Department of Diagnostic Radiology and Organ ImagingChinese University of Hong Kong

Prince of Wales HospitalHong Kong

KT Wong

Application & Imaging Features of SARS on HRCT

The Chinese University of Hong KongPrince of Wales Hospital

Background Outbreak in medical ward in PWH in March To the end of May, over 300 SARS patients

treated in our institution Imaging play an important role

- diagnosis

- monitor progress and treatment response

- assess long-term lung damage

The Chinese University of Hong KongPrince of Wales Hospital

Indication Not all patients with suspected SARS need

HRCT scan Initial cohort of 138 patients

- 78% had abnormal CXR on presentation

- 22% had normal initial CXR Early diagnosis important for this group for

prompt Tx and patient isolation

Wong et al. Radiology Aug 2003

The Chinese University of Hong KongPrince of Wales Hospital

Indication Diagnostic yield depends on level of clinical suspicion Initial cohort of 74 suspected patients

- 34 / 74 with relative minor symptoms - all had negative HRCT- subsequent proven not SARS

- 40 / 74 had positive HRCT- subsequent confirmed SARS

Wong et al. Radiology Aug 2003

The Chinese University of Hong KongPrince of Wales Hospital

Indication High clinical index of suspicion and negative

CXR High clinical index with equivocal CXR findings

(young female with dense breasts) Not recommended

- all patients with low clinical suspicion

- high suspicion with definite CXR changes

The Chinese University of Hong KongPrince of Wales Hospital

Suspected SARS

CXR

+ve

Treatment

-ve(if strong clinical suspicion)

HRCT

Treatment Follow-up

+ve -ve

The Chinese University of Hong KongPrince of Wales Hospital

Scanning Technique Initial outbreak – both conventional and HRCT

performed

Preliminary experience – lack of

lymphadenopathy or pleural abnormality

Current protocol – perform only HRCT

The Chinese University of Hong KongPrince of Wales Hospital

Scanning Technique Supine position

Full inspiration (shallow breathing if SOB)

1mm collimation, 6mm interslice gap

120 kV, 140mA, scan time of 1 second

Whole scanning procedure of ~ 1 minute

The Chinese University of Hong KongPrince of Wales Hospital

Scanning Technique High-spatial frequency reconstruction algorithm

Image viewed at lung window setting

- level: -700 HU

- width: 1500 HU

Close patient monitoring

Strict infection control measures

The Chinese University of Hong KongPrince of Wales Hospital

Imaging Features Appearances:

(initial cohort of 40 patients, 149 lesions)- Ground-glass opacification (68%)- Consolidation +/- GGO (32%)- Thickened intralobular interstitium (32%)- Thickened interlobular septa (24%)

(‘Crazy-paving’ appearances)- Associated bronchiectasis (7%)

Wong et al. Radiology Aug 2003

The Chinese University of Hong KongPrince of Wales Hospital

Imaging Features Location:

- Peripheral / subpleural (72%)

- Peripheral + central (20%)

- Pure central unusual (8%)

- Slight lower lobe predominance

- half patients with bilateral involvement

Wong et al. Radiology Aug 2003

The Chinese University of Hong KongPrince of Wales Hospital

Imaging Features Absence of following features

- peribronchovascular interstitial thickening

- mass / nodule

- lymphadenopathy

- pleural effusion

- cavitation

The Chinese University of Hong KongPrince of Wales Hospital

Reasons For Negative CXR Lesions at radiographic blind-spots

- Retrocardiac area

- Paraspinal area

- Posterior costophrenic sulcus

- Peri-hilar area

Early disease with small areas of ground-glass

opacification

The Chinese University of Hong KongPrince of Wales Hospital

Role In Follow-up Persistent CXR changes after discharge +

functional impairment necessitate HRCT

- assessment of nature of lung change (persistent alveolitis steroid / immune Tx

fibrosis irreversible, steroid not useful)

- extent of lung fibrosis

- interval HRCT – serial change after Tx

The Chinese University of Hong KongPrince of Wales Hospital

Follow-up Initial cohort of 24 discharged patients HRCT at ~ 37 days after admission 23/24 (96%) – persistent GGO 15/24 (62%) – HRCT evidence of fibrosis 9 had HRCT at initial presentation

- all had radiological improvement- residual GGO + interstitial changes

Antonio et al. Radiology Sep 2003

The Chinese University of Hong KongPrince of Wales Hospital

Follow-up HRCT evidence of fibrosis

- parenchymal band

- subpleural lines

- interlobular septal thickening

- honey-combing

- traction bronchiectasis

- architectural distortion

The Chinese University of Hong KongPrince of Wales Hospital

Follow-up Patients with HRCT evidence of fibrosis

- Older age group- Male > female- Longer hospital stay- Higher ICU admission rate- Higher peak LDH level- More requirement for pulse iv steroid

Antonio et al. Radiology Sep 2003

The Chinese University of Hong KongPrince of Wales Hospital

Limitations Small number of patients

Relatively short follow-up

- some HRCT changes may be reversible

No histology for confirmation of fibrosis

No correlation with lung function or objective

assessment of exercise tolerance

The Chinese University of Hong KongPrince of Wales Hospital

Take Home Messages HRCT useful for early diagnosis of SARS

Not suitable as 1st line investigation

Indication of HRCT for suspected SARS

- patients with high index of clinical suspicion

and negative / equivocal CXR findings

The Chinese University of Hong KongPrince of Wales Hospital

Take Home Messages HRCT features includes

- GGO +/- consolidation

- interstitial thickening

- peripheral / subpleural in location

- slight lower lobe predominance

- lack of cavitation, lymphadenopathy & pleural effusion

The Chinese University of Hong KongPrince of Wales Hospital

Take Home Messages HRCT useful in follow-up SARS patients with

functional impairment and persistent CXR changes

Preliminary experiences – significant proportion of discharged patients with HRCT evidence of fibrosis

Need longer FU study with more patients for further assessment