Ngaile J E, Msaki P, Kazema R
Department of Physics, University of Dar es Salaam, PO Box 35063, Dar es Salaam, Tanzania.
J Radiol Prot. 2006 Jun;26(2):213-25. doi: 10.1088/0952-4746/26/2/006. Epub 2006 May 26.
Without the knowledge of reference dose levels (RDLs) from computed tomography (CT) examinations, the optimal dose to patients undergoing CT examinations cannot be realised. The aim of this study was therefore to assess the radiation dose levels from CT examinations according to reference dose quantities proposed by the European Commission (EC) guidelines. The dosimetric quantities proposed in the EC for CT are weighted CT dose index (CTDI(w)) for a single slice and dose-length product (DLP) for a complete examination. The RDLs from five common CT examinations were obtained from eight hospitals. The RDLs in terms of CTDI(w) and DLP were estimated from measurements of CTDI in standard phantoms using typical exposure parameters. Mean values of CTDI(w) for head and lumbar spine had a range of 25-77 and 18-47 mGy, respectively, while those for chest, abdomen and pelvis had a range of about 11-25 mGy, respectively. Mean values of DLP for head, chest and abdomen had a range of 610-1684, 496-992 and 717-1428 mGy cm, respectively, while those for lumbar spine and pelvis had a range of 200-382 and 526-1302 mGy cm, respectively. Wide variations of mean CTDI(w) and DLP values among hospitals observed for similar CT examinations were mainly attributed to the variations of CT scanning protocols and scanner types. The mean CTDI(w) values per examination for almost all hospitals were below proposed RDLs, while the mean DLP values per examination were almost all above the proposed RDLs for all except one hospital. These were mainly influenced by the large scan length used in Tanzanian hospitals. In order to achieve the required level of dose for establishment of the national RDLs, it was concluded that further investigation of optimization of scanning protocols is needed.
如果不了解计算机断层扫描（CT）检查的参考剂量水平（RDL），就无法实现对接受CT检查患者的最佳剂量。因此，本研究的目的是根据欧盟委员会（EC）指南提出的参考剂量量来评估CT检查的辐射剂量水平。EC为CT提出的剂量学量是单一层面的加权CT剂量指数（CTDI(w)）和完整检查的剂量长度乘积（DLP）。从八家医院获取了五项常见CT检查的RDL。通过使用典型曝光参数在标准体模中测量CTDI来估算CTDI(w)和DLP方面的RDL。头部和腰椎的CTDI(w)平均值范围分别为25 - 77和18 - 47 mGy，而胸部、腹部和骨盆的CTDI(w)平均值范围分别约为11 - 25 mGy。头部、胸部和腹部的DLP平均值范围分别为610 - 1684、496 - 992和717 - 1428 mGy cm，而腰椎和骨盆的DLP平均值范围分别为200 - 382和526 - 1302 mGy cm。在相似的CT检查中，各医院间CTDI(w)和DLP平均值的广泛差异主要归因于CT扫描方案和扫描仪类型的差异。几乎所有医院每项检查的CTDI(w)平均值均低于建议的RDL，而除一家医院外，每项检查的DLP平均值几乎均高于建议的RDL。这主要受坦桑尼亚医院使用的大扫描长度影响。为了达到建立国家RDL所需的剂量水平，得出结论认为需要进一步研究扫描方案的优化。
