"Aliasing occurs in colour Doppler when the speed of blood flow exceeds 0.4-0.7m/s 6."
"The Nyquist limit defines the frequency at which aliasing and range ambiguity will occur, and is equal to the PRF/2. Factors such as higher velocities of target structures and increasing depth of the region of interest insonated will result in aliasing and consequent range ambiguity. Other potential causative factors include:"
"A specific use for aliasing in echocardiography is the calculation of the effective regurgitation orifice area in the assessment of valvular regurgitation, most commonly involving the mitral valve. With colour Doppler interrogation of a mitral regurgitant jet, a hemispheric flow convergence forms surface area tapering to form the vena contracta before entering the left atrium. The hemispheric area (PISA) is calculated and the product of PISA and aliasing velocity yields regurgitant flow. The quotient with calculated MR regurgitant VTI yields EROA."
"A specific use for aliasing in echocardiography is the calculation of the effective regurgitation orifice area in the assessment of valvular regurgitation, most commonly involving the mitral valve. With colour Doppler interrogation of a mitral regurgitant jet, a hemispheric flow convergence forms surface area tapering to form the vena contracta before entering the left atrium. The hemispheric area (PISA) is calculated and the product of PISA and aliasing velocity yields regurgitant flow. The quotient with calculated MR regurgitant VTI yields EROA."
"A specific use for aliasing in echocardiography is the calculation of the effective regurgitation orifice area in the assessment of valvular regurgitation, most commonly involving the mitral valve. With colour Doppler interrogation of a mitral regurgitant jet, a hemispheric flow convergence forms surface area tapering to form the vena contracta before entering the left atrium. The hemispheric area (PISA) is calculated and the product of PISA and aliasing velocity yields regurgitant flow. The quotient with calculated MR regurgitant VTI yields EROA."
"In case of spectral Doppler the velocity peak is cut off at the peak of the scale, and the peak is displayed at the bottom of the scale, often overlapping with the rest of the curve. The artifact can be quickly remedied by lowering the baseline (if display of flow away from the transducer is not required), or increasing the PRF."
"Pulsed wave Doppler"
"Colour flow Doppler"
Expected headings
"Physics"
"Clinical use"
"Ultrasound"
"Echocardiography"
"Pulsed wave Doppler"
"Colour flow Doppler"
"Pulsed wave Doppler and colour flow Doppler operate on this presumption; when a location of interest is designated, the ultrasound machine will only record returning echoes during an interval that corresponds to the time necessary for wave egress and return along a linear path. If Doppler shifts occur at a frequency exceeding the maximum pulse interval (1/pulse repetition frequency) detected phase shifts will be calculated based on incorrect assumptions."