Date: Dec 02, 2013 Source: University of Wisconson-Madison School of Medicine and Public Health Press Relea (
click here to go to the source)
One of the greatest restraints in advancing technology into practical use is money. The mighty dollar can frustrate a researcher trying to schedule time on scarce instruments; unfavorable results from a feasibility study can confound potential clinical relevance; costs can make the most efficacious technology impractical.
But because of a device that can be as small as a grain of rice, the field of biomagnetism may be primed for a cost-effective renewal.
While Ron Wakai, professor of medical physics in the School of Medicine and Public Health, was publishing the results of the first sizable study tracking magnetic activity in the hunt for long QT syndrome - a dangerous arrhythmia - he's also been working with a company in Colorado, QuSpin, Inc., on a new sensor.
The scalable technology can be small enough to fit on a microchip. The new prototype fits in his hand.
Using massive, multi-channel biomagnetometers more commonly used in brain scans, Wakai's most recent study evaluated 30 pregnancies in search of the dangerous fetal heart rhythm. To gather enough subjects, the study ran between 1996-2012.
The vernix, a protective coating on the skin of the fetus that interferes with electrical measurements such as EKGs, so Wakai needed a different way to measure the fetal heart rhythm. Because electrical activity produces a magnetic field, Wakai used a magnetometer to measure changes in the magnetic field to produce a fetal magnetocardiograph, comparable to a traditional EKG reading. The study identified long QT syndrome with 89 percent accuracy.
"This disease is something that really cannot be diagnosed with an ultrasound," said Wakai. "For the fetus and obstetrics, ultrasound dominates. It's really the only technology that's used. It's simple and inexpensive."
According to Wakai, if the cost of a technology could be reduced by a significant margin, it really would have a big impact. "For fetal MCG, its main competing technology is ultrasound, so it has to be cost effective in comparison to that."
Enter the atomic magnetometer.
"It's the first device that has adequate sensitivity, comparable to the detectors that we call a SQUID (superconducting quantum interference device) detector," said Wakai. "We just published a study showing that we could get heart and brain scans with an atomic magnetometer that are just as good as those from a SQUID."
Magnetometers - found in almost everything from smart phones to archeological survey equipment - measure magnetic fields. The technology varies, but an atomic magnetometer is made of three components: an infrared laser, a cube filled with vaporized atoms, and an infrared photodetector.
When no magnetic field is present, the laser's polarized light, which aligns the vaporized atoms, passes directly through the cube unaffected. But, when a magnetic field is present, the atoms change their alignment and absorb an amount of light proportional to the strength of the magnetic field. The change in light is measured by the photodetector.
The SQUID is a superconducting detector that has to be cooled to 450 degrees below zero Fahrenheit. That requirement also makes the detectors very large because they are contained within a Dewar, a reservoir that holds about 50 liters of liquid helium. A SQUID also must be used in a sophisticated, shielded room made of magnetic alloy to block out other magnetic fields. The shielding room alone costs roughly $500,000.
QuSpin's new prototype is almost the opposite. A single insulated sensor is roughly the size of a screwdriver handle and is heated to almost 200 degrees Celsius to keep the cube of atoms in a vapor phase. Also, a much smaller shield that wraps around the patient is sufficient, comparable to an MRI table. Instead of a patient sliding into the bore of a magnet, they'd slide into a cylindrical magnetic shield.
Wakai believes that atomic magnetometers can also substantially reduce the cost of magnetoencephalography (MEG) scanners for brain studies. A device for brain scans is also underway, but the lion's share of Wakai's attention is being paid to the fetal device.
"The feasibility study has already been done for the prototype," said Wakai. "The prototype we're envisioning probably needs somewhere between seven to 20 mounted sensors so you can position them over the mother's belly, and that's pretty much all there is to it."
Wakai believes the atomic magnetometer will be much cheaper than current technology, and while it might not be cheaper by a factor of ten, he predicts it will be much more than a factor of two. He plans to be testing his new array of atomic magnetometers by early next year.
