Doppler sonography: This imaging technique makes use of the Doppler effect in detection and measuring moving targets, typically blood.Most imaging techniques are operating in B-mode. Īn imaging technique refers to a method of signal generation and processing that results in a specific application. This has also been referred to as C-mode. Three-dimensional imaging is done by combining B-mode images, using dedicated rotating or stationary probes. As the actual speed of sound varies greatly in different tissue types, an ultrasound image is therefore not a true tomographic representation of the body. Most machines convert two-way time to imaging depth using as assumed speed of sound of 1540 m/s. As moving tissue transitions produce backscattering, this can be used to determine the displacement of specific organ structures, most commonly the heart. This mode is an ultrasound analogy to streak video recording in high-speed photography. The M-mode image dimensions are however voltage as a function of two-way time and recording time. Each next line is plotted adjacent to the previous, resulting in an image that looks like a B-mode image. The backscattered signal is converted to lines of bright pixels, whose brightness linearly correlates to backscattered voltage amplitudes.
M-mode: In motion mode, A-mode pulses are emitted in succession.The dimensions of B-mode images are voltage as a function of angle and two-way time. Each pixel value of the image correlates to voltage amplitude registered from backscattered signal. B-mode: In brightness mode, an array of transducer elements scans a plane through the body resulting in a two-dimensional image.The voltage amplitudes recorded correlate linearly to acoustic pressure amplitudes. A single pulse is transmitted through the body and scatters back to the same transducer element. A-mode: Amplitude mode refers to the mode in which the amplitude of the transducer voltage is recorded as a function of two-way travel time of an ultrasound pulse.Several modes of ultrasound are used in medical imaging: The imaging mode refers to probe and machine settings that result in specific dimensions of the ultrasound image. At the extreme, very small transducers can be mounted on small diameter catheters and placed within blood vessels to image the walls and disease of those vessels. For this purpose, special-use transducers, including transvaginal, endorectal, and transesophageal transducers are commonly employed. Most ultrasound examination is done using a transducer on the surface of the body, but improved visualization is often possible if a transducer can be placed inside the body. An ultrasound result on fetal biometry printed on a piece of paperĪ general-purpose ultrasound transducer may be used for most imaging purposes but some situations may require the use of a specialized transducer.
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