Computed Tomography Image Manipulation Image Manipulation Defined Techniques

Computed Tomography Image Manipulation

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

Windowing Manipulation of image gray scale using image’s CT numbers

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.

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

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

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

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

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

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

Cuts coronal sagittal paraxial oblique

Coronal Reconstruction Example Stack of Axial Slices Reconstructed Slice

Coronal Reconstruction Example Stack of Axial Slices Reconstructed Slice

Sagittal Reconstruction Example Stack of Axial Slices Reconstructed Slice

Oblique Reconstruction Example Stack of Axial Slices Reconstructed Slice

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