腹部/盆腔X线检查期间儿童和成人使用性腺屏蔽可实现的剂量降低：蒙特卡罗模拟

Somasundaram Elanchezhian, Brady Samuel L, Strauss Keith J

Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.

Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.

Med Phys. 2020 Nov;47(11):5514-5522. doi: 10.1002/mp.14495. Epub 2020 Oct 13.

PURPOSE

Recently, medical professionals have reconsidered the practice of routine gonadal shielding for radiographic examinations. The objective of this study was to evaluate the gonadal dose reduction achievable with gonadal shields in the primary beam during abdominal/pelvic radiographic examinations under ideal and non-ideal shielding placement.

METHODS

CT scans of CIRS anthropomorphic phantoms were used to perform voxelized Monte Carlo simulations of the photon transport during abdominal/pelvic radiographic examinations with standard filtration and 0.1 mm Cu + 1 mm Al added filtration to estimate gonadal doses for an adult, 5 yr old, and newborn phantom with and without gonadal shields. The reduction in dose when the shields were not placed at the ideal locations was also evaluated. The ratio of the number of scattered-to-primary photons (SPR) across the anteroposterior (AP) dimension of the phantoms was also reported.

RESULTS

The simulated dose reduction with ideal shielding placement for the testes and ovaries ranged from 80% to 90% and 55% to 70% respectively. For children, a misalignment of the shield to the gonad of 4 cm reduced the measured dose reduction to the gonads to <10%. For adults, this effect did not occur until the misalignment increased to ~6 cm. Effects of dose reduction with and without the gonadal shields properly placed were similar for standard filtration and added filtration. SPR at the level of the testes was consistently <1 for all phantoms. SPR for ovaries was ~1.5 for the adult and 5-yr old, and ~1 for the newborn phantom.

CONCLUSION

Dose reduction with ideal alignment of the simulated gonadal shield to the gonads in this study was greater for the testes than the ovaries; both reductions were substantial. However, the dose reductions were greatly reduced (to <10%) for both sexes with misalignment of the gonads to the shields by 4 cm for children and 6 cm for adults.

目的

最近，医学专业人员重新审视了放射检查中常规性腺屏蔽的做法。本研究的目的是评估在理想和非理想屏蔽放置情况下，腹部/盆腔放射检查期间性腺屏蔽在原射线束中可实现的性腺剂量降低情况。

方法

使用CIRS人体模型的CT扫描对腹部/盆腔放射检查期间的光子传输进行体素化蒙特卡罗模拟，采用标准过滤以及添加0.1毫米铜+1毫米铝过滤，以估计有和没有性腺屏蔽时成人、5岁儿童和新生儿模型的性腺剂量。还评估了屏蔽未放置在理想位置时的剂量降低情况。还报告了模型前后径上散射光子与原光子数量之比（SPR）。

结果

模拟的理想屏蔽放置情况下，睾丸和卵巢的剂量降低分别为80%至90%和55%至70%。对于儿童，屏蔽与性腺错位4厘米会使测量到的性腺剂量降低至<10%。对于成人，直到错位增加到约6厘米才会出现这种情况。标准过滤和添加过滤情况下，性腺屏蔽放置正确与否时的剂量降低效果相似。所有模型在睾丸水平的SPR始终<1。成人和5岁儿童卵巢的SPR约为1.5，新生儿模型约为1。