Reuven Shreiber MD, Presenter: Employee, Algotec Limited

Guy Engelhard PhD, Abstract Co-Author: Employee, Algotec Limited

Tiferet A. Gazit MSc, Abstract Co-Author: Employee, Algotec Limited

Roni Shreter MD, Abstract Co-Author: Nothing to Disclose

Doron Fischer BSc, MD, Abstract Co-Author: Nothing to Disclose

Luda Goralnik, Abstract Co-Author: Nothing to Disclose

Imaging data sets such as CT, MRI and PET are characterized by a highly dynamic range of pixel values, which must be reduced for the purpose of display. Regular windowing processes cover only a fraction of the dynamic range, which renders it necessary to use several different sets of windowing procedures for the reading of a single study. In chest CT images, for example, the user has to use three separate sets of windowing levels: bone, mediastinum and lung windows in the same reading. Several filters have been used in the past in an attempt to locally enhance the contrast while incorporating all of the required windowing operations into a single set. These methods are based on High Dynamic Range (HDR) imaging but are not clinically employed because the output has been too different from the images to which radiologists are used. A new method is suggested whereby segmentation of the main organs in a CT scan is performed, and several windows are assigned to a single image according to the various organs being shown on screen. For example, if a lung and bone segmentation is generated, the application assigns a lung window to the lung , a bone window to the bone and a body window to the rest (see figure).  

Several examples of CT studies, including dual energy ones, were tested by 4 experienced radiologists. After segmentation of the main organs in the study the windowing procedure was applied using different window settings for each of the organs. This yielded an MRI appearance to the read images. The results were viewed by the radiologists.  

When viewing abdomen, lung and bone windows on a unified view, an ’MRI-like appearance’ was observed and accepted by all radiologists as a satisfactorily familiar view.

While in HDR and other filter-type methods used in the past in an attempt to apply the same filtering to the entire image the resulting image did not present characteristics radiologists expected to see, the proposed method yields images possessing characteristics with which radiologists are familiar. This results from the fact that the windowing settings applied to the various organs in the image are standard windowing levels and widths using the familiar linear mappings in each region.

The proposed organ-specific windowing is expected to provide a faster viewing of CT and MRI studies with minimal need for manual windowing operations.

Shreiber, R, Engelhard, G, Gazit, T, Shreter, R, Fischer, D, Goralnik, L, Organ-specific Windowing: Providing CT Images with an "MRI Look" for Faster Interpretation of CT Studies.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002646.html