Angiography means the imaging of veins and arteries. The examination is called angiogram.

See also CT Angiography, Coronary Angiogram, Digital Subtraction Angiography, Venography and Magnetic Resonance Angiography MRA, Contrast Media Injector, Single-Head CT Power Injector.

Annihilation in general refers to the transition of a particle and its antiparticle by collision into something different, depending on their energies and based on the conservation of energy and momentum. The electromagnetic radiation emitted is the result of the annihilation (combination and disappearance) of an electron and a positron. Two gamma rays of 0.511 MeV energy, assuming very low-energy particles, are emitted perpendicular to each other.

An antiparticle is a subatomic particle similar in mass but with opposite electromagnetic properties. Most particles have their antiparticles, electron - positron, etc. Antimatter is composed of antiparticles. Colliding of a particle with its respective antiparticle leads in case of low-energy particles mostly to photon production, in case of high-energy particles to exotic heavy particles.

An arthrography is a radiographic examination of a joint (such as the knee, shoulder, hip, elbow or wrist) that requires an injection of a contrast medium into the joint space.
For an opaque x-ray arthrography a water-soluble iodinated contrast agent is injected and a series of fluoroscopic controlled images is produced. Magnetic resonance arthrography combines the arthrogram with MRI. A small quantity of gadolinium contrast agent is added to the injection into the joint space. The traditional radiographic images are followed by an MRI of the extremities. A non-invasive possibility is an indirect MR arthrography, which doesn't require the injection into the joint. The dye is given prior to the imaging procedure.
The contrast fluid produces a bright signal and allows evaluation of small defects of the joint capsule, assessment of articular surface and labral cartilage, and in case of an indirect arthrogram also of the surrounding soft tissue. If a gaseous medium is used, this exam is called pneumoarthrography and a combination with liquid contrast is used in double-contrast arthrography.
MR arthrography is often used to evaluate hip and acetabular labrum, shoulder rotator cuff and glenoid labrum (see Shoulder MRI), and less often in wrist and knee MRI studies. Also combinations of CT and nuclear medical techniques with arthrography are available.

A stream of electromagnetic or particulate radiation that could be collimated and is generally unidirectional or divergent usually from a small source and restricted to a small-solid angle.

See also Ion Beam, Broad Beam, Useful Beam and Beam On Time.