title: Multi-atlas and unsupervised learning approach to perirectal space segmentation in CT images.
abstract: Perirectal space segmentation in computed tomography images aids in quantifying radiation dose received by healthy tissues and toxicity during the course of radiation therapy treatment of the prostate. Radiation dose normalised by tissue volume facilitates predicting outcomes or possible harmful side effects of radiation therapy treatment. Manual segmentation of the perirectal space is time consuming and challenging in the presence of inter-patient anatomical variability and may suffer from inter- and intra-observer variabilities. However automatic or semi-automatic segmentation of the perirectal space in CT images is a challenging task due to inter patient anatomical variability, contrast variability and imaging artifacts. In the model presented here, a volume of interest is obtained in a multi-atlas based segmentation approach. Un-supervised learning in the volume of interest with a Gaussian-mixture-modeling based clustering approach is adopted to achieve a soft segmentation of the perirectal space. Probabilities from soft clustering are further refined by rigid registration of the multi-atlas mask in a probabilistic domain. A maximum a posteriori approach is adopted to achieve a binary segmentation from the refined probabilities. A mean volume similarity value of 97% and a mean surface difference of 3.06 ± 0.51 mm is achieved in a leave-one-patient-out validation framework with a subset of a clinical trial dataset. Qualitative results show a good approximation of the perirectal space volume compared to the ground truth.
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH, 44106, USA.
authors.forename: Soumya
authors.initials: S
authors.lastname: Ghose
authors.affiliation: School of Medicine and Public Health, University of Newcastle, Callaghan, NSW, 2308, Australia.
authors.forename: James W
authors.initials: JW
authors.lastname: Denham
authors.affiliation: Radiation Oncology, Sir Charles Gairdner Hospital, Hospital Ave, Nedlands, WA, 6009, Australia. Martin.Ebert@health.wa.gov.au.|School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia. Martin.Ebert@health.wa.gov.au.
authors.forename: Martin A
authors.identifier: http://orcid.org/0000-0002-6875-0719
authors.initials: MA
authors.lastname: Ebert
authors.affiliation: Radiation Oncology, Sir Charles Gairdner Hospital, Hospital Ave, Nedlands, WA, 6009, Australia.
authors.forename: Angel
authors.initials: A
authors.lastname: Kennedy
authors.affiliation: Department of Biomedical Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH, 44106, USA.
authors.forename: Jhimli
authors.initials: J
authors.lastname: Mitra
authors.affiliation: Australian e-Health Research Centre, CSIRO, Brisbane, QLD, 4029, Australia.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Dowling
mesh_terms: D000465:Algorithms; D016000:Cluster Analysis; D019992:Databases as Topic; D006801:Humans; D011857:Radiographic Image Interpretation, Computer-Assisted; D012007:Rectum / Q000000981:diagnostic imaging*; D012044:Regression Analysis; D014057:Tomography, X-Ray Computed; D000069558:Unsupervised Machine Learning
keywords: Autosegmentation; Gaussian mixture model; Multi-atlas segmentation; Perirectal space