Editing Doppler effect (section)

===Medical===
{{Main|Doppler ultrasonography}}
[[File:CarotidDoppler1.jpg|thumb|upright|Colour flow ultrasonography (Doppler) of a [[carotid artery]] – scanner and screen]]
An [[echocardiogram]] can, within certain limits, produce an accurate assessment of the direction of blood flow and the velocity of blood and cardiac tissue at any arbitrary point using the Doppler effect. One of the limitations is that the [[ultrasound]] beam should be as parallel to the blood flow as possible. Velocity measurements allow assessment of cardiac valve areas and function, abnormal communications between the left and right side of the heart, leaking of blood through the valves (valvular regurgitation), and calculation of the [[cardiac output]]. [[Contrast-enhanced ultrasound]] using gas-filled microbubble contrast media can be used to improve velocity or other flow-related medical measurements.<ref>{{cite journal| last1=Davies|first1=MJ| last2=Newton|first2=JD|title=Non-invasive imaging in cardiology for the generalist|journal=British Journal of Hospital Medicine| date=2 July 2017|volume=78|issue=7|pages=392–398|doi=10.12968/hmed.2017.78.7.392|pmid=28692375}}</ref><ref>{{cite journal| last1=Appis|first1=AW|last2=Tracy|first2=MJ|last3=Feinstein|first3=SB|title=Update on the safety and efficacy of commercial ultrasound contrast agents in cardiac applications|journal=Echo Research and Practice|date=1 June 2015|volume=2|issue=2| pages=R55–62|doi=10.1530/ERP-15-0018|pmid=26693339|pmc=4676450}}</ref>

Although "Doppler" has become synonymous with "velocity measurement" in medical imaging, in many cases it is not the frequency shift (Doppler shift) of the received signal that is measured, but the phase shift (''when'' the received signal arrives).<ref group=p>{{Cite journal|last=Petrescu|first=Florian Ion T|year=2015|title=Improving Medical Imaging and Blood Flow Measurement by using a New Doppler Effect Relationship|url=https://www.proquest.com/openview/cec7b768b14887621e9494261e122a4c/1?pq-origsite=gscholar&cbl=1226369|journal=American Journal of Engineering and Applied Sciences|volume=8|issue=4 |pages=582–588| via=ProQuest|doi=10.3844/ajeassp.2015.582.588|doi-access=free}}</ref>

Velocity measurements of blood flow are also used in other fields of [[medical ultrasonography]], such as [[obstetric ultrasonography]] and [[neurology]]. Velocity measurement of blood flow in arteries and veins based on Doppler effect is an effective tool for diagnosis of vascular problems like [[stenosis]].<ref>{{cite book |first1=D. H. |last1=Evans |first2=W. N. |last2=McDicken |title=Doppler Ultrasound |edition=2nd |publisher=John Wiley and Sons |location=New York |date=2000 |isbn=978-0-471-97001-9 }}{{page needed|date=June 2015}}</ref>