Fred Sterzer

Microwave medical devices

This article describes several new microwave medical devices that either were or are being developed at MMTC, Inc. in cooperation with the following institutions: Celsion Corporation, Columbia, Maryland (microwave balloon catheters); Montefiore Medical Center (MMC), Bronx, New York (microwave balloon catheters, dual microwave antennas, and microwave poration); and the University of California at San Francisco (conformal array antennas). The individuals who developed these devices have previously published patents and articles that contain most of the material presented here. All of the medical devices described depend on the ability of microwaves to deeply penetrate into living tissues. The depth to which microwaves can penetrate tissues is primarily a function of the dielectric properties of the tissues and of the frequency of the microwaves. In general, the lower the water content of the tissue, the deeper a wave at a given frequency can penetrate. Also, at the frequencies of interest, the lower the frequency, the deeper is the depth of penetration into tissues with given water content.

Microwave applicators for localized hyperthermia treatment of cancer of the prostate

Abstract Directional coaxial applicators designed for operation with microwave frequencies of 915 MHz or 2450 MHz are described. Hyperthermia can be induced in tumors located within, or in the vicinity of, natural body cavities by means of these applicators. This paper reports on a method developed in animal experiments for the use of these applicators as therapeutic tools and on results of initial clinical trials using this technique in cases of cancer of the prostate.

Microwave Hyperthermia for Brain Tumors

Twelve patients with malignant brain tumors who had failed to respond to conventional therapies were treated with thermotherapy. Hyperthermic temperatures (approximately 43 degrees C) were induced in the tumors using microwaves at a frequency of 2450 MHz that were guided into the tumors by one or more semirigid coaxial applicators. These applicators fit into 16 gauge tubes or needles and can be inserted into the brain with minimal damage to healthy tissues. During each treatment, the tumors were maintained at hyperthermic temperatures for 1 hour. Several treatments spaced a few days apart were usually administered. The procedure used for producing hyperthermia in brain tumors with microwaves proved to be safe and could be repeated several times without producing toxic effects. Objective tumor responses were obtained in 75% of the patients (decrease in tumor size, 3 patients; slowing of tumor growth, 2 patients; necrosis of tumor tissues verified by pathological examination, 4 patients). Favorable clinical responses were observed in 75% of the patients (rapid decrease in intractable headaches, 5 patients; improvements in clinical deficits, 4 patients). Also, in all patients, the microwave power required to heat for a given time or a given volume decreased during most of the thermotherapy sessions, possibly because of heat damage to the tumor vasculature. Our results, taken together with the results of other investigators, indicate that thermotherapy is a promising modality for treating malignant brain tumors, either as the sole therapy or in combination with radiotherapy and chemotherapy. The next logical steps would be Phase I/II type trials of subjects whose disease is less advanced than the disease of patients treated in the current series of investigations.

Microwave-induced hyperthermia in cancer treatment: apparatus and preliminary results.

Abstract Apparatus for the controlled local heating of cutaneous and subcutaneous tumors is described. This apparatus, which uses microwave radiation in the frequency 915 MHz or 2450 MHz, can raise the temperature of such tumors to the hyperthermic range (42.5–43°C), i.e. the temperature range which appears to be optimum for the treatment of malignant tumors. Encouraging results have been obtained with this apparatus in treating malignancies in laboratory animals and in man. Complete eradication of transplanted mammary adenocarcinoma was achieved in C3H mice. In several clinical cases, hyperthermis appeared to be beneficial in the treatment of basal. cell carcinoma, malignant melanoma, and skin metastases of carcinoma of the breast.

Microwave Parametric Subharmonic Oscillators for Digital Computing

In a digital information handling system, a binary one can be represented by an RF signal of a given phase, frequency, and amplitude, and a binary zero by RF of the same frequency and amplitude but with opposite phase. The use of subharmonic oscillators to switch, store, and amplify binary information coded in this manner is reviewed. A variable capacitance subharmonic oscillator having an output frequency of 2000 mc is described, and the use of this oscillator in circuits for amplifying, scaling, and performing logic functions is discussed. The circuits described operate at pulse repetition rates exceeding 100 mc. By raising the carrier frequency to X-band, it should be possible to increase the maximum rate to a few hundred megacycles.

A Self-Balancing Microwave Radiometer for Non-Invasively Measuring the Temperature of Subcutaneous Tissues During Localized Hyperthermia Treatments of Cancer

The use of a self-balanced microwave radiometer in localized rf and microwave hyperthermia treatments of cancer is described. Initial clinical observations are presented.

Microwave treatments for prostate disease

This paper describes three novel microwave techniques that show promise for being useful in treating diseases of the prostate. They are (1) Microwave Urethroplasty for providing immediate symptomatic relief of urinary obstructions caused by BPH. This technique uses microwave balloon catheters for producing biological stents in the urethra. Initial results obtained in an FDA approved Phase I clinical trial are highly encouraging. (2) Hyperthermia produced in the prostate by dual microwave balloon catheters. When combined with external beam radiation or implanted radioactive seeds this technique has the potential of improving local recurrence rates of prostate cancer over the rates that are obtained when only radiation treatments are given. (3) Microwave Poration Therapy, a therapy that when combined with either systemic or locally administered chemotherapy has been shown to be effective in shrinking implanted prostatic tumors in rats. The potential clinical advantages of microwave poration/chemotherapy over electrochemotherapy using DC pulses for treating cancers are discussed.

Applications of microwave heating in medicine

The application of microwave heating to the treatment of cancer, coronary heart disease, tachycardia, benign prostatic hypertrophy, and glaucoma are described.<<ETX>>

Fast Microwave Logic Circuits

In a carrier-type digital computer system, binary information can be represented by the presence or absence of an RF pulse in a given time interval. Using strip-line printed circuit techniques and point-contact diodes, passive AND and NOT gates were constructed which operate with RF pulses of less than 2 m?sec duration (i.e., an effective pulse repetition rate of 500 mc), at a carrier frequency of 3000 mc. The basic gates were combined to form half-adders. Unlike other carrier approaches, these circuits keep the information in RF form through all steps of the logic operations; i.e., both inputs and outputs of all elements are RF pulses.

Instrumentation for Invasive and Non-Invasive Microwave Hyperthermia of Brain Tumors

Nineteen patients with malignant brain tumors who had failed to respond to conventional therapies were treated with invasive thermotherapy. In the last four of these patients the thermotherapy was combined with brachytherapy. Hyperthermic temperatures (-43 °C) were induced in the tumors using microwaves at a frequency of 2450 MHz that were guided into the tumors by one or more semi-rigid coaxial applicators. The feasibility of non-invasively heating malignant brain tumors that are located close to the skull is being investigated. A microwave lens that can concentrate 915 MHz microwave power into small tissue volumes shows promise of being clinically useful.