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CEST MR-Fingerprinting: practical considerations and insights for acquisition schedule design and improved reconstruction
{Purpose To understand the influence of various acquisition parameters on the ability of CEST MR-Fingerprinting (MRF) to discriminate different chemical exchange parameters and to provide tools for optimal acquisition schedule design and parameter map reconstruction. Methods Numerical simulations were conducted using a parallel computing implementation of the Bloch-McConnell equations, examining the effect of TR, TE, flip-angle, water urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0011 and urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0012, saturation-pulse duration, power, and frequency on the discrimination ability of CEST-MRF. A modified Euclidean distance matching metric was evaluated and compared to traditional dot product matching. L-Arginine phantoms of various concentrations and pH were scanned at 4.7T and the results compared to numerical findings. Results Simulations for dot product matching demonstrated that the optimal flip-angle and saturation times are urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0013 and 1100 ms, respectively. The optimal maximal saturation power was 3.4 $\mu$T for concentrated solutes with a slow exchange rate, and 5.2 $\mu$T for dilute solutes with medium-to-fast exchange rates. Using the Euclidean distance matching metric, much lower maximum saturation powers were required (1.6 and 2.4 $\mu$T, respectively), with a slightly longer saturation time (1500 ms) and urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0014 flip-angle. For both matching metrics, the discrimination ability increased with the repetition time. The experimental results were in agreement with simulations, demonstrating that more than a 50\textpercent reduction in scan-time can be achieved by Euclidean distance-based matching. Conclusions Optimization of the CEST-MRF acquisition schedule is critical for obtaining the best exchange parameter accuracy. The use of Euclidean distance-based matching of signal trajectories simultaneously improved the discrimination ability and reduced the scan time and maximal saturation power required.}
@article{item_3051977, title = {{CEST MR-Fingerprinting: practical considerations and insights for acquisition schedule design and improved reconstruction}}, journal = {{Magnetic Resonance in Medicine}}, abstract = {{Purpose To understand the influence of various acquisition parameters on the ability of CEST MR-Fingerprinting (MRF) to discriminate different chemical exchange parameters and to provide tools for optimal acquisition schedule design and parameter map reconstruction. Methods Numerical simulations were conducted using a parallel computing implementation of the Bloch-McConnell equations, examining the effect of TR, TE, flip-angle, water urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0011 and urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0012, saturation-pulse duration, power, and frequency on the discrimination ability of CEST-MRF. A modified Euclidean distance matching metric was evaluated and compared to traditional dot product matching. L-Arginine phantoms of various concentrations and pH were scanned at 4.7T and the results compared to numerical findings. Results Simulations for dot product matching demonstrated that the optimal flip-angle and saturation times are urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0013 and 1100 ms, respectively. The optimal maximal saturation power was 3.4 $\mu$T for concentrated solutes with a slow exchange rate, and 5.2 $\mu$T for dilute solutes with medium-to-fast exchange rates. Using the Euclidean distance matching metric, much lower maximum saturation powers were required (1.6 and 2.4 $\mu$T, respectively), with a slightly longer saturation time (1500 ms) and urn:x-wiley:07403194:media:mrm27937:mrm27937-math-0014 flip-angle. For both matching metrics, the discrimination ability increased with the repetition time. The experimental results were in agreement with simulations, demonstrating that more than a 50\textpercent reduction in scan-time can be achieved by Euclidean distance-based matching. Conclusions Optimization of the CEST-MRF acquisition schedule is critical for obtaining the best exchange parameter accuracy. The use of Euclidean distance-based matching of signal trajectories simultaneously improved the discrimination ability and reduced the scan time and maximal saturation power required.}}, volume = {83}, number = {2}, pages = {462--478}, publisher = {Wiley-Liss}, address = {New York}, year = {2020}, slug = {item_3051977}, author = {Perlman, O and Herz, K and Zaiss, M and Cohen, O and Rosen, MS and Farrar, CT} }