Publication: Depth identification accuracy of a three layer phoswich PET detector module
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1999-06
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Tutors
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IEEE
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Abstract
We describe a PET detector module that provides three
levels of depth-of-interaction (DOI) information. The detector
is a 9 x 9 array of 2 mm x 2 mm x 12 mm deep phoswich
crystal elements, each consisting of 4 mm long LSO (entrance
layer), GSO (middle layer) and BGO (exit layer) crystals
joined optically together end-to-end. The BGO exit layer is
directly coupled to a miniature position-sensitive photomultiplier
tube (PSPMT). Delayed charge integration, a method
that exploits differences in the light decay times of these
scintillators, is used to determine the layer-of-interaction.
DO1 accuracy, measured by scanning a slit source of 5 1 1 keV
radiation along the length of the module was 86% for the LSO
layer, 80% for the GSO layer and 84% for the BGO layer.
Energy resolution at 511 keV was 19% for LSO, 21% for
GSO and 40% for BGO. Apparent gain differed between
layers in the ratios 2.7: 1.9: 1 .O (LS0:GSO:BGO). Crystal
separation was good between crystals in the LSO layer,
acceptable between crystals in the GSO layer and poor
between crystals in the BGO layer due, primarily, to the
pronounced spatial non-linearity of the PSPMT. The delayed
charge integration method, however, does appear suitable for
obtaining multi-level depth information when DO1 effects are
particularly significant, e.g. in very small ring diameter PET
scanners for small animal imaging.
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IEEE Transcations on Nuclear Science, vol. 46, n. 3, jun. 1999. Pp. 485-490