Fundamentals of HRCT - GGO and consolidation

Question 1

on imaging, what do GGO represent?

Answer 1

abnormalities below the resoution of HRCT. should not be able to see vessels.

May represent alveolar filling, alveolar wall thickening, or a combination. May represent alveolar filling, inflammation, or fibrosis.

Question 2

what is the differential for acute GGOs? (<6 weeks) (7)

Answer 2

infection (usually atypical) - viral, legionealla, mycoplasma, chlamydia, PJP
edema
acute lung injury
hemorrhage
aspiration
acute HP
AEP

Question 3

what is the differential for chronic GGOs (>6 weeks), broken down by distribution (10)

Answer 3

peripheral
- NSIP
- DIP
- chronic EP
- OP

central
- chronic HP
- RB
- LIP
- follicular bronchiolitis
- alveolar proteinosis
- sarcoid

Unilateral/asymmetric
- invasive mucinous adenocarcinoma
- lipid pneumonia

Question 4

what is the differential for consolidation based on symptom duration?

Answer 4

acute
- infection
- edema
- acute lung injury
- hemorrhage
- aspiration
- HP
- AEP

chronic
- OP
- chronic EP
- invasive mucinous
- sarcoid
- lymphoma
- lipoid pneumonia
- cHP

Question 5

what is atolls sign

Answer 5

ring of consolidation surrounding GGOs

Question 6

what is the differential for atolls sign

Answer 6

usually OP - COP, drugs, CTD, inhalations, immunodeficiencies

DDX - CEP, HP, infection (fungal, viral), GPA