Phelps Andrew S, Gould Robert G, Courtier Jesse L, Marcovici Peter A, Salani Christina, MacKenzie John D
Department of Radiology & Biomedical Imaging, UCSF Benioff Children's Hospital, University of California, San Francisco, California, USA.
Department of Radiology & Biomedical Imaging, UCSF Benioff Children's Hospital, University of California, San Francisco, California, USA.
J Med Imaging Radiat Sci. 2016 Jun;47(2):171-177. doi: 10.1016/j.jmir.2015.12.082. Epub 2016 Feb 6.
Fluoroscopy technologists routinely place a lead shield between the x-ray table and the patient's gonads, even if the gonads are not directly in the x-ray field. Internal scatter radiation is the greatest source of radiation to out-of-field body parts, but a shield placed between the patient and the x-ray source will not block internal scatter. Prior nonfluoroscopy research has shown that there is a small reduction in radiation dose when shielding the leakage radiation that penetrates through the collimator shutters. The goal of this in vitro study was to determine if there was any radiation dose reduction when shielding leakage radiation during fluoroscopy.
This was an in vitro comparison study of radiation doses using different collimation and shielding strategies during fluoroscopy. Ionization chamber measurements were obtained during fluoroscopy of an acrylic block with and without collimation and shielding. Ionization chamber readings were taken in-field at 0 cm and out-of-field at 7.5, 10, and 12.5 cm from beam center.
Collimation reduced 87% of the out-of-field radiation dose, and the remaining measurable dose was because of internal scatter. The radiation dose contribution from leakage radiation was negligible, as there was not any measurable radiation dose difference when shielding leakage radiation, with P value of .48.
These results call into question the clinical utility of routinely shielding out-of-field body parts during fluoroscopy.
透视技师通常会在X射线检查床和患者性腺之间放置铅屏蔽物，即使性腺并不直接处于X射线照射野内。体内散射辐射是照射野外身体部位的最大辐射源，但置于患者与X射线源之间的屏蔽物并不能阻挡体内散射。先前的非透视研究表明，屏蔽透过准直器百叶窗的泄漏辐射时，辐射剂量会有小幅降低。本体外研究的目的是确定在透视期间屏蔽泄漏辐射时是否能降低辐射剂量。
这是一项关于透视期间使用不同准直和屏蔽策略的辐射剂量的体外对比研究。在对一块丙烯酸块进行透视时，分别在有和没有准直及屏蔽的情况下进行电离室测量。电离室读数在射野内距射束中心0厘米处以及射野外距射束中心7.5、10和12.5厘米处获取。
准直减少了87%的射野外辐射剂量，剩余可测量剂量是由于体内散射。泄漏辐射对辐射剂量的贡献可忽略不计，因为屏蔽泄漏辐射时没有任何可测量的辐射剂量差异，P值为0.48。
这些结果对透视期间常规屏蔽照射野外身体部位的临床实用性提出了质疑。
