Diagnostic imaging

Diagnostic imaging also called medical imaging, refers to the ensemble of methods used to generate visual representations of objects of clinical interest. These include x-rays, computed tomography (CT), magnetic resonance imaging (MRI), Positron emission tomography (PET), Radionuclide angiography, Single Photon Emission Computed Tompography (SPECT) and ultrasonography. They are usually used to provide supplementary diagnostic information as well as to monitor the progress of disease and/or therapy.

Physicians who devote their careers in the interpretation of these methods are radiologists or nuclear medicine specialists. Both specialties do other work besides imaging, but, in general, radiologists are concerned with images produced by directing an electromagnetic or ultrasound signal through the body to a receiver, where nuclear medicine is concerned with obtaining images from radioactive substances inside the body. Biomedical engineers also assist in the process of image analysis by using engineering and computer science principles to interpret images.

Not all of these methods, such as ultrasonography, use radioactivity. There are evolving methods that look at heat distribution at the skin surface. A Wood's Light, which emits ultraviolet light, is commonly used in dermatology; some skin lesions exhibit fluorescence under this illumination.

The interpretation of radiographs may be facilitated by:
 * access to prior images
 * Single reader assisted by computer-aided detection (CAD).
 * Double reading with arbitration (as opposed to consensus) Double reading may be better than single reader with CAD.
 * Fusing several types of imaging, such the anatomical detail of CT and the physiological data with PET, into a composite image, perhaps incorporating other antatomically correlated data, such as histopathology. Composite imaging is technically challenging and requires much computerized image processing, when the various imaging techniques use different coordinate systems, different orientation (e.g. axial vs. planar) and have different levels of resolution.