Introduction: Heterogeneity correction is an important parameter in dose calculation for cancer patients where it may be cause inaccuracy in dose calculation as a result of different densities of patients. This study studied the impact of dose calculation of breast cancer patients with and without heterogeneity correction. Material and Methods: Twenty breast cancer patients were treated with Three-Dimensional CONFORMAL RADIOTHERAPY(3DCRT). Dose calculations were performed using two modes: Fast Photon mode for homogeneity and Fast Photon Effective Path length for heterogeneity with two photon energies. Monitor Units(MU), Modulation Factor, Dose Volume Histograms(DVH) and quality indices were used to evaluate the effect of heterogeneity correction on dose calculation and investigate the mechanism of this effect in the low and high energies. Results: Heterogeneity correction compared to without it showed significant reduction in MU and modulation factor at 6MVand 10MV (p<0. 05). Dosimetric parameters derived from DVH were significantly lower for Planning Target Volume (PTV) with homogeneity versus heterogeneity (p<0. 05) as D95% (95. 1%vs93. 7%) and V95%(95. 3%vs89%) for 6MV while max Dose and D2 increased. Also the dose for organs at risk exhibited an increase with heterogeneity correction. Quality indices were be worst with heterogeneity correction with a significant difference (p <0. 05). The differences between the dose with heterogeneity correction and without it in 6MV and 10MV were as follows: Δ D95% (4. 4%vs3. 4%; P=0. 001) and Δ V95%(4. 76%vs4. 5%; P=0. 001). Conclusion: non-use of the heterogeneity correction can be cause to deliver under or overdose dose to the target volume. Tissue heterogeneity correction had an impact on dose calculation for breast cancer patients and this impact was more effective for the low energy.

Background: To analyze the dosimetric and radio biologic advantages between intensity modulated RADIOTHERAPY (IMRT) and 3 dimensional CONFORMAL RADIOTHERAPY (3DCRT) and selection of optimal photon energy for IMRT treatments.Materials and Methods: 24 patients with localized prostate carcinoma were planned for 3DCRT and IMRT techniques. Radiation dose of 54 Gy with 2 Gy/fraction, was planned to Planning target volume (PTV1) (prostate+seminal vesicle+1 cm margin) and 72 Gy to PTV2 (prostate+1 cm margin) respectively. 3DCRT planning was done using 15 MV photon beam while IMRT plans were created using 6 MV and 15MV photons. Treatment plans were analyzed using mean, median, dose maximum and cumulative dose volume histogram for PTV1, PTV2, bladder, and rectum. Tumor control probability (TCP) was calculated for prostate. Normal tissue complication probability (NTCP) was calculated for bladder, rectum, and head of femur. Results: Mean dose to prostate was 72.79±0.18 Gy for IMRT 15 MV, 72.16±0.27 Gy for 3DCRT and 72.48±0.19 Gy for IMRT 6 MV. TCP was greater for IMRT 15 MV followed by IMRT 6 MV. The mean value of NTCP was significantly lower (p=0.0015) for IMRT 6 MV compared to 3DCRT for rectum while for bladder all were comparable. Conclusion: IMRT techniques shows superiority in sparing surrounding critical organs, thus reducing normal tissue complication rates while maintaining the same or higher tumor control probability. No significant difference was observed between IMRT 6 MV and IMRT 15 MV techniques.

Introduction: The purpose of this study was to evaluate the dosimetric and radiobiological parameters of salivary glands in treatment of patients with oral tongue cancer by 3D conventional RADIOTHERAPY (3D-CRT) and intensity modulated radiation therapy (IMRT) techniques. Materials and Methods: This study was performed on treatment planning of patients with oral tongue cancer in T2-3/N0 cancer staging. In this way, the treatment planning was performed on CT images for 3D-CRT and IMRT techniques (with 5, 7 and 9 fields) for all patients. Then, the homogeneity (HI) and conformity index (CI) of dose in the target volume and maximum, mean does of the salivary glands and normal tissue complication probability of parotid glands were computed and compared between different treatment. Results: Results of this study indicated an increase in HI and CI in IMRT compared to 3D-CRT (up to 61. 54% and 28. 78%). Moreover, the increase in the number of beams in the IMRT technique can lead to decrease in the mean dose of sublingual glands (up to 9. 52%) and decrease in the maximum dose of the submandibular glands (up to 6. 93%), while, the use of IMRT with 5 and 7 beams can lead to a significant increase in the probability of xerostomia in parotid gland (up to 8. 61%) compare with 3D-CRT technique. Conclusion: It can be concluded that IMRT technique with 9 fields led to improve the salivary glands protection, more homogeneity and conformity in the target volume and reducing the received dose of submandibular and sublingual glands compare to the 3D-CRT in patient with oral tongue cancer.

Background: We aimed to compare field-in-field technique (FIF) with CONFORMAL tangential field RADIOTHERAPY (CRT) in terms of dosimetric benefits for early stage breast cancer RADIOTHERAPY.Materials and Methods: Twenty consecutive left-side breast cancer patients who underwent breast-conserving surgery were included to the study. For each patient, two different treatment plans were created for the entire breast. FIF plans and CRT plans were compared for doses in the planning target volume (PTV), the organ at risk (OAR) volume including ipsilateral lung, heart, left ascending coronary artery (LAD) and the contralateral breast, the homogeneity index (HI), and the monitor unit (MU) counts required for the treatment. Paired samplest -test was used for statistical analysis.Results: The FIF technique significantly reduced the maximum dose of the PTV as well as the mean doses of the heart, LAD, ipsilateral lung and the contralateral breast (p values were<0.001 for each). When the OAR volumes irradiated with 2, 5, 10, 20, 30 and 40 Gy were compared, the results were in favor of the FIF technique. The volume receiving<20 Gy of the prescription dose for the ipsilateral lung was significantly decreased using FIF technique (p<0.001). FIF technique allowed us more homogenous dose distribution with lower MUs.Conclusion: The FIF technique provided better dose distribution in the PTV and significantly reduced the doses in the OAR. Considering the lower MUs required for treatment the FIF technique seems to be more advantageous than CRT during whole breast irradiation.

Introduction: Radiation-induced secondary primary cancer is one of the significant late side effects and an undesired outcome of RADIOTHERAPY that can be observed in long-term cancer survivors. The present study aimed to estimate the risk of second cancer risk after Three-dimensional CONFORMAL RADIOTHERAPY (3DCRT) and intensity modulated RADIOTHERAPY (IMRT) for early stage prostate cancer patient. Material and Methods: In this study, 10 patients with early stage prostate cancer have been chosen. Threedimensional CONFORMAL RADIOTHERAPY (3DCRT), intensity-modulated RADIOTHERAPY (IMRT) plans were designed. The organ equivalent dose (OED) was calculated based on linear, linear-exponential, and plateau dose-response models. The Second cancer risks (SCR) were estimated by Excess absolute risk (EAR). Results: The target dose coverage parameters were significantly improved in IMRT compared to 3DCRT. The rectum and bladder mean dose DMean, V50Gy% and V40Gy % were significantly decreased with IMRT. The maximum dose (DMax), DMean, V30Gy % and V20Gy % for head of femurs significantly decreased with IMRT plans. However, the colon DMean significantly increased with in IMRT compared with 3DCRT. The IMRT plans were decreased SCR for the rectum by 10%, 26. 6% and 19. 5% for linear, plateau and linearexponential dose-response models respectively. The bladder second cancer risk was decreased by 14% with linear dose-response model in comparison to 3DCRT plans. However, the second cancer risk for colon was significantly increased in average by 91. 2% with IMRT plans. Conclusion: IMRT technique demonstrated a clear advantage in dose coverage, conformity, and homogeneity over 3DCRT and was superior in terms of OAR-sparing. The Second cancer risk for in field organs (rectum and bladder) was decreased with IMRT compared 3DCRT plan.

Background: External beam RADIOTHERAPY (EBRT) is mainstay of treatment in patients with locally advanced cervical carcinoma (LACC). Three dimensional CONFORMAL RADIOTHERAPY (3DCRT) and intensity modulated RADIOTHERAPY (IMRT) are mainly used in EBRT. However which one is superior is still controversial. Materials and Methods: Forty patients of LACC treated with IMRT were selected for this study.3DCRT plans were also created for all the patients.3DCRT and IMRT plans were compared on the basis of planning target volume (PTV) coverage, dose to normal organs, homogeneity index (HI) and conformity index (CI95%).Results: In both the techniques 99% of PTV was covered with more than 96% of prescribed dose (PD). D15, D35 and D50 (Dose to 15%, 35% and 50% volume respectively) for bladder was reduced by 2.09%, 14.623% and 32.57% and for the rectum it was reduced by 7.46%, 23.82% and 43.68% in IMRT compared to 3DCRT. V45 (volume receiving 45 Gy) in case of bowel were found to be much less in IMRT in comparison to 3DCRT. Insignificant difference found between doses to femoral heads in IMRT and 3DCRT. The CI95% in IMRT plans was found much better than that in 3DCRT whereas HI in both the techniques were found almost same.Conclusion: IMRT significantly reduced the irradiated volume of OAR and improved dose conformity in the PTV compared to that by 3DCRT. So, it can be concluded that IMRT should be chosen as preferred technique for the EBRT of LACC with proper immobilizing devices and imaging.

Background: This study aims to evaluate and compare Three-Dimensional CONFORMAL RADIOTHERAPY (3D-CRT) versus Helical Tomotherapy (HT) based on treatment planning and selection of the most appropriate method to reduce side effects. Materials and Methods: Treatment planning was performed on images of 20 patients with head and neck cancer with lymph node involvement by HT and 3D-CRT techniques in Seyed Al-Shohada hospital, Isfahan, Iran. The quality of target coverage, the exposure of normal tissue, and radiation delivery efficiency in two studied methods were compared. Results: Tomotherapy showed significant improvement over 3D-CRT in terms of D2%, D50% Dmean, V95%, CI (conformity index), and HI (homogeneity index) for PTV (planning target volume) and in terms of D2%, D98%, Dmean, V95%, CI and HI for PTV Nodal. The mean dose received by 98% of PTV (D98%) increased in HT compared to 3D-CRT. Whereas, higher doses received in organs at risk (OARs) in 3DCRT compared to HT. Conclusion: Results showed improvements in target quality for HT over 3D-CRT, including dosimetric coverage of target volumes, homogeneity and conformity indices, and reduction of the volume of cold and hot spots. Tomotherapy also performed better than that of 3D-CRT in OARs. Overall, with the satisfactory results obtained here, HT technique has considerable promise for treating head and neck cancers with the involvement of regional lymph nodes.

Introduction: The purpose of this study is to evaluate and compare treatment plan quality metrics for postmastectomy breast cancer patients using 3-DIMENSIONAL CONFORMAL RADIOTHERAPY (3DCRT) and intensitymodulated RADIOTHERAPY (IMRT) planning techniques. Material and Methods: The current study included 50 postmastectomy breast cancer patients out of which 24 were planned with 3DCRT and 26 with IMRT technique. Treatment plan quality metrics, namely homogeneity index (HI), conformity index (CI), conformation number (CN), uniformity index (UI) and spillage index (R50), volume receiving 110% and 95% of the prescribed dose (V110% and V95%) were calculated and compared for the two planning techniques. Results: IMRT plans have better conformity, homogeneity indices, and lower V110% than 3DCRT plans with an almost similar R50% and V95%. Conclusion: Quantitative values of RADIOTHERAPY treatment plan quality metrics for the target are found in favour of the IMRT technique rather than 3DCRT. Implementation of these five parameters is helpful for evaluating treatment plans along with slice by slice and DVH analysis.

Background: The objective of this study was to compare the dosimetric outcome of plans with more fields to those with fewer ones for breast cancer patients. Method: 23 breast cancer patients were examined in this experimental study. Two groups of these patients were planned by treatment planning system. The number of beams was changed for each group, and the dosimetric parameters were calculated. The dose volume histogram (DVH) and the statistical analyses were performed for the two plans of all patients. Results: The DVH for the planning target volume (PTV) of the two techniques was estimated. Optimized plans were carried out to ensure that 95 % of the target volume takes 95 % of the dose. Based on the statistical analysis, the best coverage of dose had no relationship with the number of beams because the P-value of V105 %, V95%, V110%, Dmean, Dmax, conformity index, homogeneity index, and D5% were 0. 9537, 0. 9152, 0. 3446, 0. 8156, 0. 9516, 0. 7888, 0. 2127, and 0. 7282, respectively. The Mean ± standard error of mean for all PTV parameters was nearly the same. Also, the organ at risk had no significant difference after changing the number of beams, which means that the complication to normal tissue was nearly the same for both plans. Conclusion: The number of beams has no effect on PTV and normal tissue. Therefore, it is important for medical physicists to conduct the optimized plan without exceeding the number of beams to reduce the scattered radiation.