advanced medical imaging

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Modes of sonography Several different modes of ultrasound are used in medical imaging. [7]  These are: A-mode: A-mode is the simplest type of ultrasound. A single transducer scans a line through the  body with the echoes plotted on screen as a function of depth. Therapeutic ultrasound aimed at a specific tumor or calculus is also A-mode, to allow for pinpoint accurate focus of the destructive wave energy. B-mode: In B-mode ultrasound, a linear array of transducers simultaneously scans a plane through the body that can be viewed as a two-dimensional image on screen. M-mode: M stands for motion. In m-mode a rapid sequence of B-mode scans whose images follow each other in sequence on screen enables doctors to see and measure range of motion, as the organ boundaries that produce reflections move relative to the probe. Doppler mode: This mode makes use of the Doppler effect in measuring and visualizing blood flow o Color doppler: Velocity information is presented as a color coded overlay on top of a B- mode image o Continuous doppler: Doppler information is sampled along a line through the body, and all velocities detected at each time point is presented (on a time line) o Pulsed wave (PW) doppler: Doppler information is sampled from only a small sample volume (defined in 2D image), and presented on a timeline o Duplex: a common name for the simultaneous presentation of 2D and (usually) PW doppler information. (Using modern ultrasound machines color doppler is almost always also used, hence the alternative name Triplex.) o 4B Mode: A four dimensional B-mode ultrasound means length, width, and depth over time so that a moving three-dimensional image is seen on the monitor. o In 3D ultrasound (US) several 2D images are acquired by moving the probe across the body surface or rotating inserted probes. 3D-mode uses the same basic concept of a 2D ultrasound but rather than take the image from a single angle, the sonographer takes a volume image. The volume image that is displayed on the screen is software rendering of all of the detect ed soft- tissue combined by special ized computer software to form three-di mensional i mages. The 3D volume rendering technique (VR) does not rely on segmentation (segmentation techniques are difficult to apply to ultrasound pictures) and makes it possible to obtain clear  3D ultrasound images for clinical diagnosis. A 3D ultrasound produces a still image. Diagnosti c US systems with 3D display functions and linear  array probes are mainly used for  obstetric and abdominal  applications. The combi nation of  contrast agents, harmoni c imaging and power Doppl er  greatl y improves 3D US reconstructions. 3D imaging shows a better look at the organ being examined and is used for: Detection of abnormal fetus development, e.g. of the face and limbs Visualization of e.g. the colon and rectum Detection of cancerous and benign tumors, e.g. tumors of the prostate gland, and breast lesions Pictures of blood flow in various organs or a fetus

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