Large blood vessels can produce steep temperature gradients in frozen tissues resulting in inadequate cooling temperatures during cryosurgery. In addition, arresting of blood vessels and bleeding due to rupture of large blood vessels by the iceball may cause undesired damage to healthy tissues. However, such important issues received few attentions up to now. In this article, several typical vascular models are applied to study the effects of large blood vessels to the tissue temperature distributions during cryosurgery. The thermal model combines the Pennes bioheat transfer equation describing for perfused tissues and the energy equation for blood vessels. A finite difference algorithm based on the effective heat capacity method is used to solve this complex heat transfer problems. In the algorithm, the tissues are treated as nonideal materials, freezing over a temperature range. Numerical analyses are then performed to study the influences of the blood vessels to the temperature distributions of tissues. The results indicate that different vascular models produce significantly different temperature responses for a given freezing pattern.

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