Abstract
The purpose of this study was to compare three computed tomography (CT) images under different conditions—average intensity projection (AIP), free breathing (FB), mid‐ventilation (MidV)—used for radiotherapy contouring and planning in lung cancer patients. Two image sets derived from four‐dimensional CT (4DCT) acquisition (AIP and MidV) and three‐dimensional CT with FB were generated and used to plan for 29 lung cancer patients. Organs at risk (OARs) were delineated for each image. AIP images were calculated with 3D conformal radiotherapy (3DCRT) and intensity‐modulated radiation therapy (IMRT). Planning with the same target coverage was applied to the FB and MidV image sets. Plans with small and large tumors were compared regarding OAR volumes, geometrical center differences in OARs, and dosimetric indices. A gamma index analysis was also performed to compare dose distributions. There were no significant differences (P > 0.05) in OAR volumes, the geometrical center differences, maximum and mean doses of the OARs between both tumor sizes. For 3DCRT, the gamma analysis results indicated an acceptable dose distribution agreement of 95% with 2%/2 mm criteria. Although, the gamma index results show distinct contrast of dose distribution outside the planning target volume (PTV) in IMRT, but within the PTV, it was acceptable. All three images could be used for OAR delineation and dose calculation in lung cancer. AIP image sets seemed to be suitable for dose calculation while patient movement between series acquisition of FB images should be considered when defining target volumes on 4DCT images.
Highlights
Advances in radiation therapy, radiation doses can be tightly conformed to target volumes while minimizing dose delivery to surrounding normal organs.[1,2] Respiratory motion is a significant and challenging problem in radiation therapy due to geometrical uncertainties of both the target and normal organs in the thoracoabdominal region.[3]
For 3D radiation treatment planning in lung cancer, the internal target volume (ITV) was delineated on maximum intensity projection (MIP) images, whereas organ at risk (OAR) contouring and static 3D dose calculation were done with 3DCT images.[9,10,11,12]
The movement resulted in unmatched free breathing (FB) and 4DCT images in the series, which could be a potential source of error
Summary
Radiation doses can be tightly conformed to target volumes while minimizing dose delivery to surrounding normal organs.[1,2] Respiratory motion is a significant and challenging problem in radiation therapy due to geometrical uncertainties of both the target and normal organs in the thoracoabdominal region.[3]. | 27 underdosage to tumor and overdosage to normal organs, and significantly diverted the planned and the delivered doses.[4] Several approaches have been developed to manage the effects of respiratory motion during radiation therapy.[5,6] One of them is a motionencompassing method, which addresses the entire range of tumor motion and adds a margin to the target volumes. For 3D radiation treatment planning in lung cancer, the ITV was delineated on maximum intensity projection (MIP) images, whereas organ at risk (OAR) contouring and static 3D dose calculation were done with 3DCT images.[9,10,11,12]
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