Small Animal Hyperthermia Ultrasound System
An external ultrasound system has been developed for the heating of
subcutaneously implanted tumors in small animals. This small animal
hyperthermia ultrasound system (SAHUS) was designed to be compatible with a microPET scanner to facilitate studies of
hyperthermia effects on tumor hypoxia. Collimation of thermal energy
deposition, a specific goal for this device to avoid regional and/or systemic
heating of small animals, was demonstrated thermometrically using
thermoradiography following high-power short-time heating of a layered gel
phantom. The system consisted of an acrylic applicator with up to four
independent 5MHz non-focused ultrasound transducers, 10-channel RF
generator, 16-channel thermocouple thermometer, and a PC with PID
controller based power regulation software. The
system is capable of performing a real time temperature feedback control of
power deposited independently in each tumor, and simultaneously in up to four
tumors at the time. The performance of the SAHUS was tested in over 90 experiments using 5 different cell-lines
grown in thighs of female nude (nu/nu) mice. In vivo intratumoral temperatures were
recorded during heating trials with interstitially implanted thermocouples.
Compatibility with the microPET system was tested by carrying out
studies on the same tumor model before and during SAHUS induced hyperthermia.
The SAHUS was able to produce hyperthermia in target temperature of 41.5 °C, and maintained within a narrow temperature
range (regulation error -0.02±0.10 °C) for up to 4 hours without significantly raising the core temperature of the animals. The concurrent operation of the SAHUS and the
microPET did not show any interference.
The design and construction of SAHUS was supported by a grant from the US National Cancer
Institute, R01 CA63121. The animal studies were supported by the following grants: R01 CA71638, CA104457, CA106587 and K08 CA88924.
Experience with a Small Animal Hyperthermia Ultrasound System (SAHUS): Report on 83 Tumors. Physics in Medicine and
Biology, 2005; 50: pp 5127-5139.
Localized versus regional hyperthermia: comparison of xenotransplants treated with a small animal ultrasound and
waterbath limb immersion. International Journal of Hyperthermia, 2005; 21(3): pp 271-281.
small animal hyperthermia ultrasound system (SAHUS) for sustainable, collimated and controlled hyperthermia of
subcutaneously implanted tumours. International Journal of Hyperthermia, 2004;20(1): pp 32-44.
Diagram of SAHUS with applicator positioned in a microPET.
SAHUS controlling software.