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dc.contributor.authorO'Shea, TPen_US
dc.contributor.authorBamber, JCen_US
dc.contributor.authorHarris, EJen_US
dc.identifier.citationMedical physics, 2016, 43 (1), pp. 455 - ?en_US
dc.description.abstract<h4>Purpose</h4>Ultrasound-based motion estimation is an expanding subfield of image-guided radiation therapy. Although ultrasound can detect tissue motion that is a fraction of a millimeter, its accuracy is variable. For controlling linear accelerator tracking and gating, ultrasound motion estimates must remain highly accurate throughout the imaging sequence. This study presents a temporal regularization method for correlation-based template matching which aims to improve the accuracy of motion estimates.<h4>Methods</h4>Liver ultrasound sequences (15-23 Hz imaging rate, 2.5-5.5 min length) from ten healthy volunteers under free breathing were used. Anatomical features (blood vessels) in each sequence were manually annotated for comparison with normalized cross-correlation based template matching. Five sequences from a Siemens Acuson™ scanner were used for algorithm development (training set). Results from incremental tracking (IT) were compared with a temporal regularization method, which included a highly specific similarity metric and state observer, known as the α-β filter/similarity threshold (ABST). A further five sequences from an Elekta Clarity™ system were used for validation, without alteration of the tracking algorithm (validation set).<h4>Results</h4>Overall, the ABST method produced marked improvements in vessel tracking accuracy. For the training set, the mean and 95th percentile (95%) errors (defined as the difference from manual annotations) were 1.6 and 1.4 mm, respectively (compared to 6.2 and 9.1 mm, respectively, for IT). For each sequence, the use of the state observer leads to improvement in the 95% error. For the validation set, the mean and 95% errors for the ABST method were 0.8 and 1.5 mm, respectively.<h4>Conclusions</h4>Ultrasound-based motion estimation has potential to monitor liver translation over long time periods with high accuracy. Nonrigid motion (strain) and the quality of the ultrasound data are likely to have an impact on tracking performance. A future study will investigate spatial uniformity of motion and its effect on the motion estimation errors.en_US
dc.format.extent455 - ?en_US
dc.subjectImage Processing, Computer-Assisteden_US
dc.subjectRadiotherapy, Image-Guideden_US
dc.subjectHealthy Volunteersen_US
dc.titleTemporal regularization of ultrasound-based liver motion estimation for image-guided radiation therapy.en_US
dc.typeJournal Article
rioxxterms.typeJournal Article/Reviewen_US
dc.relation.isPartOfMedical physicsen_US
pubs.notesNo embargoen_US
pubs.organisational-group/ICR/Primary Group
pubs.organisational-group/ICR/Primary Group/ICR Divisions
pubs.organisational-group/ICR/Primary Group/ICR Divisions/Radiotherapy and Imaging
pubs.organisational-group/ICR/Primary Group/ICR Divisions/Radiotherapy and Imaging/Imaging for Radiotherapy Adaptation
pubs.organisational-group/ICR/Primary Group/ICR Divisions/Radiotherapy and Imaging/Ultrasound & Optical Imaging
pubs.embargo.termsNo embargoen_US
icr.researchteamImaging for Radiotherapy Adaptationen_US
icr.researchteamUltrasound & Optical Imagingen_US
dc.contributor.icrauthorHarris, Emmaen_US
dc.contributor.icrauthorBamber, Jeffreyen_US

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