3D multislice CT to demonstrate the effects of compression therapy.

The aim of this paper was to show the value of the 3D modelling of the leg by multislice computed tomography (MSCT) in demonstrating the effects of compression therapy on both the superficial veins and on the limb's volume. The spiral CT with 3D reconstruction of the lower limbs (with or without injection of contrast) is an accurate method to assess the 3D shape of the leg and the diameter of the superficial/deep veins. It is possible to obtain a realistic 3D model of the leg and its anatomical structures. This makes the evaluation of the interface pressure and effects due to the compression stocking possible. The real interface pressure in vivo between the skin and compression material is verified during the CT and recorded by a probe. It is measured by using the Kikuhime device at the B1 and B points of the calf. Technical limits: are exposure to X rays, a venous injection is usually not advisable, and this exam is strictly limited to the lying position. To assess the limb's volume by MSCT, we use metallic landmarks and dedicated modeling software. According to the Laplace's law, the variations of the shape of the leg i.e. cross sections at different levels, give a radius for each location, and so different interface pressures all around the limb, can be measured. The results of these theoretical values of the interface pressure are close to the real values measured at the same location by a probe: the compression of the saphenous veins in the lying position is observed below the knee providing the pressure at the ankle (B point) is at least 25 mmHg. It is not possible to make a compression of the veins at the thigh level without a pad. Regarding the assessment of the limb's volume, it it possible to localize a limb's edema and to quantify it with a precision of less than 1%. The multislice CT is a great research tool to provide a 3D model of the limb, making the assessment of the interface pressure of stockings and the evaluation of the effects on the superficial veins possible, but its main possible limitations are the lying position, and the use of X-rays. It is also possible to make an accurate measurement of the limb's volume, and to assess the specific location of edema int he soft tissues (fat, sub-cutaneous, muscle).