Dose Evaluation in the Movement Couch of the Total Body Irradiation Technique Using Semiconducting Diodes and Thermoluminescence Detectors

Aim: The present study is devoted to evaluate the dose at different points defined on the patient using semiconducting diodes and thermoluminescence detectors to excute verification of the dose at these relevant points calculated by means of movement couch and Beam Zones method of the Total Body Irradiation Technique. Material and Method: In this technique; 11 patients using 6 MV X-ray in the (non-standard) conditions lying on the couch (supine and prone positions) were treated. Barry translation couch positioned in the extended SSD on the floor of the treatment room of distance (200 cm) was used. The couch was moving (280 cm) with fixed machine dose rate (300 cGy/min), and constant velocity which is been calculated from the (beamzone method) depending on the length, different separation in different organs, thorax wall separation, and the lung density of each patient individually. Results: Comparison between calculated dose values at (orbit, lung under the shield, umbilicus, and knee) and the corresponding results measured by means of semiconductor detectors proves that there is a quite agreement with deviation in the range of (17.18 ± 3.28)%, (11.13 ± 3.72)%, (13.8 ± 3.14)%, and (6.65 ± 1.56)%, at four different sites orbit, lung under the shield, umbilicus, and knee respectively. Additionally, further comparison between the calculated dose values and the corresponding measured results performed using TLD dosimeters at the same four sites proves that the deviation falls in the range of (23.27 ± 11.77)% , (14.18 ± 10.28)% , (16.52± 7.42)% , and (17.27 ± 7.01)%, respectively. Conclusion: our results suggests that the semiconductor diodes and thermoluminesence detectors could be used for TBI quality assurance monitoring, although semiconducting diodes should remains the standard when critical dose measurements are performed. The semiconducting diodes, TLD results, and beam zones method calculations agreed within acceptable margins.