ABR Core Exam key terms

A radiation-protection principle directing that exposures be kept as low as reasonably achievable, accounting for economic and social factors, while still obtaining the needed diagnostic information.

A tissue-weighted sum of absorbed doses across organs, expressed in sieverts, used to estimate overall stochastic radiation risk to a reference person.

A standardized measure of radiation output per unit volume for a given CT protocol, derived from phantom measurements and displayed on the scanner console.

The product of CTDIvol and scanned length, estimating total radiation output for an entire CT examination and enabling comparison across protocols.

The product of x-ray tube current in milliamperes and exposure time in seconds, denoted mAs, which primarily determines the quantity of photons produced.

The thickness of a specified material that reduces the intensity of a narrow beam of radiation to half its original value, characterizing beam quality and filtration.

Interaction in which an incident photon transfers all its energy to an inner-shell electron, producing characteristic radiation; probability rises sharply with atomic number and falls with photon energy.

Interaction in which a photon transfers part of its energy to a loosely bound electron and is deflected, producing scattered radiation that degrades image contrast.

The ratio of grid height to the distance between lead strips; higher ratios improve scatter rejection but demand more precise centering and higher exposure.

A curve describing how faithfully an imaging system reproduces contrast at each spatial frequency, reflecting spatial resolution performance.

A measure of how efficiently an imaging detector converts incident x-ray quanta into output signal relative to an ideal detector, combining resolution and noise performance.

The ratio of meaningful signal amplitude to background noise in an image or measurement; higher values generally indicate more reliable detection of structures.

A normalized CT attenuation scale on which water is zero and air is approximately negative one thousand, with dense bone reaching roughly positive one thousand or more.

Selection of display window width and level to map a range of CT attenuation values onto the available gray scale, optimizing contrast for a tissue of interest.

The time constant describing recovery of longitudinal magnetization after an radiofrequency pulse; tissues with short T1 recover quickly and appear bright on T1-weighted images.

The time constant describing decay of transverse magnetization from spin-spin interactions; tissues with long T2 retain signal longer and appear bright on T2-weighted images.

The interval between successive radiofrequency excitation pulses in a magnetic resonance pulse sequence, influencing T1 weighting and total scan duration.

The interval between the excitation pulse and the peak of the measured signal echo in magnetic resonance imaging, influencing T2 weighting.

The binding of toxic free gadolinium ions by a ligand to create a stable complex that is excreted renally, reducing the risk of nephrogenic systemic fibrosis.

A fibrosing disorder of skin and internal organs occurring in some patients with severe renal impairment after exposure to certain gadolinium-based contrast agents.

Acute kidney injury occurring shortly after intravascular iodinated contrast administration, diagnosed after excluding other causes and often defined by a rise in serum creatinine.

An adverse response to iodinated contrast medium, ranging from mild physiologic symptoms to anaphylactoid reactions, with risk factors including prior reaction and asthma.

Evidence-based guidelines developed by expert panels that rate the appropriateness of imaging studies for specific clinical scenarios to support ordering decisions.

A campaign providing evidence-based recommendations to avoid unnecessary tests and treatments, including many imaging examinations lacking clear benefit.

A standardized lexicon and final assessment category system for breast imaging reports, ranging from category zero for incomplete to category six for known biopsy-proven malignancy.

A standardized reporting system for liver imaging in patients at risk for hepatocellular carcinoma, assigning categories that convey probability of malignancy and guide management.

A standardized assessment system for multiparametric prostate magnetic resonance imaging that stratifies lesions by likelihood of clinically significant cancer and informs biopsy decisions.

Consensus recommendations for management of incidentally detected pulmonary nodules, specifying follow-up imaging intervals based on nodule size, morphology, and patient risk.

An abnormality discovered during an examination performed for an unrelated indication, requiring judgment about further workup and communication to the referring clinician.

A structured process in which radiologists evaluate a sample of colleagues' reports and images for accuracy and quality, supporting continuous professional improvement.

A systematic method for identifying underlying system failures that contributed to an adverse event, with the goal of preventing recurrence rather than assigning individual blame.

An organizational framework that distinguishes human error from at-risk or reckless behavior, encouraging error reporting while maintaining accountability for unsafe choices.

A communication technique in which the receiver repeats back an order or critical result to confirm accurate understanding, reducing errors during high-stakes exchanges.

The transfer of patient information and responsibility between care teams, ideally using a structured format to prevent omissions and miscommunication.

The proportion of patients with disease who test positive; a highly sensitive test is useful for ruling out disease when negative.

The proportion of patients without disease who test negative; a highly specific test is useful for confirming disease when positive.

The probability that a patient with a positive test result truly has the disease, which depends on both test characteristics and disease prevalence in the population tested.

A plot of sensitivity against false-positive rate across all possible test thresholds, with area under the curve summarizing overall discriminatory performance.