ALONGSIDE CONVENTIONAL COLOR-DOPPLER, 2 N EW PROCEDURES ARE AVAILABLEALLOWING REPRESENTATION OF CONSIDERABLY SLOWER BLOOD-FLOW VELOCITIES - THE MAXIMUM-ENTROPY METHOD (MEM) AND ULTRASOUND ANGIOGRAPHY (POWER DOPPLER)

Aim: The sensitivity of the two procedures for slow blood flow velocit ies in two flow phantoms examined and compared to conventional colour Doppler. Method: In two phantoms with vessels between 0.3 and 6 mm dia meter the slowest measurable blood flow with the different techniques was determined. The influence of various application angles was also s tudied. Results: The slowest blood flow velocity detected with the MEM technique was 0.6 mm/s and with the angio-technique 0.4 mm/s. Two dif ferent scan-heads were used; a 5 MHz probe for the MEM procedures and a 10 MHz probe for ultrasound angiography. Using a 10 MHz scan-head wi ll most likely lead to increased sensitivity of MEM. Blood flow repres entation with the MEM technique is real-time, while several seconds of acquisition time are required for the angio-technique, which is a dis advantage during clinical use. Conventional Doppler was merely able to represent 15 mm/s blood flow. The angio-technique was less dependent on the application angle than the MEM procedure. Conclusion: The defin itely increased sensitivity of the two colour methods open up new area s in the diagnosis of organ and tumour perfusion.