18F-fluoride PET/CT for bone scanning

Summary Aim: 18F-fluoride PET/CT is a promising tool for bone scanning. Recently, guidelines concerning the conduct of 18F-fluoride PET/CT have been published. One open question of the German guideline was the necessity of attenuation correction for 18F-fluoride PET/CT. We evaluated the need for a CT-based attenuation correction in 18F-fluoride PET/CT scans for the detection of bone lesions. Patients and methods: We retrospectively analyzed wholebody 18F-Fluoride PET/CT scans of 59 cancer patients. The lesions were categorized as malignant, benign or inconclusive. This assignment was performed for every lesion in both: attenuation corrected (AC) and non-attenuation- corrected (NAC) images. The maximum standardized uptake values (SUVmax) of the lesion in the AC images were also determined. Results: All bone lesions were detected in both image modalities. The AC images revealed 201 lesions categorized as malignant, 114 as benign and 35 as inconclusive. Without an AC, the results were 209, 116 and 25, respectively (p > 0.05). 10/35 lesions categorized as inconclusive in the AC images were categorized as malignant in the NAC images, whereas 8 lesions were confirmed after comparison with other imaging modalities and follow-up data and 2 lesions were categorized as benign. The SUVmax for lesions identified as malignant showed a broad overlap with the SUV max of benign lesions and can consequently not be used for differentiation. Conclusion: An AC is not necessary for detecting bone lesions on 18F-fluoride PET/CT scans as the detection capability is identical for NAC imaging and lesion assignment was even better than with AC imaging. SUVmax seems not to improve the differentiation between malignant and benign bone lesions.

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Comparison of standardized uptake values measured on 18F-NaF PET/CT scans using three different tube current intensities

Radiologia Brasileira ◽

10.1590/0100-3984.2014.0034 ◽

2015 ◽

Vol 48 (1) ◽

pp. 17-20 ◽

Cited By ~ 1

Author(s):

Agnes Araujo Valadares ◽

Paulo Schiavom Duarte ◽

Eduardo Bechtloff Woellner ◽

George Barberio Coura-Filho ◽

Marcelo Tatit Sapienza ◽

...

Keyword(s):

Attenuation Correction ◽

Lumbar Vertebra ◽

Ct Scans ◽

Femoral Diaphysis ◽

Standardized Uptake Values ◽

Pet Ct ◽

Tube Current ◽

The Mean ◽

Humeral Diaphysis ◽

Ct Studies

Objective: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on 18FNaF PET/CT scans. Materials and Methods: A total of 254 18F-NaF PET/CT studies were analyzed using 10, 20 and 30 mAs. The SUVs were calculated in volumes of interest (VOIs) drawn on three skeletal regions, namely, right proximal humeral diaphysis (RH), right proximal femoral diaphysis (RF), and first lumbar vertebra (LV1) in a total of 712 VOIs. The analyses covered 675 regions classified as normal (236 RH, 232 RF, and 207 LV1). Results: Mean SUV for each skeletal region was 3.8, 5.4 and 14.4 for RH, RF, and LV1, respectively. As the studies were grouped according to mAs value, the mean SUV values were 3.8, 3.9 and 3.7 for 10, 20 and 30 mAs, respectively, in the RH region; 5.4, 5.5 and 5.4 for 10, 20 and 30 mAs, respectively, in the RF region; 13.8, 14.9 and 14.5 for 10, 20 and 30 mAs, respectively, in the LV1 region. Conclusion: The three tube current values yielded similar results for SUV calculation.

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Validation of MR-Based Attenuation Correction of a Newly Released Whole-Body Simultaneous PET/MR System

BioMed Research International ◽

10.1155/2019/8213215 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Guobing Liu ◽

Tuoyu Cao ◽

Lingzhi Hu ◽

Jiaxu Zheng ◽

Lifang Pang ◽

...

Keyword(s):

Soft Tissue ◽

Attenuation Correction ◽

Whole Body ◽

Bone Lesions ◽

Soft Tissue Lesions ◽

Standardized Uptake Values ◽

Positron Emission ◽

Pet Ct ◽

The Mean ◽

Relative Differences

The aim of this study was to validate quantitative performance of a newly released simultaneous positron emission tomography (PET)/magnetic resonance imaging (MRI) scanner, by using MR-based attenuation correction (MRAC), both in phantom study and in patient study. PET/MRI image uniformities of a phantom under different hardware configurations were tested and compared. Thirty patients were examined with 2-deoxy-2-[18F]fluoro-D-glucose (18F-FDG) PET/computed tomography (CT) and subsequent PET/MRI. PET images from PET/MRI were corrected with MRAC (PETMR), CT-based attenuation maps (μ-maps, PETCT), and segmented CT μ-maps (PETCTSeg) derived from PET/CT. Standardized uptake values (SUVs) were compared among the 3 sets of PET in main organs (bone, liver and lung) and in 52 FDG-avid lesions, including soft-tissue lesions and bone lesions. The result showed that PET imaging uniformities of PET/MRI under different configurations were good (<8.8%). The SUV differences among the 3 sets of PET varied with organs and lesion types. In detail, the mean relative differences of SUV between PETMR and PETCT were as follows: −18.8%, bone (SUVmean); −8.0%, liver (SUVmean); −12.2%, lung (SUVmean); −18.1%, bone lesions (SUVmean); −13.3%, bone lesions (SUVmax); −8.2%, soft-tissue lesions (SUVmean); and −7.3%, soft-tissue lesions (SUVmax). The mean relative differences between PETMR and PETCTSeg were as follows: −19.0%, bone (SUVmean); −3.5%, liver (SUVmean); −3.3%, lung (SUVmean); −19.3%, bone lesions (SUVmean); −17.5%, bone lesions (SUVmax); −5.5%, soft-tissue lesions (SUVmean); and −4.4%, soft-tissue lesions (SUVmax). The differences of SUV between PETMR and PETCT were larger than those between PETMR and PETCTSeg, in both soft tissue and soft-tissue lesions (P<0.001), but not in bone or bone lesions. In conclusion, MRAC in the newly released PET/MR system is accurate in most tissues, with SUV deviations being generally less than 10%, compared to PET/CT. In bone, however, underestimations can be substantial, which may be partially attributed to segmentation of the MR-based μ-maps.

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FDG-PET/CT Is Superior to Anatomic Imaging for the Staging and Follow Up of Bony Involvement in Patients with Lymphoma.

Blood ◽

10.1182/blood.v110.11.2330.2330 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2330-2330 ◽

Cited By ~ 1

Author(s):

Rebecca L. Elstrom ◽

Richard K.J. Brown

Keyword(s):

Fdg Pet ◽

Bone Involvement ◽

Ct Scans ◽

Bone Lesions ◽

Pet Ct ◽

Fdg Pet Ct ◽

Bone Lymphoma ◽

Diagnostic Ct ◽

Ct And Mri

Abstract Background and Objectives: Positron tomission tomography using 18fluoro-2-deoxyglucose in combination with low dose non-enhanced computed tomography (FDG-PET/CT) is increasingly utilized in the management of patients with lymphoma. Numerous studies have demonstrated improved accuracy for both staging and restaging as compared to standard diagnostic CT. However, there is a paucity of data on the significance of bone uptake in patients with lymphoma. This is one area in which FDG-PET has the potential to dramatically influence care of lymphoma patients. However, false positive FDG-PET has been shown in patients with traumatic or benign bone lesions. The aim of this study was to evaluate the utility and accuracy of FDG-PET/CT in comparison with standard anatomic imaging with CT and MRI in the staging and follow up of patients with Hodgkin lymphoma (HL) or diffuse large B cell lymphoma (DLBCL). Design and Methods: We reviewed a database of 75 lymphoma patients who underwent concurrent FDG-PET/CT and standard diagnostic CT scans or MRI, and identified those with bone involvement by lymphoma. Involvement of bone was demonstrated by either biopsy of a bone lesion or radiologic appearance and clinical follow up highly suggestive of bone involvement. Follow up studies were evaluated for resolution of FDG avid lesions on PET, and anatomic lesions on CT or MRI. Results: Fourteen patients with either HL or DLBCL who underwent both FDG-PET/CT and diagnostic CT were identified to have bone involvement by lymphoma. FDG-PET identified bone involvement in all 14 patients, whereas CT imaging identified bone involvement in seven. One patient in whom CT did not detect bone involvement had evidence of bone lymphoma by MRI. Eight patients had confirmation of bone lymphoma by biopsy, while 6 were confirmed by clinical criteria (radiologic appearance and clinical follow up). Thirteen of the patients had follow up FDG-PET/CT scans, and 12 had follow up CT and/or MRI. All follow up FDG-PET scans showed resolution of FDG avid bone lesions after anti-lymphoma therapy. In contrast, all CT and MRI scans which originally showed evidence of bone involvement had persistent abnormality on follow up, with only 2 showing improvement. At a median follow up of 9 months (range 0–20 months), 11 patients remain in remission, while 2 patients subsequently showed progression by FDG-PET, CT and biopsy in soft tissue sites, but not bone. One patient remains on therapy. No patient in our series was found to have a benign etiology of a lesion initially thought due to lymphoma. Conclusion: FDG-PET/CT is useful in the staging and follow up of patients with lymphoma with bone involvement. The lack of sensitivity of CT combined with the delayed resolution of anatomic abnormalities limit the utility of standard anatomic imaging, making FDG-PET/CT the imaging modality of choice for patients with bone lymphoma.

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Assessing bone response to cabozantinib in patients (pts) with metastatic urothelial carcinoma (mUC) using 18F-Sodium Fluoride (NaF) PET/CT.

Journal of Clinical Oncology ◽

10.1200/jco.2017.35.6_suppl.328 ◽

2017 ◽

Vol 35 (6_suppl) ◽

pp. 328-328

Author(s):

Jeffrey Lin ◽

Liza Lindenberg ◽

Seth M. Steinberg ◽

Yolanda McKinney ◽

Juanita Weaver ◽

...

Keyword(s):

Soft Tissue ◽

Serum Alkaline Phosphatase ◽

Progression Free Survival ◽

Bone Lesions ◽

Anatomical Site ◽

Kaplan Meier ◽

Standardized Uptake Values ◽

Best Response ◽

Bone Response ◽

Pet Ct

328 Background: NaF PET/CT is a radiotracer used for the assessment of bone metastases (mets). The goal of our study was to assess bone mets using NaF PET/CT imaging in mUC pts treated with cabozantinib. Methods: We conducted a single-arm phase II trial of cabozantinib in pts with mUC. Pts with known bone mets underwent a NaF PET/CT scan at baseline and every 8 weeks until progression. At each scan, we captured, the number of lesions per pt and per anatomical site, the maximum standardized uptake values (SUV), and serum alkaline phosphatase (AP). Bone responses (bone response (BR), stable disease (SD), progressive disease (PD)) were assigned to each pt based on the NaF report. Change from baseline to the time of best response for SUV, the number of lesions, and AP were compared between BR + SD vs PD were analyzed using an exact Wilcoxon rank sum test. The Kaplan-Meier method was used to determine the association of progression free survival (PFS) or overall survival (OS) with baseline SUV and number of lesions. Results: 68 pts enrolled on study, 22 pts had bone mets at baseline (6 bone only and 16 with bone and soft-tissue mets) (median OS 4.6 mo (95% CI: 3.4-7.7 mo), and median PFS 2.0 mo (95% CI: 1.8-3.9 mo)) of which 15 pts had follow up NaF scans. At baseline, 147 total lesions were analyzed, and the lesion distribution was: spine 29%, ribs 21%, pelvis 18%, skull 11%, femur 6%, scapula 3%, humerus 3%, sternum 3%, sacrum 3%, fibula 1%, and clavicle 0.7%. 5/15 pts had BR (and remained on study 238, 252, 182, 161, and 56 days), 4/15 SD, and 6/15 PD at best response. Sites of PD occurred in bone 10/22, bone and soft-tissue 5/22, and soft-tissue 7/22. The percent difference in number of lesions among responders and non-responders was 43% (p = 0.0039). At baseline, there was no association with PFS or OS and number of lesions (p = 0.84, p = 0.97), SUV (p = 0.83, p = 0.97), or AP (p = 0.97, p = 0.33). Conclusions: Pts with mUC and bone disease have poor overall outcome. Most bone lesions were found in the spine, ribs, and pelvis. Larger studies are needed to assess the correlation of NaF response with clinical outcome in mUC. We have an ongoing study using NaF PET to assess bone mets in mUC treated with cabozantinib/nivolumab/ipilimumab. Clinical trial information: NCT01688999.

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Comparison of PSMA PET/CT with fluoride PET/CT for detection of bone metastatic disease in prostate cancer

10.21203/rs.3.rs-776117/v1 ◽

2021 ◽

Author(s):

Naresh Kumar Regula ◽

Vasileios Kostaras ◽

Silvia Johansson ◽

Carlos Trampal ◽

Elin Lindström ◽

...

Keyword(s):

Prostate Cancer ◽

Bone Metastasis ◽

Soft Tissue ◽

Diagnostic Performance ◽

Bone Lesions ◽

Soft Tissue Lesions ◽

Contrast Enhanced Ct ◽

Standardized Uptake Values ◽

Psma Pet ◽

Pet Ct

Abstract 18F-NaF positron emission tomography/computed tomography (fluoride PET/CT) is considered the most sensitive technique to detect bone metastasis in prostate cancer (PCa). 68Ga-PSMA-11 (PSMA) PET/CT is increasingly used for staging of PCa. This study primarily aimed to compare the diagnostic performance of fluoride PET/CT and PSMA PET/CT in identifying bone metastasis followed by a comparison of PSMA PET/CT with contrast-enhanced CT (CE-CT) in identifying soft tissue lesions as a secondary objective. Methods: Twenty-eight PCa patients with high suspicion of disseminated disease following curative treatment were prospectively evaluated. PET/CT examinations using fluoride and PSMA were performed. All suspicious bone lesions were counted, and the tracer uptake was measured as standardized uptake values (SUV) for both tracers. In patients with multiple findings, ten bone lesions with highest SUVmax were selected from which identical lesions from both scans were considered for direct comparison of SUVmax. PSA at scan was correlated with findings of both scans. Results: Both scans were negative for bone lesions in 7 patients (25%). Of 699 lesions consistent with skeletal metastasis in 21 patients on fluoride PET/CT, PSMA PET/CT identified 579 lesions (83%). In 69 identical bone lesions fluoride PET/CT showed significantly higher uptake (mean SUVmax:73.1 ± 36.8) compared to PSMA PET/CT (34.5 ± 31.4; p < 0.001). PSA at scan was correlated with SUVmax of PSMA PET/CT (r = 0.58; p = 0.01). No correlation was observed between PSA and fluoride PET/CT measurements. Compared to CE-CT, PSMA PET/CT showed better diagnostic performance in locating local (96% vs 61%, p = 0.004) and lymph node (94% vs 46%, p < 0.001) metastasis. Conclusion: PSMA PET/CT was able to detect majority of bone lesions that were positive on fluoride PET/CT and was better correlated with PSA at time of scan. Further, this study indicates better diagnostic performance of PSMA PET/CT to locate soft tissue lesions compared to CE-CT.

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Lesion concordance, image quality and artefacts in PET/CT

Nuklearmedizin ◽

10.3413/nukmed-0275 ◽

2010 ◽

Vol 49 (04) ◽

pp. 129-137 ◽

Cited By ~ 1

Author(s):

B. J. Krause ◽

S. M. Eschmann ◽

K. U. Juergens ◽

H. Kuehl ◽

A. C. Pfannenberg ◽

...

Keyword(s):

Image Quality ◽

Fdg Pet ◽

Whole Body ◽

Ct Scans ◽

Intravenous Contrast ◽

Metal Implants ◽

Body Regions ◽

Pet Ct ◽

Fdg Pet Ct ◽

Attenuation Corrected

Summary Aim: This study had three major objectives: 1.) to record the number of concordant (both in PET and CT) pathological lesions in different body regions/organs, 2.) to evaluate the image quality and 3.) to determine both, the quantity and the quality of artefacts in whole body FDG PET/CT scans. Patients, methods: Routine whole body scans of 353 patients referred to FDG-PET/ CT exams at 4 university hospitals were employed. All potentially malignant lesions in 13 different body regions/organs were classified as either concordant or suspicious in FDG-PET or CT only. In the latter case the diagnostic relevance of this disparity was judged. The image quality in PET and CT was rated as a whole and separately in 5 different body regions. Furthermore we investigated the frequency and site of artefacts caused by metal implants and oral or intravenous contrast media as well as the subjective co-registration quality (in 4 body regions) and the diagnostic impact of such artefacts or misalignment. In addition, the readers rated the diagnostic gain of adding the information from the other tomographic method. Results: In total 1941 lesions (5.5 per patient) were identified, 1094 (56%) out of which were concordant. 602 (71%) out of the 847 remaining lesions were detected only with CT, 245 (29%) were only PET-positive. As expected, CT particularly depicted the majority of lesions in the lungs and abdominal organs. However, the diagnostic relevance was greater with PET-only positive lesions. Most of the PET/CT scans were performed with full diagnostic CT including administration of oral and intravenous contrast media (> 80%). The image quality in PET and CT was rated excellent. Artefacts occurred in more than 60% of the scans and were mainly due to (dental) metal implants and contrast agent. Nevertheless there was almost no impact on diagnostic confidence if reading of the non attenuation corrected PET was included. The co-registration quality in general was also rated as excellent. Misalignment mostly occurred due to patient motion and breathing and led to diagnostic challenges in about 4% of all exams. The diagnostic gain of adding PET to a CT investigation was rated higher than vice versa. Conclusions: As the image quality in both PET and CT was more than satisfying, CT-artefacts almost never led to diagnostic uncertainties and serious misalignment rarely occurred, PET/CT can be considered as suitable for routine use and may replace single PET- and CT-scans. However, additional reading of the non attenuation corrected PET is mandatory to assure best possible diagnostic confidence in PET. Since approximately half of all lesions found in PET/CT were not concordant, at least in a setting with a diagnostic CT the exams need to be reported by both a nuclear medicine physician and a radiologist in consensus.

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Impact of the Noise Penalty Factor on Quantification in Bayesian Penalized Likelihood (Q.Clear) Reconstructions of 68Ga-PSMA PET/CT Scans

Diagnostics ◽

10.3390/diagnostics11050847 ◽

2021 ◽

Vol 11 (5) ◽

pp. 847

Author(s):

Sjoerd Rijnsdorp ◽

Mark J. Roef ◽

Albert J. Arends

Keyword(s):

Penalized Likelihood ◽

Ct Scans ◽

Ct Scanner ◽

Scan Time ◽

Standardized Uptake Values ◽

Positron Emission ◽

Penalty Factor ◽

Psma Pet ◽

Pet Ct ◽

Voxel Grid

Functional imaging with 68Ga prostate-specific membrane antigen (PSMA) and positron emission tomography (PET) can fulfill an important role in treatment selection and adjustment in prostate cancer. This article focusses on quantitative assessment of 68Ga-PSMA-PET. The effect of various parameters on standardized uptake values (SUVs) is explored, and an optimal Bayesian penalized likelihood (BPL) reconstruction is suggested. PET acquisitions of two phantoms consisting of a background compartment and spheres with diameter 4 mm to 37 mm, both filled with solutions of 68Ga in water, were performed with a GE Discovery 710 PET/CT scanner. Recovery coefficients (RCs) in multiple reconstructions with varying noise penalty factors and acquisition times were determined and analyzed. Apparent recovery coefficients of spheres with a diameter smaller than 17 mm were significantly lower than those of spheres with a diameter of 17 mm and bigger (p < 0.001) for a tumor-to-background (T/B) ratio of 10:1 and a scan time of 10 min per bed position. With a T/B ratio of 10:1, the four largest spheres exhibit significantly higher RCs than those with a T/B ratio of 20:1 (p < 0.0001). For spheres with a diameter of 8 mm and less, alignment with the voxel grid potentially affects the RC. Evaluation of PET/CT scans using (semi-)quantitative measures such as SUVs should be performed with great caution, as SUVs are influenced by scanning and reconstruction parameters. Based on the evaluation of multiple reconstructions with different β of phantom scans, an intermediate β (600) is suggested as the optimal value for the reconstruction of clinical 68Ga-PSMA PET/CT scans, considering that both detectability and reproducibility are relevant.

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Quantitative Effect of Metal Artefact Reduction on CT-Based Attenuation Correction in FDG PET/CT in Patients With Hip Prosthesis

10.21203/rs.3.rs-76945/v1 ◽

2020 ◽

Author(s):

Maarten Haemels ◽

Delphine Vandendriessche ◽

Jeroen De Geeter ◽

James Velghe ◽

Maxence Vandekerckhove ◽

...

Keyword(s):

Hip Prosthesis ◽

Hip Prostheses ◽

Metal Artefact Reduction ◽

Standardized Uptake Values ◽

Pet Ct ◽

Measured Activity ◽

Metal Artefact ◽

Artefact Reduction ◽

Conventional Ct ◽

Attenuation Corrected

Abstract Background Metal artefact reduction (MAR) techniques still are in limited use in positron emission tomography / computed tomography (PET/CT). This study aimed to investigate the effect of Smart MAR on quantitative PET analysis in the vicinity of hip prostheses.Material and methods Activities were measured on PET/CT images in 6 sources with 10-fold activity concentration contrast to background, attached to the head, neck and the major trochanter of a human cadaveric femur, and in the same sources in similar locations after a hip prosthesis (titanium cup, ceramic head, chrome-cobalt stem) had been inserted into the femur. Measurements were compared between PET attenuation corrected using either conventional or MAR CT. In 46 patients harbouring 61 hip prostheses, standardized uptake values (SUV) in 6 periprosthetic regions and the bladder, were compared between PET attenuation corrected with either conventional or MAR CT. Results Using conventional CT, measured activity decreased from 2 to 13% when the prosthesis was inserted. Use of MAR CT increased measured activity by up to 11 12% compared with conventional CT and reduced the relative difference with the reference values to under 5% in all sources.In all regions, to the exception of the prosthesis shaft, SUVmean increased significantly (p<0.001) by use of MAR CT. Median (interquartile range) percentual increases of SUVmean were 1.9 (0.0-4.5), 3.9 (1.8-7.8), 7.0 (3.4-11.1), 1.7 (0.9-3.7), 1.5 (0.8-3.3) in acetabulum, lateral neck, medial neck, lateral diaphysis and medial diaphysis, respectively. Except for the shaft, the coefficient of variation did not increase significantly. Except for the erratic changes in the prosthesis shaft, decreases of SUVmean were rare and small. Bladder SUVmean increased by 1% in patients with unilateral and by 4% in patients with bilateral prosthesis. Conclusions In a realistic hip prosthesis phantom, Smart MAR restores quantitative accuracy by recovering counts in underestimated sources. In patient studies, Smart MAR increases SUV in all areas surrounding the prosthesis, most markedly in the femoral neck region. This proves that underestimation of activity is the most prevalent metal artefact in hip prostheses. Smart MAR increases SUV in the urinary bladder, indicating effects at a distance from the prosthesis.

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Changing Threshold-Based Segmentation Has No Relevant Impact on Semi-Quantification in the Context of Structured Reporting for PSMA-PET/CT

Cancers ◽

10.3390/cancers14020270 ◽

2022 ◽

Vol 14 (2) ◽

pp. 270

Author(s):

Patrick W. Mihatsch ◽

Matthias Beissert ◽

Martin G. Pomper ◽

Thorsten A. Bley ◽

Anna K. Seitz ◽

...

Keyword(s):

Tumor Volume ◽

Bone Lesions ◽

Primary Staging ◽

Standardized Uptake Values ◽

Positron Emission ◽

Diagnostic Certainty ◽

Psma Pet ◽

Pet Ct ◽

The Stability ◽

Specific Membrane

Prostate-specific membrane antigen (PSMA)-directed positron emission tomography/computed tomography (PET/CT) is increasingly utilized for staging of men with prostate cancer (PC). To increase interpretive certainty, the standardized PSMA reporting and data system (RADS) has been proposed. Using PSMA-RADS, we characterized lesions in 18 patients imaged with 18F-PSMA-1007 PET/CT for primary staging and determined the stability of semi-quantitative parameters. Six hundred twenty-three lesions were categorized according to PSMA-RADS and manually segmented. In this context, PSMA-RADS-3A (soft-tissue) or -3B (bone) lesions are defined as being indeterminate for the presence of PC. For PMSA-RADS-4 and -5 lesions; however, PC is highly likely or almost certainly present [with further distinction based on absence (PSMA-RADS-4) or presence (PSMA-RADS-5) of correlative findings on CT]. Standardized uptake values (SUVmax, SUVpeak, SUVmean) were recorded, and volumetric parameters [PSMA-derived tumor volume (PSMA-TV); total lesion PSMA (TL-PSMA)] were determined using different maximum intensity thresholds (MIT) (40 vs. 45 vs. 50%). SUVmax was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories (p ≤ 0.0322). In particular, the clinically challenging PSMA-RADS-3A lesions showed significantly lower SUVmax and SUVpeak compared to the entire PSMA-RADS-4 or -5 cohort (p < 0.0001), while for PSMA-RADS-3B this only applies when compared to the entire PSMA-RADS-5 cohort (p < 0.0001), but not to the PSMA-RADS-4 cohort (SUVmax, p = 0.07; SUVpeak, p = 0.08). SUVmean (p = 0.30) and TL-PSMA (p = 0.16) in PSMA-RADS-5 lesions were not influenced by changing the MIT, while PSMA-TV showed significant differences when comparing 40 vs. 50% MIT (p = 0.0066), which was driven by lymph nodes (p = 0.0239), but not bone lesions (p = 0.15). SUVmax was significantly higher in PSMA-RADS-5 lesions compared to all other PSMA-RADS categories in 18F-PSMA-1007 PET/CT. As such, the latter parameter may assist the interpreting molecular imaging specialist in assigning the correct PSMA-RADS score to sites of disease, thereby increasing diagnostic certainty. In addition, changes of the MIT in PSMA-RADS-5 lesions had no significant impact on SUVmean and TL-PSMA in contrast to PSMA-TV.

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