HALO SIGN.ppt

radiological sign on CT

1. HALO SIGN
.

2. Halo sign in chest
•The halo sign in chest imaging isa feature
seen on lung window settings, ground glass
opacity surrounding a pulmonary nodule or
mass and represents hemorrhage.
•It is typically seen in angioinvasive
aspergillosis.

3. What causes halo sign on CT
•The halo sign and reversed halo sign are most
commonly associated withinvasive pulmonary
aspergillosisand pulmonary mucormycosis,
respectively
•Many other infections and noninfectious
conditions, such as neoplasticand inflammatory
processes, may also manifest with pulmonary
nodules associated with either sign.

4. HALO SIGN ON CT –
ASPERGILOSIS

5. REVERSED HALO SIGN
•The reversed halo sign
(RHS) ischaracterisedby a
central ground-glass
opacity surrounded by a
more or less complete ring
of consolidation on high-
resolution CT (HRCT).
•It has also been described
as the “atoll sign” because
of its resemblance to a coral
atol
•( MOONGE KA ISLAND)

6. Halo sign in Covid

7. Halo versus reversed halo sign in Covid

8. Halo sign in Pulmonary TB

9. Halo sign in septic embolus

10. Causes
•Infectious disease
•fungi
–pulmonaryaspergillosis
–pulmonary mucormycosis
–pulmonary coccidioidomycosis
–pulmonary cryptococcosis
–pulmonary candidiasis

11. Causes
•septic embolism
•mycobacterial
–pulmonary tuberculosis
–pulmonary non-tuberculousmycobacterialinfection
•pulmonaryMycobacterium aviumcomplexinfection
•rickettsia-rickettsiapneumonia
•Coxiellaburnetii-Q fever pneumonia
•viral:herpes simplex virus,varicellazoster
virus(chickenpox),cytomegalovirus

12. Causes--
•Malignancy
•primary tumors
–adenocarcinomaof the lung,adenocarcinomain situor minimally
invasive (formerlybronchioalveolarcarcinoma)-
–squamouscell carcinoma of the lung
–Kaposi sarcoma
–pulmonary lymphoma
•lung metastases(especially -hemorrhagic pulmonary metastases):
–angiosarcoma
–choriocarcinoma
–osteosarcoma
–melanoma
–metastasis from gastrointestinal adenocarcinoma(<10%)

13. Causes-
•Non-neoplastic, non-infectious, inflammatory
diseases
•pulmonary infarction
•granulomatosiswith polyangiitis
•eosinophiliclung disease
•pulmonary endometriosis
•organizing pneumonia
•hypersensitivity pneumonitis
•iatrogenic injury
–radiation pneumonitis
6
•pulmonary pseudoaneurysm

14. What does Positive halo sign mean?
Basal skull fracture
•A “halo” or “ring” sign, occurs when cerebrospinal
fluid (CSF) mixes with blood on an absorbent surface
•The blood forms a spot in the center and a lightly
stained ring forms a halo around it
•The halo sign is reliable for detecting CSF but not
exclusive