Comparison of the Ultra-low-dose Veo Algorithm With the Gold Standard Filtered Back Projection for Detecting Pulmonary Asbestos-related Conditions

Asbestos-exposed workers will be recruited following referral to our radiology department for the evaluation of asbestos-related disease. CT examinations will be performed with a 64-slice CT system (Discovery CT 750HD; GE Healthcare, Milwaukee, WI) and will consist of two successive acquisitions. Each examination, the normal-dose (FBP acquisition) and ultra-low-dose (Veo acquisition) spiral CT, will be performed in supine position, on the entire thorax, at full inspiration and without contrast agent injection.

In order to perform the two acquisitions without increasing radiation, standard acquisition will be performed with the same kV with mA equal to patient's body weight minus 10. To conserve image quality, 60 mA will be the inferior limit. The other CT parameters will be rotation time 0.5 s and pitch 1.375. Image data will be reconstructed with FBP algorithm.

The Veo acquisition will be performed with constant CT parameters including: a tube voltage of 100 kV, a tube current of 20 mA, pitch of 0.984 and rotation time 0.4 s. Image data will be reconstructed with the Veo algorithm.

Each CT acquisition will be viewed independently by two experienced radiologists (2 to 7 years of experience). The low-dose images with Veo reconstruction will be interpreted before the standard CT and on separate weeks to minimize recall bias. Then, the more experienced radiologist will evaluate the detection and characterization of pleuroparenchymal abnormalities by a second and simultaneous reading of the Veo and FBP acquisitions. Because FBP images are benchmark practice, when a lesion will be found only on Veo images, it will be regarded as a false positive.

The following asbestos-related pleural and parenchymal abnormalities will be recorded as present or absent. Pleural abnormalities considered will be: pleural plaques, diffuse pleural thickening and pleural effusion.

CT features of asbestosis will include subpleural dots and branching opacities, curvilinear subpleural lines, areas of ground glass opacities, septal lines, reticulations and honeycombing.

Presence of nodules will also be recorded. We will note for each abnormality: localization (side, table position) and nature (non-solid, part-solid, solid or calcified).