中文摘要：

目的研究儿童胸部CT扫描时腹部的屏蔽方法及其效果。方法用美国CIRS公司生产的5岁儿童体模代替儿童受检者，在腹部内布放热释光剂量计LiF（Mg，Cu，P），按儿童胸部CT扫描的通常程序对体模进行扫描，测量在无屏蔽、用铅衣覆盖和用铅衣包裹时腹腔内主要器官与组织的剂量。结果儿童胸部CT扫描时，腹腔内部分器官的吸收剂量可达到数mGy。3种扫描之间，相同位置处的剂量值差异有统计学意义（x2=16．00，P〈0．05）；正面覆盖和包裹屏蔽方式之间的剂量值差异有统计学意义（Z=一2．52，P〈0．05）。较之于无屏蔽措施，采用0．35mm铅衣包裹腹部，可分别降低睾丸和结肠的剂量71．2％和42．3％，采用同样当量铅衣铺盖腹部剂量可降低55．9％和26．1％。结论开展儿童胸部CT扫描时，使用铅防护衣可有效屏蔽腹部受照，对性腺和结肠的防护具有重要作用，特别是包裹式的屏蔽措施值得推荐。

英文摘要：

Objective To investigate the methods and effects of abdominal and pelvic shielding for pediatric chest CT examinations. Methods The 705-D phantom made by Computerized Imaging Reference Systems （CIRS） was used to replace a 5-year-old child, thermoluminescent dosimeters were set in the abdomen and pelvis to measure the organ and tissue doses. Chest scans were conducted with the routine protocol for pediatric chest CT examinations. Doses to main organs and tissues in the abdomen and pelvis were measured after chest CT scans without lead apron, with lead apron covering anterior of the abdomen and pelvis and with apron wrapping same part, respectively. Results Absorbed doses to some abdominal organs near the irradiation field were up to several mGy in a procedure of pediatric chest CT examination. There were statistically significant differences among the dose values for three different scans at the same location （ X2 = 16.00 ,P 〈 O. 05 ）. Statistically significant difference was also found between the dose values for scans, which were measured with wrapping and covering approaches （ Z -- - 2.52, P 〈 0.05 ）. Compared to the doses in the condition of no shielding, the doses in testis and colon reduced by 71.2% and 42.3% , respectively, if the abdomen and pelvis was wrapped with a lead apron （0.35 mm Pb） , and reduced by 55.9% and 26.1% , respectively, if the same lead apron was used to cover the anterior of the abdomen and pelvis. Conclusions In pediatric chest CT examinations, the use of a lead apron can effectively shield the abdomen and pelvis, and plays an important role in protection of the gonad and colon. The wrapping measure is worth being recommended.