Microwaves in Medicine

Microwaves in Medicine:

Meridian Medical Systems Takes On the Status Quo

Meridian Medical Systems (MMS) is the microwave technology company you've likely never heard of. Founded in 1985 by industry luminary Dr. Kenneth Carr, MMS applies the inherent characteristics of electromagnetic energy to solve problems in medical treatment that elude more conventional technologies. The company's products use microwave energy to generate heat, measure radiation and motion, and monitor and maintain the temperature of blood and other fluids. MMS has garnered awards from NASA, the U.S. Army, the Small Business Administration, the National Institutes of Health, and the Massachusetts Technology Collaborative, many of its products have received FDA approval, and a folder of unsolicited letters testifies to their effectiveness. Carr, an Institute of Electrical and Electronics Engineers (IEEE) Life Fellow, is considered a pioneer in the medical application of microwave technology, and has nearly 40 patents in the discipline.

So why haven't you heard about MMS? "It's a big leap from product development to industry acceptance," says Bob Allison, since 1998 the company's vice president and engineering manager, and a veteran of more than 30 years in the microwave industry. "It's also hard to walk in the front door and generate interest in an innovative product using an unknown technology in such a conservative industry. People often equate innovation with risk". Fortunately, the company's latest product seems destined to bring the company into the mainstream of the medical equipment industry.

A Winner In the Works

The product is an aid for treatment of cardiac arrhythmia (when the heart beats too slowly, too fast, or irregularly), may change that forever. The procedure for treating the disorder (called cardiac ablation) selectively destroys tissue to ensure that the "signal" controlling the heartbeat follows the proper path.

A catheter is inserted into the patient's leg that runs upward and into the heart, where, through cryogenic cooling or electromagnetic or ultrasonic radiation, the target tissue is destroyed " with the decision criteria for how much tissue to destroy being based largely upon the doctor's level of experience with the procedure. The temperature sensor in conventional catheters can measure only the value in the tip, which is typically cooled, so the value returned is not very precise. Without an accurate feedback mechanism, doctors tend to apply less-than-optimum energy levels to ensure patient safety (i.e., minimize risk), which reduces the procedure's effectiveness.

The catheter/antenna developed by MMS provides precise, real-time feedback to the doctor about how much energy to apply while he or she is performing the procedure. It combines the ability to deliver microwave radiation to heat tissue with a radiometer (essentially a remote sensing device) fabricated as a microwave monolithic integrated circuit (MMIC) to sense the temperature of the heart wall. The Dicke radiometer employed in the design obtains tissue temperature measurements noninvasively and operates by comparing an internal reference temperature with an actual radiometric measurement and using the difference to calculate body temperature.
Early results show the technique to be extremely accurate. Although radiometers have been used for years in applications ranging from measuring atmospheric and terrestrial radiation from space to oceanographic remote-sensing, the radiometer designed by MMS incorporates several proprietary technologies that optimize its use for cardiac ablation.
The MMS MMIC was designed using AWR® Microwave Office®electronic design automation (EDA) software along with a process design kit (PDK) developed by AWR for TriQuint Semiconductor that accurately represents TriQuint's foundry process. Allison has used AWR tools since their earliest development, but his experience with EDA tools, as well as with virtually every other high-frequency design solution, dates back to the days of mainframe time-sharing.
"Microwave Office is unique among these tools for its ability to make the design process comparatively simple," says Allison. "It's created by engineers who understand the difference between designing a microwave circuit and digital one " and it shows in the software." Allison designed the circuit, selected the features from the PDK library, performed design rule checking, and sent the result to TriQuint, all in a very short time. Measurements on the devices received from TriQuint agree extremely well with the Microwave Office simulation.
The company's next step is to conduct additional field studies and product procedure tests and ultimately to offer it as an alternative solution to the techniques universally used by doctors to treat cardiac arrhythmia. "There is incredible potential for use of the device," says Allison. "It eliminates the inherent problems of current products, and doctors have already expressed considerable interest because it can make the procedure easier for the doctor and safer and more effective for the patient."
So Much for the "Better Mousetrap" Theory
The MMS fluid warmer provides a great example of the problems the company has encountered throughout its history. Hospitals typically use warm water baths to heat fluids, including blood, which poses a risk of infection from the water, which can harbor bacteria. The risk of infection is compounded because very fragile, thin-walled tubing is used to heat the fluid within the tubing. In contrast, the ThermoStat 900 is a dry system that uses a disposable cartridge with a short length of standard IV tubing so there is no risk of infection. It uses microwave power with radiometric sensing to safely measure, control temperature, accurately measure fluid flow-rate, and detect air emboli. It is competitive in cost with conventional solutions, and has technical features they don't provide. It offers other advantages as well.
"It's vastly superior to the current technique and we have letters from medical people that frankly, rave about the product and claims it has actually saved lives," says Allison. "One major U.S. hospital evaluated every candidate product and rated this one the best. You can turn it on instantly and deliver transfusions almost instantaneously with body-temperature blood." With such an enthusiastic response, you'd expect the ThermoStat 900 to be a staple in hospitals everywhere " but it's not. "When entrenched competitors found out about it, they simply gave them all the blood warmers they needed. And that was that." At least for now, since MMS continues to receive interest in the product from other places.
And then there's the MMS PDM-3 sterile docking system, which sterilizes tubing connections before infusing fluids into the body during Continuous Ambulatory Peritoneal Dialysis (CAPD) for people with kidney failure. In this process a short connection of IV tubing is surgically embedded into the peritoneum (the cavity that surrounds the abdominal organs). The patient infuses dialysis solution stored in bags into the peritoneum via the IV tubing. While the dialysis solution is held in the peritoneum, impurities in the blood are absorbed through the membrane surrounding the peritoneum and into the dialysis solution, which the patient then drains from the cavity.
This process occurs several times a day, each of which requires connection to a new container of solution. A disposable wipe is typically used to sterilize the connection. However, the possibility of infection is always present when the connection process is performed. If infection occurs it can result in peritonitis, an even more threatening imflammatory complication that can even result in death. The PDM-3 uses microwave energy to steam-sterilize the connection between the solution bag and the surgical implant, eliminating risk of infection at the connection point and destroying all microorganisms recognized to cause Peritonitis in 30 seconds. The PDM-3 also stores information regarding the patient's use of the unit that can be used to determine patient compliance with the connector sterilization procedure.

We spent an enormous amount to time to demonstrate that it works," says Allison. "It kills all bacteria, and is much, much more effective than the usual disposable wipes that are commonly used to sterilize the connections". The company ultimately received FDA approval and signed with a company to exclusively distribute it. After a long wait, the distributor had produced no results. "We wondered why," Allison continues, "and we finally realized they simply weren't going to market it. After a few frank discussions they said since the PDM-3 is a $2,000 product that replaces a $1 disposable wipe, actively selling it would cannibalize their existing wipe business, which was substantial. We had this silly notion that if we created something better, something that helps people, that can even save people's lives, it would be enthusiastically received. In truth, it's really all about making money."
Business Heating Up
The irony in the history of MMS is that the solutions the company has developed are almost invariably more effective than those they would replace. Doctors have given their enthusiastic approval to MMS products, and some are used at major U.S. hospitals. However, the medical equipment business is intensively competitive, and vendors fight just as hard to remain in place as they did to get the customer in the first place. That often means they must give products away or provide other perks to retain the account, which for a small company like MMS is a cast iron barrier to entry. Nevertheless, the breadth of the company's products, its technical reputation, and sheer tenacity are starting to produce the results MMS has sought for so long. "We're hopeful," said Allison, "very hopeful."
http://www.rfid-world.com/news/212901804?pgno=2
Christian Argenis umaña Zambrano
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