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 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. WW WL

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

6 Advantage of WindowingPossible to display & enhance contrast in selected segments of total CT # range

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

8 Histogram Analysis # pixels with particular range of valuesgraph of CT # frequency can apply to ROI entire image

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

10 Multiplanar ReconstructionCreates 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 ExampleStack of Axial Slices Reconstructed Slice

13 Coronal Reconstruction ExampleStack of Axial Slices Reconstructed Slice

14 Sagittal Reconstruction ExampleStack of Axial Slices Reconstructed Slice

15 Oblique Reconstruction ExampleStack of Axial Slices Reconstructed Slice

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