Department of Diagnostic Radiology and Organ Imaging Chinese University of Hong Kong Prince of Wales Hospital Hong Kong KT Wong Application & Imaging Features of SARS on HRCT

The Chinese University of Hong Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince of Wales Hospital Suspected SARS CXR +ve Treatment -ve (if strong clinical suspicion) HRCT Treatment Follow-up +ve -ve

The Chinese University of Hong Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince of Wales Hospital Imaging Features  Absence of following features - peribronchovascular interstitial thickening - mass / nodule - lymphadenopathy - pleural effusion - cavitation

The Chinese University of Hong Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince 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 Kong Prince of Wales Hospital Take Home Messages  HRCT useful for early diagnosis of SARS  Not suitable as 1 st 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 Kong Prince 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 Kong Prince 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