ARRT Procedures and Positioning Study Guide

Procedures is the largest category on the exam: 66 of the 200 scored questions — a full third. It breaks into Extremity (28 questions), Thorax and Abdomen (20), and Head, Spine and Pelvis (18).

Extremity being the single biggest block is worth sitting with for a second. Fingers, hands, wrists, elbows, shoulders, knees, ankles, and feet carry more questions than the entire skull, spine, and pelvis group combined. If positioning is the thing you planned to review last, the arithmetic is against you.

The one skill that carries this whole category

Most positioning questions can be answered without recall if you can decode the projection's name. The first word is where the beam enters; the second is where it exits — and the exit side is the side against the image receptor.

• Mediolateral enters medially, exits laterally, so the lateral surface is against the IR. The routine lateral ankle and lateral calcaneus are mediolateral projections — lateral side down. Lateromedial is the reverse.
• AP puts the posterior/dorsal surface against the IR. PA puts the anterior/palmar surface against the IR. So a routine PA hand has the palm against the receptor — and the Robert-method thumb, taken with the dorsal surface down, is an AP, not a PA.

Learn to run that decode deliberately, every time, instead of reaching for a memory of what the image looked like. It converts a large class of questions from recall into reasoning — and it's the defense against the single most common way students get positioning questions wrong.

The laterality rules that invert (read this twice)

Here is where points quietly disappear. Oblique projections demonstrate structures on one side, and which side depends on the region — and cervical and lumbar work in opposite directions.

Cervical intervertebral foramina — posterior obliques show the side FARTHEST from the IR. With RPO/LPO and the CR angled 15–20° cephalad, you see the foramina on the up side. So an LPO demonstrates the RIGHT cervical foramina. Anterior obliques (RAO/LAO) with the CR caudad show the foramina closest to the IR.

Lumbar zygapophyseal (apophyseal) joints — obliques show the side CLOSEST to the IR. At about 45°, you get the "Scottie dog," and the joints demonstrated are on the down side. So an LPO demonstrates the LEFT lumbar joints.

Those two are opposite. Same oblique, same patient, different answer depending on whether the stem says cervical or lumbar. Write both sentences out until the pair stops feeling arbitrary:

Sacroiliac joints follow the cervical pattern, not the lumbar one. The AP (posterior) oblique demonstrates the joint on the side up and away from the IR — so RPO shows the left SI joint and LPO shows the right. Said the practical way: the side of interest is elevated. Rotation is 25–30°.

Colon flexures on a contrast enema: the flexure on the elevated side opens. RAO and LPO open the right (hepatic) flexure; LAO and RPO open the left (splenic).

Decubitus positions: free air rises to the non-dependent (up) side. A left lateral decubitus demonstrates free intraperitoneal air over the right (up) lateral liver margin. And air-fluid levels require a horizontal beam — which is the reason the decubitus exists at all.

Central-ray angles worth knowing cold

These are arbitrary and heavily tested, so they're flashcard material:

The AP knee has a rule rather than a number, measured by ASIS-to-tabletop distance: under 19 cm, angle 5° caudad; 19–24 cm, 0°; over 24 cm, 5° cephalad. Questions give you the measurement and expect the direction.

Note the pattern in sacrum versus coccyx — cephalad for one, caudad for the other. Nearly every angle on this list has a neighbor that goes the other way, which is exactly why they get mixed up under time pressure.

What each region actually covers

Extremity (28) — the upper limb from fingers through the shoulder girdle (including scapula, clavicle, and AC joints), the lower limb from toes through the femur, plus long-bone measurement, bone age, bone surveys, and arthrography.

Thorax and Abdomen (20) — chest, ribs, sternum, soft-tissue neck, and sternoclavicular joints; then the abdomen and the GI studies (esophagus, upper GI, small bowel, contrast enema, and the biliary studies); then the GU studies, including intravenous urography, cystography, and hysterosalpingography. The contrast studies are a big share of this block, and they're commonly under-studied relative to plain-film chest and abdomen.

Head, Spine and Pelvis (18) — skull, facial bones, mandible, TMJ, nasal bones, orbits, and paranasal sinuses; the full spine including scoliosis series and myelography; and the SI joints, pelvis, and hip.

How to study this category

Work one projection at a time, with a fixed checklist. For each: body position, part position, central ray (direction and entry/exit point), SID and receptor, and the evaluation criteria that prove you got it right. Positioning knowledge that's organized as a repeatable checklist survives exam pressure; positioning knowledge organized as "I've seen this image" does not.

Study the evaluation criteria, not just the setup. A large share of questions describe an image — "the sternal ends of the clavicles are not symmetric" — and ask what went wrong or what to change. That's the criteria talking, and it's the same information from the other direction.

Interleave regions deliberately. Thirty elbow questions in a row feels productive and hides the actual exam skill, which is recognizing which projection a scenario is describing when they arrive mixed. Mix upper limb with spine with contrast studies in the same session.

Drill the invertible pairs as pairs. Cervical against lumbar obliques. Sacrum against coccyx. Mediolateral against lateromedial. AP against PA hand. Studying either one alone leaves you able to recall a rule without knowing which of the two you're recalling.

The one-paragraph version

Procedures is 66 questions — a third of the exam — weighted toward Extremity (28), then Thorax and Abdomen (20), then Head, Spine and Pelvis (18). The highest-leverage skill is decoding projection names: first word is beam entry, second is exit, and the exit side lies against the receptor, so mediolateral means lateral-side-down and a PA hand means palm-down. Then learn the laterality rules as pairs, because cervical and lumbar invert: posterior obliques show the cervical foramina farthest from the IR but the lumbar joints closest to it, so an LPO gives you right cervical foramina and left lumbar joints. SI joints follow the cervical pattern with the side of interest elevated; contrast-enema flexures open on the elevated side; free air rises to the up side on a decubitus. Memorize the central-ray angles cold, study evaluation criteria alongside setup, and interleave regions rather than blocking them.

Question counts reflect the ARRT Radiography examination content specifications. Positioning conventions and central-ray angles verified against Bontrager & Lampignano.

Keep going: The exam structure article shows how all four categories are weighted, and the 6-week study plan puts this category where its size says it belongs.