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A
new method has been invented to directly image the distribution
of electron emitting isotopes at very high resolution and
sensitivity, which will benefit microdosimetry studies
of radiopharmaceuticals, especially beta-emitting therapeutic
drugs. The method uses an ultra-thin phosphor, a monolayer
of 3-μm P47 phosphor powder deposited on 3-μm clear
Mylar foil, layered on radioactive objects to convert the kinetic en-
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ergy
of emitted electrons into light, which is then coupled
to a digital light sensor by optical coupling means. The
images of the fluorescent light patterns represent the isotope
distributions under study. Our group at the Center for Gamma-Ray
Imaging has completed a proof-of-concept prototype system
using a large-area low-noise CCD detector and various
large-aperture imaging lenses. When using optics at unit
magnification, the system has resolved the actual annular
shape of a 3-mm 100-nCi Y-90/Sr-90 β source,
ostensibly a point source. From the images, the spatial resolution
is measured at 60 μm, and the detection limit of this
source is about 185 disintegrations. |
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Besides β emissions,
the system is also very sensitive to other charged particles
such as positrons and conversion electrons from γ emitters.
When imaging samples in vitro, our system at unit magnification
can provide similar spatial resolution, sensitivity,
and linear response range to state-of-art digital autoradiography
systems using storage phosphors. The resolution is improved
further with optics at higher magnifications. |
Unlike
autoradiography, our system is capable of imaging small
animals in vivo. Our group has used the system to image
in vivo the 18-F-FDG uptakes in 3 types of tumors implanted
in dorsal |
skin
chamber on 3 mice respectively. The images also showed
the heterogeneity of FDG distribution inside a tumor
about 5 mm in spatial dimension. Due to the high sensitivity
of the system, we also demonstrated the dynamic
imaging of the 18-F-FDG utake
in tumor during a 1-hour period. |
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-
L.
S. Gobar, L. Chen, and H. H. Barrett, Evaluation
of a digital autoradiography system based on ultra-thin
phosphors and a CCD camera, 54th Annual Meeting
of the Society of Nuclear Medicine, Washington,
DC, June 2-6, 2007.
- L. Chen,
L. S. Gobar, G. D. Stevenson, A. F. Gmitro, and H. H.
Barrett, Electron imaging system using ultra-thin phosphor
film and a CCD camera for in vivo imaging, 54th Annual
Meeting of the Society of Nuclear Medicine, Washington,
DC, June 2-6, 2007
- L. Chen,
L. S. Gobar, G. D. Stevenson, A. F. Gmitro, and H.
H. Barrett, Electron imaging system using ultra-thin
phosphor film and CCD camera for in vivo imaging, presented
at Society of Nuclear Medicine 54th Annual Meeting,
Washington DC, Jun 2-6, 2007.
- L. S. Gobar,
L. Chen, and H. H. Barrett, Evaluation of a digital
autoradiography system based on ultra-thin phosphors
and a CCD camera, presented at Society of Nuclear
Medicine 54th Annual Meeting, Washington DC, Jun
2-6, 2007.
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