A vendor-neutral EPI sequence for hyperpolarized 13 C MRI.

Purpose: To develop a flexible, vendor-neutral EPI sequence for hyperpolarized ¹³ C metabolic imaging.
Methods: An open-source EPI sequence consisting of a metabolite-specific spectral-spatial RF excitation pulse and a customizable EPI readout was created using the Pulseq framework. To explore the flexibility of our sequence, we tested several versions of the sequence including a symmetric 3D readout with different spatial resolutions for each metabolite (1.0 cm ³ and 1.5 cm ³ ). A multichamber phantom constructed with a Shepp-Logan geometry, containing two chambers filled with either natural abundance ¹³ C compounds or hyperpolarized (HP) [1- ¹³ C]pyruvate, was used to test each sequence. For experiments involving HP [1- ¹³ C]pyruvate, a single chamber was prefilled with nicotinamide adenine dinucleotide hydride and lactate dehydrogenase to facilitate the conversion of [1- ¹³ C]pyruvate to [1- ¹³ C]lactate. All experiments were performed on a Siemens Prisma 3T scanner.
Results: All the sequence variations localized natural-abundance ¹³ C ethylene glycol and methanol to the appropriate compartment of the multichamber phantom. [1- ¹³ C]pyruvate was detectable in both chambers following the injection of HP [1- ¹³ C]pyruvate, whereas [1- ¹³ C]lactate was only found in the chamber containing nicotinamide adenine dinucleotide hydride and lactate dehydrogenase. The conversion rate from [1- ¹³ C]pyruvate to [1- ¹³ C]lactate (k _PL ) was 0.01 s ^-1 (95% confidence interval [0.00, 0.02]).
Conclusion: We have developed and tested a vendor-neutral EPI sequence for imaging HP ¹³ C agents. We have made all of our sequence creation and image reconstruction code freely available online for other investigators to use.
(© 2024 International Society for Magnetic Resonance in Medicine.)