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Publications
2007 - 2006
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 2005
- 2004 - 2003
- 2002 - 2001
- 2000
1999 - 1994-98
- 1991-93 - 1980-90
- pre-1980 |
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562. Enhancing near-IR avalanche photodiodes
performance by femtosecond laser microstructuring
2007 Applied Optics Vol. (In press)
Myers RA, Farrell F, Karger AM |
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561. Design and performance of an EMCCD based detector
for combined SPECT/CT imaging
2005 IEEE Nuclear Science Symposium Conference Record,
(IEEE Cat. No.05CH37692C), 2179-2182, 2006
Nagarkar VV, Singh B, Shestakova I, Gaysinskiy V
Abstract
We have designed and developed a very high sensitivity detector
for near-simultaneous SPECT/CT imaging of small animals. The
detector is based on a back-thinned electron multiplying charge
coupled device (EMCCD) bonded to a fiberoptic window, and
optically coupled to a high resolution, high efficiency, very
thick microcolumnar CsI(Tl) scintillator via a fiberoptic
taper. In addition to the low noise and high spatial resolution
inherent to CCDs, the EMCCD provides controllable internal
gain, which minimizes read noise even when the device is operated
at high frame rates. This allows the detection of incident
gamma-ray/X-ray radiation with high spatial resolution and
enhanced signal-to-noise ratio (SNR). The use of thick microcolumnar
CsI(Tl) offers high detection efficiency for gamma -ray/X-ray
radiation while maintaining a high spatial resolution. This
combination of the EMCCD and the CsI(Tl) scintillator has
resulted in a unique detector that can be employed for near
simultaneous functional (SPECT) and anatomical (X-ray CT)
imaging at a reduced cost. The design and evaluation of the
detector are discussed in this paper.
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560. Feasibility of an EMCCD-based beta imaging probe
for radioguided surgery
2006 2005 IEEE Nuclear Science Symposium Conference Record
Vol.(IEEE Cat. No.05CH37692C) Page 4
Shestakova I, Stack BC Jr, Gaysinskiy V, Entine G, Nagarkar
VV
Abstract
We report on initial results of our new intraoperative
probe, capable of functioning in real time with high spatial
resolution and high sensitivity. This probe is based on a
combination of two novel technologies, an electron multiplying
charge coupled device (EMCCD) bonded to a microcolumnar CsI(Tl)
scintillator via a flexible fiberoptic. Our data demonstrates
that the probe can be used with such beta-emitting radiolabels
as /sup 18/F, /sup 131/I, and /sup 32/P. The basic design
of the probe and its evaluation using standard clinical phantoms
is presented. Also, the operational data obtained on swine
models is included to demonstrate the probe's efficacy in
practical procedures.
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559. Fast X-ray/gamma-ray imaging using electron multiplying
CCD-based detector
2006 Nucl Instrum Methods Phys Res Sect A Vol.563 Pages
45-48
Bradford BH, Gaysinskiy V, Miller BW, Nagarkar VV, Shestakova
I, Singh B
Abstract
New designs of electron multiplying charge coupled devices
(EMCCDs) combine superior spatial resolution and low noise
of a conventional CCD with the internal gain of an avalanche
photodiode (APD). The presence of internal gain not only enhances
the device sensitivity, but virtually eliminates the read
noise associated with current CCDs, even when the device is
read at very high frame rates of 100 frames per second or
higher. Thus, the EMCCDs can simultaneously provide very high
sensitivity and a high signal-to-noise ratio (SNR). At RMD
we are exploiting these properties of EMCCD for use in radionuclide
and X-ray imaging. Specifically, we have developed a system
that makes use of an EMCCD with 512 $MUL 512, 16 $MUL 16 $mu@m
pixels. Special fiberoptic reducers have been designed to
enhance the detector sensitive area. The system gain is software
selectable and may be varied from 1 to 1000. This paper describes
the detector design along with its $gamma@-ray/X-ray imaging
performance. a strong 2006 Elsevier B.V. All rights reserved.
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558. Development of a solid-state photomultiplier based
on an array of Geiger mode CMOS avalanche photodiodes
2006 Proc SPIE Int Soc Opt Eng Vol.6119 Augustine FL
Christian JF, Lawrence WG, Stapels C
Abstract
We report the development of a photon-counting solid-state
photomultiplier that consists of an array of Geiger mode CMOS
avalanche photodiodes (APDs). The detector is based on the
design described by Buzhan et. al./sup1/ in which the individual
outputs of an array of Geiger APDs are coupled together to
drive a common output signal. The total output signal is a
sum of the Geiger outputs of each individual pixel in the
array. For a large array, the sum of the signals from the
discrete pixels produces an analog representation of the flux
on the detector. In this report we describe our most recent
measurements of the spectral response and noise characteristics
of the individual detector elements. We present results for
a 14 element array of Geiger mode pixels that is used as a
solid state photomultiplier (SSPM). We use this SSPM to create
a prototype radiation detector that can identify the source
based on the energy of the emitted radiation.
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557. A 16-channel avalanche photodiode detector array
for visible and near-infrared flow cytometry
2006 Progr. Biomed. Opt. Imaging Proc. SPIE Vol.6088
Christian JF, Farrell R, Lawrence WG, Poedniesinski E, Stapels
C, Tario JD Jr, Wallace PK
Abstract
We report on the development and application of a flow cytometer
using a 16-channel avalanche photodiode (APD) linear detector
array. The array is configured with a dispersive grating to
simultaneously record emission over a broad wavelength range
using the 16 APD channels of the linear APD array. The APD
detector elements have a peak quantum efficiency of 80% near
900 nm and have at least 40% quantum efficiency over the 400-nm
to 1000nm wavelength range. The extended red sensitivity of
the detector array facilitates the use of lower energy excitation
sources and near IR emitting dyes which reduces the impact
of autofluorescence in signal starved measurements. The wide
wavelength sensitivity of the APD array permits the use of
multiple excitation sources and many different fluorescent
labels to maximize the number of independent parameters in
a given experiment. We show the sensitivity and linearity
measurements for a single APD detector. Initial results for
the flow cytometer with the 16-element APD array and the 16-channel
readout ASIC (application specific integrated circuit) are
presented.
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556. Characterization of a CMOS Geiger photodiode pixel
2006 IEEE Trans. Electron Devices Vol.53 Pages 631-635
Augustine FL
Christian JF, Lawrence WG, Stapels C
Abstract
This paper examines the performance of CMOS avalanche photodiode
pixels operated in a Geiger mode. The pixels, called Geiger
photodiode (GPD) pixels, convert an incident analog photon
flux into a digital count rate. The maximum detection efficiency
of the characterized GPD pixel for 632-nm light is 22%. The
passively quenched GPD pixel exhibits an after pulsing at
excess bias voltages above 2 V, and a minimum in the after-pulsing
correction factor, of 0.53, occurs at an excess bias of 5.8
V. The after pulsing increases the fluctuations, or noise,
in the count-rate signal. The following expression accurately
describes the noise in the characterized GPD pixel, which
exhibits a relatively low after-pulsing probability: $delta/sup2/
= n$OBAR/subdp/ + n$OBAR/subap/ + 2 $DOT n$OBAR/subdp/ $DOT
n$OBAR/subap/ /sup1/2/, where $delta represents the count-rate
fluctuations, the "dp" subscript stands for "detected photons,"
the "ap" subscript stands for "after pulses," and the n$OBAR
represents the "average count rate of" dp, or ap. The noise-equivalent
illumination exhibits a minimum of 300 Hz at an operating
voltage of 28 V. The best operating voltage for the GPD pixel
increases from 28 V with increasing signal intensity. n the
sys 2006 IEEE.
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555. A CCD-based detector for SPECT
2006 IEEE Trans Nucl Sci Vol.53 Pages 54-58
Barber W, Entine G, Gaysinskiy V, Hasegawa B, Nagarkar VV,
Shestakova I, Singh B, Tipnis SV
Abstract
We are investigating the use of a CCD for high-resolution
radionuclide imaging. The use of a CCD has the potential to
provide very high spatial resolution on the order of 200 to
400 $mu@m, while significantly simplifying the readout electronics.
The detector is based on a special CCD with on-chip multiplication
gain that allows high-speed operation while maintaining the
read noise at a very low level of $LS@1 electron. To achieve
high detection efficiency and excellent spatial resolution
for incident gamma flux, a specially fabricated thick microcolumnar
CsI(TI) scintillator was optically coupled to the CCD. A prototype
SPECT imaging system was assembled by incorporating pinhole/parallel
hole collimators in the design. The use of this system for
radionuclide imaging has been demonstrated through tomographic
imaging of a test phantom filled with /sup99m/Tc. Although
2006 IEEE.
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554. Bridgman growth of LaBr/sub3/:Ce and LaCl/sub3/:Ce
crystals for high-resolution gamma-ray spectrometers
2006 J Cryst Growth Vol.287 Pages 239-242
Cirignano L, Glodo J, Gupta T, Higgins WM, Klugerman M, Shah
KS, Van Loef E, Wong P
Abstract
Single crystals of LaBr/sub3/:Ce and LaCl/sub3/:Ce have been
grown by the vertical Bridgman technique. Crystals of these
scintillators are used in the fabrication of high-resolution,
gamma-ray spectrometers. The LaBr/sub3/:Ce and LaCl/sub3/:Ce
crystals we have grown have high light outputs of similar
to 80,000 and 50,000 photons/MeV, respectively, and fast principal
decay constants of $LS@30 ns. The emission wavelength for
the LaBr/sub3/:Ce and LaCl/sub3/:Ce scintillators are $lambda@max=360
and 350 nm, respectively. Both materials have excellent energy
resolutions of similar to 3% FWHM for 662 keV photons at room
temperature. In this paper, we will report on our results
to date for vertical Bridgman crystal growth and characterization
of Ce-doped LaBr/sub3/ and LaCl/sub3/ crystals. We will also
describe the handling and processing procedures developed
for these oxygen and moisture sensitive materials. COPYRIGHT
2005 Elsevier B.V. All rights reserved.
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553. Depth of interaction resolution measurements for
a high resolution PET detector using position sensitive avalanche
photodiodes
2006 Phys Med Biol Vol.51 Pages 2131-2142
Yang Y, Dokhale PA, Silverman RW, Shah KS, McClish MA, Farrell
R, Entine G, Cherry SR
Abstract
We explore dual-ended read out of LSO arrays with two
position sensitive avalanche photodiodes (PSAPDs) as a high
resolution, high efficiency depth-encoding detector for PET
applications. Flood histograms, energy resolution and depth
of interaction (DOI) resolution were measured for unpolished
LSO arrays with individual crystal sizes of 1.0, 1.3 and 1.5
mm, and for a polished LSO array with 1.3 mm pixels. The thickness
of the crystal arrays was 20 mm. Good flood histograms were
obtained for all four arrays, and crystals in all four arrays
can be clearly resolved. Although the amplitude of each PSAPD
signal decreases as the interaction depth moves further from
the PSAPD, the sum of the two PSAPD signals is essentially
constant with irradiation depth for all four arrays. The energy
resolutions were similar for all four arrays, ranging from
14.7% to 15.4%. A DOI resolution of 3-4 mm (including the
width of the irradiation band which is approximately 2 mm)
was obtained for all the unpolished arrays. The best DOI resolution
was achieved with the unpolished 1 mm array (average 3.5 mm).
The DOI resolution for the 1.3 mm and 1.5 mm unpolished arrays
was 3.7 and 4.0 mm respectively. For the polished array, the
DOI resolution was only 16.5 mm. Summing the DOI profiles
across all crystals for the 1 mm array only degraded the DOI
resolution from 3.5 mm to 3.9 mm, indicating that it may not
be necessary to calibrate the DOI response separately for
each crystal within an array. The DOI response of individual
crystals in the array confirms this finding. These results
provide a detailed characterization of the DOI response of
these PSAPD-based PET detectors which will be important in
the design and calibration of a PET scanner making use of
this detector approach.
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