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Image Reconstruction

Collimated Beam Paths. Reconstructed images from PET, SPECT, and CT are all based on collimated beams directed through the target: the basic data consist of measurements of the absorption of x-rays (CT) or concentrations of radioactive material (PET and SPECT) along a known beam path. From this

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Image Reconstruction

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    1. Image Reconstruction The algorithms used for image reconstruction depend on the modality. In magnetic resonance imaging (MRI), reconstruction techniques are fairly straightforward, requiring only a two-dimensional inverse Fourier transform (described later in this chapter). Positron emission tomography (PET) and computed tomography (CT) use projections from collimated beams and the reconstruction algorithm is critical. The quality of the image is strongly dependent on the image reconstruction algorithm

    2. Collimated Beam Paths Reconstructed images from PET, SPECT, and CT are all based on collimated beams directed through the target: the basic data consist of measurements of the absorption of x-rays (CT) or concentrations of radioactive material (PET and SPECT) along a known beam path. From this basic information, the reconstruction algorithm must generate an image of either the tissue absorption characteristics or isotope concentrations. The mathematics are fairly similar for both absorption and emission processes and will be described here in terms of absorption processes; i.e. CT.

    3. X-Ray Absorption In CT, the intensity of an x-ray beam is dependent on the intensity of the source, Io, the absorption coefficient, , and length, R, of the intervening tissue:

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