| Background and Objectives:Being further developed from the image guided radiation therapy (IGRT), adaptive radiation therapy (ART) is a precise radiation therapy for clinical applications. In this thesis, we have collected real-time images by using a kilo-voltage (kV) cone beam CT (CBCT), and designed two plans based on ART and hypofractionated intensity-modulated radiation therapy (IMRT) to compare the dosimetric differences on the target volume and the surrounding normal tissues. The clinical significance of this method on lung cancer radiation therapy has been investigated.Methods:Eight lung cancer patients were selected for this study. The radiotherapy target was located by normal enhanced CT scanning. In the obtained CT images, internal gross tumor volume (IGTV1), internal target volume (ITV1), PIGTV1,planning target volume (PTV1) and the organ at risk (OAR) were defined, respectively. And then hypofractionated IMRT was planned and performed. The kV CBCT scanning was carried out before every radiation, and totally12CBCT images have been obtained for every patient. Both the CBCT image and planning CT image were transferred to the CMS planning system via internet, and then the distortion alignment and image fusion were conducted subsequently. In the fused image the internal gross tumor volume (IGTV2), internal target volume (ITV2), PIGTV2,planning target volume (PTV2)and OAR were re-defined. ITV were formed by extending IGTV for0.5cm. In the conventional CT location, PTV was derived form ITV plus the conventional safety margins (including setup error and organ motion induced error):extending0.5cm,Xio panning system was used to design radiation therapeutic plans based on the new profiles obtained from the CT images. Prescription dosage, field quantity, angle and optimization conditions were exactly identical to the original plans, ensuring the OAR dosage less than their tolerance dose. And then the fractionated dose, accumulated dose, the dose-volume histogram (DVH) of the internal gross target volume (IGTV), as well as the radiation dose of the normal lung and spinal cord surrounding the target volume, have been compared and analyzed to evaluate the better lung radiation therapy between the hypofractionated IMRT plan and ART plan.Results:18patients (96plans) IGTV volume range of2.52～223.96cm3average volume87.24cm3, and patients with tumor target volume (IGTV) with the number of treatments increased gradually reduced.2The accumulated maximum, minimum and average doses are:ART plan (68.88±1.35Gy49.93±2.70Gy65.62±1.10Gy), IMRT plan (68.77±1.05Gy49.85±3.05Gy65.02±0.47Gy).3Statistical analysis on V5, V10, V20, V30, V40of the diseased, healthy and whole lungs shows ART plan<IMRT plan,(P values are0.000,0.000,0.000,0.000and0.000;0.000,0.000,,1,0.000;0.000,0.000,0.000,0.000,0.000) with a significant difference.4The accumulated maximum dose of spinal cord:ART plan is21.76±7.97cGy, IMRT plan is23.39±7.89cGy; ART plan<IMRT plan,(P<0.05) with a significant difference.Conclusions:1In non-small cell lung cancer radiation therapy process, with the treatment time passing, lung tumor target volume was significantly reduced, if we don’t change the range of radiation field, normal lung tissue’s exposed volume will be increased.2In lung cancer radiotherapy, cone-beam CT (CBCT) can be applicated to observe the changing of the tumor volume, which lays out the new targets outside the contour, re-designing the radiation treatment planning in order to achieve adaptive radiotherapy.3According to the target volume size fractionated, the shape changes in the design of the adaptive plan compared with the three-dimensional conformal intensity-modulated radiotherapy plan, with significant geometry and dosimetric advantage, reducing thevolume and dose of normal organs and tissues exposed can also betargetprescription dose increased, reducing the incidence of radiation complications, andimprove tumor control rate. |
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