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Effective Dose and Cancer Risk Estimates from Computed Tomography Procedures for Diagnosis of Renal Disease

Barrington Brevitt1, Mitko Voutchkov2 , Peter Johnson3 1

The ionizing radiation employed during computed tomography (CT) imaging can result in damage to tissue, increasing the risk of cancer and genetic mutation caused by chromosomal damage. The absorbed dose, measured in Gray (Gy) describes the total radiation energy absorbed per unit mass of tissue. However to achieve a more accurate measure of radiation exposure the effective dose (ED) is considered. This is the sum of doses delivered to each organ in relation to its radiosensitivity and susceptibility to cancer risk and genetic mutation(1). This research was conducted to determine the effective radiation dose (ED) delivered during computed tomography examinations including those to diagnose renal disease. 
A Retrospective review with the guidance of a Radiologist, of CT dose reports for patients referred for CT evaluation of the brain, chest and abdomen. 180 patients age 30 and under were targeted. A sample size of 60 was chosen at 3 facility using the formula {n= (zα/2)2 σ2/ E2} where n is sample size, zα/2 is the significance level, σ is the standard deviation with E the margin of error. The following equations were used to determine the ED; 
Dose Length Product {DLP} (mGy/cm) =SCAN LENGHT (cm) * Computed Tomography Dose Index {CTDI} (mGy) 
ED (mSv) = DLP (mGy/cm) * K (AAPM correction factor) (mSv mGy–1 cm–1) 
The result showed that there were variations of effective dose among facilities conducting CT examinations of similar anatomic areas ranging from 8.03 mSv to 23.2 mSv. In excess of 50% of the cases reviewed reported normal radiological findings. This raises the issue of diagnostic efficacy, was there a need for a CT scan to be done? 
It can therefore be concluded that there is a need to manage and document effective dose delivered to patients during CT procedures as accumulated radiation exposure increase the risks for cancers and other genetic anomalies.