Histogram transformation for improved compression of CT images

Armando Manduca, Bradley J.M.D. Erickson, Kenneth R. Persons, Patrice M. Palisson

Research output: Chapter in Book/Report/Conference proceedingConference contribution


CT images represent a unique challenge for medical image compression; they have many pixels with very high and very low intensity values, often with sharp edges between the two, and the intensity values have quantitative significance, representing the attenuation coefficient in Hounsfield units (HU). Thus, the intensity ranges which represent bone or various soft tissues are essentially known in advance. When viewing a CT image, different window and level settings for mapping the 12-bit intensity values to an 8-bit display are used, depending on the objects of interest. When viewing objects with very high or low values, large window values are used, so that differences in intensity values on the order of 10 or 20 HU are not significant and are scarcely noticed in practice. Conversely, when viewing soft tissues, small windows are used to capture subtle but important distinction, and an intensity difference of 10-20 HU can be highly significant. CT compression schemes, therefore, should have a mechanism to increase the representation accuracy of intensity values corresponding to soft tissue relative to those corresponding to bone and air. We describe a simple technique to force compression algorithms to assign more importance to specific intensity ranges by transforming the histogram of the image prior to compression, and show sample results. The technique significantly increases the ratio by which the images can be compressed while retaining acceptable image quality at both large and small window settings in common clinical use.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
PublisherSociety of Photo-Optical Instrumentation Engineers
Number of pages8
ISBN (Print)0819424420
StatePublished - Dec 1 1997
EventMedical Imaging 1997: Image Display - Newport Beach, CA, USA
Duration: Feb 23 1997Feb 25 1997

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherMedical Imaging 1997: Image Display
CityNewport Beach, CA, USA

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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