ABSTRACT
Objective To evaluate the role of equivalent uniform dose (EUD) in planning optimization of intensity-modulated radiotherapy (IMRT) for prostate cancer.Methods Ten patients with prostate cancer were randomly selected who treated with IMRT.For these patients,the treatment plans were designed with dose-volume objectives.Based on these plans,new plans were designed through replacing the dose-volume objectives with maximum EUD for rectum,bladder and small bowel,while keeping the dosevolume objectives unchanged.Comparison was made between the new plans and the former cones by paired t-test.Results The conformity index of planning target volume was better with EUD optimization compared to dose-volume (1.00 ± 0.04 ∶ 0.94 ± 0.04,t =3.80,P =0.04).The D53,D30 and Dicm3 for rectum was better with EUD optimization compared to dose-volume (24.4 ± 2.7 ∶ 25.5 ± 2.6,t =-3.82,P =0.004,34.1 ±4.3∶39.1±2.1,t=-3.80,P=0.004 and51.4±1.0∶51.8±0.9,t=-2.42,P=0.039),with V10,V20 for bladder and V10,V20,V30,V40 for small bowel also better with EUD optimization (92.2 ±6.2∶99.4±1.1,t=-4.28,P=0.002;70.7±5.7∶78.7±6.3,t=-3.10,P=0.013 and 62.2±30.2∶74.7 ±30.0,t =-4.18,P =0.002;34.3 ±26.3∶46.5 ±30.9,t =-5.46,P =0.000;17.1 ±17.0∶25.1 ±22.6,t=-3.52,P=0.007;10.6± 11.5∶ 15.6± 16.1,t=-2.64,P=0.030).Conclusions The conformity index of planning target volume is better with EUD optimization compared to dose-volume.And the dose to rectum,bladder and small bowel can be reduced through optimization with EUD optimization compared to dose-volume.
ABSTRACT
Objective To investigate the intensity modulated radiation therapy (IMRT) planning optimization method to reduce the additional dose resulting from megavoltage cone-beam CT (MVCBCT) imaging for nasopharyngeal carcinoma IMRT treatment. Methods MVCBCT images collection process was simulated using XiO treatment planning system. The mean doses of MVCBCT ( DMVCBCT ) were calculated in gross tumor volume ( GTV), clinical target volume ( CTV ) and risk at organ or tissue using 27. 4 cm× 27.4 cm portal radiation 8 MU,5 MU (A,C) and 27.4 cm× 15.0 cm portal radiation 8 MU,5 MU (B,D). The dose correct factor of MVCBCT (CFMVCBCT) according to IMRT TPS and DMVCBCT ,but CFMVCBCT plus MVCBCT imaging process for radiotherapy planning optimization. The paired t-test was play for A∶ B,C∶ D,A∶ C,B∶ D of DMVCBCT. Results The DMVCBCT and CFMVCBCT of A, B, C, D were 7. 78,5. 78,4. 88,3.55 cGy ( A∶ C, t =24.41,P＜0.01) and 0.993 -0.997 in GTV,with 7.88,6.95,4.88,4.38 cGy (A∶ B,A∶ C,B∶ C,t=3. 85, -31.82, -8.52, all P＜0. 01) and 0.992 -0.996 in CTV1 ,with 8.28,6.67,5. 17,4. 17 cGy (A ∶B,A∶C,B∶C,B∶D,t=6.41 -18.24,all P＜0. 01) and 0.991 -0.996 in CTV2;with 6.88,5.00,4.28,3. 50 cGy ( A∶ B, A∶ C,t = 2. 83,11.03, all P ＜ 0. 05 ) and 0. 989 - 0. 995 in spinal cord, with 7.88,7. 38,4. 95,4. 62 cGy and 0. 984 -0. 990 in left parotid, with 8. 67,0. 28,5. 33,0. 28 cGy and 0. 963 -0. 999 in left optic nerve,with 9. 17,0.22,5.72,0. 17 cGy and 0.821 -0.997 in left eye lens,with 6.95,2. 17,4. 38,1.38 cGy and 0. 987 -0. 997 in brain stem, with 7.78,0.45,4. 95,0. 28 cGy and 0. 978 -0. 999 ( A ∶ B,A∶ C,B∶ C,B∶ D for five organ or tissue,t =5. 06 -335. 16 ,all P ＜0. 01 ) in optic chiasm. Conclusions The MVCBCT imaging process resulted in radiation doses to patient. The impact of MVCBCT image acquired dose on IMRT treatment plan for NPC was eliminated by a compensation method.