Radiation Dose From Exposure to Computed Tomography Scan of the Brain in a Reference Hospital in Nigeria
Abstract
Background: Diagnostic reference levels have been set by relevant regulatory agencies in different countries as a result of the biological risks from exposure to ionizing radiation. However, no study has been carried out in our centre to generate data that may come in handy in establishing a local reference level.
Objective: To quantify the absorbed dose from Computed Tomography (CT) scan of the brain using the CT dose chart and thermoluminescent dosimeters (TLD) with a view to establishing local diagnostic reference levels (DRL) for our centre .
Methods: A prospective, cross-sectional study involving 30 patients aged 4 months to 72 years referred for brain CT. Patients were positioned according to standard protocols for brain CT. Two TLD chips were placed on the glabella and occiput respectively. The posterior one was held in place by the weight of the head while the anterior one was held in place with tape. With an azimuth of 180o, the posterior TLD was marked as ‘entrance’ and the anterior as ‘exit.’ The TLDs were only detached at the end of the investigation. They were sealed separately in small transparent cellophanes bags and sent for reading at a regional radiation dosimetric laboratory. Simple statistical tools were used to determine central tendencies.
Results: The absorbed radiation dose noted in our centre had a range of 38.6 - 66.4mGy (1.93-3.32mSv) from CT dose chart and 0.6-104mGy (0.03-5.20mSv) for TLD respectively. The mean collective dose for CT (50.3 ± 10.2mGy; 2.52 ± 0.51mSv) was slightly higher than for TLD ( 40.83 ± 26.4mGy; 2.04 ± 1.32mSv). A paired-sample t-test at a probability level of p < 0.05 (for significance) yielded a p-value of 0.05 indicating that there is a statistical significant difference between both means.
Conclusion: The dose from our practice is within the range got from other studies. However, further dose reduction is possible with a more careful technique.
Keywords: Radiation, dose, Computed Tomography, TLD
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