Dear Professor DeGroff

We agree that raw colour data should be used as we have stated in our publication: “Optimally, vendor-specific analysis software that operates on image data acquired prior to the transfer to the DICOM system would be more optimal”. These data are available but the vendor should allow access to these data. Registrations are not ideal when digital data conversion is used. We don't think it is a good idea to compare standard spectral Doppler methods with the colour Doppler method, because the anatomical diameter measurement of the duct by echocardiography is not ideal. Using its square in flow calculations further increases the error. Moreover, one has to measure separately aortic flow with its inherent errors in order to be able to calculate Qp/Qs. Measuring Qp/Qs with colour Doppler algorithm avoids doing double errors is flow quantification and thus makes the procedure more certain. We think like you that raw colour Doppler data should be used but only animal experiments would allow testing of the precision of the method.

Sincerely Yours

Dr Solweig Harling