Thorax and Abdomen
Chest
Anatomy
Students should be able to identify the following structures on radiographic images:
Alveoli, Aortic Arch, Apex, Base, Bronchi, Cardiophrenic angle, Carina, Clavicle, Costophrenic angle, Heart, Hilum, Hyoid bone, Jugular notch (manubrial or suprasternal notch). Larynx, Lobes, Lungs, Mediastinum, Pharynx, Pleura, Ribs, Scapulae, Sternum, Thoracic spine (12 vertebrae), Thyroid cartilage, Trachea, Vertebra prominens (seventh cervical vertebra), Xiphoid process
Routine Projections (ARRT Required)
PA Chest (Upright)
CR Location & Positioning
- SID: 72 inches (reduces heart magnification)
- Patient position: Upright, facing IR, MSP centered
- Adjustments: Chin raised, shoulders rolled forward and down to move scapulae out of lung fields; hands on hips or handles
- CR: Perpendicular to IR at level of T7 (7–8 inches below vertebra prominens or at inferior angle of scapula)
- Patient instructions: Take a deep breath in, hold it
- Exposure: On full inspiration (two inspirations preferred)
Evaluation Criteria
- Coverage (what anatomy must be included and how you verify it’s complete): Entire lungs from apices to costophrenic angles
- Rotation checks (how symmetry or alignment tells you if positioning is correct): Sternoclavicular joints equidistant from spine
- Motion checks (how sharpness confirms patient cooperation/exposure timing): Sharp vascular markings, visible spine through heart shadow
- Technique checks (what contrast, density, soft tissue visibility, and artifacts to look for): Adequate contrast with 10 posterior ribs above diaphragm
- Clinical aim (what contrast, density, soft tissue visibility, and artifacts to look for): Evaluate lung fields, heart size, and mediastinal structures
AP Chest (Upright or Semi-Erect)
CR Location & Positioning
- SID: 72 inches
- Patient position: Upright or semi-erect, back against IR
- Adjustments: Chin raised, shoulders relaxed, arms at sides
- CR: Angled caudad ~5° to be perpendicular to long axis of sternum, centered at T7
- Patient instructions: Deep inspiration, hold it
- Exposure: On full inspiration
Evaluation Criteria
- Coverage: Both lungs from apices to costophrenic angles
- Rotation checks: Sternoclavicular joints symmetric
- Motion checks: Sharp lung markings, clear diaphragm outline
- Technique checks: Clavicles projected just below apices, adequate contrast for vascular markings
- Clinical aim: Evaluate lungs when PA projection is not possible (bedside, trauma, immobile patients)
Lateral Chest (Upright)
CR Location & Positioning
- SID: 72 inches
- Patient position: Upright, left side against IR (to minimize heart magnification)
- Adjustments: MSP parallel to IR; arms raised above head or holding bar; chin elevated
- CR: Perpendicular at level of T7 (3–4 inches below jugular notch)
- Patient instructions: Deep inspiration, hold it
- Exposure: On full inspiration
Evaluation Criteria
- Coverage: Entire lungs from apices to costophrenic angles
- Rotation checks: Posterior ribs superimposed, sternum in lateral profile
- Motion checks: Sharp lung and diaphragm borders
- Technique checks: Adequate density to visualize retrocardiac lung field
- Clinical aim: Evaluate depth of pathology, heart size, and retrosternal/retrocardiac regions
AP Supine (Bedside Chest)
CR Location & Positioning
- SID: 40–48 inches (mobile)
- Patient position: Supine, MSP centered, arms at sides
- Adjustments: Chin raised, shoulders relaxed
- CR: Angled caudad ~5° to be perpendicular to sternum, centered at T7 (3–4 inches below jugular notch)
- Patient instructions: Deep inspiration, hold it
- Exposure: On full inspiration
Evaluation Criteria
- Coverage: Both lungs included; apices through costophrenic angles
- Rotation checks: SC joints symmetric
- Technique checks: 8–9 posterior ribs above diaphragm (less inspiration expected)
- Clinical aim: Portable evaluation of lungs and pleura in trauma or critically ill patients
Supplemental Projections
AP Lordotic (Apical Lordotic Projection)
CR Location & Positioning
- SID: 72 inches
- Patient position: Upright, 1 foot from IR, leaning back so shoulders rest on IR
- Adjustments: Hands on hips, shoulders rolled forward
- CR: Perpendicular to midsternum (3–4 inches below jugular notch)
- Patient instructions: Deep inspiration, hold it
Evaluation Criteria
- Coverage: Lung apices free of superimposition
- Rotation checks: SC joints symmetric
- Technique checks: Clavicles nearly horizontal and projected above apices
- Clinical aim: Demonstrates apical pathology (tuberculosis, neoplasm)
Lateral Decubitus (Horizontal Beam)
CR Location & Positioning
- SID: 72 inches
- Patient position: Lateral recumbent, side of interest against IR
- Adjustments: Arms above head, chin raised
- CR: Horizontal beam to level of T7 (3–4 inches below jugular notch), centered to MSP
- Patient instructions: Deep inspiration, hold it
Evaluation Criteria
- Coverage: Entire lung field on dependent side
- Rotation checks: SC joints symmetric
- Clinical aim: Detect air-fluid levels or free intrapleural air (fluid side down, air side up)
Chest Pathology and Exposure Adjustment Summary
| Pathology | Radiographic Appearance | Exposure Adjustment | Key Considerations |
|---|---|---|---|
| Atelectasis | Increased density; possible tracheal deviation toward affected side | ↑ mAs or kVp slightly | Collapsed lung increases tissue density |
| Pleural Effusion | Fluid level with meniscus sign; blunted costophrenic angles | ↑ mAs or kVp moderately | Fluid absorbs more radiation — use upright or decubitus |
| Pneumonia | Patchy or lobar consolidation | ↑ mAs moderately | Fluid-filled alveoli reduce beam transmission |
| Pulmonary Edema / CHF | Enlarged heart; “bat-wing” perihilar pattern | ↑ mAs moderately | Fluid overload and venous congestion |
| Emphysema | Hyperinflated, radiolucent lungs; flattened diaphragm | ↓ mAs | Excess air increases radiolucency |
| COPD (Chronic Bronchitis / Emphysema) | Hyperaeration, flattened diaphragm, elongated lungs | ↓ mAs slightly | Reduced attenuation due to chronic air trapping |
| Pneumothorax | Absence of lung markings; lung edge visible | ↓ mAs slightly | Air increases radiolucency; use upright/expiration |
Hows & Whys of Chest Radiography
Anatomy
- How many lobes does each lung have, and why does this matter?
The right lung has three lobes; the left has two to accommodate the heart. Knowing lobe divisions helps localize pathology. - How do the right and left mainstem bronchi differ?
The right mainstem bronchus is shorter, wider, and more vertical than the left, making it a common site for aspirated foreign bodies. - Which lung will foreign bodies most often localize in?
The right lung, because the right main bronchus is larger and more vertical than the left. - How do the costophrenic and cardiophrenic angles help in diagnosis?
Blunting of these angles indicates pleural effusion or cardiomegaly. - How can the carina help evaluate endotracheal tube placement?
The carina is the bifurcation of the trachea; correct tube placement ends 1–2 inches above it. - How does the mediastinum change with patient position?
In supine position, mediastinal structures appear widened due to projection and fluid redistribution. - Which way does the diaphragm move on inspiration? On expiration?
Down on inspiration; up on expiration. - Why?
The diaphragm is a dome-shaped muscle. When it contracts, it flattens and moves downward, creating negative pressure in the thoracic cavity so air flows into the lungs.
When it relaxes, it returns to its dome shape, compressing the lungs and forcing air out.
Positioning
- Why should chest radiographs be performed upright?
To allow full lung expansion and to demonstrate air-fluid levels and pleural effusions accurately. - Why is 72-inch SID used?
It minimizes heart magnification and improves spatial resolution of lung detail. - Why is a PA projection preferred over an AP?
It reduces heart magnification, provides better spatial resolution, and lowers breast dose. - Why are shoulders rolled forward on the PA view?
To move the scapulae laterally, clearing the lung fields. - Why is the chin elevated for PA and lateral views?
To prevent superimposition of the chin on lung apices. - Why is a left lateral preferred?
It places the heart closer to the IR, reducing magnification. - Why angle the CR caudad for AP projections?
To project the clavicles below the apices and avoid obscuring them. - Why are decubitus projections used?
To demonstrate air-fluid levels with a horizontal beam when the patient cannot stand.
Technique & Image Evaluation
- How do you know the patient took a full inspiration?
Ten posterior ribs should be visible above the diaphragm. - How do you check for rotation on PA chest?
Sternoclavicular joints are equidistant from the spine. - How do you detect motion on a chest radiograph?
Vascular markings and diaphragm borders should be sharp with no blurring. If they are blurred, motion has occurred. - How do you check for rotation on a lateral?
Posterior ribs are superimposed and sternum appears in profile. - How do you know exposure is appropriate?
The thoracic spine should be faintly visible through the heart shadow, indicating sufficient penetration without overexposure. - What happens if exposure time is too long?
Motion blur obscures vascular markings and diaphragm borders. - How do you identify under-inspiration?
Less than ten posterior ribs visible, diaphragm appears high, and heart looks enlarged. - How do you confirm correct positioning for a decubitus chest?
No rotation (SC joints symmetric) and horizontal beam clearly showing air or fluid shift.
Clinical Applications
- Why are chest x-rays often the first imaging exam performed?
They provide rapid, low-dose assessment of lungs, heart, and thoracic structures. - When would expiration be used for chest imaging?
When we need to identify possible pneumothorax. - How can pleural effusion be demonstrated best?
With an upright or side-down decubitus projection (fluid rises when side up, layers when side down). - How can pneumothorax be demonstrated best?
With an upright or side-up decubitus projection, often on expiration to accentuate trapped air. - Why are decubitus views ordered for trauma or post-surgical patients?
They demonstrate free air or fluid when upright imaging isn’t possible. - How does COPD or emphysema affect exposure technique?
Decrease mAs slightly — the lungs are hyperinflated and radiolucent. - How does pneumonia or pleural effusion affect exposure technique?
Increase mAs moderately to compensate for denser, fluid-filled lung tissue. - Why is repeatability important in chest imaging?
Comparing current and prior studies allows monitoring of disease progression or resolution.
