Development of a high-resolution YSO gamma camera system that employs 0.8-mm pixels.
OBJECTIVE
YSO (Ce-doped Y₂SiO₅) is a promising scintillator for a single-photon imaging system since it has relatively high light output and does not contain any natural radioactivity. Since YSO is not hygroscopic, it may be possible to fabricate a block with small pixels for a high-resolution system. For this purpose, we developed a high-resolution gamma camera system that employs smaller than 1-mm YSO pixels.


METHODS
The gamma camera's detector used 0.8 × 0.8 × 7-mm YSO pixels. All the surfaces of these YSO pixels were mechanically polished, combined with a 0.1-mm-thick BaSO4 reflector to form a 48 × 48 matrix, and optically coupled to a high quantum efficiency, 2-inch square position sensitive photomultiplier tube (Hamamatsu Photonics H10966 A-100). The YSO block was 43.2 × 43.2 mm. The YSO gamma camera was encased in a 5-mm-thick tungsten container, and a parallel collimator was mounted on its front. The parallel hole collimator was made of a 3-layer (each layer was 5-mm thick) tungsten plate, and each plate had 48 × 48, 0.6-mm holes that were positioned by one-to-one coupling with the YSO pixels.


RESULTS
Even with the 0.8-mm YSO pixels, we clearly resolved most of the pixels in a 2-dimensional histogram with a peak-to-valley ratio of 2.9 for the 122-keV gamma photons. The energy resolution was 20.4% FWHM. The spatial resolutions with a parallel hole collimator 2 mm from the collimator surface were 0.7- and 1.3-mm FWHM for the 122- and ~35-keV gamma photons, respectively. We successfully obtained phantoms and small animal images with our YSO gamma camera system.


CONCLUSIONS
Our high-resolution system has a potential to be useful for molecular imaging research.
Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, 1-1-20 Daiko-Minami, Higashi-ku, Nagoya, 461-8673, Japan, s-yama@met.nagoya-u.ac.jp.
Seiichi
S
Yamamoto
Hiroshi
H
Watabe
Yasukazu
Y
Kanai
Katsuhiko
K
Kato
Jun
J
Hatazawa
D000818:Animals; D002563:Cerium / Q000737:chemistry*; D004867:Equipment Design; D015902:Gamma Cameras; D008027:Light; D019047:Phantoms, Imaging; D051381:Rats; D013669:Technetium Tc 99m Medronate / Q000031:analogs & derivatives; D015019:Yttrium / Q000737:chemistry*
D002563:Cerium; D015019:Yttrium; C024226:technetium Tc 99m hydroxymethylene diphosphonate; C091417:yttria; D013669:Technetium Tc 99m Medronate