Philips announces first 3D cardiovascular images from magnetic particle imaging

27 February 2009

Royal Philips Electronics (NYSE: PHG, AEX: PHI) has announced the first 3D imaging results obtained with a new imaging technology called magnetic particle imaging (MPI).

The technology, which uses the magnetic properties of iron-oxide nanoparticles injected into the bloodstream, has been used in a pre-clinical study to generate unprecedented real-time tomographic images of arterial blood flow and volumetric heart motion.

In the study, conducted by Philips Research Europe in Hamburg, researchers injected mice with a commercially available MRI contrast agent to produce the first in vivo 3D real-time scans of a beating mouse heart. The images had a temporal resolution of 21.5 ms and a 3D field of view of 20.4 x 12 x 16.8 mm.

This represents a major step forward in taking magnetic particle imaging from a theoretical 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 pre-clinical study were published in the  journal Physics in Medicine and Biology [1].

“A novel non-invasive 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,” says Professor Valentin Fuster, MD, PhD, director of the Mount Sinai Heart Center, New York.

“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,” says 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 and MR, 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 uses 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), magnetic particle imaging 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 mark 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. Signal measurement and processing are areas where Philips has a great deal of proven expertise and experience that it is currently applying to the task.

1. J Weizenecker et al. Three-dimensional real-time in vivo magnetic particle imaging. Phys. Med. Biol. 2009 54 L1-L10 doi: 10.1088/0031-9155/54/5/L01.  

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