Chest Computed Tomography (Chest CT)

Indications

  • xxx
  • xxx
  • xxx
  • xxx
  • xxx

Hounsfield Units

  • Low Density by Hounsfield Units Measurement: -50 to -300 HU is consistent with fat
  • Pure air or emphysema: -1000 HU
  • Normal lung parenchyma: -750 HU
  • Normal soft tissue and parenchymal lesions: around 10-70 HU
  • Calcified lesions: >100-400 HU
  • Bone: 1000 HU

Chest CT Differentiation: Empyema vs Lung Abscess

Empyema

CT Features of Empyema

  • Angles: “Ball Under the Carpet” Appearance: obtuse angeles between fluid collection and chest wall
  • Shape: lenticular shape
  • Internal Surface: typically smooth internal surface of fluid collection
  • Displacement: displacement of lung and mediastinum, as empyema pushes adjacent structures toward contralateral side
  • “Split Pleura” Sign: separation of parietal and visceral pleura
  • Air-Fluid Level: may be seen in cases with bronchopleural fistula (Bronchopleural Fistula, Bronchopleural Fistula)

CT Features of Lung Abscess

  • Angles: acute angles between fluid collection and chest wall
  • Shape: typically round shape
  • Internal Surface: typically thick, irregular internal surface of fluid collection
  • Displacement: lack of displacement of lung and mediastinum, as abscess tends to destroy adjacent lung, rather than displace it
  • Air-Fluid Level: may be seen

References

  • xxxx