Changing Threshold-Based Segmentation Has No Relevant Impact on Semi-Quantification in the Context of Structured...

Area of Science:

• Nuclear Medicine
• Oncology
• Radiology

Background:

• Prostate-specific membrane antigen (PSMA)-directed positron emission tomography/computed tomography (PET/CT) is vital for prostate cancer (PC) staging.
• The standardized PSMA Reporting and Data System (PSMA-RADS) aims to enhance interpretive certainty in PSMA PET/CT imaging.

Purpose of the Study:

• To characterize lesions using PSMA-RADS in patients undergoing 18F-PSMA-1007 PET/CT for primary PC staging.
• To assess the stability of semi-quantitative and volumetric parameters across different PSMA-RADS categories.

Main Methods:

• 18F-PSMA-1007 PET/CT imaging was performed for primary staging in 18 patients.
• 623 lesions were categorized using PSMA-RADS (3A, 3B, 4, 5) and manually segmented.
• Semi-quantitative (SUVmax, SUVpeak, SUVmean) and volumetric (PSMA-TV, TL-PSMA) parameters were analyzed at varying maximum intensity thresholds (MIT).

Main Results:

• SUVmax was significantly higher in PSMA-RADS-5 lesions compared to all other categories (p ≤ 0.0322).
• Clinically challenging PSMA-RADS-3A/3B lesions showed significantly lower SUVmax and SUVpeak compared to PSMA-RADS-4/5 cohorts.
• Changing MIT did not significantly impact SUVmean and TL-PSMA in PSMA-RADS-5 lesions, unlike PSMA-TV.

Conclusions:

• SUVmax is a key parameter that can assist molecular imaging specialists in assigning accurate PSMA-RADS scores, thereby increasing diagnostic certainty.
• PSMA-RADS provides a standardized framework for evaluating PSMA PET/CT findings in prostate cancer staging.
• Volumetric parameters like PSMA-TV require careful consideration of MIT, while SUVmean and TL-PSMA demonstrate stability.