Magnetic resonance imaging of the thorax in the evaluation of asbestosis

The purpose of the study was to evaluate the accuracy of magnetic resonance imaging (MRI) in detecting subclinical morphological changes caused by asbestos exposure. Conventional chest radiographs according to the International Labour Organisation (ILO) categories 0-11 and spirometric data were compared with MRI in 17 men with mean (+/-2SD) asbestos exposure time of 24.6+/-13.0 yrs. Mean age was 62.0+/-9.4 yrs. The inclusion criterion was an ILO score of 2 or more. Electrocardiographic registrations and antirespiratory movement artefact techniques were used in all MRI examinations to avoid movement artefacts. Mean ILO grading was found to be 7.7+/-3.8 on chest radiography and 9.8+/-2.0 with MRI (p=0.01). Five patients had a higher ILO stage as evaluated by MRI, but in nine patients the staging remained unchanged. MRI revealed mediastinal adenopathy in four patients. Forced expiratory volume in one second (expressed as a percentage of the predicted value) was negatively correlated with ILO score as assessed by MRI (r=-0.4, p=0.032). Magnetic resonance imaging seems to be more sensitive than conventional radiographs in detecting subclinical fibrosis as well as the extent of pleural asbestosis.