Blood flow and heat transfer in Walker 256 mammary carcinoma.

True thermal conductivity of 13 Walker 256 mammary carcinomas in noninbred Sprague-Dawley rats averaged 3.2+/-0.9 mW/cm/degrees C under physiologic conditions. A comparison of the effective thermal conductivity in 4 tumors with and without blood flow revealed large differences ranging from 14 to 132%. When the blood supply to the tumor was doubled or reduced to one-half, the effective thermal conductivity varied proportionally to the square root of the perfusion rate. The values of thermal conductivity were obtained from a tumor preparation in which blood flow was monitored continuously during temperature changes. These changes were measured by thermistors and produced by thermal probes incorporated by the growing tumor, not surgically inserted within the tissue at the time of measurement. Inasmuch as tissue necrosis was not a dominant factor, the data are interpreted to reflect the degree of difference in local perfusion of the neoplastic tissue.