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Doppler interrogation: Difference between revisions
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(Created page with 'INTRODUCTION — While M-mode and 2D echocardiography create ultrasonic images of the heart, Doppler echocardiography utilizes ultrasound to record blood flow within the cardiova...') |
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The value of ø is particularly important for accurate assessment of high velocity jets, which occur in aortic stenosis or pulmonary artery hypertension. It is generally assumed that ø is 0º and cos ø is therefore 1. | The value of ø is particularly important for accurate assessment of high velocity jets, which occur in aortic stenosis or pulmonary artery hypertension. It is generally assumed that ø is 0º and cos ø is therefore 1. | ||
Spectral analysis — When the backscattered signal is received by the transducer, the difference between the transmitted and backscattered signal is determined by comparing the two waveforms with the frequency content analyzed by fast Fourier transform (FFT). The display generated by this frequency analysis is termed spectral analysis. By convention, time is displayed on the x (horizontal) axis and frequency shift on the y (vertical) axis. Shifts toward the transducer are represented as "positive" deflections from the "zero" baseline, and shifts away from the transducer are displayed as "negative" deflections | Spectral analysis — When the backscattered signal is received by the transducer, the difference between the transmitted and backscattered signal is determined by comparing the two waveforms with the frequency content analyzed by fast Fourier transform (FFT). The display generated by this frequency analysis is termed spectral analysis. By convention, time is displayed on the x (horizontal) axis and frequency shift on the y (vertical) axis. Shifts toward the transducer are represented as "positive" deflections from the "zero" baseline, and shifts away from the transducer are displayed as "negative" deflections. | ||
Multiple frequencies exist at every time point. Each received frequency is displayed, with the magnitude (or amplitude) shown as the "brightness" of each frequency shift component. | Multiple frequencies exist at every time point. Each received frequency is displayed, with the magnitude (or amplitude) shown as the "brightness" of each frequency shift component. | ||
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It is important to remember that this simplified Bernoulli formula measures the pressure difference, not absolute pressure. In addition, it is imperative that accurate measurement of V2 be obtained. Due to the squaring of V2, a 10 percent error in V2 will result in a 20 percent error in the pressure estimate. (See "Aortic valve area in aortic stenosis".) | It is important to remember that this simplified Bernoulli formula measures the pressure difference, not absolute pressure. In addition, it is imperative that accurate measurement of V2 be obtained. Due to the squaring of V2, a 10 percent error in V2 will result in a 20 percent error in the pressure estimate. (See "Aortic valve area in aortic stenosis".) | ||
References: | |||
www.uptodate.org | |||
Otto | |||
Feigenbaum | |||