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Background and objective: Patients suspected to have lung cancer, undergo endobronchial ultrasound bronchoscopy (EBUS) for the purpose of diagnosis and staging. For presumptive curable patients, the EBUS bronchoscopy is planned based on images and data from computed tomography (CT) images and positron emission tomography (PET). Our study aimed to evaluate the feasibility of a multimodal electromagnetic navigation platform for EBUS bronchoscopy, integrating ultrasound and segmented CT, and PET scan imaging data. Methods: The proof-of-concept study included patients with suspected lung cancer and pathological mediastinal/hilar lymph nodes identified on both CT and PET scans. Images obtained from these two modalities were segmented to delineate target lymph nodes and then incorporated into the CustusX navigation platform. The EBUS bronchoscope was equipped with a sensor, calibrated, and affixed to a 3D printed click-on device positioned at the bronchoscope's tip. Navigation accuracy was measured postoperatively using ultrasound recordings. Results: The study enrolled three patients, all presenting with suspected mediastinal lymph node metastasis (N1-3). All PET-positive lymph nodes were displayed in the navigation platform during the EBUS procedures. In total, five distinct lymph nodes were sampled, yielding malignant cells from three nodes and lymphocytes from the remaining two. The median accuracy of the navigation system was 7.7 mm. Conclusion: Our study introduces a feasible multimodal electromagnetic navigation platform that combines intraoperative ultrasound with preoperative segmented CT and PET imaging data for EBUS lymph node staging examinations. This innovative approach holds promise for enhancing the accuracy and effectiveness of EBUS procedures. [ABSTRACT FROM AUTHOR]

Objective(s): This study aimed to examine the influence of changes in CT values on PET images, specifically focusing on errors in CT-based attenuation correction and scatter coincidence correction (CTAC/SC) caused by gastrointestinal gas. Furthermore, it aimed to demonstrate the effectiveness of time-of-flight (TOF) PET in reducing CTAC/SC errors. Methods: PET images were reconstructed using multiple CT images with varying CT values. The study then compared the fluctuations in pixel values of the PET images corresponding to the different CT values utilized for CTAC/SC between non-TOF and TOF acquisitions. Results: PET pixel values fluctuated with changes in CT values. In the phantom study, TOF showed a significantly smaller change in PET pixel value of 1.00±0.27 kBq/mL compared to 3.72±1.33 kBq/mL in the non-TOF at sites with a CT change of +1000 HU. In the patient study, a linear regression analysis was performed to determine the effect of changes in CT values due to gastrointestinal gas migration on standard uptake value (SUV).The results showed that the TOF group had a lower ratio of change in SUV to change in CT values compared to the non-TOF group. These findings revealed that PET pixel values exhibited fluctuations in response to changes in CT values, and TOF-PET effectively mitigated CTAC/SC errors arising from gastrointestinal gas. Conclusions: TOF-PET has the potential to reduce the occurrence of suspicious accumulation. [ABSTRACT FROM AUTHOR]

Movement disorders are chronic neurological syndromes with both treatable and non-treatable causes. The top causes of movement disorders are Parkinson's disease and related disorders. Functional imaging investigations with Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) images play vital roles in diagnosis and differential diagnosis to guide disease management. Since there have been new advanced imaging technologies and radiopharmaceuticals development, there is a need for up-to-date consensus guidelines. Thus, the Nuclear Medicine Society of Thailand, the Neurological Society of Thailand, and the Thai Medical Physicist Society collaborated to establish the guideline for Nuclear Medicine investigations in movement disorder for practical use in patient care. We have extensively reviewed the current practice guidelines from other related societies and good quality papers as well as our own experience in Nuclear Medicine practice in movement disorders. We also adjust for the most suitability for application in Thailand and other developing countries. [ABSTRACT FROM AUTHOR]

Use of prostate-specific membrane antigen positron emission tomography to determine disease extent provides a novel method for risk stratification for patients with nonmetastatic castration-resistant prostate cancer and may contribute to future risk-adapted treatment algorithms. Previously, we demonstrated that prostate-specific membrane antigen positron emission tomography (PSMA-PET) revealed distant metastases in 109/200 patients (39% distant nodes, 24% bone, and 6% visceral organ) with nonmetastatic castration-resistant prostate cancer (nmCRPC) and high-risk features (International Society of Urological Pathology score ≥4 and/or prostate-specific antigen doubling time ≤10 mo) without metastases by conventional imaging. However, the impact of disease extent determined by PSMA-PET on patient outcomes is unknown. We followed these 200 patients for a median of 43 mo after PSMA-PET and retrospectively assessed the association between patient characteristics, PSMA-PET findings, treatment management, and outcomes using a Kaplan-Meier model and Cox multivariable regressions. Among assessed disease characteristics, polymetastatic disease (five or more distant lesions on PET) was independently associated with shorter overall survival (OS; median 61 mo vs not reached; hazard ratio [95% confidence interval], 1.81 [1.00–3.27]; p = 0.050) and time to new metastases (median 38 vs 60 mo; 1.80 [1.10–2.96]; p = 0.019), and initial pN1 status with shorter OS (55 mo vs not reached; 1.94 [1.12–3.37]; p = 0.019). Following PSMA-PET, locoregional salvage therapies were used most commonly in no/local disease (58%), and androgen receptor signaling inhibitors were used in distant metastatic disease (51%). PSMA-PET provides additional risk stratification for patients with nmCRPC. Polymetastatic disease (five or more distant lesions) is associated with worse outcomes. A novel sensitive imaging technology, called prostate-specific membrane antigen positron emission tomography (PSMA-PET), allows doctors to detect the spread of prostate cancer, known as distant metastases, earlier and more accurately than in the past. In our study, PSMA-PET detected none to many metastases in patients who were considered free of distant metastasis by conventional imaging. These findings predicted outcomes and were used to select appropriate treatment. [ABSTRACT FROM AUTHOR]

Background: PET/CT is currently the gold standard for lung cancer staging, and it is also used to identify distant and nodal metastases. High-resolution MRI can also be used to diagnose and provide morphological details about lung cancer. Standardized uptake value 'SUV' calculated from PET/CT gives information about tumor behavior where the SUV reflects metabolic tumor activity. Apparent diffusion coefficient 'ADC' calculated from DW-MRI is a quantitative imaging marker aiming to assess tumor cellularity which reflects tumor behavior. The study aimed to correlate ADC assessed by DW-MRI and metabolic activity determined by SUV max in PET/CT in local and nodal staging of newly diagnosed NSCLC. Results: Our study involved twenty-one patients who were pathologically proven to be NSCLC, 19 males (90.5%) and 2 females (9.5%), with a median age of 61 years (ranging from 37 to 84 years). Among all NSCLC primary mass lesions, we observed a statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR (r = − 0.509 and p = 0.019, r = − 0.472 and p = 0.031 and r = − 0.434 and p = 0.049 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Additionally, we observed another statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR in NSCLC mediastinal lymph nodes (r = − 0.699 and p = 0.011, r = − 0.58 and p = 0.048 and r = − 0.629 and p = 0.028 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Conclusions: ADC values calculated from DW-MRI might act as a new prognostic tool owing to its significant inverse correlation with SUV max achieved from PET/CT in NSCLC primary mass lesions as well as mediastinal lymph nodes. [ABSTRACT FROM AUTHOR]

Background: This study addresses the technical gap between clinical radiation therapy (RT) and preclinical small‐animal RT, hindering the comprehensive validation of innovative clinical RT approaches in small‐animal models of cancer and the translation of preclinical RT studies into clinical practices. Purpose: The main aim was to explore the feasibility of biologically guided RT implemented within a small‐animal radiation therapy (SART) platform, with integrated quad‐modal on‐board positron emission tomography (PET), single‐photon emission computed tomography, photon‐counting spectral CT, and cone‐beam CT (CBCT) imaging, in a Monte Carlo model as a proof‐of‐concept. Methods: We developed a SART workflow employing quad‐modal imaging guidance, integrating multimodal image‐guided RT and emission‐guided RT (EGRT). The EGRT algorithm was outlined using positron signals from a PET radiotracer, enabling near real‐time adjustments to radiation treatment beams for precise targeting in the presence of a 2‐mm setup error. Molecular image‐guided RT, incorporating a dose escalation/de‐escalation scheme, was demonstrated using a simulated phantom with a dose painting plan. The plan involved delivering a low dose to the CBCT‐delineated planning target volume (PTV) and a high dose boosted to the highly active biological target volume (hBTV) identified by the 18F‐PET image. Additionally, the Bayesian eigentissue decomposition method illustrated the quantitative decomposition of radiotherapy‐related parameters, specifically iodine uptake fraction and virtual noncontrast (VNC) electron density, using a simulated phantom with Kidney1 and Liver2 inserts mixed with an iodine contrast agent at electron fractions of 0.01–0.02. Results: EGRT simulations generated over 4,000 beamlet responses in dose slice deliveries and illustrated superior dose coverage and distribution with significantly lower doses delivered to normal tissues, even with a 2‐mm setup error introduced, demonstrating the robustness of the novel EGRT scheme compared to conventional image‐guided RT. In the dose‐painting plan, doubling the dose to the hBTV while maintaining a low dose for the PTV resulted in an organ‐at‐risk (OAR) dose comparable to the low‐dose treatment for the PTV alone. Furthermore, the decomposition of radiotherapy‐related parameters in Kidney1 and Liver2 inserts, including iodine uptake fractions and VNC electron densities, exhibited average relative errors of less than 1.0% and 2.5%, respectively. Conclusions: The results demonstrated the successful implementation of biologically guided RT within the proposed quad‐model image‐guided SART platform, with potential applications in preclinical RT and adaptive RT studies. [ABSTRACT FROM AUTHOR]

Introduction: A newly developed clinical organ-targeted Positron Emission Tomography (PET) system (also known as Radialis PET) is tested with a set of standardized and custom tests previously used to evaluate the performance of Positron Emission Mammography (PEM) systems. Methods: Imaging characteristics impacting standardized uptake value (SUV) and detectability of small lesions, namely spatial resolution, linearity, uniformity, and recovery coefficients, are evaluated. Results: In-plane spatial resolution was measured as 2.3 mm ± 0.1 mm, spatial accuracy was 0.1 mm, and uniformity measured with flood field and NEMA NU-4 phantom was 11.7% and 8.3% respectively. Selected clinical images are provided as reference to the imaging capabilities under different clinical conditions such as reduced activity of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG) and time-delayed acquisitions. SUV measurements were performed for selected clinical acquisitions to demonstrate a capability for quantitative image assessment of different types of cancer including for invasive lobular carcinoma with comparatively low metabolic activity. Quantitative imaging performance assessment with phantoms demonstrates improved contrast recovery and spill-over ratio for this PET technology when compared to other commercial organ-dedicated PET systems with similar spatial resolution. Recovery coefficients were measured to be 0.21 for the 1 mm hot rod and up to 0.89 for the 5 mm hot rod of NEMA NU-4 Image Quality phantom. Discussion: Demonstrated ability to accurately reconstruct activity in tumors as small as 5 mm suggests that the Radialis PET technology may be well suited for emerging clinical applications such as image guided assessment of response to neoadjuvant systemic treatment (NST) in lesions smaller than 2 cm. Also, our results suggest that, while spatial resolution greatly influences the partial volume effect which degrades contrast recovery, optimized count rate performance and image reconstruction workflow may improve recovery coefficients for systems with comparable spatial resolution. We emphasize that recovery coefficient should be considered as a primary performance metric when a PET system is used for accurate lesion size or radiotracer uptake assessments. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET)-guided radiation therapy is a novel tracked dose delivery modality that uses real-time PET to guide radiation therapy beamlets. The BIOGUIDE-X study was performed with sequential cohorts of participants to (1) identify the fluorodeoxyglucose (FDG) dose for PET-guided therapy and (2) confirm that the emulated dose distribution was consistent with a physician-approved radiation therapy plan. This prospective study included participants with at least 1 FDG-avid targetable primary or metastatic tumor (2-5 cm) in the lung or bone. For cohort I, a modified 3 + 3 design was used to determine the FDG dose that would result in adequate signal for PET-guided therapy. For cohort II, PET imaging data were collected on the X1 system before the first and last fractions among patients undergoing conventional stereotactic body radiation therapy. PET-guided therapy dose distributions were modeled on the patient's computed tomography anatomy using the collected PET data at each fraction as input to an "emulated delivery" and compared with the physician-approved plan. Cohort I demonstrated adequate FDG activity in 6 of 6 evaluable participants (100.0%) with the first injected dose level of 15 mCi FDG. In cohort II, 4 patients with lung tumors and 5 with bone tumors were enrolled, and evaluable emulated delivery data points were collected for 17 treatment fractions. Sixteen of the 17 emulated deliveries resulted in dose distributions that were accurate with respect to the approved PET-guided therapy plan. The 17th data point was just below the 95% threshold for accuracy (dose-volume histogram score = 94.6%). All emulated fluences were physically deliverable. No toxicities were attributed to multiple FDG administrations. PET-guided therapy is a novel radiation therapy modality in which a radiolabeled tumor can act as its own fiducial for radiation therapy targeting. Emulated therapy dose distributions calculated from continuously acquired real-time PET data were accurate and machine-deliverable in tumors that were 2 to 5 cm in size with adequate FDG signal characteristics. [ABSTRACT FROM AUTHOR]

The synaptic hypothesis is an influential theory of the pathoetiology of schizophrenia (SCZ), which is supported by the finding that there is lower uptake of the synaptic terminal density marker [11C]UCB-J in patients with chronic SCZ than in control participants. However, it is unclear whether these differences are present early in the illness. To address this, we investigated [11C]UCB-J volume of distribution (V T) in antipsychotic-naïve/free patients with SCZ who were recruited from first-episode services compared with healthy volunteers. Forty-two volunteers (SCZ n = 21, healthy volunteers n = 21) underwent [11C]UCB-J positron emission tomography to index [11C]UCB-J V T and distribution volume ratio in the anterior cingulate, frontal, and dorsolateral prefrontal cortices; the temporal, parietal and occipital lobes; and the hippocampus, thalamus, and amygdala. Symptom severity was assessed in the SCZ group using the Positive and Negative Syndrome Scale. We found no significant effects of group on [11C]UCB-J V T or distribution volume ratio in most regions of interest (effect sizes from d = 0.0–0.7, p >.05), with two exceptions: we found lower distribution volume ratio in the temporal lobe (d = 0.7, uncorrected p <.05) and lower V T / f p in the anterior cingulate cortex in patients (d = 0.7, uncorrected p <.05). The Positive and Negative Syndrome Scale total score was negatively associated with [11C]UCB-J V T in the hippocampus in the SCZ group (r = −0.48, p =.03). These findings indicate that large differences in synaptic terminal density are not present early in SCZ, although there may be more subtle effects. When taken together with previous evidence of lower [11C]UCB-J V T in patients with chronic illness, this may indicate synaptic density changes during the course of SCZ. [ABSTRACT FROM AUTHOR]

Background: Positron Emission Tomography-Magnetic Resonance (PET-MR) scanners could improve ano-rectal radiotherapy planning through improved Gross Tumour Volume (GTV) delineation and enabling dose painting strategies using metabolic measurements. This requires accurate quantitative PET images acquired in the radiotherapy treatment position. Purpose: This study aimed to evaluate the impact on GTV delineation and metabolic parameter measurement of using novel Attenuation Correction (AC) maps that included the radiotherapy flat couch, coil bridge and anterior coil to see if they were necessary. Methods: Seventeen ano-rectal radiotherapy patients received a 18FFluoroDeoxyGlucose PET-MR scan in the radiotherapy position. PET images were reconstructed without (CTACstd) and with (CTACcba) the radiotherapy hardware included. Both AC maps used the same Computed Tomography image for patient AC. Semi-manual and threshold GTVs were delineated on both PET images, the volumes compared and the Dice coefficient calculated. Metabolic parameters:Standardized Uptake Values SUVmax,SUVmean and Total Lesion Glycolysis (TLG) were compared using paired t-tests with a Bonferroni corrected significance level of p = 0.05/8 = 0.006. Results: Differences in semi-manual GTV volumes between CTACcba and CTACstd were approaching statistical significance (difference -15.9%±1.6%, p = 0.007), with larger differences in low FDG-avid tumours (SUVmean < 8.5 gmL-1). The CTACcba and CTACstd GTVs were concordant with Dice coef- ficients 0.89 ± 0.01 (manual) and 0.98 ± 0.00 (threshold).Metabolic parameters were significantly different, with SUVmax, SUVmean and TLG differences of -11.5% ±0.3% (p < 0.001), -11.6%±0.3% (p < 0.001) and -13.7% ±0.6% (p = 0.003) respectively. The TLG difference resulted in 1/8 rectal cancer patients changing prognosis group,based on literature TLG cut-offs,when using CTACcba rather than CTACstd. Conclusions: This study suggests that using AC maps with the radiotherapy hardware included is feasible for patient imaging. The impact on tumour delineation was mixed and needs to be evaluated in larger cohorts. However using AC of the radiotherapy hardware is important for situations where accurate metabolic measurements are required, such as dose painting and treatment prognostication. [ABSTRACT FROM AUTHOR]

Objective: The diagnosis of neurosarcoidosis (NS) remains challenging due to the difficulty to obtain central nervous system (CNS) biopsies. Various diagnostic parameters are considered for the definition of possible, probable and definite NS. Magnetic resonance imaging (MRI) is the imaging gold standard and considered in diagnostic criteria. Fluorodeoxyglucose positron emission (18F-FDG PET) is sometimes performed additionally to identify possible systemic biopsy targets. However, at present, its findings are not incorporated into the diagnostic criteria for neurosarcoidosis (NS). Methods: We conducted a single center retrospective search for the period 2020–2022, for patients with neurological symptoms in a diagnostic context of suspected NS who underwent MRI and additional 18F-FDG PET scans to identify potential hypermetabolism in the CNS and biopsy targets. Results: We identified three cases of NS, where Gadolinium-enhanced MRI scans did not show abnormalities while 18F-FDG PET revealed hypermetabolic lesions in areas of the CNS. Additional MRI scans were still inconclusive for structural changes. We diagnosed a "probable" NS in all cases with histopathological confirmation of systemic sarcoidosis which led to an intensified therapy regime. Discussion: 18F-FDG PET is an early indicator for metabolic changes. It appears to be a useful add-on to improve accuracy of diagnostic criteria in suspected NS without MRI findings. [ABSTRACT FROM AUTHOR]

Because of their many advantages, such as simplicity of handling, affordability, and environmental friendliness, green magnetic nanoparticles (GMNPs) are currently receiving more attention than prevailing magnetic nanoparticles (MNPs). The synthesis and application of GMNPs inspired by biological systems are encouraged by rising ecological consciousness and stringent environmental restrictions and also deal with in detail in this manuscript. The current report presents the biological and environmental uses of GMNPs in-depth. Numerous biomedical applications, including imaging and diagnosis, cancer therapy, immunoassay, genetic engineering, and supported enzymes (proteins and peptides), among others, successfully use GMNPs. The GMNPs would be coupled with tiny sensors, microsystems, and microfluidics modules to boost the signal sensitivity for the identification of environmental contaminants, diseases, poisons, drugs, and trace biomarkers from clinical, environmental, and dietary examples. The GMNPs were essential elements in gene delivery and gene therapy initiatives, among other genetic engineering endeavors. They have also been extensively used for environmental applications such as wastewater treatment, organic pollutants decontamination, electrochemical sensing, industrial and radioactive wastes treatment, pollutant adsorption and removal etc. The use of GMNPs, particularly biosynthesized MNPs, is also believed to be more cost-effective than the majority of regularly used traditional MNPs. In addition, Green magnetic nanoparticles applied as supported enzymes, proteins and peptides catalyst, positron emission tomography, computed tomography, magnetic resonance imaging, theranostics, thermo-chemotherapy, electrochemical immunoassay and efficient detection of coronavirus is a significant issue in modern analytical chemistry and other fields. The opportunities of using GMNPs in the place of traditional MNPs have also been proposed. [ABSTRACT FROM AUTHOR]

A 58-year-old man presenting with dyspnea, weight loss, and night sweating underwent 18F-fluorodeoxyglucose positron emission tomography/ computed tomography (18F-FDG PET/CT) because of a suspicion of malignancy. 18F-FDG PET/CT demonstrated mild to moderate uptake on nasal, cricoid, and tracheobronchial tree cartilages and costovertebral junctions. The diagnosis was relapsing polychondritis, which is a rare multisystem disease characterized by inflammation of cartilage. In addition, subsequent 18F-FDG PET/CT after treatment showed complete metabolic response. [ABSTRACT FROM AUTHOR]

Multiple myeloma (MM) is a heterogeneous neoplasm accounting for the second most prevalent hematologic disorder. The identification of noninvasive, valuable biomarkers is of utmost importance for the best patient treatment selection, especially in heterogeneous diseases like MM. Despite molecular imaging with positron emission tomography (PET) has achieved a primary role in the characterization of MM, it is not free from shortcomings. In recent years, radiomics and artificial intelligence (AI), which includes machine learning (ML) and deep learning (DL) algorithms, have played an important role in mining additional information from medical images beyond human eyes' resolving power. Our review provides a summary of the current status of radiomics and AI in different clinical contexts of MM. A systematic search of PubMed, Web of Science, and Scopus was conducted, including all the articles published in English that explored radiomics and AI analyses of PET/CT images in MM. The initial results have highlighted the potential role of such new features in order to improve the clinical stratification of MM patients, as well as to increase their clinical benefits. However, more studies are warranted before these approaches can be implemented in clinical routines. [ABSTRACT FROM AUTHOR]

Background: Over the past five years, ultrafast high-frequency (HF) readout concepts have advanced the timing performance of silicon photomultipliers (SiPMs). The shown impact in time-of-flight (TOF) techniques can further push the limits in light detection and ranging (LiDAR), time-of-flight positron-emission tomography (TOF-PET), time-of-flight computed tomography (TOF-CT) or high-energy physics (HEP). However, upscaling these electronics to a system-applicable, multi-channel readout, has remained a challenging task, posed by the use of discrete components and a high power consumption. To this day, there are no means to exploit the high TOF resolution of these electronics on system scale or to measure the actual timing performance limits of a full detector block. Methods: In this work, we present a 16-channel HF readout board, including leading-edge discrimination and a linearized time-over-threshold (TOT) method, which is fully compatible with a high-precision time-to-digital converters (TDCs), such as the picoTDC developed at CERN. The discrete implementation allows ideal adaptation of this readout to a broad range of detection tasks. As a first step, the functionality of the circuit has been tested using the TOFPET2 ASIC as back-end electronics to emulate the TDC, also in view of its properties as a highly scalable data acquisition solution. Results: The produced board is able to mitigate influences of baseline shifts in the TOFPET2 front end, which has been shown in experiments with a pulsed laser, increasing the achievable intrinsic coincidence timing resolution (CTR) of the TOFPET2 readout electronics from 70 ps (FWHM) to 62 ps (FWHM). Single-channel coincidence experiments including a γ -source, 2 × 2 × 3 mm 3 LYSO:Ce,Ca crystals and Broadcom NUV-MT SiPMs resulted in a CTR of 118 ps (FWHM). For a 4 × 4 matrix of 3.88 × 3.88 × 19 mm 3 LYSO:Ce,Ca crystals one-to-one coupled to a 4 × 4 array of Broadcom NUV-MT SiPMs, an average CTR of 223 ps (FWHM) was obtained. Conclusion: The implemented 16-channel HF electronics are fully functionall and have a negligible influence on the timing performance of the back-end electronics used, here the TOFPET2 ASIC. The ongoing integration of the picoTDC with the 16-channel HF board is expected to further set the path toward sub-100 ps TOF-PET and sub-30ps TOF resolution for single-photon detection. [ABSTRACT FROM AUTHOR]

Prevalent PET imaging reconstructs 2γ-photon pairs emitted after an annihilation from para-positronium (p-Ps) and rejects 3γ events from ortho-positronium (o-Ps) as noises. The 3γ/2γ decay ratio is ~ 3/7 in human body theoretically but in fact significantly lower due to pick-off process, hence PET imaging quality is well controlled. In a PET-MR hybrid unit, the MR magnetic field alters positronium decay patterns through magnetic quenching: all o-Ps and excited p-Ps states are split into finer quantum states under strong magnetic field, thus transitions between some triplet and singlet finer states (mz = 0) were no longer forbidden, thus some o-Ps converts to p-Ps spontaneously by emitting hyperfine split (HFS) photons, which also drops 3γ/2γ ratio hence helps PET imaging quality. However, inverse magnetic quenching might also occur if any external source of HFS frequencies is nearby, thus many p-Ps convert to o-Ps by absorbing those HFS photons (induced HFS transitions). This will dramatically increase 3γ/2γ ratio and hence degrade PET imaging quality instantaneously. The HFS spectrum lies in a broad range of microwaves, from 0.02 to 200 GHz. To prevent inverse magnetic quenching, it is necessary to block external microwave sources outside the hybrid vault, by adding a thin metal layer at all directions of the vault. This could be achieved by adopting the metallic Faraday Cage, which was originally for MR shielding, with possible amendment if necessary. The frequencies of excitation pulses in MR imaging overlap with HFS spectrum, however, the chance for mutual interference during hybrid imaging is small, hence there seems no need to veto each other during hybrid scans. [ABSTRACT FROM AUTHOR]

Objective. Head and neck (H&N) cancers are prevalent globally, and early and accurate detection is absolutely crucial for timely and effective treatment. However, the segmentation of H&N tumors is challenging due to the similar density of the tumors and surrounding tissues in CT images. While positron emission computed tomography (PET) images provide information about the metabolic activity of the tissue and can distinguish between lesion regions and normal tissue. But they are limited by their low spatial resolution. To fully leverage the complementary information from PET and CT images, we propose a novel and innovative multi-modal tumor segmentation method specifically designed for H&N tumor segmentation. Approach. The proposed novel and innovative multi-modal tumor segmentation network (LSAM) consists of two key learning modules, namely L2-Norm self-attention and latent space feature interaction, which exploit the high sensitivity of PET images and the anatomical information of CT images. These two advanced modules contribute to a powerful 3D segmentation network based on a U-shaped structure. The well-designed segmentation method can integrate complementary features from different modalities at multiple scales, thereby improving the feature interaction between modalities. Main results. We evaluated the proposed method on the public HECKTOR PET-CT dataset, and the experimental results demonstrate that the proposed method convincingly outperforms existing H&N tumor segmentation methods in terms of key evaluation metrics, including DSC (0.8457), Jaccard (0.7756), RVD (0.0938), and HD95 (11.75). Significance. The innovative Self-Attention mechanism based on L2-Norm offers scalability and is effective in reducing the impact of outliers on the performance of the model. And the novel method for multi-scale feature interaction based on Latent Space utilizes the learning process in the encoder phase to achieve the best complementary effects among different modalities. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET) myocardial perfusion imaging (MPI) quantifies left ventricular ejection fraction (LVEF) at peak stress. PET LVEF reserve (LVEF-R = stress LVEF − rest LVEF) offers diagnostic and prognostic value. The purpose of this study was to determine if PET LVEF-R identifies patients with survival benefit postrevascularization. We followed 14,649 unique consecutive patients undergoing 82Rb rest/stress PET MPI from January 2010 to January 2016 (excluding known cardiomyopathy). Adjusted Cox models were built to predict all-cause death, and the 3-way interaction of known coronary artery disease (CAD) (prior myocardial infarction/revascularization), LVEF-R, and 90-day revascularization was tested. Known CAD was present in 4,982 (34.0%). Ischemia was detected in 5,396 (36.8%; ≥10% in 1,909 [13%]). Mean LVEF-R was 4.2% ± 5.7%, and was ≤0, 1 to 5, and >5 in 3,349 (22.9%), 5,266 (35.9%), and 6,034 (41.2%). Over median follow-up of 3.4 years (IQR: 1.9-5.2 years), 1,324 (8.1%) had 90-day revascularization, and there were 2,192 (15.0%) deaths. In multivariable modeling, there was a significant 3-way interaction among known CAD, LVEF-R, and 90-day revascularization (P = 0.025), such that LVEF-R ≤0 identified patients with survival benefit with 90-day revascularization in those without prior CAD (interaction P = 0.005), independently beyond percent ischemia and myocardial flow reserve. Among patients with known CAD, LVEF-R was not prognostic of death (HR: 0.99; 95% CI: 0.98-1.02; P = 0.98). A lack of augmentation or drop in LVEF with vasodilator stress on PET MPI independently identifies patients who have better survival with revascularization within 90 days post-MPI compared with medical therapy, in absence of prior myocardial infarction or revascularization. Multiparametric assessment of ischemia with PET can optimize post-test management. [Display omitted] [ABSTRACT FROM AUTHOR]

Most treatment planning systems of boron neutron capture therapy perform dose calculations based on the assumption of a homogeneous boron distribution in tumors, which leads to dose distortion due to the difference between the tumor-to-normal tissue ratio (TNR) range measured in positron emission tomography images (PET) and the target delineation in computed tomography images of the treatment plan. The heterogeneous boron distribution in the target of the treatment plan can be obtained by image fusion. This study provides a way to quantify a heterogeneous boron distribution based on PET images. Theoretically, the same mean TNR for dose calculation by homogeneous or heterogeneous boron distribution should get almost the same mean dose. However, slightly different mean doses are found due to the partial volume effect for a small target volume. The wider the boron distribution is, the higher the impact on the dose-volume histogram distribution is. Dose distribution with homogeneous boron distribution may be overestimated in low boron uptake regions by wrong boron concentration and neutron flux depression. To accurately give the tumor prescription dose and achieve better tumor control, for low dose regions of the tumor should be considered more boron neutron capture therapy treatments or combined with other treatment modalities. The heterogeneous boron distribution must be taken into consideration to have an accurate dose estimation. Therefore, the way how medical physicists and clinicians process the TNR in gross tumor volume should be refined, and the method demonstrated in the work provides a good reference. [ABSTRACT FROM AUTHOR]

Time-of-flight (TOF) positron emission tomography (PET) detectors improve the signal-to-noise ratio of PET images by limiting the position of the generation of two 511 keV gamma-rays in space using the arrival time difference between the two photons. Unfortunately, bismuth germanate (BGO), widely used in conventional PET detectors, was limited as a TOF PET scintillator due to the relatively slow decay time of the scintillation photons. However, prompt Cerenkov light in BGO has been identified in addition to scintillation photons. Using Cerenkov photons for timing has significantly improved the coincidence timing resolution (CTR) of BGO. Based on this, further research on improving the CTR for a BGO-based TOF PET system is being actively conducted. Wrapping materials for BGO pixels have primarily employed white reflectors to most efficiently collect scintillation light. White reflectors have customarily been used as reflectors for BGO pixels even after Cerenkov light began to be utilized for timing calculations in pixel-level experiments. However, when the arrival-time differences of the two 511 keV annihilations photons were measured with pure Cerenkov radiators, painting the lateral sides of the radiators black can improve CTR by suppressing the reflection of Cerenkov photons. The use of BGO for TOF PET detectors requires simultaneously minimizing scintillation loss for good energy information and suppressing reflected Cerenkov photons for better timing performance. Thus, reflectors for BGO pixels should be optimized for better timing and energy performance. In this study, colored polytetrafluoroethylene (PTFE) tapes with discontinuous reflectance values at specific wavelengths were applied as a BGO reflector. We hypothesized that CTR could be enhanced by selectively suppressing reflected Cerenkov photons with an optimum colored reflector on the BGO pixel while minimizing scintillation photon loss. CTRs were investigated utilizing white and three colors (yellow, red, and green) PTFE tapes as a reflector. In addition, black-painted PTFE tape and enhanced specular reflector film were investigated as reference reflector materials. When 3 × 3 × 20 mm3 BGO pixels were wrapped with the yellow PTFE reflector, the CTR was significantly improved to 365 ± 5 ps from 403 ± 14 ps measured with the conventional white PTFE reflector. Adequate energy information was still obtained with only 4.1% degradation in light collection compared to the white reflector. Colored reflectors show the possibility to further improve CTR for BGO pixels with optimum reflectance design. [ABSTRACT FROM AUTHOR]

Early diagnosis of Alzheimer's disease (AD) plays a key role in preventing and responding to this neurodegenerative disease. It has shown that, compared with a single imaging modality‐based classification of AD, synergy exploration among multimodal neuroimages is beneficial for the pathological identification. However, effectively exploiting multimodal information is still a big challenge due to the lack of efficient fusion methods. Herein, a multimodal fusion network based on attention mechanism is proposed, in which magnetic resonance imaging (MRI) and positron emission computed tomography (PET) images are converted into feature vectors with the same dimension, while the demographic information and clinical data are preprocessed and converted into feature vectors through embedding. This attention model can focus on important feature points, fuse the multimodal information more effectively, and thus provide accurate diagnosis and prediction for different pathological stages. The results show that the model achieves an accuracy of 84.1% for triple classification tasks in normal cognition (NC) versus mild cognitive impairment (MCI) versus AD and 93.9% prediction accuracy in stable MCI (sMCI) versus progressive MCI (pMCI). In contrast to the existing multimodal diagnosis methods, our model yields a state‐of‐the‐art accuracy of AD diagnosis, which is powerful and promising in clinical practice. [ABSTRACT FROM AUTHOR]

The serotonin system plays a critical role in the modulation of impulsive aggression. Although serotonin transporters (SERT) are key in modulating synaptic serotonin levels, few studies have investigated the role of SERT levels in human impulsive aggression. The aim of this study was to investigate whether brain SERT levels are associated with trait impulsive aggression. We included 148 healthy individuals (mean age 29.3 ± 13.0, range 18–80 years, 91 females) who had undergone positron emission positron (PET) examinations with the SERT tracer [11C]DASB and filled in self-report questionnaires of trait aggression, trait impulsivity and state aggression. We evaluated the association between cerebral SERT binding (BP ND) and trait impulsive aggression in a latent variable model, with one latent variable (LV SERT) modelled from SERT BP ND in frontostriatal and frontolimbic networks implicated in impulsive aggression, and another latent variable (LV IA) modelled from various trait measures of impulsivity and aggression. The LV SERT was not significantly associated with the LV IA (p = 0.8). Post-hoc univariate analyses did not reveal any significant associations between regional SERT levels and trait aggression, trait impulsivity or state aggression, but we found that state aggression at the day of PET scan was significantly lower in L A /L A homozygotes vs S-carriers of the 5-HTTLPR gene (p = 0.008). We conclude that brain SERT binding was not related to variations in trait impulsive aggression or state aggression. Our findings do not support that SERT is involved in mediating the serotonergic effects on aggression and impulsivity, at least not in individuals with non-pathological levels of impulsive aggression. [ABSTRACT FROM AUTHOR]

Objectives: Given emerging data suggesting that uncertainty in the relative biologic effectiveness at the distal end of the Bragg peak results in increased mucosal injury in patients with oropharynx cancer receiving adjuvant proton therapy, we evaluated the results of post-treatment positron emission tomography--computed tomography (PET/CT) in patients with p16-positive oropharynx cancer (p16+OPC) treated with definitive intensitymodulated proton therapy (IMPT). Material and Methods: A retrospective cohort study of patients with p16+OPC treated with definitive IMPT between 2016 and 2022 was performed at a single institution. Patients with PET/CT scans within 6 months following completion of IMPT were included in the study. Positive post-treatment scans were defined by a maximum standard uptake values (SUVmax) >4.0 or a <65% reduction in SUVmax in either the primary tumor or lymph node. The Fisher's exact test was used to evaluate factors associated with positive post-treatment PET/ CT values. Results: Sixty-two patients were included for analysis. Median follow-up was 21 months (range: 3--71 months) with a median time to post-treatment PET/CT of 3 months (range: 2--6 months). Median post-treatment SUVmax of the primary disease and nodal disease was 0 (mean: 0.8, range: 0--7.7) and 0 (mean: 0.7, range: 0--9.5), respectively. Median post-treatment percent reduction in SUVmax for the primary site and lymph node was 100% (mean: 94%, range: 31.3--100%) and 100% (mean: 89%, range: 23--100%), respectively. Eleven patients had a positive posttreatment PET/CT with one biopsy-proven recurrence. Negative and positive predictive values (NPV and PPV) were 98% and 9.1%, respectively. There were no factors associated with positive post-treatment PET/CT. Conclusion: Similar to patients treated with photon-based radiation therapy, post-treatment PET/CT has a high NPV for patients with p16+OPC treated with definitive proton therapy and should be used to guide patient management. Additional patients and more events are needed to confirm the PPV of a post-treatment PET/CT in this favorable patient cohort. [ABSTRACT FROM AUTHOR]

Background: Positron Emission Mammography (PEM) is a nuclear medicine imaging tool, playing a significant role in the diagnosis of patients with breast cancer. These days, many research has been done in order to improve the performance of this system. Objective: This study aims to propose a new method for optimizing the size of axial Field of View (FOV) in PEMs and improving the performance of the systems. Material and Methods: In this analytical study, a conventional Inveon PET is simulated using GATE in order to validate the simulation. For this simulation, the mean relative difference is 2.91%, showing the precision and correction of simulation and consequently it is benchmarked. In the next step, for design of the new optimized detector, several validated simulations are performed in order to find the best geometry. Results: The best result is obtained with the axial FOV of 101.7 mm. It has 1.6×1.6×15 mm3 lutetium yttrium orthosilicate (LYSO) crystals. The detector consists of 6 block rings with 30 detector blocks in each ring. In this paper, the performance of the scanner is improved and the geometry is optimized. Sensitivity and scatter fraction of the designed scanner are 4.65% and 21.2%, respectively, also noise equivalent count rate (NECR) is 105.442 kcps. Conclusion: The results showed 1 up to 3% improvement in the sensitivity of this new detector compared with different PEMs. [ABSTRACT FROM AUTHOR]

Medical image enhancement is a topic of great interest to researchers due to the rapid evolution of technology and advancements in communication. There are many types of medical images such as X-ray images, computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, ultrasound images, positron emission tomography (PET) scans, single photon emission computed tomography (SPECT) scans, digital radiography images, mammography images and Fluoroscopy images. X-ray imaging is a valuable tool for diagnosis, monitoring, and treatment of many medical conditions, and its non-invasive, widely available, low cost and fast nature makes it a popular choice for many medical professionals. The proposed approach presents an algorithm for enhancing X-ray images, improving their visual appearance and making their content more useful and meaningful. The results of the algorithm show that enhanced images have a more natural look and provide accurate details of the objects in the X-ray images. Overall, this algorithm can aid in the diagnostic process by providing clearer and more detailed images for medical professionals to interpret. [ABSTRACT FROM AUTHOR]

Objective: The aim of this retrospective study is to evaluate the difference of 18-fluorine fluoro-2-deoxy-d-glucose positron emission tomography/ computed tomography images between the symptomatic and asymptomatic tuberculosis cases. Methods: Patients diagnosed with tuberculosis underwent 18-fluorine fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography imaging. Cases were categorized according to symptom status, types/number of symptoms, types/localization of lung lesions, and extrapulmonary involvement sides. Every lesion with pathologic features on computed tomography and/or increased 18-fluorine fluoro-2-deoxy-d-glucose uptake was measured semiquantitatively using the maximum standardized uptake value. Results: One hundred fourteen patients (n = 40 female, n = 74 male; median age 57) were enrolled in this study. Although lung parenchyma involvement was observed significantly at a higher rate in males than females, pleural and lymph node involvement was revealed at significantly higher rates in females. No significant difference was found between the symptom-positive and -negative groups in terms of gender, localization/types of lung lesion, and extrapulmonary involvement sides detected with positron emission tomography/computed tomography. Based on the criteria of maximum standardized uptake value greater than 2.0 to define active lesions, 9.5% of symptomatic cases had inactive lesions, while 80% of asymptomatic cases had active lesions. There was no statistically significant difference between the maximum standardized uptake value values of the types of lung lesions. While a positive low correlation was detected between maximum standardized uptake value of lung parenchymal lesions and the number of symptoms, a negative moderate correlation was found between the maximum standardized uptake value values of the pleura and the age. Conclusion: Interestingly, there was no significant difference between symptomatic and asymptomatic tuberculosis cases in terms of types of lung lesions and extrapulmonary involvement sides. The majority of the asymptomatic cases had active disease. Based on the findings, we think that 18-fluorine fluoro-2-deoxy-d-glucose, positron emission tomography/computed tomography is a valuable imaging modality even in asymptomatic cases with a low probability of clinically active tuberculosis. [ABSTRACT FROM AUTHOR]

This article discusses a study on the relationship between the medial thalamus and photophobia-associated migraine. The researchers found that patients with migraine, particularly those with constant photophobia, had increased activity in the thalamus compared to healthy participants. They also found a positive correlation between thalamic activity and the degree of photophobia in daily life. These findings suggest that the thalamus may play a role in the development of constant photophobia in patients with migraine. [Extracted from the article]

In the field of radiation instrumentation, there is a desire to reach a sub-10 ps FWHM timing resolution for applications such as time-of-flight positron emission tomography, time-of-flight positron computed tomography and time-resolved calorimetry. One of the key parts of the detection chain for these applications is a single-photon detector and, in recent years, the first single-photon avalanche diode (SPAD) with a sub-10 ps timing resolution was presented. To reach such a timing resolution, the SPAD was read out by an operational amplifier operated in open-loop as a comparator. This paper presents a comparison between comparators and inverters to determine which type of leading-edge discriminator can obtain the best single-photon timing resolution. Six different quenching circuits (QCs) implemented in TSMC 65 nm are tested with SPADs of the same architecture and in the same operation conditions. This allows us to compare experimental results between the different QCs. This paper also presents a method to measure the SPAD signal slope, the SPAD excess voltage variation and simulations to determine the added jitter of different leading-edge discriminators. For some discriminator architectures, a cascode transistor was required to increase the maximum excess voltage of the QC. This paper also presents the impact on the single-photon timing resolution of adding a cascode transistor for a comparator or an inverter-based discriminator. This paper reports a 6.3 ps FWHM SPTR for a SPAD read out by a low-threshold comparator and a 6.8 ps FWHM SPTR for an optimized 1 V inverter using a cascode transistor for a higher excess voltage. [ABSTRACT FROM AUTHOR]

Background: The Jagiellonian Positron Emission Tomograph is the 3-layer prototype of the first scanner based on plastic scintillators, consisting of 192 half-metre-long strips with readouts at both ends. Compared to crystal-based detectors, plastic scintillators are several times cheaper and could be considered as a more economical alternative to crystal scintillators in future PETs. JPET is also a first multi-photon PET prototype. For the development of multi-photon detection, with photon characterized by the continuous energy spectrum, it is important to estimate the efficiency of J-PET as a function of energy deposition. The aim of this work is to determine the registration efficiency of the J-PET tomograph as a function of energy deposition by incident photons and the intrinsic efficiency of the J-PET scanner in detecting photons of different incident energies. In this study, 3-hit events are investigated, where 2-hits are caused by 511 keV photons emitted in e + e - annihilations, while the third hit is caused by one of the scattered photons. The scattered photon is used to accurately measure the scattering angle and thus the energy deposition. Two hits by a primary and a scattered photon are sufficient to calculate the scattering angle of a photon, while the third hit ensures the precise labeling of the 511 keV photons. Results: By comparing experimental and simulated energy distribution spectra, the registration efficiency of the J-PET scanner was determined in the energy deposition range of 70–270 keV, where it varies between 20 and 100 % . In addition, the intrinsic efficiency of the J-PET was also determined as a function of the energy of the incident photons. Conclusion: A method for determining registration efficiency as a function of energy deposition and intrinsic efficiency as a function of incident photon energy of the J-PET scanner was demonstrated. This study is crucial for evaluating the performance of the scanner based on plastic scintillators and its applications as a standard and multi-photon PET systems. The method may be also used in the calibration of Compton-cameras developed for the ion−beam therapy monitoring and simultaneous multi-radionuclide imaging in nuclear medicine. [ABSTRACT FROM AUTHOR]

Incidental gastrointestinal tract (GIT) [18F]-Fluorodeoxyglucose (FDG) uptake in positron emission technology/computed tomography (PET/CT) is an unexpected and often complicated finding for clinicians. This retrospective study reviewed 8991 charts of patients who underwent PET/CT: 440 patients had incidental GIT uptake, of which 80 underwent endoscopy. Patient characteristics, imaging parameters, and endoscopic findings were studied. Of the 80 patients, 31 had cancer/pre-cancer lesions (16 carcinomas; 15 pre-malignant polyps). Compared to patients with benign/absent lesions, patients with cancer/pre-cancer lesions were significantly older (p = 0.01), underwent PET/CT for primary evaluation/staging of cancer (p = 0.03), had focal GIT uptake (p = 0.04), and had lower GIT uptake (p = 0.004). Among patients with focal uptake, an SUVmax of 9.2 had the highest sensitivity (0.76) and specificity (0.885) in detecting cancer/pre-cancerous lesions. Lower GIT uptake was most common in the sigmoid colon, and upper GIT uptake was most frequent in the stomach. In a bivariate analysis, predictors of cancer/pre-cancer were older age, PET/CT indicated for primary evaluation, focal uptake, uptake in the lower GIT, and higher SUVmax. Further endoscopic investigation is warranted for patients with incidental GIT uptake, especially in the elderly or those presenting for primary evaluation with PET/CT, with the following findings on imaging: lower GIT uptake, focal uptake, or high SUVmax. [ABSTRACT FROM AUTHOR]

Background: Dynamic positron emission tomography (dPET) is a nuclear medicine imaging technique providing functional images for organs of interest with applications in oncology, cardiology, and drug discovery. This technique requires the acquisition of the time-course arterial plasma activity concentration, called the arterial input function (AIF), which is conventionally acquired via arterial blood sampling. Purpose: The aim of this study was to (A) optimize the geometry for a novel and cost efficient non-invasive detector called NID designed to measure the AIF for dPET scans through Monte Carlo simulations and (B) develop a clinical data analysis chain to successfully separate the arterial component of a simulated AIF signal from the venous component. Methods: The NID was optimized by using an in-house Geant4-based software package. The sensitive volume of the NID consists of a band of 10 cm long and 1 mm in diameter scintillating fibers placed over a wrist phantom. The phantom was simulated as a cylinder, 10 cm long and 6.413 cm in diameter comprised of polyethylene with two holes placed through it to simulate the patient's radial artery and vein. This phantom design was chosen to match the wrist phantom used in our previous proof of concept work. Two geometries were simulated with different arrangements of scintillating fibers. The first design used a single layer of 64 fibers. The second used two layers, an inner layer with 29 fibers and an outer layer with 30 fibers. Four positron emitting radioisotopes were simulated: 18F, 11C, 15O, and 68Ga with 100 million simulated decay events per run. The total and intrinsic efficiencies of both designs were calculated as well as the full width half maximum (FWHM) of the signal. In addition, contribution by the annihilation photons versus positrons to the signal was investigated. The results obtained from the two simulated detector models were compared. A clinical data analysis chain using an expectation maximization maximum likelihood algorithm was tested. This analysis chain will be used to separate arterial counts from the total signal. Results: The second NID design with two layers of scintillating fibers had a higher efficiency for all simulations with a maximum increase of 17% total efficiency for 11C simulation. All simulations had a significant annihilation photon contribution. The signal for 18F and 11C was almost entirely due to photons. The clinical data analysis chain was within 1% of the true value for 434 out of 440 trials. Further experimental studies to validate these simulations will be required. Conclusions: The design of the NID was optimized and its efficiency increased through Monte Carlo simulations. A clinical data analysis chain was successfully developed to separate the arterial component of an AIF signal from the venous component. The simulations show that the NID can be used to accurately measure the AIF non-invasively for dPET scans. [ABSTRACT FROM AUTHOR]

Background: 44Sc/47Sc is an attractive theranostic pair for targeted in vivo positron emission tomographic (PET) imaging and beta-particle treatment of cancer. The 44Ti/44Sc generator allows daily onsite production of this diagnostic isotope, which may provide an attractive alternative for PET facilities that lack in-house irradiation capabilities. Early animal and patient studies have demonstrated the utility of 44Sc. In our current study, we built and evaluated a novel clinical-scale 44Ti/44Sc generator, explored the pharmacokinetic profiles of 44ScCl3, [44Sc]-citrate and [44Sc]-NODAGA (1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid) in naïve mice, and estimated the radiation burden of 44ScCl3 in humans. Methods: 44Ti/44Sc (101.2 MBq) in 6 M HCl solution was utilized to assemble a modular ZR resin containing generator. After assembly, 44Sc was eluted with 0.05 M HCl for further PET imaging and biodistribution studies in female Swiss Webster mice. Based on the biodistribution data, absorbed doses of 44/47ScCl3 in human adults were calculated for 18 organs and tissues using the IDAC-Dose software. Results: 44Ti in 6 M HCl was loaded onto the organic resin generator with a yield of 99.97%. After loading and initial stabilization, 44ScCl3 was eluted with 0.05 M HCl in typical yields of 82.9 ± 5.3% (N = 16), which was normalized to the estimated generator capacity. Estimated generator capacity was computed based on elution time interval and the total amount of 44Ti loaded on the generator. Run in forward and reverse directions, the 44Sc/44Ti ratio from a primary column was significantly improved from 1038 ± 440 to 3557 ± 680 (Bq/Bq) when a secondary, replaceable, ZR resin cartridge was employed at the flow outlet. In vivo imaging and ex vivo distribution studies of the reversible modular generator for 44ScCl3, [44Sc]-citrate and [44Sc]-NODAGA show that free 44Sc remained in the circulation significantly longer than the chelated 44Sc. The dose estimation of 44ScCl3 reveals that the radiation burden is 0.146 mSv/MBq for a 70 kg adult male and 0.179 mSv/MBq for a 57 kg adult female. Liver, spleen and heart wall will receive the highest absorbed dose: 0.524, 0.502, and 0.303 mGy/MBq, respectively, for the adult male. Conclusions: A clinical-scale 44Ti/44Sc generator system with a modular design was developed to supply 44ScCl3 in 0.05 M HCl, which is suitable for further radiolabeling and in vivo use. Our data demonstrated that free 44ScCl3 remained in the circulation for extended periods, which resulted in approximately 10 times greater radiation burden than stably chelated 44Sc. Stable 44Sc/47Sc-complexation will be more favorable for in vivo use and for clinical utility. [ABSTRACT FROM AUTHOR]

Purpose: Total body positron emission tomography (TB-PET) has recently been introduced in nuclear medicine departments. There is a large interest in these systems, but for many centers, the high acquisition cost makes it very difficult to justify their current operational budget. Here, we propose medium-cost long axial FOV scanners as an alternative. Methods: Several medium-cost long axial FOV designs are described with their advantages and drawbacks. We describe their potential for higher throughput, more cost-effective scanning, a larger group of indications, and novel research opportunities. The wider spread of TB-PET can also lead to the fast introduction of new tracers (at a low dose), new methodologies, and optimized workflows. Conclusions: A medium-cost TB-PET would be positioned between the current standard PET-CT and the full TB-PET systems in investment but recapitulate most advantages of full TB-PET. These systems could be more easily justified financially in a standard academic or large private nuclear medicine department and still have ample research options. [ABSTRACT FROM AUTHOR]

Background: Autologous anti‐CD19 chimeric antigen receptor (CAR) T‐cell therapy is an effective treatment for approximately 40% of relapsed/refractory large B cell lymphomas (LBCL), and early identification of patients at risk for relapse or progression after CAR T‐cell therapy represents a clinical need. Methods: The authors conducted a single‐center prospective study on 47 relapsed/refractory LBCL receiving CAR T‐cell therapy to evaluate the prognostic value of baseline and after infusion 18F‐fluorodeoxyglucose positron emission tomography (PET)‐computed tomography. Qualitative and quantitative metabolic parameters were evaluated before lymphodepletion, at day 30 and 90 post‐infusion. Results: Deep variation of standardized uptake value (SUV)mean between baseline and day 30 correlated with response at day 90 (hazard ratio [HR], 1.49; 95% confidence interval [CI], 1.01–2.2); p =.04) and better progression‐free survival (PFS) (HR, 0.63; 95% CI, 0.41–0.97); p =.04). In the overall population, 1‐year PFS was 63% for Deauville score (DS)1–3 and 39% for DS4–5 patients, respectively (p =.02), however, the prognostic role of DS was lost when survivals are analyzed by considering 38 patients not progressing at 30 days. In these patients, in partial response or stable disease, the combination of DS and variation of SUVmean allowed identification of three groups with different prognosis: patients with DS1–3 and those with DS4–5 and decreased SUVmean had similar 1‐year PFS of 62% and 61%, whereas patients with DS4–5 and increased SUVmean had a poorer 1‐year PFS of 33% (p =.04). Conclusions: PET parameters and association of DS and variation of SUVmean at 30 days could help in identify patients at high risk of CAR T‐cell failure. Lay summary: This is a single‐center prospective study on 47 lymphoma patients receiving commercial chimeric antigen receptor T‐cell therapy aimed to evaluate the prognostic value of baseline and after infusion 18F‐fluorodeoxyglucose positron emission tomography.Among patients in partial remission or stable disease at day 30, the authors observed two subgroups with significantly different prognosis; patients with Deauville score (DS)4–5 and a concomitant reduction of standardized uptake value (SUV)mean had higher probability of long‐lasting response than those with DS4–5 and an increase of SUVmean. The combination of qualitative and quantitative positron emission tomography parameters assessed at day 30 after chimeric antigen receptor T‐cell treatment could help identify prognostically different subgroups among patients with partial response or stable disease. At day 30, patients in partial remission (PR)/stable disease (SD) and a concomitant reduction of standardized uptake value (SUV)mean had higher probability of long‐lasting response than those with PR/SD and an increase of SUVmean. [ABSTRACT FROM AUTHOR]

Introduction: There is increased interest in the use of positron emission tomography (PET) in psoriatic patients. We used PET induced with tracer fluorine- 18 (18F) fluorodeoxyglucose (FDG) to study the association between the process of early-atherogenesis (eAg) and aortitis by quantifying enhanced aortic vascular inflammation along with calculation of total coronary plaque load (TCPL) and non-calcified atherosclerotic plaque load (NcAPL). In order to study the utility of aortitis in capturing eAg, we also assessed luminal stenosis atherosclerosis (LSA) and high-risk coronary plaques (HrCP). Material and methods: The study was conducted at our hospital between 1 April 2014 and 31 December 2017, and the analysis was done in July 2018. We recruited 180 consecutive psoriatic patients and subjected them to 18F-FDG PET. However, in order to characterise eAg, 160 out of 180 patients were also subjected to coronary angiographic computed tomographic studies (CACTS). Results: Among 180 psoriatic patients (76 women, 42%) (mean [SD] age, 51.1 [13.2] years), greater prevalence values of LSA (odd ratio [OR], 3.71; 95% confidence interval [CI], 1.84-7.89; p = 0.001) and HrCP (OR, 3.11; 95% CI: 1.54- 6.51; p = 0.003) along with enhanced TCPL (standardised ß = 0.44; p < 0.001) were observed in patients with enhanced aortitis. However, the association between aortitis and HrCP was controlled by low-attenuation plaque (LAP), while the same between aortitis and TCPL was controlled by NcAPL (ß = 0.45; p < 0.001). Conclusions: Association between aortitis and broad coronary angiographic indices was achieved and hence predicted the possibility of a surrogate role of aortitis in eAg. [ABSTRACT FROM AUTHOR]

Background: 18F-FDG PET is often utilized to determine BNCT selection due to the limited availability of 18F-BPA PET, which is performed by synthesizing 18F into the boron drug used for BNCT, although the uptake mechanisms between those are different. Additionally, only a few non-spatial point parameters, such as maximum SUV (SUVmax), have reported a correlation between those in previous studies. This study aimed to investigate the spatial accumulation pattern between those PET images in tumors, which would be expected to either show higher uptake on 18F-BPA PET or be utilized in clinical, to verify whether 18F-FDG PET could be used as a selection indicator for BNCT. Methods: A total of 27 patients with 30 lesions (11 squamous cell carcinoma, 9 melanoma, and 10 rhabdomyosarcoma) who received 18F-FDG and 18F-BPA PET within 2 weeks were enrolled in this study. The ratio of metabolic tumor volumes (MTVs) to GTV, histogram indices (skewness/kurtosis), and the correlation of total lesion activity (TLA) and non-spatial point parameters (SUVmax, SUVpeak, SUVmin, maximum tumor-to-normal tissue ratio (Tmax/N), and Tmin/N) were evaluated. After local rigid registration between those images, distances of locations at SUVmax and the center of mass with MTVs on each image and similarity indices were also assessed along its coordinate. Results: In addition to SUVmax, SUVpeak, and Tmax/N, significant correlations were found in TLA. The mean distance in SUVmax was 25.2 ± 24.4 mm and significantly longer than that in the center of mass with MTVs. The ratio of MTVs to GTV, skewness, and kurtosis were not significantly different. However, the similarities of MTVs were considerably low. The similarity indices of Dice similarity coefficient, Jaccard coefficient, and mean distance to agreement for MTV40 were 0.65 ± 0.21 , 0.51 ± 0.21 , and 0.27 ± 0.30 cm, respectively. Furthermore, it was worse in MTV50. In addition, spatial accumulation patterns varied in cancer types. Conclusions: Spatial accumulation patterns in tumors showed low similarity between 18F-FDG and 18F-BPA PET, although the various non-spatial point parameters were correlated. In addition, the spatial accumulation patterns were considerably different in cancer types. Therefore, the selection for BNCT using 18F-FDG PET should be compared carefully with using 18F-FBPA PET. [ABSTRACT FROM AUTHOR]

Single-modality medical images often cannot contain sufficient valid information to meet the information requirements of clinical diagnosis. The diagnostic efficiency is always limited by observing multiple images at the same time. Image fusion is a technique that combines functional modalities such as positron emission computed tomography (PET) and single-photon emission computed tomography (SPECT) with anatomical modalities such as computed tomography (CT) and magnetic resonance imaging (MRI) to supplement the complementary information. Meanwhile, fusing two anatomical images (like CT-MRI) is often required to replace single MRI, and the fused images can improve the efficiency and accuracy of clinical diagnosis. To this end, in order to achieve high-quality, high-resolution and rich-detail fusion without artificial prior, an unsupervised deep learning image fusion framework is proposed in this paper. It is named the back project dense generative adversarial network (BPDGAN) framework. In particular, we construct a novel network based on the back project dense block (BPDB) and convolutional block attention module (CBAM). The BPDB can effectively mitigate the impact of black backgrounds on image content. Conversely, the CBAM improves the performance of BPDGAN on the texture and edge information. To conclude, qualitative and quantitative experiments are tested to demonstrate the superiority of BPDGAN. In terms of quantitative metrics, BPDGAN outperforms the state-of-the-art comparisons by approximately 19.58%, 14.84%, 10.40% and 86.78% on AG, EI, Qabf and Qcv metrics, respectively. [ABSTRACT FROM AUTHOR]

A 76-year-old male, previously submitted enucleation renal-cell carcinoma (pT1) and prostatectomy for prostate cancer (Gleason score 3+5, pT3b pN0 pMx), was submitted to positron emission/computed tomography (PET/CT) with 18F-choline for restaging due to raised levels of prostate-specific antigen. PET/CT scan showed increased tracer incorporation corresponding to bone metastases in the left ischio-pubic ramus, also revealing 2 areas of increased tracer uptake in the cerebellum, subsequently confirmed by brain magnetic resonance imaging. The patient was urgently submitted to neurosurgery. Post-operative histology was positive for brain metastases from prostate cancer. [ABSTRACT FROM AUTHOR]

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Individual post-treatment dosimetry plays a crucial role in assessing the effectiveness of Y-90 transarterial radioembolization (TARE) treatment. Y-90 positron emission tomography (PET) imaging is widely regarded as the gold standard for post-TARE dosimetry. However, a major limitation of Y-90 PET imaging is the low positron yield of Y-90. This study aimed to address this limitation and improve individual dosimetry using Au nanoparticles (NPs)-induced pair production in Y-90 PET imaging. The GATE Monte Carlo platform was used to simulate post-TARE PET imaging. The study examined five levels of Au NP concentration in the liver tumor: 1%, 5%, 10%, 15%, and 20% by weight. The quality of the acquired PET images was evaluated by calculating the signal-to-background ratio (SBR) and contrast-to-noise ratio (CNR). The errors in PET-based dose volume histograms (DVH PET-based) and reference dose volume histograms (DVH refrence) were evaluated through various metrics, including root-mean-square error (RMSE), mean absorbed dose (D mean), and maximum absorbed dose (D max). The results showed that as the concentration of Au NPs increased in the tumor, the CNR and SBR values also increased. At concentrations 5 wt% and above, the difference in the values of D mean and D max obtained from the reference dosimetry and PET-based dosimetry is less than 5%. The calculated RMSE values indicated that concentrations 5 wt% and above exhibited acceptable agreement between the DVH PET-based and DVH refrence. When the concentration of Au NPs increases up to 5 wt%, the presence of Au NPs within the tumor does not significantly affect the D mean. Conversely, with the presence of Au NPs, at concentrations of 10, 15, and 20 wt%, the D mean within the tumor experiences reductions of approximately 6%, 10%, and 14%, respectively. The pair production was induced by simultaneously injecting Y-90 and Au NPs into the tumor. Our study demonstrated that dosimetry accuracy in TARE improved through induced positron PET imaging. As a consequence of the dose reduction phenomenon observed upon introducing Au NPs into the tumor, the optimal concentration of Au NPs for enhancing dosimetric precision was determined to be 5 wt%. • First study on PET imaging using induced positrons. • Inducing positrons by simultaneously injecting Y-90 and Au NPs in Radioembolization. • Induced positrons significantly enhance the quality of Y-90 PET images. • Precision post-treatment dosimetry through induced positrons PET imaging. [ABSTRACT FROM AUTHOR]

In the present study, we aimed to investigate the relationship between metabolic parameters of 18F-fluorodeoxyglucose positron emission computed tomography (18F-FDG PET/CT) and the expression of programmed death ligand-1 (PD-L1), as well as the prognostic value of PD-L1, in patients with surgically resected non-small-cell lung cancer (NSCLC). A total of 169 NSCLC patients who received preoperative 18F-FDG PET were retrospectively enrolled in the present study. The correlation between PD-L1 and patient characteristics was evaluated. Based on the expression of PD-L1 and metabolic parameters, patients were classified into low-, medium-, or high-risk groups. The maximum standardized uptake value (SUV max) and total lesion glycolysis (TLG) were significantly higher in NSCLC patients with high PD-L1 expression compared with the low expression group (P < 0.001 for all). Multivariate analysis revealed that pleural invasion (P < 0.001) and SUV max (P < 0.001) were independent predictors of PD-L1 expression. Survival analysis showed that tumor stage (P = 0.004) and pleural invasion (P = 0.007) were independent prognostic indicators of progression-free survival (PFS). Tumor stage (P = 0.001), TLG (P = 0.039), and PD-L1 expression (P = 0.001) were independent prognostic indicators of overall survival (OS). Patients of the high-risk group with high PD-L1 expression and high TLG had a poor prognosis compared with the low-risk group (P < 0.05) and medium-risk group (P < 0.05). In NSCLC patients, the SUV max of 18F-FDG PET/CT was a predictor of PD-L1 expression. The expression of PD-L1 and TLG were independent prognostic factors of OS. The risk stratification standard based on the PD-L1 expression and TLG provided valuable insights into the development of personalized treatment and follow-up. Registration number:ChiCTR2100051554. • SUV max was a predictor of PD-L1 expression in NSCLC patients. • PD-L1 expression and TLG were associated with prognosis. • Risk stratification standard provided valuable insights into the development of personalized treatment. [ABSTRACT FROM AUTHOR]

In this paper, we describe design considerations and promising detector technologies for time-of-flight positron emission tomography (TOF-PET). During a positron emission tomography scan, TOF-PET enables positron annihilation events to be positioned closer to their true origin along system response lines, thus facilitating improved reconstructed image signal-to-noise ratio, which has benefits such as better disease visualization and quantification, lower injected dose, and/or lower study duration. The degree of this image signal-to-noise ratio boost is determined by the annihilation photon pair coincidence time resolution of the detector system. Thus, there has been much research and development to advance detector coincidence time resolution, which is the foundation for future TOF-PET system designs. But when considering novel TOF-PET detector designs, it is important to select approaches that enhance coincidence time resolution without a tradeoff of decreasing detection efficiency (e.g., employing thin or low-density detector materials or low intra- or inter-module packing fraction, etc.). One might even argue that high coincidence detection efficiency (a.k.a. sensitivity) is the primary goal of any new positron emission tomography system design. In this paper, we will briefly discuss fundamental limitations on positron emission tomography coincidence time resolution using scintillation detectors and describe new detector configurations and electronic readout designs that attempt to address those constraints and achieve as low as 100 ps coincidence time resolution without compromising overall detection efficiency. We also concisely describe an innovative, non-scintillation-based, fast detection concept, which borrows ideas from the field of optics and could, in theory, achieve ~ 1 ps coincidence time resolution. If successful, these technologies will lead to next-generation systems that enhance TOF-PET's ability to visualize and quantify disease. [ABSTRACT FROM AUTHOR]

Objectives: Positron emission tomography (PET) is susceptible to patient movement during a scan. Head motion is a continuing problem for brain PET imaging and diagnostic assessments. Physical head restraints and external motion tracking systems are most commonly used to address to this issue. Data-driven methods offer substantial advantages, such as retroactive processing but typically require manual interaction for robustness. In this work, we introduce a time-of-flight (TOF) weighted positron emission particle tracking (PEPT) algorithm that facilitates fully automated, data-driven head motion detection and subsequent automated correction of the raw listmode data. Materials methods: We used our previously published TOF-PEPT algorithm Dustin Osborne et al. (2017), Tasmia Rahman Tumpa et al., Tasmia Rahman Tumpa et al. (2021) to automatically identify frames where the patient was near-motionless. The first such static frame was used as a reference to which subsequent static frames were registered. The underlying rigid transformations were estimated using weak radioactive point sources placed on radiolucent glasses worn by the patient. Correction of raw event data were achieved by tracking the point sources in the listmode data which was then repositioned to allow reconstruction of a single image. To create a "gold standard" for comparison purposes, frame-by-frame image registration based correction was implemented. The original listmode data was used to reconstruct an image for each static frame detected by our algorithm and then applying manual landmark registration and external software to merge these into a single image. Results: We report on five patient studies. The TOF-PEPT algorithm was configured to detect motion using a 500 ms window. Our event-based correction produced images that were visually free of motion artifacts. Comparison of our algorithm to a frame-based image registration approach produced results that were nearly indistinguishable. Quantitatively, Jaccard similarity indices were found to be in the range of 85-98% for the former and 84-98% for the latter when comparing the static frame images with the reference frame counterparts. Discussion: We have presented a fully automated data-driven method for motion detection and correction of raw listmode data. Easy to implement, the approach achieved high temporal resolution and reliable performance for head motion correction. Our methodology provides a mechanism by which patient motion incurred during imaging can be assessed and corrected post hoc. [ABSTRACT FROM AUTHOR]

Background: The staging of nasopharyngeal carcinoma (NPC) is of great value in treatment and prognosis. We explored whether a positron emission tomography/ magnetic resonance imaging (PET/MRI) based comprehensive model of radiomics features and semiquantitative parameters was useful for clinical evaluation of NPC staging. Materials and methods: A total of 100 NPC patients diagnosed with non-keratinized undifferentiated carcinoma were divided into early-stage group (I—II) and advanced-stage group (III—IV) and divided into the training set (n = 70) and the testing set (n = 30). Radiomics features (n = 396 × 2) of the primary site of NPC were extracted from MRI and PET images, respectively. Three major semiquantitative parameters of primary sites including maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) in all NPC patients were measured. After feature selection, three diagnostic models including the radiomics model, the metabolic parameter model, and the combined model were established using logistic regression model. Finally, internal validation was performed, and a nomogram for NPC comprehensive diagnosis has been made. Results: The radiomics model and metabolic parameter model showed an area under the curve (AUC) of 0.83 and 0.80 in the testing set, respectively. The combined model based on radiomics and semiquantitative parameters showed an AUC of 0.90 in the testing set, with the best performance among the three models. Conclusion: The combined model based on PET/MRI radiomics and semiquantitative parameters is of great value in the evaluation of clinical stage (early-stage group and advanced-stage group) of NPC. [ABSTRACT FROM AUTHOR]

Giardia lamblia is an intestinal protozoan with oral-fecal transmission. Infection is predominantly located in the small intestine. Giardiasis causes intraepithelial lymphocytosis in the small intestine which causes false‑positive fluorodeoxyglucose (FDG) uptake mimicking malignancy. We present here an interesting image of fluorine‑18 FDG positron emission tomography/computed tomography showing jejunal uptake caused by giardiasis in a known case of lymphoma. [ABSTRACT FROM AUTHOR]

Background: Advancements in hybrid positron emission tomography-magnetic resonance (PET-MR) systems allow for combining the advantages of each modality. Integrating information from MRI and PET can be valuable for diagnosing and treating neurological disorders. However, combining diffusion MRI (dMRI) and PET data, which provide highly complementary information, has rarely been exploited in image post-processing. dMRI has the ability to investigate the white matter pathways of the brain through fibre tractography, which enables comprehensive mapping of the brain connection networks (the "connectome"). Novel methods are required to combine information present in the connectome and PET to increase the full potential of PET-MRI. Methods: We developed a CONNectome-based Non-Local Means (CONN-NLM) filter to exploit synergies between dMRI-derived structural connectivity and PET intensity information to denoise PET images. PET-MR data are parcelled into a number of regions based on a brain atlas, and the inter-regional structural connectivity is calculated based on dMRI fibre-tracking. The CONN-NLM filter is then implemented as a post-reconstruction filter by combining the nonlocal means filter and a connectivity-based cortical smoothing. The effect of this approach is to weight voxels with similar PET intensity and highly connected voxels higher when computing the weighted-average to perform more informative denoising. The proposed method was first evaluated using a novel computer phantom framework to simulate realistic hybrid PET-MR images with different lesion scenarios. CONN-NLM was further assessed with clinical dMRI and tau PET examples. Results: The results showed that CONN-NLM has the capacity to improve the overall PET image quality by reducing noise while preserving lesion contrasts, and it outperformed a range of filters that did not use dMRI information. The simulations demonstrate that CONN-NLM can handle various lesion contrasts consistently, as well as lesions with different levels of inter-connectivity. Conclusion: CONN-NLM has unique advantages of providing more informative and accurate PET smoothing by adding complementary structural connectivity information from dMRI, representing a new avenue to exploit synergies between MRI and PET. [ABSTRACT FROM AUTHOR]

A positron emission tomography (PET)–magnetic resonance imaging (MRI) hybrid system has been developed to improve the accuracy of molecular imaging with structural imaging. However, the mismatch in spatial resolution between the two systems hinders the use of the hybrid system. As the magnetic field of the MRI increased up to 7.0 tesla in the commercial system, the performance of the MRI system largely improved. Several technical attempts in terms of the detector and the software used with the PET were made to improve the performance. As a result, the high resolution of the PET–MRI fusion system enables quantitation of metabolism and molecular information in the small substructures of the brainstem, hippocampus, and thalamus. Many studies on psychiatric disorders, which are difficult to diagnose with medical imaging, have been accomplished using various radioligands, but only a few studies have been conducted using the PET–MRI fusion system. To increase the clinical usefulness of medical imaging in psychiatric disorders, a high-resolution PET–MRI fusion system can play a key role by providing important information on both molecular and structural aspects in the fine structures of the brain. The development of high-resolution PET–MR systems and their potential roles in clinical studies of psychiatric disorders were reviewed as prospective views in future diagnostics. [ABSTRACT FROM AUTHOR]

Uterine leiomyoma with hepatic vasculopathy, specifically non-cirrhotic portal fibrosis (NCPF), has hitherto been undescribed. NCPF is characterized by elevated portal pressure sans cirrhosis and has previously not been described in association with a gynecological pathology. We report the case of a female under evaluation for a heterogeneously enhancing intrauterine mass with multiple hepatic lesions with increased uptake of fluorodeoxyglucose on positron emission analysis. Fibroscan values were increased. Histopathologic evaluations revealed a leiomyoma with liver tissue showing tubercular granulomas, thin wispy fibrotic strands, and rounded portal tracts pointed to NCPF. No evidence of malignancy was seen. Metabolic imaging may be unreliable to distinguish between benign and malignant uterine pathology and granulomatous and malignant hepatic lesions. Elastography may also be ineffective in diagnosing the etiology of liver fibrosis. Histopathological analysis hence remains essential despite noninvasive tests. Further research is required on females afflicted with NCPF to exclude a hormonal link. [ABSTRACT FROM AUTHOR]

The purpose of this study is to assess a rare case of fetal radiation absorbed dose here through 18F-Fludeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) in early pregnancy (5-week-old fetus). The fetal absorbed dose due to the radiation emitted from the mother's body, the fetus self-dose, and the dose received from CT were computed. The 35-year-old patient, weighing 85 kg, was injected with 370 MBq of 18F-FDG. Imaging started at 1 h with CT acquisition followed by PET imaging. The photon and positron self-dose was calculated by applying the Monte Carlo (MC) GATE (GEANT 4 Application for Tomographic Emission) code. The volume of absorbed dose from the mother's body organs and the absorbed dose from the CT were added to the self-dose to obtain the final dose. The volume of self-dose obtained through MC simulation for the fetus was 3.3 × 10-2 mGy/MBq, of which 2.97 × 10-2 mGy/MBq was associated with positrons and 0.33 × 10-2 mGy/MBq was associated with photons. Biologically, the absorbed dose from CT, 7.3 mGy, had to be added to the total dose. The absorbed dose by the fetus during early pregnancy was higher than the standard value of 2.2 × 10-2 mGy/MBq (MIRD DER) because, during the examinations, the mother's bladder was full. This issue was a concern during updating standards. [ABSTRACT FROM AUTHOR]

This article presents a physics-informed deep learning method for the quantitative estimation of the spatial coordinates of gamma interactions within a monolithic scintillator, with a focus on Positron Emission Tomography (PET) imaging. A Density Neural Network approach is designed to estimate the 2-dimensional gamma photon interaction coordinates in a fast lead tungstate (PbWO 4) monolithic scintillator detector. We introduce a custom loss function to estimate the inherent uncertainties associated with the reconstruction process and to incorporate the physical constraints of the detector. This unique combination allows for more robust and reliable position estimations and the obtained results demonstrate the effectiveness of the proposed approach and highlights the significant benefits of the uncertainties estimation. We discuss its potential impact on improving PET imaging quality and show how the results can be used to improve the exploitation of the model, to bring benefits to the application and how to evaluate the validity of the given prediction and the associated uncertainties. Importantly, our proposed methodology extends beyond this specific use case, as it can be generalized to other applications beyond PET imaging. [ABSTRACT FROM AUTHOR]