Sandia LabNews

Sandia researcher's device uses radio frequency heating to treat enlarged prostate

Millions of older men who suffer from urinary obstruction and associated pain caused by an enlarged prostate gland could benefit from new radio-frequency-treatment technology developed at Sandia

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 (15300) should have several advantages over existing ones — the treatment could be done on an outpatient basis, and a single treatment should have long-lasting benefits, perhaps for the patient’s lifetime. Also, side effects should be almost nil from the minimally invasive technique, and treatment costs could be lowered, he 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.

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 Labs’ projects in applied electromagnetics that affect diverse technologies, including communications, microwave power electronics, proximity fuzes, and directed energy. Older men typically suffer prostate problems ranging from mild urinary obstruction to cancerous prostates that can even cause death. Lawrence’s technology is designed to treat benign prostate enlargements that cause urinary obstruction and pain, not cancerous problems.

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. Symptomatic prostate enlargement is often associated simply with aging, Lawrence says. It 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 doesn’t have lasting benefits, surgery has traditionally been the only workable remedy, Lawrence says. Unfortunately, surgery is expensive and can have serious side effects, including incontinence, impotence, and infection.

Lawrence 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."

Heats uniformly via ‘windows’

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. 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.

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.

Last modified: May 22, 2000