 This technology is widely used in confirming venous pathology diagnoses . The imaging capability needed , was made possible with the developments of Doppler and color Doppler . Doppler measurements using Doppler effect can show the direction of the blood flow and its relative velocity and color Doppler is the provision of color to help interpret the image , showing for example , the blood flow towards the probe in one color and that flowing away another . Whilst the equipment itself is costly , the procedure is not . Apart from the scanner , different probes are required according to the depth to be studied . A gel is used with the probe to make a good acoustic impedance contact . The training and expertise of the examiner is important because of the many technical complications that can present . Venous anatomy for example , is not constant , for example a patient 's vein layout of the right limb is not identical to that of the left limb . 
