Abstract
This study investigated the effects of respiratory motion, including unwanted breath holding, on the target volume and centroid position on four‐dimensional computed tomography (4DCT) imaging. Cine 4DCT images were reconstructed based on a time‐based sorting algorithm, and helical 4DCT images were reconstructed based on both the time‐based sorting algorithm and an amplitude‐based sorting algorithm. A spherical object 20 mm in diameter was moved according to several simulated respiratory motions, with a motion period of 4.0 s and maximum amplitude of 5 mm. The object was extracted automatically, and the target volume and centroid position in the craniocaudal direction were measured using a treatment planning system. When the respiratory motion included unwanted breath‐holding times shorter than the breathing cycle, the root mean square errors (RSME) between the reference and imaged target volumes were 18.8%, 14.0%, and 5.5% in time‐based images in cine mode, time‐based images in helical mode, and amplitude‐based images in helical mode, respectively. In helical mode, the RSME between the reference and imaged centroid position was reduced from 1.42 to 0.50 mm by changing the reconstruction method from time‐ to amplitude‐based sorting. When the respiratory motion included unwanted breath‐holding times equal to the breathing cycle, the RSME between the reference and imaged target volumes were 19.1%, 24.3%, and 15.6% in time‐based images in cine mode, time‐based images in helical mode, and amplitude‐based images in helical mode, respectively. In helical mode, the RSME between the reference and imaged centroid position was reduced from 1.61 to 0.83 mm by changing the reconstruction method from time‐ to amplitude‐based sorting. With respiratory motion including breath holding of shorter duration than the breathing cycle, the accuracies of the target volume and centroid position were improved by amplitude‐based sorting, particularly in helical 4DCT.
Highlights
| INTRODUCTIONFor patients with irregular breathing patterns, including unwanted breath‐holding, alignment errors
Example coronal images of the spherical object and helical 4DCT images of the spherical object: (a) spherical image scanned without movement, (b) helical 4DCT with time‐based images for Type B respiratory motion (80% phase), (c) helical 4DCT amplitude‐based images for
We investigated the effects of respiratory motion, including breath‐
Summary
For patients with irregular breathing patterns, including unwanted breath‐holding, alignment errors. Advances in technology have led to the development of high‐preci[1,2,3] sion radiotherapy that can capture moving targets. Beam CT, which may result in under‐dosage to the target volume.[19] this, the technology must recognize the motion of a target during. This study investigated the effects of respiratory motion, includthe planning of radiation treatment. Four‐dimensional computed ing breath‐holding, on the target volume and centroid position of tomography (4DCT) has been used to obtain temporal and spatial
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