Multi-Atlas-Based Segmentation of Pelvic Structures from CT Scans for Planning in Prostate Cancer Radiotherapy

Abstract

In prostate cancer radiotherapy, the accurate identification of the prostate and organs at risk in planning computer tomography (CT) images is an important part of the therapy planning and optimization. Manually contouring these organs can be a time consuming process and subject to intra-and inter-expert variability. Automatic identification of organ boundaries from these images is challenging due to the poor soft tissue contrast. Atlas-based approaches may provide a priori structural information by propagating manual expert delineations to a new individual space; however the inter-individual variability and registration errors may lead to biased results. Multiatlas approaches can partly overcome some of these difficulties by selecting the most similar atlases among a large data base but the definition of similarity measure between the available atlases and the query individual has still to be addressed. The purpose of this chapter is to explain atlas-based segmentation approaches and the evaluation of different atlas-based strategies to simultaneously segment prostate, bladder and rectum from CT images. A comparison between single and multiple atlases is performed. Experiments on atlas ranking, selection strategies and fusion decision rules are carried out to illustrate the presented methodology. Propagation of labels using two registration strategies are applied and the results of the comparison with manual delineations are reported.

Multi-atlas segmentation of biomedical images: A survey

“…Outside brain imaging, the prevalence of prostate cancer in men has sparked interest in applications within prostate imaging, using modalities such as MRI (Langerak et al, 2010; Litjens et al, 2014; Rivest-Hénault et al, 2014), CT (Acosta et al, 2011; Sjöberg et al, 2013; Acosta et al, 2014) and ultrasound (Nouranian et al, 2014). Likewise, interest in radiotherapy treatment planning has been the main driver of applications in head, neck, and thoracic CT segmentation (Han et al, 2008; Wang et al, 2014c), which have mainly focused on segmenting tumors (Ramus and Malandain, 2010), organs at risk (e.g, the parotid glands, Fritscher et al 2014; Gorthi et al 2010; Han et al 2010; Hollensen et al 2010; Yang et al 2010 or mediastinal lymph nodes, Liu et al 2014) and lymph node metastases (Sjöberg et al, 2013; Teng et al, 2010).…”

Multi-atlas-based segmentation of prostatic urethra from planning CT imaging to quantify dose distribution in prostate cancer radiotherapy

“…As shown in figure A2(Supplemental material), more similar atlas yields a better segmentations if only one single atlas was used for segmentation . Then, adding multiple atlases improves the accuracy when fusing labels from the closest atlas [29]. Other global or local features based on CT intensity or shape descriptors may have been proposed (mutual information, cross correlation, SPHARM, etc.…”

“…This allows to overcome the interindividual variability and registration issues. Previous works have shown the benefits of combining multiple atlases in improving segmentation accuracy [20,22,23,[27][28][29].…”

Advances in Biomedical Imaging and Image Fusion

“…CT accurately outlines the bone, some soft tissue and blood vessels inside body; it is geometrically accurate, with short scan times and high resolution. CT fails to characterize tissue, transverse slices and there is a restriction on intensity of X-rays for short scan times and lastly the radiation can be harmful and not recommended for patients diagnosed with cancer or pregnant women [12,23].…”

“…CT is also used in radiation therapy and planning prostate cancer radiotherapy [7,11]. The latest research trends in CT are in areas of registration, segmentation of veins, tumors in brain, lesion in liver, aorta, prostrate, reconstruction of CT images, generation of 3D CT images, superposition of cone-based CT images and generation of synthetic 4D CT images for image guided surgery [4,[12][13][14][15][16][17][18][19][20][21][22]. CT accurately outlines the bone, some soft tissue and blood vessels inside body; it is geometrically accurate, with short scan times and high resolution.…”