Soares Machado J, Tran-Gia J, Schlögl S, Buck A K, Lassmann M
Department of Nuclear Medicine, University Hospital Würzburg, Oberdürrbacher Str. 6, 97080, Würzburg, Germany.
EJNMMI Res. 2018 Feb 2;8(1):10. doi: 10.1186/s13550-017-0356-2.
Renal scans are among the most frequent exams performed on infants and toddlers. Due to the young age, this patient group can be classified as a high-risk group with a higher probability for developing stochastic radiation effects compared to adults. As there are only limited data on biokinetics and dosimetry in this patient group, the aim of this study was to reassess the dosimetry and the associated radiation risk for infants undergoing Tc-MAG3 renal scans based on a retrospective analysis of existing patient data. Consecutive data were collected from 20 patients younger than 20 months (14 males; 6 females) with normal renal function undergoing Tc-MAG3 scans. To estimate the patient-specific organ activity, a retrospective calibration was performed based on a set of two 3D-printed infant kidneys filled with known activities. Both phantoms were scanned at different positions along the anteroposterior axis inside a water phantom, providing depth- and size-dependent attenuation correction factors for planar imaging. Time-activity curves were determined by drawing kidney, bladder, and whole-body regions-of-interest for each patient, and subsequently applying the calibration factor for conversion of counts to activity. Patient-specific time-integrated activity coefficients were obtained by integrating the organ-specific time-activity curves. Absorbed and effective dose coefficients for each patient were assessed with OLINDA/EXM for the provided newborn and 1-year-old model. The risk estimation was performed individually for each of the 20 patients with the NCI Radiation Risk Assessment Tool.
The mean age of the patients was 7.0 ± 4.5 months, with a weight between 5 and 12 kg and a body size between 60 and 89 cm. The injected activities ranged from 12 to 24 MBq of Tc-MAG3. The patients' organ-specific mean absorbed dose coefficients were 0.04 ± 0.03 mGy/MBq for the kidneys and 0.27 ± 0.24 mGy/MBq for the bladder. The mean effective dose coefficient was 0.02 ± 0.02 mSv/MBq. Based on the dosimetry results, an evaluation of the excess lifetime risk for the development of radiation-induced cancer showed that the group of newborns has a risk of 16.8 per 100,000 persons, which is about 12% higher in comparison with the 1-year-old group with 14.7 per 100,000 persons (all values are given as mean plus/minus one standard deviation except otherwise specified).
In this study, we retrospectively derived new data on biokinetics and dosimetry for infants with normal kidney function after undergoing renal scans with Tc-MAG3. In addition, we analyzed the associated age- and gender-specific excess lifetime risk due to ionizing radiation. The radiation-associated stochastic risk increases with the organ doses, taking age- and gender-specific influences into account. Overall, the lifetime radiation risk associated with the Tc-MAG3 scans is very low in comparison to the general population risk for developing cancer.
肾脏扫描是婴幼儿最常进行的检查之一。由于年龄小，与成年人相比，该患者群体可被归类为高风险群体，发生随机辐射效应的可能性更高。由于该患者群体中关于生物动力学和剂量学的数据有限，本研究的目的是基于对现有患者数据的回顾性分析，重新评估接受锝-巯基乙酰三甘氨酸（Tc-MAG3）肾脏扫描的婴儿的剂量学及相关辐射风险。收集了20例年龄小于20个月（14例男性；6例女性）、肾功能正常且接受Tc-MAG3扫描的患者的连续数据。为了估计患者特定器官的活度，基于一组两个填充有已知活度的3D打印婴儿肾脏进行回顾性校准。两个体模在水模内沿前后轴的不同位置进行扫描，为平面成像提供深度和尺寸依赖的衰减校正因子。通过为每位患者绘制肾脏、膀胱和全身感兴趣区来确定时间-活度曲线，随后应用校准因子将计数转换为活度。通过对器官特定的时间-活度曲线进行积分获得患者特定的时间积分活度系数。使用OLINDA/EXM为提供的新生儿和1岁模型评估每位患者的吸收剂量系数和有效剂量系数。使用美国国立癌症研究所（NCI）辐射风险评估工具对20例患者中的每一例进行个体风险估计。
患者的平均年龄为7.0±4.5个月，体重在5至12千克之间，身高在60至89厘米之间。注射的Tc-MAG3活度范围为12至24兆贝可。患者器官特定的平均吸收剂量系数，肾脏为0.04±0.03毫戈瑞/兆贝可，膀胱为0.27±0.24毫戈瑞/兆贝可。平均有效剂量系数为0.02±0.02毫希沃特/兆贝可。基于剂量学结果，对辐射诱发癌症的终生超额风险评估表明，新生儿组每10万人中有16.8例的风险，与每10万人中有14.7例的1岁组相比高出约12%（除另有说明外，所有值均以平均值加减一个标准差给出）。
在本研究中，我们回顾性地得出了肾功能正常的婴儿在接受Tc-MAG3肾脏扫描后的生物动力学和剂量学新数据。此外，我们分析了由于电离辐射导致的相关年龄和性别特异性终生超额风险。考虑到年龄和性别特异性影响，辐射相关的随机风险随器官剂量增加。总体而言，与Tc-MAG3扫描相关的终生辐射风险与一般人群患癌症的风险相比非常低。
