ObjectivesLiver volumetry has emerged as an important tool in clinical practice. Liver volume is assessed primarily via organ segmentation of computed tomography (CT) and magnetic resonance imaging (MRI) images. The goal of this paper is to provide an accessible overview of liver segmentation targeted at radiologists and other healthcare professionals.MethodsUsing images from CT and MRI, this paper reviews the indications for liver segmentation, technical approaches used in segmentation software and the developing roles of liver segmentation in clinical practice.ResultsLiver segmentation for volumetric assessment is indicated prior to major hepatectomy, portal vein embolisation, associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) and transplant. Segmentation software can be categorised according to amount of user input involved: manual, semi-automated and fully automated. Manual segmentation is considered the “gold standard” in clinical practice and research, but is tedious and time-consuming. Increasingly automated segmentation approaches are more robust, but may suffer from certain segmentation pitfalls. Emerging applications of segmentation include surgical planning and integration with MRI-based biomarkers.ConclusionsLiver segmentation has multiple clinical applications and is expanding in scope. Clinicians can employ semi-automated or fully automated segmentation options to more efficiently integrate volumetry into clinical practice.Teaching points• Liver volume is assessed via organ segmentation on CT and MRI examinations.
• Liver segmentation is used for volume assessment prior to major hepatic procedures.
• Segmentation approaches may be categorised according to the amount of user input involved.
• Emerging applications include surgical planning and integration with MRI-based biomarkers.
Electronic supplementary materialThe online version of this article (doi:10.1007/s13244-017-0558-1) contains supplementary material, which is available to authorised users.
Pulmonary embolism (PE) can be life-threatening and, when suspected, is usually investigated by computed tomographic pulmonary angiogram (CTPA). Concerns related to overutilization and harmful ionizing radiation have identified CTPA as an area in need of resource stewardship. 1,2 The purpose of this study was to explore interphysician variability in CTPA diagnostic yield and to identify any associated physician characteristics that could inform an intervention to reduce overuse in our institution.Methods | We retrospectively reviewed all CTPAs at an academic teaching hospital in Montreal, Quebec, Canada, from September 2014 to January 2016. Studies were classified as positive or negative; indeterminate examinations, and those performed for chronic pulmonary emboli were excluded. A total of 1394 examinations ordered by 182 physicians were included, of which 199 (14.3%) were positive and 1195 (85.7%) were negative. A multivariable logistic regression analysis was performed to explore whether physician specialty, years in practice, physician sex, or total numbers of studies ordered per physician were associated with CTPA diagnostic yield. We used a generalized estimating equations (GEE) approach to account for patients who underwent repeated examinations over the study period. 3 Statistical tests of hypothesis were 2-sided with a significance of P ≤ .05. All analyses were performed using SAS statistical software (version 9.4, SAS Institute Inc). The McGill University Health Centre research ethics board approved this study.
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