ARRT Radiography terminology

The ARRT Radiography Boards glossary, A to Z.

Q: How many terms are tested on the ARRT Radiography Boards?

ARRT does not publish a term count, and the exam itself is secure, so any total is a guess and we will not give you one. What we can state precisely: this glossary defines 185 terms, each linked to a related chapter. Not every term is on the ARRT content outline. For example, Stenvers Method is on neither ARRT outline, IVU is absent from the 2027 outline, and Pi Lines is a film-screen artifact.

Q: Should I memorize all the radiography terminology?

You don't need to memorize every term verbatim. You need to understand each one well enough to recognize it in a question stem and in the rationale. ARRT publishes content categories, not how often a term appears, so nobody can honestly rank terms as most tested. A sensible place to start is these families: positioning vocabulary (projection, position, angulation), fracture types (Colles, Boxer, Salter-Harris), legal terms (battery, negligence, malpractice, informed consent), photon interactions (photoelectric, Compton), and dose units (Gy, Sv, the SI units ARRT says are primary on the exam).

Q: How is this glossary organized?

Alphabetically A through Z, with a link from each term to a related chapter. 185 terms, linked to 25 of the 28 chapters in the curriculum. Use Cmd-F or Ctrl-F to search the page for any term you encounter in a practice question.

Plain-English definitions of 185 terms for ARRT Radiography registry study. Each term links to a related chapter in the curriculum.

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10 Posterior Ribs Rule: On a properly inspired PA chest, at least 10 posterior ribs should be visible above the diaphragm. See Chest Radiography → Practice questions →
10-Day Rule: Older rule to schedule pelvic and lower abdominal exams in the first 10 days after menstruation begins, when Ehrlich and Coakes say pregnancy is least likely. Bontrager calls it obsolete, because canceling essential exams may do more harm than the fetal dose. Follow your department's pregnancy screening policy. See Radiation Protection → Practice questions →
15% Rule: A 15% increase in kVp doubles density; halve mAs to compensate. A 15% decrease halves density; double mAs. See Radiographic Quality → Practice questions →
30% Density Rule: Film-era rule of thumb: mAs must change by at least 25% to 30% (Bontrager), or about 30% (Bushong), to make a visible difference in density. See Radiographic Quality → Practice questions →

A

ABS (Automatic Brightness Stabilization): Fluoroscopic system that works like a phototimer to hold image brightness steady. ARRT's outlines call it automatic brightness control (ABC). See Equipment Operation & QA → Practice questions →
AC Joint Separation: Acromioclavicular ligament injury. Imaged with weighted and unweighted bilateral AP projections of the shoulders. See Elbow, Humerus & Shoulder Positioning → Practice questions →
Additive Pathology: Disease that increases tissue density, such as pleural effusion or atelectasis. Bontrager increases exposure for these, but lists generally no change for pneumonia. See Pathology → Practice questions →
AEC (Automatic Exposure Control): Ionization chamber or solid-state detector that terminates exposure when the preset radiation level reaches the IR. Bontrager lists a recommended cell location for each projection, so cell selection and centering matter. See Radiographic Quality → Practice questions →
Air Gap Technique: Moving the receptor 10 to 15 cm from the patient instead of using a grid, so much of the scatter misses it. More magnification, and mAs rises about 10% per centimeter of gap. See Radiographic Quality → Practice questions →
Air-Fluid Level: Horizontal interface between air and fluid in a body cavity. In a child's sinus, Merrill's says it would probably warrant a diagnosis of sinusitis when clinical and laboratory findings strongly support it. See Skull, Facial Bones & Sinuses → Practice questions →
Airborne Precautions: Negative-pressure isolation room, for tuberculosis, measles and varicella (chickenpox). N95 or higher for tuberculosis and measles. For varicella, CDC makes no recommendation on mask or respirator type, while Ehrlich and Coakes says susceptible staff who must enter wear an N95 or higher, so follow facility policy. See Infection Control → Practice questions →
ALARA: As Low As Reasonably Achievable. The operational principle of all radiation protection. See Radiation Protection → Practice questions →
Anaphylaxis: Severe systemic allergic-like reaction with bronchospasm, hypotension, and laryngeal edema. Maintain the airway and call a code. Epinephrine is the drug of choice (Ehrlich and Coakes); ACR's table gives it IV, or IM if no IV access. See Patient Monitoring → Practice questions →
Anatomic Position: Standing erect, palms forward, feet pointing ahead. The universal reference for all directional terminology. See Positioning Terminology → Practice questions →
Anode: Positive electrode (the target). Tungsten-rhenium rotating disk in modern diagnostic tubes. See Equipment Operation & QA → Practice questions →
Anode Heel Effect: Beam intensity is greater on the cathode side of the field due to anode self-absorption on the anode side. See Equipment Operation & QA → Practice questions →
Aortography: Contrast imaging of the thoracic or abdominal aorta by angiography. The common femoral artery has historically been the usual access (Merrill's). See Urinary System & Contrast Studies → Practice questions →
AP Axial Cervical: AP projection with 15–20° cephalic central-ray angulation. Demonstrates C3 through C7 with the intervertebral disk spaces open. See Cervical & Thoracic Spine Positioning → Practice questions →
AP Mortise: Ankle projection with 15–20° internal rotation. Opens the talocrural joint space free of overlap. See Foot, Ankle & Calcaneus Positioning → Practice questions →
ARRT Rule 21: Duty to report violations by other technologists or candidates. Failing to report is itself a violation. See Ethics, Law & Communication → Practice questions →
ARRT Rule 22: Duty to immediately report any error in patient care to your supervisor, whether or not the patient was injured. See Ethics, Law & Communication → Practice questions →
Autotransformer: Variable-ratio transformer that selects kVp by tapping different points along a single coil. See Equipment Operation & QA → Practice questions →
Avulsion Fracture: A small piece of bone is pulled away by the attached ligament or tendon. Common at insertions. See Trauma, Mobile & Surgical Radiography → Practice questions →

B

Barium Sulfate: Positive contrast used in GI imaging. Coats mucosa, distends lumen. Contraindicated when perforation is suspected, because barium that escapes into the peritoneal cavity can cause intestinal infarcts or peritonitis. Bontrager and Merrill's use water-soluble iodinated contrast instead. Bontrager warns against that contrast with iodine sensitivity or severe dehydration. See Esophagus, Stomach & Biliary → Practice questions →
Battery: Unauthorized physical contact, for example, performing an exam after a patient has refused. Distinct from assault, which is the threat alone. See Ethics, Law & Communication → Practice questions →
Beam-Light Field Alignment: Tolerance: within 2% of SID. At 40 inches, beam edge can deviate up to 0.8 inches from light field edge. See Equipment Operation & QA → Practice questions →
Bennett Fracture: Longitudinal fracture at the base of the first metacarpal, entering the carpometacarpal joint, generally with a posterior dislocation or subluxation. See Hand, Wrist & Forearm Positioning → Practice questions →
Body Mechanics: Lifting and movement principles that protect the radiographer's spine: legs not back, wide base, load close to center. See Patient Transfer & Body Mechanics → Practice questions →
Boxer's Fracture: Fracture usually of the distal fifth metacarpal, at the metacarpal neck, with apex posterior angulation best seen on the lateral. Results from punching. See Hand, Wrist & Forearm Positioning → Practice questions →
Breathing Technique: Slow, shallow breathing during exposure to blur overlying lung markings and ribs, as on a lateral T-spine. See Cervical & Thoracic Spine Positioning → Practice questions →
Bremsstrahlung: X-ray photon produced when an incident electron is decelerated by the nucleus of an anode atom. Continuous energy spectrum. See Radiation Physics & Radiobiology → Practice questions →
Brightness Gain: Image intensifier gain. Product of minification gain and flux gain. See Equipment Operation & QA → Practice questions →
Bucky Factor: Ratio of x-rays incident on the grid to x-rays transmitted, which sets the mAs penalty for a grid. Bushong's Table 11-2 averages: 8:1 about 4, 12:1 about 5, 16:1 about 6. The factor rises with kVp. See Radiographic Quality → Practice questions →

C

C-A-B Sequence: Compressions, Airway, Breathing. The 2010 AHA CPR guidelines recommend this order for adults and children in place of the older A-B-C. See Patient Monitoring → Practice questions →
Caldwell Method: PA skull with CR 15° caudad to OML. Demonstrates frontal bone and anterior ethmoid air cells. See Skull, Facial Bones & Sinuses → Practice questions →
Caldwell PA: PA sinus projection with 15° caudad CR to OML. Demonstrates frontal and anterior ethmoid sinuses. See Skull, Facial Bones & Sinuses → Practice questions →
Camp-Coventry Method: PA knee with 40–50° flexion and 40–50° caudad central ray. Alternative for the intercondylar fossa. See Knee, Leg & Patella → Practice questions →
Cardiac Catheterization: Catheter-based imaging of the coronary arteries. The femoral artery was historically the most common access site, and Merrill's says the radial artery is quickly becoming preferred. See Urinary System & Contrast Studies → Practice questions →
Cardiothoracic Ratio: Ratio of the heart's greatest width to the chest cavity's greatest width on a PA radiograph. A value above 0.50 is considered abnormal. See Chest Radiography → Practice questions →
Cathode: Negative electrode containing the filament(s). Source of electrons via thermionic emission. See Equipment Operation & QA → Practice questions →
Cerebral Angiography: Contrast study of carotid and vertebral arteries. Maps the cerebral vessels and locates lesions such as an aneurysm. See Urinary System & Contrast Studies → Practice questions →
Characteristic Radiation: X-ray photon produced when a K-shell electron is ejected and replaced by an outer-shell electron. Discrete energy specific to the anode material (tungsten K-shell binding ~69 keV; emitted characteristic photons ~57-69 keV). See Radiation Physics & Radiobiology → Practice questions →
Coherent Scatter: Low-energy photon interacts with the atom and scatters with no energy loss. Minor at diagnostic energies. See Radiation Physics & Radiobiology → Practice questions →
Colles Fracture: Transverse fracture of the distal radius with dorsal (posterior) displacement of the distal fragment. From a fall on outstretched hand. See Hand, Wrist & Forearm Positioning → Practice questions →
Collimation: Restriction of the beam to the area of clinical interest. Reduces scatter, improves contrast, lowers patient dose. See Radiographic Quality → Practice questions →
Comminuted Fracture: Fracture in which the bone is splintered or crushed at the site of impact. See Trauma, Mobile & Surgical Radiography → Practice questions →
Compound Fracture: Fracture in which the splintered ends of bone are forced through the skin. Contrasts with a closed fracture. See Trauma, Mobile & Surgical Radiography → Practice questions →
Compton Scatter: Photon transfers partial energy to outer-shell electron and scatters at lower energy. Source of patient and operator dose. See Radiation Physics & Radiobiology → Practice questions →
Contact Precautions: Gown, gloves, dedicated equipment. Used for MRSA, VRE, C. diff, scabies, and other contact-transmitted organisms. See Infection Control → Practice questions →
Contrast: Range of densities (gray scale) on the image. On film, kVp is the controlling factor. On digital systems, displayed contrast is set by processing (LUT and window width). See Radiographic Quality → Practice questions →
Coronal Plane: Vertical plane that divides the body into anterior and posterior portions. Also called the frontal plane. See Positioning Terminology → Practice questions →
Coronary Angiography: Imaging of the LAD, circumflex, and right coronary arteries. Performed during cardiac cath. See Urinary System & Contrast Studies → Practice questions →
Costophrenic Angle: The extreme outermost lower corner of each lung, where the diaphragm meets the ribs. See Chest Radiography → Practice questions →
Cross-Table Lateral: Lateral projection performed with a horizontal central ray and the patient supine. Used for trauma C-spine and hip imaging. See Trauma, Mobile & Surgical Radiography → Practice questions →
Cross-Table Lateral C-Spine: Horizontal-beam lateral with the patient supine, used in C-spine trauma. Many emergency departments now routinely order CT to rule out injury (Bontrager). See Cervical & Thoracic Spine Positioning → Practice questions →
Cyanosis: Bluish discoloration of skin and mucous membranes from low oxygen saturation. A clinical sign, not a diagnosis. See Patient Monitoring → Practice questions →
Cycle of Infection: The six-link chain (agent, reservoir, portal of exit, transmission, portal of entry, susceptible host). Breaking any link stops infection. See Infection Control → Practice questions →

D

Danelius-Miller Method: Cross-table axiolateral hip projection. Used for trauma when the patient cannot rotate the affected leg. See Femur, Pelvis & Hip → Practice questions →
Density: Film term for overall blackness, controlled primarily by mAs. Digital systems speak of receptor exposure and brightness, and Bushong warns that mAs does not control OD on CR. See Radiographic Quality → Practice questions →
Destructive Pathology: Disease that decreases tissue density, such as emphysema or osteoporosis. Bontrager decreases exposure for these, but lists generally no change for pneumothorax. See Pathology → Practice questions →
Deterministic Effect: Threshold effect (skin erythema, cataracts). Severity increases with dose above the threshold. See Radiation Physics & Radiobiology → Practice questions →
Diagnostic Quality Checklist: Our label for a systematic image check, not a textbook term. Bontrager's five criteria: anatomy demonstrated, positioning, collimation and CR, exposure, and side markers. Artifacts can also compromise quality. See Radiographic Quality → Practice questions →
Distortion: Misrepresentation of size or shape. Size = magnification (SID/SOD). Shape = elongation/foreshortening (CR angulation). See Radiographic Quality → Practice questions →
Don't Move Rule: With possible spinal injury or severe trauma, do not attempt to move the patient (Bontrager). Adapt the tube and IR to the patient instead. See Trauma, Mobile & Surgical Radiography → Practice questions →
Dose Creep: Gradual rise in exposure over time. Digital systems still yield a good image when overexposed, and higher technique gives less noisy images, so levels drift up unless exposure is monitored. See Digital Image Processing → Practice questions →
Double-Contrast Study: Combination of barium + air/CO2. Barium coats the mucosa, gas distends the lumen for maximum mucosal detail. See Esophagus, Stomach & Biliary → Practice questions →
Droplet Precautions: Mask when close to the patient. CDC's traditional distance is 3 feet or less, and it says a mask may be prudent within 6 to 10 feet or on room entry. Used for influenza, pertussis, mumps, meningococcal disease. See Infection Control → Practice questions →
DSA (Digital Subtraction Angiography): Subtraction technique that removes overlying bone and tissue, leaving only the contrast-filled vessels. See Urinary System & Contrast Studies → Practice questions →

E

Elongation: Shape distortion from CR or IR being angled relative to the part. Projects longer than reality. See Radiographic Quality → Practice questions →
Erect Position: Patient sitting or standing upright. Bontrager says sinus radiography should be done erect, if possible, to show air-fluid levels. See Skull, Facial Bones & Sinuses → Practice questions →
Exposure Index: CR/DR numeric metric of receptor exposure, judged against the target for that exam. The IEC standard index rises in proportion to receptor dose. On the Deviation Index, 0 is on target, positive is overexposure and negative is underexposure. Vendor indices differ: Siemens EXI rises with exposure while Fuji S and Philips EI fall, so always check the manufacturer convention. See Digital Image Processing → Practice questions →
Exposure Index (EI): Manufacturer-specific or IEC-standardized estimate of receptor exposure. Tracks under- and overexposure. See Digital Image Processing → Practice questions →

F

Filtration: Aluminum sheets that remove low-energy photons. Required minimum total: 2.5 mm Al equivalent above 70 kVp. See Radiographic Quality → Practice questions →
Focal Spot: The area on the anode where the electron beam strikes. Smaller focal spot = sharper image but lower thermal capacity. See Radiographic Quality → Practice questions →
Focal Spot Tolerance: Bushong's QC table lists ±50% for focal-spot size. His NEMA table sets limits by size: a nominal 1.0 × 1.0 mm spot may measure up to 1.4 × 2.0 mm. See Equipment Operation & QA → Practice questions →
Focusing Cup: Negative-charged cup around the filament that focuses the electron beam onto the target. See Equipment Operation & QA → Practice questions →
Fomite: An inanimate object that carries infectious organisms (a cassette, a marker, a cell phone). Disinfect between patients. See Infection Control → Practice questions →
Foreshortening: Shape distortion from the part being at an angle to the IR. Projects shorter than reality. See Radiographic Quality → Practice questions →
Frontal Sinus: Air-filled cavity in the frontal bone above the orbits. Best demonstrated on the Caldwell. See Skull, Facial Bones & Sinuses → Practice questions →

G

Gastrografin (Water-Soluble Iodinated Contrast): Substitute for barium when GI perforation is suspected. Safer because it is absorbable from the peritoneum. See Esophagus, Stomach & Biliary → Practice questions →
Grashey Method: AP oblique shoulder with 35–45° body rotation toward the affected side. Demonstrates the glenohumeral joint space in profile. See Elbow, Humerus & Shoulder Positioning → Practice questions →
Gray (Gy): SI unit of absorbed dose. 1 Gy = 100 rad. See Radiation Protection → Practice questions →
Greenstick Fracture: Incomplete fracture seen in pediatric bones. The cortex bends and breaks on one side only. See Trauma, Mobile & Surgical Radiography → Practice questions →
Grid Cutoff: Density loss caused by improper grid positioning (off-center, off-level, off-focus, upside down). See Radiographic Quality → Practice questions →
Grid Ratio: Height of lead strips ÷ distance between strips. Higher ratio = better scatter cleanup, more mAs required. See Radiographic Quality → Practice questions →

H

Half-Value Layer (HVL): Thickness of aluminum that reduces beam intensity by 50%. Federal minimum at 80 kVp: 2.9 mm Al on current equipment and 2.3 mm Al in the older column of 21 CFR 1020.30(m), which Sherer's table still prints. See Equipment Operation & QA → Practice questions →
Heat Units (HU): Quantification of tube thermal load. HU = kVp x mA x s x generator multiplier: single-phase = 1.0; three-phase (6- or 12-pulse) and high-frequency = 1.4. See Equipment Operation & QA → Practice questions →
Heel Effect: Beam intensity is greater on the cathode side of the field. Place thicker body parts on the cathode side. See Radiographic Quality → Practice questions →
Hepatobiliary Imaging: Imaging of the liver, gallbladder, and biliary tree. Includes T-tube cholangiography and operative cholangiography. See Esophagus, Stomach & Biliary → Practice questions →
HIPAA: Health Insurance Portability and Accountability Act of 1996. Its Privacy Rule protects individually identifiable health information held by covered entities, in electronic, paper, or oral form. See Ethics, Law & Communication → Practice questions →
Histogram: Graph of how often each pixel value occurs in an image. Its shape is characteristic of each projection, and most digital systems store and analyze these plots by projection, so selecting the right one matters. See Digital Image Processing → Practice questions →
Holmblad Method: PA axial knee, kneeling, with the CR perpendicular to the lower leg. Knee flexion is 60 to 70 degrees in Bontrager and 70 degrees in Merrill's. Demonstrates the intercondylar fossa. See Knee, Leg & Patella → Practice questions →
Horizontal Beam: Central ray traveling parallel to the floor. Required to demonstrate air-fluid levels when the patient is erect. See Skull, Facial Bones & Sinuses → Practice questions →

I

Image Intensifier: Fluoroscopic device that converts x-rays to visible light, accelerates electrons, and focuses onto a small output phosphor. See Equipment Operation & QA → Practice questions →
Informed Consent: Patient's signed permission after a full explanation of the procedure, its risks and benefits, and the outcomes of not having it. The patient must be competent. Only a parent or legal guardian may sign for a minor. It can be revoked at any time. See Ethics, Law & Communication → Practice questions →
Intensifying Screen: Film-era phosphor screen that converts x-ray photons to visible light and lowers patient dose. Bushong gives intensification factors of 20 to 100 and 40 to 400 by screen type. See Radiographic Quality → Practice questions →
Inverse Square Law: Beam intensity is inversely proportional to the square of the distance from the source. Double SID = 1/4 intensity. See Radiographic Quality → Practice questions →
IVU (Intravenous Urography): Contrast study of the urinary tract with timed images; department routines vary (Bontrager). On the ARRT 2022 outline, in force until 2027-02-28, and absent from the 2027 outline. See Urinary System & Contrast Studies → Practice questions →

J

Jones Fracture: Fracture at the base of the 5th metatarsal, checked on the foot and ankle views that include it. See Foot, Ankle & Calcaneus Positioning → Practice questions →

K

kVp: Kilovoltage peak. Controls beam quality (penetration) and contrast scale. Higher kVp = longer gray scale. See Radiographic Quality → Practice questions →
kVp Accuracy: AAPM TG-150 expects measured kVp within 5 kV or 5%, whichever is greater. Bushong's older QC table prints ±10%. Use the limit your program or the question names. See Equipment Operation & QA → Practice questions →

L

Last-Image Hold (LIH): Fluoroscopic feature that preserves the last frame on screen without continuing exposure. See Radiation Protection → Practice questions →
Lateral Decubitus: Patient lying on their side with a horizontal central ray. Used to demonstrate air-fluid levels and free air. See Positioning Terminology → Practice questions →
Lead Apron: Minimum 0.25 mm Pb equivalent. 0.5 mm preferred for fluoroscopy. Fluoroscope aprons and gloves at least once a year to check for defects. See Radiation Protection → Practice questions →
Lead Marker Rule: R or L lead marker must be visible inside the collimated field, anatomically correct, before exposure. See Radiographic Quality → Practice questions →
Left Lateral Decubitus: Patient lies on the left side, horizontal CR. Demonstrates free fluid on the left or free air on the right. See Chest Radiography → Practice questions →
Line Focus Principle: The angled anode produces a small effective focal spot from a larger actual focal spot. Allows high tube loading with good resolution. See Radiographic Quality → Practice questions →
Lordotic Position: Patient leans back so the central ray is angled relative to the body. Demonstrates the apices free of the clavicles. See Chest Radiography → Practice questions →

M

Magnification Factor: SID / SOD. Larger MF = more magnification. Minimized by maximizing SID and minimizing OID. See Radiographic Quality → Practice questions →
mAs: Milliampere-seconds. Controls beam quantity (number of photons), and quantity changes in direct proportion to it. On film it controls density, but Bushong warns that rule does not hold for CR. See Radiographic Quality → Practice questions →
Maxillary Sinus: Largest paranasal sinus, located in the maxilla below the orbit. Best demonstrated on the Waters. See Skull, Facial Bones & Sinuses → Practice questions →
Mild Contrast Reaction: Warmth, flushing, metallic taste, coughing, nausea. Ehrlich and Coakes say these pass quickly and usually need no treatment, only observation. ACR says mild hives often need none either, though an antihistamine can be considered. See Contrast Media & Venipuncture → Practice questions →
Moiré Pattern: Interference pattern from interaction of grid lines with the digital sampling matrix. CR/DR artifact. See Digital Image Processing → Practice questions →
Motion Artifact: Blurred edges from patient or equipment motion during exposure. Reduced by short exposure time and immobilization. See Radiographic Quality → Practice questions →
Motion Blur: Image unsharpness from patient movement during exposure. Minimized by short exposure time and immobilization. See Radiographic Quality → Practice questions →
Myelography: Contrast study of the spinal subarachnoid space. Lumbar puncture usually at L3-L4, water-soluble iodinated contrast. See Urinary System & Contrast Studies → Practice questions →

N

Nasal Cannula: Low-flow oxygen delivery at up to 6 L/min. Ehrlich and Coakes give 24–45% oxygen at 1–6 L/min; AARC's 2002 guideline gives 24–40%, so use your question's source. The simplest and most frequently used device for longer-term oxygen. See Patient Monitoring → Practice questions →
Negligence: Neglect or omission of reasonable care or caution. A radiographer is held to the standard of care and skill of the profession. See Ethics, Law & Communication → Practice questions →
Non-Rebreather Mask: High-flow oxygen mask with reservoir bag and one-way valves. Sources differ: Ehrlich and Coakes say it can supply 100% used properly; AARC's 2002 guideline gives 60-80% at 10 L/min or more. Used in respiratory distress. See Patient Monitoring → Practice questions →

O

Occupational Dose Limit: NCRP-recommended 5 rem (50 mSv) per year whole body. Lifetime: 1 rem × age. See Radiation Protection → Practice questions →
Off-Center Grid Cutoff: Grid error where the central ray is not aligned with the grid centerline. Entire image is uniformly light. See Radiographic Quality → Practice questions →
Off-Focus Grid Cutoff: Edges light, from cutoff toward the edges of the image. Caused by SID outside the grid's specified focal range. See Radiographic Quality → Practice questions →
Off-Level Grid Cutoff: Grid not perpendicular to the central ray. Cutoff across the whole image, which reads light. See Radiographic Quality → Practice questions →
OML (Orbitomeatal Line): Cranial baseline from the outer canthus of the eye to the external acoustic meatus. Reference for most skull positioning. See Skull, Facial Bones & Sinuses → Practice questions →
Open-Mouth Odontoid: AP cervical projection with the mouth open. Demonstrates C1, C2, and the dens between the upper teeth and skull base. See Cervical & Thoracic Spine Positioning → Practice questions →

P

PA Chest: Posteroanterior chest projection. 72-inch SID, patient erect, scapulae cleared, full inspiration. The standard adult chest. See Chest Radiography → Practice questions →
Penumbra: Unsharp edges of objects in the image (Bontrager), which a small focal spot reduces but does not remove. Bushong calls this focal-spot blur. See Radiographic Quality → Practice questions →
Personal Dosimeter: TLD or OSL badge worn at collar level, outside the apron during fluoroscopy. Records cumulative occupational dose. See Radiation Protection → Practice questions →
Photoelectric Effect: Photon transfers all its energy to an inner-shell electron and is absorbed. Produces diagnostic contrast, bone vs. soft tissue. See Radiation Physics & Radiobiology → Practice questions →
Photostimulable Phosphor (PSP): Barium fluorohalide doped with europium. Traps electrons proportional to x-ray exposure. Read by laser scanner. See Digital Image Processing → Practice questions →
Pi Lines: Density lines repeating at 3.1416-inch intervals, one turn of a 1-inch roller, from dirt or a chemical stain on the roller (Bushong). A film-screen processor artifact. See Radiographic Quality → Practice questions →
Pneumothorax: Air in the pleural space. Best seen on upright expiratory PA or lateral decubitus with the affected side up. See Chest Radiography → Practice questions →
Position: How the body is placed on the table (supine, prone, recumbent, erect, decubitus). Distinct from projection. See Positioning Terminology → Practice questions →
Pott Fracture: The books differ. Bontrager: complete fracture of the distal fibula with major injury to the ankle joint, including ligament damage and frequent fracture of the distal tibia or medial malleolus. Merrill's: avulsion fracture of the medial malleolus with loss of the ankle mortise. Follow your program's or your question's source. See Foot, Ankle & Calcaneus Positioning → Practice questions →
Potter-Bucky Diaphragm: Oscillating grid that blurs lead strips during exposure. Makes the grid invisible on the final image. See Radiographic Quality → Practice questions →
Pregnant Radiographer Dosimetry: Second badge worn at waist level under the lead apron. Monitors embryo dose separately. See Radiation Protection → Practice questions →
Pregnant Radiographer Limit: 0.5 rem (5 mSv) total over the gestation, 0.05 rem (0.5 mSv) per month maximum. See Radiation Protection → Practice questions →
Projection: Path of the central ray through the body (AP, PA, lateral, oblique). Distinct from position. See Positioning Terminology → Practice questions →
Public Dose Limit: NCRP limit for the public: 1 mSv (0.1 rem) per year for continuous or frequent exposure, and 5 mSv (0.5 rem) for infrequent exposure. See Radiation Protection → Practice questions →
Pulsed Fluoroscopy: Intermittent rather than continuous beam, which shortens the overall exposure and lowers dose (Sherer). See Radiation Protection → Practice questions →
Pyelography: Imaging of the renal collecting system. Retrograde (catheter) or antegrade (percutaneous) approaches available. See Urinary System & Contrast Studies → Practice questions →

Q

Quantum Mottle: Grainy, noisy image from too few photons reaching the IR. Caused primarily by insufficient mAs (low photon fluence), often when a high-kVp / low-mAs technique is used. See Radiographic Quality → Practice questions →

R

RAO 40–70° UGI: Right anterior oblique 40–70° rotation during an upper GI series. Demonstrates the duodenal bulb in profile. See Esophagus, Stomach & Biliary → Practice questions →
RAO Sternum: Right anterior oblique 15–20° rotation. Throws the sternum off the spine and against the heart shadow. See Bony Thorax → Practice questions →
Reciprocity Test: Film-era check that exposures of equal mAs (different mA × time combinations) produce equal density. Bushong's QC table uses exposure linearity. See Equipment Operation & QA → Practice questions →
Recorded Detail: Sharpness of imaged structures. Improved by a small focal spot, minimal motion, small OID and long SID, plus good screen-film contact on film. See Radiographic Quality → Practice questions →
Rectification: Conversion of AC to DC. Half-wave uses one or more diodes and full-wave at least four. Three-phase and high-frequency are generator types that smooth the waveform further. See Equipment Operation & QA → Practice questions →
Repeat Exposure Rate: Share of images a department repeats, tracked as a QC metric. Bushong puts the film-era repeat rate from exposure factors alone at up to about 5%. Your department sets its own trigger for review. See Radiographic Quality → Practice questions →
Ripple: Variation in voltage during the AC cycle. Single-phase: 100%; three-phase six-pulse: about 14%; high-frequency: about 1%. See Equipment Operation & QA → Practice questions →

S

Sagittal Plane: Vertical plane that divides the body into left and right portions. Midsagittal divides into equal halves. See Positioning Terminology → Practice questions →
Salter-Harris Fracture: Pediatric fracture involving the epiphyseal plate. Classified Types I–V by the Salter-Harris system. See Trauma, Mobile & Surgical Radiography → Practice questions →
Scaphoid Fracture: Most frequently fractured carpal bone. Scaphoid views such as the modified Stecher or an angled CR with ulnar deviation show it better. See Hand, Wrist & Forearm Positioning → Practice questions →
Schueller Method: Axiolateral TMJ projection with CR 25–30° caudad, used for closed and open mouth comparison (Bontrager). Merrill's says this projection is sometimes called the modified Schüller method, and gives the Schüller name to the submentovertical cranial base projection, so check which one your source means. See Skull, Facial Bones & Sinuses → Practice questions →
Scotty Dog: Anatomic pattern on a 45° lumbar oblique where the pars interarticularis is the dog's neck. A 'collar' indicates spondylolysis. See Lumbar Spine, Sacrum & Coccyx → Practice questions →
Sensitometry: Film-era processor QC. A controlled film exposure measured for base+fog, mid-density, and contrast. See Equipment Operation & QA → Practice questions →
Settegast Method: Tangential projection of the patellofemoral joint with the knee flexed about 90 degrees and the beam tangential to the patella. Bontrager also applies sunrise/skyline to other tangential methods. See Knee, Leg & Patella → Practice questions →
Sievert (Sv): SI unit of equivalent or effective dose. 1 Sv = 100 rem. See Radiation Protection → Practice questions →
Six-Foot Rule: Sherer's mobile rule is at least 2 m (6.6 ft) from the patient, tube and useful beam, and at a right angle to the beam-scattering object line if possible. See Radiation Protection → Practice questions →
SMV (Submentovertical): Skull base projection. IOML parallel to IR, CR perpendicular. Demonstrates sphenoid sinuses and skull base. See Skull, Facial Bones & Sinuses → Practice questions →
Spatial Resolution: The ability to distinguish small adjacent objects. Measured in line pairs per millimeter (lp/mm). See Radiographic Quality → Practice questions →
Sphygmomanometer: Blood pressure cuff, used with a stethoscope to read systolic and diastolic pressure. See Patient Monitoring → Practice questions →
Spondylolysis: Defect in the pars interarticularis. Visible as a 'collar' on the Scotty Dog (lumbar oblique). See Lumbar Spine, Sacrum & Coccyx → Practice questions →
Stand-Pivot Transfer: Transfer for patients who can bear weight. Position the strong side next to the table, lead with the strong leg, and assist on the weak side. See Patient Transfer & Body Mechanics → Practice questions →
Standard Precautions: Treat every patient's blood, body fluids, secretions, and non-intact skin as potentially infectious. Applies to every patient, every time. See Infection Control → Practice questions →
Stecher Method: Scaphoid view. Stecher's method angles the IR 20 degrees with a perpendicular CR (Merrill's). Bontrager's modified Stecher elevates the hand 20 degrees with ulnar deviation. A 20-degree CR toward the elbow is a variation. See Hand, Wrist & Forearm Positioning → Practice questions →
Stenvers Method: Named petrous bone projection. Not found in Bontrager 9e or Merrill's 15e, and not on either ARRT outline, so check your program's text. See Skull, Facial Bones & Sinuses → Practice questions →
Step-Up Transformer: Transformer with more secondary turns than primary turns. Steps voltage up to kVp range. See Equipment Operation & QA → Practice questions →
Sterile Technique: Asepsis maintained for invasive procedures. The outer 1-inch border of the sterile field is treated as contaminated, and anything unsterile that touches the field contaminates it. See Infection Control → Practice questions →
Stochastic Effect: Probabilistic effect (cancer, genetic mutation). No threshold; probability increases with dose. See Radiation Physics & Radiobiology → Practice questions →

T

Thermionic Emission: Boiling of electrons from a heated filament. The first step in x-ray production. See Equipment Operation & QA → Practice questions →
Time, Distance, Shielding: The three cardinal rules of radiation protection. Apply all three to minimize occupational and patient dose. See Radiation Protection → Practice questions →
Timer Accuracy: Bushong's QC table: ±5% for exposure times over 10 ms and ±20% at 10 ms or less. The spinning top is the film-era test; TG-150 uses a meter. See Equipment Operation & QA → Practice questions →
Tort: A civil wrong for which the injured party may seek damages. Torts fall into intentional misconduct or negligence. A radiographer can also commit a criminal act. See Ethics, Law & Communication → Practice questions →
Towne Method: AP axial skull with CR 30° caudad to OML. Demonstrates occipital bone and dorsum sellae within foramen magnum. See Skull, Facial Bones & Sinuses → Practice questions →
Transverse Plane: Horizontal plane that divides the body into superior and inferior portions. Also called the axial or horizontal plane. See Positioning Terminology → Practice questions →
Trendelenburg Position: Patient supine with the head lower than the feet. Fluoroscopic tables can tilt the head down at least 15 degrees into this position. See Patient Monitoring → Practice questions →
Two-Factor Identification: Confirming patient identity using two independent identifiers (name + DOB) before every procedure. The Joint Commission standard. See Ethics, Law & Communication → Practice questions →

U

Upside-Down Grid: Center exposed, both edges light from severe cutoff. Always verify grid orientation arrows. See Radiographic Quality → Practice questions →

V

Vasovagal Syncope: Brief loss of consciousness when the vagus nerve's action widens blood vessels and slows the heart, so blood pressure falls. Can be brought on by fright, pain, or a contrast injection. See Patient Monitoring → Practice questions →
Venography: Contrast imaging of veins, part of angiography. See Urinary System & Contrast Studies → Practice questions →
Vital Signs: Temperature, pulse, respiration and blood pressure. Oxygen saturation is often recorded with them. Adult normals: 98.6°F, 60–100, 12–20, <120/80, and SpO2 95–100%. See Patient Monitoring → Practice questions →

W

Waters Method: Parietoacanthial projection. OML 37° to IR, CR perpendicular. Demonstrates maxillary sinuses. See Skull, Facial Bones & Sinuses → Practice questions →
Waters Sinus: Parietoacanthial projection. OML 37° to the IR. Demonstrates the maxillary sinuses without petrous ridge superimposition. See Skull, Facial Bones & Sinuses → Practice questions →
Window Level: Center pixel value of the displayed window, which controls brightness. Whether raising it darkens or brightens the image depends on the viewing software (Bontrager). See Digital Image Processing → Practice questions →
Window Width: Range of pixel values displayed as gray scale. Wide width = low contrast, long scale of grays. See Digital Image Processing → Practice questions →

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About this glossary

How many terms are tested on the ARRT Radiography Boards?

ARRT does not publish a term count, and the exam itself is secure, so any total is a guess and we will not give you one. What we can state precisely: this glossary defines 185 terms, each linked to a related chapter. Not every term is on the ARRT content outline. For example, Stenvers Method is on neither ARRT outline, IVU is absent from the 2027 outline, and Pi Lines is a film-screen artifact.

Should I memorize all the radiography terminology?

You don't need to memorize every term verbatim. You need to understand each one well enough to recognize it in a question stem and in the rationale. ARRT publishes content categories, not how often a term appears, so nobody can honestly rank terms as most tested. A sensible place to start is these families: positioning vocabulary (projection, position, angulation), fracture types (Colles, Boxer, Salter-Harris), legal terms (battery, negligence, malpractice, informed consent), photon interactions (photoelectric, Compton), and dose units (Gy, Sv, the SI units ARRT says are primary on the exam).

How is this glossary organized?

Alphabetically A through Z, with a link from each term to a related chapter. 185 terms, linked to 25 of the 28 chapters in the curriculum. Use Cmd-F or Ctrl-F to search the page for any term you encounter in a practice question.