Kaveh Shirani Tak Abi - Department of Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
Hassan Ali Nedaie - Radiotherapy Oncology Department, Cancer Research Center, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran.
Nooshin Banaee - Young Researchers and Elites Club, Science and Research Branch, Islamic Azad University, Tehran, Iran.
Hossein Hassani - Department of Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.

Introduction Intensity-Modulated Radiotherapy (IMRT) is becoming an increasingly routine treatment method. IMRT can be delivered by use of conventional Multileaf Collimators (MLCs) and/or physical compensators. One of the most important factors in selecting an appropriate IMRT technique is integral dose. Integral dose is equal to the mean energy deposited in the total irradiated volume of the patient. The aim of the present study was to calculate and compare the integral dose in normal and target organs in two different procedures of IMRT: Step-and-Shoot (SAS) and compensator-based IMRT. Materials and Methods In this comparative study, five patients with prostate cancer were selected. Module Integrated Radiotherapy System was applied, using three energy ranges. In both treatment planning methods, the integral dose dramatically decreased by increasing energy. Results Comparison of two treatment methods showed that on average, the integral dose of body in SAS radiation therapy was about 1.62% lower than that reported in compensator-based IMRT. In planning target volume, rectum, bladder, and left and right femoral heads, the integral doses for SAS method were 1.01%, 1.02%, 1.11%, 1.47%, and 1.40% lower than compensator-based IMRT, respectively. Conclusion Considering the treatment conditions, the definition of dose volume constraints for healthy tissues, and the equal volume of organs in both treatment methods, SAS radiation therapy by providing a lower integral dose seems to be more advantageous and efficient for prostate cancer treatment, compared to compensator-based IMRT.             

Integral dose, Step and Shoot Radiation Therapy, Compensator-based Intensity Modulated Radiation Therapy, Dose Volume Constraints, Dose Volume Histogram