Expressed by velocity type: Peak Systolic Velocity (PSV) end-diastolic velocity (EDV) average velocity (MFV).
#TRANSCRANIAL DOPPLER MACHINES SERIES#
Spectral analysis is performed using Fourier series analysis algorithm (F.F.T - Fast Fourier Transform). Analyze a complex signal into discrete frequencies of corresponding amplitude and time progression. Doppler spectrum: A doppler frequency image is made of moving blood cells in an area of the vessel lumen examined over time. However, it is subjective and qualitative. The flow is more compact than the artery.
Timbre and loudness due to different frequencies and amplitudes. Transcranial doppler signal received is shown through: Sound: Doppler frequency, amplifier, speaker, ear. M mode: Displays flow strength and direction over a length of about 6cm or more the advantage of displaying all possible flow signals at a time on the same screen. B mode: Signal represents light dots, amplitude brightness, dot position is the distance from the transducer to the feedback surface. Display modes: A mode: The signal shows spikes, the height is the magnitude, the position is the distance from the probe to the feedback surface This type of representation is used in measurement because of its high accuracy. This information is processed and expressed into audio and visual signals. The transducer converts the echo into an electrical signal.
The magnitude and amplitude of the reflected wave depends on the amplitude, angle of incidence, environmental acoustic impedance, and size of the feedback surface.
The time it takes for the sound wave to travel back and forth indicates the depth of the feedback surface: d = c * t/2 (c: speed of sound propagation in the body t: time it takes for the sound wave to travel back and forth d: depth feedback side). The disadvantage is that the high velocity flow cannot be measured, the time T for the outgoing and returning pulses determines the shortest time interval between two pulses, the repetition frequency of the PRF pulses cannot be greater than 1/ T. The advantage of the transcranial doppler pulse probe is the determination of the location of the flow. Only the feedback pulse at the sampling site is analyzed. The wave propagates in sequence of pulses.
Pulse probe: The probe has a crystal that both transmits and receives. For example, when sound waves pass through two adjacent blood vessels, the recorded speed is the average speed of the two blood vessels. However, the disadvantage is that the speed is not recorded at one point, but the average speed of many points the beam meets along the way. Continuity transducer: Transducer with 2 crystals Continuity of sound waves Continuity of sound waves The advantage of the continuous transducer of transcranial doppler ultrasound is that it can measure very high velocities.
0 kommentar(er)
