Acquisition Of Size-Specific Dose Estimates For Abdominal Computed Tomography Examination In Nigeria: A Preliminary Study Using A Water Equivalent Diameter

Abstract

Background

Size-specific dose estimates is an important metric for personalizing dose measurements during abdominal computed tomography (CT) examination. This study aimed to establish patient size-specific dose data as a guide for dose monitoring of abdominal computed tomography examinations among Nigerians.

Methods

Abdominal CT images of adult subjects obtained from two CT scanners - a light speed VCT –ZTe; (GE Healthcare) 16 – Slice and a Brivo CT 385 series; (GC Healthcare) 16-slice scanners were used in the study.  The estimated computed tomography dose index volume (CTDI_vol) and dose length product (DLP) were extracted from the CT dose report on the patients’ electronic Image folders. The effective size of the abdomen was obtained by using electronic caliper on the scanner console to measure the anterior-posterior and lateral dimensions at the level of the widest diameter on the image. With Table1A from the AAPM report 220, conversion factors were determined for a total of 264 abdominal CT images. The corresponding conversion factor was multiplied by the CTDI_vol to obtain the size specific dose estimates (SSDE).  The relationships between effective diameter (ED), CTDI_VOL and age on SSDE were analyzed using minitab statistical software version 17.

Results

The mean CTDlvol was 6.94+ 1.63mGy, while SSDE was 9.76 + 2.56mGy. The SSDE decreased significantly with effective diameter, and increased significantly with the CTDI vol. The effective diameter measured between 8.72.90 and 37.70cm.

Conclusion

The study concludes that the CTDvol and patient’s abdominal size are determinant factors in the development of a size-specific radiation protection protocol and optimization of patient dose during abdominal CT examinations based on scanner output.