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Background and purpose: Breast‑conserving surgery followed by radiation therapy to the whole breast is now recognized as a standard strategy in patients with breast cancer. Recommended technique for radiotherapy is whole breast irradiation followed by boost to the tumor bed. This study aimed to compare the dosimetric parameters of electron and photon beams for boosting irradia­tion in post‑lumpectomy patients of breast cancer.
Materials and methods: This analytical study included 50 patients of post‑lumpectomy breast cancer. Treatment Planning System (TPS) was used to compare the plans for electron beam and photon beam boost irradiation. The organs at risk (OAR) consist of heart, ipsilateral lung, and skin. Target-volume coverage, Conformity Index (CI), Homogeneity Index (HI), and doses to OAR were compared.
Results: Photon plans represented a considerably better CI and HI for the planning target volumes (PTV), compared to the electron beam plans. Regarding OAR sparing, the V_1Gy and D_mean in heart and ipsilateral lung with photon beam were significantly higher than electron beam (P<0.05).
Conclusion: Dosimetric analysis revealed that CI index, HI index, and PTV coverage were significantly better in photon boost plans, while OAR dosimetry conveyed a significant reduction in ipsilateral lung and heart doses with electron beam plans.

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Background and purpose: Radiation therapy make an important contribution in the control and treatment of cancers. Lungs are the main organs at risk in esophageal cancer radiotherapy. Difference between the dose distribution due to the treatment planning system (TPS) and the patient's body dose is dependent on the calculation of the treatment planning system algorithm, which is more pronounced in heterogeneities such as the lung. In this study, the dose distribution of treatment planning system was compared with Monte Carlo calculations in both homogeneous and heterogeneous tissues.
Materials and methods: Three dimensional planning composed of four fields were done on the CT images using the CorPLAN TPS of a SIEMENS PRIMUS linac. EGSnrc Monte Carlo simulation code was used for the same conditions. The dose distributions obtained from Monte Carlo simulation and the TPS were compared using PDD curve and Dose Difference Percentage index obtained from the two modes.
Results: According to the findings, the error rate from the TPS was less than 3% in the homogeneous tissue, whereas the error in the heterogeneous tissue was higher than the standard value (more than 5%).
Conclusion: The accuracy of CorPLAN TPS at homogeneous tissue is more than that in the heterogeneous tissue and this should be considered in the clinic. This study suggests that the Monte Carlo code can be used to simulate and estimate the dose distribution in radiotherapy, and in cases where the practical measurement of some dosimetric parameters is impossible or difficult, this code can be used for prediction and optimization of treatment plans.

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Background and purpose: Radiation therapy as a part of cancer treatment is used in almost 50-60% of involved cases. In prostate cancer radiation therapy, a large volume of pelvis is irradiated, so, it is necessary to preserve sensitive organs around the treatment area, especially rectum and bladder. In this study, some dosimetric parameters such as minimum dose (Dmin), maximum dose (Dmax), mean dose (Dmean) to target (PTV) and organs at risk (OAR), Integral dose, Homogeneity Index and Conformity Index were compared between two techniques.
Materials and methods: In this analytical study, computed tomography scans of 50 patients (mean age: 52 years) attending Sari Imam Khomeini Hospital were acquired and transferred to the 3D treatment planning system (TPS). For each patient, a conventional plan (Box Fields) and modified oblique four-field (MOFF) plan were prepared using TPS for 15 MV photon energy. A total dose of 7200 cGy was prescribed for each patient. Data analysis was carried out in SPSS applying paired-t-test.
Results: In current study, 15-MV energies for radiation of pelvis and bladder using box radiation fields (routine plan) lead to maximum uniformity and homogeneity of dose in irradiated tumor tissue. The results also showed that 15-MV energies for radiation of pelvis and bladder and the new plan could decrease the average integrated dose in femur heads.
Conclusion: We observed a significant effect of the geometrics of radiation fields on distribution of dose in tumor tissue and also the amount of dose received by organs at risk in radiotherapy of patients with prostate cancer.