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Computed Tomography Image Manipulation

Learn about the techniques used in computed tomography image manipulation to enhance the visibility of useful information while suppressing non-useful information. Discover how windowing, image manipulation, and specialized programs can improve the interpretation of CT images.

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Computed Tomography Image Manipulation

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  1. Computed Tomography Image Manipulation

  2. Image Manipulation Defined • “Techniques (operations) or processes which modify an image to enhance visibility of useful information while suppressing ‘noise’ or non-useful information” • No additional or new information produced • Content of interest emphasized • Overall information content reduced

  3. Windowing • Manipulation of image gray scale using image’s CT numbers

  4. Window Width & Level WL WW • Contrast visible only for pixel values within selected window. • All CT #’s below/above window will be all white or all black & display no contrast.

  5. Window Width & Level • Window width • range of CT #’s displayed • Window level • center or midpoint of CT # range CT #’s WL WW

  6. Advantage of Windowing • Possible to display & enhance contrast in selected segments of total CT # range

  7. CT Image Manipulation • Magnification • Distance angle measurement • Region of interest (ROI) analysis • Rectangular • Circular • Values • Average CT # • Standard deviation • Area

  8. Histogram Analysis • # pixels with particular range of values • graph of CT # frequency • can apply to • ROI • entire image

  9. Specialized CT Image Manipulation Programs • Multiplanar reconstruction • 3D reconstruction • Quantitative CT • Osteo CT / bone densitometry • Xenon CT • Radiation therapy treatment planning using CT data

  10. Multiplanar Reconstruction • Creates non-axial images from stack of contiguous transverse axial scans • stack contains 3 dimensional CT data • pixels identified & selected from each axial slice

  11. Cuts • coronal • sagittal • paraxial • oblique

  12. Coronal Reconstruction Example Stack of Axial Slices Reconstructed Slice

  13. Coronal Reconstruction Example Reconstructed Slice Stack of Axial Slices

  14. Sagittal Reconstruction Example Reconstructed Slice Stack of Axial Slices

  15. Oblique Reconstruction Example Reconstructed Slice Stack of Axial Slices

  16. CT Applications • Angiography • Multimodality Image Fusion • PET/CT • Overlaying of images of various modalities • One anatomical (CT), one functional (Nuc med)

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