Overview
This lecture covers key concepts in thoracic and abdominal radiography, focusing on chest and abdominal X-ray positioning, anatomy, and technical considerations.
Chest X-ray Techniques & Positioning
- Evaluate rotation on PA chest by checking clavicle symmetry.
- Use 72-inch source-to-image distance (SID) to reduce magnification.
- Perform left lateral chest X-ray to minimize cardiac shadow overlap.
- Lateral chest: identify anterior and posterior anatomical markers.
- Use lordotic chest view (cephalad angle) to evaluate for tuberculosis by projecting clavicles above lung apices.
- Decubitus chest X-rays detect pleural effusion; fluid will settle on the side down, air rises.
- Decubitus requires patient in position for five minutes and a horizontal beam.
- 45° oblique localizes structures; 60° is used for heart shadow evaluation.
- AP supine chest is used for intubated or immobile patients; check ET tube placement (5 cm above carina/T5/sternal angle).
- Most common aspiration site: right main bronchus (more vertical/higher than left).
- Use high kVp for chest X-rays to achieve long scale contrast.
- Know PA and lateral chest anatomy and bony thorax landmarks.
Rib and Chest Positioning
- Upper ribs: center at T7 with inspiration; lower ribs: T10 with expiration.
- Rib obliques: PA oblique elongates side away from IR; posterior oblique elongates side toward sternum.
- Lateral and RAO chest uses 72-inch SID to compensate for object-to-image distance (OID).
- RAO chest (15–20°) for heart shadow; less rotation in thicker chests.
- LPO is alternate to RAO if patient can't stand.
- Breathing technique for sternum: low mA, longer exposure to blur ribs.
Soft Tissue Neck
- Breathing instruction: slow, deep nose inspiration to fill airway.
- Indications: epiglottitis, stridor, or foreign body.
Abdominal Radiography
- Know abdominal quadrants and the organs within each.
- Use expiration for abdominal imaging to raise diaphragm and maximize organ visibility.
- Upright abdomen: center 2 inches above iliac crest to include diaphragm; look for free air (pneumoperitoneum) and air-fluid levels with horizontal beam.
- Left lateral decubitus abdomen preferred because the liver (right side) provides contrast for free air visualized above it, avoiding confusion with the gastric bubble.
- Patient should be in position for five minutes before exposure.
Key Terms & Definitions
- PA (Posteroanterior) — X-ray beam passes from back to front.
- SID (Source-to-Image Distance) — Distance from X-ray tube to detector.
- Lordotic View — Angled chest X-ray to visualize lung apices.
- Decubitus — Patient lying on their side for imaging.
- Pleural Effusion — Fluid in the pleural space.
- ET (Endotracheal) Tube — Tube for airway management, placed above the carina.
- High kVp — High kilovoltage peak for low-contrast images.
- Pneumoperitoneum — Free air in the abdominal cavity.
Action Items / Next Steps
- Review chest and abdomen X-ray positioning, breathing instructions, and relevant anatomy.
- Study quadrant locations and organ placement within the abdomen.
- Memorize key positioning rationales, tube placements, and terminology for exams.