Quantitative 3D Analysis of Levator Ani Muscle Subdivisions in Nulliparous Women: MRI Feasibility Study.

BACKGROUND: The levator ani muscle (LAM) is crucial for pelvic floor stability, yet its quantitative MRI assessment is only a recent focus. Our study aims to standardize the quantitative analysis of the LAM morphology within the 3D Pelvic Inclination Correction System (3D-PICS). METHODS: We analyzed 35 static MR datasets from nulliparous women examining the pubovisceral (PVM), iliococcygeal (ICM), coccygeal (COC), and puborectal muscle (PRM). The PVM consists of three origin-insertion pairs, namely the puboanal (PAM), puboperineal (PPM) and pubovaginal muscle (PVaM). The analysis included a quantitative examination of the morphology of LAM, focusing on the median location (x/y/z) (x: anterior-posterior, y: superior-inferior, z: left-right) of the origin and insertion points (a), angles (b) and lengths (c) of LAM. Inter-rater reliability was calculated. RESULTS: Interindividual variations in 3D coordinates among muscle subdivisions were shown. In all, 93% of all origin and insertion points were found within an SD of <8 mm. Angles to the xz-plane range between -15.4° (right PRM) and 40.7° (left PAM). The PRM is the largest pelvic muscle in static MRI. The ICC indicated moderate-to-good agreement between raters. CONCLUSIONS: The accurate morphometry of the LAM and its subdivisions, along with reliable inter-rater agreement, was demonstrated, enhancing the understanding of normal pelvic anatomy in young nulliparous women.

The Monocle Sign on 18F-FDG PET Indicates Contralateral Peripheral Facial Nerve Palsy.

BACKGROUND: The aim of our study was to retrospectively analyze FDG PET/CT data in patients with facial nerve palsy (FNP) for the presence of the monocle sign. PATIENTS AND METHODS: A total of 85 patients with unilateral FNP were included into our study, thereof 73 with peripheral FNP and 12 with central FNP. FDG uptake (SUVmax, SUVmean, total lesion glycolysis) was measured in both orbicularis oculi muscles (OOMs). FDG uptake of paretic and nonparetic muscles was compared in patients with FNP (Wilcoxon test and Mann-Whitney U test) and was also compared with FDG uptake in 33 patients without FNP (Mann-Whitney U test). SUVmax ratios of OOM were compared. A receiver operating characteristic curve and Youden Index were used to determine the optimal cutoff SUVmax ratio for the prevalence of contralateral peripheral FNP. RESULTS: The SUVmax ratio of OOM was significantly higher in patients with peripheral FNP compared with patients with central FNP and those without FNP (1.70 ± 0.94 vs 1.16 ± 0.09 vs 1.18 ± 0.21, respectively; P < 0.001). The SUVmax ratio of OOM yielded an area under the curve (AUC) of 0.719 (95% confidence interval, 0.630-0.809), with an optimal cutoff of 1.41, yielding a specificity of 94.4% and a sensitivity of 44.1% for identifying contralateral peripheral FNP. One hundred percent specificity is achieved using a cutoff of 1.91 (sensitivity, 29.4%). CONCLUSIONS: Asymmetrically increased FDG uptake of the OOM (the "monocle sign") indicates contralateral peripheral FNP. A nearly 2-fold higher SUVmax represents a practically useful cutoff.

Evaluating the biodistribution for [68Ga]Ga-PSMA-11 and [18F]F-PSMA-1007 PET/CT with an inter- and intrapatient based analysis.

BACKGROUND: Liver uptake in [68Ga]Ga-PSMA-11 PET is used as an internal reference in addition to clinical parameters to select patients for [177Lu]Lu-PSMA-617 radioligand therapy (RLT). Due to increased demand, [68Ga]Ga-PSMA-11 was replaced by [18F]F-PSMA-1007, a more lipophilic tracer with different biodistribution and splenic uptake was suggested as a new internal reference. We compared the intra-patient tracer distribution between [68Ga]Ga-PSMA-11 and [18F]F-PSMA-1007. METHODS: Fifty patients who underwent PET examinations in two centers with both [18F]F-PSMA-1007 and [68Ga]Ga-PSMA-11 within one year were included. Mean standardized uptake values (SUVmean) were obtained for liver, spleen, salivary glands, blood pool, and bone. Primary tumor, local recurrence, lymph node, bone or visceral metastasis were also assessed for intra- and inter-individual comparison. RESULTS: Liver SUVmean was significantly higher with [18F]F-PSMA-1007 (11.7 ± 3.9) compared to [68Ga]Ga-PSMA-11 (5.4 ± 1.7, p < .05) as well as splenic SUVmean (11.2 ± 3.5 vs.8.1 ± 3.5, p < .05). The blood pool was comparable between the two scans. Malignant lesions did not show higher SUVmean on [18F]F-PSMA-1007. Intra-individual comparison of liver uptake between the two scans showed a linear association for liver uptake with SUVmean [68Ga]Ga-PSMA-11 = 0.33 x SUVmean [18F]F-PSMA-1007 + 1.52 (r = .78, p < .001). CONCLUSION: Comparing biodistribution of [68Ga]Ga and [18F]F tracers, liver uptake on [68Ga]Ga-PSMA-11 PET is the most robust internal reference value. Liver uptake of [18F]F-PSMA-1007 was significantly higher, but so was the splenic uptake. The strong intra-individual association of hepatic accumulation between the two scans may allow using of a conversion factor for [18F]F-PSMA-1007 as a basis for RLT selection.

Assessment of pelvic organ prolapse with the Pelvic Inclination Correction System: defining the normal range and threshold to pathology.

PURPOSE: To define the normal range and threshold values for pathologic prolapse on MRI using the PICS line and assess its correlation with the pubococcygeal line (PCL). METHODS: This prospective, IRB-approved study included 20 nulliparous volunteers and 18 prolapse patients (POP-Q Stage ≥ 2). Organ positions (bladder, cervix, anorectal junction) relative to PICS and PCL were measured on dynamic MRI. Differences in organ position were compared. Receiver-operating characteristic (ROC) analysis was performed to identify cutoff values for prolapse using the PICS line. The correlation between PICS and PCL measurements was tested with Spearman's rank correlation. RESULTS: In volunteers, median bladder and cervix positions measured to the PICS at rest were - 2.7 cm and - 5.3 cm compared to - 1.9 cm and - 2.7 cm in patients (p < 0.001). During straining, bladder and cervix were at - 0.9 cm and - 3.2 cm in volunteers versus + 2.5 cm and + 2.5 cm in patients (p < 0.001). Correlation was strong for PICS and PCL measurements for all three compartments (δ = 0.883-0.970, p ≤ 0.001). AUCs of PICS for the anterior and middle compartment were 0.98 (95% confidence interval [CI] 0.96-1.00, p < 0.001) and 0.96 (95% CI 0.89-1.00, p < 0.001) for differentiating patients from healthy volunteers. AUC for the posterior compartment was 0.76 (95% CI 0.57-0.96, p = 0.034). CONCLUSION: PICS measurements reliably differentiate patients from volunteers in the anterior and middle compartment. Future studies need to identify a reliable threshold for the posterior compartment. PICS and PCL measurements are strongly correlated.

MRI characterization of pelvic floor ligaments in nulliparous women: Technique development and morphometry within the 3D pelvic inclination correction system (3D-PICS).

PURPOSE: The aim of the MRI-study was to evaluate the visibility of the pelvic floor ligaments and to analyze the ligament morphometry in 3D space. METHODS: Twenty-two nulliparous women underwent MRI with a ligament specific protocol. MR datasets were evaluated using the 3D Pelvic Inclination Correction System (3D-PICS). The round ligament (RL), sacrospinous ligament (SSL), sacrotuberous ligament (STL), urogenital diaphragm (UGD) and uterosacral ligament (USL) were analyzed. Qualitative and quantitative analysis was performed. 3D coordinates for origin and insertion points were determined relative to the symphysis; subsequently lengths and angles were calculated. Interrater reliability was calculated to validate the point determination method. RESULTS: Moderate to good visibility was reported for the RL, the SSL, the STL and the UGD. Standard deviation of the points analyzed in the different dimensions vary from 1.5 mm to 21.3 mm. Origin and insertion points of the ligaments are found within a mean standard distance of 10.7 mm. The highest variability was seen in insertion points of RL, with a standard distance of 25.4 mm. The interrater reliability was good to very good (range of intraclass correlation coefficients (ICC) from 0.58 to 0.96), except for the UGD ventral points (ICC from 0.27 to 0.55). CONCLUSIONS: This in-vivo MRI technique development study offers first exact data describing the pelvic floor ligaments in nulliparous women in 3D-PICS. Visibility, exact 3D coordinates of the origin and insertion points, lengths, angles and interrater reliability assessed for all parameters were evaluated morphometrically.

Fully automated computational measurement of noise in positron emission tomography.

OBJECTIVES: To introduce an automated computational algorithm that estimates the global noise level across the whole imaging volume of PET datasets. METHODS: [18F]FDG PET images of 38 patients were reconstructed with simulated decreasing acquisition times (15-120 s) resulting in increasing noise levels, and with block sequential regularized expectation maximization with beta values of 450 and 600 (Q.Clear 450 and 600). One reader performed manual volume-of-interest (VOI) based noise measurements in liver and lung parenchyma and two readers graded subjective image quality as sufficient or insufficient. An automated computational noise measurement algorithm was developed and deployed on the whole imaging volume of each reconstruction, delivering a single value representing the global image noise (Global Noise Index, GNI). Manual noise measurement values and subjective image quality gradings were compared with the GNI. RESULTS: Irrespective of the absolute noise values, there was no significant difference between the GNI and manual liver measurements in terms of the distribution of noise values (p = 0.84 for Q.Clear 450, and p = 0.51 for Q.Clear 600). The GNI showed a fair to moderately strong correlation with manual noise measurements in liver parenchyma (r = 0.6 in Q.Clear 450, r = 0.54 in Q.Clear 600, all p < 0.001), and a fair correlation with manual noise measurements in lung parenchyma (r = 0.52 in Q.Clear 450, r = 0.33 in Q.Clear 600, all p < 0.001). Classification performance of the GNI for subjective image quality was AUC 0.898 for Q.Clear 450 and 0.919 for Q.Clear 600. CONCLUSION: An algorithm provides an accurate and meaningful estimation of the global noise level encountered in clinical PET imaging datasets. CLINICAL RELEVANCE STATEMENT: An automated computational approach that measures the global noise level of PET imaging datasets may facilitate quality standardization and benchmarking of clinical PET imaging within and across institutions. KEY POINTS: • Noise is an important quantitative marker that strongly impacts image quality of PET images. • An automated computational noise measurement algorithm provides an accurate and meaningful estimation of the global noise level encountered in clinical PET imaging datasets. • An automated computational approach that measures the global noise level of PET imaging datasets may facilitate quality standardization and benchmarking as well as protocol harmonization.

Sinonasal mucosal melanoma treatment response assessment to immune checkpoint inhibitors using hybrid positron emission tomography imaging.

The purpose of this retrospective study was to investigate response of sinonasal mucosal melanoma (SMM) patients to treatment with immune checkpoint inhibitors (ICI), using hybrid PET imaging. Fifteen SMM patients underwent hybrid PET imaging before and three months after initiation of ICI. The disease-specific survival (DSS) was calculated. Quantitative PET parameters of the primary tumor and their association with DSS and therapy response were investigated. Nine of the fifteen (60%) patients responded to ICI therapy. Patients with therapy response depicted on hybrid PET imaging had better DSS than those without (p = 0.0058). Quantitative PET parameters of the initial PET harbored no association with DSS or therapy response. However, these findings lack of sufficient statistical power and must be interpreted with caution. The first restaging PET-imaging after ICI initiation can help stratify patients with regard to DSS.

A third of the radiotracer dose: two decades of progress in pediatric [18F]fluorodeoxyglucose PET/CT and PET/MR imaging.

OBJECTIVES: To assess the evolution of administered radiotracer activity for F-18-fluorodeoxyglucose (18F-FDG) PET/CT or PET/MR in pediatric patients (0-16 years) between years 2000 and 2021. METHODS: Pediatric patients (≤ 16 years) referred for 18F-FDG PET/CT or PET/MR imaging of the body during 2000 and 2021 were retrospectively included. The amount of administered radiotracer activity in megabecquerel (MBq) was recorded, and signal-to-noise ratio (SNR) was measured in the right liver lobe with a 4 cm3 volume of interest as an indicator for objective image quality. Descriptive statistics were computed. RESULTS: Two hundred forty-three children and adolescents underwent a total of 466 examinations. The median injected 18F-FDG activity in MBq decreased significantly from 296 MBq in 2000-2005 to 100 MBq in 2016-2021 (p < 0.001), equaling approximately one-third of the initial amount. The median SNR ratio was stable during all years with 11.7 (interquartile range [IQR] 10.7-12.9, p = 0.133). CONCLUSIONS: Children have benefited from a massive reduction in the administered 18F-FDG dose over the past 20 years without compromising objective image quality. CLINICAL RELEVANCE STATEMENT: Radiotracer dose was reduced considerably over the past two decades of pediatric F-18-fluorodeoxyglucose PET/CT and PET/MR imaging highlighting the success of technical innovations in pediatric PET imaging. KEY POINTS: • The evolution of administered radiotracer activity for F-18-fluorodeoxyglucose (18F-FDG) PET/CT or PET/MR in pediatric patients (0-16 years) between 2000 and 2021 was assessed. • The injected tracer activity decreased by 66% during the study period from 296 megabecquerel (MBq) to 100 MBq (p < 0.001). • The continuous implementation of technical innovations in pediatric hybrid 18F-FDG PET has led to a steady decrease in the amount of applied radiotracer, which is particularly beneficial for children who are more sensitive to radiation.

Characterization of hypermetabolic lymph nodes after SARS-CoV-2 vaccination using PET-CT derived node-RADS, in patients with melanoma.

This study aimed to evaluate the diagnostic accuracy of Node Reporting and Data System (Node-RADS) in discriminating between normal, reactive, and metastatic axillary LNs in patients with melanoma who underwent SARS-CoV-2 vaccination. Patients with proven melanoma who underwent a 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (2-[18F]-FDG PET/CT) between February and April 2021 were included in this retrospective study. Primary melanoma site, vaccination status, injection site, and 2-[18F]-FDG PET/CT were used to classify axillary LNs into normal, inflammatory, and metastatic (combined classification). An adapted Node-RADS classification (A-Node-RADS) was generated based on LN anatomical characteristics on low-dose CT images and compared to the combined classification. 108 patients were included in the study (54 vaccinated). HALNs were detected in 42 patients (32.8%), of whom 97.6% were vaccinated. 172 LNs were classified as normal, 30 as inflammatory, and 14 as metastatic using the combined classification. 152, 22, 29, 12, and 1 LNs were classified A-Node-RADS 1, 2, 3, 4, and 5, respectively. Hence, 174, 29, and 13 LNs were deemed benign, equivocal, and metastatic. The concordance between the classifications was very good (Cohen's k: 0.91, CI 0.86-0.95; p-value < 0.0001). A-Node-RADS can assist the classification of axillary LNs in melanoma patients who underwent 2-[18F]-FDG PET/CT and SARS-CoV-2 vaccination.

Evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT between 2007 and 2021.

OBJECTIVES: To evaluate the evolution of CT radiation dose in pediatric patients undergoing hybrid 2-[18F]fluoro-2-deoxy-D-glucose (2-[18F]FDG) PET/CT between 2007 and 2021. METHODS AND MATERIALS: Data from all pediatric patients aged 0-18 years who underwent hybrid 2-[18F]FDG PET/CT of the body between January 2007 and May 2021 were reviewed. Demographic and imaging parameters were collected. A board-certified radiologist reviewed all CT scans and measured image noise in the brain, liver, and adductor muscles. RESULTS: 294 scans from 167 children (72 females (43%); median age: 14 (IQR 10-15) years; BMI: median 17.5 (IQR 15-20.4) kg/m2) were included. CT dose index-volume (CTDIvol) and dose length product (DLP) both decreased significantly from 2007 to 2021 (both p < 0.001, Spearman's rho coefficients -0.46 and -0.35, respectively). Specifically, from 2007 to 2009 to 2019-2021 CTDIvol and DLP decreased from 2.94 (2.14-2.99) mGy and 309 (230-371) mGy*cm, respectively, to 0.855 (0.568-1.11) mGy and 108 (65.6-207) mGy*cm, respectively. From 2007 to 2021, image noise in the brain and liver remained constant (p = 0.26 and p = 0.06), while it decreased in the adductor muscles (p = 0.007). Peak tube voltage selection (in kilovolt, kV) of CT scans shifted from high kV imaging (140 or 120kVp) to low kV imaging (100 or 80kVp) (p < 0.001) from 2007 to 2021. CONCLUSION: CT radiation dose in pediatric patients undergoing hybrid 2-[18F]FDG PET/CT has decreased in recent years equaling approximately one-third of the initial amount. ADVANCES IN KNOWLEDGE: Over the past 15 years, CT radiation dose decreased considerably in pediatric patients undergoing hybrid imaging, while objective image quality may not have been compromised.

Automated F18-FDG PET/CT image quality assessment using deep neural networks on a latest 6-ring digital detector system.

To evaluate whether a machine learning classifier can evaluate image quality of maximum intensity projection (MIP) images from F18-FDG-PET scans. A total of 400 MIP images from F18-FDG-PET with simulated decreasing acquisition time (120 s, 90 s, 60 s, 30 s and 15 s per bed-position) using block sequential regularized expectation maximization (BSREM) with a beta-value of 450 and 600 were created. A machine learning classifier was fed with 283 images rated "sufficient image quality" and 117 images rated "insufficient image quality". The classification performance of the machine learning classifier was assessed by calculating sensitivity, specificity, and area under the receiver operating characteristics curve (AUC) using reader-based classification as the target. Classification performance of the machine learning classifier was AUC 0.978 for BSREM beta 450 and 0.967 for BSREM beta 600. The algorithm showed a sensitivity of 89% and 94% and a specificity of 94% and 94% for the reconstruction BSREM 450 and 600, respectively. Automated assessment of image quality from F18-FDG-PET images using a machine learning classifier provides equivalent performance to manual assessment by experienced radiologists.

Pelvic organ movements in asymptomatic nulliparous and symptomatic premenopausal women with pelvic organ prolapse in dynamic MRI: a feasibility study comparing midsagittal single-slice with multi-slice sequences.

PURPOSE: To compare multi-slice (MS) MRI sequences of the pelvis acquired at rest and straining to dynamic midsagittal single-slice (SS) sequences for the assessment of pelvic organ prolapse (POP). METHODS: This IRB-approved prospective single-center feasibility study included 23 premenopausal symptomatic patients with POP and 22 asymptomatic nulliparous volunteers. MRI of the pelvis at rest and straining was performed with midsagittal SS and MS sequences. Straining effort, visibility of organs and POP grade were scored on both. Organ points (bladder, cervix, anorectum) were measured. Differences between SS and MS sequences were compared with Wilcoxon test. RESULTS: Straining effort was good in 84.4% on SS and in 64.4% on MS sequences (p = 0.003). Organ points were always visible on MS sequences, whereas the cervix was not fully visible in 31.1-33.3% on SS sequences. At rest, there were no statistically significant differences of organ point measurements between SS and MS sequences in symptomatic patients. At straining, positions of bladder, cervix, and anorectum were + 1.1 cm (± 1.8 cm), - 0.7 cm (± 2.9 cm), and + 0.7 cm (± 1.3 cm) on SS and + 0.4 mm (± 1.7 cm), - 1.4 cm (± 2.6 cm), and + 0.4 cm (± 1.3 cm) on MS sequences (p < 0.05). Only 2 cases of higher-grade POP were missed on MS sequences (both with poor straining effort). CONCLUSION: MS sequences increase the visibility of organ points compared to SS sequences. Dynamic MS sequences can depict POP if images are acquired with sufficient straining effort. Further work is needed to optimize the depiction of the maximum straining effort with MS sequences.

Prediction of pelvic lymph node metastases and PSMA PET positive pelvic lymph nodes with multiparametric MRI and clinical information in primary staging of prostate cancer.

Purpose: To compare the accuracy of multiparametric MRI (mpMRI), 68Ga-PSMA PET and the Briganti 2019 nomogram in the prediction of metastatic pelvic lymph nodes (PLN) in prostate cancer, to assess the accuracy of mpMRI and the Briganti nomogram in prediction of PET positive PLN and to investigate the added value of quantitative mpMRI parameters to the Briganti nomogram. Method: This retrospective IRB-approved study included 41 patients with prostate cancer undergoing mpMRI and 68Ga-PSMA PET/CT or MR prior to prostatectomy and pelvic lymph node dissection. A board-certified radiologist assessed the index lesion on diffusion-weighted (Apparent Diffusion Coefficient, ADC; mean/volume), T2-weighted (capsular contact length, lesion volume/maximal diameters) and contrast-enhanced (iAUC, kep, Ktrans, ve) sequences. The probability for metastatic pelvic lymph nodes was calculated using the Briganti 2019 nomogram. PET examinations were evaluated by two board-certified nuclear medicine physicians. Results: The Briganti 2019 nomogram performed superiorly (AUC: 0.89) compared to quantitative mpMRI parameters (AUCs: 0.47-0.73) and 68Ga-PSMA-11 PET (AUC: 0.82) in the prediction of PLN metastases and superiorly (AUC: 0.77) in the prediction of PSMA PET positive PLN compared to MRI parameters (AUCs: 0.49-0.73). The addition of mean ADC and ADC volume from mpMRI improved the Briganti model by a fraction of new information of 0.21. Conclusions: The Briganti 2019 nomogram performed superiorly in the prediction of metastatic and PSMA PET positive PLN, but the addition of parameters from mpMRI can further improve its accuracy. The combined model could be used to stratify patients requiring ePLND or PSMA PET.

Fully automated deep learning powered calcium scoring in patients undergoing myocardial perfusion imaging.

BACKGROUND: To assess the accuracy of fully automated deep learning (DL) based coronary artery calcium scoring (CACS) from non-contrast computed tomography (CT) as acquired for attenuation correction (AC) of cardiac single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI). METHODS AND RESULTS: Patients were enrolled in this study as part of a larger prospective study (NCT03637231). In this study, 56 Patients who underwent cardiac SPECT-MPI due to suspected coronary artery disease (CAD) were prospectively enrolled. All patients underwent non-contrast CT for AC of SPECT-MPI twice. CACS was manually assessed (serving as standard of reference) on both CT datasets (n = 112) and by a cloud-based DL tool. The agreement in CAC scores and CAC score risk categories was quantified. For the 112 scans included in the analysis, interscore agreement between the CAC scores of the standard of reference and the DL tool was 0.986. The agreement in risk categories was 0.977 with a reclassification rate of 3.6%. Heart rate, image noise, body mass index (BMI), and scan did not significantly impact (p=0.09 - p=0.76) absolute percentage difference in CAC scores. CONCLUSION: A DL tool enables a fully automated and accurate estimation of CAC scores in patients undergoing non-contrast CT for AC of SPECT-MPI.

Frequency and temporal evolution of COVID-19 vaccination rate among oncological patients undergoing 18F-FDG-PET.

PURPOSE: To evaluate the temporal evolution of vaccination against COVID-19 in a Swiss oncological cohort. METHODS: History of complete vaccination (i.e. at least two vaccine doses) against COVID-19 of patients undergoing oncological 18F-FDG PET/CT between February and September 2021 (n = 2613) was taken. Vaccination rate was compared with age-matched national data from the Swiss Federal Office of Public Health. Subgroup differences in temporal evolution of vaccination rate were analyzed by fitting a generalized linear model and determined by significant interaction between, sex, oncological diagnosis, and month of examination. RESULTS: Rate of complete vaccination against COVID-19 steadily increased and reached 81 % in September 2021. The fraction of vaccinated patients in the oncological cohort was higher in the beginning and approached the fraction in the age-matched general Swiss population at the end of the study period. Month of exam (p < 0.001) was the only significant predictor of the vaccination rate. CONCLUSION: Vaccination rate against COVID-19 in a Swiss oncological cohort increased steadily from February to September 2021. Compared to the age-matched general population it was higher in the beginning and similar by the end of the study period. Ethics approval: Trial registration: BASEC 2021-00444, Ethikkommission Zürich (Cantonal Ethics Committee Zurich), Switzerland, registered February 24th 2021.

Opportunistic deep learning powered calcium scoring in oncologic patients with very high coronary artery calcium (≥ 1000) undergoing 18F-FDG PET/CT.

Our aim was to identify and quantify high coronary artery calcium (CAC) with deep learning (DL)-powered CAC scoring (CACS) in oncological patients with known very high CAC (≥ 1000) undergoing 18F-FDG-PET/CT for re-/staging. 100 patients were enrolled: 50 patients with Agatston scores ≥ 1000 (high CACS group), 50 patients with Agatston scores < 1000 (negative control group). All patients underwent oncological 18F-FDG-PET/CT and cardiac SPECT myocardial perfusion imaging (MPI) by 99mTc-tetrofosmin within 6 months. CACS was manually performed on dedicated non-contrast ECG-gated CT scans obtained from SPECT-MPI (reference standard). Additionally, CACS was performed fully automatically with a user-independent DL-CACS tool on non-contrast, free-breathing, non-gated CT scans from 18F-FDG-PET/CT examinations. Image quality and noise of CT scans was assessed. Agatston scores obtained by manual CACS and DL tool were compared. The high CACS group had Agatston scores of 2200 ± 1620 (reference standard) and 1300 ± 1011 (DL tool, average underestimation of 38.6 ± 26%) with an intraclass correlation of 0.714 (95% CI 0.546, 0.827). Sufficient image quality significantly improved the DL tool's capability of correctly assigning Agatston scores ≥ 1000 (p = 0.01). In the control group, the DL tool correctly assigned Agatston scores < 1000 in all cases. In conclusion, DL-based CACS performed on non-contrast free-breathing, non-gated CT scans from 18F-FDG-PET/CT examinations of patients with known very high (≥ 1000) CAC underestimates CAC load, but correctly assigns an Agatston scores ≥ 1000 in over 70% of cases, provided sufficient CT image quality. Subgroup analyses of the control group showed that the DL tool does not generate false-positives.

Can Dynamic Whole-Body FDG PET Imaging Differentiate between Malignant and Inflammatory Lesions?

Background: Investigation of the clinical feasibility of dynamic whole-body (WB) [18F]FDG PET, including standardized uptake value (SUV), rate of irreversible uptake (Ki), and apparent distribution volume (Vd) in physiologic tissues, and comparison between inflammatory/infectious and cancer lesions. Methods: Twenty-four patients were prospectively included to undergo dynamic WB [18F]FDG PET/CT for clinically indicated re-/staging of oncological diseases. Parametric maps of Ki and Vd were generated using Patlak analysis alongside SUV images. Maximum parameter values (SUVmax, Kimax, and Vdmax) were measured in liver parenchyma and in malignant or inflammatory/infectious lesions. Lesion-to-background ratios (LBRs) were calculated by dividing the measurements by their respective mean in the liver tissue. Results: Seventy-seven clinical target lesions were identified, 60 malignant and 17 inflammatory/infectious. Kimax was significantly higher in cancer than in inflammatory/infections lesions (3.0 vs. 2.0, p = 0.002) while LBRs of SUVmax, Kimax, and Vdmax did not differ significantly between the etiologies: LBR (SUVmax) 3.3 vs. 2.9, p = 0.06; LBR (Kimax) 5.0 vs. 4.4, p = 0.05, LBR (Vdmax) 1.1 vs. 1.0, p = 0.18). LBR of inflammatory/infectious and cancer lesions was higher in Kimax than in SUVmax (4.5 vs. 3.2, p < 0.001). LBRs of Kimax and SUVmax showed a strong correlation (Spearman's rho = 0.83, p < 0.001). Conclusions: Dynamic WB [18F]FDG PET/CT is feasible in a clinical setting. LBRs of Kimax were higher than SUVmax. Kimax was higher in malignant than in inflammatory/infectious lesions but demonstrated a large overlap between the etiologies.

Diagnostic Value of Fully Automated Artificial Intelligence Powered Coronary Artery Calcium Scoring from 18F-FDG PET/CT.

OBJECTIVES: The objective of this study was to assess the feasibility and accuracy of a fully automated artificial intelligence (AI) powered coronary artery calcium scoring (CACS) method on ungated CT in oncologic patients undergoing 18F-FDG PET/CT. METHODS: A total of 100 oncologic patients examined between 2007 and 2015 were retrospectively included. All patients underwent 18F-FDG PET/CT and cardiac SPECT myocardial perfusion imaging (MPI) by 99mTc-tetrofosmin within 6 months. CACS was manually performed on non-contrast ECG-gated CT scans obtained from SPECT-MPI (i.e., reference standard). Additionally, CACS was performed using a cloud-based, user-independent tool (AI-CACS) on ungated CT scans from 18F-FDG-PET/CT examinations. Agatston scores from the manual CACS and AI-CACS were compared. RESULTS: On a per-patient basis, the AI-CACS tool achieved a sensitivity and specificity of 85% and 90% for the detection of CAC. Interscore agreement of CACS between manual CACS and AI-CACS was 0.88 (95% CI: 0.827, 0.918). Interclass agreement of risk categories was 0.8 in weighted Kappa analysis, with a reclassification rate of 44% and an underestimation of one risk category by AI-CACS in 39% of cases. On a per-vessel basis, interscore agreement of CAC scores ranged from 0.716 for the circumflex artery to 0.863 for the left anterior descending artery. CONCLUSIONS: Fully automated AI-CACS as performed on non-contrast free-breathing, ungated CT scans from 18F-FDG-PET/CT examinations is feasible and provides an acceptable to good estimation of CAC burden. CAC load on ungated CT is, however, generally underestimated by AI-CACS, which should be taken into account when interpreting imaging findings.

Frequency and intensity of [18F]-PSMA-1007 uptake after COVID-19 vaccination in clinical PET.

Objectives: To assess the frequency and intensity of [18F]-prostate-specific membrane antigen (PSMA)-1007 axillary uptake in lymph nodes ipsilateral to COVID-19 vaccination with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) in patients with prostate cancer referred for oncological [18F]-PSMA positron emission tomography (PET)/CT or PET/MR imaging. Methods: 126 patients undergoing [18F]-PSMA PET/CT or PET/MR imaging were retrospectively included. [18F]-PSMA activity (maximum standardized uptake value) of ipsilateral axillary lymph nodes was measured and compared with the non-vaccinated contralateral side and with a non-vaccinated negative control group. [18F]-PSMA active lymph node metastases were measured to serve as quantitative reference. Results: There was a significant difference in maximum standardized uptake value in ipsilateral and compared to contralateral axillary lymph nodes in the vaccination group (n = 63, p < 0.001) and no such difference in the non-vaccinated control group (n = 63, p = 0.379). Vaccinated patients showed mildly increased axillary lymph node [18F]-PSMA uptake as compared to non-vaccinated patients (p = 0.03). [18F]-PSMA activity of of lymph node metastases was significantly higher (p < 0.001) compared to axillary lymph nodes of vaccinated patients. Conclusion: Our data suggest mildly increased [18F]-PSMA uptake after COVID-19 vaccination in ipsilateral axillary lymph nodes. However, given the significantly higher [18F]-PSMA uptake of prostatic lymph node metastases compared to "reactive" nodes after COVID-19 vaccination, no therapeutic and diagnostic dilemma is to be expected. Advances in knowledge: No specific preparations or precautions (e.g. adaption of vaccination scheduling) need to be undertaken in patients undergoing [18F]-PSMA PET imaging after COVID-19 vaccination.

Prediction of benzimidazole therapy duration with PET/CT in inoperable patients with alveolar echinococcosis.

Alveolar echinococcosis is a rare parasitic disease, most frequently affecting the liver, as a slow-growing tumor-like lesion. If inoperable, long-term benzimidazole therapy is required, which is associated with high healthcare costs and occasionally with increased morbidity. The aim of our study was to determine the role 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in staging of patients with alveolar echinococcosis and to identify quantitative imaging parameters related to patient outcome and/or duration of benzimidazole therapy. In this single-center retrospective cohort study, 47 PET/CT performed for staging in patients with confirmed alveolar echinococcosis were analysed. In 43 patients (91%) benzimidazole therapy was initiated and was successfully stopped after a median of 870 days (766-2517) in 14/43 patients (33%). In inoperable patients, tests for trend of survivor functions displayed clear trends for longer benzimidazole therapy duration (p = 0.05; n = 25), and for longer time intervals to reach non-detectable serum concentration of Em-18 antibodies (p = 0.01, n = 15) across tertiles of SUVratio (maximum standardized uptake value in the echinococcus manifestation compared to normal liver tissue). Hence, in inoperable patients with alveolar echinococcosis, PET/CT performed for staging may predict the duration of benzimidazole therapy.