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目的通过实验方法提出并验证CT扫描中一种新的表征受检者剂量的量。方法用笔形电离室和点电离室两种测量方法,测量单层轴扫描和多层螺旋扫描两种模式下的剂量,并对测量结果的进行比较分析。结果点电离室与笔形电离室在轴扫描模式下的剂量比值接近于1,点电离室在两种扫描模式下测得的剂量读数D_(point)和D_(air)之比为1.14,笔形电离室在两种扫描模式下测得的剂量读数DLP和CTDI之比为2.88。结论点电离室测量的剂量可以作为表征受检者剂量的有效量,笔形电离室受到长度的限制,其所测量得到的剂量学量CTDI和DLP,在多层螺旋CT扫描中用来表征有效剂量显然是不充分的。
Objective To propose and validate a new method of characterizing the dose of a subject in CT scanning through experimental methods. Methods Two kinds of measurement methods, pen ionization chamber and point ionization chamber, were used to measure the dose of single-layer axial scanning and multi-layer spiral scanning. The measurement results were compared and analyzed. Results The dose ratio of point ionization chamber to pen ionization chamber in axial scanning mode was close to 1, and the ratio of D_ (point) to D_ (air) of point ionization chamber measured in both scanning modes was 1.14. The ratio of DLP to CTDI for the dose reading of the chamber measured in both scan modes was 2.88. Conclusions The dose measured at the ionization chamber can be used as an effective dose to characterize the dose of the subject and the length of the pen ionization chamber is limited. The measured dosimetry CTDI and DLP are used to characterize the effective dose in multi-slice spiral CT scans Obviously inadequate.