ARRT RRA cheat sheet

Normal adult vital signs: respiratory rate 12-20/min, pulse 60-100 bpm, blood pressure ~120/80 mmHg, oral temperature 36.1-37.5 C (97-99.5 F), SpO2 95-100%.

Hypotension with tachycardia and narrowed pulse pressure suggests hypovolemia or shock and warrants stopping the study and notifying the radiologist.

Universal/standard precautions apply to all patients: gloves for contact with blood, body fluids, mucous membranes, and nonintact skin; hand hygiene before and after every patient contact.

Contrast reaction classification: mild (flushing, pruritus, hives), moderate (vomiting, urticaria, bronchospasm), severe (laryngeal edema, hypotension, anaphylaxis requiring epinephrine).

Extravasation management: stop injection, remove cannula, elevate the limb, apply cold compress for most agents, document volume and site, and monitor for compartment syndrome.

Gadolinium is contraindicated in patients with eGFR < 30 mL/min/1.73 m2 or on dialysis because of nephrogenic systemic fibrosis risk.

Metformin: hold for 48 hours after iodinated contrast in patients with reduced renal function or AKI; resume only after renal function is confirmed stable.

Airborne precautions (negative-pressure room, N95 respirator) for tuberculosis, varicella, and measles; droplet precautions for influenza, pertussis, and meningococcal disease.

SID and magnification: increasing SID reduces magnification and increases recorded detail; magnification factor = SID / SOD (source-to-object distance).

Grid selection: grid ratio typically 5:1 for <70 kVp, 8:1 for 70-90 kVp, 10:1 to 12:1 for >90 kVp; grid cutoff appears as progressive density loss toward the periphery.

mAs controls receptor exposure (density) and is the primary control of image noise; kVp controls subject contrast and penetrability; the 15% rule states a 15% kVp increase doubles receptor exposure.

mA x seconds = mAs; exposure time must be short enough to minimize motion, with minimum response times often 1-100 ms for modern AEC systems.

Automatic exposure control: select the correct ionization chamber, center the anatomy over the chamber, and set backup time as a safety limit against overexposure.

Fluoroscopy: keep table-to-image-intensifier distance minimal, use pulsed fluoroscopy and last-image hold, and limit dose using the ALARA principle; typical dose limit for a procedure is governed by the facility's reference levels.

Contrast media osmolality: low-osmolar nonionic agents are preferred for intravenous use; high-osmolar ionic agents carry higher risk of pain, nausea, and renal effects.

Venipuncture: select a large antecubital vein, use a 20-22 gauge cannula for power injection, check for blood return, and confirm patency with a saline flush before contrast.

Primary image quality factors: receptor exposure, contrast, spatial resolution (recorded detail), and distortion; distortion has size (magnification) and shape (elongation/foreshortening) components.

Quantum mottle (noise) is inversely related to the number of photons reaching the receptor; doubling mAs reduces quantum noise by approximately the square root of 2.

Spatial resolution is improved by smaller focal spot, shorter object-to-image-receptor distance, longer SID, and smaller pixel size; line pairs per millimeter quantify resolution.

AEC density errors: underexposure produces a light image with visible noise; overexposure produces a dark image and increased patient dose without added diagnostic value.

Histogram analysis in digital radiography: the useful signal should occupy the middle of the histogram; a histogram shifted left indicates underexposure, shifted right indicates overexposure.

Contrast resolution is the ability to distinguish tissues of similar attenuation; it improves with higher detector bit depth and lower noise.

Anode heel effect: the cathode side of the beam has greater intensity; place the thicker anatomy toward the cathode side to equalize receptor exposure.

Motion artifact appears as blur or ghosting; it is minimized by short exposure time, patient instruction, and immobilization devices.