Background: The (DVH) is the most used radiotherapy formulation. (DVH) plays a fundamental role in determining DOSE constraints and side effects. VOLUME also plays the main role in calculating (DVH). In prostate treatment, there is no comprehensive consensus on determining the association between bladder VOLUME (BV) and side effects. Our aim is to investigate the reproducibility of bladder (DVH) ((DVH)B). D50%BV (DOSE received by 50% of BV) is used to analysis (DVH)B. Materials and Methods: We contoured the bladder of 467 daily MVCT images of fifteen prostate cancer patients who underwent tomotherapy. Using R software 4.2.3, the correlation between the bladder center of mass (XCM, YCM, ZCM), BV with D50%BV were modeled by the mixed model. Two prediction models were presented for D50%BV, the first model was based on BV and (XCM, YCM, ZCM), the second model was based on BV. Results: Statistical analyses revealed that independent factors YCM, ZCM, and BV have a significant influence on the response variable D50%BV. According to mixed model, YCM has a positive correlation with D50%BV, while ZCM or BV has a negative correlation. XCM does not significantly affect D50%BV. Akaike Information Criterion (AIC) index indicated that first model has a higher goodness of fit than second one. Conclusion: Our findings demonstrate that bladder location also affects D50%BV, in addition to BV. It can be concluded that (DVH)B is not always repeatable as a scientific claim.

BACKGROUND AND OBJECTIVE: Breast cancer is the most common cancer in women worldwide and radiotherapy is the best treatment choice after mastectomy. One of the main aims of radiotherapy is applying the uniform DOSE distribution in all treatment VOLUME. The objective of this study was to evaluate the chest wall angle by reference axis (vertical and horizontal) and use optimum wedge filter in post-mastectomy radiotherapy.METHODS: One hundred and forty cases of breast cancer after mastectomy surgery were included in this study. Patients were planned by ALFARD treatment planning system (TPS) or three-dimensional (3D) Core PLAN Treatment Planning System (TPS). DOSE VOLUME HISTOGRAMs ((DVH)s) with different wedge angles and without wedge were obtained for every case. (DVH)s were analyzed and compared for finding optimum wedge angle. Chest wall angle with reference axis was determined by GetData software. The wedge angel and chest wall angel were compared to reach the equation between them.FINDINGS: The optimum wedge angle was the function of chest wall angles. In all cases the compensating wedge filter causes better homogeneity index and results of chest wall angle determination were in good agreement with the results of (DVH)s as gold standard for determining homogeneity index.CONCLUSION: Finding of this study showed that an improved chest wall angle in mastectomy patients is a new method for choosing optimum wedge angle. Also time cost of this method is better than (DVH) technique.

Background: We aimed to investigate the accordance of Critical Organ Scoring Index (COSI), Conformity Index (CI) and Normal Tissue Complication Probability (NTCP) parameters with DOSE VOLUME HISTOGRAMs ((DVH)) used for evaluation of 3 different pelvic radiotherapy plans. Materials and Methods: Ten gynecologic carcinoma patients who underwent adjuvant radiotherapy were enrolled in this study. Treatment plans were created with conformal treatment planning (3DCRT) and intensity modulated radiation therapy (IMRT) to a total DOSE of 50. 4 Gy in 28 fractions. Initially, VOLUME related DOSE evaluation was done via (DVH). Subsequently, HI, CI, COSI and NTCP for selected normal tissues were calculated for each plan and compared with (DVH) parameters. Finally, a graphical demonstration was evaluated to see if the results were in accordance with (DVH). Results: CI results were statistically significant in favor of IMRT (p<0. 001). Rectum V40Gy decreased with 9IMRT compared to 3DCRT and 7IMRT (p=0. 013 and p=0. 013). V40Gy for bladder was also lower with 9IMRT compared with 3DCRT and 7IMRT (p=0. 005 and p=0. 012). COSI calculations revealed better small intestine protection in IMRT plans similar with (DVH) (p=0. 005 and p=0. 022). Femoral heads were better protected with IMRT plans were better compared to 3DCRT in NTCP calculations (p=0. 002). Normal tissue protection was worst with 3DCRT via both (DVH) and COSI evaluations (p=0. 001 and p<0. 001 respectively). Conclusion: Using the indexes in this study to decide the most appropriate plan among multiple treatment plans in gynecologic cancer patients will be timesaving and easier in comparison with evaluating the (DVH) of every alternative plan.

Background: Colorectal cancer is the most common gastrointestinal cancer and the fourth leading cause of death in the world. This study aimed to investigate and compare dosimetric differences in radiation therapy for rectal cancer in two supine and prone positions.Methods: In a cross-sectional study in Milad Hospital in Isfahan, the CT scan data of 30 patients who are candidates for radiation therapy for rectal cancer were sent to the treatment design software. The target organ PTV (Planning Target VOLUME) and the organs at risk including the bowel bag and the bladder were contoured by the radio-oncologist. The design of three-dimensional conformal radiotherapy (3D_CRT) was designed using 3 and 4 field methods and 18 megavolt energy. Finally, using the DOSE-VOLUME distribution curve DOSE-VOLUME HISTOGRAM ((DVH)), the dosimetry of the target organs and the organs at risk were discovered and converted by assimilation.Findings: The average DOSE that will receive by the bowel bag and bladder in the prone position in the 3-field method was significantly lower than the other studied methods. In addition, the position of the 3-fields supine delivers a higher DOSE to the organs at risk than the 3-fields prone. However, organs of the four fields in supine position will receive a higher DOSE compared to the other fields.Conclusion: In radiation therapy of rectal cancer, due to the improvement of the coverage of the target VOLUME and better DOSE design, it is suggested than the treatment with the 3-field in position prone.

Background: Intensity-Modulated Radiation Therapy (IMRT) is one of the best methods in the treatment of optic nerve sheath meningioma (ONSM) with tumor growth control and visual stabilization. In this study, various IMRT techniques were evaluated from the point of view of DOSE fall-off beyond the target boundaries to achieve the optimal technique. Methods: The optimization of 3 IMRT techniques was performed using 3, 5, and 7 fields with 6 MV photons in 15 patients with ONSM using Prowess Panther treatment planning system. To evaluate treatment plans, in addition to data extracted from DOSE-VOLUME HISTOGRAM ((DVH)) and evaluation of target coverage indices, differential and cumulative DOSE gradient indices (DGIs) were calculated and compared between the three techniques. Findings: The maximum and the mean DOSE received by the tumor increased with increasing number of IMRT fields. The uniformity (UI) and homogeneity (HI) indices were significantly different between the 3-field and 7-field techniques; and the conformity index (CI) was close to ideal value (0. 99) in 7-field technique. Difference of differential DOSE gradient index (dDGI) was negligible between the three techniques, and only at the 45% isoDOSE level, there was a significant difference between the 5-and 7-field techniques. Cumulative DOSE gradient index (cDGI) showed smaller values in 7-field technique than the other two techniques. Conclusion: The three IMRT techniques have no considerable statistical difference in DOSE fall-off rate beyond tumor boundaries; and their choice in the treatment of ONSM depends on the physician's discretion based on the whole patient's conditions.

Background: 90Y and 177Lu are two well-known radionuclides used in radionuclide therapy to treat neuroendocrine tumors. Objective: This current study aims to evaluate, compare and optimize tumor therapy with 90Y and 177Lu for different VOLUMEs of the tumor using the criterion of self-absorbed DOSE, cross-absorbed DOSE, absorbed DOSE profile, absorbed DOSE uniformity, and DOSE-VOLUME HISTOGRAM ((DVH)) curve using Gate Monte Carlo simulation code. Material and Methods: In our analytical study, Gate Monte Carlo simulation code has been used to model tumors and simulate particle transport. Spherical tumors were modeled from radius 0. 5 to 20 mm. Tumors were uniformly designed from water (soft tissue reagent). The full energy spectrum of each radionuclide of 177Lu and 90Y was used in the total VOLUME of tumors with isotropic radiation, homogeneously. Self-absorbed DOSE, cross-absorbed DOSE, absorbed DOSE profile, absorbed DOSE uniformity, and (DVH) curve parameters were evaluated. Results: The absorbed DOSE for 90Y is higher than 177Lu in all tumors (p-value <5%). The uniformity of the absorbed DOSE for 177Lu is much greater than 90Y. As the tumor size increases, the (DVH) graph improves for 90Y. Conclusion: Based on self-absorbed DOSE, cross-absorbed DOSE, absorbed DOSE uniformity, and (DVH) diagram, 177Lu and 90Y are appropriate for smaller and larger tumors, respectively. Next, we can evaluate the appropriate cocktail of these radionuclides, in terms of the type of composition, for the treatment of tumors with a specific size.

Background: Nasopharyngeal cancer is one of the common head and neck cancers and the main treatment for this type of cancer is radiotherapy. The purpose of this study is to investigate and compare the DOSE of organs at risk in two adaptive three-dimensional methods (3D-CRT) and helical tomotherapy (HT) in patients with head and neck cancers. Methods: This study is a cross-sectional experimental retrospective study and to conduct this study, CT scan images (Computed Tomography) of 16 patients with early stages of NPC with an average age range of 16-81 years (42. 7 ±,16. 3) those were randomly selected. The organs at risk and their target VOLUME were contoured and the treatment plan of the patients was done for both HT and 3D-CRT methods. In the end, using a VOLUME-DOSE HISTOGRAM ((DVH)), the dosimetry variables of organs at risk and target VOLUME were extracted and compared with each other. Findings: Compared to 3D-CRT, the HT method improved the homogeneity index and concordance index. It also significantly reduced the DOSE of the studied OARs compared to 3D-CRT, although the DOSE of some of these organs exceeded the prescribed DOSE limit. Conclusion: HT method is a better technique for treating nasopharyngeal cancer patients who are candidates for radiotherapy due to better coverage of the target VOLUME and also, better performance in preserving OARs compared to the 3D-CRT method.

Background: The present study aimed to evaluate dosimetrically and correlate the lung and heart DOSE VOLUME HISTOGRAM ((DVH)) of the 4 field three-dimensional conformal radiotherapy (3DCRT) with 7 field intensity modulated radiotherapy (IMRT) in patients with oesophageal cancers. Method: This retrospective dosimetric study considered 20 oesophagus cancer patients treated with definitive chemoradiation with IMRT technique. In the 7 field IMRT technique, the first phase delivered a DOSE of 36Gy/18fr followed by 18Gy/9fr in two weeks in the second phase. In the 3DCRT technique, the first phase was planned with 4 field technique with two parallel opposed and two posterior oblique fields, followed by the 3 field technique in the second phase. The assessments of the techniques were performed using differential (DVH) analysis of the right and left lungs, heart, and the spinal cord. The values of the mean DOSE, V20 (VOLUME receiving 20 Gy), and V30 (VOLUME receiving 30 Gy) were assessed for any correlations. Results: The (DVH) of V20 in IMRT showed 5% less lung VOLUME irradiation compared with the 3DCRT plans and over 20% less V30 for irradiated heart VOLUME. The study demonstrated a statistical advantage of using 7 field IMRT over 4 field 3DCRT in reducing the mean percentage DOSE to both lungs, heart, and spinal cord. Conclusion: 7 field IMRT is superior to 4 field 3DCRT plans in significantly reducing the average percentage of irradiated VOLUME of both the lung and heart in esophageal cancer radiation therapy.

Background: Radiation-induced lung toxicity is an important DOSE-limiting toxicity in lung cancer radiotherapy, for which there are no generally accepted predictive factors. This study seeks to identify risk factors associated with the development of severe radiation-induced lung toxicity using clinical and dosimetric parameters.Methods: We reviewed the medical records of 54 patients with histologically proven stage III non-small cell lung cancer treated with three dimensional-conformal radiotherapy at Alexandria Main University Hospital between January 2008 and December 2011. The original treatment plans for those patients were restored and imported to a treatment planning system. Lung DOSE–VOLUME HISTOGRAMs and various dosimetric parameters were calculated. Univariate and multivariate logistic regression analyses were performed.Results: The following grades of radiation-induced lung toxicity were observed in patients - grade 0: 17 (31.5%), grade 1: 5 (9.3%), grade 2: 13 (24.1%), grade 3: 15 (27.8%), and grade 5: 4 (7.4%). A total of 19 (35.2%) patients developed grade ≥3 and were considered to have an event. Univariate analysis showed that age, presence of chronic obstructive pulmonary disease and location of the primary tumor had significant associations with severe radiation-induced lung toxicity. Other dosimetric variables such as tumor side, histology, forced expiratory VOLUME in 1 s, smoking, and gender showed no significant correlations with severe radiation-induced lung toxicity. Multivariate analysis showed that the presence of chronic obstructive pulmonary disease (P=0.001) and location of the primary tumor (P=0.010) were the only predictive factors for severe radiation-induced lung toxicity.Conclusion: This study demonstrates that patients with chronic obstructive pulmonary disease and lower lung lobe tumors have a high risk of severe radiationinduced lung toxicity when treated with combined chemoradiotherapy. These easily obtained clinical factors should be considered when calculating the risk for radiationinduced lung toxicity.