RT Journal Article
SR Electronic
T1 Feasibility of short acquisition for pediatric FDG-PET/CT scan using the SiPM-PET/CT system
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 3031
OP 3031
VO 62
IS supplement 1
A1 Owaki, Yoshiki
A1 Minamishima, Kazuya
A1 Nakajima, Kiyotaka
YR 2021
UL http://jnm.snmjournals.org/content/62/supplement_1/3031.abstract
AB 3031Objectives: In recent years, radiopharmaceutical dosage in pediatric nuclear medicine examinations have been optimized globally. However, imaging methods for pediatric positron emission tomography (PET)/computed tomography (CT) examinations have not been optimized. Appropriate selection of the imaging method not only affects the accurate diagnosis in pediatric patients, but also affects the amount of sedation used, which is closely related to the examination time. In this study, we developed original phantoms for evaluating image quality in pediatric patients and validated the appropriate acquisition and image reconstruction conditions for each age group. Methods: The original phantom was developed to conform to the thickness and width of the torso in each age group (neonates, 1-year-olds, 5-year-olds, 10-year-olds, 15-year-olds, and adults) as defined by the American Association of Physicists in Medicine “Image Gently”, and to reflect the shape of The National Electrical Manufacturers Association (NEMA) international Electrotechnical Commission (IEC) body phantom. The ratio of hot spheres to background radioactivity was 4:1, and the radioactivity concentration was adjusted according to the Japanese consensus guidelines for appropriate implementation of pediatric nuclear medicine examinations. Each phantom was scanned using Lu2SiO5- Silicon photomultiplier -PET/CT system. Image reconstruction was performed using the ordered subset expectation maximization + point spread function + time of flight algorithm, with iteration varying from 1 to 5 and Gaussian filter whose full width at half maximum (FWHM) ranged from 0 to 9 mm. We evaluated the root mean square error (RMSE) as an assessment/function of the standardized uptake value of each hot sphere, the background variability (N10 mm), and the % contrast of the hot sphere (QH, 10 mm / N10 mm) to determine the optimal reconstruction parameters. We also examined the appropriate acquisition time for each phantom in conjunction with the noise equivalent counts (NEC) to these indices. Results: In phantom sizes below 10 years of age, N10 mm and QH, 10 mm/N10 mm guideline values were satisfied in all reconstruction conditions. In contrast, in 15-year-old and adult phantoms, N10 mm did not satisfy the guideline values in conditions with a high number of iterations and low FWHM width of the Gaussian filter. The minimum RMSE was obtained by setting the half-width of the Gaussian filter to 0-2 mm for iteration 1 or 2 and by setting the half-width of the Gaussian filter to 3-4 mm for iteration 3 or more. Comparison of each phantom size at the same acquisition time demonstrated that larger phantom size and shorter acquisition time tended to have higher N10 mm and RMSE. Acquisition times that satisfied the guideline values for N10 mm and QH, 10 mm/N10 mm were 30 s for neonate and 1-year-old phantoms, 45 s for 5- and 10-year-old phantoms, 60 s for 15-year-old phantoms, and 105 s for adult phantoms. In contrast, in the NEC results, phantom sizes below the 5-year-old phantom did not satisfy the guideline values even with acquisition time of 180 s. Conclusions: We recommend reconstruction with an iteration number of 2 or 3 and FWHM width of 0-3 mm for the Gaussian filter. Good PET images can be obtained with short acquisition times when the examination is performed under appropriate reconstruction conditions. This result may lead to a reduction in unnecessarily prolonged acquisition time. Acknowledgments: The authors thank the staff of the Division of Nuclear Medicine at the Department of Radiology for their valuable support.