A comparison of ultrasonic beams for thermal treatment of ocular tumors.
OBJECTIVE
This study examined the relative merits of different ultrasonic beams and exposure modalities for treating ocular melanomas.


METHODS
Simulations were conducted to evaluate temperature patterns and lesion shapes induced by intense-ultrasound treatment of ocular tumors. In-vitro insonification experiments were conducted in bovine lenses.


RESULTS
Simulated hyperthermia exposures did not effectively treat tumor margins because of thermal conduction into nearby fluid-like media. Standard high-intensity focused beams produced narrow lesions during 2-s exposures. A high-intensity, multi-lobed beam, produced by a transducer with strip electrodes, generated asymmetric lesions with a single large dimension; this lesion shape could expedite the production of lesion matrices within large tumors. In-vitro cataract shapes were consistent with simulation results for focused high-intensity beams.


CONCLUSIONS
Thermal conduction and perfusion can cause underheating of tumor margins during hyperthermia unless special beam designs are used. The strip-electrode transducer configuration promises to expedite treatment of extended tumor volumes.
Lizzi
F L
FL
Biomedical Engineering Laboratories, Riverside Research Institute, 330 West 42nd Street, New York, NY 10036, USA. lizzi@rrinyc.org
Deng
C X
CX
Lee
P
P
Rosado
A
A
Silverman
R H
RH
Coleman
D J
DJ
D000818:Animals; D002386:Cataract / Q000209:etiology / Q000473:pathology; D002417:Cattle; D003198:Computer Simulation; D004566:Electrodes; D004867:Equipment Design; D005134:Eye Neoplasms / Q000473:pathology / Q000628:therapy*; D006358:Hot Temperature; D007908:Lens, Crystalline / Q000473:pathology; D008545:Melanoma / Q000473:pathology / Q000628:therapy*; D008954:Models, Biological; D013814:Thermal Conductivity; D014159:Transducers; D014464:Ultrasonic Therapy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*