Creating a clinical platform for carbon‐13 studies using the sodium‐23 and proton resonances

Abstract

Purpose Calibration of hyperpolarized 13C‐MRI is limited by the low signal from endogenous carbon‐containing molecules and consequently requires 13C‐enriched external phantoms. This study investigated the feasibility of using either 23Na‐MRI or 1H‐MRI to calibrate the 13C excitation. Methods Commercial 13C‐coils were used to estimate the transmit gain and center frequency for 13C and 23Na resonances. Simulations of the transmit B1 profile of a Helmholtz loop were performed. Noise correlation was measured for both nuclei. A retrospective analysis of human data assessing the use of the 1H resonance to predict [1‐13C]pyruvate center frequency was also performed. In vivo experiments were undertaken in the lower limbs of 6 pigs following injection of hyperpolarized 13C‐pyruvate. Results The difference in center frequencies and transmit gain between tissue 23Na and [1‐13C]pyruvate was reproducible, with a mean scale factor of 1.05179 ± 0.00001 and 10.4 ± 0.2 dB, respectively. Utilizing the 1H water peak, it was possible to retrospectively predict the 13C‐pyruvate center frequency with a standard deviation of only 11 Hz sufficient for spectral–spatial excitation‐based studies. Conclusion We demonstrate the feasibility of using the 23Na and 1H resonances to calibrate the 13C transmit B1 using commercially available 13C‐coils. The method provides a simple approach for in vivo calibration and could improve clinical workflow.

Non-Invasive Differentiation of M1 and M2 Activation in Macrophages Using Hyperpolarized 13C MRS of Pyruvate and DHA at 1.47 Tesla

“…The power of dynamic metabolic probing using HP 13 C MR is compelling, as it allows the measuring of previously inaccessible metabolic reactions noninvasively. HP 13 C metabolic imaging is a rapidly growing field, and is now being used in multiple clinical trials across the globe, targeting several organs, including the brain, heart, prostate, and kidney [ 28 , 29 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 ]. It is very likely that, given the constant improvements reported, both on the acquisition and processing sides, this methodology will soon approach feasibility for widespread clinical adoption.…”

Hyperpolarized 129Xe MRI Abnormalities in Dyspneic Patients 3 Months after COVID-19 Pneumonia: Preliminary Results

“…A single exponential fit to the integrated gas spectrum was used to calibrate transmit power (assuming 129 Xe T 1 of 23s) and centre frequency. A further sodium calibration was performed to estimate gas and dissolved phase centre frequency per participant using pulse acquire non-localised spectroscopic acquisition (hard pulse, pulse width = 500ms, TR = 100ms, flip angle = 20 degrees, number of averages (NEX) = 16) ( 13 ).…”

Non-invasive Differentiation of M1 and M2 Activation in Macrophages using Hyperpolarized13C MRS of Pyruvate and DHA at 1.47 Tesla

“…The power of dynamic metabolic probing using HP 13 C MR is compelling, as it allows measuring previously inaccessible metabolic reactions non-invasively. HP 13 C metabolic imaging is a rapidly growing field, and is now being used in multiple clinical trials across the globe, targeting several organs including brain, heart, prostate and kidney [46][47][48][49][50][51][52][53][54][55][56][57] . It is very likely that, given the constant improvements reported both on the acquisition and processing sides, this methodology will soon approach feasibility for widespread clinical adoption.…”