Chest X-Rays (CXR)

Overview:

• Chest X-rays are a quick, non-invasive, and widely available imaging tool that provides basic visualisation of the heart, lungs, and bones.
• Different tissues absorb varying amounts of radiation: bones appear white, while lungs appear gray.

Technique:

• Two views are standard: posteroanterior (PA) and lateral.
• Additional views, such as oblique or decubitus, may be needed.
• Patients are often asked to hold their breath during imaging to prevent blurring.

Uses:

• Diagnose and monitor respiratory and cardiac conditions, including:
  • Pneumonia
  • Tuberculosis (TB)
  • Chronic obstructive pulmonary disease (COPD)
  • Lung cancer
  • Rib fractures
  • Pleural effusions

Common Findings:

1. Pneumonia:
   • Consolidation: Homogenous opacity obscuring blood vessels.
   • Air bronchograms: Visible air-filled bronchi surrounded by consolidation.
2. Tuberculosis (TB):
   • Cavities: Darker areas with thick walls, often in upper lobes.
   • Nodules or consolidation.
3. COPD:
   • Hyperinflation: Flattened diaphragm, increased retrosternal air space.
4. Lung Cancer:
   • Nodules or masses.
   • Atelectasis: Collapse of lung tissue due to obstruction.
5. Interstitial Lung Disease (ILD):
   • Reticular or nodular patterns indicating interstitial thickening.
6. Pleural Effusion:
   • Uniform opacity with blunted costophrenic angles.
7. Pneumothorax:
   • Translucent areas without lung markings, indicating air in the pleural space.

Limitations:

• Misses subtle fractures or early-stage diseases.
• Limited sensitivity for identifying soft tissue abnormalities.

High-Resolution Computed Tomography (HRCT)

Overview:

• HRCT uses thin slices and advanced algorithms to provide detailed images of lung parenchyma, offering superior spatial resolution compared to standard CT scans.

Technique:

• Imaging is acquired in thin slices with patients in supine and prone positions.
• Performed during inspiration and expiration to identify dynamic changes.

Applications in ILD:

• HRCT is the gold standard for diagnosing ILDs.

Key Patterns:

1. Usual Interstitial Pneumonia (UIP):
   • Honeycombing: Clustered cystic airspaces.
   • Reticulation: Linear opacities.
   • Subpleural, basal predominance.
2. Non-Specific Interstitial Pneumonia (NSIP):
   • Bilateral ground-glass opacities with basal distribution.
3. Hypersensitivity Pneumonitis:
   • Diffuse ground-glass opacities with centrilobular nodules.
4. Organising Pneumonia (OP):
   • Patchy peripheral consolidation, sparing subpleural areas.
5. Sarcoidosis:
   • Perilymphatic nodules and fibrosis, typically in upper lobes.

Advantages:

• May eliminate the need for biopsy in classic cases (e.g., UIP).
• Tracks disease progression and response to treatment.

Positron Emission Tomography-Computed Tomography (PET-CT)

Overview:

• PET-CT combines metabolic imaging (PET) with detailed anatomical imaging (CT).
• Uses a radiotracer, commonly fluorodeoxyglucose (FDG), to detect areas of increased metabolic activity.

Technique:

• A radioactive tracer is injected, and its uptake is detected by the PET scanner.
• CT provides structural localisation of metabolically active areas.

Key Applications:

1. Cancer Staging:
   • Detects metastases in systemic cancers, including lung cancer.
   • Aids in treatment planning and surgical decisions.
2. Lung Cancer:
   • Differentiates malignant from benign lesions.
   • Monitors treatment response and identifies recurrence.
3. Infection and Inflammation:
   • May identify granulomatous diseases, but caution is needed due to false positives.

Limitations:

• False Positives: Granulomatous diseases (e.g., sarcoidosis) and inflammation.
• False Negatives: Small (<1 cm) or low-grade tumours.

Clinical Impact:

• Reduces unnecessary surgeries by accurately staging cancers and identifying metastatic spread.

Key Takeaways for Pharmacy Students

• Chest X-Rays: Widely used for initial assessments of respiratory conditions, particularly infections, COPD, and cancer.
• HRCT: Essential for diagnosing ILDs, with characteristic patterns guiding treatment and biopsy decisions.
• PET-CT: Critical in cancer management, providing both diagnostic and prognostic information.

Clinical Relevance:

Familiarity with these imaging modalities allows pharmacists to:

• Understand diagnostic terminology and findings.
• Optimise pharmacotherapy based on the specific respiratory condition.
• Educate patients about the role of imaging in their care.

References

1. MSD Manual. (n.d.). Chest Imaging for Lung Disorders. Retrieved from https://www.msdmanuals.com/home/lung-and-airway-disorders/diagnosis-of-lung-disorders/chest-imaging

2. Brunetti, M. A., & Mahadevan, V. (2022). Diagnostic imaging of chest disorders. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK558976/

3. Cleveland Clinic. (n.d.). Chest X-Ray. Retrieved from https://my.clevelandclinic.org/health/diagnostics/10228-chest-x-ray

4. Radiology Assistant. (n.d.). Chest X-Ray: Lung Disease Interpretation. Retrieved from https://radiologyassistant.nl/chest/chest-x-ray/lung-disease

5. Yoon, S. H., et al. (2022). Advances in radiologic imaging for pulmonary diseases. Journal of Thoracic Imaging, 37(2), 161-171. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC8996276/

6. Lynch, D. A., et al. (2022). HRCT in the Diagnosis of Interstitial Lung Disease. In StatPearls. StatPearls Publishing. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK553872/#:~:text=HRCT%20plays%20a%20central%20role,the%20distribution%20of%20the%20findings.

7. Jacob, J., & Hansell, D. M. (2022). High-Resolution CT in Pulmonary Disease. Radiology Review Journal, 45(6), 349-366. Retrieved from https://pubmed.ncbi.nlm.nih.gov/36307108/

8. Fraser, R. G., & Pare, J. A. P. (2007). Radiologic imaging of pulmonary disease: Past and present perspectives. Chest, 131(4), 945-952. Retrieved from https://pmc.ncbi.nlm.nih.gov/articles/PMC1805068/