DHA Radiology / Radiographer flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ALARA principle

ALARA means keeping radiation doses as low as reasonably achievable, considering economic and social factors, while still obtaining the required diagnostic information.

Inverse square law

For a point source, radiation intensity is inversely proportional to the square of the distance, so doubling distance reduces intensity to one quarter.

Equivalent dose

Equivalent dose, measured in sieverts, equals absorbed dose in gray multiplied by the radiation weighting factor and reflects biological harm from different radiation types.

Effective dose

Effective dose, measured in sieverts, sums equivalent doses to tissues after multiplying by tissue weighting factors and estimates whole-body stochastic risk.

Stochastic effect

A stochastic radiation effect has no dose threshold; its probability increases with dose, but severity does not, and cancer induction is the main example.

Bremsstrahlung

Bremsstrahlung is continuous x-radiation produced when electrons decelerate in the anode target, and its maximum photon energy equals the applied tube voltage.

Characteristic radiation

Characteristic x-rays are emitted when an incoming electron removes an inner-shell electron and an outer-shell electron fills the vacancy, producing discrete energies specific to the target element.

Tube current

Tube current, measured in milliamperes, controls the number of electrons crossing the x-ray tube and therefore the quantity of x-ray photons produced per unit time.

DICOM

DICOM is the standard for storing, transferring, and displaying medical images, including patient metadata and worklists, allowing equipment from different vendors to interoperate.

PACS

A picture archiving and communication system stores, retrieves, distributes, and displays medical images electronically and integrates with the radiology information system.

PA chest projection

In a PA chest radiograph, the x-ray beam enters posteriorly and exits anteriorly, the patient stands upright, and a 180-centimeter source-to-image distance reduces magnification.

KUB radiograph

A KUB radiograph is a supine anteroposterior abdominal image showing kidneys, ureters, and bladder; it is used to assess bowel gas, calcifications, and tube positions.

Anode heel effect

The anode heel effect makes the x-ray beam intensity lower on the anode side because photons produced deeper in the target are absorbed by the anode itself.

Spatial resolution

Spatial resolution is the ability to distinguish small adjacent structures, commonly expressed in line pairs per millimeter and limited by focal spot, detector, and motion.

Quantum mottle

Quantum mottle is grainy image noise caused by too few x-ray photons reaching the detector; increasing mAs or using a larger detector element can reduce it.

Repeat analysis

Repeat analysis reviews rejected or repeated radiographs to identify causes such as positioning errors, exposure errors, artifacts, and equipment faults, guiding quality improvement.

Flat-field calibration

Flat-field calibration corrects detector pixel gain and offset variations by exposing the detector uniformly, producing a uniform image and reducing fixed-pattern noise.

Hounsfield unit

A Hounsfield unit expresses computed tomography attenuation relative to water, with water at zero, air near minus one thousand, and dense bone near plus one thousand.

Axial plane

The axial plane divides the body into superior and inferior sections and is the standard plane for computed tomography images displayed as if viewed from below.

Pneumothorax

A pneumothorax is air in the pleural space that produces increased lucency and absent lung markings on radiographs and may cause mediastinal shift in tension.

Cardiomegaly

Cardiomegaly is enlargement of the heart, often defined on a frontal chest radiograph when the cardiothoracic ratio exceeds one half in an adult.

Informed consent

Informed consent requires that a competent patient receives adequate information about benefits, risks, and alternatives and voluntarily agrees to the procedure.

Two-patient identifiers

Two patient identifiers, such as full name and date of birth, must be confirmed before imaging to prevent wrong-patient errors and ensure correct documentation.

Iodinated contrast reaction

An iodinated contrast reaction may range from mild urticaria to severe bronchospasm or hypotension; management includes stopping contrast, airway support, and epinephrine when severe.

Barium contraindication

Barium sulfate should not be used when gastrointestinal perforation or a leak is suspected because spillage into the peritoneum can cause severe inflammation; water-soluble contrast is preferred.

Extravasation management

For contrast extravasation, stop the injection, remove the cannula, elevate the limb, apply cold compress unless specific protocol says otherwise, and monitor for swelling and neurovascular change.

Standard precautions

Standard precautions apply to all patients and include hand hygiene, gloves, gown, mask, eye protection, safe injection practices, and safe handling of contaminated equipment.

Airborne precautions

Airborne precautions require a negative-pressure room and fitted N95 respirator for infections spread by small droplets, such as tuberculosis, measles, and varicella.

Personal dosimeter

A personal dosimeter measures occupational radiation dose and should be worn at chest or collar level outside the lead apron, with a second badge under the apron when required.

RACE fire response

RACE stands for rescue, alarm, contain, and evacuate; it guides immediate response to fire by removing people, activating alarms, closing doors, and evacuating if needed.

Negligence elements

Negligence requires four elements: a duty of care, a breach of that duty, causation of harm, and actual damages; all four must be proved.

Confidentiality

Confidentiality means protecting patient health information from unauthorized disclosure and sharing it only with those who need it for care or as permitted by law.