Abstract
The image‐guided radiotherapy technique (IGRT) makes use of imaging devices to verify the positions of the target volume and organs at risk during the treatment sessions. In this work we evaluate the image quality provided by an imaging system based on a kilovoltage cone‐beam CT, and explore its ability to perform IGRT and adaptive radiotherapy. We analyze the accuracy of the image slice width, the spatial resolution using the MTF function, the image uniformity, the signal‐to‐noise ratio, the contrast‐to‐noise ratio, the low‐contrast sensitivity, and the HU linearity with density. The studied parameters are evaluated in an objective and quantitative way, allowing for a direct comparison with other imaging devices. We conclude that the analyzed cone‐beam imaging system is adequate to accurately perform IGRT within its clinical use, despite the high level of noise present in a cone beam caused by scatter. We also point out the presence of a bowtie wobble artifact in the reconstructed images. Nevertheless, we conclude that these features do not limit the capability of the system to perform adaptive radiotherapy in most cases.PACS number: 87.57.‐s
Highlights
Successful external radiotherapy requires the ability to reproduce in the treatment room the patient setup used in the simulation
The conventional method consists in the acquisition of two orthogonal planar megavoltage images (2D) with an electronic portal imaging device (EPID).(1) The comparison between these images and the digitally reconstructed radiographs (DRR) leads to an anatomic registration based on high-contrast areas such as bony structures
We present a study of the volumetric conebeam computed tomography (CBCT) image quality obtained with the on-board imager (OBI) system to test its capability to perform both image-guided radiotherapy technique (IGRT) and adaptive radiotherapy (ART)
Summary
Successful external radiotherapy requires the ability to reproduce in the treatment room the patient setup used in the simulation. The conventional method consists in the acquisition of two orthogonal planar megavoltage images (2D) with an electronic portal imaging device (EPID).(1) The comparison between these images and the digitally reconstructed radiographs (DRR) leads to an anatomic registration based on high-contrast areas such as bony structures. This method does not discriminate soft tissue. Some modern imaging systems, such as those based on a kilovoltage cone beam (kV CBCT) allow obtaining tomographic images of the patient that can be directly compared with the CT planning study They provide information of low-contrast structures, which make possible the registration based on areas with soft tissue
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