University of Wisconsin–Madison

About the PET Scanner

PET Scanner

The laboratory houses a complete PET research facility, complementing the previously established PET research labs under the Medical Physics department. The scanning facilities consist of a Siemens ECAT EXACT HR+ PET scanner and its adjacent control room, subject prep room, and blood metabolite analysis lab. A dedicated particle accelerator (see below) and radiochemistry lab support the imaging experiments. The PET scanner room is also equipped with a positional computer monitor for performing computer tasks during the acquisition of the scans.

The EXACT HR+ scanner consists of 4 detector rings of 72 BGO blocks per ring. Each block contains an 8 x 8 array of discrete detector elements with dimensions of 4.39 x 4.05 x 30 mm3, providing 63 contiguous 2-D image planes through an axial field of view (FOV) of 15.5 cm and a patient port diameter of 56.2cm. The rings are separated by extendable tungsten septa for acquisition in both 2D and 3D modes. The transaxial intrinsic resolution of this scanner is 4.3 mm FWHM, and axial intrinsic resolution is 4.7 mm FWHM in the center of the field of view. Reconstructed spatial resolution for a head-shaped object is in a nearly isotropic resolution of 6mm FWHM throughout the entire region of the brain.

Data acquisition and processing is performed using the ECAT v7.2.2 software. For most research brain imaging applications, the data are acquired in 3D mode following a 3 minute transmission scan in 2D mode. The data are reconstructed using either filtered back projection or iterative algorithms, using brain mode sinogram trimming, zoom = 2.8, and a 4mm Gaussian filter to a reconstructed image of 128 x 128 x 63 voxel matrix (pixel size = 1.84mm x 1.84mm x 2.43mm ). The reconstructed data are also corrected for the attenuation of annihilation radiation (using segmented attenuation maps), scanner normalization and scatter radiation.

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