Optimized dose regimen of 18F-FDG total body PET/CT imaging in oncological patients

1144 Objectives: The current guidelines for FDG PET/CT imaging recommend an injection dose with a linear or quadratic relation with the patient weight. [1] However, a degreased image quality in obese patients was found in the clinic for total-body PET/CT imaging. The purpose was to explore an optimized dose regimen of the administered activity of 18F-FDG in total body PET/CT imaging without compromising image quality.\n Methods: A total number of 78 consecutive total-body PET/CT scans (uEXPLORER) for oncological patients (Female/Male: 27/51, age: 59.7 ± 13.7 y, weight: 63.9 ± 17.5 kg, BMI: 23.3 ± 4.8) were retrospectively enrolled in the study. Patients were equally distributed according to their BMI according to WHO criteria (underweight, normal weight, overweight, obese). The acquired list-mode PET rawdata were then segmented into 300s, 120s, 60s, 45s and 30s, and reconstructed with the clinical parameters. The image quality was assessed independently by two experienced nuclear medicine physicians to determine the clinical preferred image quality. The liver SUV was measured by manually drawing a region of interest (ROI) on the homogeneous region of the right liver lobe and then normalized by the square root of the product of injection dose (MBq) and acquisition time (min). The normalized SNR, referred as SNRnorm, was then analyzed using linear and non-linear fits with patient-dependent parameters, including patient weight, weight/height, BMI, lean body mass, fat mass and free fat mass, to determine the best correlating parameter and fit method. This optimized dose regimen was then validated by a second oncological patient cohort (Female/Male: 9/29, age: 61.3 ± 14.1 y, weight: 68.4 ± 13.7 kg, BMI: 24.8 ± 3.9).\n Results: Of all patient-dependent parameters, the linear fit with BMI showed the strongest correlation (R2 = 0.69) with SNRnorm as shown in Figure 1A. The subjective assessment revealed a SNR of 14.0 as the clinically preferred image quality threshold in the study. And the optimized dose regimen was determined as: injection dose = 39.2 MBq/ (-0.03*BMI + 1.49)2 for a given acquisition time in clinic. The quadratic relation between injection dose and BMI was confirmed with a constant image quality independent of patient size as shown in Figure 1B. In addition, the proposed regimen could reduce the total injection dose compared with the previous weight-based regimen.\n Conclusions: The optimized regimen recommended a quadratic relation between the FDG injection dose and patient‘s BMI. The regimen has been validated by a patient cohort which indicated a constant image quality among patients in different BMI groups.