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...

Products & Services
CCD Image Sensors
Charged coupled device (CCD) image sensors are electronic devices that are capable of transforming a light pattern (image) into an electric charge pattern (an electronic image).
Video Cameras
Video cameras record live-action scenes that are available for viewing via a stored or transmitted video feed. This allows the user to create a permanent and detailed chronicle of events. Video cameras record dozens of pictures (or frames) a second that when viewed in succession, clearly distinguish the translation of an object or person over time.
Low Light Cameras
Low light cameras are a type of video camera with extreme photon sensitivity, and are excellent for recording in situations where only ambient levels of light are available. Common deployments include overnight surveillance and remote machine monitoring.
CMOS Cameras
Complementary metal oxide semiconductor (CMOS) cameras use image sensors that operate at lower voltages than charged coupled devices (CCDs), reducing power consumption for portable applications. Each CMOS active pixel sensor cell has its own buffer amplifier, and can be addressed and read individually. 
Frame Grabbers
Frame grabbers are image processing computer boards that capture and store image data for industrial applications such as quality control.

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...

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

Chapter List Color Plates: Color Plates Plate 1: The horizon slice is a time structure surface generated by automatic event picking in the seismic data volume. Shown here are various perspective...