ABSTRACT
Objective: To measure setup error of head and neck neoplasm in radiotherapy and discuss over effects of error on physical dose acting on target region and organs at risk of nasopharynx cancer [NPC] patients treated with intensity modulated radiation therapy [IMRT]
Methods: A total of 152 patients who developed head and neck neoplasm and received IMRT were randomly selected. Through comparing digital portal image and digital reconstruction image, we measured setup error, calculated expanding margin from clinical target volume [CTV] to planning target volume [PTV] and analyzed whether there was rules between setup error and treatment time. Additionally, 20 cases of NPC were selected. Three-dimensional error was simulated in planning system. Dose distribution was recalculated and a series of dose parameters of target volume and OAR were analyzed
Results: Setup error in left-right, head-feet and ventral-dorsal direction was [-0.62 +/- 1.46] mm, [-0.41 +/- 1.54] mm and [-0.31 +/- 1.67] mm respectively. Regarding limit value, the maximum and minimum value in left right direction, head-feet direction and ventral-dorsal direction was 2.70 mm and -6.00 mm; 3.00 mm and -5.00 mm, 5.00 mm and -7.50 mm. Expanding margin from CTV to PTV was 2.26 mm, 1.88 mm and 1.97 mm in left-right direction, head-feet direction and ventral-dorsal direction
Conclusion: During IMRT, only when setup error is controlled below 3 mm can sharply reduce the damage caused by radiation to normal tissue; therefore, quality security and control of electronic portal imaging device need [EPID] to be improved
ABSTRACT
Objective To investigate the advantage of two-way shrinking field radiotherapy with high intensity on non-small cell lung cancer(NSCLC) with stage Ⅳ.Methods Forty-two old NSCLC patients with stage Ⅳ were selected as our subjects who cannot performed surgery in the People's Hospital of binzhou.The patients all underwent CT-scan and the CT information was input TPS planning system in order to outlined gross tumor volume(GTV1) and make plan 1 with the first three-dimensional conformal radiotherapy 50 Gy/25 F～ 54 Gy/27 F.Then the 2nd CT-scan was performed to sketch GTV2 and make Plan 2.The detail of Plan 2 was that the amount of radiation was increased to the total 66 Gy/33 F ～ 70 Gy/35 F,two radiotherapy plans in accordance with 1 times/d,5 times/weeks;chemotherapy with paclitaxel 40 mg/m2,weekly radiotherapy before the intravenous infusion,once every 6 weeks.Results The median of reduce tumor size between GTV2 and GTV1 was 68.85 cm3 and relative reduce tumor size was 28.32％.As to short-term effect,there were 5 cases with total recovery(1 1.9％),25 cases with partly recovery(59.5％),10 cases with stable stage (23.8 ％),2 cases with development(4.8％).Local control rate regarding of tumor development was 71.4％ at 1-yrea period and 23.8％ at 2-year periods.Survival rate was 73.8％(31/42) at 1 year and 28.6％(12/42) at 2-year.Side effects included radiation esophagitis and radiation pneumonitis based,radiation-induced lung injury.Condusion The therapy scheme of two-way three-dimensional conformal radiation dosage treatment of NSCLC,GTV and re-plan outlined dosage can increase the target dose,radiation therapy to reduce side effects.