From Ionizing Radiation Detectors For Medical Imaging

8.4 Image Reconstruction

The aim of PET image reconstruction is to achieve an image of the activity distribution within the patient from the recorded sets of acquired data. In a tomographic study, data are acquired by performing several sets of linear scannings of the examined slice at different angles: each set gives an activity profile. The acquired profiles are then used to generate an appropriate number of independent equations to mathematically solve, where the unknowns are the activity elements of a grid (the image matrix).

In 2D, the image matrix elements are called pixels, and each slice is a plane, without thickness. The number of detected events in a LOR is the sum of activity along the line of scanning in the plane ( line integral), and the activity is uniform in each pixel (the value associated to the pixel is the mean activity). In addition, the reconstruction program considers the resolution and sensitivity as independent from the depth of the annihilation event. The reconstruction should include a method for attenuation correction. In 3D-MS ( multi-slice), the image is obtained by simply overlapping 2D images of adjacent slices, therefore the assumptions used are the same. In 3D-PVI ( volume imaging), the slice thickness is considered and voxels ( volume elements) substitute pixels: the uniformity assumption is then true for the voxel.

A profile or a line integral does not contain the information on the depth of the annihilation events. An attempt to recover this information...

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Topics of Interest

8.5 Correction and Normalization Procedures 8.5.1 Attenuation Ideal PET imaging requires that neither of the annihilation photons undergo any interaction in the biological tissue. By neglecting the...

R.M. Leahy, University of Southern California R. Clackdoyle, CNRS, France 1 Introduction The term tomography refers to the general class of devices and procedures for producing two-dimensional (2D)...

In this chapter we will deal with the mathematical basis of tomography with nondiffracting sources. We will show how one can go about recovering the image of the cross section of an object from the...

Iterative methods for reconstructing images have been studied for decades. Because many of these methods, such as the EMML, are slow to converge, particularly for the large data sets typical of modern...

18.1   INTRODUCTION In the second part of computerized imaging involving Fourier-related transforms, image reconstruction from projections including tomography is discussed. The fundamental...