Role of imaging in evaluation of lung involvement in severe acute respiratory syndrome (SARS)

Abstract

Diagnostic imaging played a substantial role in the management and treatment of

patients during the Severe Acute Respiratory Syndrome (SARS) outbreak when daily

chest radiographs were performed as a measure of disease severity and respiratory

status. This thesis was performed to address several issues relating to the

radiological spectrum of SARS, its temporal pattern on chest radiograph and high

resolution computed tomography (HRCT) during the course of disease, and

relationships between severity of opacities quantified on chest radiographs and

clinical parameters including treatment response. Radiological parameters that could

discriminate SARS from non-SARS community-acquired pneumonia (CAP) were

also studied.

Unifocal unilateral ground glass opacities was the dominant radiographic abnormality

at presentation that progressed rapidly to maximal disease within 9.35 ± 4.09

(median 9, range 3-21) days after onset of symptoms with bilateral consolidation in

62.5% of patients. Complete resolution and significant residual disease was noted in

50% and 20% of cases respectively at end of assessment period. There was a

temporal pattern of lung abnormalities on HRCT with ground glass opacity and

consolidation at presentation. Reticulation developed after the first week and was

present in 50% of patients at ?four weeks. HRCT was useful in illustrating

parenchymal abnormalities in patients with normal radiographs at presentation.

Severity of lung abnormalities quantified on chest radiograph at different time points

of disease correlated with clinical and laboratory parameters such as SaO2 and liver

transaminases ALT and AST. Significant relationships were also found between

radiographic parameters, and O2 supplementation and treatment response. There

are discriminating differences in the radiographic pattern, rate of radiographic

progression, and zone of involvement between SARS and non-SARS CAP.