Ray Sum imaging (RSI) is a post processing technique that creates 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.

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. This can usually be created within few seconds. 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.

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. Pulmonary Tuberculosis A 38 year old male recent migrant to Australia presented with haemoptysis on a background of 2 month history of non-productive cough and increasing...

Ray sum image is a simple post processing technique of the routinely acquired CT dataset allowing creation of a radiograph‐like image which can be used as a base-line image for comparison if patients require follow-up radiographs in a variety of clinical radiology settings, including a wide range of chest conditions. This removes the requirement of performing additional radiographs post CT, and therefore, reduces the radiation burden to the population.

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