The use of devices incorporating magnets for the targeted delivery of drugs is nothing new.

As just one prominent example,FeRx, which had been based in San Diego, developed what it called Magnetic Targeted Carrier Technology which employed a small, externally positioned magnet, combined with microparticles made of metallic iron and activated carbon. The microparticles were mixed with a drug and the magnet was then positioned to draw the drug to a specific site in the body.

FeRx discontinued operations in 2004 after its major trial failed to reach significance in the treatment of primary liver cancer (Medical Device Daily, May 4, 2004).

Now, researchers reporting at theAnnual Congress of the American College of Surgeons (Chicago) this week have described a new spin on this delivery method – using magnetism, incorporated into an implanted stent, and pairing this with an external magnet.

The study, the researchers said, provides proof of principle that the dual-magnet sources, in tandem, can deliver drugs to a targeted area and do it efficiently.

“We haven’t reinvented the wheel yet, but we are getting very encouraging results,” said Zachary Forbes, PhD, assistant professor of surgery at Drexel University College of Medicine (Philadelphia).

The investigators said they believe the method may be tailored to carry antibiotics used to prevent acute and chronic infections that can occur alongside orthopedic implants and to confine chemotherapeutic agents to malignant tumors.

Their first objective, however, is to adapt the system for use in preventing restenosis of the arteries.

Forbes and his colleagues are hoping to magnetize the same stents that open up blocked blood vessels so drugs that have been treated with magnetic nanoparticles can be delivered directly to areas of infection or inflammation. The researchers either added a thin layer of magnetic material to a standard stent or by incorporated into it a magnetic alloy that will draw and snare drugs armed with magnetic particles to the implants.

The researchers inserted into animals stents that had been composed of an alloy that magnetized the implants without interfering with their mechanical integrity or properties. After magnetic particles were injected and allowed to circulate in the bloodstream, the investigators computed the number of particles captured by the stents and determined the pattern of distribution of the particles in the tissue.

The researchers found that the magnetic forces generated by the stents attracted enough nanoparticles to be therapeutic, and the stents held magnetic nanoparticles in the bloodstream in a characteristic pattern.

“This system of drug delivery could be used for long-term healing by magnetically attracting particles to the stent, thus providing a sort of rechargeable drug delivery over the life of the implant. Instead of having to restent a blood vessel or perform bypass surgery, patients may be treatable simply by magnetically dosing a site with a given drug,” he said.

The researchers contrasted the system to methods using only external magnets, such as in the approach by FeRx.

“Those systems could get particles to the right site, but had difficulty distributing the particles when they got there,” Forbes said. “So the particles ended up in clumps or scattered over a couple of inches instead of staying in one place.”

Developed for humans, the magnetic stent would be inserted at a designated site, via catheter, in the cardiovascular system. The external magnetic field would lead magnetically charged drugs to the stent, and the stent would hold the drugs in place.

Forbes said, “The kinds of doses we are using in our first studies translate very well to the kinds of numbers of particles we would want to have in the human body. So the fact that we have control over our particles means we have a much more efficient way of putting a certain amount of a drug on a designated surface area.”

In another report from the ACS congress:

A 3D MRI software system that allows practicing physicians to visually “swim” through the anatomy and streamline the diagnosis of patients was introduced in the U.S. at the ACS Congress.

The software was developed by Lee Schiel of Early Response Imaging (San Bernadino, California), who has worked for the National Aeronautics and Space Administration and the California Institute of Technology (Pasadena) to design software programs that can explore the structure of rocks on Mars. An amateur paleontologist, Schiel has used similar software and imaging modalities to reveal dinosaur embryos within fossilized eggs.

For the last year, Schiel has been working on 3D imaging systems for mobile MRI units for several hospitals in the Southern California area.

According to Roger De Filippo, MD, assistant professor of urology at Children’s Hospital Los Angeles (CHLA) and Keck School of Medicine , the software, shown in Europe at the meeting of the British Association of Pediatric Surgeons (London) earlier this year, captures all of the 2D slice data normally presented in MRI images. It then compresses them to a single 3D image.

“When you make something 3D, you enter the world of the surgeon because we operate in 3D,” De Filippo said.

More important, the software enables manipulation of the imaging data on laptop computers and the ability of having access to this data securely from virtual storage warehouses so that it can be accessed from anywhere.

“Physicians can slice through the image virtually, rotate the image, and take sagittal or oblique sections-whatever they need to find pathology. So instead of having to look at 100 slices of 2D sagittal data, physicians have one image in 3D form they can dissect themselves and get a better, more precise representation of the pathology they’re dealing with,” De Filippo said.

The study identified pathology in six children with urologic abnormalities ranging from obstructions in the kidney, blockages of the ureter and bladder, and lack of insertion of the ureter into the bladder.

The imaging software depicted the genitourinary tract in every child from top to bottom. “It gave me a basic gestalt or a way of seeing the whole anatomy in one image,” De Filippo said. The 3D images produced by the software provided clearer views of the anatomy in the pelvis and surrounding the bladder than conventional 2D MRI images.

The software has the potential to reduce or eliminate the need to sedate children while they were being imaged. Standard MRI can take between 45 minutes to an hour. The software gets 3D images in just a few minutes.