The document discusses the role of chest imaging in diagnosing and managing COVID-19. It states that while RT-PCR is the gold standard diagnostic test, chest imaging can be useful when PCR testing is unavailable, results are delayed, or initial PCR is negative but clinical suspicion remains high. Chest x-rays and CT scans may show findings like ground glass opacities and lung consolidations indicative of COVID-19. The document outlines several chest imaging scoring systems and provides recommendations on its use from diagnostic to therapeutic contexts according to WHO guidelines.

1. Dr Vikas Balania ,
MD Medicine

2.  COVID-19 : is an infectious disease caused by severe acute respiratory syndrome
coronavirus 2.
 The diagnosis of COVID-19 is currently confirmed by identification of viral RNA through
reverse transcriptase polymerase chain reaction (RT-PCR).
 In settings where laboratory testing (RT-PCR) is not available or results are delayed or results
are initially negative in the presence of symptoms attributable to COVID-19, chest imaging has
been considered as part of the diagnostic workup of patients with suspected or probable
COVID-19.
 Imaging has been also considered to complement clinical evaluation and laboratory parameters
in the management of patients, already diagnosed with COVID19

3. WHO RECOMMENDATIONS
 For asymptomatic contacts of patients with COVID-19.
 For symptomatic patients with suspected COVID-19, WHO suggests using chest
imaging for the diagnostic workup of COVID-19 when:
(1)RT-PCR testing is not available;
(2)RT-PCR testing is available, but results are delayed; and
(3)Initial RT-PCR testing is negative, but with high clinical suspicion of COVID-19.

4.  For patients with suspected or confirmed COVID-19 with mild symptoms, not
currently hospitalized.
WHO suggests using chest imaging in addition to clinical and laboratory assessment to
decide on hospital admission versus home treatment

5.  For patients with suspected or confirmed COVID-19, not currently hospitalized and
with moderate to severe symptoms
WHO suggests using chest imaging in addition to clinical and laboratory assessment to
decide on regular ward admission versus intensive care unit (ICU) admission.

6.  For patients with suspected or confirmed COVID-19, currently hospitalized and with moderate
to severe symptoms.
WHO suggests using chest imaging in addition to clinical and laboratory assessment to inform
the therapeutic management.

7.  For hospitalized patients with COVID-19 whose symptoms are resolved. WHO suggests not
using chest imaging to inform the decision regarding discharge.
 WHO suggests not using chest imaging for the diagnostic workup of COVID-19 when RT-
PCR testing is available with timely results.
 RT-PCR should be done to confirm diagnosis.

9. (A) Chest Radiograph : First-line imaging modality
 Sensitivity(50-69%)& specificity(30-40%).
 Remains normal for 4-5 days after start of symptoms.
 Findings are most extensive at about 10-12 days after symptom onset.
 Most common finding- air space opacities
 Uncommon findings are- Cavity, pleural effusion, pneumothorax & lymphadenopathy.
(B) Computed Tomography :
 Has high sensitivity(97%) and specificity.
 HRCT is better then contrast study as contrast can affect the GGOs.

10. Chest X Ray Scoring System : BRIXIA SCORE (AIIMS DELHI)
 Includes two steps of image analysis.
 Each lung was divided into three zones named from A to F ,
1. Upper (A/D) above aortic arch,
2. Middle (B/E) below aortic arch to hilum and
3. Lower zones (C/F) below hilum to bases, on both posteroanterior or anteroposterior projections.
 Each zone was given a score of 0 to 3 based on lung abnormalities detected:
Score 0 - no abnormality,
Score 1 - interstitial infiltrates,
Score 2 - interstitial and alveolar infiltrates with interstitial predominance,
Score 3 - interstitial and alveolar infiltrates with alveolar predominance.

11.  Scores were added to form a cumulative CXR SCORE ranging from 0 – 18 , with partial score of
each zone entered as well. Other additional findings like pleural effusion were mentioned
separately.
 Score was higher in patients who died than with those recovered.(p<0.002)

12. (A) Bacterial Pneumonia vs Viral pneumonia :

13. Air bronchogram :
 Defined as gas filled bronchi
which are surrounded by
fluid filled alveoli.
 Sign of alveolar pathology
rather then interstitium.
 Seen in Pulmonary Edema,
consolidation, ARDS etc.

14. (B) Specific for COVID 19
(1) Ground glass densities :
 Most common reported CXR
and CT findings of COVID-
19.
 Not so evident as on CT scan

15. CXR (left) with patchy peripheral left mid to lower lung opacities (black arrow) corresponding to ground
glass opacities (white arrow) on coronal section of chest CT (right).

16. (B) Bilateral lower lobe
consolidations :

17. (C) Peripheral air space
opacities :

18. (D) Uncommon CXR findings:
Lung cavitation and pneumothorax Localized large nodule

19. Various findings:
 GGO- Ground glass opacities.
 GGO + underlying interstitial reticular thickening (Crazy paving).
 Focal consolidations
 Fibrosis (more in later stages) and traction bronchiectasis.
 Vascular dilatation
 Pleural effusion (rare but can be seen).
Distribution is predominantly bilateral, multifocal, subpleural, peripheral and more in both lower
lobes.

21. Ground glass opacities

23. GGOs CONSOLIDATION

24. Crazy paving is thickened interlobular and intralobular lines in combination with a ground
glass pattern. It is believed that this pattern is seen in later stage !
Crazy paving

25. Pt. Presented with high-grade fever and breathlessness
HRCT chest showing GGO, interstitial thickening, crazy paving and traction bronchiectasis with extensive
lung involvement. RT-PCR proven case of COVID infection.

26. VASCULAR DILATATION

27. BRONCHIAL DILATATION

28. “Parallel pleura sign” “Paving stone sign” “Bronchiectasis”

29. Vascular sign” “Halo sign” “Reverse halo sign

30.  EACH LOBE IS GIVEN SCORE 1 TO 5 BASED ON INVOLVEMENT
INFECTION CRITERIA
(SINGLE LOBE) :
5 % INFECTED : SCORE 1
5-25 % INFECTED: SCORE 2
25-50 % INFECTED: SCORE
3 50-75 % INFECTED:
SCORE 4 75 % INFECTED:
SCORE 5

31. The total CT score is the sum of the individual lobar scores and can range
from 0 (no involvement) to 25 (maximum involvement), when all the five
lobes shows more than 75% involvement.

32. CT SEVERITY SCORE 9 OUT OF 25: means lungs are moderately infected with COVID-19
in this particular patient

33. IMPACT ON TREATMENT
 STAGE 1 (0-4 days) - 75% of HRCT is positive in this stage.
 STAGE 2 (5-9 days) - Lesion extent/burden continues to peak.
 STAGE 3 (10-14 days) - Disease burden peaks around ~10th day.
 STAGE 4 (15-21 days) - Disease starts resolving (Absorption stage).
 STAGE 5 (>21 days) – Fibrosis.

34. Exudative phase: Active viral multiplication & Infective –Rx with antiviral
Organizing phase: Immune mediated injury predominates – Rx with immune-modulators in severe cases
Resolving phase: Repair phase with architectural distortion – Rx with ?anti-fibrotic agents

35. Can HRCT Prognosticate the COVID 19 ??

36. CO-RADS classification :
 The CO-RADS classification is a standardized reporting system .
 Based on the CT findings, the level of suspicion of COVID-19 infection is graded from very
low or CO-RADS 1 up to very high or CO-RADS 5.
 CORADS-1 has high negative predictive value.
 CORADS 5 has high positive predictive value.

38. CO-RADS 1
• COVID-19
is highly
unlikely

39. CO-RADS 2
• Level of suspicion of COVID-
19 infection is low.
• Findings consistent with other
infections like typical
bronchiolitis with tree-in-bud
and thickened bronchus walls.
• No typical signs of COVID-19.
CT-image shows bronchiectasis, bronchial wall thickening and tree-in-bud.
No GGOs.

40. The images show bronchial wall
thickening, tree-in-bud (arrow) and
consolidation.
There are no ground glass opacities.
Lobar consolidation and tree-in-bud
(arrows) consistant with a bacterial
infection.

41. Tree in Bud appearance
Defined as impaction of centrilobular bronchus filled with pus/mucus/fluid resulting in dilatation of
bronchus with associated peribronchiolar inflammation.

42. CO-RADS 3
• COVID-19 unsure/ indeterminate.
• CT abnormalities indicating
infection, but unsure whether
COVID-19 is involved or not, like
widespread bronchopneumonia,
lobar pneumonia, septic emboli
with ground glass opacities.
Ct chest of 4 different patients showing unifocal GGOs.

43. CORADS 4
• The level of suspicion is high.
• Mostly these are suspicious CT findings
but not extremely typical:
 Unilateral ground glass opacities.
 Multifocal consolidations without
any other typical finding.
 Findings suspicious of COVID-19 in
underlying pulmonary disease.
Unilateral areas of GGO in left
upper lobe.
Bilateral GGO in a patient with
emphysema

44. CO-RADS 5
COVID is highly likely
Multifocal GGO and consolidation Bilateral multifocal GGO,
vascular thickening (circle),
subpleural bands (arrow).

45. CORADS 6
• Patient with positive PCR and
bilateral GGO.
• Halo sign (arrow).

46. Cases

47. CASE 1
Mildly symptomatic patient with
low-grade fever and throat pain
since 4- 5days.
HRCT CHEST showing classic peripheral GGOs consistent with viral
pneumonitis. This patient tested RT-PCR positive done after imaging.

48. CASE 2
PT Presented with high-
grade fever and
breathlessness.
HRCT chest showing GGO, interstitial thickening, crazy paving and
traction bronchiectasis with extensive lung involvement. RT-PCR proven
case of COVID infection.

49. CASE 3
An elderly patient with
multiple comorbidities,
severe breathlessness and
fever. .
HRCT chest showing bilateral GGOs, underlying interstitial fibrosis
and traction bronchiectasis. Patient had tested positive with RT-PCR after
the scan and unfortunately, this patient died due to respiratory
complications after 4 days

50. CASE 4
This patient had severe
breathlessness with fever
and increased D-dimer.
Initial RT-PCR was
negative.
(A) HRCT findings showed
peripheral GGOs and
consolidations on lung
window.
(B) Contrast images in soft
tissue window showed partial
pulmonary thromboembolism
(arrow marks).
Repeat RT-PCR was done which turned out to be positive

51. DIFFERENTIALS

52.  Other viral Pneumonias (eg- CMV) and
 Atypical bacterial pneumonia (eg- mycoplasma pneumonia)
 Opportunistic infections like:- PCP/ Pneumocystis jiroveci infection.
 Fungal infections.
 Pulmonary oedema
 Interstitial lung disease- like cryptogenic organising pneumonia and chronic eosinophilic
pneumonia (CEP)
 Small vessel vasculitis- eg Wegners granulomatosis

53. Immuno-compromised
patient
Pneumocystis jiroveci
Initial scan showing
diffuse GGO in both
lungs
Complete resolution in follow
up scan after treatment for
Pneumocystis jiroveci. HRCT
done after 1 month

54. Small vessel vasculitis-
Wegners granulomatosis
HRCT chest showing multiple lesions with central cavitations. Also bilateral
mild pleural effusion.

55. Known asthmatic with repeat
episodes of cough and
breathing difficulties.
Allergic bronchopulmonary aspergillosis (ABPA)
HRCT shows bronchiectasis with mucous plugging and peribronchiolar
opacity-consolidations.

56. Follow up of same pt after 1 month treatment shows significant
improvement, both radiologically and also clinically.

57. COVID vs Non-COVID Viral Pneumonia
Except for a higher prevalence of peripheral distribution, involvement of upper and middle lobes,
COVID-19 and non-COVID viral pneumonia had overlapping chest CT findings.

58. The sensitivity of HRCT was greater than that of RT-PCR (97% vs 71%, respectively) in many
prospective studies
HRCT VS RT-PCR (GOLD STD)

59.  HRCT chest is very sensitive and gold standard in imaging modalities.
 Helps in diagnosis when RT PCR is not available or results are delayed or in RT-
PCR negetive pts with high clinical suspicion.
 Assess the severity of lung involved and helps in deciding for home treatment vs
hospital treatment, in hospitalized pts for regular ward vs ICU admission and
provide road map for therapeutic management.