Quick Answers
Straight answers to the ARRT® Radiography questions students search most.
Each answer lists the sources it was checked against, such as regulations, ARRT documents and CDC guidance.
Need the long version? See the Blog for prep guides and strategy. Need the full curriculum? Start at Learn.
Patient Care
2 answers
Adult vs Pediatric Vital Signs: Normal Values by Age
Adult pulse is 60 to 100 and respiration 12 to 20. A newborn averages about 125 beats/min. If a patient arrests, call the code and start CPR.
Quick answerGeriatric Patient Definition (ARRT): 65 and Impaired
ARRT's competency list defines a geriatric patient as at least 65 and impaired by aging. Under 65 doesn't qualify, but any impaired patient needs care.
Safety
7 answers
Do Grids Reduce Patient Dose? No, They Raise It
Grids raise patient dose because technique must rise to keep the receptor signal. Bushong's average factors: 5:1 = 2, 8:1 = 4, 12:1 = 5, 16:1 = 6.
Quick answerTwo-Dosimeter Formula: 1.5 Waist + 0.04 Collar (NCRP 122)
NRC Regulatory Guide 8.40 credits NCRP 122 with the formula 1.5 x waist + 0.04 x collar. It estimates effective dose equivalent. ARRT lists no formula.
Quick answerIs a Thyroid Shield Required for Fluoroscopy?
No federal rule we read requires a thyroid shield in fluoroscopy. Your state or facility may. Sherer and Bontrager disagree on whether it is required.
Quick answerMost Common Cause of Repeat Exposures: Positioning Errors
Positioning leads rejected digital radiographs in published audits, at 49% to 79% where it is reported alone. Motion and exposure sit far behind.
Quick answerLead Apron Attenuation: What the Numbers Really Say
Bushong lists 88% at 75 kVp and 75% at 100 kVp for a 0.5 mm Pb apron. A 2018 study measured about 97% at 100 kVp. No federal rule we read sets a minimum.
Quick answerSkin Erythema Threshold Doses: 2 Gy Early, 3 to 6 Gy Main
Early transient erythema starts near 2 Gy within hours. Main erythema is listed at 6 Gy after about 10 days, though CDC lists about 3 Gy. Sources vary.
Quick answerX-Ray Production Efficiency: About 99% Heat, 1% X-Rays
Bushong says more than 99% of electron energy becomes heat and about 1% becomes x-rays at 100 kVp. No radiography textbook we hold gives 99.8% and 0.2%.
Image Production
13 answers
Which AEC Cell for a PA Chest? The Two Outside Cells
With the lungs of interest, Bushong says use the two outside AEC cells. By our reasoning, a center cell behind the mediastinum runs the exposure longer.
Quick answerFilm vs Digital Spatial Resolution: Screen-Film Resolves More
Bushong lists screen-film at 8 to 15 lp/mm. Bontrager lists general digital at 2.5 to 5 lp/mm. Film is off both outlines, so learn what limits digital.
Quick answerCan Window Level Reveal Hidden Detail? Only What Was Recorded
Window and level can show recorded detail you couldn't see at first. They can't recover noise-buried or clipped detail, or lower the dose.
Quick answerHigh-Frequency Heat Unit Multiplier: 1.4 in Bushong, Not 1.45
Bushong's high-frequency heat unit multiplier is 1.4, the same as three-phase. Single phase uses 1.0. See the formula, worked numbers and other values.
Quick answerInherent vs Added Filtration: What Counts as Which
Inherent filtration is built into the tube, about 0.5 mm Al. Added is the aluminum sheet and, in Bushong, the collimator mirror. Total: usually 2.5 mm.
Quick answerPediatric AEC Errors: Both Under and Overexposure Can Happen
AEC on a child can fail either way. ACR-AAPM says partial cell coverage can cut the exposure short. By our reasoning, a missed cell may overexpose.
Quick answerIs Breathing Voluntary or Involuntary Motion in Radiography?
Bontrager's and Merrill's class breathing as voluntary motion. Bushong groups lung motion with involuntary motion. Sources conflict, so learn the reasoning.
Quick answermAs vs kVp: What Each One Controls
mAs changes beam quantity only. kVp changes quantity and quality. A 15% kVp rise roughly doubles receptor exposure, so you can halve mAs.
Quick answerPhilips EI vs Siemens EXI: Exposure Index by Vendor
Older Philips EI falls as exposure rises. Siemens EXI rises with it. See vendor scales, the IEC EI and how to read the deviation index.
Quick answerHow to Read a Tube Rating Chart: kVp, Time and mA Curves
On a radiographic rating chart, kVp is on the vertical axis, maximum exposure time is horizontal, and each curve is one mA. Below the curve is safe.
Quick answerTungsten Melting Point: 3410°C in Bushong, Up to 3422°C Elsewhere
Bushong prints tungsten's melting point as 3410°C and 3400°C, and other references give up to 3422°C. Papers call it the highest of any metal.
Quick answerWindow Level Direction: Does Higher Level Mean Brighter or Darker?
Bontrager says a higher window level darkens the image in some PACS and brightens it in others. No textbook we opened sets one direction, so check yours.
Quick answerWhat Causes X-Ray Filament Burnout? Tungsten Vaporization
Filament burnout happens when tungsten vaporizes off the hot filament until the wire breaks. The same tungsten coats the enclosure and can cause arcing.
Procedures
6 answers
Is the Ankle a Hinge or Saddle Joint? Sources Disagree
Merrill's says the ankle is a hinge joint and Bontrager's 9th edition says saddle. StatPearls also says hinge. What that means for your prep.
Quick answerAxiolateral Hip (Danelius-Miller): CR Enters the Groin
In the Danelius-Miller axiolateral hip, the CR enters the groin perpendicular to the femoral neck. The IR stands at the outer hip, parallel to the neck.
Quick answerAP Pelvis CR Centering: Midway Between ASIS and Symphysis
For an AP pelvis, the CR is perpendicular and midway between the ASIS level and pubic symphysis, about 5 cm (2 in) below the ASIS on an average adult.
Quick answerSmallest Facial Bone: The Lacrimal Bones
The lacrimal bones are the smallest facial bones, according to Merrill's Atlas. Each is about the size of a fingernail and sits in the medial orbital wall.
Quick answerSternal Angle Vertebral Level: The T4-T5 Disk Space
The sternal angle lies at the T4-T5 disk space on an average adult, about 5 cm (2 in) below the jugular notch, where the second costal cartilage attaches.
Quick answerSphenoid Sinus Projection: SMV, and the 2027 Change
Both textbooks describe an SMV for the sphenoid sinus, but it leaves ARRT's sinus list on March 1, 2027. The lateral also shows the sphenoid.
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