B-Mode Ultrasound (Brightness Mode)
Why talk about B Mode? B Mode is the foundation of the ultrasound image. It is the actual raw data returned to the transducer and displayed on the monitor without image processing. How much distortion do you want to apply to the B Mode image? Start with no processing, then add only what you need to produce a clear, focused image of the the relevant anatomy.
©Walter Rasmussen, R.D.C.S.
A-Mode: Amplitude Mode
Amplitude mode ultrasound displays the strength of the reflections from tissues encountered by the ultrasound beam as spikes rising from a baseline.
B Mode Ultrasound: When the ultrasound beam strikes structures, the amplitude of the A Mode signal increases. When the signal reaches the B Mode Plane it is converted to a proportional video signal, appearing as brighter areas (speckle} on a monitor screen. The adjustment of Gain higher, increases the number of amplitude spikes reaching the B Mode plane, revealing more weak reflectors.
Above:B-Mode ultrasound of the interventricular septum and aortic valve.
Ultrasound speckle varies in shades from pure black, indicating no ultrasound reflected, to pure white, –indicating a high amount of ultrasound reflected.
Below: Grey Scale, corresponding to the intensity of returning reflections.
Ultrasound Speckle Resolution and its relationship to Frequency, and Image Processing.
Ultrasound speckle conveys tissue texture and so is affected by transducer frequency (smaller targets are rendered at higher frequency, resulting in finer speckle). Excessive image processing (acting to blur the speckle), will lower the resolution of the original signal, increasing speckle size and decreasing resolution.
Some sonongraphers think that the ultrasound image should look smooth, blurred or even gelatinous however, when they do this they are de-focusing the speckle and decreasing tissue resolution. While blurring the image can benefit visualization of the edges of structures, it will also distort their geometry, thus creating the impression of increased thickening, degenerative or sclerotic changes.
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