Department of Radiology, University of Washington, Seattle, Washington, USA.
J Nucl Med. 2011 Jul;52(7):1028-34. doi: 10.2967/jnumed.110.086579. Epub 2011 Jun 16.
Pediatric (18)F-FDG dosing and acquisition durations are generally based on coarse extrapolation from adult guidelines. This study sought to determine whether shorter acquisition durations or a lower (18)F-FDG injected activity could be used for pediatric (18)F-FDG PET/CT examinations while maintaining diagnostic utility. Reduction of overall scan time potentially reduces motion artifacts, improves patient comfort, and decreases length of sedation. Alternatively, decreased (18)F-FDG dose minimizes radiation risk.
Fourteen whole-body (18)F-FDG PET/CT examinations were performed on 13 patients (weight, 13-109 kg; age range, 1-23 y) with a weight-based injected activity (5.3 MBq/kg [0.144 mCi/kg]), fixed acquisition durations (3 min/field of view [FOV] if < 22 kg, 5 min/FOV if > 22 kg), and list-mode acquisition. For each examination, the list-mode data were truncated to form multiple datasets with shorter acquisition durations down to a minimum of 1 min/FOV (i.e., 1, 2, 3, 4, and 5 min/FOV data were formed from single 5 min/FOV acquisition). Fifty-six image volumes were generated, randomized, and reviewed in a masked manner with corresponding CT image volumes by 5 radiologists. Overall, subjective adequacy and objective lesion detection accuracy by body region were evaluated.
All examinations with maximum acquisition duration were graded as adequate and were used as the reference standard for detection accuracy. For patients less than 22 kg, 1 of the 3 PET/CT examinations was graded as inadequate for clinical tasks when acquisition duration was reduced to 2 min/FOV, and all examinations were graded as inadequate when reduced to 1 min/FOV. For patients more than 22 kg, all 3-5 min/FOV studies were graded as adequate, and 2 of the 9 studies were graded as inadequate for 2 min/FOV studies. Lesion detection accuracy was perfect for acquisition times between 3 min/FOV and 5 min/FOV for all regions of the body. However, lesion detection became less accurate when imaging acquisition time was reduced more than 40%.
Evaluation of image volumes generated from simulated shorter acquisition durations suggests that imaging times for larger patients (>22 kg) can be reduced from 5 min/FOV to 3 min/FOV without a loss of diagnostic utility. Using decreased acquisition times as a surrogate for (18)F-FDG dose, (18)F-FDG dose can be reduced by approximately 40% when all patients were scanned for 5 min/FOV.
儿科（18）F-FDG 的给药和采集时间通常是基于成人指南的粗略推断。本研究旨在确定在保持诊断效用的同时，是否可以使用较短的采集时间或较低的（18）F-FDG 注射活性进行儿科（18）F-FDG PET/CT 检查。减少总扫描时间可以减少运动伪影，提高患者舒适度，并缩短镇静时间。或者，减少（18）F-FDG 剂量可以最大限度地降低辐射风险。
对 13 名患者（体重 13-109 公斤；年龄范围 1-23 岁）进行了 14 次全身（18）F-FDG PET/CT 检查，采用基于体重的注射活性（5.3MBq/kg[0.144mCi/kg]）、固定采集时间（<22 公斤时为 3 分钟/视野[FOV]，>22 公斤时为 5 分钟/FOV）和列表模式采集。对于每次检查，列表模式数据被截断以形成多个数据集，采集时间缩短至最短 1 分钟/FOV（即，单个 5 分钟/FOV 采集可形成 1、2、3、4 和 5 分钟/FOV 数据）。生成了 56 个图像体积，以随机和屏蔽方式与相应的 CT 图像体积一起由 5 名放射科医生进行评估。总体上，评估了按身体部位划分的主观充分性和客观病变检测准确性。
所有采用最大采集时间的检查均被评为充分，并被用作检测准确性的参考标准。对于体重小于 22 公斤的患者，当采集时间减少到 2 分钟/FOV 时，有 3 次 PET/CT 检查中有 1 次被评为不适合临床任务，当采集时间减少到 1 分钟/FOV 时，所有检查均被评为不适合。对于体重超过 22 公斤的患者，所有 3-5 分钟/FOV 研究均被评为充分，9 次 2 分钟/FOV 研究中有 2 次被评为不充分。对于所有身体部位，采集时间在 3 分钟/FOV 至 5 分钟/FOV 之间时，病变检测准确性为完美。然而，当成像采集时间减少超过 40%时，病变检测的准确性会降低。
对模拟较短采集时间生成的图像体积进行评估表明，对于较大的患者（>22 公斤），可以将采集时间从 5 分钟/FOV 减少到 3 分钟/FOV，而不会降低诊断效用。使用较短的采集时间作为（18）F-FDG 剂量的替代物，当所有患者均扫描 5 分钟/FOV 时，（18）F-FDG 剂量可减少约 40%。
