Liver blood flow studies during local hyperthermia. An experimental study in rats

Regional blood flow in rat liver and in inoculated liver tumors was studied before, during and after local hyperthermia treatment at 42.0 degrees C for one hour. Hyperthermia was induced by microwave irradiation of the central liver lobe. The method used for blood flow studies was the clearance of Xenon-133 following portal and intraparenchymal injection. The wash-out curves were analyzed by using a bi-exponential approach where k1 and k2 represented the individual curve slope of the two components. The fast component, k1, was considered to denote the relative liver blood flow. There was no difference in blood flow (k1) between tumor and normal parenchyma before heating. During local hyperthermia of the liver lobe an overall statistically significant decrease in relative blood flow occurred. In normal liver parenchyma a statistically significant increase in blood flow occurred within 30 min after concluded hyperthermia with a return to prehyperthermic values. Intratumoral blood flow did not increase in the posthyperthermic period. The decrease in relative blood flow in the liver parenchyma during hyperthermia may be one explanation for liver sensitivity to hyperthermia treatment. Local hyperthermia may impair the tumor capillary network with a decreased blood flow and alteration in the intratumoral environment as a result.