In this situation, HRCT is clearly superior. The normal pleural line as seen on HRCT is 1-2 mm and is composed of the visceral and parietal pleura, the endothoracic fascia, and, the at times, the innermost intercostal . A layer of fat, vessels, and nerves separate the innermost intercostal from the internal and external intercostals. In the paravertebral area, the innermost intercostal is absent, and the ple ural line is almost imperceptible. Any soft tissue density internal to the central portion of a rib is abnormal.
Asbestosis refers to fibrosis of the lung parenchyma itself.
The disease is most severe in the posterior, lower zones of the lungs. Once inhaled, the asbestos fibers deposit in the respiratory bronchioles and alveolar ducts. It is here in the peribronchiolar area of the lung that fibrosis begins . As the disease progresses, there is involvement of the adjacent alveoli. Patients are rarely symptomatic before 15 years from the time of initial exposure.