OP15.07: Influence of pulse repetition frequency adjustment on three‐dimensional power Doppler indices and STIC volumetric pulsatility index using an in vivo model

To determine the influence of pulse repetition frequency (PRF) upon three-dimensional (3D) power Doppler (PD) indices and volumetric pulsatility index (vPI) from spatio-temporal imaging correlation (STIC) datasets acquired from an in vivo model. Eleven STIC datasets, one for each PRF value ranging from 0.6 to 9.0 KHz, were acquired from a common carotid of a healthy young subject. The vascularization flow index (VFI) values were determined from every static 3D dataset within each STIC dataset, using Virtual Organ Computer-aided Analysis (VOCAL). VFI values along the cardiac cycle were used to construct curves for each PRF. The VFI curves demonstrated that signal intensity gradually differentiate as PRF values increased. Two patterns of curves were observed and divided into low PRF values (from 0.6 to 2.4 KHz) which displayed a ‘flattened’ pattern and high PRF values (from 3.2 to 9.0 KHz) with a ‘triphasic’ pattern. vPI values were close to zero for low PRF values; high PRF values displayed a gradual increase in vPI for each increment in PRF. Relative stability was observed between PRF values of 3.2 and 4.0 KHz: subjective visual comparison suggests that these PRFs were the most proper for the specific analysis. We concluded that PRF dramatically influences 3DPD indices and vPI. The use of PRF values in which the presence of minimum VFI values correspond to the diastolic phase in the spectral Doppler wave may validate the use of vPI. These findings still have little implication to clinical practice as 3DPD still lacks standardization but they highlight the importance of using adequate PRF settings when performing vascularity/flow assessment.