Effect of Time-of-Flight and Regularized Reconstructions on Quantitative Measurements and Qualitative Assessments in Newly Diagnosed Prostate Cancer With F-Fluorocholine Dual Time Point PET/MRI

Recent technical advances in positron emission tomography/magnetic resonance imaging (PET/MRI) technology allow much improved time-of-flight (TOF) and regularized iterative PET reconstruction regularized iterative reconstruction (RIR) algorithms. We evaluated the effect of TOF and RIR on standardized uptake values (maximum and peak SUV [SUV max and SUV peak ]) and their metabolic tumor volume dependencies and visual image quality for 18 F-fluorocholine PET/MRI in patients with newly diagnosed prostate cancer. Fourteen patients were administered with 3 MBq/kg of 18 F-fluorocholine and scanned dynamically for 30 minutes. Positron emission tomography images were divided to early and late time points (1-6 minutes summed and 7-30 minutes summed). The values of the different SUVs were documented for dominant PET-avid lesions, and metabolic tumor volume was estimated using a 50% isocontour and SUV threshold of 2.5. Image quality was assessed via visual acuity scoring (VAS). We found that incorporation of TOF or RIR increased lesion SUVs. The lesion to background ratio was not improved by TOF reconstruction, while RIR improved the lesion to background ratio significantly ( P < .05). The values of the different VAS were all significantly higher ( P < .05) for RIR images over TOF, RIR over non-TOF, and TOF over non-TOF. In conclusion, our data indicate that TOF or RIR should be incorporated into current protocols when available

Scatter Artifact with Ga-68-PSMA-11 PET: Severity Reduced With Furosemide Diuresis and Improved Scatter Correction

Purpose: To assess the utility of furosemide diuresis and the role of an improved scatter correction algorithm in reducing scatter artifact severity on Ga-68- Prostate-specific membrane antigen (PSMA)-11 positron emission tomography (PET). Materials and Methods: A total of 139 patients underwent Ga-68-PSMA-11 PET imaging for prostate cancer: 47 non-time-of-flight (non-TOF) PET/computed tomography, 51 PET/magnetic resonance imaging (MRI) using the standard TOF scatter correction algorithm, and 41 PET/MRI using an improved TOF scatter correction algorithm. Whole-body PET acquisitions were subdivided into 3 regions: around kidneys; between kidneys and bladder; and around bladder. The images were reviewed, and scatter artifact severity was rated using a Likert-type scale. Results: The worst scatter occurred when using non-TOF scatter correction without furosemide, where 42.1% of patients demonstrated severe scatter artifacts in 1 or more regions. Improved TOF scatter correction resulted in the smallest percentage of studies with severe scatter (6.5%). Scatter ratings by region were lowest using improved TOF scatter correction. Furosemide reduced mean scatter severity when using non-TOF and standard TOF. Conclusions: Both furosemide and scatter correction algorithm play a role in reducing scatter in PSMA PET. Improved TOF scatter correction resulted in the lowest scatter severity