Diagnostic Reference Levels For Common Computed Tomography Examinations In Adult Patients, Kampala- Uganda

Abstract

The aim of this study was to estimate the computed tomography (CT) dose levels for common examinations in Kampala. Dose data and scan parameters for the most commonly performed procedures were surveyed during a five-month period in 4 CT centers with mul-tislice scanning capabilities (16-64 slices). The CT volume dose index (CTDI vol ) and dose length product (DLP) displayed on the scanner console were recorded for a minimum of 10 patients with an average weight of 67 kg and used to compute the reference levels. The rounded 3 rd quartile of the dose was calculated by compiling all results from centers surveyed and set as the regional DRL.

The CT console dose data were validated after scanning the CTDI head and body phantom. The results indicated an absolute maximum deviation of 20.0% and 18.3% for the head and body phantom respectively, indicating that all scanners passed the output test.

Data was collected for 419 patients. The regional DRLs are proposed using CTDI vol (mGy) and DLP (mGycm). The rounded regional DRL in terms of CTDI vol was 56, 48, 55, 9, and 24 respectively for acute stroke, trauma, and cardiovascular accident (CVA), high-resolution chest CT, and liver metastases. The DRLs in terms of DLP (mGycm) were; 1443, 1248, 1486, 730, and 978 respectively for acute stroke, trauma, cardiovascular accident (CVA), high-resolution chest CT, and liver metastases.

Simple linear regression analysis performed on the scanning parameters and the volume CTDI revealed that tube peak voltage (kVP) was the most significant parameter (β=0.740), followed by effective tube current (mAs) with a normalised coefficient, β of 0.585.