measuring-spin-lattice-relaxation-magnetic-field-dependence

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-<sup>13</sup>C]pyruvate

The fundamental limit to in vivo imaging applications of hyperpolarized 13C-enriched compounds is their finite spin-lattice relaxation times. Various ...

Western University

Delta relaxation enhanced magnetic resonance (dreMR) imaging requires an auxiliary B0 electromagnet capable of shifting the main magnetic field within a clinical 1.5 Tesla (T) MR system. In this work, the main causes of interaction between an actively shielded, insertable resistive B0 electromagnet and a 1.5T superconducting system are systematically identified and mitigated.

Development and optimization of hardware for delta relaxation enhanced MRI.

To construct a switch-tuned (13) C - (1) H birdcage radiofrequency (RF) coil system capable of metabolic imaging of hyperpolarized (13) C-enriched metabolic probes for co-registration with MRI morphology using protons.

Construction and evaluation of a switch-tuned (13) C - (1) H birdcage radiofrequency coil for imaging the metabolism of hyperpolarized (13) C-enriched compounds.

Radiation Pneumonitis (RP) limits radiotherapy. Detection of early metabolic changes in the lungs associated with RP may provide an opportunity to adjust treatment before substantial toxicities occur. In this work, regional lactate-to-pyruvate signal ratio (lac/pyr) was quantified in rat lungs and heart following administration of hyperpolarized (13)C-pyruvate magnetic resonance imaging (MRI) at day 5, 10, 15 and 25-post conformal radiotherapy. These results were also compared to histology and blood analyses.

Mapping metabolic changes associated with early Radiation Induced Lung Injury post conformal radiotherapy using hyperpolarized ¹³C-pyruvate Magnetic Resonance Spectroscopic Imaging.

In vivo pH mapping in tissue using hyperpolarized hydrogencarbonate- C has been proposed as a method to study tumor growth and treatment and other pathological conditions related to pH changes. The finite spin-lattice relaxation times (T ) of hyperpolarized media are a significant limiting factor for in vivo imaging. Relaxation times can be measured at standard magnetic fields (1.5 T, 3.0 T etc.), but no such data are available at low fields, where T values can be significantly shorter. This information is required to determine the potential loss of polarization as the agent is dispensed and transported from the polarizer to the MRI scanner. The purpose of this study is to measure T dispersion from low to clinical magnetic fields (0.4 mT to 3.0 T) of different hyperpolarized hydrogencarbonate formulations previously proposed in the literature for in vivo pH measurements.  C-enriched cesium and sodium hydrogencarbonate preparations were hyperpolarized using dynamic nuclear polarization, and the T values of different samples were measured at different magnetic field strengths using a fast field-cycling relaxometer and a 3.0 T clinical MRI system. The effects of deuterium oxide as a dissolution medium for sodium hydrogencarbonate were also analyzed. This study finds that the cesium formulation has slightly shorter T values compared with the sodium preparation. However, the higher solubility of cesium hydrogencarbonate- C means it can be polarized at greater concentration, using less trityl radical than sodium hydrogencarbonate- C. This study also establishes that the preparation and handling of sodium hydrogencarbonate formulations in relation to cesium hydrogencarbonate is more difficult, due to the higher viscosity and lower achievable concentrations, and that deuterium oxide significantly increases the T of sodium hydrogencarbonate solutions. Finally, this work also investigates the influence of pH on the spin-lattice relaxation of cesium hydrogencarbonate- C measured over a pH range of 7 to 9 at 0.47 T.

Francisco Martinez-Santiesteban

Imaging Research Laboratory,
Robarts Research Institute,
Imaging Research Laboratory, Robarts Research Institute

Western University

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-¹³C]pyruvate

Francisco Martinez-Santiesteban

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Western University

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate

Imaging Research Laboratory,
Robarts Research Institute,
Imaging Research Laboratory, Robarts Research Institute

Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-¹³C]pyruvate