| Objective The aim of this study is to evaluate different radiotherapy plannings of non-small-cell lung cancer by analyze and compare the dosimetric distribution of tumor target and surrounding normal tissue, while using dynamic multileaf collimator intensity-modulated radiotherapy(DMLC-IMRT),MIMiC multileaf collimator intensity-modulated radiotherapy(MIMiC-IMRT) and 3-dimensional conformal radiotherapy(3DCRT), to obtain the advantages and disadvantages of treatment plannings mentioned above.Methods A total of 12 patients with biopsy-proven non-small-cell-lung cancer was studied,which treated with Varian Eclipse 3D-treatment system and NOMOS Peacock treatment system. Based on the CT images of the patients, we delineated the outline of different regions as gross tumor volume (GTV),clinical target volume(CTV), planning target volume(PTV) and the organs at risk (lung,esophagus,heart,spinal cord) separately. Each patient was done with four radiation treatment plannings as 3DCRT,5-beam DMLC-IMRT,7-beam DMLC-IMRT and MIMiC-IMRT, all had the 66Gy of prescription dose in PTV while delivered in 33 fractions.Every planning should satisfy the criteria as not less than 95% volume coverage in PTV should be received the defined prescription dose, while dose for the organ at risk is within the tolerated dose.By comparison of the isodose distribution, dose-volume histograms (DVH) and derivated conformity index (CI) and heterogeneity index (HI) of the four plannings mentioned above, we can show the difference of the dosimetric distribution for the target volume and normal tissue.Results Under the prescription dose, the dosimetric distribution for all four plannings can be satisfied, according to anticipated therapeutic requirements.The mean dose of PTV was 67.66Gy,68.53Gy,68.57Gy and 68.74Gy for 3DCRT, IMRT groups(5-beam DMLC-IMRT,7-beam DMLC-IMRT and MIMiC-IMRT included) respectively, while that of IMRT groups was higher than 3DCRT.The CI for IMRT groups was higher than that of 3DCRT, which was 0.67,0.74,0.75,and 0.74 respectively. The HI was 1.09, 1.14,1.14 and 1.16 for 3DCRT and IMRT groups respectively, while IMRT groups was higher than 3DCRT, especially for MIMiC-IMRT. For 3DCRT and IMRT groups, the mean lung dose(MLD) was14.27Gy,11.94Gy,11.74Gy and 12.21Gy respectively; the percent of total lung volume received radiation exceeding 10Gy (V10) was 31.08%, 27.34%,27.01% and 27.40% respectively;the percent of total lung volume received radiation exceeding 20Gy (V20) was 22.27%,18.10%,17.47% and 18.63% respectively; the percent of total lung volume received radiation exceeding 30Gy (V30) was 13.48%, 9.70%,9.51% and 10.39% respectively, while IMRT groups was lower than 3DCRT, however, the percent of total lung volume received radiation exceeding 5Gy (V5) was 38.08%,41.67%,41.34% and 46.19% respectively;while IMRT groups was higher than 3DCRT, especially for MIMiC-IMRT. The percent of esophageal volume received radiation exceeding 50Gy (V50) was 22.77%,20.23%,19.99% and 20.34% respectively; while IMRT groups was lower than 3DCRT. The percent of heart volume received radiation exceeding 35Gy (V35) was 17.99%,13.37%,13.43% and 13.78% respectively; the isoeffective dose for 1/3 isoeffective heart volume(D1/3)was 15.74Gy,12.43Gy, 12.30Gy and 13.06Gy respectively, while IMRT groups was lower than 3DCRT. The mean dose of spiral cord was 18.51Gy,15.32Gy,14.69Gy and 15.55Gy respectively, while IMRT groups was lower than 3DCRT.Conclusions 1.By comparison of IMRT groups vs 3DCRT results above, we can conclude that the conformity of tumor target is improved in IMRT than 3DCRT, while homogeneity is declined on the contrary.2. The MLD, lung V10, lung V20 and lung V30 are much decreased in IMRT, while the lung V5 increased on the contrary, especially for MIMiC-IMRT.3.The protection of esophagus, heart and spinal cord is much better in IMRT than 3DCRT.4.Homogeneity of tumor target under MIMiC-IMRT is much decreased than that of DMLC-IMRT, while the lung V5 result is increased on the contrary by comparison.5.The dosimetric distribution of tumor target and surrounding normal tissue, between 5-beam and 7-beam DMLC-IMRT, can not be differentiate significantly.
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