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- Title
Specialized computational methods for denoising, B<sub>1</sub> correction, and kinetic modeling in hyperpolarized <sup>13</sup>C MR EPSI studies of liver tumors.
- Authors
Lee, Philip M.; Chen, Hsin‐Yu; Gordon, Jeremy W.; Zhu, Zihan; Larson, Peder E.Z.; Dwork, Nicholas; Van Criekinge, Mark; Carvajal, Lucas; Ohliger, Michael A.; Wang, Zhen J.; Xu, Duan; Kurhanewicz, John; Bok, Robert A.; Aggarwal, Rahul; Munster, Pamela N.; Vigneron, Daniel B.
- Abstract
Purpose: To develop a novel post‐processing pipeline for hyperpolarized (HP) 13C MRSI that integrates tensor denoising and B1+ correction to measure pyruvate‐to‐lactate conversion rates (kPL) in patients with liver tumors. Methods: Seven HP 13C MR scans of progressing liver tumors were acquired using a custom 13C surface transmit/receive coil and the echo‐planar spectroscopic imaging (EPSI) data analysis included B0 correction, tensor rank truncation, and zero‐ and first‐order phase corrections to recover metabolite signals that would otherwise be obscured by spectral noise as well as a correction for inhomogeneous transmit (B1+) using a B1+ map aligned to the coil position for each patient scan. Processed HP data and corrected flip angles were analyzed with an inputless two‐site exchange model to calculate kPL. Results: Denoising averages SNR increases of pyruvate, lactate, and alanine were 37.4‐, 34.0‐, and 20.1‐fold, respectively, with lactate and alanine dynamics most noticeably recovered and better defined. In agreement with Monte Carlo simulations, over‐flipped regions underestimated kPL and under‐flipped regions overestimated kPL. B1+ correction addressed this issue. Conclusion: The new HP 13C EPSI post‐processing pipeline integrated tensor denoising and B1+ correction to measure kPL in patients with liver tumors. These technical developments not only recovered metabolite signals in voxels that did not receive the prescribed flip angle, but also increased the extent and accuracy of kPL estimations throughout the tumor and adjacent regions including normal‐appearing tissue and additional lesions.
- Subjects
LIVER tumors; MONTE Carlo method; ECHO-planar imaging; SPECTROSCOPIC imaging; PATIENT positioning
- Publication
Magnetic Resonance in Medicine, 2021, Vol 86, Issue 5, p2402
- ISSN
0740-3194
- Publication type
Article
- DOI
10.1002/mrm.28901