| 摘要 |
A universal nuclear medicine imager (UNMI) enables planar, SPECT and PET studies. The UNMI is a "position sensitive" type of detector which has a relatively thick (e.g., {fraction (6/8)} in.) NaI(TI) crystal optically divided by a thin non-scintillating material into two half-thicknesses of ⅜ in. each. The UNMI detector uses a light collimator system to enable a depth of interaction (DOI) determination in addition to a two-dimensional location of gamma photons in the half-thicknesses of the crystal. The system includes a combination of a scintillating, optically more dense material with a non-scintillating, optically less dense material and uses the light refraction reflection law with PM tubes and coincidence circuits. For obtaining the optimal spatial resolution in planar and SPECT studies, a known DOI enables the use of only the lower ⅜ in. of the crystal (energies up to 150 KeV) or both of the half-thicknesses for medium energies (250, 360 KeV), with the resolution in each being corrected by use of digital filters. In PET detection of 511 KeV energies, a known DOI improves the resolution by correcting for parallax error in addition to the use of an adequately thick crystal.
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