Abstract
Background and objectives: Accuracy of the delivered dose to the patient is one of the most important and effective factors in radiotherapy. In vivo dosimetry is used to evaluate the accuracy of delivered dose in radiotherapy. Therefore, in this study the accuracy of delivered dose to the patients was verified using in vivo dosimetry in radiotherapy department of Tabriz Imam Hospital.
Materials and Methods: Entrance doses of 320 fields treated by Cobalt-60 machine and linear accelerator including head and neck, trunk, pelvis, and extremities were measured using in vivo dosimetry system. Difference between measured entrance dose and prescribed dose for each field was determined. For all fields and also for each specific group of fields, average error and standard deviation of its distribution were determined.
Results: For whole fields, the average error of 1.34% with standard deviation (SD) of 7.12%, for 60Co fields the average error of -0.17% with SD of 5.98% and for Linac fields, the average error of -3.56% and 7.17% were seen. In head and neck fields, the average error of -0.37% with SD of 4.73%; for trunk fields the average error of %-1.88 with SD of 7.27%, and for pelvis and extremities, the average error of -2.49% with SD of 7.79% were seen.
Conclusion: The results show an acceptable systematic error in radiotherapy department. But standard deviation of 7.12% is slightly higher than the recommended value of 5%. It is possible to lower the uncertainty in delivered dose to recommended value by optimization of Linac function, regular quality control, and workload reduction.