Entrance skin dose assessment of selected computed radiography facilities in Ghana

The basic challenge with computed radiography (CR) systems is the large dynamic range which provides an opportunity for radiographers to gradually increase exposure factors and still produce good image quality, a practice that can lead to dose creep.

The aim of this study was to establish  the entrance skin dose (ESD) values for nine selected examinations in three CR facilities in Ghana (chest PA, abdomen AP, lumbar Pelvis AP, lumbar spine LAT, cervical spine AP, cervical spine LAT, skull PA and skull LAT). ESD was estimated by the indirect method involving the use of a standard equation.  The study involved 150 females and 120 males with the average age of 50 ± 14 years. The average weight of the study population was 69 ± 8 kg, and the average height of 162 ± 9 cm. The CR systems used at all the hospitals were manufactured by Shimadzu medical systems (Kyoto, Japan) and the model number was UD150L-40E.

The average ESDs (mGy) for each examination were; 0.93 ± 0.7, 3.04 ± 0.4 , 4.95 ± 0.9, 0.59 ± 0.3, 0.63 ± 0.4, 1.77 ± 0.3, 1.64 ± 0.3, 2.31 ± 0.4 and 3.15 ± 0.6 for chest PA, lumbar spine AP, lumber spine LAT, cervical spine AP, cervical spine LAT, skull PA, skull LAT, pelvis AP, and abdomen AP respectively. The single factor ANOVA t-test that was performed indicated a significant difference (p-value = 5.73 x 10-15) among the ESDs for chest PA examination.

Over exposure of patients is very possible with CR systems, it is therefore important for patient dose to be audited periodically in order to achieve the principles of As Low As Reasonably Achievable (ALARA).