A vendor‐neutral EPI sequence for hyperpolarized 13C MRI

Abstract

AbstractPurposeTo develop a flexible, vendor‐neutral EPI sequence for hyperpolarized 13C metabolic imaging.MethodsAn 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 cm3 and 1.5 cm3). A multichamber phantom constructed with a Shepp‐Logan geometry, containing two chambers filled with either natural abundance 13C compounds or hyperpolarized (HP) [1–13C]pyruvate, was used to test each sequence. For experiments involving HP [1–13C]pyruvate, a single chamber was prefilled with nicotinamide adenine dinucleotide hydride and lactate dehydrogenase to facilitate the conversion of [1–13C]pyruvate to [1–13C]lactate. All experiments were performed on a Siemens Prisma 3T scanner.ResultsAll the sequence variations localized natural‐abundance 13C ethylene glycol and methanol to the appropriate compartment of the multichamber phantom. [1–13C]pyruvate was detectable in both chambers following the injection of HP [1–13C]pyruvate, whereas [1–13C]lactate was only found in the chamber containing nicotinamide adenine dinucleotide hydride and lactate dehydrogenase. The conversion rate from [1–13C]pyruvate to [1–13C]lactate (kPL) was 0.01 s−1 (95% confidence interval [0.00, 0.02]).ConclusionWe have developed and tested a vendor‐neutral EPI sequence for imaging HP 13C agents. We have made all of our sequence creation and image reconstruction code freely available online for other investigators to use.