Magnetic Particle Image Technology Provides Real-Time Images of Blood Flow and the Heart

New technology called magnetic particle imaging (MPI) has been shown to generate unprecedented real-time images of blood flow and heart movement, which may improve disease diagnosis and treatment planning.

Philips Healthcare (Best, The Netherlands) reported the first three-dimensional (3D) imaging results obtained with MPI. The technology, which uses the magnetic properties of iron-oxide nanoparticles injected into the bloodstream, has been used in a preclinical study to generate extraordinary real-time images of arterial blood flow and volumetric heart motion. This represents a major step forward in taking MPI from a hypothetical concept to an imaging tool to help improve diagnosis and therapy planning for many of the world's major diseases, such as heart disease, stroke, and cancer. The results of the preclinical study were published in March 7, 2009, issue of the journal Physics in Medicine and Biology.

"A novel noninvasive cardiac imaging technology is required to further unravel and characterize the disease processes associated with atherosclerosis, in particular those associated with vulnerable plaque formation, which is a major risk factor for stroke and heart attacks,” said Prof. Valentin Fuster, M.D., Ph.D., director of the Mount Sinai Heart Center (New York, NY, USA). "Through its combined speed, resolution, and sensitivity, magnetic particle imaging technology has great potential for this application, and the latest in vivo imaging results represent a major breakthrough.”

"We are the first in the world to demonstrate that magnetic particle imaging can be used to produce real-time in vivo images that accurately capture cardiovascular activity,” stated Henk van Houten, senior vice president of Philips Research and head of the Healthcare research program. "By adding important functional information to the anatomical data obtained from existing modalities such as CT [computed tomography] and MR [magnetic resonance], Philips' MPI technology has the potential to significantly help in the diagnosis and treatment planning of major diseases such as atherosclerosis and congenital heart defects.”

Philips' magnetic particle imaging utilizes the magnetic properties of injected iron-oxide nanoparticles to measure the nanoparticle concentration in the blood. Because the human body contains no naturally occurring magnetic materials visible to MPI, there is no background signal. After injection, the nanoparticles therefore appear as bright signals in the images, from which nanoparticle concentrations can be calculated. By combining high spatial resolution with short image acquisition times (as short as 1/50th of a second), MPI can capture dynamic concentration changes as the nanoparticles are swept along by the blood stream. This could ultimately allow MPI scanners to perform a wide range of functional cardiovascular measurements in a single scan. These could include measurements of coronary blood supply, myocardial perfusion, and the heart's ejection fraction, wall motion, and flow speeds.

The results obtained from Philips' experimental MPI scanner marks an important step towards the development of a whole-body system for use on humans. Some of the technical challenges in scaling up the system relate to the magnetic field generation required for human applications. Others lie in the measurement and processing of the extremely weak signal emitted by the nanoparticles.

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