Motion Compensated Abdominal Diffusion Weighted MRI by Simultaneous Image Registration and Model Estimation (SIR-ME)
Non-invasive characterization of water molecule’s mobility variations by quantitative analysis of diffusion-weighted MRI (DW-MRI) signal decay in the abdomen has the potential to serve as a biomarker in gastrointestinal and oncological applications. Accur
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diology, Boston Children’s Hospital, Harvard Medical School, Boston, USA 2 Nuclear Medicine, Rabin Medical Center, Petah-Tikva, Israel
Abstract. Non-invasive characterization of water molecule’s mobility variations by quantitative analysis of diffusion-weighted MRI (DW-MRI) signal decay in the abdomen has the potential to serve as a biomarker in gastrointestinal and oncological applications. Accurate and reproducible estimation of the signal decay model parameters is challenging due to the presence of respiratory, cardiac, and peristalsis motion. Independent registration of each b-value image to the b-value=0 s/mm2 image prior to parameter estimation might be sub-optimal because of the low SNR and contrast difference between images of varying b-value. In this work, we introduce a motion-compensated parameter estimation framework that simultaneously solves image registration and model estimation (SIR-ME) problems by utilizing the interdependence of acquired volumes along the diffusion weighting dimension. We evaluated the improvement in model parameters estimation accuracy using 16 in-vivo DW-MRI data sets of Crohn’s disease patients by comparing parameter estimates obtained using the SIR-ME model to the parameter estimates obtained by fitting the signal decay model to the acquired DW-MRI images. The proposed SIR-ME model reduced the average root-mean-square error between the observed signal and the fitted model by more than 50%. Moreover, the SIR-ME model estimates discriminate between normal and abnormal bowel loops better than the standard parameter estimates. Keywords: Diffusion-weighted imaging, abdomen, motion compensation, Crohn’s disease, block matching registration.
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Introduction
DW-MRI enables characterization of the tissue microenvironment by measuring variations in the mobility of water molecules due to cellularity, cell membrane
This work is supported by the National Institute of Diabetes & Digestive & Kidney Diseases of the NIH under award R01DK100404 and by the Translational Research Program at Boston Childrens Hospital. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.
c Springer International Publishing Switzerland 2015 N. Navab et al. (Eds.): MICCAI 2015, Part III, LNCS 9351, pp. 501–509, 2015. DOI: 10.1007/978-3-319-24574-4_60
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integrity, and the compartment in which water molecules are located (intravascular, extracellular, or intracellular spaces) [1]. The water molecule mobility leads to attenuation in the diffusion signal, which is measured at multiple b-values. The signal decay at high b-values associated with the slow-diffusion component reflects water molecules’ mobility in the tissue and the decay at low b-values associated with the fast-diffusion component reflects micro-capillaries’ blood flow. Combined with an appropriate model, the variations in both fast and slow diffusion between normal tissue and regions with pathology can be quantified. Quantitative DW-MRI has been increasingly used for vario
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