Imaging refers to the visual representation of an object. Today, diagnostic imaging uses radiology and other techniques, mostly noninvasive, to create pictures of the human body. Diagnostic radiography studies the anatomy and physiology to diagnose an array of medical conditions. The history of medical diagnostic imaging is in many ways the history of radiology. Many imaging techniques also have scientific and industrial applications. Diagnostic imaging in its widest sense is part of biological science and may include medical photography, microscopy and techniques which are not primarily designed to produce images (e.g., electroencephalography and magnetoencephalography).
Brief overview about important developments:
Imaging used for medical purposes, began after the discovery of x-rays by Konrad Roentgen 1896. The first fifty years of radiological imaging, pictures have been created by focusing x-rays on the examined body part and direct depiction onto a single piece of film inside a special cassette.
In the 1950s, first nuclear medicine studies showed the up-take of very low-level radioactive chemicals in organs, using special gamma cameras. This diagnostic imaging technology allows information of biologic processes in vivo. Today, single photon emission computed tomography (SPECT) and positron emission tomography (PET) play an important role in both clinical research and diagnosis of biochemical and physiologic processes.
In the 1960s, the principals of sonar were applied to diagnostic imaging. Ultrasound has been imported into practically every area of medicine as an important diagnostic tool, and there are great opportunities for its further development. Looking into the future, the grand challenges include targeted contrast imaging, real-time 3D or 4D ultrasound, and molecular imaging. The earliest use of ultrasound contrast agents (USCA) was in 1968.
The introduction of computed tomography (CT/CAT) in the 1970s revolutionized medical imaging with cross sectional images of the human body and high contrast between different types of soft tissues. These developments were made possible by analog to digital converters and computers. First, spiral CT (also called helical), then multislice CT (or multi-detector row CT) technology expanded the clinical applications dramatically.
The first magnetic resonance imaging (MRI) devices were tested on clinical patients in 1980. With technological improvements including higher field strength, more open MRI magnets, faster gradient systems, and novel data-acquisition techniques, MRI is a real-time interactive imaging modality that provides both detailed structural and functional information of the body.

Today, imaging in medicine has been developed to a stage that was inconceivable a century ago, with growing modalities:
x-ray projection imaging, including conventional radiography and digital radiography;
All these types of scans are an integral part of modern healthcare. Usually, a radiologist interprets the images. Most clinical studies are acquired by a radiographer or radiologic technologist. In filmless, digital radiology departments all images are acquired and stored on computers. Because of the rapid development of digital imaging modalities, the increasing need for an efficient management leads to the widening of radiology information systems (RIS) and archival of images in digital form in a picture archiving and communication system (PACS). In telemedicine, medical images of MRI scans, x-ray examinations, CT scans and ultrasound pictures are transmitted in real time.

See also Interventional Radiology, Image Quality and CT Scanner.

The industry standard of computed tomography (CT) contrast media power injectors changed over time from single-head to dual-head systems. The advantage of a power (or pressure) injector with two syringes is that a saline solution can be injected first to open the veins, followed by a second injection with contrast agent. Then the first head flushes the saline to maintain contrast flow. As a result, much less contrast agent is needed (about 30 percent less), helping to reduce costs. Dual-head contrast media injectors also provide greater patient safety by reducing the pressure of the flow rate, helping to prevent damage to the veins.
Contrast delivery is much more controlled and efficient when using a dual-head power injector (also called double-piston injector). Also, these medical devices are required to accommodate the quick imaging times typical for a multi-detector CT scanner.

See also Contrast Media Injector, Single-Head CT Power Injector, CT Power Injector, Multi-Head Contrast Media Injector, Syringeless CT Power Injector.

(Scintillation Camera, Scintillation Gamma Camera, Gamma Scintillation Camera or Anger Gamma Camera) A gamma camera is an imaging device used in nuclear medicine to scan patients who have been injected, inhaled, or ingested with small amounts of radioactive materials emitting gamma rays. The gamma camera records the quantity and distribution of the radionuclide that is attracted to a specific organ or tissue of interest.
The first gamma camera was developed and introduced by Hal O. Anger in 1957/58. The structure hasn't changed by today. A gamma camera consists of:

Through this design the simultaneous registration of gamma ray photons is possible, the computer further allows dynamic imaging.

See also Pinhole, Elution, Center of Rotation, First Pass Scintigraphy, and Anger Hal Oscar.

(GBPS) The gated blood pool scintigraphy is an examination to evaluate the ventricular performance. This scintigraphic blood pool imaging uses an electrocardiographic synchronizer or gating device to acquire data during repeated heart cycles at specific times in the heart cycle. Radionuclides, for example 99mTc-humanserumalbumin (HSA), are used as intravascular tracers.
GBPS allows to determinate the left ventricular function with heart minute volume, ejection fraction (EF) at rest and under exercise. Single photon emission computed tomography (SPECT) versus planar scintigraphic imaging improves cardiac evaluation due to the three dimensional nature. The GBPS method is not suitable to analyze the right ventricular function; that is best evaluated by first-pass ventriculography.
Echocardiography vs. GBPS has important disadvantages due to problems in quantitative evaluation, in patients with anatomic variations and dyskinetic left ventricles.

See also Myocardial Perfusion Imaging.

(LINAC) [Linear Particle Accelerator]
An electrical device that creates high-energy radioactive materials to treat cancers. It uses electricity to form a fast-moving linear stream of subatomic particles to collide with the target. LINACs for medical use produce a beam of 6-30 MeV energy.