Biological effective dose, cumulative radiation dose, risk of malignancy and mortality rate estimation in adult patients who have a history of cancer and exposed to recurrent computed tomography

Abstract

Computed tomography is commonly used for the initial diagnosis of a tumour to provide information about the stage of cancer & to assess whether the disease is responding to treatment. Leukemia & solid tumour may have developed as a result of exposure to a low dose of diagnostic ionizing radiation so another primary tumour may develop as a result of radiation exposure. We used information in the patient sheet to measure patient effective radiation dose(E) in millisievert (mSv) & calculate cumulative dose by summation of dose over three years, estimated life attributed risk & mortality rate. The results of the current study revealed that from 50 patients 37 (74%) of them were female & 13 (26%) of them were male, age range 23- 80yr, breast cancer was the commonest cause of malignancy follow by lung cancer. Cumulative dose in mSv/yr rang 12-80 mSv, about 43(86%) of our patients exposed to more than 20mSv /yr & 7(14%) of them expose to 20 & less than 20 per year. Collective dose in three years’ range was 35-250 mSv mean 97 ± 37 Estimated radiological effective dose was more than 100 mSv in 22 (44%) per three years & 28(56%) of them had less than 100mSv. Life attributed risk for incidence of cancers was 1:285 -1:40 & mortality rate 0.21%-1.5%. A high percentage of patient 86% with cancer receive high radiation dose annually from CT scan more than considerable safe radiation dose for a worker in this field and 44% of our patient expose to cumulative dose more than 100 mSv per three which is also excess allowed dose for the radiological worker.