ARRT Radiography flashcards

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

Normal adult heart rate

The typical resting heart rate for an adult is 60 to 100 beats per minute; below 60 is bradycardia and above 100 is tachycardia.

Nasal cannula oxygen flow

A nasal cannula delivers oxygen at 1 to 6 liters per minute, producing an inspired oxygen concentration of approximately 24% to 44%.

Sterile field border rule

The outer 1-inch (2.5 cm) border of a sterile drape is considered non-sterile, and any item touching it or held below table level is contaminated.

Airborne precautions requirements

Airborne precautions require a negative-pressure room with a closed door and an N95 respirator for staff, and are used for tuberculosis, measles, and varicella.

Contrast premedication schedule

A patient with a prior contrast reaction typically receives prednisone 50 mg by mouth at 13, 7, and 1 hour before, plus diphenhydramine 50 mg one hour before.

Extravasation first response

When contrast extravasates, stop the injection, disconnect the tubing, elevate the limb, apply a compress per policy, and document and monitor the site.

Fifteen percent rule

Increasing kVp by 15% doubles receptor exposure, so mAs is halved; decreasing kVp by 15% halves exposure, so mAs must be doubled.

Density maintenance formula

The relationship mAs1 divided by mAs2 equals (SID2 divided by SID1) squared keeps receptor exposure constant when the source-to-image distance changes.

Heat unit calculation

Heat units equal kVp times mA times seconds times a waveform factor of 1.0 for single-phase full-wave and high-frequency generators, and about 1.35 to 1.41 for three-phase.

Grid conversion factors

To maintain exposure when adding a grid, multiply mAs by 2 for 5:1, 3 for 6:1, 4 for 8:1, 5 for 12:1, and 6 for 16:1.

Anode heel effect

X-ray intensity is lower on the anode side of the beam, so the thicker portion of the anatomy should be placed toward the cathode side.

Magnification factor formula

Magnification equals source-to-image distance divided by source-to-object distance; increasing object-to-image distance or decreasing SID increases magnification and reduces detail.

Minimum total filtration

X-ray tubes operating above 70 kVp require at least 2.5 mm aluminum equivalent total filtration, while units limited to 70 kVp require 0.5 to 1.5 mm.

Deviation index formula

The deviation index equals ten times the base-ten logarithm of exposure index divided by target exposure index; values within plus or minus three are acceptable.

Quantum mottle cause

A grainy, mottled appearance results from too few x-ray photons reaching the receptor, usually from insufficient mAs, excessive filtration, or a high speed class.

Brightness versus receptor exposure

Brightness is the luminance displayed on a digital monitor and is adjusted at the workstation, unlike film density, which was controlled by the exposure reaching the film.

Subject contrast determinants

Subject contrast depends on the thickness, density, and atomic number of the tissues being imaged, along with kVp and the presence of contrast medium.

Rotation on PA chest

Equidistant clavicular heads and symmetric sternoclavicular joints indicate no rotation, while asymmetry between the two sides indicates patient rotation.

Spatial resolution definition

Spatial resolution is the ability to image small objects that have high subject contrast, improved by small focal spots, short object-to-image distance, and no motion.

Sternal angle landmark

The sternal angle, or angle of Louis, lies at the T4–T5 level at the carina and is used for centering thoracic spine and chest projections.

Iliac crest landmark

The iliac crest corresponds to the L4–L5 level, which is also approximately the level of the umbilicus and is used to center lumbar spine and abdominal studies.

Barium contraindication

Barium sulfate is contraindicated when bowel perforation or obstruction is suspected; a water-soluble iodinated agent such as Gastrografin is used instead.

PA chest positioning

The PA chest is performed at 72 inches SID with the patient upright, chin elevated, and shoulders rolled forward to move the scapulae off the lung fields.

Double-contrast barium enema

Barium plus air distends the colon and coats the mucosa so small polyps can be seen; it is contraindicated in toxic megacolon and suspected perforation.

Orbitomeatal line definition

The orbitomeatal line runs from the outer canthus of the eye to the external auditory meatus, and the infraorbitomeatal line runs from the infraorbital margin to the meatus.

Nonionic contrast advantage

Nonionic, low-osmolar iodinated contrast produces fewer osmolality-related side effects and less chemotoxicity than ionic agents, but it costs more.

Occupational dose limit

The annual effective dose limit for radiation workers is 50 mSv (5 rem), with a lens-of-eye limit of 150 mSv and a skin and extremity limit of 500 mSv.

Public dose limit

The annual effective dose limit for the general public is 1 mSv (0.1 rem), and the limit for an embryo-fetus of a declared pregnant worker is 0.5 mSv per month.

ALARA principle

ALARA means keeping exposures as low as reasonably achievable, balancing every dose reduction measure against the image quality required for an accurate diagnosis.

Inverse square law distance

Radiation intensity is inversely proportional to the square of the distance from the source, so doubling the distance reduces the dose rate to one quarter.

Dosimeter placement

A whole-body personnel dosimeter is worn at collar level outside the lead apron, and a second badge may be worn beneath the apron to estimate dose to shielded tissues.

Fluoroscopy cumulative timer

Fluoroscopic equipment must signal the operator after 5 minutes of cumulative fluoroscopic exposure during a procedure so that dose can be assessed and limited.