IN VIVO TRANSIT DOSIMETRY WITH ELECTRONIC PORTAL IMAGING DEVICES (EPID) FOR EXTERNAL BEAM CANCER TREATMENTS

ABSTRACT

According to the Radiotherapy Risk Profile report by the World Health Organization (WHO), the major causes of severe radiotherapy incidents are due to human errors. The real danger is when the error in administration goes undetected during cancer treatments. This may lead to radiation damage to normal tissues, and may be lethal to the patient. The aim of this work was to develop a transit dosimetry calculation model using C++ and vb.net codes for verifying patient radiation doses using amorphous silicon electronic portal imaging devices (aSi EPID), which could be fast, simple and accurate to be employed in routine clinical work. The model was tested with heterogeneous phantom by comparing the calculations from the developed model with measurements from thermoluminescent dosimeters (TLDs). The transit dosimetry model developed in this study offers satisfying results for square defined fields in real-time treatment of a tissue–mimicking phantom (anthropomorphic phantom). A comparison of absorbed dose measurements between the developed model and TLDs indicate a maximum and a minimum deviations of 3.93% and 1.02% respectively. The calculated absorbed doses from the developed model was therefore in concurrence with TLD measurements within ±5%, and was within the prescribed International Atomic Energy Agency (IAEA) reference level. The model presented therefore satisfied the accuracy requirements for clinical use. The model may therefore be used for in vivo dosimetry of radiation therapy.