Positioning is the skill that turns a radiography student into a confident technologist. This guide covers the key terms, the general principles and the routine projections for the most common exams, with central ray centering and what a good image should show. Use it as a quick reference alongside your textbook and your program’s protocols.
[TU EXPERIENCIA: 2–3 sentences on how you learned positioning and one tip you give students, noting that you trained and work in Spain.]
Key takeaways
- Learn the terminology first: projection, position and view mean different things.
- Most exams need at least two projections at 90 degrees to each other.
- Always center to the right landmark, include the required anatomy and collimate closely.
- Department routines and angles vary, so always follow your program and facility protocols.
Positioning terms you need to know
| Term | Meaning |
|---|---|
| Projection | The path of the central ray, for example AP (anteroposterior) or PA (posteroanterior) |
| Position | How the patient’s body is placed, for example supine, prone, upright or lateral |
| View | How the image looks from the receptor’s perspective. Often used loosely; prefer «projection» |
| AP / PA | Central ray enters the front and exits the back (AP), or the reverse (PA) |
| Lateral | Side view. Named for the side closest to the image receptor (left lateral, right lateral) |
| Oblique | Body rotated so it’s neither AP/PA nor lateral, for example a 45-degree oblique |
| Decubitus | Patient lying down, with a horizontal beam |
| Axial | Central ray angled along the long axis of the body or part |
| Cephalad / caudad | Angled toward the head / toward the feet |
| SID | Source-to-image distance, commonly 40 inches (102 cm) or 72 inches (183 cm) |
General principles
- Two projections at 90 degrees. Many exams need an AP or PA plus a lateral to show the anatomy in three dimensions.
- Include the joints. Long bones usually need both joints included.
- Center, then collimate. Center the central ray to the correct landmark and collimate to the area of interest.
- Use markers. Place a right or left marker in the collimated field on every image.
- Reduce motion. Give clear breathing instructions and use immobilization when needed.
- Protect and communicate. Explain the exam, check identity and pregnancy status as required and follow ALARA.
Routine projections by body region
These are common routine projections. Your department may add or change projections.
Chest
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| PA (upright, 72 in SID) | Perpendicular, to the level of about T7 | At least 10 posterior ribs above the diaphragm, no rotation, scapulae moved out of the lung fields |
| Left lateral | Perpendicular, to about T7 at the midcoronal plane | Both lungs from apices to costophrenic angles, arms raised out of the field |
Take both on full inspiration, usually the second breath.
Abdomen
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| AP supine (KUB) | Perpendicular, at the level of the iliac crests, midsagittal | From the kidneys to the symphysis pubis, taken on expiration |
| AP upright | Perpendicular, about 2 in above the iliac crests | Includes the diaphragm, to show free air or air-fluid levels |
Hand and wrist
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| PA hand | Perpendicular, to the 3rd MCP joint | All digits and carpals; fingers separated |
| PA oblique hand (about 45 degrees) | Perpendicular, to the 3rd MCP joint | Mid-shafts of the 3rd to 5th metacarpals without overlap |
| Lateral hand | Perpendicular, to the 2nd MCP joint | Metacarpals superimposed; fan lateral to show the fingers |
| PA wrist | Perpendicular, to the midcarpal area | Distal radius and ulna, carpals, proximal metacarpals |
| PA wrist, ulnar deviation (scaphoid) | Angled about 10 to 15 degrees toward the elbow, to the scaphoid | Scaphoid without foreshortening |
Elbow and shoulder
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| AP elbow | Perpendicular, to the mid-elbow joint | Fully extended elbow, epicondyles parallel to the receptor |
| Lateral elbow | Perpendicular, to the mid-elbow joint, elbow flexed 90 degrees | Humeral epicondyles superimposed |
| AP shoulder (external and internal rotation) | Perpendicular, to about 1 in inferior to the coracoid process | Greater tubercle in profile (external) or lesser tubercle in profile (internal) |
Foot, ankle and knee
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| AP foot | About 10 degrees toward the heel, to the base of the 3rd metatarsal | Tarsals anterior to the talus, metatarsals and phalanges |
| Medial oblique foot (30 to 40 degrees) | Perpendicular, to the base of the 3rd metatarsal | Tarsal bones and metatarsal bases with less overlap |
| Lateral foot | Perpendicular, to the base of the 3rd metatarsal (medial cuneiform area) | Superimposed metatarsals, ankle joint included |
| AP ankle | Perpendicular, midway between the malleoli | Distal tibia and fibula, talus |
| AP mortise ankle | Perpendicular, leg rotated about 15 to 20 degrees medially | Open ankle mortise all around |
| Lateral ankle | Perpendicular, to the medial malleolus | Fibula over the posterior tibia, base of the 5th metatarsal included |
| AP knee | Angle depends on the patient’s body size (often 0 to 5 degrees), to about 1/2 in distal to the patellar apex | Open joint space, no rotation |
| Lateral knee | About 5 to 7 degrees cephalad, to about 1 in distal to the medial epicondyle, knee flexed 20 to 30 degrees | Femoral condyles superimposed, patellofemoral joint open |
Pelvis and hip
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| AP pelvis | Perpendicular, midway between the level of the ASIS and the symphysis pubis, legs rotated internally 15 to 20 degrees | Both hips and the whole pelvis, femoral necks in profile, no rotation |
| AP hip | Perpendicular, to the femoral neck | Hip joint and proximal femur, femoral neck in profile |
Don’t rotate the legs if a hip fracture is suspected. Follow your department’s trauma protocol.
Spine
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| AP axial cervical | 15 to 20 degrees cephalad, to about C4 | C3 to T2 with open intervertebral spaces |
| AP open-mouth (odontoid) | Perpendicular, through the open mouth | Dens and C1 to C2 without teeth or skull superimposed |
| Lateral cervical (72 in SID) | Perpendicular, to about C4 | All seven cervical vertebrae, shoulders depressed |
| AP lumbar | Perpendicular, at the level of the iliac crests, knees flexed | Lumbar vertebrae and sacroiliac joints, spinous processes centered |
| Lateral lumbar | Perpendicular, at the level of the iliac crests (about L4) | Lumbar bodies and intervertebral foramina |
| Oblique lumbar (45 degrees) | Perpendicular, to about L3 | Zygapophyseal joints («Scottie dog») |
Skull
| Projection | Central ray and centering | Good image shows |
|---|---|---|
| PA axial (Caldwell) | 15 degrees caudad to the OML, exiting at the nasion | Petrous ridges in the lower third of the orbits |
| AP axial (Towne) | 30 degrees caudad to the OML (37 degrees to the IOML) | Occipital bone, dorsum sellae within the foramen magnum |
| Lateral | Perpendicular, about 2 in superior to the EAM | Superimposed orbital roofs and mandibular rami |
How to evaluate your images
Ask yourself:
- Is all the required anatomy included?
- Is the position correct, with no unwanted rotation?
- Is the central ray centered and the field collimated?
- Is the right or left marker visible and correct?
- Is the exposure appropriate (check the exposure indicator)?
- Is there any motion or artifact?
If the answer to any of these is no, decide with your supervisor whether a repeat is justified.
Study tips
- Practice on classmates in the lab, without exposures, until the steps feel automatic.
- Learn landmarks by touch, such as the iliac crest, ASIS, vertebra prominens and EAM.
- Study images, not just text. Compare good and poor examples in your clinical rotations.
- Make your own summary cards for each exam: projections, central ray, landmarks and evaluation criteria.
- Check the official list. ARRT’s radiography content specifications list the procedures and positions you need to know. An update takes effect March 1, 2027.
Frequently asked questions
What’s the difference between a projection and a view? A projection describes the path of the x-ray beam through the body. A view describes the image as seen from the receptor. Most programs prefer projection terminology.
Why is a left lateral used for the chest? Placing the left side against the receptor puts the heart closer to it, which reduces magnification of the heart.
Do all departments use the same routines? No. Routines vary between facilities. Always follow your department’s protocols.
How can I remember central ray locations? Link each one to a palpable landmark, and practice positioning repeatedly. Summary cards and practice tests help.
Sources
- Standard positioning references, such as Frank, Long and Smith, Merrill’s Atlas of Radiographic Positioning and Procedures, and Lampignano and Kendrick, Bontrager’s Textbook of Radiographic Positioning and Related Anatomy.
- American Registry of Radiologic Technologists (ARRT): Radiography Content Specifications and Updated Radiography Documents (effective March 1, 2027).
For education only. Always follow your program’s instruction and your facility’s protocols when positioning patients.