RF/Microwave Delivery Systems for Therapeutic Applications - RF/Microwave Interaction with Biological Tissues - page 288

lated chick embryo hearts. In their paper entitled “Analysis of microwave
effects on isolated hearts” [130] and in other publications [132, 133], the
authors report that their experiments have shown low-intensity pulse-modu-
lated microwave energy at 2.45 GHz to have affected the heartbeat of isolated
chick embryo heart: The heartbeat is said to have changed with the increase
in modulation frequency above the natural unperturbed heart rate. In the pres-
ence of arrhythmia, the authors report having demonstrated that the heart-
beat could be regulated with the proper pulse repetition frequency. During the
experiments, the hearts were irradiated with a 2.45-GHz pulsed source having
a peak power of 10 mW and a duty cycle of 10%. The estimated incident peak
power density was 3 mW cm -2 .
4. Authors of a number of papers on the application of microwaves and
millimeter-waves to acupoints for the treatment of various ailments have sug-
gested the utilization of millimeter waves (53 GHz) to reduce the frequency
of angina attacks. The irradiation zones selected are the acupoints based on
the acupuncture theory of traditional Chinese therapy [131, 134]. At the begin-
ning of the treatment, the patients continued with their prescribed medical
therapy (drugs), with reduction of the medical dose as a function of the length
of the millimeter-wave therapy. The procedures took place once or twice a
week for 25 min at a power level of 0.1 mW.

6.9 FUTURE RESEARCH

The section on future research is relatively short, since its purpose is not to
provide an exhaustive description of the possible utilization of microwaves in
medicine. Rather its purpose is to describe to the reader the result of one
uncompleted research program in which better solutions for “tissue welding”
were sought (National Institutes of Health funded grant R41-HL55758,
“Microwave System for Tissue Anastomoses,” William P. Santamore, Principal
Investigator) and another program which is awaiting investigation on the
subject of “photodynamic therapy.” We believe that such examples will trigger
new ideas in the minds of students and other researchers.

6.9.1 Microwave Tissue Welding [135]

In Vitro and In Vivo Experimental Studies Initial studies utilizing endoscopic
techniques are revolutionizing many surgical procedures, and further expan-
sion of the endoscopic approach is inevitable. Although minimal access
surgery is advantageous to patients, the technical problems imposed by the
limited access are promoting existing tissue closure technologies. Laser tissue
welding offers several potential advantages over suture anastomosis or
closure. These include faster healing, less inflammatory response, a better flow
surface, and the ability of the weld site to grow.