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Application & Imaging Features of SARS on HRCT. KT Wong. Department of Diagnostic Radiology and Organ Imaging Chinese University of Hong Kong Prince of Wales Hospital Hong Kong. Background. Outbreak in medical ward in PWH in March - PowerPoint PPT Presentation
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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