(ROI) Keyboard controlled identification of a given area of an image for numerical analysis and the area of anatomy being scanned that is of particular importance in the image. This area can also be a volume, than called (VOI) volume of interest.
A ROI can be used for purposes such as calculation of pixel statistics. ROI measurements should be made with the smallest area and away from boarders and edges to avoid partial volume averaging.

Radiographic contrast media (RCM) contributes important information to the diagnostic process. Actual contrast agents are safe drugs. Adverse reactions are rare, the incidence and severity of side effects decrease with the use of nonionic and low-osmolar contrast media. Adverse reactions are diverse, ranging from mild physiological disturbances to very rare life-threatening anaphylactic or anaphylactoid reactions. Users of contrast agents must be aware of the risk factors and be prepared to promptly manage adverse effects.
Side effects that may occur with intravascular administration of contrast agents are also possible after administration by other paths. Increased risk to an adverse reaction includes patients with a history of a previous reaction to a contrast medium, a known sensitivity to iodine, or a known clinical hypersensitivity (bronchial asthma, hay fever, and food allergies).

See also Contrast-Induced Nephropathy, Iodide-Induced Hyperthyroidism and Idiosyncratic Reactions.

Conversion of the analog signal to a series of digital values by measurement at a set of particular times; this utilizes the analog to digital converter. If the rate of sampling is less than twice the highest frequency in the signal, aliasing will occur. The duration of sampling determines how small a difference of frequencies can be separated.

See also Algorithm, Trigonometric Functions, Digitization, Exponential Functions, Imaginary Number, Logarithms, Point Spread Function.

(SFOV) The scan field of view is the area being scanned. This selectable scan factor is measured from a CT system isocenter to the most distant located edge of the patient.

See also Reconstruction Field Of View.

Syringeless CT power injectors (also called pressure injectors) have been developed as a solution to reduce contrast fluid waste. The Joint Commission does not allow the reuse of unused cans from disposable syringes, so the syringeless option allows facilities to use contrast media as efficiently as possible.
A syringeless CT (computed tomography) contrast media injector permits delivery to be made directly from standard contrast media bottles, featuring multi-dosing and programmable automatic saline flush. This higher loading capacity for contrast agent ( up to two contrast bottles or 1000 ml) and a bag of saline at initial setup, enables to perform multiple contrast enhanced CT scans without reloading contrast agent; resulting in increased efficiency and less waste.

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