使用DICOM元数据估算数字X线摄影检查中的儿科入射皮肤剂量：一种质量保证工具。

Brady S L, Kaufman R A

Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee 38105.

Med Phys. 2015 May;42(5):2489-97. doi: 10.1118/1.4918324.

PURPOSE

To develop an automated methodology to estimate patient examination dose in digital radiography (DR) imaging using DICOM metadata as a quality assurance (QA) tool.

METHODS

Patient examination and demographical information were gathered from metadata analysis of DICOM header data. The x-ray system radiation output (i.e., air KERMA) was characterized for all filter combinations used for patient examinations. Average patient thicknesses were measured for head, chest, abdomen, knees, and hands using volumetric images from CT. Backscatter factors (BSFs) were calculated from examination kVp. Patient entrance skin air KERMA (ESAK) was calculated by (1) looking up examination technique factors taken from DICOM header metadata (i.e., kVp and mA s) to derive an air KERMA (k air) value based on an x-ray characteristic radiation output curve; (2) scaling k air with a BSF value; and (3) correcting k air for patient thickness. Finally, patient entrance skin dose (ESD) was calculated by multiplying a mass-energy attenuation coefficient ratio by ESAK. Patient ESD calculations were computed for common DR examinations at our institution: dual view chest, anteroposterior (AP) abdomen, lateral (LAT) skull, dual view knee, and bone age (left hand only) examinations.

RESULTS

ESD was calculated for a total of 3794 patients; mean age was 11 ± 8 yr (range: 2 months to 55 yr). The mean ESD range was 0.19-0.42 mGy for dual view chest, 0.28-1.2 mGy for AP abdomen, 0.18-0.65 mGy for LAT view skull, 0.15-0.63 mGy for dual view knee, and 0.10-0.12 mGy for bone age (left hand) examinations.

CONCLUSIONS

A methodology combining DICOM header metadata and basic x-ray tube characterization curves was demonstrated. In a regulatory era where patient dose reporting has become increasingly in demand, this methodology will allow a knowledgeable user the means to establish an automatable dose reporting program for DR and perform patient dose related QA testing for digital x-ray imaging.

目的

开发一种自动化方法，利用DICOM元数据作为质量保证（QA）工具来估算数字X线摄影（DR）成像中的患者检查剂量。

方法

通过对DICOM头数据进行元数据分析来收集患者检查和人口统计学信息。对用于患者检查的所有滤过器组合的X线系统辐射输出（即空气比释动能）进行了表征。使用CT容积图像测量头部、胸部、腹部、膝盖和手部的平均患者厚度。根据检查管电压计算反向散射因子（BSF）。患者入口皮肤空气比释动能（ESAK）的计算方法为：（1）查找从DICOM头元数据中获取的检查技术参数（即管电压和毫安秒），根据X线特征辐射输出曲线得出空气比释动能（k空气）值；（2）用BSF值对k空气进行缩放；（3）根据患者厚度对k空气进行校正。最后，通过将质能衰减系数比乘以ESAK来计算患者入口皮肤剂量（ESD）。对本机构常见的DR检查计算了患者ESD：双能胸部、前后位（AP）腹部、侧位（LAT）颅骨、双能膝盖和骨龄（仅左手）检查。

结果

共对3794例患者计算了ESD；平均年龄为11±8岁（范围：2个月至55岁）。双能胸部的平均ESD范围为0.19 - 0.42 mGy，AP腹部为0.28 - 1.2 mGy，LAT位颅骨为0.18 - 0.65 mGy，双能膝盖为0.15 - 0.63 mGy，骨龄（左手）检查为0.10 - 0.12 mGy。