Optimization of scan time in 18F FDG-PET/CT imaging for cardiac sarcoidosis

Objective We determined an appropriate noise equivalent count per volume (NEC _density ) for cardiac spot acquisition and optimized the scan time of cardiac spot acquisition by utilizing NEC _density in ¹⁸ F-fluorodeoxyglucose positron emission tomography/computed tomography imaging for the diagnosis of cardiac sarcoidosis. Methods Seventy-two patients were enrolled. Using list mode data of cardiac spot acquisition, we evaluated the relationship between acquisition time and NEC _density . Based on this result and the guideline recommendation of whole-body scan (NEC _density >0.2), an appropriate NEC _density for cardiac spot acquisition was determined. The correlation between the minimum acquisition time that satisfied the determined appropriate NEC _density and the patient’s physical index (body weight, body mass index [BMI], and lean body mass) was evaluated. Results NEC _density increased linearly with longer acquisition times. For all patients, NEC _density of 10 min was 4.07 ± 0.15 times as high as that of 3 min, which was the acquisition time per one bed of whole-body scan. From the above and the guideline recommendation of whole-body scan (NEC _density >0.2), we determined that NEC _density of 0.9 was an appropriate NEC _density for cardiac spot acquisition. The correlation coefficient value between the minimum acquisition time meeting the appropriate NEC _density and body weight, BMI, or lean body mass was 0.79 (p < 0.0001), 0.83 (p < 0.0001), or 0.53 (p < 0.0001), respectively. Conclusions We defined a NEC _density of 0.9 as an appropriate NEC _density for cardiac spot acquisition. Our retrospective study using NEC _density revealed that optimization of acquisition time according to BMI could help reduce examination time for patients with small body size and homogenization of image quality.