John Stefan Petersson

General Electric | GE

The conversion of hyperpolarized (13) C pyruvate to metabolic products in the Krebs cycle provides valuable information about the metabolic status and the viability of the myocardium. Therefore, imaging methods must be able to spectrally discriminate different (13) C metabolites. However, the requirement for spectral selectivity conflicts with the...

Hyperpolarization is a technique to enhance the nuclear polarization and thereby increase the available signal in magnetic resonance (MR). This chapter provides an introduction to the concept of hyperpolarization as well as an overview of dynamic nuclear polarization (DNP) and para-hydrogen induced polarization (PHIP), two methods used to generate...

This chapter provides an overview of pulse sequences adapted to hyperpolarized MR imaging. Applications of hyperpolarized agents in aqueous solution are reviewed. Vascular (e.g., angiography, perfusion, and catheter tracking) as well as metabolic (e.g., oncology, cardiology, neurology, and pH mapping) applications are covered. Due to the rapid deve...

To investigate the feasibility of multiecho balanced steady-state free precession (bSSFP)-based fast chemical shift mapping hyperpolarized (13)C metabolites. The overall goal was to reduce total imaging time and to increase spatial resolution compared to common chemical shift imaging (CSI). A multiecho bSSFP sequence in combination with an iterativ...

Pyruvate is included in the energy production of the heart muscle and is metabolized into lactate, alanine, and CO(2) in equilibrium with HCO(3) (-). The aim of this study was to evaluate the feasibility of using (13)C hyperpolarization enhanced MRI to monitor pyruvate metabolism in the heart during an ischemic episode. The left circumflex artery o...

Interventional procedures in MRI can be performed preclinically using active or passive catheter-tracking methods. A novel passive nonproton technique is suggested that uses a catheter filled with a hyperpolarized (13)C contrast agent. A prototype three-lumen catheter was built with two closed lumens containing a flowing hyperpolarized (13)C contra...

The study of lung perfusion in normal and diseased subjects is of great interest to physiologists and physicians. In this work we demonstrate the application of a liquid-phase hyperpolarized (HP) carbon-13 ((13)C) tracer to magnetic resonance imaging (MRI) of the pulmonary vasculature and pulmonary perfusion in a porcine model. Our results show tha...

A method is proposed that provides spectroscopic images with high spatial resolution and moderate spectral resolution at very short total data acquisition times. Balanced steady-state free precession (bSSFP, TrueFISP, FIESTA, b-FFE) is combined with a multiecho readout gradient and frequency-sensitive reconstruction such as Fourier reconstruction k...

A new diagnostic application of a water-soluble contrast medium (CM) based on the hyperpolarization of a 13C substance is introduced. The degree of polarization achieved is >30%, which is about a factor of 10(5) higher than the thermal equilibrium polarization level at 1.5 T. Imaging of hyperpolarized (HP) CM during a cardiac interventional MRI pro...

The evolution of magnetic resonance imaging (MRI) has been astounding since the early 1980s, and a broad range of applications has emerged. To date, clinical imaging of nuclei other than protons has been precluded for reasons of sensitivity. However, with the recent development of hyperpolarization techniques, the signal from a given number of nucl...

A new technique for assessing tissue blood flow using hyperpolarized tracers, based on the fact that the magnetization of a hyperpolarized substance can be destroyed permanently, is described. Assessments of blood flow with this technique are inherently insensitive to arterial delay and dispersion, and allow for quantification of the transit time a...

Cerebral perfusion was assessed with 13C MRI in a rat model after intravenous injections of the 13C-labeled compound bis-1,1-(hydroxymethyl)-1-13C-cyclopropane-D8 in aqueous solutions hyperpolarized by dynamic nuclear polarization (DNP). Since the tracer acted as a direct signal source, several of the problems associated with techniques based on tr...

Dynamic nuclear polarization has enabled hyperpolarization of nuclei such as 13C and 15N in endogenous substances. The resulting high nuclear polarization makes it possible to perform subsecond 13C MRI. By using the dynamic nuclear polarization hyperpolarization technique, 10% polarization was obtained in an aqueous solution of 100 mM 13C-labeled u...

A (13)C-enriched water-soluble compound (bis-1,1-(hydroxymethyl)-1-(13)C-cyclopropane-D(8)), with a (13)C-concentration of approximately 200 mM, was hyperpolarized to approximately 15% using dynamic nuclear polarization, and then used as a contrast medium (CM) for contrast-enhanced magnetic resonance angiography (CE-MRA). The long relaxation times...

MRI provides unsurpassed soft tissue contrast, but the inherent low sensitivity of this modality has limited the clinical use to imaging of water protons. With hyperpolarization techniques, the signal from a given number of nuclear spins can be raised more than 100 000 times. The strong signal enhancement enables imaging of nuclei other than proton...

A (13)C-enriched water-soluble compound (bis-1,1-(hydroxymethyl)-1-(13)C-cyclopropane-D(8)), with a (13)C-concentration of approximately 200 mM, was hyperpolarized to approximately 15% using dynamic nuclear polarization, and then used as a contrast medium (CM) for contrast-enhanced magnetic resonance angiography (CE-MRA). The long relaxation times...

The influence of flip angle and flow velocity on the signal intensity achieved when imaging a hyperpolarized substance with a spoiled gradient echo sequence was investigated. The study was performed both theoretically and experimentally using hyperpolarized xenon dissolved in ethanol. Analytical expressions regarding the optimal flip angle with res...

The feasibility of hyperpolarized 129Xe for fast MR angiography (MRA) was evaluated using the echo-planar imaging (EPI) technique. Hyperpolarized Xe gas was dissolved in ethanol, a carrier agent with high solubility for Xe (Ostwald solubility coefficient 2.5) and long relaxation times. The dissolved Xe was injected as a bolus into a flow phantom wh...

A new strategy for a quantitative measurement of regional pulmonary ventilation using hyperpolarized helium-3 (3He) MRI has been developed. The method employs the build-up of the signal intensity after a variable number of (3)He breaths. A mathematical model of the signal dynamics is presented, from which the local ventilation, defined as the fract...

Purpose: The feasibility of hyperpolarized ¹²⁹ Xe for fast MR angiography (MRA) was evaluated using the echo-planar imaging (EPI) technique. Material and Methods: Hyperpolarized Xe gas was dissolved in ethanol, a carrier agent with high solubility for Xe (Ostwald solubility coefficient 2.5) and long relaxation times. The dissolved Xe was injected a...

High nuclear spin polarization of (13)C was reached in organic molecules. Enhancements of up to 10(4), compared to thermal polarization at 1.5 T, were achieved using the parahydrogen-induced polarization technique in combination with a field cycling method. While parahydrogen has no net polarization, it has a high spin order, which is retained when...

A noninvasive method for in vivo measurement of the oxygen concentration has been developed. By introducing a novel contrast medium (CM) based on a single electron substance, it is possible to enhance the proton signal through the Overhauser effect. A low-field magnetic resonance scanner is used to image the proton nuclei of the object. The electro...

The purpose of this work was to study image effects due to time-varying contrast medium concentration in contrast-enhanced three dimensional (3D) magnetic resonance angiography (MRA) images. Two different simulation models (1D and 3D) and two different contrast medium variation schemes were used. Phantom measurements were also performed. Experiment...

The multidimensional partition model, which combines the k-space description of magnetic resonance imaging pulse sequences with a partition concept, has been developed to model flow-related effects. A partition represents the magnetization created due to excitation by a given radiofrequency pulse. In the present model, it is visualized as a set of...

Introduction We have developed a prototype imaging system for Overhauser MRI experiments on phantoms and on small animals (rats and rabbits). So far, two copies of the scanner have been built; one is operated at Philips Research in Hamburg, the other one at Nycomed Innovation in Malmo. The scanners are intended for evaluation of contrast agents for...

Parameters of relevance to oximetry with Overhauser magnetic resonance imaging (OMRI) have been measured for three single electron contrast agents of the triphenylmethyl type. The single electron contrast agents are stable and water soluble. Magnetic resonance properties of the agents have been examined with electron paramagnetic resonance (EPR), n...

To evaluate a new single-electron contrast agent for Overhauser-enhanced MR imaging. The contrast agents that are currently available give enhancement factors that are too low to make the technique a valid option for routine clinical use. MR images were generated directly following the injection of the substance into rats. The MR scanner was operat...

The k-space description, of MRI pulse sequences, has been combined with a partition model in order to model the image reconstruction and the contrast behaviour found in SSFP pulse sequences. A partition represents the magnetisation created, due to excitation by a given rf pulse. In the present model, it is visualised as a set of parameters rather t...

An MRI simulation method, together with a corresponding computer program, using the k-space formalism has been developed. It uses a FFT algorithm to generate the ideal NMR signal from a user defined object. The k-space trajectory given by a pulse sequence is calculated. And it is used to select elements from the ideal NMR signal. This selection of...