High Resolution Detector Modules Based on NaI(T1) Arrays for Small Animal Imaging Page: 2 of 5
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B. R2487 PSPMT Based Setup
The R2487 is a crossed wire anode PSPMT which has
18X and 17Y anodes and an active ama of 76 mm x 76 mm.
The 12 stage parallel mesh dynode structure results in a gain
amplification factor of lx 10'. We have reduced the number d
channels to readout by connecting neighbor wire anodes into
eight anode sectors of six groups of two and two groups of
three for the X-anodes. For the Y-anode wires we have seven
groups of two neighbor anode wires connected and one group
of three connected together. The end result is that we have 8X
and 8Y anode sectors to readout.
Studies done with the R2487 were accomplished using the
same data acquisition system and image generation methods
as we have described elsewhere . Briefly, we make use of
LeCroy CAMAC FERA 4300B ADCs to digitize the
crosswire anodes of the R2487. The CAMAC system is
interfaced via a Jorway SCSI CAMAC crate controller to a
Machintosh G3 workstation. On the Macintosh we used the
Kmax data acquisition development package from Sparrow
C. H8500 PSPMT Based Setup
We have been evaluating a hybrid variant of the 2" square
flat panel H8500 PSPMT which has 64 anodes of the direct
output type. We will be publishing the complete results of
our evaluation at a future date. The H8500 PSPMT is a 12
stage metal dynode PSPMT with a gain factor of over 106
based on a technology similar to the one used in the current
generation of compact metal dynode Hamamatsu
R5900/R7600/R8520 PSPMTs with active photocathode
sizes of 22mm x 22mm. The sample H8500 had a factory-
installed high voltage divider and signal connectors for the
de-coupled 12th dynode output and for the 64 (8x8) 6 mm x
6 mm anode pads. A 0.1 mm thick p-metal shield was used
around the PSPMT to minimize effect of magnetic fields.
Additional in-house built printed circuit boards with
readout/amplifier circuitry were attached to the PSPMT
through the connectors installed at the back of the factory
package. The function of these readout boards is to amplify
and invert the dynode signal that is later used to produce a
trigger to the ADC data acquisition system; and to de-couple
the 64 channel anode pad readout into an 8 X-channel by 8
Y-channel sectorized readout.
The data acquisition system was built around a PC
computer using the WindowsNT operating system with a
single DATEL PCI 416L ADC card. This PCI computer
card is a sixteen channel, 12 bit simultaneous sample-and-
hold ADC card with 5 volts input amplitude range . The
KmaxNT development software package from Sparrow
Corporation was used to develop software to control the
acquisition. This control software generates an image by
processing the raw anode data on an event by event basis.
D. Data Acquisition System
To perform the studies with the two PSPMTs control
software developed with the Sparrow Corporation's data
acquisition development packages for Macintosh (Kmax) and
PC (KmaxNT) based computers was used to generate an
images by processing the ral
scintillation event. Determinatio
ray interaction in the scintillat
computing a truncated center
distribution on the X and Y at
This is achieved by using only t
anode wires in the calculation ti
minimal fraction of the sum of all
5 to 10%). We have found tha
center-of-gravity (COG) techniqu
use of the PSPMT array. Tl
processed image is discussed b
v PSPMT data for each
i of the position of gamma-
wr array is determined by
of gravity of the signal
iodes of the PSPMT array.
ie digitized signals of those
at have a predefined chosen
the anode signals (typically
the use of this truncated,
is essential to maximizing
e generation of the final
low in the results of I-125
III. TEST RESULTS
The performance of the 5 cm sc
scintillators in which each eleme
in dimension was measured for
gamma and x-ray emissions of
The Nal(TI) array was coupled tc
H8500 position sensitive photon
A. Results from Na-22 studies
The array of 1 mm x 1 mm
optically coupled to a 3" square I
Below in Fig. 1 is shown a
illuminating the face of the dete
rays from a Na-22 source. Als
obtained with Na-22 (511 and 12
136 keV) source from a single
scintillation pixel from the center
Fig. 1: Raw image (top) obtained w
separation of 1mm x Imm x Smm Nal(1
with Co-57 (bottom-left) and Na-22 (
1mm x 1mm x 5mm scintillation pixel fro
The scintillator array was a
PSPMT. Please see Fig. 2.
uare array of Nal(Tl) crystal
it is 1 mm x 1 mm x 5 mm
use with detection of the
Na-22, 1-125 and Tc-99m.
the Hamamatsu R2487 and
5 mm NaI(TI) pixels was
lamamatsu R2487 PSPMT.
flood image obtained by
:tor with 511 keV gamma-
shown are energy spectra
74 keV) and Co-57 (122 and
1 mm x 1 mm x 5 mm
LI PSPMT region.
th a Na-22 source showing the
1) pixels. Energy spectra obtained
iottom-right) source with a single
m the central PSPMT region.
[so tested with the H8500
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Weisenberger, A.G.; Wojcik, R.; Majewski, S. & Popov, V. High Resolution Detector Modules Based on NaI(T1) Arrays for Small Animal Imaging, article, November 1, 2001; Newport News, Virginia. (https://digital.library.unt.edu/ark:/67531/metadc717797/m1/2/: accessed April 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.