Hyperpolarized carbon-13 MRI

Hyperpolarized carbon-13 MRI is a functional medical imaging technique for probing perfusion and metabolism using injected substrates.

It is enabled by techniques for hyperpolarization of carbon-13-containing molecules using dynamic nuclear polarization and rapid dissolution to create an injectable solution.

For example, metabolic conversion of hyperpolarized pyruvate into lactate is increasingly being used to image cancerous tissues via the Warburg effect.

[6] The compounds are then thawed and dissolved to yield a room temperature solution containing hyperpolarized nuclei which can be injected.

Hyperpolarized samples of 13C pyruvic acid are typically dissolved in some form of aqueous solution containing various detergents and buffering reagents.

Using techniques for simultaneous spatial and spectral selective excitation, RF pulses can be designed to perturb metabolites individually.

This technique also allows different flip angles to be applied to each metabolite,[11][12] which enables pulse sequences to be designed that make optimal use of the limited polarization available for imaging.

[13][14] In contrast with conventional MRI, hyperpolarized experiments are inherently dynamic as images must be acquired as the injected substrate spreads through the body and is metabolized.

Comparing the definite integral under the substrate and product metabolite curves has been proposed as an alternative to model-based parameter estimates as a method of quantifying metabolic activity.

are not met, or there is significant noise in the collected data, it is desirable to compute estimates of model parameters directly.

When noise is independent and identically distributed and Gaussian, parameters can be fit using non-linear least squares estimation.