Comparison of SSDE values based on effective diameter and water equivalent diameter in head CT examination of adult patients
10.3760/cma.j.issn.0254-5098.2018.07.010
- VernacularTitle: 基于有效直径和水当量直径计算头颅CT扫描体型特异性剂量估算值的对比研究
- Author:
Jian XU
1
;
Dewang MAO
;
Jianguo XU
;
Huawei XIAO
;
Qiaowei SONG
;
Fuhua CHEN
Author Information
1. Department of Radiology, Zhejiang Provincial People′s Hospital, People′s Hospital of Hangzhou Medical College, Hangzhou 310014, China
- Publication Type:Journal Article
- Keywords:
Head;
CTDIvol;
Effective diameter;
Water equivalent diameter;
Size-specific dose estimate
- From:
Chinese Journal of Radiological Medicine and Protection
2018;38(7):535-540
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To compare and quantify the differences in size-specific dose estimates (SSDE) obtained by effective diameter and water-equivalent diameter from the central slice of the scan range in head CT examination.
Methods:A total of 111 consecutive adult patients who underwent head CT examination were enrolled in this study. All of CTDIvol values in the dose report were documented. The dataset was assigned into group A and group B, based on the individual size-dependent conversion factors (f) of effective diameter (deff) and water-equivalent diameter (dw) at the central slice multiplied by normalized volume computed tomography dose index (CTDIvol ) respectively. Body size, f and SSDE were calculated. With SSDEgross served as the reference level, the performance of SSDEdeff and SSDEdw was evaluated.
Results:Statistically significant differences were found in body size (t=47.587, P<0.05) and f(z=-9.242, P<0.05) between group A and group B. Statistically significant difference also existed in SSDE (t=-46.687, P<0.05), (56.20±2.66) and (53.49±2.48) mGy for group A and group B respectively. Strongly positive correlation was shown in body size (r=0.873, R2 =0.761) and SSDE (r=0.974, R2 =0.949) between group A and group B(all P<0.05). Positive correlation was also found between SSDEdeff and SSDEgross(r=0.900, R2 =0.809), SSDEdw and SSDEgross (r=0.904, R2 =0.817, all P<0.05). Mean absolute difference was 2.34 and 0.78 mGy, for SSDEdeff vs. SSDEgross and SSDEdw vs. SSDEgross respectively; mean absolute relative difference was 4.38%, 1.40%; root mean square difference was 1.17 mGy (2.17%), 1.06 mGy (1.91%). Interquartile range and full range of SSDEdeff and SSDEdw were 3.22 vs. 2.39 mGy, 13.65 vs. 12.48mGy, respectively. A less degree of variation was observed in SSDEdw than that in SSDEdeff.
Conclusions:SSDEdw values based on the water-equivalent diameter at the central slice of the scan range got better agreement with those derived from all slices, which could serve as a simpler and more valid indicator to represent the average value of size-specific dose estimates of the whole scan range in head CT examination.
