Analysis Of Target Volume And Dosimetry In 3D Conformal Radiation Therapy For NSCLC

Objective To assess and delineate the dosimetric shortcomings of conventional radiotherapy planning ,as compared with the three dimensional treatment planning system , and to obtain a better technique in the treatment of lung cancers. Methods Using the eclipse 6.5 treatment planning system , three different methods of radiotherapy planning : conventional planning , conventional and conformal planning , and conformal planning were designed for the patient. The total radiation dose was 66 Gy and DVH were used to assess the dosimetric distribution in the gross tumor volume and the surrounding organs at risk. Results Three designs are able to meet the demands of dosimetric requirements for radiation treatment of lung cancers. The maximum dose at GTV were 69.9 Gy,69 Gy,70.6 Gy; and the minimum dose were63 Gy,61.5 Gy,61.7 Gy ; the mean dose were 66.2 Gy,66.3 Gy,68.1 Gy . The maximum dose at CTV3 were 70.3 Gy,69.2 Gy,70.8 Gy; and the minimum dose were57.3 Gy,54.9 Gy,60.1 Gy ; the mean dose were 66.2 Gy,66.17 Gy,68 Gy. The left lung volumes which received radiation dose of ≥20 Gy (V20) at the three designs were 46.7 %,36.7%和37.5%;and ≥30 Gy(V30) were 35.9%,29.2%,25.8;the mean dose were 6.2 Gy,4.9 Gy,7.4 Gy. The right lung volumes which received radiation dose of ≥20 Gy (V20) at the three designs were12%,4.2 %和4.6%;and ≥30 Gy(V30) were 7.92%,3.3%,4.2%; the mean dose were 6.2 Gy,4.9 Gy,7.4 Gy。The whole lung volumes which received radiation dose of ≥20 Gy (V20) at the three designs were 25%,16.3 %和17.2 %; and ≥30 Gy(V30) were18.9%,13.6%,12.5%; the mean dose were12.8 Gy,11 Gy,11.5. The esophageal volume which received radiation of ≥45 Gy (V45) were 34.2%,23.4%和17.9%; the esophageal volume which received radiation of ≥50 Gy (V50) were 29%,20%和11.8%;the volume which received radiation of ≥60 Gy (V60) were 18.7%,6.69%和4.2%.The maximum dose at the spinal cord were 43.4 Gy,46.5 Gy和26.1 Gy ;and the minimum dose were1.36 Gy,0.16 Gy,0.93 Gy ; the mean dose were 10.4 Gy,10.5 Gy,2.1 Gy。The radiation dose to the 1/3 volume of heart were 45 Gy,43 Gy,21 Gy;the radiation dose to the 2/3 volume were 14 Gy,6.4 Gy,3.2 Gy; 1/2 volume dose were31 Gy,19 Gy,13.4 Gy。Conclusions Conventional radiotherapy planning is able to meet the demands of dosimetric requirements for radiation treatment of lung cancers. The three dimensional conformal radiation therapy planning system is able to provide superior delivery of high dose to the target volume without inflicting too high a risk to the surrounding normal tissues and organs.