Clinical applications of computed tomography ray sum imaging in chest imaging.

Abstract

Learning Objectives: Ray Sum imaging (RSI) is a post processing technique to create a radiograph-like image from the routine Computed Tomography (CT) dataset. The aim of this educational exhibit is to review its applications in Chest imaging. Background(s): A ray sum image derived from CT is created by casting 'rays' through its dataset and adding voxel attenuation values along the path of the ray. Coronal and sagittal images created using this technique are comparable to frontal and lateral digital radiographs. This ray sum image can be used for cross modality comparison and as a baseline image for longitudinal imaging follow-up. Imaging Findings or Procedural Details: Previously published literature has established superior RSI image quality compared to CT scanogram and described clinical application in imaging of urolithiasis. The reconstruction technique requires no additional radiation dose and can be performed retrospectively. Reconstruction tools are relatively simple to use and are not vendor specific. This pictorial review presents the clinical benefits of RSI created from CT Chest that could be used as baseline imaging in clinical scenarios that normally require follow-up Chest Radiographs or comparison with previous chest radiographs. Illustrative clinical applications include chest infection, lung collapse, benign and malignant pulmonary masses, interstitial lung disease, pleural effusion/collection, pulmonary infarction and medical device positioning. Conclusion(s): RSI, as a post processing CT technique, has a comparable imaging quality to a Chest radiograph and can replace the need of an additional CXR that is routinely performed for follow up or comparison purposes in a number of chest conditions. This can improve cross modality comparison between CT and plain radiographs as well as minimising the radiation burden to patients who may require repeated imaging as part of longitudinal follow-up.