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.

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.

Introduction: In this survey, radiation-induced secondary cancer risks (SCRs) have been assessed in irradiated organs following three-dimensional CONFORMAL radiation therapy (3D-CRT) of breast cancer using the Biological Effects of Ionizing Radiation (BEIR) VII models. Material and Methods: Sixty patients with left-sided breast cancer, who were treated with a total breast dose of 50 Gy in 2 Gy fractions were chosen for this study. Differential dose volume histograms (dDVHs) were retrieved, and values of mean organs dose were computed. Second cancer risks for the heart, ipsilateral lung, liver, thyroid, and contralateral were estimated using both excess relative risk (ERR) and excess absolute risks (EAR) models as proposed by the BEIR VII committee of the U. S National Academy of Sciences. Results: The mean organ dose values of these 60 patients were 6. 8, 15. 9, 3. 7, 4. 5, and 1. 5 Gy in the thyroid, ipsilateral lung, contralateral breast, heart, and liver, respectively. Based on the BEIR VII models, ERR was estimated to be 21. 2, 5. 0, 1. 6, and 1. 4 Gy-1 for the ipsilateral lung, thyroid, heart, and liver, respectively. In addition, excess absolute risks for cancer incidence were calculated as 105, 45. 8, 15. 8, and 4. 35 Gy-1 for these organs, respectively. Conclusion: In this survey, SCRs were quantitatively measured for various organs of breast cancer patients who received 3D-CRT. We observed that 3D-CRT treatment was associated with a relatively high SCR in the lung.

Aims: It was aimed to investigate postoperative CONFORMAL RADIOTHERAPY planning that provides the best target volume and the least dose for critical organs in cancers of stomach.Methods: This study was conducted on the CT simulation images of thirty patients diagnosed with gastric cancer. Target volumes and the organs at risk were contoured. AP-PA reciprocal parallel field conventional plan and three- and four-field 3D CONFORMAL plans were created using linear accelerator. Target volumes and doses consumed by organs at risk were compared by dose-volume histograms.Results: While a sufficient dose could be applied to target volumes in all plans with CONFORMAL planning, average figures showed that 95% of porta hepatis area failed to take the prescribed dose (D95) in some plans by using AP-PA reciprocal parallel zone conventional plans. The most convenient protection for spinal cord, heart and kidneys was obtained by CONFORMAL four-field technique and the liver doses were increased in CONFORMAL four-field plans but did not exceed the tolerance dose. And also, in the conventional AP-PA reciprocal parallel field plans, tolerance dose of spinal cord (4500 cGy) was exceeded.Conclusion: In this study, CONFORMAL four-field technique was superior considering target volume dose distributions, and especially spinal cord doses in all localizations and heart doses in cardia tumors. Kidney doses were also reduced in CONFORMAL four-field planning, but failed to reach statistical significance. There was a not exceeding tolerance limits dose increase in liver.

Background: The aim of this study was to compare the dosimetric and radiobiological efficiency of various intensity modulated RADIOTHERAPY (IMRT) techniques with 3D conventional RADIOTHERAPY (3D-CRT) technique in the treatment of early stage oral tongue cancer. Materials and Methods: This study was performed on 38 CT images of patients who were planned with 3DCRT and three sets of IMRT treatment plans including five, seven and nine fields with prescribed dose of 66 Gy to planning target volume. The dose volume histograms, homogeneity index (HI), conformity index (CI) and normal tissue complication probability (NTCP) of main organs at risk were derived using Prowess Panther treatment planning system. Results: The results of this study indicated an increase in HI and CI for IMRT plans compared to 3D-CRT. Furthermore, IMRT techniques led to a statistically significant reduction in received dose by mandible (up to 10. 10 Gy) and thyroid (up to 13. 59 Gy) compared to the conventional technique used; whereas, it led to a statistically significant increase in received dose by parotid glands (up to 7. 62 Gy) and brain stem (up to 9. 87 Gy). In addition, IMRT increased (up to 12. 79%) the probability of occurrence of parotid xerostomia and decreased mandibular complications (up to 7. 76%) in comparison to conventional treatment. Conclusions: It can be concluded that IMRT can be more successful in improving oral tongue cancer treatment with more conformity and homogeneity. However, IMRT may not be required for all patients with oral tongue cancer at early stage of the disease.

Hassan Ali Nedaie et al., recently have published "Assessment of Radiation-induced Secondary Cancer Risks in Breast Cancer Patients Treated with 3D CONFORMAL RADIOTHERAPY" paper in Iranian journal of Medical Physics [1]. The aim of this study was to evaluate the secondary cancer risk in organs at risk for breast cancer RADIOTHERAPY by the 3D-CRT technique. The authors used BEIR VII model for measuring of excess absolute risk (EAR) and excess relative risk(ERR). This model was basically used for organs that received low dose (below 1-2 Gy) [2]. . .

Background: For the purpose of individual clinical target volume assessment in RADIOTHERAPY of prostate cancer, MRSI was used as a molecular imaging modality with MRI and CT images. Materials and Methods: The images of 20 prostate cancer patients were used in this study. The MR and MRSI images were registered with CT ones using non‐rigid registration technique. The CT based planning (BP), CT/MRI BP and CT/MRSI BP was performed for each patient. For plan evaluation, Dose Volume Histograms (DVHs) data were used. A paired sample T‐test was used for the analysis of the obtained data.Results: The percentage of variation of CTVMRI to CTVCT and PTVMRI to PTVCT were 12.83% and 8.97%, respectively. CTVMRSI and PTVMRSI were 21% and 27.41% more than their corresponding values of CT volumes. The mean percentage of variation in rectum volume that received 60% of the prescribe dose (V60R) in MRSI/CT BP relative to CT BP was 14.66%.Conclusion: The use of MRSI in detecting of prostate adenocarcinoma could provide some decisive information to determine optimum volume and safe margin for target definition to improve adaptive RADIOTHERAPY in prostate cancer.

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.

Background: Thyroid cancer is one of the most common secondary malignancies as a result of receiving therapeutic doses to the head and neck. In this study, the probability of secondary thyroid cancer risk due to neutron contamination of 15 MV Siemens Linear Accelerator (LINAC) in brain tumor 3D-CONFORMAL Radiation Therapy (3D-CRT) was calculated. Methods: Neutron fluence and neutron dose were measured at different points at the treatment table using an energy-independent neutron detector consisting of a sphere moderator and a Boron Trifluoride (BF3) counter, and the neutron dose equivalent to the thyroid was determined to calculate the probability of secondary cancer risk. Findings: The neutron dose equivalent was obtained at the central axis (0. 304 mSv/Gy) and at 4 cm (0. 285 mSv/Gy), 15 cm (0. 229 mSv/Gy), 45 cm (0. 125 mSv/Gy), and 150 cm (0. 02 mSv/Gy) inferior. The neutron dose equivalent reaching the thyroid for the total prescribed dose was 12. 366 mSv. According to that, the probability of secondary thyroid cancer risk was obtained as 0. 001%. Conclusion: The thyroid dose in high-energy radiation therapy of brain tumor cannot cause significant biological damage. Therefore, the risk of secondary thyroid cancer due to neutron contamination is relatively low.