radiological sign on CT

1. HALO SIGN
.

2. Halo sign in chest
• The halo sign in chest imaging is a 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 with invasive pulmonary
aspergillosis and pulmonary mucormycosis,
respectively
• Many other infections and noninfectious
conditions, such as neoplastic and 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) is characterised by 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
– pulmonary aspergillosis
– pulmonary mucormycosis
– pulmonary coccidioidomycosis
– pulmonary cryptococcosis
– pulmonary candidiasis

11. Causes
• septic embolism
• mycobacterial
– pulmonary tuberculosis
– pulmonary non-tuberculous mycobacterial infection
• pulmonary Mycobacterium avium complex infection
• rickettsia - rickettsia pneumonia
• Coxiella burnetii - Q fever pneumonia
• viral: herpes simplex virus, varicella zoster
virus (chickenpox), cytomegalovirus

12. Causes--
• Malignancy
• primary tumors
– adenocarcinoma of the lung, adenocarcinoma in situ or minimally
invasive (formerly bronchioalveolar carcinoma) -
– squamous cell 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
• granulomatosis with polyangiitis
• eosinophilic lung 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