BMode

B-mode, short for brightness mode, is a standard display method used in medical ultrasonography to produce two-dimensional grayscale images. It is one of the main ultrasound imaging modes, alongside A-mode (amplitude) and M-mode (motion). In B-mode, the ultrasound system emits short pulses from a transducer and records echoes returned from tissue interfaces. Each echo's amplitude is converted into a brightness value for a pixel along the scanned line, and the collection of many lines forms a 2D cross-sectional image.

The resulting image shows tissue structures based on echogenicity; brighter echoes indicate stronger reflections. The depth corresponding to each echo is determined from the time delay, while lateral position is defined by the scanning geometry. Real-time B-mode imaging is achieved by rapid sequential line acquisitions and display updates. Resolution depends on transducer frequency, beam focusing, element count, and system dynamics; higher frequencies improve resolution but reduce penetration.

Applications and improvements: widely used in obstetrics, cardiology, radiology for organ assessment; B-mode images are compatible with Doppler modes to assess blood flow. Advances include 3D and 4D ultrasound by acquiring multiple B-mode frames to render volume datasets, compound imaging to reduce speckle, and speckle-tracking techniques. Artifacts such as acoustic shadowing, attenuation, and speckle can complicate interpretation.

Other uses: in cosmology and physics, B-mode denotes a curl-like pattern of polarized cosmic microwave background radiation, associated with primordial gravitational waves and gravitational lensing. Detection and analysis of B-mode polarization provide constraints on inflationary models and the universe's early conditions.