8.2 Chest & Thorax Radiography
Key Takeaways
- PA upright chest at ~180 cm SID with full inspiration is the preferred standard when the patient can stand; AP portable geometry increases cardiac magnification and needs careful centering and technique.
- Acceptable inspiration on PA chest is commonly judged by visualizing about 10 posterior ribs above the diaphragm; rotation is judged by SC joint symmetry.
- Left lateral chest demonstrates the heart with less magnification than right lateral; posterior ribs should be nearly superimposed for a true lateral.
- Lordotic (apical) projections throw the clavicles above the apices; horizontal-beam decubitus chest evaluates air–fluid levels or free pleural air when upright imaging is limited.
- High-kVp chest technique with appropriate grid use (department-dependent) balances penetration of mediastinum and lung detail; pediatrics and portables need lower dose strategies, immobilization, and often non-grid adaptations.
8.2 Chest & Thorax Radiography
Quick Answer: Prefer PA upright chest at ~180 cm SID on full inspiration with SC joints symmetric and ~10 posterior ribs above the diaphragm. Add left lateral, lordotic, or decubitus as indicated. Portables use AP geometry with careful centering, higher awareness of magnification, and technique adapted for grid/non-grid and patient condition.
General radiography of the respiratory system is a high secondary-weight clinical procedure area on the CAMRT Radiological Technology blueprint. Expect application items that combine positioning criteria, pathology intent (pneumothorax, effusion, infiltrate, lines/tubes), and image critique. This section is core RTR.4 procedure knowledge tightly linked to RTR.6 acceptance decisions.
Why Chest Technique Matters
The thorax mixes high-contrast air-filled lung with dense mediastinum and spine. Goals of a standard chest series:
- Demonstrate lung parenchyma, pleural surfaces, and costophrenic angles
- Show mediastinal contours, heart size (with geometry understood), and hila
- Include apices free of clavicular superimposition when clinically required
- Visualize support devices (ETT, central lines, NG tubes, chest tubes) in correct anatomic context
- Minimize cardiac magnification and avoid rotation that mimics pathology
Standard PA Chest
Patient position and setup
| Element | Typical practice |
|---|---|
| Position | Upright, facing IR; chin elevated; shoulders rolled forward to move scapulae lateral to lung fields |
| SID | ≈ 180 cm |
| CR | Perpendicular to IR, centered at approximately T7 (inferior scapular angles) mid-sagittal |
| Collimation | Apices to costophrenic angles; lateral skin margins; avoid open abdomen field |
| Markers | Correct R/L; upright annotation as required |
| Respiration | Second full inspiration hold (after coaching) |
| Exposure | On suspended full inspiration |
Shoulders rolled forward / hands on hips or hugging Bucky: Moves scapulae out of the upper lung fields so they do not obscure lung detail.
Evaluation criteria (PA)
| Criterion | Acceptable appearance |
|---|---|
| Inspiration | About 10 posterior ribs visible above the diaphragm (department may teach 10 posterior or 6 anterior—know both; CAMRT-style items often use posterior rib count) |
| Rotation | Medial clavicles equidistant from spinous process; SC joints symmetric |
| Tilt | Clavicles in expected horizontal relationship; chin not superimposing apices |
| Coverage | Both apices, both costophrenic angles, lateral soft tissues |
| Scapulae | Primarily outside lung fields |
| Exposure | Vascular markings visible in lungs; spine just visible through heart (technique-dependent digital processing) |
| Motion | Sharp diaphragms and vessel margins |
Inspiration coaching
Poor inspiration crowds lung markings, elevates the diaphragm, and can mimic basilar disease. Coach:
- “Take a deep breath in… blow it out.”
- “Another deep breath in—hold still—don’t breathe.”
- Expose at full hold; release immediately after.
Expiration chest is a special request (e.g., suspected pneumothorax, foreign body, or comparison)—do not confuse with a failed inspiration PA. Expiration can make a small pneumothorax more conspicuous as lung volume falls.
AP Chest (Including Portable)
Use AP when the patient cannot stand for PA: ICU, emergency stretcher, severe dyspnea, trauma precautions.
| Element | AP / portable considerations |
|---|---|
| Position | Supine or semi-erect preferred over flat if clinically allowed (air–fluid and physiology better semi-erect) |
| SID | Often shorter than 180 cm in crowded rooms—note magnification and adjust mAs |
| CR | Perpendicular to sternum/IR when possible; if patient is semi-erect and IR angled, angle CR to remain perpendicular to IR to reduce lordotic distortion |
| Heart size | Appears more magnified than PA (heart farther from IR) |
| Clavicles | May project higher / more horizontal; can obscure apices |
| Grid | Use when OID/part thickness and portable grid policy support it; grid cutoff is a major portable pitfall |
| Lines/tubes | Include relevant devices; do not pull tubes; communicate with nursing |
Portable safety and quality
- Verify identity and order at bedside; explain the exam briefly.
- Clear non-essential staff; announce exposure; use distance and lead for those who must stay (RTR.1).
- Watch for grid upside-down, tilted, or decentered → severe density cut-off.
- Prevent image receptor contamination; follow infection control for ICU patients.
- Document position (supine/semi-erect), SID if nonstandard, and inspiration quality when relevant.
Lateral Chest
Usually performed as left lateral (left side against IR) so the heart is closer to the IR, reducing cardiac magnification.
| Element | Typical practice |
|---|---|
| Position | Upright left lateral; arms elevated out of lung fields; MSP parallel to IR |
| SID | ≈ 180 cm |
| CR | Perpendicular, mid-thorax at ~T7 level |
| Collimation | Sternum to posterior ribs / skin; apices to costophrenic angles |
| Respiration | Full inspiration |
Lateral evaluation criteria
| Criterion | Acceptable appearance |
|---|---|
| Rotation | Posterior ribs nearly superimposed (within ~1 cm typical teaching tolerance) |
| Arms | Not overlapping upper lungs |
| Hila | Approximately superimposed |
| Sternum | In profile |
| Coverage | Apices, bases, posterior costophrenic sulci |
| Motion | Sharp diaphragms |
Right lateral may be requested for right-sided pathology (bring side of interest closer to IR) or when left lateral is impossible.
Lordotic (Apical) Chest
Purpose: Project clavicles superior to the apices to evaluate apical disease (e.g., tuberculosis suspicion, apical masses) without clavicular superimposition.
| Approach | Method |
|---|---|
| Patient lordotic | Patient stands away from IR and arches back, shoulders against Bucky; CR perpendicular |
| Tube angle | Patient AP upright against IR; CR angled cephalad (often ~15–20°) to achieve similar clavicle projection |
Critique: Clavicles should lie above the apices; apices free for inspection; no excessive rotation.
Decubitus Chest for Air–Fluid Relationships
Use when the patient cannot stand but pleural fluid or free air must be assessed, or when comparing layering.
| Clinical goal | Typical approach |
|---|---|
| Pleural effusion | Affected side down (fluid layers along dependent chest wall); horizontal beam |
| Pneumothorax | Affected side up (air rises); horizontal beam; sometimes expiration per protocol |
| Air–fluid level in cavity | Horizontal beam essential; side selection per protocol/pathology |
Must-haves: true lateral or AP/PA projection with horizontal CR, adequate inspiration if possible, inclusion of the side of interest, and annotation of which side is down.
Technique: kVp, mAs, Grid, and AEC
Chest technique philosophy emphasizes high kVp (often in the 110–125 kVp range for adult upright Bucky work, department-specific) to penetrate the mediastinum while still showing lung detail with digital processing. Lower kVp increases contrast but may underexpose mediastinum or raise dose if mAs climbs excessively.
| Factor | Practical notes |
|---|---|
| kVp | High enough for mediastinal penetration; pediatric lower; follow technique charts |
| mAs / AEC | AEC chambers: typically outer cells for PA lungs; avoid centering heart over a single center cell if it drives wrong exposure—know your equipment |
| Grid | Upright Bucky chest usually grid; very small patients/neonates often non-grid; portable grid only when aligned |
| Filtration / processing | Use approved chest algorithms; do not “window away” a badly underexposed histogram as a quality fix |
Grid vs non-grid decision drivers: part thickness, kVp, scatter volume, ability to align grid, and pediatric dose policy. Misaligned grid is worse than no grid.
Pediatric Chest Notes
- Prioritize immobilization and caregiver assistance per policy; never expose hands in the primary beam.
- Use pediatric technique charts, shorter exposure times, and appropriate collimation (include airway when indicated).
- SID may follow department pediatric protocols; still minimize OID.
- Inspiration timing is harder—use calm coaching, distraction, and experience with crying infants (exposure near full inspiration).
- Gonad/thyroid shielding: follow current facility guidance; never obscure required anatomy or AEC.
- Minimize repeats: one carefully prepared exposure beats two rushed ones.
Pathology and Indication Links (Exam Mindset)
| Indication | Positioning implication |
|---|---|
| Infiltrate / pneumonia | Full inspiration PA + lateral; avoid underinspiration mimics |
| Pleural effusion | Upright or decubitus affected-side-down |
| Pneumothorax | Upright; consider expiration or lateral decubitus affected-side-up per protocol |
| CHF / cardiomegaly | Prefer PA for heart size; note AP magnification |
| Apical TB concern | Lordotic or carefully collimated apical views |
| Line placement | Include relevant anatomy; annotate portable/semi-erect |
| Foreign body (child) | PA inspiration/expiration or lateral; soft-tissue neck if upper airway (next section) |
Positioning Summary Table — Chest
| Projection | Patient position | CR | Key criteria |
|---|---|---|---|
| PA chest | Upright, chest against IR, shoulders rolled forward | ⊥ to T7, 180 cm SID | 10 posterior ribs; SC symmetry; apices & CP angles |
| AP chest | Supine or semi-erect | ⊥ to IR/sternum as able | Note magnification; include devices; minimize rotation |
| Left lateral | Upright, left side to IR, arms up | ⊥ mid-thorax ~T7, 180 cm | Posterior ribs superimposed; arms clear |
| Lordotic / apical | Lordotic stance or cephalad CR | Per protocol to project clavicles up | Clavicles above apices |
| Lat. decubitus | Side down per indication; horizontal beam | Horizontal, chest centered | Side annotated; air/fluid demonstrated |
Bottom Line for High-Weight Respiratory Radiography
Default to PA + left lateral upright at long SID with coached inspiration and zero avoidable rotation. Adapt to AP portable, lordotic, and decubitus when clinical status or pathology demands it. Critique every chest against inspiration, rotation, coverage, and exposure—because respiratory examinations are frequent, high-stakes, and heavily represented in RTR procedure and image-analysis competencies.
What is the preferred standard projection geometry for an ambulatory adult chest examination when the patient can stand?
Approximately how many posterior ribs should be visible above the diaphragm on an adequately inspired adult PA chest radiograph?
Compared with a PA chest, an AP portable chest radiograph typically demonstrates the heart as:
A patient cannot stand. The order is to evaluate a right pleural effusion with a horizontal beam. Which position is most appropriate?