ABSTRACT
Objective To compare dose distribution in gamma knife radiotherapy plan, conformal radiotherapy(CRT)plan and intensity modulated radiotherapy(MRT)plan for patients with small mass in lung, and evaluate their characters. Methods Fourteen patients with small mass in lung participated in the study. Gamma knife radiotherapy plan(plan 1), CRT plan(plan 2)and IMRT plan(plan 3)were made for each mass. The planning target volume(PTV)and the dose include 95% PTV were consistent.Conformal index(CI), homogeneity index(HI), lung V5 ,V10 ,V20 ,V30 and the max dose of esophagus and spinal cord were analyzed. Paired samples t-test was used for comparison between each two plans. Results The CI of the plan 1,2 and 3 were 0. 58,0. 46 and 0. 63, respectively. CI of the plan 1 ＞ that of the plan 2 (t= -3.95,P =0.000),plan 3 ＞ plan 2(t = -6.01 ,P =0.000),plan 1 =plan 3(t =1.64,P =0.116);HI of the plan 1,2 and 3 were 1.66,1.10 and 1.07 respectively. HI of the plan 1 ＞ plan 2 ,plan 1 ＞ plan 3(t= -20.52,21.41 respectively, both P=0. 000),plan 2 = plan 3(t= -1.08,P=0.294). The wholelung V5 ,V10 ,V20 and V30 were 10.0% ,5.6% ,2. 4% and 1.2%, respectively, in plan 1 ;20. 2% ,13. 4%,6. 9% ,3.0%, respectively, in plan 3; and 26. 5%, 18. 0%, 11.4% and 4. 6%, respectively, in plan 2.The V5, V10, V20 and V 30 of the plan 1 ＜ in plan 2(t = 9. 68,8. 41,5. 45,5. 14, all P = 0. 000), the V5,V10,V20 and V30 of the plan 1 ＜ in plan 3(t=7.58,8.95,6. 15,4.78, respectively, all P=0.000),the V5 ,V10, V20andV30 oftheplan2 ＞ inplan3(t =9. 71,5. 91,4. 13,3.91, respectively, allP =0.000).The max dose of esophagus in plan 1 ,2 and 3 were 24.93 ± 21.54, 31.90 ± 18. 75, 29. 19 ± 23.09 Gy,respectively, plan 1 ＜ plan 2(t = -2. 71 ,P=0.013),plan 1 = plan 3(t = - 1.49,P =0. 152),plan 2 =plan 3(t = 1.35, P = 0. 193). The max dose of spinal cord in plan 1,2 and 3 were 12.07 ± 10. 67,17.70 ±11.35 and 8.92 :± 10. 04 Gy, respectively, plan 2 ＞ plan 1 ＞plan 3(t = -2. 38,2. 29,4. 83,P=0. 1027,0.033,0.000);All three plans of each mass meet the needs that the max dose of the esophagus≤60 Gy and the max dose of spinal cord ≤40 Gy. Conclusions The dose of the normal lung was lower, but the HI and the max dose of spinal cord were higher in Gamma knife radiotherapy plan than those in the CRT and the IMRT plan of the small mass in lung.