Power modulation is a non-linear method, based on a multi-pulse technique where the acoustic amplitude (and hence power) of the transmitted pulses is changed. Full and half amplitudes pulses are used to induce changes in the response of the contrast agent. The received echoes from the emitted half amplitude pulse are adjusted with the full amplitude pulse and this pairs of pulses are subtracted. Power modulation is used to separate contrast agent echoes at low mechanical index, allowing real-time perfusion imaging.
Power modulation can be used with a low frequency wide band transducer to increase the depth and transmit the sound beam homogenous allowing ultraharmonic imaging.

Sonography [aka: ultrasonography] is a term that encompasses the entire process of performing ultrasound examinations and interpreting the obtained images.
Sonography involves the skilled application of ultrasound technology by trained professionals known as sonographers or ultrasound technologists. These specialists operate the ultrasound equipment, manipulate the transducer, and acquire the necessary pictures for diagnostic imaging purposes. Sonography requires in-depth knowledge of anatomy, physiology, and pathology to accurately interpret the ultrasound images and provide valuable information to the treating physician.
Sonography uses equipment that generates high frequency sound waves to produce images from muscles, soft tissues, fluid collections, and vascular structures of the human body. Obstetric sonography is commonly used during pregnancy. Sonography visualizes anatomy, function, and pathology of for example gallbladder, kidneys, pancreas, spleen, liver, uterus, ovaries, urinary bladder, eye, thyroid, breast, aorta, veins and arteries in the extremities, carotid arteries in the neck, as well as the heart.
A typical medical ultrasound machine, usually a real-time scanner, operates in the frequency range of 2 to 13 megahertz.

See also Musculoskeletal and Joint Ultrasound, Pediatric Ultrasound, Cerebrovascular Ultrasonography and Contrast Enhanced Ultrasound.

The elements of a rectangular array transducer (also called matrix transducer) are arranged in a rectangular pattern. Rectangular arrays with unequal rows (e.g. 3, 5, 7) of transducer elements are in real 2D (two-dimensional), but they are termed 1.5D, because the number of rows is much less than the number of columns. Their main advantage is electronic focusing even in the elevation plane (z-plane).
The transducers that are termed 2D have an equal number of rows and columns. 2D transducers have the potential to provide real-time 3D ultrasound imaging without moving the transducer.
Active matrix array transducers have several elements in the short axis and in addition multiple elements along the long axis. This allows electronic focusing in both axes, resulting in a narrower elevation axis beam width in the near field and far field.

2D ultrasound imaging is a widely used technique in medical imaging that provides two-dimensional visual representations of internal structures. A handheld device known as a probe or transducer contains piezoelectric crystals that emit and receive ultrasound waves which penetrate tissues and bounce back as echoes. The echoes are detected and converted into electrical signals. These signals are processed and displayed on a monitor, creating a real-time 2D grayscale image, with different shades of gray representing various tissue densities. The brighter areas on the image correspond to structures that reflect more ultrasound waves, while darker areas represent structures that reflect fewer waves or are attenuated by intervening tissues. The 2D-mode (or B-mode) provides cross-sectional views of the scanned area, showing a single plane or slice of the scanned area at a time.

Key Features and Uses of 2D Ultrasound:

Comparison with 3D and 4D Ultrasound:
See also Ultrasound Technology, Sonographer, Ultrasound Elastography, Obstetric and Gynecologic Ultrasound.

Also called B-mode echography, B-mode sonography, 2D-mode, and sonogram.
B-mode ultrasound (Brightness-mode) is the display of a 2D-map of B-mode data, currently the most common form of ultrasound imaging.
The development from A-mode to B-mode is that the ultrasound signal is used to produce various points whose brightness depends on the amplitude instead of the spiking vertical movements in the A-mode. Sweeping a narrow ultrasound beam through the area being examined while transmitting pulses and detecting echoes along closely spaced scan lines produces B-scan images. The vertical position of each bright dot is determined by the time delay from pulse transmission to return of the echo, and the horizontal position by the location of the receiving transducer element.
To generate a rapid series of individual 2D images that show motion, the ultrasound beam is swept repeatedly. The returning sound pulses in B-mode have different shades of darkness depending on their intensities. The varying shades of gray reflect variations in the texture of internal organs. This form of display (solid areas appear white and fluid areas appear black) is also called gray scale.

Different types of displayed B-mode images are:
The probe movement can be performed manual (compound and static B-scanner) or automatic (real-time scanner).
The image reconstruction can be parallel or sector type.

See also B-Scan, 4B-Mode, and Harmonic B-Mode Imaging.