New 3D imaging technology promises better heart, blood-flow diagnosis
Researchers at Philips Research Europe (Hamburg, Germany) have performed a preclinical study using a prototype system based on a new technology called magnetic particle imaging (MPI) to capture high-resolution, three-dimensional images of arterial blood flow and volumetric heart motion in real time from a live laboratory rat. They believe their work represents a major step forward in taking MPI from a theoretical concept to an imaging tool that would help improve diagnosis and therapy planning for many of the world’s major diseases, such as atherosclerosis and congenital heart defects.
Using iron-oxide nanoparticles injected into a live subject, MPI measures the nanoparticle concentration in the blood. The nanoparticles appear as bright signals in the images, from which nanoparticle concentrations can be calculated.
This schematic shows both MPI system setup and its operating principles.
To detect and measure the particles, the MPI system uses sets of static magnetic ﬁeld (‘selection ﬁeld’) coils, oscillating ﬁeld (‘drive ﬁeld’) coils and signal receive coils. The selection ﬁeld provides a single ﬁeld-free point (FFP) in space, while it is non-zero at all other spatial positions (see diagram.) In the close vicinity of the FFP, the magnetic orientation of the nanoparticles aligns easily with an applied oscillating drive ﬁeld, while at all other positions, the magnetization is forced to align with the local selection-ﬁeld direction.
Since the particles have a nonlinear magnetization curve, the magnetization reorientation occurring around the FFP induces a signal in the receive coils (at the drive-ﬁeld frequency) that is proportional to the particle concentration at that point. Moving the FFP over the subject in a dense trajectory generates a full image that can be related to CT or MRI images.
By combining a high spatial resolution of less than 2 mm with image acquisition times as short as 21.5 ms, MPI can capture dynamic changes in concentration as the nanoparticles are swept along by the blood stream. Ultimately, MPI scanners could, in a single scan, perform a range of functional cardiovascular tests such as measurements of coronary blood supply, myocardial perfusion, and the heart’s ejection fraction, wall motion, and flow speeds. For further information, call Steve Klink at 011-31-40-27-43703 or e-mail him at email@example.com.
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