A FLOW MODEL OF CEREBRAL ANEURYSMS FOR USE WITH POWER DOPPLER STUDIES

It has recently been observed using power Doppler that cerebral aneury sms appear to change size through the cardiac cycle. The purpose of th is study was to develop a pulsatile flow model of cerebral aneurysm ex pansion and to investigate whether the observations of pulsation could be confirmed using the model. The model consisted of a latex bubble g lued onto the side of a latex tube. A computer controlled pump was use d to generate pulsatile flow. The degree of bubble expansion was adjus ted by the use of flow restrictor placed in the downstream section of the How rig. Ultrasound images were acquired using an Acuson 128 XP/10 V colour How scanner. True expansion (maximum area/minimum area) was m easured from the B-scan image using a 7 MHz probe. Three observers mea sured expansion of the simulated aneurysm from the power Doppler image s using a 2 MHz probe. Expansion measured with the power Doppler decre ased as the colour gain setting increased, and decreased as the persis tence increased. The true expansion of 1.43 was comparable with the co lour gain set optimally for a persistence value of 3. The model allows simple investigations of the relationship between true aneurysm expan sion and that measured from the power Doppler images. Colour gain and persistence settings must be standardized in clinical studies.