脑灌注 CT 中皮肤和眼部晶状体的峰值剂量：基于 CTDI 和蒙特卡罗的估算。

Peak skin and eye lens radiation dose from brain perfusion CT: CTDI and Monte Carlo based estimations.

机构信息

Department of Imaging and Pathology, Division of Medical Physics & Quality Assessment, KU Leuven, Herestraat 49 box 7003, 3000, Leuven, Belgium.

出版信息

Eur J Radiol. 2020 May;126:108950. doi: 10.1016/j.ejrad.2020.108950. Epub 2020 Mar 10.

DOI:10.1016/j.ejrad.2020.108950

PMID:32199141

Abstract

PURPOSE

To quantify the eye lens, peak skin and brain doses associated with head CT perfusion exam by means of thermoluminescent dosimeters (TLDs) measurements in a cadaver and compare them to Monte Carlo (MC) dose estimations as well as to the CTDI.

METHOD

18 TLDs were inserted in the brain, skin, and eye lenses of a female cadaver head, who underwent a CT brain perfusion scan using a Siemens Definition Flash. The table-toggling protocol used 80 kVp, 200 mAs, 32 × 1.2 mm collimation and 30 sequences. From the CT images, a voxel model was created. Doses were calculated with a MC framework (EGSnrc) and compared to TLD measurements. TLD measurements were also compared to the displayed CTDI.

RESULTS

The average measured doses were: 185 mGy for the eyes lenses, 107 mGy for the skin, 172 mGy for the brain and 273 mGy for the peak skin. The reported CTDI of 259 mGy overestimated the averaged organ doses but not the peak skin dose. MC estimated organ doses were 147 mGy for the eyes (average), 104 mGy for the skin and 178 mGy for the brain (-20 %, -3% and 4% difference respect to the TLDs measurements, respectively).

CONCLUSIONS

CTDI remains a conservative metric for average brain, skin and eyes lenses doses. For accurate eye lens and skin dose estimates MC simulations can be used. CTDI should be used with caution as it was of the same order of magnitude as the peak skin dose for this protocol and this particular CT scanner.

摘要

目的

通过在尸体上使用热释光剂量计（TLD）测量来量化头部 CT 灌注检查相关的晶状体、峰值皮肤和脑剂量，并将其与蒙特卡罗（MC）剂量估算以及 CT 剂量指数（CTDI）进行比较。

方法

将 18 个 TLD 插入女性尸体头部的大脑、皮肤和晶状体中，该尸体接受了西门子 Definition Flash 进行的 CT 脑灌注扫描。使用的表切换协议为 80 kVp、200 mAs、32×1.2 mm 准直和 30 个序列。从 CT 图像创建了体素模型。使用 MC 框架（EGSnrc）计算剂量，并将其与 TLD 测量值进行比较。还将 TLD 测量值与显示的 CTDI 进行比较。

结果

平均测量剂量为：晶状体 185 mGy、皮肤 107 mGy、大脑 172 mGy 和峰值皮肤 273 mGy。报告的 CTDI 为 259 mGy，高估了平均器官剂量，但未高估峰值皮肤剂量。MC 估计的器官剂量为：晶状体 147 mGy（平均值）、皮肤 104 mGy 和大脑 178 mGy（分别与 TLD 测量值相差-20%、-3%和 4%）。