Optimal acquisition scheme for flow-compensated intravoxel incoherent motion diffusion-weighted imaging in the abdomen: An accurate and precise clinically feasible protocol.
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<h4>Purpose</h4>Flow-compensated (FC) diffusion-weighted MRI (DWI) for intravoxel-incoherent motion (IVIM) modeling allows for a more detailed description of tissue microvasculature than conventional IVIM. The long acquisition time of current FC-IVIM protocols, however, has prohibited clinical application. Therefore, we developed an optimized abdominal FC-IVIM acquisition with a clinically feasible scan time.<h4>Methods</h4>Precision and accuracy of the FC-IVIM parameters were assessed by fitting the FC-IVIM model to signal decay curves, simulated for different acquisition schemes. Diffusion-weighted acquisitions were added subsequently to the protocol, where we chose the combination of b-value, diffusion time and gradient profile (FC or bipolar) that resulted in the largest improvement to its accuracy and precision. The resulting two optimized FC-IVIM protocols with 25 and 50 acquisitions (FC-IVIM<sub>opt25</sub> and FC-IVIM<sub>opt50</sub> ), together with a complementary acquisition consisting of 50 diffusion-weighting (FC-IVIM<sub>comp</sub> ), were acquired in repeated abdominal free-breathing FC-IVIM imaging of seven healthy volunteers. Intersession and intrasession within-subject coefficient of variation of the FC-IVIM parameters were compared for the liver, spleen, and kidneys.<h4>Results</h4>Simulations showed that the performance of FC-IVIM improved in tissue with larger perfusion fraction and signal-to-noise ratio. The scan time of the FC-IVIM<sub>opt25</sub> and FC-IVIM<sub>opt50</sub> protocols were 8 and 16 min. The best in vivo performance was seen in FC-IVIM<sub>opt50</sub> . The intersession within-subject coefficients of variation of FC-IVIM<sub>opt50</sub> were 11.6%, 16.3%, 65.5%, and 36.0% for FC-IVIM model parameters diffusivity, perfusion fraction, characteristic time and blood flow velocity, respectively.<h4>Conclusions</h4>We have optimized the FC-IVIM protocol, allowing for clinically feasible scan times (8-16 min).
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Radiotherapy Physics Modelling
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Magnetic resonance in medicine, 2020, 83 (3), pp. 1003 - 1015