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ARRT Radiography Cheat Sheet

Practice this exam

Patient Care

  • 16-17% of exam
  • Vitals & Assessment Contrast Media Infection & Emergencies Contrast Picker

Safety

  • 25% of exam
  • Radiation Units NCRP Dose Limits Protection & ALARA Radiobiology & Fluoro

Image Production

  • 25-26% of exam
  • Exposure Factors Image Quality Digital Imaging QC & Artifacts Exposure Fix Picker

Procedures

  • 33% of exam
  • Chest & Thorax Spine & Skull Extremities & Pelvis Abdomen & Contrast Projection Picker

Quick Facts

  • Exam ARRT Radiography
  • Scored 200 (+30 pilot)
  • Time 230 min
  • Pass Scaled 75
  • Fee $225
  • Format Mostly MCQ (Pearson VUE)
  • Domains 4 categories
  • Blueprint Jan 2022

Barium vs Water-Soluble PA

Barium

  • Intact GI tract
  • Better coating
  • Not if perforation

Water-soluble

  • Suspected perforation
  • Iodinated, absorbable
  • Safe in peritoneum
  • Intact vs perforation

Contrast Picker PA

  • Suspected GI perforation → Water-soluble iodinated
  • Impaired renal function → Check eGFR, hydrate
  • Prior contrast reaction → Premedicate steroids
  • Joint evaluation → Arthrography, iodinated
  • Uterus and tubes → Hysterosalpingography

Vitals & Assessment PA

  • Pulse 60-100 bpm adult
  • Respirations 12-20 per minute
  • SpO2 95-100% normal
  • Hypoxemia Below 90% SpO2
  • Blood pressure About 120/80 mmHg
  • Nasal cannula 1-6 L/min low-flow

Contrast Media PA

  • LOCM Nonionic, fewer reactions
  • HOCM Ionic, more reactions
  • Barium Intact GI tract only
  • Water-soluble If perforation suspected
  • eGFR/creatinine Screen before iodinated
  • Shellfish myth Not a contraindication

Infection & Emergencies PA

  • Hand hygiene Most effective control
  • Airborne N95 + negative-pressure room
  • Droplet Surgical mask, close range
  • Contact Gown and gloves
  • PPE order Gown, mask, goggles, gloves
  • Epinephrine First for anaphylaxis
  • Vasovagal Supine, legs elevated

Cardinal Rules SA

  • Time - Distance - Shielding
  • Time: less beam-on Distance: inverse square Shielding: lead barrier Distance is most effective

Gray vs Sievert SA

Gray (Gy)

  • Absorbed dose
  • Energy per kg
  • Tissue dose

Sievert (Sv)

  • Equivalent dose
  • Weighted by risk
  • Stochastic reporting
  • Absorbed vs biological

Radiation Units SA

  • Gray Absorbed dose Gy
  • Sievert Equivalent/effective dose Sv
  • Roentgen Exposure (traditional unit; SI = C/kg)
  • Becquerel One disintegration per second
  • Coulomb/kg SI exposure unit
  • LET / RBE Biological damage factors

Dose Limits SA

  • Whole 50, Lens 150, Skin 500
  • 50 mSv: whole body 150 mSv: eye lens 500 mSv: skin/extremities 1 mSv: public

NCRP Dose Limits SA

  • Occupational 50 mSv per year
  • Cumulative 10 mSv times age
  • Public 1 mSv per year
  • Fetus 5 mSv over gestation
  • Monthly fetus 0.5 mSv after declaration
  • Lens of eye 150 mSv per year
  • Skin/extremities 500 mSv per year

Protection & ALARA SA

  • ALARA As Low As Reasonably Achievable
  • Cardinal rules Time, distance, shielding
  • Inverse square Double distance, quarter dose
  • Filtration 2.5 mm Al above 70kVp
  • Collimation Less scatter, lower dose
  • Protective apron 0.25-0.5 mm Pb equivalent
  • Distance Most effective protection

Radiobiology & Fluoro SA

  • Stochastic No threshold, probability
  • Deterministic Threshold, tissue reactions
  • Bremsstrahlung Braking radiation
  • Characteristic Shell-transition x-rays
  • Photoelectric Absorption, more contrast
  • Compton Scatter, patient dose
  • Last-image hold Freezes frame, cuts dose

15% kVp Rule IM

  • +15% kVp = double exposure
  • +15% kVp: 2x exposure Halve mAs to hold Lower dose, lower contrast

mAs vs kVp IM

mAs

  • Receptor exposure
  • Density/brightness
  • Directly proportional

kVp

  • Beam penetration
  • Contrast scale
  • More scatter
  • Exposure vs contrast

Exposure Fix Picker IM

  • Quantum mottle noise → Increase mAs ( More photons )
  • Low contrast, scatter fog → Add grid, collimate
  • Need lower patient dose → +15% kVp, halve mAs
  • Motion blur → Shorter exposure time
  • Too much magnification → Raise SID, reduce OID
  • Overexposed, high DI → Reduce mAs

Exposure Factors IM

  • mAs Controls receptor exposure
  • kVp Controls penetration/contrast
  • 15% rule +15% kVp doubles exposure
  • SID Affects exposure and magnification
  • OID Increases magnification, air gap
  • AEC Auto-terminates exposure
  • Focal spot Small = better detail

EI vs DI IM

EI

  • Receptor exposure
  • Detector-specific
  • Technique feedback

DI

  • Deviation from target
  • Zero is ideal
  • +3 ≈ 2× target receptor exposure
  • Amount vs deviation

Image Quality IM

  • Contrast Density difference (kVp)
  • Spatial resolution Recorded detail/sharpness
  • Distortion Size or shape misrepresentation
  • Magnification Enlarged by OID
  • Quantum mottle Noise from low mAs
  • SNR Signal-to-noise ratio

Window Width vs Level IM

Window width

  • Displayed contrast
  • Gray range shown
  • Post-processing only

Window level

  • Displayed brightness
  • Midpoint value
  • Post-processing only
  • Contrast vs brightness

Digital Imaging IM

  • EI Receptor exposure indicator
  • DI Deviation from target (0 ideal)
  • Dose creep DI +3 ≈ 2× receptor exposure
  • DQE Efficiency of signal capture
  • Direct DR a-Se converts to charge
  • Indirect DR Scintillator makes light first

QC & Artifacts IM

  • Window width Displayed contrast
  • Window level Displayed brightness
  • kVp accuracy Within about 5%
  • Reproducibility Output varies under 5%
  • Flat-field Corrects dead pixels
  • Grid cutoff Primary-beam absorption loss
  • Moire CR grid-line aliasing

Oblique Spine (posterior obliques) PR

  • Posterior obliques: Cervical up, Lumbar down
  • Cervical RPO/LPO foramina: farthest (up) Lumbar RPO/LPO zygapophyseal: nearest (down) Scotty dog = lumbar

Fluid vs Air Decubitus PR

Fluid (effusion)

  • Affected side down
  • Fluid layers dependent
  • Horizontal beam

Air (pneumothorax)

  • Affected side up
  • Air rises nondependent
  • Horizontal beam
  • Fluid down, air up

Projection Picker PR

  • Suspect pleural effusion → Lateral decub, side down ( Fluid layers dependent )
  • Suspect pneumothorax → Lateral decub, side up ( Air rises nondependent )
  • Free air, cannot stand → Left lateral decubitus ( Air over liver )
  • Lung apices clear → AP lordotic (Lindblom)
  • Scaphoid detail → Stecher, ulnar deviation
  • Carpal tunnel → Gaynor-Hart
  • Open glenohumeral joint → Grashey method
  • Suspected hip fracture → Danelius-Miller lateral

Chest & Thorax PR

  • PA chest SID 72 inches (180 cm)
  • CR centering T7, inferior scapular angle
  • Full inspiration 10 posterior ribs
  • Fluid decub Affected side down
  • Air decub Affected side up
  • AP lordotic Apices free of clavicles
  • SC joints PA or shallow oblique

Decubitus Rule PR

  • Fluid down, Air up
  • Effusion: affected side down Pneumothorax: affected side up

Frog-leg vs Danelius-Miller PR

Frog-leg (Cleaves)

  • Routine lateral hip
  • Requires abduction
  • Not for fracture

Danelius-Miller

  • Trauma lateral hip
  • Horizontal beam
  • No limb movement
  • Routine vs trauma

Abdomen & Contrast PR

  • KUB centering Iliac crests
  • Upright abdomen 2 inches above crests
  • Free air Left lateral decubitus
  • Erect wait 5 minutes before exposure
  • Esophagram/UGI RAO position
  • Small bowel Images 15-30 minutes
  • IVU centering Iliac crests

Spine & Skull PR

  • Open-mouth Dens, C1-C2
  • Cervical posterior oblique Foramina farthest (upside)
  • Lumbar posterior oblique Zygapophyseal joints (Scotty dog)
  • Lateral lumbar Centered at L4
  • Towne 30 caudad, occipital bone
  • Waters Maxillary sinuses, orbital floors
  • Caldwell 15 caudad, frontal sinuses

Extremities & Pelvis PR

  • PA oblique hand 45 external rotation
  • Stecher Scaphoid, ulnar deviation
  • Gaynor-Hart Carpal canal/tunnel
  • Lateral elbow 90 degrees flexion
  • Grashey Open glenohumeral joint
  • AP mortise ankle 15-20 internal rotation
  • Calcaneus axial 40 cephalad angle
  • AP pelvis 15-20 internal rotation

Trauma / Mobile / OR PR

  • Trauma C-spine Cross-table lateral first
  • Must include C7-T1 visualized
  • Trauma rule CR perpendicular, 2 projections 90
  • Mobile chest Upright as tolerated
  • C-arm Tube under table
  • Markers In field, at exposure

Common Traps

Gray vs Sievert

  • Gray = absorbed dose ≠ Sievert = equivalent dose

mAs vs kVp

  • mAs = exposure ≠ kVp = contrast

Shellfish myth

  • Shellfish allergy irrelevant ≠ Prior reaction matters

Barium danger

  • Barium if intact ≠ Water-soluble if perforation

Decub direction

  • Fluid: side down ≠ Air: side up

EI is not dose

  • EI = receptor exposure ≠ Not patient dose

Distance beats shielding

  • Distance most effective ≠ Shielding not first

Last Minute

  • 1. Procedures 33%, biggest domain
  • 2. Pass = scaled score 75
  • 3. 200 scored, 30 pilot
  • 4. 230 minutes total test time
  • 5. PA chest = 72-inch SID
  • 6. Distance beats time and shielding
  • 7. Occupational limit 50 mSv yearly
  • 8. mAs = exposure; kVp = contrast
  • 9. Perforation = water-soluble contrast
  • 10. Fluid decub down, air up
  • 11. Epinephrine first for anaphylaxis
  • 12. Gray = absorbed; Sievert = equivalent