Arterial spectral Doppler

Spectral Doppler measurements of hepatic arterial and portal venous blood flows are used for calculation of the DPI, i.e. ratio of hepatic arterial flow to total liver flow. In normal subjects the DPI is 0.25 (the hepatic artery contributes <25% of total liver blood flow), but this increases in arterialisation due to metastases. An excellent correlation between raised DPI and overt metastatic disease has been documented in colon and gastric cancer. In colon cancer patients with no overt liver malignancy, a raised DPI preoperatively correlated strongly with a shorter disease free survival and development of overtliver metastases within 5 years postoperatively, indicative of occult disease at presentation (Leen et... 

Following identification at color Doppler ultrasound, the cavernosal vessels are interrogated. Pulse-wave (PW) duplex Doppler is turned on putting the sample volume on the cavernosal arteries. The spectral analysis is preferably performed at the base of the penis where the Doppler angle is particularly favorable (between 30° and 50°) and the flow velocity shows major reproducibility and correctness (Mills and Sethia 1996). The flow velocity must be measured repeatedly (at least three times) at the same level and the mean value reported. Functional studies have shown a progressive decrease of blood velocity in the cavernosal arteries from the base to the glans penis... 

When the arterial obstruction is complete, color Doppler imaging can show flow inversion in the cavernosal artery, easily detected in the longitudinal and transversal scans because of the different color of flow (Fig. 6.16). At spectral analysis the flow is reversed in the proximal portion of the artery and normally directed in the distal part. The curve obtained is of low amplitude with increased time to peak. The... 

Initially, light pressure is used so as not to collapse the vein (Fig. 4.33a). With the probe straddling both artery and vein, further pressure is subsequently applied. If the vein is patent, the walls collapse and appose each other completely (Fig. 4.33b). When the pressure is released, the lumen of the vein returns to normal. If the vein contains clots, it will not collapse but remains distended when applying probe pressure (Fig. 4.33a,b). In lower limb veins, Doppler imaging and spectral analysis reveal monophasic venous flow rather than triphasic waveforms. In contrast, upper limb veins demonstrate more pulsatile flow because of their closer proximity to the heart (Chin et al. 2005). The use of low velocity (3-6 cm/s)... 

Fig. 5.13a,b. Early callus formation following fracture of the distal tibia, a Color Doppler 12-5 MHz US image obtained 12 days after treatment shows a bone defect (arrowheads) related to the fracture site and multiple blood flow signals (arrow) in the periosseous soft tissues superficial to the fracture, b Spectral analysis reveals low-resistance (RI <0.50) arterial flow in the vessels surrounding the fracture. These features indicate initial normal development of fracture callus... 

Fig. 4.2.18. Doppler US of hepatic artery stenosis showing the typical tardus-parvus waveform pattern (prolonged acceleration time, spectral broadening), with a resistive index of less than 0.5...

Sikdar et al. (2004) have used vascular ultrasound to record arterial wall vibrations from ex vivo 3.1 mm lamb arteries that have been partially ligated to model a 40% stenosis. Flow is provided from a pulsatile pump to match flow in a human artery. The apparatus was used to generate stenosis-induced sounds and were recorded by both ultrasound recording of vascular sounds and a fiber-optic microphone. To illustrate the frequency content microphone records a Fourier transform was applied to the microphone data to provide spectral data for both the ultrasound and Doppler records. 

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