LEAKAGE MEASUREMENT DURING SELECTIVE LIMB PERFUSION USING A GAMMA-PROBE

The objective of this study was to establish a probe system for intrao perative quantitative leakage measurement during selective limb perfus ion for adjuvant high-dose chemotherapy in patients with malignant mel anomas. We used a portable gamma probe with digital display and invest igated the physical properties in a phantom study simulating blood poo l activity at different angles of the probe to the surface and differe nt distances. In 20 patients the limb circulation was surgically separ ated from the systemic blood circulation, and the limb was then select ively perfused (cytostatics added) for 60 min. Initially, 15 MBq techn etium-99m labelled autologous red blood cells was injected into the li mb circulation, and an equal amount was kept as a standard. Every 10 m in, blood samples were drawn from the body circulation and count rates were simultaneously measured by the probe system at the lower end of the sternal body. At the end of perfusion, the circulation of the limb was reconnected, the standard injected into the systemic circulation, and a blood sample drawn after 10 min. All blood samples were counted for calculation of leakage in terms of percent of the injected dose, and the results compared with the intraoperative count rates of the pr obe system. In the range of leakage observed in this study (0%-86%), t he count rate of the probe system (corrected for blood volume, i.e. fo r body surface) correlated with the results of conventional measuremen t (r=0.92) according to the equation: %leakage=counts per sx[1.2 x bod y surface (m(2))-1.19]. In conclusion, the use of the described probe system is a feasible approach for leakage quantification which continu ously yields data during selective limb perfusion.