Diagnostic Radiographer flashcards
Diagnostic Radiographer · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- ALARA principle
- As Low As Reasonably Achievable: radiation exposure should be minimized to the extent practical, considering economic and social factors, while achieving the diagnostic objective.
- Effective dose formula
- Effective dose E = Σ w_T · H_T, where w_T is the tissue weighting factor and H_T is the equivalent dose to that tissue; units are sieverts (Sv).
- Half-value layer
- The thickness of a specified material that reduces the intensity of a radiation beam to one half of its original value; used to measure beam quality and filtration.
- Inverse square law
- The intensity of radiation from a point source is inversely proportional to the square of the distance from the source: I₁/I₂ = (d₂/d₁)².
- Law of Bergonié and Tribondeau
- Cells are most radiosensitive when they are undifferentiated, are actively dividing, and have a long mitotic future; lymphocytes and basal cells are examples.
- Automatic exposure control
- A device that terminates the X-ray exposure when a predetermined quantity of radiation reaches the image receptor, using ionization chambers or solid-state detectors.
- Heel effect
- The variation in X-ray beam intensity across the field, with lower intensity on the anode side due to absorption of X-rays in the anode target.
- Focal spot size test
- Measured using a pinhole camera or star pattern; the image of the focal spot is evaluated to determine nominal focal spot size, typically 0.6 mm or 1.2 mm.
- Grid ratio
- The ratio of the height of the lead strips to the distance between them; higher ratios remove more scatter but require greater mAs and precise alignment.
- Deviation index
- DI = actual exposure index (EI) minus target EI; a value within ±3 indicates exposure within approximately 30% of the optimal receptor exposure.
- Photoelectric effect
- An X-ray interaction in which a photon transfers all its energy to an inner-shell electron, which is ejected; dominant at low kVp and in high-atomic-number materials.
- Compton scatter
- An X-ray interaction in which a photon interacts with an outer-shell electron, losing some energy and changing direction; produces scatter that reduces image contrast.
- Modulation transfer function
- A measure of the spatial resolution performance of an imaging system, describing how well the system transfers contrast from the object to the image at various spatial frequencies.
- PA chest radiography
- Posteroanterior projection of the chest performed erect at 180 cm SID, 110–125 kVp, with high mA and short exposure time to minimize motion.
- KUB radiograph
- Kidneys, ureters, and bladder: a supine anteroposterior abdominal radiograph at 100 cm SID, typically 70–80 kVp, used to evaluate bowel gas and calcifications.
- Caldwell projection
- A PA skull projection with a 15° caudal tube angle, performed at 100 cm SID, used to visualize the frontal sinus and orbital roofs.
- Oblique position naming
- Oblique positions are named by the side of the patient closest to the image receptor, such as right anterior oblique (RAO) or left posterior oblique (LPO).
- Informed consent elements
- Includes the nature of the procedure, risks, benefits, alternatives, and the patient's right to refuse; must be documented before invasive procedures.
- Metformin and contrast
- Metformin should be withheld for 48 hours after iodinated contrast administration in patients with renal impairment to reduce the risk of lactic acidosis.
- Universal precautions
- Infection control practice in which all blood and body fluids are treated as potentially infectious; gloves, gown, mask, and eye protection are used as indicated.
- Anaphylactoid contrast reaction
- A severe contrast media reaction with bronchospasm, laryngeal edema, or hypotension; requires immediate epinephrine, oxygen, and emergency medical response.
- Anatomical planes
- Sagittal plane divides left and right; coronal plane divides anterior and posterior; transverse (axial) plane divides superior and inferior.
- Hounsfield unit
- HU = 1000 × (μ_tissue − μ_water) / μ_water; water is 0 HU, air is −1000 HU, and dense bone is +1000 HU or higher.
- Vertebral column regions
- Cervical (7), thoracic (12), lumbar (5), sacral (5 fused), and coccygeal (3–4 fused) vertebrae; 33 total in adults.
- Mediastinal window
- A CT display setting with window width approximately 350 HU and window level approximately 50 HU, used to evaluate soft tissues of the mediastinum.
- Bremsstrahlung radiation
- X-rays produced when electrons are decelerated by the electric field of atomic nuclei; produces a continuous spectrum with maximum energy equal to the kVp.
- Characteristic X-rays
- X-rays produced when an inner-shell electron is ejected and an outer-shell electron fills the vacancy, emitting a photon with energy equal to the shell difference.
- Half-life formula
- T½ = 0.693/λ, where λ is the decay constant; activity A = λN, and N = N₀ e^(−λt).
- Minimum filtration requirement
- X-ray tubes operating above 70 kVp must have total filtration of at least 2.5 mm aluminum equivalent to remove low-energy photons and reduce patient dose.
- HIPAA Privacy Rule
- Protects individually identifiable health information and requires minimum necessary disclosure; applies to covered entities such as hospitals and radiology practices.
- ARRT Standards of Ethics
- Includes the Code of Ethics (aspirational) and Rules of Ethics (enforceable); violations may lead to sanctions, suspension, or revocation of certification.
- ARRT continuing education
- Requires 24 credits every two years, including at least 12 in the discipline of certification and 1 credit in ethics.