Respiratory triggered 4D cone‐beam computed tomography: A novel method to reduce imaging dose. Issue 4 (11th March 2013)

• Record Type: Journal Article
• Authors: Cooper, Benjamin J.; O'Brien, Ricky T.; Balik, Salim; Hugo, Geoffrey D.; Keall, Paul J.
• Is Part Of: Medical physics. Volume 40:Issue 4(2013)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2013-03-11
• Subjects: Computed tomography -- Dosimetry/exposure assessment -- Pneumodyamics, respiration -- Image quality -- Reconstruction; computerised tomography -- data acquisition -- dosimetry -- image reconstruction -- medical image processing -- phantoms -- pneumodynamics; 4D cone‐beam computed tomography -- imaging dose -- respiratory motion -- respiratory triggered; Computerised tomographs -- Data acquisition and logging -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general; Cone beam computed tomography -- Medical imaging -- Medical image quality -- Medical image reconstruction -- Dosimetry -- Image reconstruction -- Cluster analysis -- Linear accelerators -- Anatomy -- Image guided radiation therapy; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4793724
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : A novel method called respiratory triggered 4D cone‐beam computed tomography (RT 4D CBCT) is described whereby imaging dose can be reduced without degrading image quality. RT 4D CBCT utilizes a respiratory signal to trigger projections such that only a single projection is assigned to a given respiratory bin for each breathing cycle. In contrast, commercial 4D CBCT does not actively use the respiratory signal to minimize image dose. Methods: : To compare RT 4D CBCT with conventional 4D CBCT, 3600 CBCT projections of a thorax phantom were gathered and reconstructed to generate a ground truth CBCT dataset. Simulation pairs of conventional 4D CBCT acquisitions and RT 4D CBCT acquisitions were developed assuming a sinusoidal respiratory signal which governs the selection of projections from the pool of 3600 original projections. The RT 4D CBCT acquisition triggers a single projection when the respiratory signal enters a desired acquisition bin; the conventional acquisition does not use a respiratory trigger and projections are acquired at a constant frequency. Acquisition parameters studied were breathing period, acquisition time, and imager frequency. The performance of RT 4D CBCT using phase based and displacement based sorting was also studied. Image quality was quantified by calculating difference images of the test dataset from the ground truth dataset. Imaging dose was calculated by counting projections. Results: : Using phase based sorting RT 4D CBCT results in 47% less imaging dose on average compared to conventional 4D CBCT. Image quality differences were less than 4% at worst. Using displacement based sorting RT 4D CBCT results in 57% less imaging dose on average, than conventional 4D CBCT methods; however, image quality was 26% worse with RT 4D CBCT. Conclusions: : Simulation studies have shown that RT 4D CBCT reduces imaging dose while maintaining comparable image quality for phase based 4D CBCT; image quality is degraded for displacement based RT 4D CBCT in its current implementation.