A reproducible dynamic phantom for sequence testing in hyperpolarised 13C-magnetic resonance

Abstract

Objectives: To develop a phantom system which can be integrated with an automated injection system, eliminating the experimental variability that arises with manual injection; for the purposes of pulse sequence testing and metric derivation in hyperpolarised 13C-MR. Methods: The custom dynamic phantom was machined from Ultem and filled with an NADH and LDH mixture dissolved in phosphate buffered saline. Hyperpolarised [1-13C]-pyruvate was then injected into the phantom (n = 8) via an automated syringe pump and the conversion of pyruvate to lactate monitored through a 13C imaging sequence. Results: The phantom showed low coefficient of variation for the lactate to pyruvate peak signal heights (11.6%) and dynamic area-under curve ratios (11.0%). The variance for the LDH enzyme rate constant (kP) was also seen to be low at 15.6%. Conclusion: The dynamic phantom demonstrates high reproducibility for quantification of 13C-hyperpolarised MR derived metrics. Establishing such a phantom is needed to facilitate development of hyperpolarsed 13C-MR pulse sequenced; and moreover, to enable multi site hyperpolarised 13C-MR clinical trials where assessment of metric variability across sites is critical. Advances in knowledge: The dynamic phantom developed during the course of this study will be a useful tool in testing new pulse sequences and standardisation in future hyperpolarised work.

Quantification of Prostate Cancer Metabolism Using 3D Multiecho bSSFP and Hyperpolarized [1‐13C] Pyruvate: Metabolism Differs Between Tumors of the Same Gleason Grade

“…For kinetic analysis of the metabolite signals, lactate‐to‐pyruvate area under the temporal curve (AUC) ratios were calculated 28 , 29 ; as well as a one‐directional kinetic model to derive the forward rate constant ( k P ) for the enzymatic conversion of pyruvate to lactate. Further information on the analysis methods is provided in the Supplementary Material ( SI6 ).…”

Current methods for hyperpolarized [1‐13C]pyruvate MRI human studies

“…Dynamic phantoms that aim to mimic metabolite kinetics have also been developed, 79–81 and have the potential to more closely mimic the HP experiment, but so far these are not widely used.…”

“…Typically, it is easier to increase the conductivity and hence, coil loading of the non-conductive phantom by adding NaCl to match physiological loading. 16,78 Dynamic phantoms that aim to mimic metabolite kinetics have also been developed, [79][80][81] and have the potential to more closely mimic the HP experiment, but so far these are not widely used.…”