Comparison of conventional chest x ray with a novel projection technique for ultra‐low dose CT

Purpose To compare a novel thick‐slab projection technique for ultra‐low dose computed tomography (CT; thoracic tomogram) with conventional chest x ray with respect to 13 diagnostic categories. Methods With the approval of the institutional ethics board, a dataset was retrospectively collected of 22 consecutive patients who had undergone a clinically requested emergency room conventional chest x ray (CXR) and a same‐day standard‐of‐care non‐contrast CT. Scanner specific noise was added to the CT images to simulate a target dose of 0.18 mSv. A novel algorithm was used to post‐process CT images as coronal isotropic reformats by applying a voxel‐based, locally normalized weighted‐intensity projection to generate 2 cm thick slabs with 1 cm overlap. Three chest radiologists with no prior training for the study reviewed the CXR and thoracic tomogram for each case and assessed each diagnostic category (pneumonic infiltrates, pulmonary edema, interstitial lung disease, nodules > 5 mm, nodules