Article

The effect of blood perfusion rate on the temperature distributions induced by multiple, scanned and focused ultrasonic beams in dogs' kidneys in vivo.

Arizona Cancer Center, University of Arizona Health Sciences Center, Tucson 85724.
International Journal of Hyperthermia (impact factor: 1.92). 5(4):485-97. pp.485-97
Source: PubMed

ABSTRACT The effect of blood perfusion rate on the temperature distribution during scanned, focused ultrasound hyperthermia was investigated using an in vivo dog kidney model. The results showed that the ultrasound beams could penetrate through the body wall without severe distortion, and that they could be used to induce controlled temperature elevations in the target volume. The blood perfusion rate of the heated tissue significantly modified the temperature distribution and the temperatures achieved in the kidney with no flow were about five times higher than in the case with full flow for the same applied acoustic power. It was also demonstrated that the power deposition pattern produced by scanned focused ultrasonic fields could be modified to give an acceptable temperature distribution in different perfusion situations. Similar trends were also obtained by using the bioheat transfer equation to simulate the experiment. Both the magnitude of the temperature elevations and the effect of perfusion on the temperature distributions obtained in the experiments were in agreement with the simulations. The main difference occurred at high perfusion rates where the experiments showed significant temperature elevation outside of the scanned volume and the simulation results predicted hardly any temperature increase 5 mm outside the scan. These observations indicate that both the theoretical power calculation programme and the temperature simulations will have value in the design of optimal heating systems, treatment planning and in the retrospective of the achieved temperature distributions.

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Keywords

acceptable temperature distribution
 
achieved temperature distributions
 
blood perfusion rate
 
body wall
 
full flow
 
main difference
 
optimal heating systems
 
perfusion rates
 
power deposition pattern
 
scanned volume
 
significant temperature elevation
 
simulation results
 
simulations
 
target volume
 
temperature increase 5
 
temperature simulations
 
temperatures
 
theoretical power calculation programme
 
ultrasound beams
 
vivo dog kidney model