Drugs, surgery, and other devices are effective to various degrees in controlling and treating this condition, benign prostatic hyperplasia (BPH), but the method developed by Sandia's Dr. Lawrence Larsen should have several advantages over existing ones -- it could be done on an outpatient basis and a single treatment should have long-lasting benefits, perhaps for the life of the BPH patient.

Also, side effects should be almost nil from the minimally invasive technique, and treatment costs could be lowered, Larsen says.

His new endoscopic method uses an improved radio frequency (RF) "leaky-wave" applicator to deliver a uniform heating pattern along the length of the gland. The process shrinks the prostate by killing excess cells that typically grow as men age.

The uniform heating pattern is a major improvement over some existing treatment devices. A US patent (6,051,018) was issued for this technology April 18.

Older men typically suffer prostate problems ranging from mild urinary obstruction to cancerous prostates that can even cause death. Larsen's technology is designed to treat benign prostate enlargements that cause urinary obstruction and pain, not cancerous problems. BPH does not necessarily lead to prostate cancer, he says, but is loosely coupled.

This work is a product of Sandia's Laboratory Directed Research and Development program as a dual-use application of radar technology and conformal antennas. It is related to the lab's projects in applied electromagnetics that affect diverse technologies, including communications, microwave power electronics, proximity fuzes, and directed energy.

BPH by itself is a significant problem. Fifty percent of males develop BPH by age 65 and fully 90 percent by age 80. The major symptom is difficulty urinating and associated pain. A normal prostate in a young man is walnut-sized, about 25 to 30 cubic centimeters, and urinary problems usually begin when the gland becomes 25 percent or more larger. An enlarged prostate puts excess pressure on the urethra, making urination more difficult and sometimes painful.

Symptomatic prostate enlargement can be triggered by urinary tract infections but it is often associated simply with aging, Larsen says.

Benign prostatic hyperplasia occurs when cells proliferate in the gland, causing enlargement. The gland can continue to enlarge later on even when cell proliferation decreases, because cells do not die "on cue," he says.

If treatment isn't done early enough or have lasting benefits, surgery has traditionally been the only workable remedy, Larsen says. Unfortunately, surgery is expensive and can have serious side effects, including incontinence, impotence, infection, and retrograde ejaculation.

Larsen believes his new method can overcome shortcomings in existing minimally-invasive BPH treatment methods.

"The lack of uniform heating along the length of the prostate is the major problem with existing devices," he says. "This leads to unnecessary tissue destruction where temperatures are too high and failure to achieve cell death in regions where temperatures are too low. Heating must be more uniform."

Experience with the existing technology thus does not fully live up to expectations, he says. The need for repeat treatment is too high, and the number of patients with only minimal improvement is too large. Because the number of men in the at-risk age group continues to grow, healthcare costs for prostate disease also continue to grow and are now estimated to exceed $4 billion per year.

His new method uses a leaky transverse electric and magnetic (TEM) wave antenna in a transurethral applicator. It heats uniformly because it radiates an RF field from numerous controlled openings ("windows") along its shield and is fed along its entire length to produce in one application a uniform electric field over the length of the gland.

The frequency of operation is at the 915 MHz ISM band to permit sufficient penetration radially to heat the periurethral cells of the enlarged transitional zone. The windows in the shield are insulated with a low-loss dielectric that prevents ohmic paths and stops "shorts" across the windows. A second dielectric surrounds the center conductor where the fields originate.

These structures are carried in a flexible catheter, along with temperature measurement from at least one location. The Food and Drug Administration requires an additional rectal-temperature measurement to ensure that the rectal mucosa remains below 45 degrees centigrade. Unlike laser treatment, a chilled-water loop cools the urethral mucosal tissue. This serves to protect that tissue, as well.

Other features are circuits to control and monitor the coupling between the applicator and prostate by the power-reflection coefficient. There is a matching network between the RF generator and the applicator to ensure that at least 99 percent of the power is coupled into the prostate.

Larsen is one of only three MD researchers at Sandia. At the laboratory since 1993, he works as a senior scientist in the Applied Biophysics Laboratory of the Applied Physics Center.

Now that the patent has been issued, Larsen says the next step will be to partner with the medical device industry and clinical centers to manufacture and test the technology on humans. The Urology Department at Albuquerque's Veterans Administration Hospital is a potential clinical partner, he says, and preliminary discussions have already been held with doctors there.

This work on improved prostate treatment technology has thus far been in the laboratory only. If proved successful, the technology could have other medical applications later, including combating swallowing disorders, Larsen says.

He has worked in medical technology research, development, and medical teaching in several organizations, including the US Army Medical Corps, Walter Reed Army Medical Center, and Baylor College of Medicine. He was president of the Medical Microwave Research Corp. in Silver Spring, Md., for six years beginning in the mid-80s and was an IEEE Congressional Fellow working on health care technology for the US Senate Governmental Affairs Committee before joining Sandia.

Larsen has 17 US patents and has authored or coauthored about 100 scientific presentations, journal articles, books, and technical reports.

Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major research and development responsibilities in national security, energy and environmental technologies, and economic competitiveness.

[Contact: Dr. Lawrence Larsen, Larry Perrine, Howard Kercheval]

25-Apr-2000