A preliminary study on a novel approach to the assessment of the sample volume length and registration accuracy in PW Doppler quality control

Sample volume (SV) in PW Doppler is usually characterized by two main factors, i.e., sample volume size and range gate registration accuracy, which have been included among the recommended Quality Control (QC) Doppler tests commonly proposed in the literature. However, most of the studies focusing on these two factors date back to the last years of the XX century. In this context, the present preliminary study proposes and investigates a novel approach for the automatic analysis of faults in both sample volume length and registration accuracy through the post-processing of PW Doppler spectrograms. In particular, a Velocity Profile Discrepancy Index (VPDI) has been defined and assessed under the hypothesis of laminar flow and parabolic velocity profiles in the examined conduct. According to the definition hereby proposed, VPDI is expected to be as close as possible to 0 for a good agreement between theoretical and measured velocity profile, therefore suggesting that the displayed PW spectrogram is not affected by significant SV error sources. A single ultrasound (US) system of intermediate technology level, equipped with three probe models, has been used to acquire the PW spectrograms obtained for six different SV positions (i.e., six sample volume depths) with respect to the tube diameter of a Doppler flow phantom. Tests have been repeated for all the US probes operating at two Doppler frequencies each. Based on the preliminary promising outcomes, further studies may be needed that include (i) increasing the number of diagnostic systems, (ii) exploring different US system settings, (iii) improving the test protocol to estimate the two error sources separately.