Categorization of CT findings in COVID 19

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Salient  Points

The following article focuses mainly on the CT findings of COVID-19 patients, a classification of the images on the basis of their appearance, trends as well as frequency of various features of the images and the reports being made on the same. Literature is based upon reports at the time of writing in March 2020.

CT appearances may be classified as:

  • Typical: Bilateral, peripheral/ multifocal GGOs +/- consolidation and later reverse halo sign
  • Indeterminate: Multifocal/ diffuse, but perihilar GGOs +/- consildation
  • Atypical: Isolated/ lobar findings/ centrilobular nodules/ cavitation/ septal thickening. Atypical findings are points against Covid 19 pneumonia.

Detailed Summary 

The following are the various classification of CT images

  1. Typical Appearance – These are the most commonly reported imaging features of COVID-19 associated pneumonia
  • CT Findings
  1. Peripheral, B/L Ground Glass Appearance +/- Consolidation
  2. Multifocal Ground Glass Appearance +/- Consolidation
  3. Presence of Reverse Halo sign (seen later in disease progression)

Remarks – Common imaging features of pneumonia are present in typical appearance of COVID-19 pneumonia. Similar imaging patterns – influenza, pneumonia, organising pneumonia, drug toxicity, connective tissue disease.

  1. Indeterminate Appearance – Non Specific Findings on CT for COVID – 19 pneumonia
  • CT Findings
  1. Multifocal, diffuse, peri-hilar, U/L Ground Glass Appearance +/- Consolidation
  2. No Specific distribution
  3. Non Rounded, Non Peripheral Ground Glass Appearance

Remarks – CT image features are non specific and may be associated with other infectious and non infectious causes.

  1. Atypical Appearance – Uncommon CT findings among COVID-19 pneumonia.
  • CT Findings
  1. Isolated lobar/segmental consolidation +/- Ground Glass Appearance
  2. Centri-lobar Nodules (Tree – in – Bud appearance)
  3. Lung Cavitation
  4. Interlobular septal thickening + Pleural Effusion

Remarks – Atypical CT findings for COVID-19 pneumonia. Alternative diagnosis should be considered.

  1. Negative for pneumonia – No features of pneumonia
  • CT findings – Negative for pneumonia

Remarks – CT may be negative in the early stages of COVID-19.

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