Improvement Of Stereotactic Body Radiotherapy in Lung Tumors By Sparing Normal Tissues Using RapidArc Technique

Abstract

The major objectives are 1)To improve the efficiency of stereotactic body radiotherapy, 2)To optimize treatment volumes by 3D-CT and pneumatic abdominal compression device, and 3)To predict the radiobiological efficiency.Vac-Lok cushion with indexing feature was used for immobilizing the patient.A pneumatic abdominal compression apparatus (PACA) comprising a commercially available sphygmomanometer and nylon strap with a Velcro fastener was used for treatment of the patients.CT images were acquired using a helical CT machine.The patient was allowed for shallow breathing and CT images were acquired at a random phase of breathing (RB) when the patient was immobilized along with the inflated sphygmomanometer. This CT dataset was used as the reference image for planning.On account of tumor shift during respiratory motions,two more CT datasets were acquired at deep inspiration breath hold (DIBH) and deep expiration breath holds (DEBH).CT imaging data was imported to ARIA for contouring and planning. GTV was delineated on CT images which were acquired during all breathing phases with abdominal compression. Internal treatment volume (ITV) is the volume within which the tumor oscillates during a particular breathing pattern. DelineatedGTVs on all three phases were combined to generate ITV on the reference image (RB). The critical organs such as lungs, spinal cord, esophagus, ribs, and chest wall, which are at high risk of exposure, were contoured on CT dataset from the RB phase with abdominal compression.A TrueBeam STx platform Linac device equipped with HD120 MLC was used to deliver the SBRT-Lung plan.RapidArc® technique using the External Beam Planning (Version 13.0.33) feature of Eclipse was used to deliver the prescribed dose of 50 Gy in five fractions of 10 Gy each for the PTV.Finding suggest that RapidArc-SBRT is one potential cancer directed immune therapeutic modality and have tremendous potential for rescuing patients from death from most aggressive NSCLC. newline