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Aim: CT images can identify structural and opacity alterations of the lungs while nuclear medicine's lung perfusion studies show the homogeneity (or lack of) of blood perfusion on the organ. Therefore, the use of SPECT/CT in lung perfusion scintigraphies can help physicians to assess anatomical and functional alterations of the lungs and to differentiate between acute and chronic disease. Objective: To develop a computer-aided methodology to quantify the total global perfusion of the lungs via SPECT/CT images and to compare these results with parenchymal alterations obtained in CT images. Methods: 39 perfusion SPECT/CT images collected retrospectively from the Nuclear Medicine Facility of Botucatu Medical School's Clinics Hospital in São Paulo, Brazil, were analyzed. Anatomical lung impairments (emphysema, collapsed and infiltrated tissue) and the functional percentage of the lungs (blood perfusion) were quantified from CT and SPECT images, with the aid of the free, open-source software 3D Slicer. The results obtained with 3D Slicer (3D-TGP) were also compared to the total global perfusion of each patient's found on their medical report, obtained from visual inspection of planar images (2D-TGP). Results: This research developed a novel and practical methodology for obtaining lungs' total global perfusion from SPECT/CT images in a semiautomatic manner. 3D-TGP versus 2D-TGP showed a bias of 7% with a variation up to 67% between the two methods. Perfusion percentage showed a weak positive correlation with infiltration (p = 0.0070 and ρ = 0.43) and collapsed parenchyma (p = 0.040 and ρ = 0.33). Conclusions: This research brings meaningful contributions to the scientific community because it used a free open-source software to quantify the lungs blood perfusion via SPECT/CT images and pointed that the relationship between parenchyma alterations and the organ's perfusion capability might not be so direct, given compensatory mechanisms. [ABSTRACT FROM AUTHOR]

Background: The limited spatial resolution in SPECT images leads to partial volume effect (PVE), degrading the subsequent dosimetric accuracy. We aim to quantitatively evaluate PVE and partial volume corrections (PVC), i.e., recovery coefficient (RC)-PVC (RC-PVC), reblurred Van-Cittert (RVC) and iterative Yang (IY), in 177Lu-PSMA-617 SPECT images. Methods: We employed a geometrical cylindrical phantom containing five spheres (diameters ranging from 20 to 40 mm) and 40 XCAT phantoms with various anatomical variations and activity distributions. SIMIND Monte Carlo code was used to generate realistic noisy projections. In the clinical study, sequential quantitative SPECT/CT imaging at 4 time-points post 177Lu-PSMA-617 injections were analyzed for 10 patients. Iterative statistical reconstruction methods were used for reconstruction with attenuation, scatter and geometrical collimator detector response corrections, followed by post-filters. The RC-curves were fit based on the geometrical phantom study and applied for XCAT phantom and clinical study in RC-PVC. Matched and 0.5-2.0 voxels (2.54–10.16 mm) mismatched sphere masks were deployed in IY. The coefficient of variation (CoV) was measured on a uniform background on the geometrical phantom. RCs of spheres and mean absolute activity error (MAE) of kidneys and tumors were evaluated in simulation data, while the activity difference was evaluated in clinical data before and after PVC. Results: In the simulation study, the spheres experienced significant PVE, i.e., 0.26 RC and 0.70 RC for the 20 mm and 40 mm spheres, respectively. RVC and IY improved the RC of the 20 mm sphere to 0.37 and 0.75 and RC of the 40 mm sphere to 0.96 and 1.04. Mismatch in mask increased the activity error for all spheres in IY. RVC increased noise and caused Gibbs ringing artifacts. For XCAT phantoms, both RVC and IY performed comparably and were superior to RC-PVC in reducing the MAE of the kidneys. However, IY and RC-PVC outperformed RVC for tumors. The XCAT phantom study and clinical study showed a similar trend in the kidney and tumor activity differences between non-PVC and PVC. Conclusions: PVE greatly impacts activity quantification, especially for small objects. All PVC methods improve the quantification accuracy in 177Lu-PSMA SPECT. [ABSTRACT FROM AUTHOR]

Background: Accurate attenuation correction (AC) is vital in nuclear medicine, particularly for quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. This study aimed to establish a CT-free quantification technology in kidney SPECT imaging using deep learning to generate synthetic attenuation maps (μ-maps) from SPECT data, thereby reducing radiation exposure and eliminating the need for CT scans. Results: A dataset of 1000 Tc-99m DTPA SPECT/CT scans was analyzed for training (n = 800), validation (n = 100), and testing (n = 100) using a modified 3D U-Net for deep learning. The study investigated the use of primary emission and scattering SPECT data, normalization methods, loss function optimization, and up-sampling techniques for optimal μ-map generation. The problem of checkerboard artifacts, unique to μ-map generation from SPECT signals, and the effects of iodine contrast media were evaluated. The addition of scattering SPECT to primary emission SPECT imaging, logarithmic maximum normalization, the combination of absolute difference loss (L1) and three times the absolute gradient difference loss (3 × LGDL), and the nearest-neighbor interpolation significantly enhanced AI performance in μ-map generation (p < 0.00001). Checkerboard artifacts were effectively eliminated using the nearest-neighbor interpolation technique. The developed AI algorithm produced μ-maps neutral to the presence of iodine contrast and showed negligible contrast effects on quantitative SPECT measurement, such as glomerular filtration rate (GFR). The potential reduction in radiation exposure by transitioning to AI-based CT-free SPECT imaging ranges from 45.3 to 78.8%. Conclusion: The study successfully developed and optimized a deep learning algorithm for generating synthetic μ-maps in kidney SPECT images, demonstrating the potential to transition from conventional SPECT/CT to CT-free SPECT imaging for GFR measurement. This advancement represents a significant step towards enhancing patient safety and efficiency in nuclear medicine. [ABSTRACT FROM AUTHOR]

To develop and validate a machine learning (ML) model based on high-frequency ultrasound (HFUS) images with the aim to identify the functional status of parathyroid glands (PTGs) in secondary hyper-parathyroidism (SHPT) patients. This retrospective study enrolled 60 SHPT patients (27 female, 33 male; mean age: 51.2 years) with 184 PTGs detected from February 2016 to June 2022. All enrollments underwent single-photon emission computed tomography/computed tomography and contrast-enhanced ultrasound examinations. The PTGs were randomly divided into training (n = 147) and testing datasets (n = 37). Four effective ML classifiers were used and combined models incorporating multi-modal HFUS visual signs and radiomics features was constructed based on the optimal classifier. Model performance was compared in terms of discrimination, calibration and clinical utility. The Shapley additive explanation method was used to explain and visualize the main predictors of the optimal model. This model, using a random forest classifier algorithm, outperformed other classifiers. Based on optimal classifier features, the model constructed from ultrasound visual and ML features achieved a favorable performance in the prediction of hyper-functioning PTGs. Compared with the traditional visual model, the ultrasound-based ML model achieved significant (p = 0.03) improvement (area under the curve: 0.859 vs. 0.629) and higher sensitivity (100.0% vs. 94.1%) and accuracy (86.5% vs. 67.6%). Among the predictors attributed to model development, large size and high echogenic heterogeneity of PTGs in ultrasonographic images were more often associated with high risk of hyper-functioning PTGs. The ultrasound-based ML model for identifying hyper-functioning PTGs in SHPT patients showed good performance and interpretability using high-frequency ultrasonographic images, which may facilitate clinical management. [ABSTRACT FROM AUTHOR]

Background: Asymmetric joint load is the main cause of development of ankle osteoarthritis (OA). Realignment surgery aims to transfer ankle joint load from the degenerative area toward the uninvolved area. Determination of the optimal shift is still challenging. When the degenerative area is correlated to the ankle joint mechanical axis establishing an optimal target angle for corrective surgery may become more feasible. The primary aim of our study was to investigate if the area of ankle joint activation on single-photon emission computed tomography and conventional computed tomography (SPECT/CT) imaging correlates with the mechanical ankle joint axis point (MAJAP). Methods: In this cross-sectional study, patients 18 years or older with symptomatic asymmetric ankle OA and a hip-to-calcaneus long leg view with SPECT/CT of the affected ankle were eligible for inclusion. Primary outcome was MAJAP divided into 3 alignment categories (medial shift, neutral, lateral shift). SPECT/CT activation was determined in 8 different areas of the ankle joint. A Spearman rho correlation coefficient was calculated to investigate the relationship between the alignment categories and SPECT/CT activation in the 8 areas. Results: Forty-nine patients (mean age 58.8 [SD 10.0] years) with 52 ankles with moderate to severe asymmetric OA were included. A significantly (Spearman rho −0.379 [ P =.006] and Spearman rho −0.279 [ P =.045]) higher proportion of ankles with radioisotope uptake in the anteromedial ankle joint areas (zones 1 and 5) was seen in the medial shift category. A significantly (Spearman rho.312 (P =.025)) higher proportion of ankles with radioisotope uptake in the anterolateral ankle joint area (zone 8) was seen in the lateral shift category. Conclusion: We found in this patient group that the area of SPECT/CT uptake in asymmetric ankle OA was associated to MAJAP measured on hip-to-calcaneus weightbearing views, although the strength of the correlation is weak to moderate. Consequently, nonweightbearing metabolic SPECT/CT radiotracer uptake has the potential to help determine the area to unload in ankle joint-preserving alignment surgery. [ABSTRACT FROM AUTHOR]

Abstract Background The limited spatial resolution in SPECT images leads to partial volume effect (PVE), degrading the subsequent dosimetric accuracy. We aim to quantitatively evaluate PVE and partial volume corrections (PVC), i.e., recovery coefficient (RC)-PVC (RC-PVC), reblurred Van-Cittert (RVC) and iterative Yang (IY), in 177Lu-PSMA-617 SPECT images. Methods We employed a geometrical cylindrical phantom containing five spheres (diameters ranging from 20 to 40 mm) and 40 XCAT phantoms with various anatomical variations and activity distributions. SIMIND Monte Carlo code was used to generate realistic noisy projections. In the clinical study, sequential quantitative SPECT/CT imaging at 4 time-points post 177Lu-PSMA-617 injections were analyzed for 10 patients. Iterative statistical reconstruction methods were used for reconstruction with attenuation, scatter and geometrical collimator detector response corrections, followed by post-filters. The RC-curves were fit based on the geometrical phantom study and applied for XCAT phantom and clinical study in RC-PVC. Matched and 0.5-2.0 voxels (2.54–10.16 mm) mismatched sphere masks were deployed in IY. The coefficient of variation (CoV) was measured on a uniform background on the geometrical phantom. RCs of spheres and mean absolute activity error (MAE) of kidneys and tumors were evaluated in simulation data, while the activity difference was evaluated in clinical data before and after PVC. Results In the simulation study, the spheres experienced significant PVE, i.e., 0.26 RC and 0.70 RC for the 20 mm and 40 mm spheres, respectively. RVC and IY improved the RC of the 20 mm sphere to 0.37 and 0.75 and RC of the 40 mm sphere to 0.96 and 1.04. Mismatch in mask increased the activity error for all spheres in IY. RVC increased noise and caused Gibbs ringing artifacts. For XCAT phantoms, both RVC and IY performed comparably and were superior to RC-PVC in reducing the MAE of the kidneys. However, IY and RC-PVC outperformed RVC for tumors. The XCAT phantom study and clinical study showed a similar trend in the kidney and tumor activity differences between non-PVC and PVC. Conclusions PVE greatly impacts activity quantification, especially for small objects. All PVC methods improve the quantification accuracy in 177Lu-PSMA SPECT.

Abstract To explore the performance of 99mTc-diethylene triaminepentaacetic acid (DTPA) SPECT/CT texture analysis in evaluating the activity of thyroid-associated ophthalmopathy (TAO) . This retrospective study examined 115 TAO patients from a single institution as an internal cohort and 58 TAO patients from another institution as an external validation set. Patients in the internal cohort were randomly divided into training (n = 81) and internal validation sets (n = 34). Radiomics signatures were constructed with the minimal redundancy maximal relevance and least absolute shrinkage and selection operator algorithms in training set. Multivariate logistic regression analysis was used to develop a clinical model and a combined clinical–radiomics model. Diagnostic performance of models was evaluated using receiver operating characteristic curve analysis, calibration curves and decision curve analysis. Compared with CT and SPECT radiomics models, Rad-scoreSPECT/CT demonstrated the best performance with areas under the receiver operating characteristic curve of 0.94 and 0.91 in the training and test sets, respectively. The combined clinical-radiomics model exhibited significantly better performance in evaluating TAO activity. Our results demonstrate the validity of a multimodal radiomic model of 99mTc-DTPA-SPECT/CT to assess TAO activity. The combined clinical-radiomics model exhibited significantly better diagnostic performance than the clinical model.

Abstract Background Accurate attenuation correction (AC) is vital in nuclear medicine, particularly for quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) imaging. This study aimed to establish a CT-free quantification technology in kidney SPECT imaging using deep learning to generate synthetic attenuation maps (μ-maps) from SPECT data, thereby reducing radiation exposure and eliminating the need for CT scans. Results A dataset of 1000 Tc-99m DTPA SPECT/CT scans was analyzed for training (n = 800), validation (n = 100), and testing (n = 100) using a modified 3D U-Net for deep learning. The study investigated the use of primary emission and scattering SPECT data, normalization methods, loss function optimization, and up-sampling techniques for optimal μ-map generation. The problem of checkerboard artifacts, unique to μ-map generation from SPECT signals, and the effects of iodine contrast media were evaluated. The addition of scattering SPECT to primary emission SPECT imaging, logarithmic maximum normalization, the combination of absolute difference loss (L1) and three times the absolute gradient difference loss (3 × LGDL), and the nearest-neighbor interpolation significantly enhanced AI performance in μ-map generation (p < 0.00001). Checkerboard artifacts were effectively eliminated using the nearest-neighbor interpolation technique. The developed AI algorithm produced μ-maps neutral to the presence of iodine contrast and showed negligible contrast effects on quantitative SPECT measurement, such as glomerular filtration rate (GFR). The potential reduction in radiation exposure by transitioning to AI-based CT-free SPECT imaging ranges from 45.3 to 78.8%. Conclusion The study successfully developed and optimized a deep learning algorithm for generating synthetic μ-maps in kidney SPECT images, demonstrating the potential to transition from conventional SPECT/CT to CT-free SPECT imaging for GFR measurement. This advancement represents a significant step towards enhancing patient safety and efficiency in nuclear medicine.

PURPOSE: To characterize the recovery of diagnostic cardiovascular procedure volumes in U.S. and non-U.S. facilities in the year following the initial COVID-19 outbreak. MATERIALS AND METHODS: The International Atomic Energy Agency (IAEA) coordinated a worldwide study called the IAEA Noninvasive Cardiology Protocols Study of COVID-19 2 (INCAPS COVID 2), collecting data from 669 facilities in 107 countries, including 93 facilities in 34 U.S. states, to determine the impact of the pandemic on diagnostic cardiovascular procedure volumes. Participants reported volumes for each diagnostic imaging modality used at their facility for March 2019 (baseline), April 2020, and April 2021. This secondary analysis of INCAPS COVID 2 evaluated differences in changes in procedure volume between U.S. and non-U.S. facilities and among U.S. regions. Factors associated with return to prepandemic volumes in the United States were also analyzed in a multivariable regression analysis. RESULTS: Reduction in procedure volumes in April 2020 compared with baseline was similar for U.S. and non-U.S. facilities (-66% vs -71%, P = .27). U.S. facilities reported greater return to baseline in April 2021 than did all non-U.S. facilities (4% vs -6%, P = .008), but there was no evidence of a difference when comparing U.S. facilities with non-U.S. high-income country (NUHIC) facilities (4% vs 0%, P = .18). U.S. regional differences in return to baseline were observed between the Midwest (11%), Northeast (9%), South (1%), and West (-7%, P = .03), but no studied factors were significant predictors of 2021 change from prepandemic baseline. CONCLUSION: The reductions in cardiac testing during the early pandemic have recovered within a year to prepandemic baselines in the United States and NUHICs, while procedure volumes remain depressed in lower-income countries.Keywords: SPECT, Cardiac, Epidemiology, Angiography, CT Angiography, CT, Echocardiography, SPECT/CT, MR Imaging, Radionuclide Studies, COVID-19, Cardiovascular Imaging, Diagnostic Cardiovascular Procedure, Cardiovascular Disease, Cardiac Testing Supplemental material is available for this article. © RSNA, 2023.

Abstract Background Lymph node (LN) metastasis is a significant prognostic factor for esophageal squamous cell carcinoma (ESCC), and there are no satisfactory methods for accurately predicting metastatic LNs. The present study aimed to assess the efficacy of 99mTc‐3PRGD2 single‐photon emission computed tomography (SPECT)/computed tomography (CT) for diagnosing metastatic LNs in ESCC. Methods A total of 15 enrolled patients with ESCC underwent 99mTc‐3PRGD2 SPECT/CT and 18F‐fluorodeoxyglucose positron emission tomography‐computed tomography (18F‐FDG PET/CT) examinations preoperatively. High‐definition bone carving reconstruction technology (HD‐xSPECT Bone) was applied to quantitatively assess the LN's SUVmax via SPECT/CT. The two methods were compared for diagnosing metastatic LNs with pathology as the gold standard. Results Among 15 patients, 23 metastatic lymph node stations (mLNSs) were predicted by SPECT/CT, with a mean SUVmax of 2.71 ± 1.34, of which 15 were pathologically confirmed; 32 mLNSs were predicted by PET/CT with a mean SUVmax of 4.41 ± 4.02, of which 17 were pathologically confirmed. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of SPECT/CT for diagnosing metastatic LNs were 62.50%, 91.30%, 85.34%, 65.22%, and 90.32%, respectively, and those of PET/CT were 70.83%, 83.70%, 81.03%, 53.13%, and 91.67%, respectively. There was no significant difference in sensitivity (p = 0.061) or specificity (p = 0.058) between the two methods. The AUCSPECT/CT was 0.816 and the SUVmax threshold was 2.5. Conclusion 99mTc‐3PRGD2 SPECT/CT might be an effective method for diagnosing metastatic LNs in ESCC, especially in combination with HD‐xSPECT Bone. The diagnostic efficiency of this method was noninferior to that of 18F‐FDG PET/CT. The SUVmax threshold of 2.5 showed the highest agreement with the pathology findings.

Abstract Background Prompt and accurate diagnosis of prostate cancer (PCa) is of paramount importance for effective treatment planning. While Gallium-68 labeled prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) has proven efficacy in detecting PCa, limited availability poses challenges. As a potential alternative, [99mTc]Tc-PSMA single photon emission computed tomography (SPECT)/computed tomography (CT) holds promise. This systematic review and meta-analysis aimed to evaluate the diagnostic value of [99mTc]Tc-PSMA SPECT/CT for prostate cancer. Methods A comprehensive search of PubMed, Cochrane, EMBASE, Scopus, Ovid, and Web of Science databases was conducted until July 2024. Sensitivity and specificity data were extracted to assess the diagnostic accuracy of [99mTc]Tc-PSMA SPECT/CT, while the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool was used to evaluate study quality. Statistical analyses were performed using STATA 18, with MetaDisc 1.4 employed to detect threshold effects. Diagnostic accuracy indicators, including sensitivity, specificity, diagnostic odds ratio (DOR), negative likelihood ratio (LR-), and positive likelihood ratio (LR+), were pooled. The area under the curve (AUC) of the combined model was calculated using summary receiver-operating characteristic (SROC) curves. Results Seven studies meeting the inclusion criteria were identified from an initial pool of 1467 articles, with no publication bias observed. The pooled sensitivity, specificity, and AUC of [99mTc]Tc-PSMA SPECT/CT were found to be 0.89 (95% CI, 0.84–0.93), 0.92 (95% CI, 0.67–0.99), and 0.93 (95% CI, 0.90–0.95), respectively. Additionally, the comprehensive diagnostic odds ratio, diagnostic score, positive likelihood ratio, and negative likelihood ratio were calculated as 95.24 (95% CI, 17.30-524.41), 4.56 (95% CI, 2.85–6.26), 11.35 (95% CI, 2.31–55.71), and 0.12 (95% CI, 0.08–0.18), respectively. Conclusions In conclusion, our findings demonstrate that [99mTc]Tc-PSMA SPECT/CT exhibits favorable diagnostic performance for prostate cancer and can provide valuable supplementary information, particularly in regions and settings where [68Ga]Ga-PSMA PET/CT availability is limited, such as remote areas. These results highlight the potential of [99mTc]Tc-PSMA SPECT/CT as a valuable tool in the diagnosis and management of prostate cancer, warranting further investigation and validation in larger patient cohorts.

Abstract Background Relapsing Polychondritis(RP) is a rare rheumatic immune disease. As with most diseases, if intervention is delayed, the patient’s prognosis is worse. Currently, the diagnostic criteria used in clinical practice do not include CT, PET/CT, SPECT/CT and other new imaging examinations that have developed rapidly in recent years. However, these examinations have some special manifestations for RP, which can help clinicians diagnose RP earlier and distinguish it from other diseases. Case presentation These five RP patients all had respiratory symptoms such as cough and wheezing as the first symptom, which could not be diagnosed in time according to the previous diagnostic criteria. The clinical data of the five patients are listed in Table 1. The relatively specific manifestations of SPECT/CT examination provided clinicians with very valuable clues to help them advance the diagnosis time. Conclusions The application of SPECT/CT bone imaging in early diagnosing RP proves to be effective, enabling clinicians to intervene promptly and enhance the overall well-being and quality of life for individuals affected by this condition.

Abstract Introduction This study aims to evaluate the use of CT-based whole kidney parenchyma (WKP) segmentation in 177Lu-DOTATATE dosimetry. Specifically, it investigates whether WKP volumes change during treatment and evaluates the accuracy of applying a single delineated WKP volume for dosimetry. Furthermore, it aims to determine the cause of WKP volume changes—whether caused by radiation or amino acid infusion—by comparing them with spleen volume changes as a marker for radiation-induced alterations. Methods SPECT/CT images of 18 patients were acquired over the abdomen approximately 4 h (h) (D0), 24 h (D1), 48 h (D2) and 168 h (D7) post-administration of 177Lu-DOTATATE. CT guided WKP volumes were measured before (baseline) and during treatment. Kidney activity concentrations at each time point were derived from CT-segmented WKP overlaid on SPECT scans. The accuracy of using WKP segmentation from a single CT for all time points was assessed against the gold standard of segmenting each WKP individually. Time-integrated activity calculations were based on a tri-exponential curve fit of the kidney activity concentration over time. Kidney absorbed doses were estimated under the assumption of local energy deposition. Additionally, the impact of various partial volume correction methods on dosimetry was evaluated. Results Whole-kidney parenchyma (WKP) volumes, ranging from 31 to 243 mL, showed a gradual increase from baseline (mean ± SD = 130.6 ± 46.1 mL) at the initial time points D0 (138.5 ± 44.7 mL) and D1 (139.4 ± 41.6 mL), followed by a slight decrease at D2 (132.8 ± 44.5 mL) and a further decrease at D7 (129.2 ± 42.7 mL). The volume increase at D0 and D1 was statistically significant. Spleen volume did not change during treatment, suggesting that amino acid infusion rather than irradiation effects caused WKP volume changes. Bland-Altman analysis revealed WKP volume biases of 8.77% (D0 vs. BL), 10.77% (D1 vs. BL), 1.10% (D2 vs. BL), and 1.10% (D7 vs. BL), with corresponding uncertainties of 24.4%, 23.6%, 25.4%, and 25.4%, respectively. When WKP segmentation from a single CT is applied across all SPECTs, these WKP volume changes could overestimate the activity concentration and mean absorbed doses up to 4.3% and 2.5%, respectively. The absorbed dose uncertainties using a recovery coefficient (RC) of 0.85 for single-time-point WKP delineation increase the absorbed dose uncertainty by 4% compared to the use of patient-specific RCs and time specific segmentation of WKP volumes. Conclusions Kidney volume exhibited significant variation form D0 to D7, affecting the precision of dosimetry calculation, primarily due to errors in whole-kidney parenchyma (WKP) delineation. Notably, using WKP segmentation from a single CT scan applied to sequential SPECT images introduce further uncertainty and may lead to an overestimation of the absorbed dose. The fluctuations in kidney volume are most likely attributable to amino acid infusion.

Abstract Background The application of semi-conductor detectors such as cadmium–zinc–telluride (CZT) in nuclear medicine improves extrinsic energy resolution and count sensitivity due to the direct conversion of gamma photons into electric signals. A 3D-ring pixelated CZT system named StarGuide was recently developed and implemented by GE HealthCare for SPECT acquisition. The system consists of 12 detector columns with seven modules of 16 × 16 CZT pixelated crystals, each with an integrated parallel-hole tungsten collimator. The axial coverage is 27.5 cm. The detector thickness is 7.25 mm, which allows acquisitions in the energy range [40–279] keV. Since there is currently no performance characterization specific to 3D-ring CZT SPECT systems, the National Electrical Manufacturers Association (NEMA) NU 1-2018 clinical standard can be tailored to these cameras. The aim of this study was to evaluate the performance of the SPECT/CT StarGuide system according to the NEMA NU 1-2018 clinical standard specifically adapted to characterize the new 3D-ring CZT. Results Due to the integrated collimator, the system geometry and the pixelated nature of the detector, some NEMA tests have been adapted to the features of the system. The extrinsic measured energy resolution was about 5–6% for the tested isotopes (99mTc, 123I and 57Co); the maximum count rate was 760 kcps and the observed count rate at 20% loss was 917 kcps. The system spatial resolution in air extrapolated at 10 cm with 99mTc was 7.2 mm, while the SPECT spatial resolutions with scatter were 4.2, 3.7 and 3.6 mm in a central, radial and tangential direction respectively. Single head sensitivity value for 99mTc was 97 cps/MBq; with 12 detector columns, the system volumetric sensitivity reached 520 kcps MBq−1 cc−1. Conclusions The performance tests of the StarGuide can be performed according to the NEMA NU 1-2018 standard with some adaptations. The system has shown promising results, particularly in terms of energy resolution, spatial resolution and volumetric sensitivity, potentially leading to higher quality clinical images.

Abstract Background Parathyroid scan is an important imaging modality for localizing hyperfunctioning parathyroid tissue in patients with hyperparathyroidism. Unfortunately, whether early or delayed timing is the optimal protocol for [99mTc]Tc-MIBI SPECT/CT parathyroid remains under debate. This study aimed to evaluate the agreement and compare the confidence levels of physicians when interpreting early and delayed [99mTc]Tc-MIBI SPECT/CT parathyroid scans. Additionally, it sought to identify clinical factors that related to positive scan result. We conducted a prospective study where the early and delayed [99mTc]Tc-MIBI SPECT/CT was separately interpreted as either positive or negative. Furthermore, these interpretations were categorized based on whether they fell within more or less confidence levels of the readers and were correlated with clinical information. Results We enrolled 39 patients with hyperparathyroidism with 158 possible locations of parathyroid glands. The per-location agreement between the early and delayed scans was moderate (concordant rate: 80.3%, Kappa = 0.558), and the per-patient agreement was slight (concordant rate: 71.8%, Kappa = 0.093). The confidence of interpretation was significantly higher for the delayed scans. Calcium supplementation, low serum parathyroid hormone levels, and low serum phosphate levels were associated with positive early scans. High calcium level and high parathyroid hormone levels were associated with positive delayed scans. Conclusions Our study highlights the impact of the timing of SPECT/CT in [99mTc]Tc-MIBI parathyroid scans. The different confidence levels between early and delayed scans, along with clinical factors, imply that various factors affect parathyroid scan interpretation, and individualized scanning protocols adjusted for specific settings may be needed to optimize the successful localization of hyperfunctioning parathyroid tissue.

Perforation of the bowel can be a life-threatening condition and is usually clinically diagnosed when a patient presents with such features as severe abdominal pain, tenderness, and tachycardia. Bowel perforation may be corroborated by various conventional imaging modalities, including X-ray, ultrasonography, computed tomography, and magnetic resonance imaging. Nuclear medicine imaging modalities seldom have a role to play in these settings. Rarely diagnosis of perforation may be missed if it is concealed and does not present with the usual signs. Mostly the perforation will eventually be diagnosed if they develop signs and symptoms and is taken up for an exploratory laparotomy. A delay in diagnosis can later lead to significant patient morbidity or even mortality. This report describes a case where possible intestinal perforation was suspected on a 99mTc-DTPA renogram in a postoperative patient with significant urine leak, the presence of which was confirmed intraoperatively. To our knowledge, this was the first such case in the literature.

Meckel's diverticulum is the most prevalent congenital anomaly of the gastrointestinal tract, identified in 2% of the population according to autopsy studies. Most patients remain asymptomatic throughout their lives and are typically diagnosed when complications arise. The diagnosis can be challenging, but imaging is crucial for promptly identifying and distinguishing it from other conditions that have similar clinical manifestations. A 13-year-old male was admitted with a 5-day history of rectal bleeding. The patient continued to experience painless gastrointestinal bleeding, indicating the performance of a Tc-99m pertechnetate scintigraphy or Meckel's scan. Planar images revealed focal uptake within the right hemiabdomen, suggestive of the presence of a Meckel's diverticulum. Subsequent laparotomy surgery confirmed the presence of a Meckel's diverticulum located 50 cm from the ileocecal valve. Histopathological examination of the resected specimen confirmed Meckel's diverticulum with ectopic gastric mucosa. This patient with Meckel's diverticulum exhibited minimal abdominal symptoms, and there were no other complications such as intussusception, which could lead to bowel obstruction. Technetium-99m pertechnetate scintigraphy is a common method for evaluating children with unexplained gastrointestinal tract bleeding. SPECT/CT fusion imaging enables the simultaneous fusion of functional and anatomical information, preventing false-negative scintigraphy examinations. Its capability to precisely localize activity in abnormal structures contributes to accurate scan interpretation. Complications of Meckel's diverticulum are uncommon and pose a diagnostic challenge. Through comprehensive history-taking, physical examination, and nuclear imaging, the diagnosis can be identified, and surgical intervention can be performed to achieve the best possible outcome for the patient.

Background: Lymph node (LN) metastasis is a significant prognostic factor for esophageal squamous cell carcinoma (ESCC), and there are no satisfactory methods for accurately predicting metastatic LNs. The present study aimed to assess the efficacy of 99mTc‐3PRGD2 single‐photon emission computed tomography (SPECT)/computed tomography (CT) for diagnosing metastatic LNs in ESCC. Methods: A total of 15 enrolled patients with ESCC underwent 99mTc‐3PRGD2 SPECT/CT and 18F‐fluorodeoxyglucose positron emission tomography‐computed tomography (18F‐FDG PET/CT) examinations preoperatively. High‐definition bone carving reconstruction technology (HD‐xSPECT Bone) was applied to quantitatively assess the LN's SUVmax via SPECT/CT. The two methods were compared for diagnosing metastatic LNs with pathology as the gold standard. Results: Among 15 patients, 23 metastatic lymph node stations (mLNSs) were predicted by SPECT/CT, with a mean SUVmax of 2.71 ± 1.34, of which 15 were pathologically confirmed; 32 mLNSs were predicted by PET/CT with a mean SUVmax of 4.41 ± 4.02, of which 17 were pathologically confirmed. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of SPECT/CT for diagnosing metastatic LNs were 62.50%, 91.30%, 85.34%, 65.22%, and 90.32%, respectively, and those of PET/CT were 70.83%, 83.70%, 81.03%, 53.13%, and 91.67%, respectively. There was no significant difference in sensitivity (p = 0.061) or specificity (p = 0.058) between the two methods. The AUCSPECT/CT was 0.816 and the SUVmax threshold was 2.5. Conclusion: 99mTc‐3PRGD2 SPECT/CT might be an effective method for diagnosing metastatic LNs in ESCC, especially in combination with HD‐xSPECT Bone. The diagnostic efficiency of this method was noninferior to that of 18F‐FDG PET/CT. The SUVmax threshold of 2.5 showed the highest agreement with the pathology findings. [ABSTRACT FROM AUTHOR]

Background: Deformable registration is required to generate a time‐integrated activity (TIA) map which is essential for voxel‐based dosimetry. The conventional iterative registration algorithm using anatomical images (e.g., computed tomography (CT)) could result in registration errors in functional images (e.g., single photon emission computed tomography (SPECT) or positron emission tomography (PET)). Various deep learning‐based registration tools have been proposed, but studies specifically focused on the registration of serial hybrid images were not found. Purpose: In this study, we introduce CoRX‐NET, a novel unsupervised deep learning network designed for deformable registration of hybrid medical images. The CoRX‐NET structure is based on the Swin‐transformer (ST), allowing for the representation of complex spatial connections in images. Its self‐attention mechanism aids in the effective exchange and integration of information across diverse image regions. To augment the amalgamation of SPECT and CT features, cross‐stitch layers have been integrated into the network. Methods: Two different 177 Lu DOTATATE SPECT/CT datasets were acquired at different medical centers. 22 sets from Seoul National University and 14 sets from Sunway Medical Centre are used for training/internal validation and external validation respectively. The CoRX‐NET architecture builds upon the ST, enabling the modeling of intricate spatial relationships within images. To further enhance the fusion of SPECT and CT features, cross‐stitch layers have been incorporated within the network. The network takes a pair of SPECT/CT images (e.g., fixed and moving images) and generates a deformed SPECT/CT image. The performance of the network was compared with Elastix and TransMorph using L1 loss and structural similarity index measure (SSIM) of CT, SSIM of normalized SPECT, and local normalized cross correlation (LNCC) of SPECT as metrics. The voxel‐wise root mean square errors (RMSE) of TIA were compared among the different methods. Results: The ablation study revealed that cross‐stitch layers improved SPECT/CT registration performance. The cross‐stitch layers notably enhance SSIM (internal validation: 0.9614 vs. 0.9653, external validation: 0.9159 vs. 0.9189) and LNCC of normalized SPECT images (internal validation: 0.7512 vs. 0.7670, external validation: 0.8027 vs. 0.8027). CoRX‐NET with the cross‐stitch layer achieved superior performance metrics compared to Elastix and TransMorph, except for CT SSIM in the external dataset. When qualitatively analyzed for both internal and external validation cases, CoRX‐NET consistently demonstrated superior SPECT registration results. In addition, CoRX‐NET accomplished SPECT/CT image registration in less than 6 s, whereas Elastix required approximately 50 s using the same PC's CPU. When employing CoRX‐NET, it was observed that the voxel‐wise RMSE values for TIA were approximately 27% lower for the kidney and 33% lower for the tumor, compared to when Elastix was used. Conclusion: This study represents a major advancement in achieving precise SPECT/CT registration using an unsupervised deep learning network. It outperforms conventional methods like Elastix and TransMorph, reducing uncertainties in TIA maps for more accurate dose assessments. [ABSTRACT FROM AUTHOR]

Objective: To explore the value of 99mTc-isonitrile deoxyglucosamine (CNDG) SPECT/CT in the staging and resectability diagnosis of non-small cell lung cancer (NSCLC) compared with contrast-enhanced CT (CECT). Methods: This research was approved by the hospital ethics review committee. Sixty-three patients with NSCLC received 99mTc-CNDG SPECT/CT, CECT and initial TNM staging before treatment. Thirty-three patients who underwent radical surgery underwent postoperative pathological TNM staging as the reference standard. Another thirty patients underwent radiochemotherapy; among them, the reference standard of 7 patients of N staging and 5 patients of M staging was based on biopsy pathology, and the diagnosis of the remaining lesions was confirmed by at least one different image or clinical imaging follow-up for more than 3 months. The McNemar test and receiver operating characteristic (ROC) curve analysis were used to compare the diagnostic accuracy of staging and resectability of 99mTc-CNDG SPECT/CT and CECT in NSCLC, respectively. Results: For all patients and surgical patients, the accuracies of 99mTc-CNDG SPECT/CT in diagnosing the T stage and N stage were higher than those of CECT (all patients: 90.5%, 88.9% vs. 79.4%, 60.3%; surgical patients: 81.8%, 78.8% vs. 60.6%, 51.5%), and the differences were statistically significant (all patients: T stage, P = 0.016; N stage, P = 0.000; surgical patients: T stage, P = 0.016; N stage, P = 0.004). For all patients, the accuracy of 99mTc-CNDG SPECT/CT in diagnosing the M stage was higher than that of CECT (96.8% vs. 90.5%), but the difference was not statistically significant (P = 0.289). ROC curve analysis showed that the accuracy of 99mTc-CNDG SPECT/CT in diagnosing the potential resectability of NSCLC was significantly better than that of CECT (P = 0.046). Conclusion: This preliminary clinical study shows that 99mTc-CNDG SPECT/CT is of great value for accurate clinical staging of NSCLC compared with CECT and can significantly improve the accuracy of resectability diagnosis. [ABSTRACT FROM AUTHOR]

Primary: aldosteronism is a frequent cause of secondary hypertension. With access to specialized care, an increasing number of patients with aldosteronism are being identified. Primary aldosteronism is treatable by adrenal surgery if aldosterone excess originates from one of the two, and not from both, adrenals. Bilateral hyperplasia requires lifelong mineralocorticoid receptor antagonist treatment. Up till now, adrenal venous sampling (AVS) has been widely used to distinguish between one-sided and two-sided aldosterone overproduction and patient selection for surgery. AVS is an invasive technique, and the unsuccessful sampling of the right adrenal vein during AVS often prevents side comparison, making the AVS procedure useless. Molecular imaging using [131I]6ß-iodomethyl-19-norcholesterol with SPECT CT imaging (SPECT/CT) may be a potential alternative. Methods: In 42 consecutive patients with confirmed primary aldosteronism, molecular imaging has been performed. After dexamethasone suppression of the non-affected adrenal tissue, 37 MBq [131I]6ß-iodomethyl-19-norcholesterol was injected i.v., and SPECT/CT images were taken 7 days later. Based on the visual evaluation of the images by two nuclear medicine specialists, patients with one-sided tracer accumulation underwent adrenalectomy. To identify a SPECT/CT parameter that best characterizes the side difference, the maximum counts and the mean counts of spherical VOIs were analyzed. Results: Of the 42 patients, 24 had one-sided aldosterone overproduction by SPECT/CT. After surgical removal of the involved adrenal, all 24 patients with SPECT/CT-identified unilateral aldosteronism achieved biochemical cure, defined as a normalized potassium level combined with an aldosterone-to-renin ratio ≤ 30. To identify the best measurable parameter of SPECT/CT side difference, the mean counts and maximum counts of a series of spherical VOIs of different diameters were analyzed. The ratio of the mean counts of 3 cm spherical VOIs of the right and left adrenal regions (lateralization index) was the best discriminator; a ratio of ≥1.29 was characteristic of one-sided disease, without overlap between the one-sided and two-sided patient groups. Conclusions: [131I]6ß-iodomethyl-19-norcholesterol SPECT/CT with a count-based image interpretation and side-ratio calculation may be an equipollent non-invasive substitute for adrenal venous sampling in the lateralization of mineralocorticoid overproduction. It reliably identifies unilateral disease and facilitates patients' selection for surgical intervention. If confirmed by others, this functional imaging may replace AVS when lateralization is required for management decisions in primary aldosteronism. [ABSTRACT FROM AUTHOR]

Aim The imaging of Meckel's diverticulum (MD) is based of accumulation of Tc-99m pertechnetate in the ectopic gastric mucosa (EGM) content. Although the diagnostic accuracy of this imaging modality is high, there are some overlap patients with coexisting gastrointestinal bleeding and false positive causes hampering diagnostic power. The aim of this study was to evaluate the possible contribution of single-photon emission computed tomography/computed tomography (SPECT/CT) in EGM-MD diagnosis and to determine the indication of this additional imaging modality. Materials and Methods Fifty-two pediatric patients (24 girls, 28 boys; mean age: 8.06 ± 5.22 years old) who have suspicion of MD and referred for scintigraphy were evaluated retrospectively. Additional SPECT/CT were performed to selected five cases among the group. The results of the scintigraphy as well as SPECT/CT were compared with endoscopy, pathology, and/or follow-up results. Results There were 9 patients with equivocal study results, 12 positive results, and the others were considered negative MD scintigraphy. One patient was out of follow-up and 10 patients underwent surgery. Only one single patient was negative during surgery but scintigraphy was also negative. The diagnostic sensitivity, specificity, and accuracy were 100, 95, and 96%, respectively. Among five patients with SPECT/CT results one patient was diagnosed by only SPECT/CT who had EGM in duplication cyst, one equivocal patient was diagnosed as descending colon bleeding, and one patient's lesion was clearly delineated by SPECT/CT. Conclusion SPECT/CT has clear advantage over standard planar scintigraphy imaging in EGM-MD determination. This modality might decrease equivocal and false positive results but this issue has to be addressed with further studies. [ABSTRACT FROM AUTHOR]

Purpose: An international survey was conducted by the Cardiovascular Interventional Radiological Society of Europe (CIRSE) to evaluate radioembolization practice and capture opinions on real-world clinical and technical aspects of this therapy. Materials and Methods: A survey with 32 multiple choice questions was sent as an email to CIRSE members between November and December 2022. CIRSE group member and sister societies promoted the survey to their local members. The dataset was cleaned of duplicates and entries with missing data, and the resulting anonymized dataset was analysed. Data were presented using descriptive statistics. Results: The survey was completed by 133 sites, from 30 countries, spanning 6 continents. Most responses were from European centres (87/133, 65%), followed by centres from the Americas (22/133, 17%). Responding sites had been performing radioembolization for 10 years on average and had completed a total of 20,140 procedures over the last 5 years. Hepatocellular carcinoma treatments constituted 56% of this total, colorectal liver metastasis 17% and cholangiocarcinoma 14%. New sites had opened every year for the past 20 years, indicating the high demand for this therapy. Results showed a trend towards individualized treatment, with 79% of responders reporting use of personalized dosimetry for treatment planning and 97% reporting routine assessment of microsphere distribution post-treatment. Interventional radiologists played an important role in referrals, being present in the referring multi-disciplinary team in 91% of responding centres. Conclusion: This survey provides insight into the current state of radioembolization practice globally. The results reveal the increasing significance placed on dosimetry, evolving interventional techniques and increased technology integration. [ABSTRACT FROM AUTHOR]

Performance testing of gamma cameras and single photon computed tomography/computed tomography (SPECT/CT) systems is not subject to regulatory requirements across states and territories in Australia. Internationally recognised testing standards from organisations such as the National Electrical Manufacturers Association (NEMA) describe methodologies for recommended tests. However, variations exist in suggested quality control (QC) schedules from professional bodies such as the Australia and New Zealand Society of Nuclear Medicine (ANZSNM). In this study, a survey was conducted to benchmark current QC programs across a selected sample of eight standalone and networked Australian public hospitals. Vendor-specific flood-field uniformity (intrinsic or extrinsic/system) verification without photomultiplier (PMT) tuning and CT QC were performed at all sites. Weekly and monthly PMT tuning followed by intrinsic flood-field verifications were performed at most sites. At least half of the sites performed monthly centre of rotation (COR) offset verifications. SPECT/CT alignment calibrations and verifications were undertaken by service engineers at all sites, and periodic verifications were performed by local staff at varying frequencies. Variations were observed for other periodic QC tests such as spatial resolution and planar sensitivity. Similarly, variations were observed for tests specific to whole-body systems and SPECT systems. Most sites checked daily and periodic QC results against pass/fail criteria set by vendors. Additional analyses of the QC results, including trend analysis and periodic reviews, were not common practice. The lack of regulatory requirements is likely to have led to variations in QC tests that are generally either harder to perform or are more labour intensive. [ABSTRACT FROM AUTHOR]

Introducing a hybrid imaging approach, such as single-photon emission computerized tomography with X-ray computed tomography (SPECT)/CT, improves diagnostic accuracy and patient management. The ongoing advancement of SPECT hardware and software has resulted in the clinical application of novel approaches. For example, whole-body SPECT/CT (WB-SPECT/CT) studies cover multiple consecutive bed positions, similar to positron emission tomography-computed tomography (PET/CT). WB-SPECT/CT proves to be a helpful tool for evaluating bone metastases (BM), reducing equivocal findings, and enhancing user confidence, displaying effective performance in contrast to planar bone scintigraphy (PBS). Consequently, it is increasingly utilized and might substitute PBS, which leads to new questions and issues concerning the acquisition protocol, patient imaging time, and workflow process. Therefore, this review highlights various aspects of WB-SPECT/CT acquisition protocols that need to be considered to help understand WB-SPECT/CT workflow processes and optimize imaging protocols. [ABSTRACT FROM AUTHOR]

Background: Relapsing Polychondritis(RP) is a rare rheumatic immune disease. As with most diseases, if intervention is delayed, the patient's prognosis is worse. Currently, the diagnostic criteria used in clinical practice do not include CT, PET/CT, SPECT/CT and other new imaging examinations that have developed rapidly in recent years. However, these examinations have some special manifestations for RP, which can help clinicians diagnose RP earlier and distinguish it from other diseases. Case presentation: These five RP patients all had respiratory symptoms such as cough and wheezing as the first symptom, which could not be diagnosed in time according to the previous diagnostic criteria. The clinical data of the five patients are listed in Table 1. The relatively specific manifestations of SPECT/CT examination provided clinicians with very valuable clues to help them advance the diagnosis time. Conclusions: The application of SPECT/CT bone imaging in early diagnosing RP proves to be effective, enabling clinicians to intervene promptly and enhance the overall well-being and quality of life for individuals affected by this condition. [ABSTRACT FROM AUTHOR]

Antibody-drug conjugates (ADCs) are a class of biopharmaceuticals that combine the specificity of monoclonal antibodies (mAbs) with the cytotoxicity of small molecule drugs. 15 ADCs have been approved by regulatory authorities up to now, mainly for indications in oncology, however, this review paper will only focus on the 13 ADCs that have been approved by either the FDA or EMA. ADME (Absorption, Distribution, Metabolism, and Excretion) studies are essential for the development of small molecule drugs to evaluate their disposition properties. These studies help to select drug candidates, determine the optimal dosing regimen and help to identify potential safety concerns for the drug of interest in human. Tissue distribution studies are also important as they facilitate the understanding of the efficacy and safety for parent drug and its metabolites in preclinical and clinical studies. For biologics, ADME studies are usually not required. In this paper, we review the existing approval packages and literature for approved ADCs to determine the extent of ADME studies performed as part of ADC registration packages. We conclude that ADME studies are recommended for the development of ADCs if new linkers and payloads are used that have never been used in humans before as these studies provide valuable information on the pharmacokinetic properties, optimal dosing regimen, and potential safety concerns. However, for the development of ADCs with established linker payload combinations, radiolabelled ADME studies may not be necessary if the distribution, metabolism and excretion properties have been described before. Clinical radiolabelled ADME studies are not recommended where patients are treated for life threating diseases like for indications in oncology. [ABSTRACT FROM AUTHOR]

Introduction: This study aims to evaluate the use of CT-based whole kidney parenchyma (WKP) segmentation in 177Lu-DOTATATE dosimetry. Specifically, it investigates whether WKP volumes change during treatment and evaluates the accuracy of applying a single delineated WKP volume for dosimetry. Furthermore, it aims to determine the cause of WKP volume changes—whether caused by radiation or amino acid infusion—by comparing them with spleen volume changes as a marker for radiation-induced alterations. Methods: SPECT/CT images of 18 patients were acquired over the abdomen approximately 4 h (h) (D0), 24 h (D1), 48 h (D2) and 168 h (D7) post-administration of 177Lu-DOTATATE. CT guided WKP volumes were measured before (baseline) and during treatment. Kidney activity concentrations at each time point were derived from CT-segmented WKP overlaid on SPECT scans. The accuracy of using WKP segmentation from a single CT for all time points was assessed against the gold standard of segmenting each WKP individually. Time-integrated activity calculations were based on a tri-exponential curve fit of the kidney activity concentration over time. Kidney absorbed doses were estimated under the assumption of local energy deposition. Additionally, the impact of various partial volume correction methods on dosimetry was evaluated. Results: Whole-kidney parenchyma (WKP) volumes, ranging from 31 to 243 mL, showed a gradual increase from baseline (mean ± SD = 130.6 ± 46.1 mL) at the initial time points D0 (138.5 ± 44.7 mL) and D1 (139.4 ± 41.6 mL), followed by a slight decrease at D2 (132.8 ± 44.5 mL) and a further decrease at D7 (129.2 ± 42.7 mL). The volume increase at D0 and D1 was statistically significant. Spleen volume did not change during treatment, suggesting that amino acid infusion rather than irradiation effects caused WKP volume changes. Bland-Altman analysis revealed WKP volume biases of 8.77% (D0 vs. BL), 10.77% (D1 vs. BL), 1.10% (D2 vs. BL), and 1.10% (D7 vs. BL), with corresponding uncertainties of 24.4%, 23.6%, 25.4%, and 25.4%, respectively. When WKP segmentation from a single CT is applied across all SPECTs, these WKP volume changes could overestimate the activity concentration and mean absorbed doses up to 4.3% and 2.5%, respectively. The absorbed dose uncertainties using a recovery coefficient (RC) of 0.85 for single-time-point WKP delineation increase the absorbed dose uncertainty by 4% compared to the use of patient-specific RCs and time specific segmentation of WKP volumes. Conclusions: Kidney volume exhibited significant variation form D0 to D7, affecting the precision of dosimetry calculation, primarily due to errors in whole-kidney parenchyma (WKP) delineation. Notably, using WKP segmentation from a single CT scan applied to sequential SPECT images introduce further uncertainty and may lead to an overestimation of the absorbed dose. The fluctuations in kidney volume are most likely attributable to amino acid infusion. [ABSTRACT FROM AUTHOR]

Background: The application of semi-conductor detectors such as cadmium–zinc–telluride (CZT) in nuclear medicine improves extrinsic energy resolution and count sensitivity due to the direct conversion of gamma photons into electric signals. A 3D-ring pixelated CZT system named StarGuide was recently developed and implemented by GE HealthCare for SPECT acquisition. The system consists of 12 detector columns with seven modules of 16 × 16 CZT pixelated crystals, each with an integrated parallel-hole tungsten collimator. The axial coverage is 27.5 cm. The detector thickness is 7.25 mm, which allows acquisitions in the energy range [40–279] keV. Since there is currently no performance characterization specific to 3D-ring CZT SPECT systems, the National Electrical Manufacturers Association (NEMA) NU 1-2018 clinical standard can be tailored to these cameras. The aim of this study was to evaluate the performance of the SPECT/CT StarGuide system according to the NEMA NU 1-2018 clinical standard specifically adapted to characterize the new 3D-ring CZT. Results: Due to the integrated collimator, the system geometry and the pixelated nature of the detector, some NEMA tests have been adapted to the features of the system. The extrinsic measured energy resolution was about 5–6% for the tested isotopes (99mTc, 123I and 57Co); the maximum count rate was 760 kcps and the observed count rate at 20% loss was 917 kcps. The system spatial resolution in air extrapolated at 10 cm with 99mTc was 7.2 mm, while the SPECT spatial resolutions with scatter were 4.2, 3.7 and 3.6 mm in a central, radial and tangential direction respectively. Single head sensitivity value for 99mTc was 97 cps/MBq; with 12 detector columns, the system volumetric sensitivity reached 520 kcps MBq−1 cc−1. Conclusions: The performance tests of the StarGuide can be performed according to the NEMA NU 1-2018 standard with some adaptations. The system has shown promising results, particularly in terms of energy resolution, spatial resolution and volumetric sensitivity, potentially leading to higher quality clinical images. [ABSTRACT FROM AUTHOR]

Purpose: Lutetium-177 [177Lu]Lu-PSMA-617 radioligand therapy (RLT) represents a significant advancement for metastatic castration-resistant prostate cancer (mCRPC), demonstrating improvements in radiographic progression free survival (rPFS) and overall survival (OS) with a low rate of associated side effects. Currently, most post-therapy SPECT/CT is conducted at 24 h after infusion. This study examines the clinical utility of a next-generation multi-detector Cadmium-Zinc-Telluride (CZT) SPECT/CT system (StarGuide) in same-day post-infusion assessment and early treatment response to [177Lu]Lu-PSMA-617. Methods: In this retrospective study, 68 men with progressive mCRPC treated with [177Lu]Lu-PSMA-617 at our center from June 2022 to June 2023 were evaluated. Digital whole-body SPECT/CT imaging was performed after [177Lu]Lu-PSMA-617infusion (mean ± SD: 1.8 ± 0.6 h, range 1.1–4.9 h). Quantitative analysis of [177Lu]Lu-PSMA-617 positive lesions was performed in patients who underwent at least 2 post-therapy SPECT/CT, using liver parenchyma uptake as reference. Metrics including [177Lu]Lu-PSMA-617 positive total tumor volume (Lu-TTV), SUVmax and SUVmean were calculated. These quantitative metrics on post-infusion SPECT/CT images after cycles 1, 2 and 3 were correlated with overall survival (OS), prostate specific antigen-progression free survival (PSA-PFS) as defined by prostate cancer working group 3 (PCWG3), and PSA decrease over 50% (PSA50) response rates. Results: 56 patients (means age 76.2 ± 8.1 years, range: 60–93) who underwent at least 2 post-therapy SPECT/CT were included in the image analysis. The whole-body SPECT/CT scans (~ 12 min per scan) were well tolerated, with 221 same-day scans performed (89%). At a median of 10-months follow-up, 33 (58.9%) patients achieved PSA50 after [177Lu]Lu-PSMA-617 treatment and median PSA-PFS was 5.0 months (range: 1.0–15 months) while median OS was not reached. Quantitative analysis of SPECT/CT images showed that 37 patients (66%) had > 30% reduction in Lu-TTV, associated with significantly improved overall survival (median not reached vs. 6 months, P = 0.008) and PSA-PFS (median 6 months vs. 1 months, P < 0.001). However, changes in SUVmax or SUVmean did not correlate with PSA-PFS or OS. Conclusion: We successfully implemented same-day post-therapy SPECT/CT after [177Lu]Lu-PSMA-617 infusions. Quantitation of 1–2 h post-therapy SPECT/CT images is a promising method for assessing treatment response. However, the approach is currently limited by its suboptimal detection of small tumor lesions and the necessity of incorporating a third-cycle SPECT/CT to mitigate the effects of any potential treatment-related flare-up. Further investigation in a larger patient cohort and prospective validation is essential to confirm these findings and to explore the role of SPECT/CT as a potential adjunct to PSMA PET/CT in managing mCRPC. [ABSTRACT FROM AUTHOR]

Background: Parathyroid scan is an important imaging modality for localizing hyperfunctioning parathyroid tissue in patients with hyperparathyroidism. Unfortunately, whether early or delayed timing is the optimal protocol for [99mTc]Tc-MIBI SPECT/CT parathyroid remains under debate. This study aimed to evaluate the agreement and compare the confidence levels of physicians when interpreting early and delayed [99mTc]Tc-MIBI SPECT/CT parathyroid scans. Additionally, it sought to identify clinical factors that related to positive scan result. We conducted a prospective study where the early and delayed [99mTc]Tc-MIBI SPECT/CT was separately interpreted as either positive or negative. Furthermore, these interpretations were categorized based on whether they fell within more or less confidence levels of the readers and were correlated with clinical information. Results: We enrolled 39 patients with hyperparathyroidism with 158 possible locations of parathyroid glands. The per-location agreement between the early and delayed scans was moderate (concordant rate: 80.3%, Kappa = 0.558), and the per-patient agreement was slight (concordant rate: 71.8%, Kappa = 0.093). The confidence of interpretation was significantly higher for the delayed scans. Calcium supplementation, low serum parathyroid hormone levels, and low serum phosphate levels were associated with positive early scans. High calcium level and high parathyroid hormone levels were associated with positive delayed scans. Conclusions: Our study highlights the impact of the timing of SPECT/CT in [99mTc]Tc-MIBI parathyroid scans. The different confidence levels between early and delayed scans, along with clinical factors, imply that various factors affect parathyroid scan interpretation, and individualized scanning protocols adjusted for specific settings may be needed to optimize the successful localization of hyperfunctioning parathyroid tissue. [ABSTRACT FROM AUTHOR]

Perforation of the bowel can be a life-threatening condition and is usually clinically diagnosed when a patient presents with such features as severe abdominal pain, tenderness, and tachycardia. Bowel perforation may be corroborated by various conventional imaging modalities, including X-ray, ultrasonography, computed tomography, and magnetic resonance imaging. Nuclear medicine imaging modalities seldom have a role to play in these settings. Rarely diagnosis of perforation may be missed if it is concealed and does not present with the usual signs. Mostly the perforation will eventually be diagnosed if they develop signs and symptoms and is taken up for an exploratory laparotomy. A delay in diagnosis can later lead to significant patient morbidity or even mortality. This report describes a case where possible intestinal perforation was suspected on a 99mTc-DTPA renogram in a postoperative patient with significant urine leak, the presence of which was confirmed intraoperatively. To our knowledge, this was the first such case in the literature. [ABSTRACT FROM AUTHOR]

With the development of PD-1/PD-L1 immune checkpoint inhibitor therapy, the ability to monitor PD-L1 expression in the tumor microenvironment is important for guiding therapy. This study was performed to develop a novel radiotracer with optimal pharmacokinetic properties to reflect PD-L1 expression in vivo via single-photon emission computed tomography (SPECT) imaging. [99mTc]Tc-HYNIC-WL12-tricine/M (M = TPPTS, PDA, ISONIC, 4-PSA) complexes with high radiochemical purity (>97%) and suitable molar activity (from 100.5 GBq/μmol to 300 GBq/μmol) were prepared through a kit preparation process. All 99mTc-labeled HYNIC-WL12 radiotracers displayed good in vitro stability for 4 h. The affinity and specificity of the four radiotracers for PD-L1 were demonstrated both in vitro and in vivo. The results of biodistribution studies displayed that the pharmacokinetics of the 99mTc-HYNIC-conjugated radiotracers were significantly influenced by the coligands of the radiotracers. Among them, [99mTc]Tc-HYNIC-WL12-tricine/ISONIC exhibited the optimal pharmacokinetic properties (t1/2α = 8.55 min, t1/2β = 54.05 min), including the fastest clearance in nontarget tissues, highest tumor-to-background contrast (e.g., tumor-to-muscle ratio, tumor-to-blood ratio: 40.42 ± 1.59, 14.72 ± 2.77 at 4 h p.i., respectively), and the lowest estimated radiation absorbed dose, highlighting its potential as a clinical SPECT imaging probe for tumor PD-L1 detection. [ABSTRACT FROM AUTHOR]

Single photon emission tomography/computed tomography (SPECT/CT) is a mature imaging technology with a dynamic role in the diagnosis and monitoring of a wide array of diseases. This paper reviews the technological advances, clinical impact, and future directions of SPECT and SPECT/CT imaging. The focus of this review is on signal amplifier devices, detector materials, camera head and collimator designs, image reconstruction techniques, and quantitative methods. Bulky photomultiplier tubes (PMTs) are being replaced by position-sensitive PMTs (PSPMTs), avalanche photodiodes (APDs), and silicon PMs to achieve higher detection efficiency and improved energy resolution and spatial resolution. Most recently, new SPECT cameras have been designed for cardiac imaging. The new design involves using specialised collimators in conjunction with conventional sodium iodide detectors (NaI(Tl)) or an L-shaped camera head, which utilises semiconductor detector materials such as CdZnTe (CZT: cadmium–zinc–telluride). The clinical benefits of the new design include shorter scanning times, improved image quality, enhanced patient comfort, reduced claustrophobic effects, and decreased overall size, particularly in specialised clinical centres. These noticeable improvements are also attributed to the implementation of resolution-recovery iterative reconstructions. Immense efforts have been made to establish SPECT and SPECT/CT imaging as quantitative tools by incorporating camera-specific modelling. Moreover, this review includes clinical examples in oncology, neurology, cardiology, musculoskeletal, and infection, demonstrating the impact of these advancements on clinical practice in radiology and molecular imaging departments. [ABSTRACT FROM AUTHOR]

False positive radioiodine uptake may pose difficulties in diagnosis and subsequent management of thyroid cancer. Combined imaging techniques, such as SPECT/CT, play a crucial role in accurately identifying the specific location of radioiodine uptake, thereby avoiding potential diagnostic error. This is particularly important in situations where unexpected uptake could lead to unnecessary treatment interventions such as surgery or radioiodine treatment. In this study, we discuss a case involving a 38-year-old female with a history of thyroid cancer and I-131 treatment. Approximately six years later, her course was complicated by left sided epiphora leading to dacryocystorhinostomy and subsequently elevation of thyroglobulin (Tg) levels prompting retreatment by radioiodine. The post-therapy whole-body scan revealed false-positive radioiodine uptake on the left side of the skull, conclusively confirmed through SPECT/CT imaging to be localized in the patient's left eye. [ABSTRACT FROM AUTHOR]

De novo metastatic prostate cancer with neuroendocrine differentiation (NED) at first presentation is extremely rare. A 65-year-old man (Gleason score 5+4, first assumed to be acinar adenocarcinoma), was referred for [99mTc]Tc-HYNIC-PSMA SPECT/CT due to low back pain. The PSA levels were 8 and <0.07 ng/mL at the time of diagnosis and prior to scintigraphy respectively. The scan revealed multiple non-PSMA-avid lesions throughout the skeleton, lung and liver, suggesting the possibility of NED or 2nd malignancy. Second-look and review of the pathology led to change of the diagnosis to mixed small cell neuroendocrine carcinoma-acinar adenocarcinoma. This case highlights the importance of PSMA imaging in suggestion of type of the tumor, which as in our case, might alter the pathologic tissue diagnosis. [ABSTRACT FROM AUTHOR]

We presented a 2.5-year-old boy with a history of the left pulmonary hypoplasia, repaired congenital diaphragmatic hernia and multiple episodes of pyelonephritis was referred to our department for [99mTc]Tc-DMSA and [99mTc]Tc-EC renal scintigraphy. The scans revealed an unusual pattern of renal uptake with horizontally aligned kidneys located high on left lower thoracic region extended to the mid abdomen. SPECT/CT of the [99mTc]Tc-DMSA scan clearly demonstrated the unusual location of the kidneys which was due to crossed fused renal ectopia and elevated diaphragm. Diuretic renal scans showed no evidence of renal obstruction. Additionally, the VCUG scan indicated vesicoureteral reflux in both ureters. [ABSTRACT FROM AUTHOR]

Introduction: Myocardial perfusion imaging (MPI) faces a challenge in diagnostic accuracy due to gastric wall uptake (GWU). Previous studies have linked GWU to proton pump inhibitors (PPIs) intake, but only a minority of patients on PPIs show activity accumulation. Our study aimed to investigate the influence of PPIs on GWU in MPI by single photon emission computed tomography (SPECT) and assess the necessity or benefits of discontinuing PPIs before the procedure. Methods: The 368 patients who underwent a two-day stress/rest [99mTc]Tc-MIBI SPECT/CT MPI were divided into three groups: (i) Control group (n=114, without the consumption of any gastroprotective medication), (ii) continued medication(n=48, on PPI treatment) and (iii) discontinued medication (n=206, PPI discontinued for one day or more before MPI). Rest SPECT images were analysed for clinically relevant GWU. Results: Based on our study, out of 114 patients in group (i),16 individuals (14%), and 10 patients from 48 patients in group (ii) (20.8%) demonstrated radioactivity accumulation in the gastric wall. In group (iii), despite discontinuing PPIs use, 20.3% of patients showed GWU. Statistical analysis of these three groups and their subgroups did not show any significant difference in terms of gastric wall uptake of [99mTc]Tc-MIBI in MPI. Conclusion: Concisely, our study found no significant link between PPI use and gastric wall activity in MPI. Further data is needed before adjusting drug guidelines in nuclear medicine centers. Multicenter studies with larger patient cohorts must explore the PPI-GWU relationship, utilizing SPECT/CT scans for precise interference location determination. [ABSTRACT FROM AUTHOR]

A 73-year-old male with left hip prosthesis infection performed a 99mTc HMPAO–labelled autologous WBC (WBC) scan to evaluate the response to antibiotic therapy. Since the early planar scan, an area of increased activity was visible extending from the left groin region to the ipsilateral flank. At late planar images, the area progressively focused in the left groin, site of a painful inguinal hernia. The contextual tomographic acquisition showed increased activity partly referable to non-specific intestinal contents and partly localized at the parietal wall of the herniated intestinal loop. Our case suggests that the incidental detection of increased accumulation of WBC in correspondence of the intestinal wall of an inguinal hernia may indicate inflammatory involvement and subsequent further complications. [ABSTRACT FROM AUTHOR]

Background: In patients with advanced breast cancer (BC), distant metastases happen mainly in the skeleton. This study aimed to investigate the role of 99mTc-MDP SPECT/CT in the differential diagnosis of malignant bone lesions from degenerative benign bone diseases in female BC patients. Methods and Results: The study included 39 female BC patients who underwent a baseline 99mTc-MDP SPECT/CT bone scans. After lesion detection, a quantitative radiotracer uptake analysis was conducted, and the standardized uptake value (SUVmax) was identified in each patient, and the data were then statistically analyzed. SUVmax values were significantly higher in BC patients with malignant metastasis than in patients with degenerative changes (33.04±15.3 vs. 13.25±5.46 g/mL, P

Abstract Background Personalised multi-compartment dosimetry based on [99mTc]Tc-MAA is a valuable tool for planning 90Y radioembolization treatments. The establishment and effective application of dose–effect relationships in yttrium-90 (90Y) radioembolization requires [99mTc]Tc-MAA SPECT quantification ideally independent of clinical site. The purpose of this multi-centre phantom study was to evaluate inter-site variability of [99mTc]Tc-MAA imaging and evaluate a standardised imaging protocol. Data was obtained from the TARGET study, an international, retrospective multi-centre study including 14 sites across 8 countries. The impact of imaging related factors was estimated using a NEMA IQ phantom (representing the liver), and a uniformly filled cylindrical phantom (representing the lungs). Imaging was performed using site-specific protocols and a standardized protocol. In addition, the impact of implementing key image corrections (scatter and attenuation correction) in the site-specific protocols was investigated. Inter-site dosimetry accuracy was evaluated by comparing computed Lung Shunt Fraction (LSF) measured using planar imaging of the cylindrical and NEMA phantom, and contrast recovery coefficient (CRC) measured using SPECT imaging of the NEMA IQ phantom. Results Regarding the LSF, inter-site variation with planar site-specific protocols was minimal, as determined by comparing computed LSF between sites (interquartile range 9.6–10.1%). A standardised protocol did not improve variation (interquartile range 8.4–9.0%) but did improve mean accuracy compared to the site-specific protocols (5.0% error for standardised protocol vs 8.8% error for site-specific protocols). Regarding the CRC, inter-system variation was notable for site-specific SPECT protocols and could not be improved by the standardised protocol (CRC interquartile range for 37 mm sphere 0.5–0.7 and 0.6–0.8 respectively), however the standardised protocol did improve accuracy of sphere:background determination. Implementation of key image corrections did improve inter-site variation (CRC interquartile range for 37 mm sphere 0.6–0.7). Conclusion Eliminating sources of variability in image corrections between imaging protocols reduces inter-site variation in quantification. A standardised protocol was not able to improve consistency of LSF or CRC but was able to improve accuracy.

Abstract Background A new, alternative option for patients with recurrent glioblastoma is targeted alpha therapy (TAT), in the form of a local administration of substance P (neurokinin type 1 receptor ligand, NK-1) labelled with 225Ac. The purpose of the study was to confirm the feasibility of quantitative SPECT imaging of 225Ac, in a model reproducing specific conditions of TAT. In particular, to present the SPECT calibration methodology used, as well as the results of validation measurements and their accuracy. Additionally, to discuss the specific problems related to high noise in the presented case. Materials and methods All SPECT/CT scans were conducted using the Symbia T6 equipped with HE collimators, and acquired with multiple energy windows (three main windows: 440 keV, 218 keV, and 78 keV, with three lower scatter energy windows). A Jaszczak phantom with fillable cylindrical sources of various sizes was used to investigate quantitative SPECT/CT imaging characteristics. The planar sensitivity of the camera, an imaging calibration factor, and recovery coefficients were determined. Additionally, the 3D printed model of the glioblastoma tumour was developed and imaged to evaluate the accuracy of the proposed protocol. Results Using the imaging calibration factor and recovery coefficients obtained with the Jaszczak phantom, we were able to quantify the activity in a 3D-printed model of a glioblastoma tumour with uncertainty of no more than 10% and satisfying accuracy. Conclusions It is feasible to perform quantitative 225Ac SPECT/CT imaging. However, there are still many more challenges that should be considered for further research on this topic (among others: accurate determination of ICF in the case of high background noise, better method of background estimation for recovery coefficient calculations, other methods for scatter correction than the dual-energy window scatter-compensation method used in this study).

Abstract Background PSMA PET/CT is the most sensitive molecular imaging modality for prostate cancer (PCa), yet much of the developing world has little or no access to PET/CT. [99mTc]Tc-PSMA scintigraphy (PS) is a cheaper and more accessible gamma camera-based alternative. However, many resource-constrained departments have only a single camera without tomographic or hybrid imaging functionality, and camera time is frequently in high demand. Simplifying imaging protocols by limiting the field of view (FOV) and omitting SPECT/CT or even SPECT may provide a partial solution. The aim was thus to determine the adequacy of PS planar-only and/or SPECT-only imaging protocols with a limited FOV. Methods The scans of 95 patients with histologically proven PCa who underwent PS with full-body planar and multi-FOV SPECT/CT were reviewed. The detection rates for uptake in the prostate gland/bed and in metastases were compared on planar, SPECT, and SPECT/CT. The agreement between modalities was calculated for the detection of metastases and for staging. The impact of imaging a limited FOV was determined. Results Pathological prostatic uptake was seen in all cases on SPECT/CT (excluding two post-prostatectomy patients), 90.3% of cases on SPECT, and 15.1% on planar images (p

Abstract Background The administration of a 166Ho scout dose is available as an alternative to 99mTc particles for pre-treatment imaging in Selective Internal Radiation Therapy (SIRT). It has been reported that the 166Ho scout dose may be more accurate for the prediction of microsphere distribution and the associated therapy planning. The aim of the current study is to compare the scintigraphic imaging characteristics of both isotopes, considering the objectives of the pre-treatment imaging using clinically geared phantoms. Methods Planar and SPECT/CT images were obtained using a NEMA image quality phantom in different phantom setups and another body-shaped phantom with several inserts. The influence of collimator type, count statistics, dead time effects, isotope properties and patient obesity on spatial resolution, contrast recovery and the detectability of small activity accumulations was investigated. Furthermore, the effects of the imaging characteristics on personalized dosimetry are discussed. Results The images with 99mTc showed up to 3 mm better spatial resolution, up to two times higher contrast recovery and significantly lower image noise than those with 166Ho. The contrast-to-noise ratio was up to five times higher for 99mTc than for 166Ho. Only when using 99mTc all activity-filled spheres could be distinguished from the activity-filled background. The measurements mimicking an obese patient resulted in a degraded image quality for both isotopes. Conclusions Our measurements demonstrate better scintigraphic imaging properties for 99mTc compared to 166Ho in terms of spatial resolution, contrast recovery, image noise, and lesion detectability. While the 166Ho scout dose promises better prediction of the microsphere distribution, it is important to consider the inferior imaging characteristics of 166Ho, which may affect individualized treatment planning in SIRT.