J04: Joint NSS/MIC 4
Tuesday, Oct. 27 16:00-18:00;
in International Ballroom North
J04-1: (16:00) The Digital Silicon Photomultiplier - A Novel Sensor for the
Detection of Scintillation Light
C. Degenhardt, G. Prescher, T. Frach, R. de Gruyter, A. Schmitz, R. Ballizany
Philips Corporate Technologies, Aachen, Germany
Silicon Photomultipliers (SiPMs), arrays of avalanche photodiodes operated in Geigermode, are attractive alternatives to Photomultiplier Tubes for reasons of ruggedness,
compactness or insensitivity to magnetic fields. Other advantages of solid state detectors
are their low operating voltage, low power consumption and large scale fabrication
possibilities. On the other hand, current solid state detectors are limited when it comes to
the detection of very low light fluxes or precise timing measurements and their gain is
very sensitive to temperature variations. The Digital Silicon Photomultiplier (dSiPM)
presented here overcomes those problems by early digitization of the Geiger-cell output
and integrated electronics on chip.
We developed a Digital SiPM of 3.8x3.3mm2 in size containing 8188 individual cells.
Each detected photon is converted into a digital signal as early as possible in each of the
Geiger-mode cells of the sensor. In addition, the complete trigger logic and the time-todigital converter are integrated into the sensor.
To show the performance of the sensor, scintillation crystals of different sizes and
materials using different reflector materials were coupled to the sensor and irradiated by
gamma radiation of 662keV, 511keV and 49keV. The energy resolution at 511keV using
LYSO scintillators was determined to be 10.8%, being comparable to results obtained
with PMTs. The timing resolution of 190ps FWHM for 4x4x5 mm3 LYSO crystals
constitute the best timing resolution ever obtained with this scintillator material.
In addition, the influence of temperature on photon detection efficiency and timing
characteristics of the sensor will be presented.
The results show that the Digital Silicon Photomultiplier is a promising novel detector for
the detection of low light fluxes as encountered in scintillation detector readout,
especially in cases where a good timing resolution is mandatory.
N22: Semiconductor Detectors II: Silicon Devices
Wednesday, Oct. 28 08:00-10:00;
in Grand Ballroom 2
N22-1 (invited) : (08:10) The First Measurements on an Avalanche Diode Array
with Bulk Integrated Quench Resistors for Single Photon Detection
J. Ninkovic1, L. Andricek1, G. Liemann1, G. Lutz2, H. G. Moser1, R. H. Richter1
Semiconductor Laboratory, Max Plancl Institute for Physics, Munich, Germany
2PN
Sensor GmbH, Munich, Germany
1
A Silicon Photomultiplier (SiPM) is an avalanche photodetector that is entering many
application areas as a replacement of conventional photomultiplier tubes (PMTs). Its
Geiger mode operation requires high ohmic polysilicon as quench resistor that becomes
an obstacle for light and is one of the most cost and yield driving technological issues.
We have proposed a new detector concept which has the quench resistor integrated into
the silicon bulk avoiding polysilicon resistors. Extensive simulation results showed the
feasibility of the concept. The quenching mechanism has been demonstrated in a proof of
principle production performed in house. The first prototype fabrication (second
production run) on silicon on isolator substrates has been done and allows testing of the
device performance. The results from the first measurements will be evaluated in
comparison with the simulations. Based on these results the inherent advantages and
drawbacks compared to standard SiPMs will be discussed.
N24: New Detector Concepts and Instrumentation II
Wednesday, Oct. 28 08:00-10:00;
in Grand Ballroom 7
N24-7: (09:40) Time Based Readout of Silicon Photomultiplier (SiPM) for Time of
Flight PET Tomography
P. P. Jarron1, E. E. Auffray1, S. S. Brunner1, H. H. Hillemanns1, A. A. Kluge1,
P. P. Lecoq1, M. M. Morel1, T. T. Meyer1, F. F. Powolony1, M. C. S. C. Williams2,
M. M. Despeisse3
PH, CERN, Geneva, Switzerland
2University of Bologna, Bologna, Italy
3IMT, EPFL,
Neuchatel, Switzerland
1
Time of flight (TOF) technique for PET is very demanding in timing performance,
ideally less than 100ps FWHM precision. We present a time based differential technique
to readout SiPM having less than 10ps rms electronic jitter. The novel readout is a fast
front end circuit based on a first stage differential current mode amplifier with 20 ohm
input resistance. The amplifier inputs are connected differentially to the SiPM anode and
cathode ports. DC current of the amplifier input branches are offset to provide a
discrimination threshold. The second stage of the current mode front end circuit is a fast
differential amplifierdiscriminator circuit performing a time-over-threshold signal
processing. The leading edge of the output signal provides the time information, the
trailing edge the energy information. SPICE simulation results of the precise 3x3 mm
SiPM model and the front end electronics design in 0.25um CMOS technology are
presented and compared to experimental results obtained with a 3x3x20mm LSO
scintillator Crystal readout with a SiPM. Time coincidence precision and energy spectra
are also presented and interpreted with the SPICE simulation.
N25: Posters II
Wednesday, Oct. 28 10:30-12:00;
in Palm 3, 4 & 5
N25-86: (10:30) Characterization of CMOS Position Sensitive Solid-State
Photomultipliers
M. McClish, P. Dokhale, J. Christian, C. Stapels, E. Johnson, R. Robertson, K. S. Shah
Radiation Monitoring Devices, Inc., Watertown, MA, USA
We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a
complementary metal-oxide-semiconductor (CMOS) process. While only needing four
signal output channels to readout, the device provides spatial information on the micropixel level. Three variations of the PS-SSPM design were characterized for their energy
and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each
PS-SSPM is 1.5 x 1.5 mm2, however, each device has different micro-pixel geometries
and different micro-pixel electrical readout for event position sensing. The FWHM
energy resolution at 511 keV was measured using a 1 x 1 x 20 mm3 LYSO crystal. The
resolution varied, however, one PS-SSPM design achieved 11.6%. The LYSO scintillator
coincidence timing resolution also varied between designs with results ranging from 2.1
to 1.0 nsec. Spatial resolution studies were conducted using a focused (~ 15 μm beam
spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, its X and Y FWHM
spatial resolution was measured. Lastly, we demonstrate the PS-SSPM imaging
capabilities using a LYSO scintillator array with 500 x 500 μm2 pixels uniformly
irradiated by 22Na.
N25-118: (10:30) Tests of Silicon Photomultiplier PET Modules
H. Chagani1, R. Dolenec1, S. Korpar1,2, P. Krizan1,3, R. Pestotnik1, A. Stanovnik1,4,
R. Verheyden1
1
Experimental Particle Physics Department, Jozef Stefan Institute, Ljubljana,
Slovenia
2Department of Chemistry and Chemical Engineering, University of Maribor,
Maribor, Slovenia
3Department of Mathematics and Physics, University of Ljubljana,
Ljubljana, Slovenia
4Department of Electrical Engineering, University of Ljubljana,
Ljubljana, Slovenia
The use of Silicon Photomultipliers (SiPMs) as photon detectors in Positron Emission
Tomography (PET) modules offers significant advantages over conventional light
sensors, including application in a magnetic field, better resolution and easier operation.
Two PET modules have been constructed by coupling 4 x 4 arrays of LYSO scintillation
crystals of area 4 x 4 mm2 and length 20 mm to SiPMs. Two types of SiPM have been
tested: the Hamamatsu S10931-100P and Photonique PCB-PET07 of active surface areas
3 x 3 mm2 and 2.1 x 2.1 mm2 respectively. The energy, time and spatial resolutions of the
arrays are presented in view of arrangement into a larger module. Results from both
modules are also compared with light collection simulations performed in GEANT4.
N25-131: (10:30) Recent Developments for CMOS Solid-State Photomultipliers
with Integrated Signal Processing
E. B. Johnson1, C. J. Stapels1, M. McClish1, P. Dokhale1, S. Mukhopadhyay1,
E. C. Chapman1, F. L. Augustine2, J. F. Christian1
1
Radiation Monitoring Devices, Inc., Watertown, MA, USA
2Augustine Engineering,
Encinitas, CA, USA
Solid-state photomultipliers (SSPMs) are a compact, lightweight, potentially low-cost
alternative to a photomultiplier tube for a variety of scintillation detector applications,
including nuclear and medical-imaging applications. Manufacturing SSPMs with a
commercial CMOS process provides the ability for rapid prototyping, and facilitates
production to reduce the cost. On-chip integration of signal processing circuits is a
distinct advantage of CMOS photodetectors beyond traditional phototubes. We will
discuss the advances of the CMOS SSPM with integrated signal processing, which
includes fabrication of large area (1 x 1 cm^2) devices and back illumination of thinned
die.
N25-133: (10:30) Advanced Study of Novel Radiation Detector Based on Silicon
Photomultiplier
A. Osovizky1, D. Ginzburg1, M. Ghelman2, I. Cohen-Zada1, V. Pushkarsky1, E. Marcus2,
A. Manor1, Y. Kadmon2, Y. Cohen2
1
Health Physics Instrumentation Department, Rotem Industries Ltd, Beer-Sheva,
Israel
2Electronics & Control Laboratories, Nuclear Research Center - Negev, BeerSheva, Israel
The Silicon Photomultiplier is a novel and rapidly developing solid state optical sensor.
In contradiction to its use for photon counting the operating conditions of the SiPM are of
main concern when used as a light sensor in portable radiation detection device due to the
gain dependence in temperature and operating voltage. The detection of low energy at
high temperature requires an improvement of the Photon Detection Efficiency (PDE). An
optimization of the PDE can be achieved by increasing the pixel size which improves the
detector sensitive area fill factor. However, an increase in the pixel size reduces the
dynamic range. This work describes the measurements and the results obtained for
different photo-coupling configurations of a CsI(Tl) scintillation crystal with SiPM and
the effect of various operating conditions on the instability of the gain. An optimization
of the dominant parameters, such as noise level, resolution and dynamic range, is
discussed and concluded. The dependence of these parameters in crystal dimension was
examined in series of measurements using about 10 different crystal sizes and 3x3mm
active area SiPM device. The energy equivalent noise level was measured over a wide
temperature range and optimal operating voltage was determined. An investigation of the
pixel size had been performed testing pixels from 35μm to 50μm to determine the most
suitable to achieve the required dynamic range for energies up to 3 MeV. Reduction of
sensor noise was approached with the coincidence detection method using two SiPM
devices and a coincidence circuit. The improvement in noise level was tested in two
configurations of the photo-sensors. The described comprehensive evaluation of the
SiPM device showed the sensor performances in variety of configurations. The results
emphasize the potential of the technology in radiation detection applications and the
issues yet to be solved before it can present a viable alternative to the currently used
technology.
N25-137: (10:30) Fast, Large Area CMOS Solid-State Photomultiplier for
Radiation Detection
P. Dokhale, J. Christian, C. Stapels, E. Johnson, K. Shah
Radiation Monitoring Devices Inc., Watertown, MA, USA
Current and next generation experiments in nuclear and particle physics require sensors
with fast response and high signal-to-noise ratio for detection of low intensity optical
signals. Photomultiplier tubes (PMT) have been widely used for sensing light in most
nuclear physics and imaging research experiments. PMTs, however, have several
drawbacks that limit their use in several applications and technologies. Solid-state
photomultipliers (SSPM) are compact, have high gain at low bias, fast response time and
they are insensitive to magnetic fields gives a potential alternative to photomultiplier
tubes for a variety of scintillation detector applications. A novel solid-state
photomultiplier (SSPM) has been designed and developed by Radiation Monitoring
Devices Inc., using standard CMOS technology. In this paper, we report performance of
large area SSPM detector for spectroscopy and imaging applications. A detector was built
by directly coupling a 6x6x5 mm3 LYSO scintillator to the large area (36 mm2) SSPM.
Energy, co-incidence timing, linearity and imaging performance of the detector was
evaluated. Energy resolution measured for 661.7 keV gamma rays was 9.6% (FWHM).
The timing resolution measured against LYSO-PMT detector with 511 keV gamma rays
(22Na) source was 700 ps. The position sensitive SSPM (PS-SSPM) was also designed,
built and evaluated. A flood image was recorded with a 4x4 LYSO array (each LYSO
element measuring 1.5mm x 1.5mm x 20mm) coupled to a PS-SSPM with 36 mm2 active
area. All 16 LYSO elements were clearly visible and well separated from each other in
the flood image. We have also studied the performance of the 36 mm2 SSPM when
coupled to 5x5x3 mm3 CsI(Tl) scintillator. The energy resolution measured with CsI(Tl)
scintillator for 661.7 keV gamma rays was 7.2% (FWHM).
N25-141: (10:30) Time Resolving Characterization of HPK and FBK Silicon
Photomultipliers for TOF and PET Applications
G. U. Pignatel1,2, G. Ambrosi1, P. Azzarello1, R. Battiston1, G. DiLorenzo2, M. Ionica1
Physics Department, National Institute of Nuclear Physics, Perugia, Italy
2Electronic
and Information Eng., University of Perugia, Perugia, Italy
1
In Time-of-Flight measurements, or Positron Emission Tomography experiments where
two gamma rays are emitted in coincidence, the time resolution of the photon detector is
of primary importance. SIPMs are very promising devices for these applications, since
their intrinsic response time is very short, typically less than 1 ns. However the actual
timing resolution of SIPMs is affected by the area (capacitance) of the device, by the type
of electronics used to pre-amplify the signal, by the dark count rate which is detected as
pure noise, and other second order effects like cross-talk and after dark pulsing. In this
work we report the characteristics of different samples of HPK (Hamamatsu Photonics)
and FBK (Fondazione-Bruno-Kessler) SIPMs, with pixel size ranging from 40 to 100
micron. In particular, we have investigated their time response when stimulated with
O(100) ps pulsed laser with wavelength in the range 400 - 800 nm. SIPM performances
are also compared with that of fast PIN diodes characterized with the same set-up.
N25-151: (10:30) Investigation of Timing Resolution and Energy Resolution for
SiPM/PET Detectors Using the Silicon Flexible Optical Material
J. Zhu1,2, Z. Zhang1, B. Zhang1,2, M. Niu1,2, T. Xu1, X. Zhang3, Q. Xie1,2
1
Department of Biomedical Engineering, Huazhong University of Science and
Technology, Wuhan,Hubei, China
2Wuhan National Laboratory for Optoelectronics,
Wuhan,Hubei, China
3Institute for Pattern Recognition & Artificial Intelligence,
Huazhong University of Science and Technology, Wuhan,Hubei, China
Silicon photomultipliers (SiPMs) attract extensive attention for detecting optical photons
in high energy physics and medical imaging due to its high gain, high photon detection
efficiency (PDE), low operation voltage and fast timing response. We use the silicon
flexible optical material to transform the Gaussian distribution of incident light intensity
into uniform in space, making the incident photons being detected by SiPM equally. In
this way, we can make full use of all cells of SiPM, and more cells operating means more
photons being detected for a certain pulse, which can increase the count rate of the
incident photons, and improve the detection efficiency of SiPM. Furthermore, by
comparing the output of SiPM in different light intensity input, we can find out the best
light intensity fit for SiPM and the suitable crystal and surface treatment for positron
emission tomography (PET) imaging based on SiPM. In primary experiment, we use the
laser pulse as SiPM input since that its light intensity expressed as Gaussian distribution
in space, and analyze the readout of SiPM using the silicon flexible optical material or
not. The result is consistent with our expectation. By the use of the silicon flexible optical
material, the timing resolution and energy resolution of SiPM become better than without
it, when the light intensity of input is appropriated. Considering the difference between
the laser output and scintillation pulse, we will apply the silicon flexible optical material
to SiPM/PET detectors by coupling it to crystal directly, and evaluate its effect on the
timing resolution and energy resolution in PET imaging.
N28: Photodetectors and Scintillation Detectors II
Wednesday, Oct. 28 13:30-15:30;
in Grand Ballroom 7
N28-1: (13:30) SiPM Performance in PET Applications: an Experimental and
Theoretical Analysis
D. Henseler1, R. Grazioso2, N. Zhang2, M. Schmand2
Healthcare, Siemens AG, Forchheim, Germany
2Healthcare, Siemens Medical
Solutions, Rockford, TN, USA
1
Silicon photomultipliers are increasingly being studied for their use in clinical and preclinical PET applications, both by industry and academia. Many groups have evaluated
the performance of Multi-Pixel Photon Counters (MPPCs) from Hamamatsu Photonics.
When coupled to typical PET scintillator crystals, these devices have shown promising
results in terms of energy and timing resolution. The purpose of this paper is to analyze
the main factors that determine the spectroscopic performance of SiPM based PET
detectors and to provide guidelines for further optimization towards the performance
levels of state-of-the-art PMT detectors. We present experimental results for the energy
and timing resolution for different microcell types of Hamamatsu MPPCs coupled to
single LSO crystals. For the 50 m microcell type, we show results for LSO arrays
coupled to MPPC arrays with different coupling geometries. To explore the potential and
the limitations of SiPM based detectors, we present a statistical signal analysis that links
the detector performance to fundamental device characteristics, such as photon detection
efficiency, cell density, crosstalk and afterpulsing probability and dark rate. The relative
influence of each device parameter on the overall spectroscopic performance is analyzed
and discussed. This theoretical analysis is carried out for several optical coupling
configurations. The light distribution is modeled with the ray-tracing program ZEMAX,
before applying the statistical model to the remaining signal chain (see Figs 1 and 2).
Theoretical estimates will be given for both energy and timing resolution Our analysis
concludes with a discussion of the impact of each fundamental device parameter on the
spectroscopic and spatial resolution of a simple PET block detector. This way the model
helps to predict the benefits of future device optimization efforts and to assign priorities
to competing optimization targets.
N28-4: (14:15) Production of Large Area Silicon Photomultipliers for a PET/MR
Scanner
C. Piemonte1, M. Melchiorri1, A. Piazza1, A. Tarolli1, N. Zorzi1, V. Schulz2, T. Solf2,
P. Fischer3
FBK, Trento, Italy
2Philips Research, Aachen, Germany
3University of Heidelberg,
Heidelberg, Germany
1
We report on the production experience and the characteristics of silicon photomultipliers
(SiPMs) fabricated at FBK to be used to fully equip a preclinical positron emission
tomography (PET) system. More than 700 fully working, 2x2 monolithic arrays of
4x4mm2 SiPMs have been produced. A test procedure, based on forward and reverse IV
measurements, has been implemented to extract the basic properties and, finally, to select
the devices at the wafer level. Methodology, results from the on-wafer tests and
functional performance are shown. Besides this production, test SiPMs featuring
microcells with different designs have been fabricated to find the configuration which
optimizes the timing and energy resolution performance of the sensor coupled with the
scintillator. Tests on these structures are ongoing and the results will be shown at the
conference.
N28-5: (14:30) The Digital Silicon Photomultiplier - Principle of Operation and
Intrinsic Detector Performance
T. Frach, G. Prescher, C. Degenhardt, R. de Gruyter, A. Schmitz, R. Ballizany
Philips Corporate Technologies, Aachen, Germany
Recently, the Silicon Photomultiplier (SiPM) gained interest as a potential candidate to
replace Photomultiplier Tubes for reasons of ruggedness, compactness or insensitivity to
magnetic fields. Other advantages of solid state detectors are their low operating voltage,
low power consumption and large scale fabrication possibilities. Today, those SiPMs
operate in an analog manner, connecting the individual Geiger-mode cells of the SiPM in
parallel resulting in an analog output signal. This limits the performance of the analog
SiPM due to parasitic capacitances and inductances, the influence of electronic noise and
sensitivity to temperature drifts.
We developed a digital SiPM (dSiPM) of 3.8mm x 3.3mm in size with readout
electronics integrated next to each of the 8188 Geiger-mode cells to allow for an early
digitization of the state of each cell. In addition, a low skew trigger network, the trigger
logic and a time-to-digital converter are integrated on the sensor chip.
In this talk, we describe the sensors principle of operation and show results on important
sensor characteristics like dark count behavior, photo detection efficiency and timing
resolution.
The integrated electronics allow to switch off faulty cells which generate large numbers
of dark counts. The dark count rate of the sensor can be significantly reduced by
switching off less than 10% of all cells. The overall photo detection efficiency of the
sensor, including the fill-factor, amounts to a maximum of 30% at a wavelength of
420nm and 3.3V excess voltage. The intrinsic timing resolution of the complete sensor,
as determined with a picosecond laser reference, is 22ps FWHM.
The results show that the digital SiPM presented here overcomes major drawbacks of
analog SiPMs like high dark count rates and low yields due to faulty cells. Its integrated
digital electronics enables the detection of single optical photons with very high timing
accuracy.
M06: PET/SPECT instrumentation 1
Thursday, Oct. 29 14:00-15:30;
in International Ballroom Center
M06-2: (14:15) Optimization of Digital Time Pickoff Methods for LaBr3-SiPM
TOF PET Detectors
R. Vinke1, S. Seifert2, D. R. Schaart2, H. T. van Dam2, F. J. Beekman2,3, H. Loehner1,
P. Dendooven1
KVI - University of Groningen, Groningen, The Netherlands
2Delft University of
Technology, Delft, The Netherlands
3University Medical Centre Utrecht, Utrecht, The
Netherlands
1
Scintillation detectors based on LaBr3:Ce crystals and silicon photomultipliers (SiPMs)
are promising for time-of-flight (TOF) positron emission tomography (PET). LaBr3:Ce is
a fast and bright scintillator, while SiPMs have low transit time jitter and high gain. We
focus here on the optimization of digital signal processing (DSP) time pickoff methods
for such detectors. Several methods are compared, including conventional leading edge
(LE) estimators, pulse fitting routines and statistical least square estimators. The analysis
is performed on digitized waveforms originating from two bare 3 x 3 x 5 mm 3 LaBr3: 5%
Ce crystals, coupled directly to 3 x 3 mm2 SiPMs. A high bandwidth preamplifier
provided an energy and a timing signal. Timing signals were digitized at 8 GS/s and 10
bit resolution. The noise on the digitized timing signal is mainly introduced by the
digitizer itself. High gain amplification of the timing signal minimizes the noise-to-slope
ratio of the pulse rising edge on which the time pickoff is performed. As a result, the
noise contribution to the timing resolution is negligible and all time pickoff methods
show similar coincidence timing resolutions of 100-105ps FWHM. It is shown that linear
fitting and extrapolation to the baseline of the pulse rising edge gives rise to incorrect
time pickoff, resulting in artificially good timing resolutions below 100 ps. In a second
series of measurements, timing analysis is performed on large monolithic 18 x 16 x
20mm3 LaBr3:Ce (5%Ce) crystals, coupled to 4 x 4 arrays of SiPMs. In addition to the
time pickoff analysis, a correction is made for the depth-of-interaction related time walk.
This is achieved by determining the 3D photo-conversion location inside the crystal using
Maximum Likelihood Estimation (MLE). A simplified simulation shows that this time
walk correction can improve the coincidence timing resolution by a factor of 1.5.
M06-4: (14:45) Preclinical and Clinical PET Detector Design Considerations Using
Silicon
H. Peng, P. Olcott, C. Levin
School of Medicine, Stanford University, Palo Alto,CA, USA
We are developing a new high-resolution PET block detector using the silicon
photomultiplier (SPM) for both clinical (~3 mm resolution) and preclinical (~1 mm
resolution) PET/MRI applications. As a new type of photon detection device, each SPM
comprises thousands of microscopic avalanche photodiodes operated in Geiger mode;
This detector exhibits the advantages of compact size, high gain and the ability to operate
in a strong magnetic field. In this work, we investigated coupling arrays of 3 mm and 1
mm scintillation crystals to a 4x4 array of 3x3 mm SPM pixels. For the 3.2 mm crystal
pitch array, 2x2 crystals were coupled one-to-one to a 2x2 portion of the 4x4 SPM array
charge without any multiplexing). The 511 keV photopeak energy resolution (the average
for four SPM pixels) is 15.3+/-0.2% FWHM. The individual crystals in the array can be
clearly resolved with average peak-to-valley ratio of 23.1+/-0.8. We studied acrylic
plastic light diffusers of different thickness for sharing light from 1 mm pitch crystals to
the 3 mm pixels of the SPM array. For the case of a 6x6 array of 1 mm crystals directly
coupled to 2x2 pixels of the SPM array with only optical multiplexing, individual 1 mm
crystals were not well resolved as the size of the SPM (3 mm) is too coarse to resolve the
crystals of finer size (1 mm). There was also no distinguishable 511 keV photopeak.
When we coupled an 8x8 array of 1 mm crystals through a 1.5 mm thick light diffuser to
a 3x3 portion of the 4x4 SPM array, an electrical multiplexing was implemented along
with the optical multiplexing to further reduce 9 readout channels down to 4. All 64
crystals are resolved with an average peak-to-valley ratio of 4.48+/-2.06. The 511 keV
photopeak energy resolution of the global energy spectrum (after the normalization per 1
mm crystal) was 21.2+/-0.4% FWHM.
M05: MIC Posters 1
Thursday, Oct. 29 10:30-12:30;
in Grand Ballroom 4&5; Palm 3,4&5
M05-31: (10:30) Feasibility Study of Using Solid State Photomultiplier Array with
Resistor Network Readout for SPECT Detector Development
X. Sun, Y. Shao, C. J. Bircher, K. A. Lan
Imaging Physics, University of Texas MD Anderson Cancer Center, Houston, TX, United
States
It is well known that the solid state photomultiplier (SSPM) has many advantages
including high gain and robust signal output, but suffers noise dominated by high dark
counts, which can be a serious issue to single gamma photon detection. There is also a
technical challenge of using large size SSPM and limited readout channels to decode
array of small size crystals for achieving high spatial resolution. We report the progress
of using the latest commercially available an array of SSPM for developing a high
intrinsic spatial resolution detector for gamma camera and SPECT applications. The
initial detector consists of one 8x8 array of 1x1x3 mm CsI(Tl) crystals and was optically
coupled to a 4x4 matrix of SSPM. Each SSPM (pixel) has 3x3 mm photon sensitive area,
3640 micro cells, ~1 million gain and 4-8 MHz dark counts with different biases, and
~20% PDE. The inter-pixel gap and insensitive edge around the matrix are 0.2 mm,
making it suitable for detecting closely packaged crystals and tiled for large area gammaimaging detectors. A simple resistor network based signal multiplexing board was
developed to investigate the method to reduce the number of readout channels while still
provide suitable imaging performance. SNR as a function of number of pixels at different
signal shaping times were measured. Different light sharing among different pixels were
studied. Initial crystal maps measured with a Co-57 source and 3x3 pixels have shown
that all crystals can be clearly identified except those at the edge, while 4x4 pixels gave
worse results due to increased noises. Our initial study have shown that 1 mm intrinsic
spatial resolution can be achieved with 3x3 mm size SSPM pixels through light sharing,
and certain level signal multiplexing is applicable for reducing the electronic readout
channels. It is expected that this will lead to exciting development of high resolution
SPECT detectors to be reported in the conference.
M05-61: (10:30) Depth of Interaction Encoding Detector with Phosphor-Coated
Crystals and Silicon Photomultipliers
E. Roncali, H. Du, S. Saint James, Y. Yang, Y. Wu, S. R. Cherry
Dept. of Biomedical Engineering, University of California-Davis, Davis, CA, USA
Introduction: in recent years, including depth of interaction information in positron
emission tomography detectors has been a very active area of development. Several
depth-encoding detector designs have been presented to provide discrete or continuous
depth of interaction information. Among them, a solution based on the use of a phosphorcoated scintillator crystal was proposed by Du et al. The phosphor modifies the decay
times of detected pulses. Measuring the variation in decay times enables to get
information regarding the depth of interaction. A resolution of 8 mm has been achieved
using photomultiplier tube readout of the phosphor-coated scintillator array. Here we
present the results from similar experiments conducted using Multi-Pixel Photon Counter
(MPPC) for the readout of phosphor-coated crystals instead of PMTs. A critical
parameter in that study is the sensitivity of the photodetector to the phosphor emitted
light, which peak is at 550 nm. Considering the excellent performance of silicon
photomultipliers, we expected an improvement in the depth of interaction resolution.
Methods: a phosphor-coated LSO crystal was coupled to a MPPC and incorporated into a
depth of interaction resolution measurement setup. This crystal was irradiated side-on at
five different positions and 500 pulses were recorded at each depth. Results: a variation
of 14.3 ns resulted from decay times measurements with a phosphor-coated crystal
whereas a difference of 3.8 ns was obtained with uncoated crystal. Conclusions:
significant variations in decay times were measured with phosphor-coated crystals
coupled to MPPCs. This may be improved by using larger silicon photomultipliers and
optimization of the experimental setup. Pulse shape discrimination methods will be
implemented to evaluate the depth of interaction. Methods to add information such as rise
time variation or spectral information in pulse shape discrimination will be investigated
as well.
M05-73: (10:30) Time-of-Flight PET Detector Based on Multi-Pixel Photon
Counter
C. L. Kim
Imaging Technologies, GE Global Research, Niskayuna, NY, USA
Since Geiger-mode multi-pixel APD can have better photon detection efficiency than
PMT, we proposed that it could be a suitable photo-sensor for next-generation time-offlight PET detectors. Last year, we have presented the coincidence timing resolution of
240ps result using single channel detectors based on 3 x 3 mm2 Multi-Pixel Photon
Counter (MPPC) and 3 x 3 x 10mm3 LYSO crystals. MPPC is a Geiger-mode multi-pixel
APD developed by Hamamatsu Corp. In this work, we will present the coincidence
timing resolution of a time-of-flight PET detector based on a 4 x 4 array of 3 x 3 mm2
50um MPPCs. Since timing resolution depends on crystal size and shape, longer LYSO
crystals with 3 x 3 x 25 mm3 dimension were used to be realistic. A preliminary result
showed MPPC-LYSO detector could achieve less than 350ps coincidence timing
resolution in FWHM between two of these block detectors. We will present the timing
result using 4 x 4 array of 3.5 x 3.5 x 25mm3 LYSO crystals too in order to understand
the aspect ratio effect between LYSO and MPPC sizes. We will also discuss about its
readout challenges due to increased number of channels in a SSPM block detector
compared to conventional PET detector based on PMTs.
M05-91: (10:30) Monolithic 64-Channel Silicon Photomultiplier Matrices for Small
Animal PET
G. Llosa1, N. Belcari1,2, M. G. Bisogni1,2, S. Marcatili1,2, G. Collazuol1,3, M. Melchiorri4,
C. Piemonte4, P. Barrillon5, S. Bondil-Blin5, N. Dinu5, C. de La Taille5, A. Del Guerra1,2
Department of Physics, University of Pisa, Pisa, Italy
2INFN Pisa, Pisa, Italy
3Scuola
Normale Superiore, Pisa, Italy
4Department of microelectronics, FBK-irst, Trento,
Italy
5Linear Accelerator Laboratory, Orsay, France
1
The University of Pisa and INFN Pisa are developing a small animal PET scanner with
Silicon Photomultiplier (SiPM) matrices as photodetectors. The proposed PET scanner
will consist of four detector heads, composed of three detection layers. Each layer will be
made of a continuous LYSO crystal 4 cm x 4 cm x 5 mm and a SiPM matrix structure as
photodetector. The matrices are produced at the Center for Scientific and Technological
Research (FBK-irst) in Trento, Italy. The successful results obtained with the first 16pixel matrices have lead to the fabrication of matrices with 64 (8x8) SiPM elements in a
common substrate, with different layouts. The matrices tested are 12 mm x 12 mm size,
with readout on two opposite sides. The SiPM elements are 1.5 mm x 1.4 mm size and
they have 840 microcells of 50μm x 50μm size. The matrices show an excellent
uniformity in the breakdown points of all pixel elements. The first tests have been
performed with continuous LYSO crystals, employing the ASIC MAROC2 and test
board developed at the Linear Accelerator Laboratory (LAL) in Orsay (France) as data
acquisition system. The energy resolution at 511 keV is 17% without correcting for the
gain variations among the different pixels. The first position determination tests have
been performed. A spatial resolution about 1 mm FWHM has been obtained with centerof-gravity algorithms. Reconstruction tests with maximum likelihood algorithms are
being carried out. The results will be presented.
M05-94: (10:30) Measured Temperature Dependence of Scintillation Camera
Signals Read Out by GeigerMller Mode Avalanche Photodiodes
W. C. J. Hunter1, R. S. Miyaoka1, L. R. MacDonald1, T. K. Lewellen1,2
Radiology, University of Washington, Seattle, WA, USA
2Electrical Engineering,
University of Washington, Seattle, WA, USA
1
Signals of a Geiger-Müller mode avalanche photodiode (GM-APD) are strongly
dependent on junction temperature. Consequently, we are developing a temperaturecontrolled GM-APD-based detector for positron emission tomography (PET) whose
monitored temperature can be used to dynamically account for the temperature
dependence of the output signals. Presently, we aim to characterize the output-signal
dependence on temperature and bias for a GM-APD-based scintillation camera.
Preliminary data for a Zecotek MAPD-3N GM-APD suggest a linear dependence of
breakdown voltage on temperature (slope 0.071 V/°C), corresponding to a rapid variation
in gain with temperature (>10%/°C). Furthermore, using two MAPD-3N to read out a
pair of 3.5-by-3.5-by-20 mm3 Zecotek LFS-3 scintillator, we observe a moderate
decrease (~200 psec) in coincidence-time resolution of a Ge-68 point source as the
temperature was lowered from 23 °C to 10 °C. We also investigate changes in energy
resolution with temperature.
M05-244: (10:30) Solid-State Detector Stack for ToF-PET/MR
T. Solf1, V. Schulz1, A. Thon1, P. Fischer2, M. Ritzert2, V. Mlotok2, C. Piemonte3,
N. Zorzi3
Molecular Imaging Systems, Philips Research Laboratories, Aachen, Germany
2Chair
of Cricuit Design, University of Heidelberg, Heidelberg, Germany
3Micro-ElectroMechanical-Systems and Radiation Detectors, Foundation Bruno Kessler, Trento, Italy
1
Simultaneous PET and MR imaging requires a novel type of highly integrated PET
detectors. Due to geometric constraints and MR compliance a very compact detector
stack was built within the HYPERImage consortium. This allows a four sides buttable
detector module design with a low dead space in between. The scintillation light coming
from a LYSO array is converted in a SiPM sensor tile with a high packing fraction and a
high photo detection efficiency to provide sub-ns time-of-flight timing resolution. The
analog signals coming from SiPM detectors are digitized close to the sensor to minimize
potential crosstalk. A custom mixed-signal ASIC was integrated on a 64 channel sensor
stack which is powered and controlled by an FPGA interface board. The complete sensor
stack is assembled and characterized to extract the PET relevant parameters, in particular
energy, timing and spatial resolution.
M05-268: (10:30) Performance Measurements of a LYSO-SSPM Detector Module
for Small Animal Positron Emission Tomography.
P. Dokhale1, C. Staples1, J. Christian1, S. Cherry2, W. Moses3, K. Shah1
Radiation Monitoring Devices Inc., Watertown, MA, USA
2Department of Biomedical
Engineering, UC-Davis, Davis, CA, USA
3Lawrence Berkeley Lab, Berkeley, CA, USA
1
We present the performance of a compact PET detector module with a depth-ofinteraction (DOI) capability based on a LYSO scintillator array coupled at both ends to
CMOS solid state photomultipliers (SSPM). In this paper we present energy, coincidence
timing resolution and flood imaging results for a prototype PET detector module
consisting of a 4 x 4 block of LYSO scintillators, each crystal measuring 1.43 x 1.43 x 20
mm3 coupled to 4 x 4 array of SSPM (PS-SSPM) each SSPM measuring 1.5x1.5 mm2.
All 16 elements in the flood image recorded with 22Na gamma-ray source were clearly
visible and well separated from each other. The measured FWHM energy resolution with
511 keV gamma rays for all crystals in the array ranged between 14% 15%. The timing
resolution measured for the complete detector module in coincidence with LYSO-PMT
detector was 2.2 ns. The DOI resolution was measured for all crystals in the array by dual
ended readout method. The average DOI resolution measured for corner crystal was ~ 2.3
mm and for middle crystal was 2.5 mm.
M05-280: (10:30) Detectors with Dual-Ended Readout by Silicon Photomultipliers
for High Resolution Positron Emission Mammography Applications
F. Taghibakhsh1,2, S. Cuddy1, T. Rvachov3, A. Reznik2,4, J. A. Rowlands1,2
1
Department of Medical Biophysics, University of Toronto, Toronto, ON,
Canada
2Thunder Bay Regional Health Sciences Centre, Thunder Bay, ON,
Canada
3Department of Electrical and Computer Engineering, University of Toronto,
Toronto, ON, Canada
4Department of Physics, Lakehead University, Thunder Bay, ON,
Canada
Reducing parallax error and increasing overall efficiency are two key factors in
development of high resolution positron emission mammography (PEM) systems to
detect early stages of cancerous activities in breasts. We propose silicon photomultipliers
(SiPM) coupled to LYSO crystals in dual readout configuration for high timing and depth
of interaction (DOI) resolution as PEM detectors. We examine the effect of surface
finishing of the pixilated crystals on various detector performances such as DOI, timing
and energy resolution to arrive at a proper detector design. Our experimental setup
consists of single 2x2x20 mm3, and multiple 1x1x20 mm3 crystals coupled to SiPM
arrays, custom designed dual readout electronics, 22Na and FDG positron sources. We
used the scaled difference between the two SiPM signals for extraction of DOI
information, while the sum of the signals provided energy and timing information (Fig.
1). We are investigating the effect of crystal side walls finishing on resolution and
linearity of DOI measurement, as well as energy discrimination (Fig. 2 and 3). So far, our
measurements indicate almost linear DOI resolution of ~0.8 mm for saw cut crystal side
walls, and ~1.5 mm for polished crystals. Energy discrimination improves as DOI
approaches either ends of the crystal, and resolution of better than 19% and 15% were
measured for rough cut and polished crystals respectively using 22Na source;
experiments with an FDG source (no lead collimator) resulted in energy resolution of
better than 13%. We will present details of our experiments and results for DOI, timing
and energy resolution for single and multiple detectors. The high gain and fast response
of SiPM, comparable to those of photomultiplier tubes, improve timing resolution for
better true coincidence detection, and the dual readout configuration provides high
resolution depth of interaction information to reduce parallax error for essential for
efficient and high resolution PEM.
N40: Photodetectors and Scintillation Detectors III
Thursday, Oct. 29 13:30-15:30;
in Grand Ballroom 1
N40-6: (14:45) MPPC Response Simulation and High Speed Readout Optimization
F. Retiere
TRIUMF, Vancouver, BC, Canada
Pixilated Geiger Mode avalanche photo-diodes and especially Hamamatsu Multi-Pixel
Photon Counters (MPPC) are replacing photomultiplier tubes (PMTs) in a variety of
applications. However, to become a competitive alternative to PMTs, a number of
drawbacks must be overcome or accommodated: small size, lower gain (roughly a factor
of 10 smaller) , large dark noise (0.5-1 MHz) and significant after-pulsing (5-20%) .
While the small size has to be accommodated, the other nuisances can be dealt with when
designing the readout electronics. To do so, we rely on a Monte Carlo simulation of the
MPPC response developed for the T2K experiment. We focus on two applications that
require excellent timing resolution: plastic scintillator readout for muon spin rotation
experiments and LSO readout for Positron Emission Tomography. For the latter
application, accurate simulation of the MPPC recovery is critical to understand the LSOMPPC response because the LSO time constant is long (40 ns) compare to the MPPC
intrinsic recovery (13 ns for T2K MPPC) time constant. We will show that by using the
simulation information to design high speed readout electronics, we achieved excellent
energy resolution (limited by LSO for PET) and timing resolution (<500 ps for PET).
N40-7: (15:00) Evaluation of Silicon Photomultiplier Arrays for the GlueX Barrel
Calorimeter
C. Zorn
Radiation Detection and Medical Imaging Group, Jefferson Laboratory, Newport News,
VA, USA
On behalf of the GlueX Collaboration
The first prototype silicon photomultipliers suitable for use as the photodetector for the
GlueX barrel calorimeter have been delivered and are being evaluated. These detectors
are in the form of a 4x4 array of closely-packed 3x3 mm^2 detector elements. The next
generation (to be delivered in the near future) will be encapsulated within a ceramic base
that will allow for temperature control via an onboard peltier cooler. This will allow one
to cool the sensor directly both in order to reduce the dark noise and to maintain a
constant temperature so as to keep the gain stable. PDE and dark rate measurements of
the two currently considered vendors indicate cooling will be necessary with one and
temperature maintenance with either. A possible third vendor may also be evaluated if
suitable array-style photodetectors can be delivered.
M09: MIC Posters 2
Friday, Oct. 30 10:30-12:30;
in Grand Ballroom 4&5; Palm 3,4&5
M09-8: (10:30) Development of PET Using 4x4 Array of Large Size Geiger-Mode
Avalanche Photodiodes
K. J. Hong1, Y. Choi1, J. H. Kang1, W. Hu1, J. H. Jung1, B. J. Min1, S. H. Shin1,
Y. S. Huh1, H. K. Lim1, Y. H. Chung2, P. Hughes3, C. Jackson3
1
Department of Nuclear Medicine, Sungkyunkwan University, Samsung Medical Center,
Seoul, South Korea
2Department of Radiological Science, College of Health Science,
Yonsei University, Wonju, South Korea
3SensL, Cork, Ireland
Geiger-mode avalanche photodiode (GAPD) has been demonstrated to be a high
performance PET sensor because of high gain, fast response, low excess noise and
magnetic field insensitivity. The purpose of this study is to develop a PET for human
brain imaging using 4x4 array of large size GAPD. PET detector modules were designed
and built to develop a prototype PET. The PET consisted of 8 pairs of LYSO-GAPD
block detectors arraged in a partial ring, covering arc of 80˚, with an inner diameter of
330 mm. The LYSO arrays consisted of 4x4 array of 3x3x20 ㎣ pixels, which were 1-to1 coupled to a 4x4 array of 9 ㎟ GAPD pixels (SensL, Ireland). The GAPD arrays were
fabricated to maintain the the variations of 511 keV photopeak position of the 16 pixels
within 20%. The signals of the each module were amplified by a 16-ch preamp with
differential outputs and then sent to a position decoder circuit (PDC), which readouts
digital address and analog pulse of the one interacted channel from 64 signals of 4
preamplifier boards. The PDC output signals were fed into FPGA-embedded DAQ
boards. The analog signal was sampled with 100 MHz, and arrival time and energy of the
digitized signal were calculated and stored. PET imaging was performed by rotating an
object with a step-and-shoot acquisition with 60 projections over 180. The coincidence
data were sorted and each projection was normalized and reconstructed by OSEM. The
average energy and time resolution of 16 LYSO-GAPD block detectors for 511 keV was
20% and 2.2 ns, respectively. Activity distribution patterns of hot&cold-rod phantoms
were well imaged without distrortions, and rods down to a diameter of 3.2 mm were
resolved. Currently, a full-ring PET system consisting of 72 detector modules having
12.9 mm axial and 330 mm transaxial FOV is being developed. These results
demonstrate that high performance PET could be developed using the GAPD-based PET
detectors, analog and digital signal processing methods designed in this work.
M11: Plenary 2 / Multimodality Instrumentation and
Techniques
Friday, Oct. 30 16:00-18:00;
in International Ballroom Center
M11-4: (17:15) Development of a Detector Module for Combined PET/CT or
Combined Photon Counting/Standard CT Based on SiPM Technology
A. Persson1, A. Khaplanov1, B. Cederwall1, C. Bohm2
Department of Physics, Royal Institute of Technology, Stockholm, Sweden
2Department
of Physics, Stockholm University, Stockholm, Sweden
1
Recent developments make it possible to utilize SiPMs for quantifying high radiation
fluxes in current mode as well as in pulse mode measurements for counting and
characterizing individual gamma-ray or X-ray photons when coupled to scintillators. This
opens new possibilities for multimodal medical imaging by enabling common radiation
sensors for PET, standard CT and photon counting CT. Currently, two separate detector
systems are required for combined PET/CT. The advantages of an integrated PET/CT
system include increased patient throughput, higher image fusion accuracy due to perfect
PET-CT sensor alignment and reduced system cost. In this work we present a novel
detector design based on dual-mode readout of SiPM-based radiation sensors that enables
imaging systems where conventional CT imaging is combined with PET, as well as in CT
systems where both conventional integrating (high-flux) and photon counting (low-dose)
operation can be selected. Such dual-mode SiPMs coupled to scintillators in medical
imaging can be used to detect and characterize single primary X-ray or gamma-ray
photons up to fluxes of millions of photons per mm^2 per second in pulse mode. Current
mode operation allows the dynamic range to be extended to the much higher rates found
in standard CT imagers and beyond. For this purpose the selection of the optimal
scintillator is crucial as is the design of the dual SiPM readout electronics. A prototype
detector has been developed and studied from the point of view of the energy and timing
resolution required for the photon-counting application as well as the flux-to-current
characteristics, essential for the current mode.
M13: MIC Posters 3
Saturday, Oct. 31 10:30-12:30;
in Grand Ballroom 4&5; Palm 3,4&5
M13-6: (10:30) Cross-strip capacitive multiplexing and electro-optical coupling for
silicon photomultiplier arrays for PET detectors
P. D. Olcott1,2, H. Peng1, C. S. Levin1
Radiology, Stanford University, Stanford, CA, USA
2Bio-engineering, Stanford
University, Stanford, CA, USA
1
A key component for the development of simultaneous, PET/MR is a PET block detector
that has a low number of readout channels, non-magnetic components, and little or no
mutual influence between PET and MR systems. We have developed a differential
multiplexing circuit for silicon photomultipliers (SiPM) that uses capacitors instead of
resistors in a way that preserves their coincidence time performance. We demonstrated
that a 4 x 4 array of 3 mm x 3 mm SiPM devices can be multiplexed into four signals
with excellent spatial, energy (15.9 +/- 0.4% FWHM at 511 keV) , and timing resolution
(1.4 ns FWHM) using a variety of scintillation crystal designs. Output signals from the
multiplexing circuit can directly drive telecommunication-grade lasers without using
active amplifiers to transmit the energy and fast timing information of the scintillation
block detector out of the MR, using multi-mode optical fibers, rather than coaxial cables,
using a custom designed laser alignment block. This multiplexed, laser coupled block
detector has a significant reduction in the number of readout channels while having a
very low electrical footprint. These two technologies will be a key enabler of SiPM
technology for high resolution small animal and clinical PET/MR.
M13-9: (10:30) Development of G-APD-Based PET Block Detectors
A. Kolb1, E. Lorenz2, D. Renker3, R. Grazioso4, N. Zhang4, D. Henseler4, B. J. Pichler1
1
University of Tuebingen, Laboratory for Preclinical Imaging and Imaging Technology,
Tuebingen, Germany
2Max Planck Institute for Physics, Muenchen, Germany
3Paul
Scherer Institute, Villigen, Switzerland
4Siemens Medical Solutions, MI, Knoxville, USA
The focus of this study was to build a Geigermode Avalanche Photodiode (G-APD)
based PET block detector with a high multiplexing factor and to determine desirable
structure specifications for future G-APD detectors. In order to determine the most
appropriate structure specifications for the block detectors, G-APDs from various
manufacturers (Hamamatsu, SensL, Zecotek) will be compared. Most G-APD
manufacturers use a standard silicon n-on-p type structure with the exception of
Hamamatsu and Zecotek which use a p-on-n structure. Typically, p-on-n devices have a
higher quantum efficiency in the blue-light region (<470nm) than n-on-p devices which
can significantly increase the G-APD photon detection efficiency. The signal-to-noise
ratio of p-on-n devices is additionally enhanced by having a typically lower dark count
rate than n-on-p devices [1]. These two effects make p-on-n type G-APDs more suitable
in PET detector applications using LSO and similar scintillators emitting in blue light.
The newly built block detectors using p-on-n type G-APDs will be compared to a
previously built detector using n-on-p G-APDs from SensL. Moreover, block detectors
will be built with a 4x4 array of G-APDs in order to readout a 15x15 LSO block of 1.5
mm x 1.5 mm x 10 mm crystals. Initially, G-APDs from two different vendors were
coupled to a single LSO crystal (3 mm x 3 mm x 20 mm) and were evaluated in terms of
energy and timing resolution. The G-APDs tested were the Hamamatsu S10391 and the
Sensl SPMMicro3035 both having an active area of 3 mm x 3mm. A prototype detector
was built using a 4x4 array of S10391 G-APDs coupled to a 12 x 12 LSO crystal block
with an individual crystal size of 1.5 mm x 1.5 mm x 10 mm was used. The LSO crystal
block/G-APD array combination was evaluated in terms of energy and timing resolution
yielding an energy resolution range of 16-22% and a timing resolution of 1.4 ns in
coincidence with a LSO/PMT detector.
M13-60: (10:30) Position-Sensitive Solid State Photomultipliers for PET Imaging
E. Roncali1, Y. Yang1, M. McClish2, P. Dokhale2, C. Stapels2, E. Johnson2, J. Christian2,
K. S. Shah2, S. R. Cherry1
1
Dept. of Biomedical Engineering, University of California-Davis, Davis, CA,
USA
2Radiation Monitoring Devices Inc., Watertown, MA, USA
Due to their excellent overall performance characteristics, silicon photomultipliers are
promising for numerous emerging applications and technologies, and are particularly
suitable for constructing compact detector modules such as for small animal PET
scanners. Designing new silicon photomultipliers with enhanced features (higher
photodetection efficiency and larger active area) has been a very active area of
development for the last recent years. Here we present the characterization of position
sensitive CMOS solid state photomultipliers (PS-SSPMs) using LSO and LYSO
scintillator crystals. Spatial and timing resolutions were measured on LYSO crystals.
Flood imaging of LYSO and LSO crystals has also been performed. Depth of interaction
(DOI) resolution measurements have been performed using dual-ended readout of LYSO
crystals by PS-SSPMs. Pulse shape analysis for DOI-encoding also was evaluated using
signals recorded by a phosphor-coated LSO crystal read out by a PS-SSPM. 0.5 mm
crystals could be resolved in LSO and LYSO arrays and an intrinsic spatial resolution of
70 μm was measured for a highly collimated light source. 1 ns timing resolution and 15%
energy resolution was measured on a 1.5 x 1.5 x 20 mm3 LYSO crystal. A depth of
interaction resolution of 2.5 mm was obtained with a dual-ended readout setup.
Experiments conducted with a phosphor-coated LSO crystal showed a relationship
between the depth of irradiation and the pulse shape. Amplitude and decay times were
found to be greater and longer when interactions occurred at the near end of the crystal.
Development of larger devices is in progress and new PS-SSPM elements will be tested
M13-87: (10:30) Feasibility Study of Using Solid State Photomultiplier Array for
PET Detector Development
C. J. Bircher, Y. Shao, X. Sun, K. Lan
Physics, University of Texas MD Anderson Cancer Center, Houston, TX, USA
Solid State photomultipliers have the potential to dramatically improve the performance
of Positron Emission Tomography. Their low form factor, high intrinsic gain, fast timing,
and good energy resolution will allow SSPMs to advance simultaneous PET/MRI and
dual ended readout for depth of interaction measurements. In this study we investigated
the imaging capability of the first tillable SSPM array with large area pixels for PET
application. The array has 16 pixels in a 4x4 matrix. Each pixel has 3640 total microcells, 3x3 mm sensitive area, and about one million amplification gain. Both inter-pixel
gap and insensitive edge are around 0.2 mm, which improves the photon detection
efficiency and makes it possible to closely tile multiple arrays for designing large area
detector. Its basic performance of gain, dark counts and signal linearity were measured.
Energy and resolution was measured with a 2x2x10 mm LYSO crystal with a Na-22
source are ~20%. To evaluate its imaging capability, a 12x14 array of 1.4x1.4x10 mm
LSYO crystals were optically coupled to the SSPM array with light sharing among
different pixels. Either with a individual signal readout of each SSPM pixel or with a
position sensitive readout based on a signal multiplexing circuit with a resistor network
for current sharing, all crystal were clearly identified. Other detector performance such as
Depth-Of-Interaction, detector with multiple SSPM arrays, and test inside MRI for PETMR dual modality imaging will be reported as well. Our initial studies have indicated
that, with appropriate detector design and electronics, substantial imaging performance
and innovative imaging design approaches can be achieved for PET clinical and
preclinical applications.
M13-267: (10:30) The "X'tal Cube" PET Detector: 3D Scintillation Photon
Detection by a 3D Crystal Array Using MPPCs
Y. Yazaki1,2, H. Murayama2, N. Inadama2, H. Osada1,2, F. Nishikido2, K. Shibuya3,
T. Yamaya2, E. Yoshida2, M. Suga4, T. Moriya5, M. Watanabe5, T. Yamashita5,
H. Kawai1
Graduate School of Sciences, Chiba University, Chiba, Japan
2Molecular Imaging
Center, National Institute of Radiological Sciences, Chiba, Japan
3Graduate School of
Arts and Sciences, Tokyo University, Tokyo, Japan
4Graduate School of Engineering,
Chiba University, Chiba, Japan
5Central Reserch Lab., Hamamatsu Photonics K.K.,
Shizuoka, Japan
1
ABSTRACT- We have proposed a depth of interaction (DOI) PET detector named X'tal
cube, in which a number of Multi-Pixel Photon Counters (MPPCs) are coupled on
various positions of six surfaces of a segmented scintillation crystal block. There are no
reflectors within the block, and the areas among MPPCs on the surface are covered with
reflector. Each MPPC is thin and light solid-state photo-detector so that the crystal block
can be closely placed on the PET detector ring. To study the characteristics of the Xtal
cube, we constructed a crystal block consisting of six layers of a 6 x 6 segmented crystal
array with Lu2xGd2(1-x)SiO5 (LGSO) crystals. Each crystal is 3.0 x 3.0 x 3.0 mm3. We
examined crystal identification performance for different MPPC arrangements on the
block surfaces, where we used 3-dimensional (3D) Anger-type position calculation. The
preliminary experiments showed the possibility of a 3D detector having isotropic
resolutions for PET.
M13-273: (10:30) Possibility Analysis of Si-PM Based DOI Detector Using Pulse
Shape Analysis for PET
S. Yamamoto
Kobe City College of Technology, Kobe, Japan
Geiger-mode avalanche photo-diode (silicon photomultiplier: Si-PM) was tested whether
it can be used for depth-of-interaction (DOI) detector based on decay time differences of
the scintillator using pulse shape analysis. Hamamatsu Si-PM (MPPC: S10362-33025C）was used for the experiments which has 3mm x 3mm sensitive area. The Si-PM
was optically coupled to two GSO crystals with difference Ce concentration, 1.5 mol%
(decay time of 35ns) and 0.5 mol% (~50ns), optically coupled in DOI direction. Also the
Si-PM was tested with two LGSO with different Ce concentration, 0.025 mol% (33ns)
and 0.75 mol% (43ns). Pulse shape and energy spectra for Cs-137 gamma photons (662
keV) were measured digitally using dual integration method. In both combinations of
scintillators, pulse shape spectra were successfully obtained with Si-PM. Si-PM optically
coupled with GSO crystals with different Ce concentration showed good separation in the
pulse shape spectrum; peak-to-valley (P/V) ratio was 3.6. Si-PM with LGSO crystals
showed moderate separation; P/V ratio was 1.25. With these results, it is confirmed that
Si-PM can be used for DOI detectors based on the decay time difference of scintillators
using pulse shape analysis.