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 M-mode (Motion-mode) ultrasound is used for analyzing moving body parts (also called time-motion or TM-mode) commonly in cardiac and fetal cardiac imaging. The application of B-mode and a strip chart recorder allows visualization of the structures as a function of depth and time. The M-mode ultrasound transducer beam is stationary while the echoes from a moving reflector are received at varying times.
A single beam in an ultrasound scan is used to produce the one-dimensional M-mode picture, where movement of a structure such as a heart valve can be depicted in a wave-like manner. The high sampling frequency (up to 1000 pulses per second) is useful in assessing rates and motion, particularly in cardiac structures such as the various valves and the chamber walls.

The term 'sonogram' is often used interchangeably with 'ultrasound,' but it specifically refers to the resulting image or picture produced during a diagnostic ultrasound examination, also known as ultrasonography or sonography. It serves as a visual representation of the echoes detected by the transducer and provides detailed anatomical information about the area being examined. Sonograms are typically displayed on a monitor, printed on film, or stored digitally for further analysis and documentation by medical professionals such as sonographers and radiologists. They serve as invaluable diagnostic tools, aiding in the detection and evaluation of various medical conditions, as well as guiding interventions, ultrasound therapy, and treatment planning.
The term 'ultrasound' itself refers to the technology used during a sonogram, but it also finds several other applications beyond medical imaging. These include echolocation, crack detection, and cleaning, among others.
See also Ultrasound Imaging, Ultrasound Technology, Handheld Ultrasound, Ultrasound Accessories and Supplies, Environmental Protection and Ultrasound Elastography.

The definition of imaging is the visual representation of an object. Medical imaging is a broad term that encompasses various imaging modalities and techniques used in the field of medicine to visualize and study the body's anatomy and physiology. It includes both diagnostic and non-diagnostic imaging procedures, where diagnostic imaging specifically refers to the subset of medical imaging techniques that are primarily focused on diagnosing diseases or conditions. Medical imaging techniques are employed to obtain images or visual representations of the internal organs, tissues, and structures, aiding in the diagnosis, treatment, and monitoring of medical conditions.
The field of medical imaging has significantly evolved since the discovery of X-rays by Konrad Roentgen in 1896. Initially, radiological imaging involved focusing X-rays on the body and capturing the images on a single piece of film within a specialized cassette. Subsequent advancements introduced the use of fluorescent screens and special glasses for real-time visualization of X-ray images.
A significant breakthrough came with the application of contrast agents, enhancing image contrast and improving organ visualization. In the 1950s, nuclear medicine studies utilizing gamma cameras demonstrated the uptake of low-level radioactive chemicals in organs, enabling the observation of biological processes in vivo. Currently, positron emission tomography (PET) and single photon emission computed tomography (SPECT) technologies play pivotal roles in clinical research and the diagnosis of biochemical and physiological processes. Additionally, the advent of the x-ray image intensifier in 1955 facilitated the capture and display of x-ray movies.
In the 1960s, diagnostic imaging incorporated the principles of sonar, using ultrasonic waves generated by a quartz crystal. These waves, reflecting at the interfaces between different tissues, were received by ultrasound machines and translated into images through computer algorithms and reconstruction software. Ultrasound (ultrasonography) has become an indispensable diagnostic tool across various medical specialties, with immense potential for further advancements such as targeted contrast imaging, real-time 3D or 4D ultrasound, and molecular imaging. The first use of ultrasound contrast agents (USCA) dates back to 1968.
Digital imaging techniques were introduced in the 1970s, revolutionizing conventional fluoroscopic image intensifiers. Godfrey Hounsfield's pioneering work led to the development of the first computed tomography (CT) scanner. Digital images are now electronic snapshots represented as grids of dots or pixels. X-ray CT brought about a breakthrough in medical imaging by providing cross-sectional images of the human body with high contrast between different types of soft tissue. These advancements were made possible by analog-to-digital converters and computers. The introduction of multislice spiral CT technology dramatically expanded the clinical applications of CT scans.
The first magnetic resonance imaging (MRI) devices were tested on clinical patients in 1980. With technological improvements, such as higher field strength, more open MRI magnets, faster gradient systems, and novel data-acquisition techniques, MRI has emerged as a real-time interactive imaging modality capable of providing detailed structural and functional information of the body.
Today, imaging in medicine offers a wide range of modalities, including:

These imaging modalities have become integral components of modern healthcare. With the rapid advancement of digital imaging, efficient management has become important, leading to the expansion of radiology information systems (RIS) and the adoption of Picture Archiving and Communication Systems (PACS) for digital image archiving. In telemedicine, real-time transmission of all medical image modalities from MRI to X-ray, CT and ultrasound has become the standard. The field of medical imaging continues to evolve, promising further innovations and advancements in the future, ultimately contributing to improved patient care and diagnostics.

See also History of Ultrasound Contrast Agents, and History of Ultrasound.