In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans.
In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans.
复制标题
通过腹部/骨盆 CT 扫描对人体尸体进行体外剂量测量。
DOI：
10.1118/1.4893499
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发表时间：
2014
期刊：
影响因子：
3.8
通讯作者：
Liu,Bob
中科院分区：
文献类型：
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作者：
Zhang,Da;Padole,Atul;Li,Xinhua;Singh,Sarabjeet;Khawaja,RanishDeedarAli;Lira,Diego;Liu,Tianyu;Shi,JimQ;Otrakji,Alexi;Kalra,MannudeepK;Xu,XGeorge;Liu,Bob
目的：介绍一项在临床CT扫描仪上扫描人体尸体的辐射剂量测量研究。方法：使用放置在人体尸体（身高183 cm，体重67.5 kg）的胃、肝脏、椎旁沟、升结肠、左肾和膀胱内的高精度顶针电离室获得多点剂量测量值，该尸体的腹部/骨盆区域使用多探测器行CT重复扫描。验证了剂量计的平坦能量响应和精度，并对每个剂量计的响应中的微小差异进行了评估和校正，以获得高精度。此外，使用OSL剂量计测量扫描区域以外的放射敏感器官的皮肤剂量：右眼、甲状腺、两个乳头和右睾丸。使用了三种扫描协议，它们共享大多数扫描参数，但具有不同的kVp和mA设置：120-kVp automA、120-kVp 300 mA和100-kVp 300 mA。结果：在两个主要条件下，射线管起始角度（TSA）随机变化，这会导致重复点剂量测量的大幅波动：对于120-kVp 300 mA方案，该角度从大约110°变化到290°，导致胃、肝脏、结肠和膀胱测量的点剂量出现8%-25%的差异。当TSA的波动很小时（在5°以内），最大变异系数约为3.3%。对于120和100-kVp固定mA扫描，扫描区域中心附近四个位置的平均软组织吸收剂量分别为27.2 ± 3.3和16.5 ± 2.7 mGy。这些值与相应尺寸特定剂量估计值一致，在4%范围内。三个方案中每100 mAs组织剂量的比较显示：（1）TCM扫描中非浅表位置的剂量水平无法通过简单地用局部mA值缩放固定mA剂量来准确推断;（2）剂量和kVp之间的一般幂律关系因位置而异，幂指数范围在2.7和3.5之间。两个乳头的平均剂量测量值，这是约0.6厘米以外的规定扫描区域，范围从23至27 mGy的左乳头，并在3至20 mGy的右乳头在三个扫描协议。重复扫描的大波动也被观察到，作为大螺距（1.375）和皮肤剂量计的小活动区域的螺旋扫描的组合结果。此外，平均皮肤剂量急剧下降的距离最近的边界的扫描regions.Conclusions：这项研究揭示了复杂的CT剂量波动和变化与人体尸体。
Purpose:To present a study of radiation dose measurements with a human cadaver scanned on a clinical CT scanner.Methods:Multiple point dose measurements were obtained with high‐accuracy Thimble ionization chambers placed inside the stomach, liver, paravertebral gutter, ascending colon, left kidney, and urinary bladder of a human cadaver (183 cm in height and 67.5 kg in weight) whose abdomen/pelvis region was scanned repeatedly with a multidetector row CT. The flat energy response and precision of the dosimeters were verified, and the slight differences in each dosimeterˈs response were evaluated and corrected to attain high accuracy. In addition, skin doses were measured for radiosensitive organs outside the scanned region with OSL dosimeters: the right eye, thyroid, both nipples, and the right testicle. Three scan protocols were used, which shared most scan parameters but had different kVp and mA settings: 120‐kVp automA, 120‐kVp 300 mA, and 100‐kVp 300 mA. For each protocol three repeated scans were performed.Results:The tube starting angle (TSA) was found to randomly vary around two major conditions, which caused large fluctuations in the repeated point dose measurements: for the 120‐kVp 300 mA protocol this angle changed from approximately 110° to 290°, and caused 8% − 25% difference in the point dose measured at the stomach, liver, colon, and urinary bladder. When the fluctuations of the TSA were small (within 5°), the maximum coefficient of variance was approximately 3.3%. The soft tissue absorbed doses averaged from four locations near the center of the scanned region were 27.2 ± 3.3 and 16.5 ± 2.7 mGy for the 120 and 100‐kVp fixed‐mA scans, respectively. These values were consistent with the corresponding size specific dose estimates within 4%. The comparison of the per‐100‐mAs tissue doses from the three protocols revealed that: (1) dose levels at nonsuperficial locations in the TCM scans could not be accurately deduced by simply scaling the fix‐mA doses with local mA values; (2) the general power law relationship between dose and kVp varied from location to location, with the power index ranged between 2.7 and 3.5. The averaged dose measurements at both nipples, which were about 0.6 cm outside the prescribed scan region, ranged from 23 to 27 mGy at the left nipple, and varied from 3 to 20 mGy at the right nipple over the three scan protocols. Large fluctuations over repeated scans were also observed, as a combined result of helical scans of large pitch (1.375) and small active areas of the skin dosimeters. In addition, the averaged skin dose fell off drastically with the distance to the nearest boundary of the scanned region.Conclusions:This study revealed the complexity of CT dose fluctuation and variation with a human cadaver.