Studies on venous chronic obstructions with perfused krypton-81m

A perfusion system is used to study the venous return of the lower limbs through an injection of a superficial vein of the foot. Multiple sequential perfusions are possible because there is no building up of the radioactivity (short-life of the Kr-81m and lung elimination). We are therefore able to study the system under different mechanical conditions (tourniquet at different sites and pressures, hyperaemia). The main veins (from popliteal vein to vena cava) are therefore normally vizualised by a peripheral injection. The region below the knee is difficult to study by venoscintigraphy. The transit times from the foot to the groin, and between regions of interest are also studied. We analyse the results obtained with a consecutive serie of 31 patients suffering from possible chronic venous problems and sequelae of deep venous thrombosis (lasting for 2 weeks to more than 20 years): 58 limbs are actually examined. Most of these limbs are also assessed by non invasive heamodynamic techniques: Doppler ultrasound and calf plethysmography: 35 limbs are normal, 23 show obliterative sequelae of deep vein thrombosis. The venoscintigraphy displays the level and the degree of obstructions and the pattern of collateral pathways with an accuracy comparable to RX-phlebography. We demonstrate that the Doppler is able to recognize most of the residual obstructions. The resistances to venous outflow measured by plethysmography are also generally increased. We are not able to demonstrate systematic and significant variations of the transit times in the different haemodynamic conditions. These parameters do not seem therefore adequate for functional assessment