Open-Access, Low Magnetic Field MRI for Humans

We are developing a novel biomedical imaging technology: magnetic resonance imaging (MRI) of hyperpolarized noble gas (³He) inhaled into human lungs at low magnetic fields (< 0.01 tesla). This technology will allow MRI studies of human ventilation in a simple, low-cost system with an open geometry (i.e., with the person standing, sitting, or lying down) and without the problems of high magnetic fields for people with implants, pacemakers, etc.

We are applying this open-access MRI to studies of pulmonary physiology, e.g., mapping ventilation and pulmonary oxygen concentration as a function of body orientation in the gravitational field. In the future, this technology may enable small, portable, low-field MRI systems with important uses such as imaging the underdeveloped lungs of premature infants, who often suffer from pulmonary problems and cannot be moved from the neonatal intensive care unit to a conventional MRI scanner.

Low-field MRI is made practical by the process of noble gas "hyperpolarization". In this laser optical pumping process, the NMR signal of noble gases such as ³He and ¹²⁹Xe can be increased by four to five orders of magnitude by increasing the atoms' nuclear spin polarization. In addition to MRI of human lungs, there are many important applications of hyperpolarized noble gas NMR in the physical sciences - some of which are pursued by our group and described on other pages.

A novel feature of hyperpolarized noble gas is that it enables high-sensitivity MRI at low magnetic fields, because the polarization is induced optically, prior to the MRI procedure, rather than by thermal equilibrium in the presence of a large magnetic field. The large magnetic fields of conventional human MRI instruments typically require a large, heavy, and expensive superconducting magnet which often restricts the imaging subject to lie flat inside a tight tube. At low magnetic fields, however, it is possible to image hyperpolarized noble gas using a simple, open electromagnet and achieve similar resolution (1 mm) to that obtained at high fields, as our group first demonstrated for small samples in a home-built MRI system operating at 0.002 tesla.

A description of our work in this area is also provided by the Harvard-MIT HST program, here

Recent Posters (click to download)

(Caution: 6 MB file!)

References:

Towards Posture-Dependent Human Pulmonary Oxygen Mapping using Hyperpolarized Helium and
an Open-Access MRI System
An Open-Access, Very-Low-Field MRI System for Posture-Dependent ³He Human Lung Imaging.

Posture-Dependent Human ³He Lung Imaging in an Open Access MRI System: Initial Results.

Development of a Low-Field ³He MRI System to Study Posture-Dependence of Pulmonary Function

A System for Open-Access ³He Human Lung Imaging at Very Low Field.

³He Lung Imaging in an Open Access, Very-Low-Field Human MRI System.

Novel MRI Applications of Laser-Polarized Noble Gases. (Large File - 6.8 MB!)

Biomedical Applications of Low Field MRI in Microgravity
A system for low field imaging of laser-polarized noble gas.

Low field MRI of laser polarized noble gas.

Nuclear Magnetic Resonance Experiments using Laser-Polarized Noble Gas