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Purpose Tendency is to moderate the injected activity and/or reduce acquisition time in PET examinations to minimize potential radiation hazards and increase patient comfort. This work aims to assess the performance of regular full-dose (FD) synthesis from fast/low-dose (LD) whole-body (WB) PET images using deep learning techniques. Methods Instead of using synthetic LD scans, two separate clinical WB 18F-Fluorodeoxyglucose (18F-FDG) PET/CT studies of 100 patients were acquired: one regular FD (~ 27 min) and one fast or LD (~ 3 min) consisting of 1/8th of the standard acquisition time. A modified cycle-consistent generative adversarial network (CycleGAN) and residual neural network (ResNET) models, denoted as CGAN and RNET, respectively, were implemented to predict FD PET images. The quality of the predicted PET images was assessed by two nuclear medicine physicians. Moreover, the diagnostic quality of the predicted PET images was evaluated using a pass/fail scheme for lesion detectability task. Quantitative analysis using established metrics including standardized uptake value (SUV) bias was performed for the liver, left/right lung, brain, and 400 malignant lesions from the test and evaluation datasets. Results CGAN scored 4.92 and 3.88 (out of 5) (adequate to good) for brain and neck + trunk, respectively. The average SUV bias calculated over normal tissues was 3.39 ± 0.71% and − 3.83 ± 1.25% for CGAN and RNET, respectively. Bland-Altman analysis reported the lowest SUV bias (0.01%) and 95% confidence interval of − 0.36, + 0.47 for CGAN compared with the reference FD images for malignant lesions. Conclusion CycleGAN is able to synthesize clinical FD WB PET images from LD images with 1/8th of standard injected activity or acquisition time. The predicted FD images present almost similar performance in terms of lesion detectability, qualitative scores, and quantification bias and variance.

This work sets out to investigate the performance of full-dose (FD) PET prediction from fast or low-dose (LD) whole-body (WB) PET scans using convolutional neural networks. One hundred patients who underwent WB PET/CT examinations were retrospectively used to develop LD to FD PET conversion models. The patients underwent two separate WB examinations lasting ~27 min (regular scan) and ~3 min (fast or LD scan) acquisition times. The fast (3 min) WB PET examinations are equivalent to 1/8th of the full-dose PET scan. A residual neural network (ResNet) and a modified cycle-consistent generative adversarial network (CycleGAN) architecture were employed to model the LD to FD PET conversion. The quality of synthetic PET images produced by ResNet and CycleGAN models, referred to as RNET and CGAN, respectively, were evaluated by two nuclear medicine physicians using a five-point scoring. Quantitative metrics, including structural similarity index (SSIM), peak signal-to-noise ratio (PSNR), mean square error (MSE) and standardized uptake value (SUV) bias were calculated within the left/right lung, brain, liver, and one hundred hot spots (malignant lesions) in PET images predicted using CGAN and RNET models. The physicians assigned scores of 3.88 and 4.92 (out of 5) to the CGAN-predicted FD PET images for the neck & trunk and brain regions, respectively. Considering the PSNR and SSIM metrics, the CGAN model exhibited superior performance with PSNR=39.08±3.56 and SSIM=0.97±0.02 compared to the RNET model with PSNR=34.91±1.50 and SSIM=0.93±0.04. Overall, the CGAN model outperformed the RNET model exhibiting lower SUV bias and higher image quality in the predicted FD PET images.

Purpose: To assess the performance of full dose (FD) positron emission tomography (PET) image synthesis in both image and projection space from low-dose (LD) PET images/sinograms without sacrificing diagnostic quality using deep learning techniques. Methods: Clinical brain PET/CT studies of 140 patients were retrospectively employed for LD to FD PET conversion. 5% of the events were randomly selected from the FD list-mode PET data to simulate a realistic LD acquisition. A modified 3D U-Net model was implemented to predict FD sinograms in the projection-space (PSS) and FD images in image-space (PIS) from their corresponding LD sinograms/images, respectively. The quality of the predicted PET images was assessed by two nuclear medicine specialists using a five-point grading scheme. Quantitative analysis using established metrics including the peak signal-to-noise ratio (PSNR), structural similarity index metric (SSIM), region-wise standardized uptake value (SUV) bias, as well as first-, second- and high-order texture radiomic features in 83 brain regions for the test and evaluation dataset was also performed. Results: All PSS images were scored 4 or higher (good to excellent) by the nuclear medicine specialists. PSNR and SSIM values of 0.96 ± 0.03, 0.97 ± 0.02 and 31.70 ± 0.75, 37.30 ± 0.71 were obtained for PIS and PSS, respectively. The average SUV bias calculated over all brain regions was 0.24 ± 0.96% and 1.05 ± 1.44% for PSS and PIS, respectively. The Bland-Altman plots reported the lowest SUV bias (0.02) and variance (95% CI: -0.92, +0.84) for PSS compared with the reference FD images. The relative error of the homogeneity radiomic feature belonging to the Grey Level Co-occurrence Matrix category was -1.07 ± 1.77 and 0.28 ± 1.4 for PIS and PSS, respectively Conclusion: The qualitative assessment and quantitative analysis demonstrated that the FD PET prediction in projection space led to superior performance, resulting in higher image quality and lower SUV bias and variance compared to FD PET prediction in the image domain.

Purpose Tumor hypoxia is associated with radioresistance and poor prognosis after radiation therapy for prostate cancer (PCa). In this prospective pilot study, we assessed the ability of 18F-misonidazole (18F-MISO) positron emission tomography (PET)–magnetic resonance imaging (MRI) to detect hypoxia in high-grade PCa patients who were candidates for curative radiation therapy, and we evaluated 18F-MISO PET-MRI modulation after 3 months of neoadjuvant androgen deprivation therapy (nADT). Methods and Materials Eleven PCa patients with a Gleason score (GS) ≥ 8 underwent 18F-fluorocholine (18F-FCH) PET–computed tomography at diagnosis and an 18F-MISO hybrid PET-MRI examination before nADT; a second 18F-MISO PET-MRI examination was acquired after 3 months of nADT for all patients but one who dropped out because of noncompliance with nADT. Immunohistochemistry for tissue hypoxia- and proliferation-related biomarkers (glucose transporter 1, carbonic anhydrase IX, vascular endothelial growth factor A, Ki-67, hypoxia-inducible factor 1 alpha, and epidermal growth factor receptor) was performed in lesions bearing the highest GS. We used nonparametric tests to assess (1) the presence of 18F-MISO–positive regions (tumor-to-background ratio [TBR] ≥ 1.4) at baseline; (2) the correlation between imaging parameters (PET tracer uptake, Prostate Imaging Reporting and Data System [PIRADS] scores, and dynamic contrast enhancement perfusion markers) at baseline; (3) the difference in immunohistochemistry staining between 18F-MISO–positive and –negative lesions; and (4) the changes in 18F-MISO PET-MRI after nADT. Results Uptake of 18F-MISO was significant in 7 patients, being coincidental with the highest GS region in 5 of them. A significant correlation was found at baseline between GS and 18F-MISO TBR, between 18F-MISO TBR and MRI perfusion markers, between GS and 18F-FCH maximum standardized uptake value, between GS and PIRADS score, and between 18F-FCH maximum standardized uptake value and PIRADS score. No difference was found between 18F-MISO–positive and –negative biopsy specimens with respect to tissue biomarkers. The TBR of 18F-MISO diminished significantly after nADT only in high-grade lesions and in regions with a significant uptake at baseline. Conclusions PET imaging with 18F-MISO showed variable uptake in PCa, associated with a higher GS, lowering significantly after 3 months of nADT in high-grade lesions. These results suggest the existence of a hypoxic microenvironment in PCa and a reoxygenation effect of nADT.

Parathyroid adenoma within or adjacent to the vagus nerve is a rare ectopia, with only 21 cases reported in the literature [1,2,3]. A plausible explanation described by Gilmour in 1937 is that parathyroid elements, destined for the inferior parathyroid glands, may segregate and attach to the nerve during embryogenesis [4, 5].

Resume Les depots extracellulaires de peptides beta-amyloides constituent une des lesions histologiques necessaires pour le diagnostic neuropathologique de la maladie d’Alzheimer. Pendant la derniere decennie, plusieurs traceurs PET ont ete valides et ont maintenant une autorisation de mise sur le marche pour visualiser les plaques amyloides in vivo, avec des sensibilite et specificite excellentes. L’objectif de cet article est de fournir un guide pratique a la lecture et a l’interpretation de ces images, ainsi que de decrire les perspectives de developpement plus recentes ouvertes par cette modalite pour son integration dans le processus diagnostique et la prise en charge des patients.

To evaluate the diagnostic performance of a whole-body 18F-choline (FCH) hybrid PET/MRI for prostate cancer patients at biochemical relapse after radical prostatectomy (RP) compared to pelvic multiparametric MRI (mpMRI), one of the standard imaging modality for this patient population. From 2010 to 2016, 58 whole-body FCH PET/MRI studies with mpMRI acquisitions were performed in 53 prostate cancer patients relapsing after curative RP. Median PSA and PSA doubling time (PSA DT) at PET study were 1.5 ng/ml and 6.5 months, respectively. The overall positivity rate of FCH PET/MRI was 58.6% (n = 34), dropping to 44% in patients with a PSA ≤ 2 ng/ml (n = 36). Median PSA values in positive and negative PET/MRI studies were 2.2 ng/ml and 0.8 ng/ml, respectively, with no differences in PSA DT (6.5 vs. 6.6 months). A PSA value ≥ 1.5 ng/ml was a significant predictor of positivity on PET/MRI studies. Compared to PET, mpMRI identified more local relapses (17 vs. 14, p = 0.453) while PET outperformed whole-body Dixon MRI for regional (16 vs. 9, p = 0.016) and distant (12 vs. 6, p = 0.031) metastases. Compared to pelvic mpMRI, the treatment approach turned out to be influenced more frequently using whole-body FCH hybrid PET/MRI studies (58.6% vs. 38%). In prostate cancer patients with biochemical recurrence after RP, whole-body FCH PET/MRI achieved a higher detection rate of nodal/distant metastases compared to pelvic mpMRI alone, increasing the change of treatment strategy by more than 20%.

PET/MRI tomographs represent the latest development in hybrid molecular imaging, opening new perspectives for clinical and research applications and attracting a large interest among the medical community. This new hybrid modality is expected to play a pivotal role in a number of clinical applications and among these the assessment of neurodegenerative disorders. PET and MRI, acquired separately, are already the imaging biomarkers of choice for a comprehensive assessment of the changes occurring in dementias (major cognitive disorders) as well as in their prodromal phase. In this paper we review the current evidence on the use of integrated PET/MRI scanners to investigate patients with neurodegenerative conditions, and in particular major neurocognitive disorders. The number of studies performed is still limited and shows that the use of PET/MRI gives results overall comparable to PET/CT and MRI acquired independently. We also address the challenges for quantitative aspects in PET/MRI, namely attenuation, partial volume and motion correction and the use of semi-quantitative approaches for FDG PET image analysis in this framework. The recent development of PET tracers for the in vivo differential diagnosis of dementias, able to visualize amyloid and tau deposits, suggests that in the future PET/MRI might represent the investigation of choice for a single session evaluation of morphological, functional and molecular markers.

This chapter will summarize the evidence supporting the clinical use of FDG-PET brain imaging in the evaluation of patients with pharmaco-resistant epilepsy considered for surgical treatment. We will discuss the clinical indications, the main patterns of hypometabolism observed, and the main advantages and limitations associated with its use.

To compare the diagnostic performance of 18-FDG-PET/MR and PET/CT for the N- and M- staging of breast cancer. Two independent readers blinded to clinical/follow-up data reviewed PET/MR and PET/CT examinations performed for initial or recurrent breast cancer staging in 80 consecutive patients (mean age = 48 ± 12.9 years). The diagnostic confidence for lesions in the contralateral breast, axillary/internal mammary nodes, bones and other distant sites were recorded. Sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated. The standard of reference included pathology and/or follow-up > 12 months. Nine of 80 patients had bone metastases; 13/80 had other distant metastases, 44/80 had axillary, 9/80 had internal mammary and 3/80 had contralateral breast tumours. Inter-reader agreement for lesions was excellent (weighted kappa = 0.833 for PET/CT and 0.823 for PET/MR) with similar reader confidence for the two tests (ICC = 0.875). In the patient-per-patient analysis, sensitivity and specificity of PET/MRI and PET/CT were similar (p > 0.05). In the lesion-per-lesion analysis, the sensitivity of PET/MR and PET/CT for bone metastases, other metastases, axillary and internal mammary nodes, contralateral tumours and all lesions together was 0.924 and 0.6923 (p = 0.0034), 0.923 and 0.923 (p = 1), 0.854 and 0.812 (p = 0.157), 0.9 and 0.9 (p = 1), 1 and 0.25 (p = 0.083), and 0.89 and 0.77 (p = 0.0013) respectively. The corresponding specificity was 0.953 and 1 (p = 0.0081), 1 and 1 (p = 1), 0.893 and 0.92 (p = 0.257), 1 and 1 (p = 1), 0.987 and 0.99 (p = 1) and 0.96 and 0.98 (p = 0.0075) respectively. Reader confidence, inter-reader agreement and diagnostic performance per patient were similar with PET/MR and PET/CT. However, for all lesions together, PET/MR had a superior sensitivity and lower specificity in the lesion-per-lesion analysis. • N and M breast cancer staging performance of PET/MR and PET/CT is similar per patient. • In a lesion-per-lesion analysis PET/MR is more sensitive than PET/CT especially for bone metastasis. • Readers’ diagnostic confidence is similar for both tests.

The development and validation of molecular imaging markers for the neuropathological hallmarks of neurodegenerative diseases associated with cognitive impairment is a reality since two decades. Amyloid PET tracers have been validated analytically and are currently tested for their clinical utility. More recently tracers targeting specifically tau deposits have been developed and are currently tested in large clinical studies. The availability of these markers opens the possibility for precision medicine in a field that was limited by a gold standard diagnosis occurring only postmortem. Aim of this review is to summarize the main findings obtained using tau-specific PET tracers in clinical cohorts of patients with cognitive impairment. We report the results of a systematic literature review. Various approaches for automated image assessment have been tested, while visual rating strategies have not been validated yet. In the AD spectrum an increase in cortical binding has been consistently observed, with a topography correlated with the profile of cognitive impairment and in agreement with the knowledge on tau pathology from neuropathological series. The evidence in non-AD diseases is more limited, with discordant findings in different cohorts and with different tracers. Post-mortem validations of in vivo data in large cohorts and studies investigating the clinical added value of this biomarker in comparison with others will be required before routine clinical use of this new modality.

Breast cancer is the most common cancer in women worldwide, and represented more than 25% of the newly diagnosed cancer cases in women in 2016. PET/CT is recommended in the clinical workup of advanced breast cancers and in cases of breast cancer recurrence and may also be proposed in treatment monitoring. PET/MRI is a new imaging technique which is now being used clinically in different countries, and which may replace PET/CT in some selected breast cancer patients, when available. A detailed description of advantages and indications of, respectively, PET and MRI techniques taken separately in breast cancer patients is beyond the scope of the present work and has already been reviewed elsewhere by our group. We focused on the technical advantages and disadvantages of combined PET/MRI acquisitions in breast cancer patients from diagnosis to follow-up. In this chapter, we cover the specifics of PET/MRI in terms of quantification and provide a summary of the different protocols performed in breast cancer PET/MRI imaging. We will also discuss the clinical advances for patient management, the potential improvements that may occur in the future, as well as the future role that may be given to this technique.

Multiple factors, namely amyloid, tau, inflammation, metabolic, and perfusion changes, contribute to the cascade of neurodegeneration and functional decline occurring in Alzheimer's disease (AD). These molecular and cellular processes and related functional and morphological changes can be visualized in vivo by two imaging modalities, namely positron emission tomography (PET) and magnetic resonance imaging (MRI). These imaging biomarkers are now part of the diagnostic algorithm and of particular interest for patient stratification and targeted drug development.In this field the availability of hybrid PET/MR systems not only offers a comprehensive evaluation in a single imaging session, but also opens new possibilities for the integration of the two imaging information. Here, we cover the clinical protocols and practical details of FDG, amyloid, and tau PET/MR imaging as applied in our institutions.

Idiopathic normal pressure hydrocephalus (iNPH) and iNPH mimics (i.e., Parkinson’s disease, progressive supranuclear palsy or dementia with Lewy bodies) share similar clinical features, and discrimination between both conditions relies on invasive time-consuming investigations. This study aims to compare [123I]FP-CIT SPECT imaging—visual rating and semiquantitative values—between iNPH and iNPH mimics. Among 56 patients with a suspicion of iNPH (76.5 ± 6.1 years; 23.2% women), 26 fulfilled the iNPH diagnostic criteria and the remaining 30 were classified as iNPH mimics. Patients were visually categorized as having normal or abnormal [123I]FP-CIT SPECT; and for the quantification of the [123I]FP-CIT SPECT imaging, we calculated striatal binding ratios (SBR) using BRASS™ automated brain analysis while applying locally established reference limits (adjusted for age). Logistic regressions were used to assess the association between [123I]FP-CIT SPECT and diagnostic groups. A normal SBR [123I]FP-CIT SPECT was present in 69.2% of iNPH and 37.9% of mimics (p value = .020), while visual rating did not differ between the two groups. Normal SBR [123I]FP-CIT SPECT values were associated with the diagnosis of iNPH, even after adjusting for white matter changes and comorbidities (adjusted odds ratio: 4.17; 95% CI 1.26–13.80). Semi-quantitative [123I]FP-CIT SPECT evaluation, but not visual assessment, discriminates iNPH patients from their mimics. [123I]FP-CIT SPECT represents an interesting neuroimaging biomarker to improve the selection of patients with iNPH for invasive shunt surgery.

Background: A corollary of the reserve hypothesis is that what is regarded as pathological cortical metabolism in patients might vary according to education. Objective: The aim of this study is to assess the incremental diagnostic value of education-adjusted over unadjusted thresholds on the diagnostic accuracy of FDG-PET as a biomarker for Alzheimer disease (AD). Methods: We compared cortical metabolism in 90 healthy controls and 181 AD patients from the Alzheimer Disease Neuroimaging Initiative (ADNI) database. The AUC of the ROC curve did not differ significantly between the whole group and the higher-education patients or the lower-education subjects. Results: The threshold of wMetaROI values providing 80% sensitivity was lower in higher-education patients and higher in the lower-education patients, compared to the standard threshold derived over the whole AD collective, without, however, significant changes in sensitivity and specificity. Conclusion: These data show that education, as a proxy of reserve, is not a major confounder in the diagnostic accuracy of FDG-PET in AD and the adoption of education-adjusted thresholds is not required in daily practice.

Tumor hypoxia is associated with radioresistance and poor prognosis after radiation therapy for prostate cancer (PCa). In this prospective pilot study, we assessed the ability ofEleven PCa patients with a Gleason score (GS) ≥ 8 underwentUptake ofPET imaging with

We present a Tc pertechnetate scintigraphy performed in a 64-year-old woman to investigate a mediastinal cystic mass in search of residual gastric mucosa after gastrectomy. She had a history of esophagectomy and gastric pull-up for esophageal cancer. Postoperative leakage necessitated ablation of the gastric pull-up and reconstruction using part of the colon. Oral realimentation resulted in mediastinal pain and brownish discharge within the trachea, raising the suspicion of residual gastric pouch. SPECT/CT demonstrated increased tracer uptake in the median part of the mediastinal cyst, and a biopsy confirmed the presence gastric mucosa.

Breast cancer is an international public health concern in which an optimal treatment plan requires a precise staging. Both MRI and PET imaging techniques have made significant progress in the last decades with constant improvements that made both modalities clinically relevant in several stages of breast cancer management and follow-up. On one hand, specific breast MRI permits high diagnostic accuracy for local tumor staging, and whole-body MRI can also be of great use in distant staging, eventually accompanied by organ-specific MRI sequences. Moreover, many different MRI sequences can be performed, including functional MRI, letting us foresee important improvements in breast cancer characterization in the future. On the contrary, 18F-FDG-PET has a high diagnostic performance for the detection of distant metastases, and several other tracers currently under development may profoundly affect breast cancer management in the future with better determination of different types of breast cancers allowing personalized treatments. As a consequence PET/MR is a promising emerging technology, and it is foreseeable that in cases where both PET and MRI data are needed, a hybrid acquisition is justified when available. However, at this stage of deployment of such hybrid scanners in a clinical setting, more data are needed to demonstrate their added value beyond just patient comfort of having to undergo a single examination instead of two, and the higher confidence of diagnostic interpretation of these co-registered images. Optimized imaging protocols are still being developed and are prone to provide more efficient hybrid protocols with a potential improvement in diagnostic accuracy. More convincing studies with larger number of patients as well as cost-effectiveness studies are needed. This article provides insights into the current state-of-the-art of PET/MR in patients with breast cancer and gives an outlook on future developments of both imaging techniques and potential applications in the future. Semin Nucl Med 45:304-321

Background Gait impairment is common in parkinsonian syndromes but not specific to striatonigral dysfunction. The relationship between the dopaminergic system and gait parameters is poorly understood. This cross-sectional study aimed to determine if gait measures are related to the striatal dopamine transporters distribution using [ 123 I]FP-CIT SPECT in patients with parkinsonian syndromes. Materials and methods Twenty-four patients with gait impairment and parkinsonian syndromes without Parkinson's disease (mean age: 73.6 ± 8.2 years) were included in this study. Gait analysis during single- and dual-task condition (walking and backwards counting) and [ 123 I]FP-CIT SPECT were performed within 3 months of each other. Patients were visually categorized as having normal ( n = 14) or abnormal ( n = 10) [ 123 I]FP-CIT SPECT. In addition, a volume-of-interest-based analysis of uptake ratios (caudate and putamen) relative to the occipital cortex and a voxelwise analysis using SPM8 were also performed. Results Patients with parkinsonian syndromes and abnormal [ 123 I]FP-CIT SPECT did not significantly differ in terms of spatiotemporal gait parameters from those with normal [ 123 I]FP-CIT SPECT. Moreover, after correction for multiple comparisons, we did not observe any association between regional uptake ratio and spatiotemporal gait parameters for single and dual tasking. Finally, none of these parameters showed a significant association with voxelwise [ 123 I]FP-CIT uptake. Conclusions Dopaminergic denervation, as measured by [ 123 I]FP-CIT SPECT, is not necessary to induce alterations of spatiotemporal gait parameters during single and dual task in patients presenting with atypical parkinsonian syndromes.

We report the case of a 56-year-old male with bilateral total knee prostheses suffering from bilateral knee pain mainly on the right side and referred for bone scintigraphy. The medical history of the patient revealed an opening wedge high tibial osteotomy performed nine years earlier, with insertion of two blocks of ceramic made of hydroxyapatite and tricalcium phosphate in a wedge configuration as synthetic bone substitutes. The porous structure of these implants is analogous to the architecture of cancellous bone and permits fibrovascular and bone ingrowth, promoting the healing process. Planar scintigraphy and SPECT/CT showed an intense uptake within those implants in the early phase as well as in the late phase of the bone scan. It also showed bilateral patellofemoral arthritis. A (99m)Tc-labeled antigranulocyte antibody scintigraphy was negative for infection or inflammation. Bilateral patellar resurfacing led to complete symptom regression, confirmed at 10 months follow-up. To the best of our knowledge, this scintigraphic pattern with such a high tracer uptake reflecting bone substitute osteointegration has not yet been published. This should be considered in patients with such bone replacement materials that are increasingly used, in order to avoid false diagnosis of inflammation or infection.