Dosimetric Study of the Different Radiotherapy Ways for Postoperative Patients with Cervical Carcinoma / 中国医学物理学杂志

Objective:To compare the dosimetric differences of the planning target volume(PTV)and the organs at risk(OAR)for postoperative patients with cervical cancer on intensity-modulated radiotherapy(IMRT)and conventional 4 fields(4F)or 2 fields(2F)radiotherapy.Methods:Six postoperative patients with cervical cancer were chosen randomly.The next steps were CT scan,PTV and OAR contouring.The treatment protocols were designed into conventional 4F,2F and IMRT by TPS.Finally,the doso distribution and DVH were compared.Results:About the conformability of PTV,IMRT showed a significantly superior dose distribution over conventional 4F(P=0.015),and conventional 4F was superior to 2F(P=0.043).IMRT as compared with conventional 4F or 2F protocols,the received dose of the 50%volume of bladder was reduced by 25.8%and 27.5%,the rectum was reduced by 12%and 14.3%,the small intestine was reduced by 36.5%and 50%.But the differences of the femoral head(left & right)and the ilium have no statistical significance.Conclusion:in postoperative radiotherapy for cervical cancer,IMRT have Inore dosimetric advantages than conventional radiotherapy.

The Benefit of Individualized Custom Bolus in the Postmastectomy Radiation Therapy:Numerical Analysis with 3-D Treatment Planning / 대한방사선종양학회지

PURPOSE: To reduce the irradiation dose to the lungs and heart in the case of chest wall irradiation using an oppositional electron beam, we used an individualized custom bolus, which was precisely designed to compensate for the differences in chest wall thickness. The benefits were evaluated by comparing the normal tissue complication probabilities (NTCPs) and dose statistics both with and without boluses. MATERIALS AND METHODS: Boluses were made, and their effects evaluated in ten patients treated using the reverse hockey-stick technique. The electron beam energy was determined so as to administer 80% of the irradiation prescription dose to the deepest lung-chest wall border, which was usually located at the internal mammary lymph node chain. An individualized custom bolus was prepared to compensate for a chest wall thinner than the prescription depth by meticulously measuring the chest wall thickness at 1 cm2 intervals on the planning CT images. A second planning CT was obtained overlying the individualized custom bolus for each patient's chest wall. 3-D treatment planning was performed using ADAC-Pinnacle3 for all patients with and without bolus. NTCPs based on "the Lyman-Kutcher" model were analyzed and the mean, maximum, minimum doses, V50 and V95 for the heart and lungs were computed. RESULTS: The average NTCPs in the ipsilateral lung showed a statistically significant reduction (p<0.01), from 80.2+/-3.43% to 47.7+/-4.61%, with the use of the individualized custom boluses. The mean lung irradiation dose to the ipsilateral lung was also significantly reduced by about 430 cGy, from 2757 cGy to 2,327 cGy (p<0.01). The V50 and V95 in the ipsilateral lung markedly decreased from the averages of 54.5 and 17.4% to 45.3 and 11.0%, respectively. The V50 and V95 in the heart also decreased from the averages of 16.8 and 6.1% to 9.8% and 2.2%, respectively. The NTCP in the contralateral lung and the heart were 0%, even for the cases with no bolus because of the small effective mean radiation volume values of 4.4 and 7.1%, respectively. CONCLUSION: The use of an individualized custom bolus in the radiotherapy of postmastectomy chest wall reduced the NTCP of the ipsilateral lung by about 24.5 to 40.5%, which can improve the complication free cure probability of breast cancer patients.

Evaluation on the dose distribution of routine radiotherapy plan of esophageal cancer with 3D- planning system / 肿瘤研究与临床

Objective To evaluate the tumor dose distribution of routine radiotherapy plan in esophageal cancer with 3D treatment planning system. Methods For the 19 esophageal cancer patients who were diagnosed, the thoracic CT were done and GTV, CTV and PTV were delineated on the image of CT. Then a routine 3 field radiotherapy planning was produced using the Cad Plan 6.4.7 treatment planning system. The dosimetric results of GTV, CTV and PTV, target conformity and the dosimetric uniformity of variant target volume gained from DVH were compared. Results The maximal dose of GTV, CTV and PTV was 51.64Gy, 51.94Gy, 51.48Gy, respectively; the minimal dose was 41.17 Gy, 25.31 Gy, 18.94 Gy, respectively; the mean dose was 49.5 Gy, 47.34 Gy, 42.92 Gy, respectively; the conformity index was 0.94, 0.69, 0.38, respectively; and the dose variability was 2.2 Gy, 7.57 Gy, 14.56 Gy. Conclusions The routine radiotherapy plan in esophageal cancer could not offer satisfactory dose distribution. The method of CT simulation and 3D treatment planning systems should be applied to decide treatment planning.