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KMID : 0858520150190040212
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Journal of the Korean Society of Magnetic Resonance in Medicine
2015 Volume.19 No. 4 p.212 ~ p.217
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Determination of Optimal Scan Time for the Measurement of Downstream Metabolites in Hyperpolarized 13C MRSI
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Lee Han-Sol
Lee Joon-Sung
Joe Eun-Hae
Yang Seung-Wook
Choi Young-suk
Wang Eun-Kyung
Song Ho-Taek
Kim Dong-Hyun
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Abstract
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Purpose: For a single time-point hyperpolarized 13C magnetic resonance spectroscopy imaging (MRSI) of animal models, scan-time window after injecting substrates is critical in terms of signal-to-noise ratio (SNR) of downstream metabolites. Prescans of time-resolved magnetic resonance spectroscopy (MRS) can be performed to determine the scan-time window. In this study, based on two-site exchange model, protocol-specific simulation approaches were developed for 13C MRSI and the optimal scan-time window was determined to maximize the SNR of downstream metabolites.
Materials and Methods: The arterial input function and conversion rate constant from injected substrates (pyruvate) to downstream metabolite (lactate) were precalibrated, based on pre-scans of time-resolved MRS. MRSI was simulated using two-site exchange model with considerations of scan parameters of MRSI. Optimal scan-time window for mapping lactate was chosen from simulated lactate intensity maps. The performance was validated by multiple in vivo experiments of BALB/C nude mice with MDA-MB-231 breast tumor cells. As a comparison, MRSI were performed with other scan-time windows simply chosen from the lactate signal intensities of prescan time-resolved MRS.
Results: The optimal scan timing for our animal models was determined by simulation, and was found to be 15 s after injection of the pyruvate. Compared to the simple approach, we observed that the lactate peak signal to noise ratio (PSNR) was increased by 230%.
Conclusion: Optimal scan timing to measure downstream metabolites using hyperpolarized 13C MRSI can be determined by the proposed protocol-specific simulation approaches.
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KEYWORD
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Hyperpolarized 13C, MRSI, Two-site exchange, Pyruvate, Lactate
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