Pulse sequence for dynamic volumetric imaging of hyperpolarized metabolic products

Abstract

Dynamic nuclear polarization and dissolution of a (13)C-labeled substrate enables the dynamic imaging of cellular metabolism. Spectroscopic information is typically acquired, making the acquisition of dynamic volumetric data a challenge. To enable rapid volumetric imaging, a spectral-spatial excitation pulse was designed to excite a single line of the carbon spectrum. With only a single resonance present in the signal, an echo-planar readout trajectory could be used to resolve spatial information, giving full volume coverage of 32 x 32 x 16 voxels every 3.5s. This high frame rate was used to measure the different lactate dynamics in different tissues in a normal rat model and a mouse model of prostate cancer.

Rapid multislice imaging of hyperpolarized 13C pyruvate and bicarbonate in the heart

“…A spectral-spatial excitation pulse was designed according to (7). The RF pulse used was 13.6-ms long and has an excitation profile with two passbands with FWHM of 200 Hz, separated by a 1-kHz wide stopband with a suppression level of 10 −3 , and secondary bipolar sidelobes with suppression level of 10 −2 located 500 Hz from the primary passbands.…”

“…Recently, hyperpolarized 13 C pyruvate has been used to characterize cardiac metabolism noninvasively in the rat (4,5) and the pig (6). In these studies, [1][2][3][4][5][6][7][8][9][10][11][12][13] C] pyruvate was injected intravenously, and cardiac spectra were acquired with spatial localization to the heart either by coil location or by slice selection and single-step phase encoding of the field of view.…”

“…Previously, a spectral-spatial excitation pulse has been used to selectively image the lactate resonance in the [1-13 C] pyruvate spectrum, with the resulting signal spatially encoded using a 3D multi-shot echo-planar flyback readout trajectory (7). The spectral-spatial profile of the RF pulse is designed to avoid excitation of the remaining resonances in the spectrum.…”

“…This sequence permits whole-heart coverage (6 slices, 8.8 mm in-plane resolution) in any plane, allowing imaging of the metabolites of interest, [1][2][3][4][5][6][7][8][9][10][11][12][13] C] pyruvate, [1-13 C] lactate, and 13 C bicarbonate, within a single breathhold. Pyruvate and bicarbonate cardiac volumes were acquired, while lactate images were not acquired due to low lactate levels in the animal model studied.…”

Metabolic imaging of acute and chronic infarction in the perfused rat heart using hyperpolarised [1‐13C]pyruvate

“…Work with several in vivo animal models has combined DNP with different imaging techniques (18)(19)(20)(21)(22), including chemical shift imaging (CSI) (23), to obtain metabolic maps of the heart using hyperpolarised [1-13 C]pyruvate (2,20,(24)(25)(26)(27). However, these studies have focused on in vivo models, with no work to date reported on the isolated perfused heart.…”