Measurement of blood supply to murine tumours using in vivo red cell labelling and dynamic scintigraphy.

Blood pool and flow were studied in transplanted adenocarcinomas on the legs of mice. The animals' red blood cells were labelled in vivo by consecutive injections of a stannous compound and 99mTc-pertechnetate. The distribution of radioactivity was then recorded continuously with a gamma camera. This method allows prolonged and repeated estimations of blood supply to undisturbed tumours in conscious mice. It was found that in small tumours (under 1 ml) circulating blood pool was usually high, often 2 or 3 times that in normal leg tissues. In tumours bigger than 1 ml blood pool per unit volume tended to be lower but was still about 1.5 times the normal tissue level. This relatively large blood volume would seem to be outweighed by a very slow rate of flow. Even in the small tumours blood perfusion was greatly reduced compared to that in the normal leg. The blood pool results here provide no evidence that in tumours larger than 1 ml blood supply decreased progressively with growth.