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Investigation On Fast Reconstruction of Time-Resolved 4DMRI with Dynamic Keyhole Method Using Respiratory-Correlated Image Library

Y Liu1*, K Zakian2 , M Kadbi3 , J Deasy4 , G Li5 , (1) Memorial Sloan Kettering Cancer Center, New York, NY, (2) Memorial Sloan Kettering Cancer Center, New York, NY, (3) Philips Healthcare, Cleveland, OH, (4) Memorial Sloan Kettering Cancer Center, New York, NY, (5) Memorial Sloan Kettering Cancer Center, New York, NY


(Thursday, 7/18/2019) 7:30 AM - 9:30 AM

Room: 303

Purpose: 4DMRI are classified as either time-resolved (TR) or respiratory-correlated (RC); the former demonstrates real-time motion but with low spatial-dimensionality, while the latter provides high spatial-dimensionality but only one representative breathing cycle. This study aims to achieve novel time-resolved 4DMRI (TR-4DMRI) with high spatiotemporal resolution using dynamic keyhole (DKH) method with RC-4DMRI image library for motion assessment.

Methods: As a proof-of-concept, fast MRI scanning protocol with parallel imaging was applied on a digital motion phantom (ground truth) to acquire low spatial-resolution (4x4x4mm3) 3D cine (temporal-resolution: 2Hz) and high spatial-resolution (2x2x2mm3) RC-4DMRI library, under free-breathing condition. The RC-4DMRI library was built from 10-state breathing cycle. A super-resolution concept is applied to reconstruct TR-4DMRI by combining high temporal-resolution but low spatial-resolution 3D cine and a high spatial-resolution but only 10-phase library image in k-space. For each frame of the 3D cine, two image matching steps were performed between cine and library images: the first step selected one 3D image (representing one respiratory phase), that best matches internal motion status of the cine, from 10-state RC-4DMRI; the second step normalizes the k-space data intensity, to combine them (a 3D cine + a matched library image) in k-space using DKH to reconstruct TR-4DMRI. The TR-4DMRI image quality was evaluated by comparing it with the ground truth based on mean voxel intensity difference (VID) and voxel intensity correlation (VIC).

Results: TR-4DMRI reconstructed from updating central k-space data demonstrated adequate real-time motion information with fine structure details. Comparing the image quality of reconstructed TR-4DMRI and RC-4DMRI, VID=3% and VIC=0.98.

Conclusion: This study investigates the feasibility of TR-4DMRI reconstruction with dynamic keyhole method using an RC-4DMRI image library. It demonstrates motion continuously with adequate spatiotemporal resolution. Further human subject study is on-going. This technique has great potential to achieve real-time 4DMRI performance with clinically preferable spatiotemporal resolution.


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