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Intensity modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3D CRT) are two treatment modalities in prostate cancer, which provide acceptable dose distribution in tumor region with sparing the surrounding normal tissues. IMRT is based on inverse planning optimization; in which, intensity of beams is modified by using multileaf collimators and also compensators with optimum shapes in step and shoot (SAS) and compensator-based method, respectively. In the recent study, some important parameters were compared in two IMRT and 3D CRT methods. Prescribed dose was 80 Gy for both IMRT procedures and 70 Gy for 3D CRT. Treatment plans of 15 prostate cancer candidates were compared to target the minimum dose, maximum dose, V 76 Gy (for IMRT plans) V 66.5 Gy (for 3D CRT), mean dose, conformity index (CI), and homogeneity index (HI). Dose conformity in compensators-based IMRT was better than SAS and 3D CRT. The same outcome was also achieved for homogeneity index. The target coverage was achieved 95% of prescribed dose to 95% of planning target volume (PTV) in 3D CRT and 95% of prescribed dose to 98% of PTV in IMRT methods. IMRT increases maximum dose of tumor region, improves CI and HI of target volume, and also reduces dose of organs at risks. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The aim of radiation therapy treatment planning is to achieve an optimal balance between delivering a high dose to target volume and a low dose to healthy tissues. In order to refrain any complications resulting from the dose to the surrounding normal organs, the role of treatment plan has been critically evaluated in term of how large the volume or mass of normal tissues exposed in the radiation. The integral dose, hence, is one of the important guidance for predicting the radiation effects and choosing the treatment plan. The goal of this study is to compare and investigate the integral doses in conformal 3D vs. IMRT plan. Dosimetric data from five patients of prostate cancer, treated by simultaneous integrated boost IMRT and 3D CRT were evaluated in this prospective study. Target volume and organs at risk were contoured using M.I.R.S Treatment Planning System (Module Integrated Radiotherapy System version 5.0.00). A dose of 80 Gy to the PTV1, 57 Gy to RTV2 and 62 Gy to the PTV3 and 70Gy in 3D CRT and for PTV, was prescribed. For each patient IMRT plans using S.A.S (dynamic Step and Shoot) and 3D CRT with 6, 10 and 18MV energies, were done. To calculate the ID to the normal healthy tissue all the target volumes were achieved. The Integral Dose was calculated as the mean- dose times the volume of the structure. A total of thirty IMRT and 3D CRT plans were performed for evaluation. The mean ID received by rectum for 3D CRT was almost 1.04% greater than IMRT while in bladder mean value of ID for IMRT is also bigger than 3D CRT approximately about 1.04%. In RFH and LFH the mean values of ID for 3D CRT were almost 1.05% and 1.06% greater than IMRT, respectively. Due to the three PTVs in IMRT the integral dose in target volume has the biggest value comparing with 3D CRT, considerably. [ABSTRACT FROM AUTHOR]