Radiation Dose to the Closest Critical Organ during External Beam Radiotherapy of Head & Neck, Breast and Cervix at the University College Hospital, Ibadan, Nigeria

Introduction: Radiotherapy is the use of ionizing radiation for treatment of diseases, mostly malignant and non-malignant. Its goal is to deliver maximum radiation dose to tumour cells while minimizing dose to the surrounding normal cells. Studies have shown that patients who underwent radiotherapy usually receive highest scattered radiation dose to organs closest to the treatment sites due to inevitable exposure and making them susceptible to cancer induction. This study aims at quantify scattered radiation dose to closest critical organs during external beam radiotherapy of the head & neck, breast, and cervix at the University College Hospital, Ibadan, Nigeria.

Materials and Methods: Seventy-nine patients living with cancer in the region of head & neck, breast or cervix, who gave permission to participate were considered. The closest critical organs of interest are the eye lens, thyroid and femur head respectively. Thermoluminescence dosimeters (TLDs) were used to measure scattered radiation dose to these reference organs during radiation therapy of the target organs. After each treatment session, the exposed TLDs were taken to the designated Research Laboratory for processing with manual TLD reader system, HARSHAW, model 3500.

Results: The mean scattered radiation doses to reference organs during the treatment of head & neck, breast and cervical cancer cases were 110 ±77 cGy (Eye lens), 211 ± 83 cGy (Thyroid), and 319 ±103 cGy (Femur head) respectively.

Conclusion: In all, Femur head received the highest (87% of prescribed dose to target organ) scattered radiation dose followed by thyroid (54%) and the eye lens (32%) from their respective target organ.