ARRT Limited Scope key terms

A radiation safety principle meaning exposures should be kept As Low As Reasonably Achievable, balancing image quality needs against dose to the patient and staff.

Restricting the x-ray beam with adjustable shutters so only the area of interest is exposed, which reduces patient dose and scatter while improving image contrast.

Radiation that has been deflected from its original path within the patient or room, contributing unwanted fog and occupational dose; controlled by collimation, grids, and shielding.

Maximum permissible radiation exposures set for occupationally exposed workers and the public, expressed for whole body, lens of eye, and extremities over specified time periods.

Use of a dosimeter badge worn at collar level to record an individual's accumulated occupational radiation dose, which is reviewed periodically against established limits.

The intensity of radiation from a point source decreases in proportion to the square of the distance, so doubling distance reduces exposure to one quarter.

The distance from the x-ray tube focal spot to the image receptor; changing it alters magnification, recorded detail, and the exposure needed to maintain density.

The product of tube current and exposure time, which primarily controls the total number of x-rays produced and therefore the overall receptor exposure or density.

The maximum voltage applied across the x-ray tube, which controls the energy and penetrating power of the beam and strongly influences image contrast.

A numeric value displayed by digital systems that reflects how much radiation reached the image receptor, used to judge whether technique was appropriate.

The visible difference in brightness between adjacent structures on an image; high contrast shows few gray shades, while low contrast shows many.

The ability of an imaging system to distinguish small structures that lie close together, often described in line pairs per millimeter and affected by motion and geometry.

Enlargement of the recorded image relative to the actual object, increased by short source-to-image distance or by placing the object farther from the receptor.

Movement of the patient or equipment during exposure that blurs the image and reduces recorded detail; controlled with short exposure times and clear instructions.

A device of alternating radiopaque strips and radiolucent spaces placed between patient and receptor that absorbs scatter before it reaches the image, improving contrast.

Uneven beam intensity along the anode-cathode axis, with the cathode side more intense; positioning the thicker anatomy toward the cathode side evens receptor exposure.

The small area on the anode where x-rays are produced; a smaller focal spot improves recorded detail but limits the tube current that can be used.

Obtaining a patient's voluntary agreement to a procedure after explaining its purpose, risks, benefits, and alternatives in language the patient understands.

Verifying a patient's identity using at least two identifiers before any procedure, ensuring the correct examination is performed on the correct person.

Infection control practices applied to all patients, including hand hygiene and use of gloves, gowns, masks, and eye protection when contact with body fluids is possible.

A position in which the patient lies supine with the head lower than the feet, used to promote venous return or shift anatomy for certain procedures.

A position in which the patient lies supine with the upper body elevated, commonly used to ease breathing or for comfort during chest imaging.

The standard reference posture with the body upright, facing forward, arms at the sides, and palms forward, from which all positional terms are described.

Lying face up on the back, a common recumbent position used for abdomen and some spine projections.

Lying face down on the abdomen, a recumbent position sometimes used for spine and skull work or to bring specific anatomy closer to the receptor.

A projection or body rotation that is neither frontal nor lateral, used to separate superimposed structures such as ribs or spinal facets.

A projection in which the central ray passes side to side through the body, producing a side view that shows depth and alignment of structures.

The central portion of the x-ray beam, directed to a specific landmark and angulation; correct centering determines accurate demonstration of the anatomy of interest.

A palpable or visible surface reference, such as the iliac crest or sternal notch, used to position the central ray consistently for a given projection.

The eight small wrist bones arranged in two rows between the radius, ulna, and metacarpals; their arrangement is assessed on PA and oblique wrist projections.

Openings between adjacent vertebrae through which spinal nerves exit, best demonstrated on oblique projections of the cervical and lumbar spine.

Paired facet joints between the articular processes of adjacent vertebrae; they guide spinal motion and are evaluated on oblique and lateral spine images.

A saddle-shaped depression in the sphenoid bone that holds the pituitary gland, seen in profile on a lateral skull radiograph.

The bony cavity of the eye formed by several facial and cranial bones; its margins and foramina are assessed on skull and facial projections.

The lower jaw bone, the only movable bone of the skull, imaged with specific projections to show its body, rami, and temporomandibular joints.

The ring formed by the two hip bones, sacrum, and coccyx that supports the trunk and protects pelvic organs, evaluated on AP and oblique projections.

A pocket of gas in the stomach fundus that appears as a radiolucency under the left hemidiaphragm and helps confirm proper abdominal positioning.