治疗前（124）I PET(/CT) 剂量学证实，分化型甲状腺癌放射性碘治疗中，每给予（131）I 活度的唾液腺平均吸收剂量较低。
Pre-therapeutic (124)I PET(/CT) dosimetry confirms low average absorbed doses per administered (131)I activity to the salivary glands in radioiodine therapy of differentiated thyroid cancer.
机构信息
Klinik für Nuklearmedizin, Universität Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany.
出版信息
Eur J Nucl Med Mol Imaging. 2010 May;37(5):884-95. doi: 10.1007/s00259-009-1351-2. Epub 2010 Jan 13.
PURPOSE
Salivary gland impairment following high activity radioiodine therapy of differentiated thyroid cancer (DTC) is a severe side effect. Dosimetric calculations using planar gamma camera scintigraphy (GCS) with (131)I and ultrasonography (US) provided evidence that the average organ dose per administered (131)I activity (ODpA) is too low to account for observed radiation damages to the salivary glands. The objective of this work was to re-estimate the ODpA using (124)I PET(/CT) as a more reliable approach than (131)I GCS/US.
METHODS
Ten DTC patients underwent a series of six (or seven) PET scans and one PET/CT scan after administration of approximately 23 MBq (124)I-iodide. Volumes of interest (VOIs) drawn on the CT and serial PET images were used to determine the glandular volumes and the imaged (124)I activities. To enable identical VOIs to be drawn on serial PET images, each PET was co-registered with the CT image. To correct for partial volume effect and for the artificial bias in the activity concentration due to cascading gamma coincidences occurring in (124)I decay, the imaged activity was effectively corrected using isovolume recovery coefficients (RCs) based on recovery phantom measurements. A head-neck phantom, which contained (124)I-filled spheres, was manufactured to validate the isovolume recovery correction method with a realistic patient-based phantom geometry and for a range of activity concentration regimes. The mean+/-standard deviation (range) ODpA projected for (131)I was calculated using the absorbed dose fraction method.
RESULTS
The ODpAs (in Gy/GBq) for the submandibular and parotid glands were 0.32 +/- 0.13 (0.18-0.55) and 0.31 +/- 0.10 (0.13-0.46), respectively. No significant differences (p> 0.2) in the mean ODpA between (124)I PET(/CT) and (131)I GCS/US dosimetry was found. The validation experiment showed that the percentage deviations between RC-corrected and true activity concentrations were <10%.
CONCLUSION
(124)I PET(/CT) dosimetry also corroborates the low ODpAs to the salivary glands. A voxel-based calculation taking into account the nonuniform activity distributions in the glands is necessary to possibly explain the radiation-induced salivary gland damage.
目的
分化型甲状腺癌（DTC）患者经高活性放射性碘治疗后发生唾液腺损伤是一种严重的副作用。使用（131）I平面伽马相机闪烁显像（GCS）和超声（US）进行的剂量计算提供的证据表明，每给予（131）I 活性的器官剂量平均值（ODpA）过低，无法解释观察到的对唾液腺的辐射损伤。本工作的目的是使用（124）I PET（/CT）重新估算 ODpA，因为这是一种比（131）I GCS/US 更可靠的方法。
方法
10 例 DTC 患者在给予约 23MBq（124）I-碘化物后进行了一系列 6（或 7）次 PET 扫描和 1 次 PET/CT 扫描。在 CT 和连续 PET 图像上绘制的感兴趣区（VOI）用于确定腺体体积和成像的（124）I 活性。为了能够在连续的 PET 图像上绘制相同的 VOI，将每个 PET 与 CT 图像进行配准。为了校正部分容积效应以及由于（124）I 衰变中级联伽马符合引起的活性浓度的人为偏差，使用基于回收体模测量的等容恢复系数（RC）对成像的活性进行了有效校正。制造了一个头颈部体模，其中包含（124）I 填充的球体，该体模基于具有实际患者体模几何形状和一系列活性浓度范围的体模验证了等容恢复校正方法。使用吸收剂量分数法计算（131）I 的平均标准偏差（范围）ODpA。
结果
下颌下腺和腮腺的 ODpA（以 Gy/GBq 计）分别为 0.32+/-0.13（0.18-0.55）和 0.31+/-0.10（0.13-0.46）。未发现（124）I PET（/CT）和（131）I GCS/US 剂量测定之间的平均 ODpA 存在显著差异（p>0.2）。验证实验表明，RC 校正后的活性浓度与真实活性浓度之间的百分比偏差<10%。
结论
（124）I PET（/CT）剂量也证实了唾液腺的 ODpA 较低。需要基于腺体中不均匀的活性分布进行体素计算，以可能解释放射性引起的唾液腺损伤。
Zotero 插件