Reduction of Radiation Not Recommended for 18F-FDG-PET/MRI of Abdomen
Image quality may be affected if reduced doses in 18F-FDG-PET/MRI are used for abdominal examinations.
Reducing doses in 18F-FDG-PET/MRI of the abdomen may affect image quality, according to a study published in the Journal of Nuclear Medicine. Researchers from Germany evaluated the effect of stepwise reduced doses on objective and subjective image parameters and on oncologic readings in whole-body 18F-FDG-PET/MRI. The researchers retrospectively simulated the stepwise reduction of 18F-FDG doses of 19 patients, mean age of 50.9 years with a body mass index (BMI), who received a whole-body PET/MRI examination, from 3 to 0.5 MBq/kgBW in intervals of 0.25. Objective imaging parameters were assessed by measuring the standardized uptake value (SUV) and coefficient of variation (CV) in different regions: • Aorta • Liver• Spleen• Kidney• Small bowel• Lumbar vertebra• Psoas muscle• Urinary bladder They also evaluated the noise equivalent count rates (NECR) in each bed position. Subjective image quality was evaluated with a blinded reading of each simulated PET compared to the dose of 2 MBq/kgBW. Oncologic reading was performed first, according to PET response criteria in solid tumors (PERCIST) in each dose, and second by defining malignant lesions in doses of 2 MBq/kgBW and the maximum dose image (gold standard). Ninety lesions were found using the standard maximum dose of 3 MBq/kgBW. Eighty-six lesions (95 percent) of these lesions were correctly identified with the lower FDG dose; there were no false-negative or false-positive results. With decreasing doses, regions in the mid-abdomen showed a stronger decrease of SUVmean and NECR than regions in the upper abdomen. SUVmean was -45 percent on average in the small bowel and -15 percent on average in the liver. CV showed a non-linear increase, pronounced below 1.5 MBq/kgBW. Subjective image quality was stable over a range between 1.25 and 2.75 MBq/kgBW compared to 2 MBq/kgBW. However, large photopenic areas in the mid abdomen were observed in two patients. In the PERCIST reading, target lesions were above the liver threshold with a stable SUVpeak in all cases down to 2 MBq/kgBW. The researchers concluded a reduction of doses in 18F-FDG-PET/MRI might be possible down to 2 MBq/kgBW in oncologic whole-body examinations, but the image quality in the mid-abdomen may be more affected by lower doses than in the upper abdomen and in single cases, large photopenic areas can occur. “Therefore, we do not recommend reducing doses below 3 MBq/kgBW in adults at this time,” they wrote.
New MRI Research Explores Links Between Waist-to-Hip Ratio and Memory in Aging
March 13th 2025Researchers found that a higher waist-to-hip ratio in midlife was associated with higher mean diffusivity in 26 percent of total white matter tracts in the cingulum as well as the superior and inferior longitudinal fasciculus.
New Analysis Forecasts Substantial Cost Savings with the Use of Photon Counting CT for CCTA
March 8th 2025The use of ultra-high-resolution photon-counting CT in the evaluation of stable chest pain may significantly reduce follow-up tests and invasive coronary angiography (ICA) procedures, possibly resulting in millions in health-care cost savings, according to a cost-effectiveness analysis presented recently at the European Congress of Radiology.
