Use of a gamma camera for measuring limb blood flow in peripheral vascular disease.

A method for measuring limb blood flow during reactive hyperaemia is described. Pneumatic cuffs inflated to 300 mmHg are used to isolate the blood in the limbs from the rest of the circulation. The remaining blood is labelled with technetium. The increase in radioactivity in the limb following release of the cuffs is measured using a gamma camera. The mean rate of flow of blood to the limb (in ml (100 ml)-1 tissue min-1) is derived from the graph of radioactivity versus time and from the radioactivity in a sample of venous blood. The results of measurements carried out in patients with peripheral vascular disease (30 limbs) and normal controls (24 limbs) are presented. Repeated studies in 10 subjects (20 limbs) showed the method to be highly reproducible at high and low flow rates (r = 0.99). Case studies illustrating the use of the method as a screening test for peripheral vascular disease and to monitor the effects of treatment are presented.

The measurement of limb blood flow using technetium-labelled red blood cells.

A method for measuring blood flow below the knee during reactive hyperaemia induced by 3 min of arterial occlusion has been developed. Subjects are positioned with lower limbs within the field of view of a gamma camera and pneumatic cuffs are placed below the knees to isolate the blood and induce a hyperaemic response. The remaining blood pool is labelled with 99Tcm-labelled red cells. Blood flows have been derived from the initial gradients of time-activity curves and from equilibrium blood sampling. The technique has been validated using a tissue-equivalent leg phantom and peristaltic pump. The method has been applied to a small group of patients with peripheral vascular disease and to normal controls. The mean value (+/- SD) of limb perfusion for normal controls was found to be 16.4 +/- 3.0 ml/100 ml/min and for patients with intermittent claudication was 5.1 +/- 2.6 ml/100 ml/min. Flow measurements are found to correlate with clinical findings and with symptoms. Reproducibility (established by repeated measurements) is high. The method is well tolerated even by patients suffering from rest pain.