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Objective To evaluate the inter-fraction setup error during the treatment with megavoltage computed tomography (MVCT) and provide theoretical basis for clinical target volume-planning target volume (CTV-PTV) margins for nasopharyngeal carcinoma (NPC) patients treated with tomotherapy.Methods Thirty-seven consecutive NPC patients treated with tomotherapy were prospectively enrolled for the study between February 2015 and September 2015.For each patient,one MVCT scan was obtained after conventional positioning,online correction and tomotherapy delivery daily,and the scan was registered to the planning CT to determine inter-fraction setup error.The expanding margin for PTV (MPTV) was calculated with the recipe:MPTV =2.5∑ + 0.76 (∑:systematic error;6:random error).Results The average absolute errors of the inter-fraction were (2.102 ± 0.040 6) mm,(1.490 ± 0.034 8) mm,(1.306 ± 0.335) mm and (1.392 ± 0.038 4) ° in the three dimensions.Gradual increases in both inter-fraction three-dimensional displacement were observed with time and treatment (P ＜ 0.05).The total MPTV ac counting for inter-error were 3.467 5 mm,2.979 5 mm and 2.888 5 mm.Conclusions Tomotherapy irradiation technology personalized MPTV should be adopted for the design of tomotherapy plan.Displacement increased as a function of time.
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Objective To evaluate the efficacy of percutaneous CT guided interstitial 125Ⅰ seeds implantation treatment for refractory pelvic malignant tumors and discuss the procedure of technique.Methods Twenty-three patients with refractory pelvic malignant tumors(25 lesions,diameter 3.5-7.0 cm,mean 4.5 cm) showing failure response to full chemotherapy and/or radical radiotherapy after tumors resection were undergone percutaneous CT guided intratumoral 125Ⅰseed implantation.Treatment plan system(TPS)was used to design the distribution and number of 125Ⅰ seeds according to matched peripheral dose(MPD)1-3 days before the procedure.Of which 6 cases received combined internal iliac arterial infusion chemotherapy before or after the 125Ⅰ seed implantation procedure.Results 9 ～ 75(mean 27)125Ⅰ seeds were implanted into a single tumor at first time including 6 patients with intraarterial chemotherapy for 14 cycles(mean 2.3 cycles),showed relief of clinical pain symptoms in 16 of 23 cases,72 h ～ 4 w after the seeds implantation;with the an effective rate of 69.6%.Follow up for 2-34 months(median,21 months),CT or MRI performed 2 months after the seeds implantation showed no CR,but PR in 18 cases,SD in 4 cases,and PD in 1 case,with overall response rate of 78%(18/23),and no serious complication.In addition,20 cases survived,with the longest one of 34 months and the other 3 died.Conclusions Intratumoral 125Ⅰ seeds implantation under CT guidance for pelvic refractory malignant tumors is safe,minimally invasive,and effective.