Determination of Optimal Scan Time for the Measurement of Downstream Metabolites in Hyperpolarized 13C MRSI
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Purpose: For a single time-point hyperpolarized 13C magnetic resonance spectroscopyimaging (MRSI) of animal models, scan-time window after injecting substrates iscritical in terms of signal-to-noise ratio (SNR) of downstream metabolites. Prescansof time-resolved magnetic resonance spectroscopy (MRS) can be performed todetermine the scan-time window. In this study, based on two-site exchange model,protocol-specific simulation approaches were developed for 13C MRSI and the optimalscan-time window was determined to maximize the SNR of downstream metabolites. Materials and Methods: The arterial input function and conversion rate constantfrom injected substrates (pyruvate) to downstream metabolite (lactate) were precalibrated,based on pre-scans of time-resolved MRS. MRSI was simulated using twositeexchange model with considerations of scan parameters of MRSI. Optimal scantimewindow for mapping lactate was chosen from simulated lactate intensity maps. The performance was validated by multiple in vivo experiments of BALB/C nude micewith MDA-MB-231 breast tumor cells. As a comparison, MRSI were performed withother scan-time windows simply chosen from the lactate signal intensities of prescantime-resolved MRS. Results: The optimal scan timing for our animal models was determined bysimulation, and was found to be 15 s after injection of the pyruvate. Compared to thesimple approach, we observed that the lactate peak signal to noise ratio (PSNR) wasincreased by 230%. Conclusion: Optimal scan timing to measure downstream metabolites usinghyperpolarized 13C MRSI can be determined by the proposed protocol-specificsimulation approaches.
Abstract
Purpose: For a single time-point hyperpolarized 13C magnetic resonance spectroscopyimaging (MRSI) of animal models, scan-time window after injecting substrates iscritical in terms of signal-to-noise ratio (SNR) of downstream metabolites. Prescansof time-resolved magnetic resonance spectroscopy (MRS) can be performed todetermine the scan-time window. In this study, based on two-site exchange model,protocol-specific simulation approaches were developed for 13C MRSI and the optimalscan-time window was determined to maximize the SNR of downstream metabolites. Materials and Methods: The arterial input function and conversion rate constantfrom injected substrates (pyruvate) to downstream metabolite (lactate) were precalibrated,based on pre-scans of time-resolved MRS. MRSI was simulated using twositeexchange model with considerations of scan parameters of MRSI. Optimal scantimewindow for mapping lactate was chosen from simulated lactate intensity maps. The performance was validated by multiple in vivo experiments of BALB/C nude micewith MDA-MB-231 breast tumor cells. As a comparison, MRSI were performed withother scan-time windows simply chosen from the lactate signal intensities of prescantime-resolved MRS. Results: The optimal scan timing for our animal models was determined bysimulation, and was found to be 15 s after injection of the pyruvate. Compared to thesimple approach, we observed that the lactate peak signal to noise ratio (PSNR) wasincreased by 230%. Conclusion: Optimal scan timing to measure downstream metabolites usinghyperpolarized 13C MRSI can be determined by the proposed protocol-specificsimulation approaches.
참고문헌 (10)
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