Measure Partial Liver Volumetric Variations from Paired Inspiratory-expiratory Chest CT Scans

Liver stiffness is an essential clinical biomarker for diagnosing liver fibrosis and cirrhosis. In current clinical practice, elastography techniques are standard non-invasive diagnosis tools to assess stiffness of liver, using either Ultrasound (US) or magnetic resonance imaging (MRI). However, the US elastography yields ≈ 10 % failure rate and degraded performance on obese patients, while the MR elastography is costlier and less available. Compared with US and MRI, the computerized tomography (CT) imaging has not been widely used in measuring liver stiffness. In this paper, we performed a pilot study to assess if volumetric variations of liver can be captured from paired inspiratory-expiratory chest (PIEC) CT scans. To enable the assessment, we propose a Hierarchical Intra-Patient Organ-specific (HIPO) registration pipeline to quantify the partial liver volumetric variations with lung pressure from a respiratory cycle. The PIEC protocol is employed since it naturally provides two paired CT scans with liver deformation from regulated respiratory motions. For the subjects whose registration results passed both an automatic quantitative quality assurance (QA) and another visual qualitative QA, 6.0% average volumetric variations of liver were measured, from inspiratory phase to expiratory phase. Future clinical validations will be required to validate the findings in this pilot study.