Effect of correction/calibration factors on accuracy of in vivo dose delivery with cylindrical n-type Isorad diode in conventional radiotherapy

Purpose The main aim was to use pre-calculated correction factors and calibration factors for measurement of accuracy of dose delivery before implementation of such in vivo dosimetry on real patients visiting for first radiation treatment. These factors were verified by generating the most common treatment plans on human phantom except for breast and colon using cobalt-60 unit. Materials and methods Six treatment plans were generated, i.e. nasopharynx, bladder, prostate, brain, larynx and lung of human phantom, total 18 fields were planned keeping in view the correction factors which are to be verified. MULTIDATA Decision Support System 2.5, Shimadzu simulator, Isorad diode-n type, electrometer patient dose monitor and ATOM Adult male human phantom were used. Results and conclusion For 18 fields, the dose delivery was accurate in the range 0·29-6·74%. The deviation between measured and expected doses to nasopharynx, lung, bladder, prostate, brain and larynx cases of human phantom ranged from 1·44-3·89%, 0·29-0·54%, 0·44-6·18%, 0·54-5·16%, 0·33-4·90%, 5·58-6·74%, respectively. In 30 palliative patient cases, the first radiation treatment was also monitored. The accuracy of dosimety ranged from 1·05% to 5·35%. This study is helpful to identify areas of improvement in treatment of patients like quality control/quality assurance (QA) of treatment planning system, beam data modifications, machine repair maintenance, QA audit in radiotherapy.