Dear Editor,

Regarding Harling et al,Reference Harling, Jansson, El-Segaier and Peronen ¹ I am confused as to why the authors went to such great lengths in developing a sophisticated algorithm to analyse the color Doppler image of a patent ductus arteriosus to estimate the amount of shunting when it is common knowledge that spectral Doppler methods providethe highest temporal and velocity range resolutions when assessing flow velocities. The color Doppler method provides high spatial resolution but low temporaland velocity range resolution, which is not exactly what one should seek to use in shunt estimate algorithms. If the color Doppler signal were to be used then perhaps raw color Doppler data – prior to digital scan conversion – should be used in such algorithms and compare that to shunt ratio estimations using standard spectral Doppler methods.