Four-Dimensional Cone-Beam Computed Tomography Image Compression Using Video Encoder for Radiotherapy
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Four-Dimensional Cone-Beam Computed Tomography Image Compression Using Video Encoder for Radiotherapy Hui Yan 1 & Yexiong Li 1 & Jianrong Dai 1
# Society for Imaging Informatics in Medicine 2020
Abstract Four dimensional cone-beam computed tomography (4D-CBCT) images were widely used for patient positing and target localization in radiotherapy. As consisting of multiple CBCT sets, it needs more time and space for data transferring and storage. In this study the feasibility of applying video coding algorithms for 4D-CBCT image compression was investigated. Prior to compression 4D-CBCT images were arranged in an order based on breathing phase or slice location for input sequence of video encoder. Median filtering was applied to suppress noise and artifact of 4D-CBCT for improved image quality. Three popular video coding algorithms (Motion JPEG 2000, Motion JPEG AVI, and MPEG-4) were tested and their performances were evaluated on a publicly available 4D-CBCT database. The average compression ratio of MPEG-4 was 135, while the values of Motion JPEG AVI and Motion JPEG 2000 were 16 and 7, respectively. The compression rate of two ordering methods was comparable and the location-based ordering method was slightly higher. With pre-processing of median filtering, the inter-frame similarity of input sequence was improved and the resulting compression rate was increased. MPEG-4 provided extremely higher compression rate for 4D-CBCT images. The ordering method based on slice location resulted in higher compression rate than the ordering method based on breathing phase. The median filtering was effective in improving inter-frame similarity and resulted in higher compression rate. The video coding algorithms are not only applicable for 4D image modalities but also feasible for serial 3D image modalities. Keywords 4D-CBCT . Video coding algorithm . Image compression
Introduction 4D-CBCT is an emerging imaging technique for monitoring organ motion of patient under radiotherapy. Internal organ motion caused by respiration or heartbeat is considerable. It is crucial to verify reproducibility of target location prior to treatment for lung and abdominal cancer patients [1–3]. Recently, the external and surface monitoring systems, such as RPM and OSMS (Varian Medical System, Palo Alto, USA), were used for patient positioning in radiotherapy. However they were not able to track the motion of internal target. Combining external surveillance signal with 4D-CBCT images was an effective way in monitoring real-time internal
* Jianrong Dai [email protected] 1
Department of Radiation Oncology, National Cancer Center/ National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100021, China
organ motion for high-precision treatment such as hypofraction radiotherapy or radiosurgery [4, 5]. In clinic, 4D-CBCT images were reconstructed from thousands of 2D X-ray projections acquired by an on-board kilovoltage imaging system while gantry rotates during multip
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