肥満体型の種類がFDG-PET の画質に与える影響

抄録

Purpose: The aim of our study is to evaluate whether an ¹⁸F-FDG PET/CT image quality is influenced by the obesity type visceral fat or subcutaneous fat. Methods: We chose continuously 68 patients with obesity (35 subcutaneous fats and 33 visceral fats) who underwent an ¹⁸F-FDG PET/CT scan at our clinic from January 3, 2015 to June 30, 2015. And then, we calculated the noise equivalent count (NEC_density), the signal to noise ratio of the liver (SNR_liver), and the ratio of random coincidence counts to total prompt (random/prompt countrate) on each PET/CT image. Results: We observed that NEC_density was decreased as the body mass index (BMI) and the abdominal circumference increased regardless of the obesity type. When the BMI was on the same degree between two types, however, NEC_density of a visceral fat was 21.6% that is inferior to that of subcutaneous fat on the average. A similar relation was satisfied also in abdominal circumference. Conversely, random/prompt countrate of a visceral fat was more than that of subcutaneous fat when the abdominal circumference and BMI were on the same degree, respectively. Overall, random/prompt countrate tended to increase as BMI and the abdominal circumference increased. With respect to SNR_liver, the value of a visceral fat was inferior to that of subcutaneous fat unconditionally. Conclusion: When the BMI and abdominal circumference are on the same degree, respectively, the ¹⁸F-FDG PET/CT image quality of visceral fat is inferior to that of subcutaneous fat. The measure is to extend the collection time by about 20% in the pelvic area from the abdomen of visceral fat type obesity.