Please note! All times in the online program are given in New York - America (GMT -04:00) times!

New York - America ()
Jan 26, 2022, 3:06:12 PM
Your time ()
Tokyo - Asia ()
Jan 27, 2022, 5:06:12 AM
Our exhibitors and sponsors – click on name to visit booth:

To search for a specific ID please enter the hash sign followed by the ID number (e.g. #123).


Session chair: Lee , Jae Sung (Seoul National University, Department of Biomedical Sciences, Seoul, South Korea); Takahashi , Tadayuki (The University of Tokyo, Kavli IPMU, Kashiwa, Japan); Woody , Craig (Brookhaven National Laboratorty, Physics Department, Upton, USA)
Shortcut: JS-01
Date: Monday, 18 October, 2021, 11:00 AM - 1:30 PM
Session type: Joint Session


Click on an contribution to preview the abstract content.

11:00 AM JS-01-01

Reconstruction-free imaging of positron-emitting radionuclides using ultra-fast detectors (#716)

R. Ota1, S. I. Kwon2, E. Berg2, F. Hashimoto1, K. Nakajima3, I. Ogawa3, Y. Tamagawa3, T. Omura1, T. Hasegawa4, S. R. Cherry2

1 Hamamatsu Photonics K.K., Central Research Laboratory, Hamamatsu, Japan
2 University of California, Davis, Department of Biomedical Engineering, Davis, California, United States of America
3 University of Fukui, Faculty of Engineering, Fukui, Japan
4 Kitasato University, School of Allied Health Science, Sagamihara, Japan


Positron-emitting radionuclides are widely used in biomedical applications, most commonly for positron emission tomography imaging. Detection and localization of the back-to-back annihilation photons produced by positron-electron annihilation subsequent to beta-plus decay defines the trajectories or lines of response of these photons, which when combined with tomographic reconstruction algorithms, permits recovery of the distribution of the injected radionuclides in cross-sectional images.  Here, we demonstrate for the first time the ability to produce cross-sectional images of a positron-emitting radionuclide directly from the detected coincident annihilation photons, without the use of a reconstruction algorithm.  Using ultra-fast radiation detectors with a coincidence resolving time averaging 35 picoseconds to measure the difference in arrival time of the annihilation photons, we demonstrated spatial localization of each annihilation location along its line of response to 5.3 mm. Three experiments were performed, using three different types of imaging objects, i.e. NEMA-NU4, Derenzo, and Hoffman brain phantoms, each filled with an aqueous solution of 18F-fluorodeoxyglucose, and successfully generated their cross-sectional images using only timing information from the ultrafast detectors. These results indicate that direct positron emission imaging is feasible and we discuss avenues to enhance the detector/system sensitivity and timing performance to make direct imaging medically practical.

AcknowledgmentRyosuke Ota, Sun Il Kwon, and Eric Berg contributed equally to this work.
Keywords: Direct Positron Emission Imaging, Reconstruction-free imaging, CRI-MCP-PMT, Ultrafast timing
11:15 AM JS-01-02

Improving SiPM Performance for Time-of-Flight (TOF) PET DetectorsBased on Bismuth Germanate (BGO) (#430)

S. I. Kwon1, A. Gola2, G. Borghi2, G. Paternoster2, S. Merzi2, S. R. Cherry1

1 University of California, Davis, Biomedical Engineering, Davis, California, United States of America
2 Fondazione Bruno Kessler, Trento, Italy


Time-of-flight positron emission tomography (TOF-PET) detectors measure the difference in arrival time of the two 511 keV annihilation photons, and the TOF information spatially constrains the location of each annihilation event, improving image quality. Recently, bismuth germanate (BGO) has been getting attention as an emerging scintillator for use in TOF PET applications because its coincidence timing resolution (CTR) was dramatically improved by detecting Cerenkov photons produced in BGO by energetic electrons following 511-keV photon interactions. Because only a small number of Cerenkov photons (~17) are produced in BGO, to obtain a good CTR, it is of utmost importance to use SiPMs with very high PDE, excellent single-photon timing resolution (SPTR) and low correlated noise. In this study, we developed novel approaches to improve SiPM timing performance for BGO-based TOF PET detectors. In particular: 1) the NUV-HD technology has been modified, engineering the electric field inside the microcells to obtain trade-offs in terms of photon detection efficiency (PDE) as a function of the over-voltage, spectral responsivity, electrical characteristics, etc. and 2) a metal mask with variable geometry has been implemented on SiPMs to obtain a faster rise-time of microcell signal and a more homogeneous SPTR. A variety of SiPMs were produced with different combinations of the developed approaches and compared in this study. SiPMs with the metal mask showed a higher gain and faster rise time. CTR measured with BGO coupled to SiPMs with a metal mask was also much improved compared to BGOs coupled to SiPMs without a metal mask. The results guide appropriate SiPM fabrication approaches for BGO to improve timing performance.


This research was supported in part by NIH grants R01 EB029633 and R35 CA197608.

Keywords: Bismuth Germanate (BGO), silicon photomultiplier (SiPM), positron emission tomography (PET)
11:30 AM JS-01-03

Photon-trapping nanostructures in silicon photodetectors to improve detection speed and efficiency of optical photons in the visible range (#569)

C. Bartolo-Perez2, A. Ahamed2, H. C. Travaglini3, A. S. Mayet2, S. GhandiParsi2, S. Merzi4, A. Gola4, S. Cherry1, S. Islam2, G. Ariño-Estrada1

1 University of California, Davis, Department of Biomedical Engineering, Davis, California, United States of America
2 University of California, Davis, Department of Electronic and Computer Engineering, Davis, California, United States of America
3 University of California, Davis, Department of Physics, Davis, California, United States of America
4 Fondazione Bruno Kessler, Trento, Italy


Significant improvements in the detection efficiency of photodetectors without any compromise in time performance are
highly desired. This work reports on the utilization of photon-trapping (PT) nanostructures in silicon-basedphotodetectors to improve detection efficiency and time performance in the visible wavelength range. Time performance in unity-gain photodetectors with and without PT nanostructures was experimentally measured for photons of 850 nm wavelength. An improvement of the pulse full width half maximum (FWHM) from 99 ps down to 40 ps was achieved. The expected detection efficiency of devices with 1.2 um thickness for photons of 450 nm
wavelength with and without PT is of 60% and 80%, respectively. The next step of this work is to extend the utilization of PT nanostructures to photodetectors single photon avalanche detectors (SPADs) to obtain photodetectors with simultaneously high detection efficiency, high gain, and fast time performance.

AcknowledgmentThis work was supported by NIH grant R21 EB028398.
Keywords: photon-trapping structures, photodetectors, SPAD, detection efficiency, SPTR
11:45 AM JS-01-04

Spectrally encoded Schlieren imaging for ionizing radiation detection via modulation of optical properties (#363)

D. Jeong1, Y. Kim1, L. Tao1, R. Coffee2, C. Levin1

1 Stanford University, Radiology, Stanford, California, United States of America
2 SLAC National Accelerator Laboratory, Menlo Park, California, United States of America


Dramatically improving the coincidence time resolution (CTR) in time-of-flight positron emission tomography (ToF-PET) down to 10-picosecond can bring benefits in the clinical setting, such as improved lesion detection and quantification, lower dose or scan time, or a mixture of these. As detection of individual 511 keV photons is required, however, an extremely sensitive and fast detection mechanism is necessary. To achieve such a CTR, the mechanism of optical property modulation was proposed as a possible alternative to scintillation to detect the fast transient charge tracks induced by ionizing radiation.

Here, we continue to explore more sensitive setups, this time based on the ‘Schlieren imaging’ technique, which measures the optical contrast of a signal against background noise. We chirped a pulsed probe laser beam to accommodate asynchronous arrival times of the ionizing radiation while maintaining high timing precision. A single-photon avalanche diode (SPAD) array provided both spatial localization of the laser probe beam over the ionization-induced charge tracks, and spectral encoding of the time resolution for ultrafast timing. In this paper, we report a 1.43% shift of the mean value in the distribution of the transmitted optical signal with and without Tl-204 beta source irradiation, indicating small but measurable ionization-induced optical property modulations. We selected a time frame when a radiation source was present that had the maximum counts among the 1.1e6 frames collected, which we induce is from single ionizing beta particle detection with this method. In summary, this novel research direction of optical property modulation detection seems promising as we head towards our goal of 10 ps CTR for ToF-PET, and we will continue to improve the sensitivity our setup with lower background, and spectral encoding of timing information.


This work is partly supported by NIH grant 5R01EB02390302, T32 CA118681, and Korea NRF grant 2020R1A6A3A03039918.

Keywords: ToF-PET, PET, CTR, Optical Properties Modulations, Schlieren
12:00 PM JS-01-05

Pixel design optimization of Photon Counting Detectors with Charge Sharing Correction for spectral CT (#530)

A. Brambilla1, K. Abdoul Karim1, J. P. Rostaing1, A. Peizerat1, L. Verger1

1 CEA - Université Grenoble Alpes, LETI-DOPT, Grenoble, France


Spectral CT relies on the use of Energy Resolved Photon Counting Detectors (PCDs) capable to provide a good energy discrimination under very high X-ray fluxes. The spectrometric performance can be defined as the capability to detect an X-ray in the correct energy bin. It is the result of a compromise on the pixel pitch. Small pixels are necessary to reduce the incident count rate and limit the impact of pile-up, but at the cost of an increase of charge sharing. The optimal pitch depends on the incident X-ray flux, but also on the use of a charge sharing correction.

We present the results of a parametric study carried by Monte Carlo simulation in order to evaluate the spectral performance of PCDs as a function of pixel size for fluxes ranging from 106 to 109 X/mm²/s. Pixels of 100 to 400 µm in steps of 50 µm were tested. We evaluate the spectral count rate efficiency and the photoelectric peak efficiency for different peaking times and with several charge correction algorithms. Finally, we simulated X-ray spectra to perform a two material decomposition and estimated the accuracy of the resulting equivalent thicknesses at low, medium and high flux.

We find that 200-250 µm pixel pitches with an optimized charge correction algorithm represent the best compromise for low to intermediate X-ray fluxes up to 5 107 X/mm²/s and show acceptable performance above 2 108 X/mm²/s. These results are obtained thanks to an original trigger method which reduces the dead time and avoids the detector paralysis .Further, we have optimized the charge sharing correction algorithm which must not be polluted at very high flux when the probability that several photons interact at the same time in neighboring pixels. Preliminary experimental results with 16 pixel array CdTe detectors are presented.

Keywords: Photon Counting Detector, Charge sharing correction, Pile-up, Spectral CT
12:15 PM JS-01-06

Capability Demonstration of a Pixelated CdZnTe Gamma-Ray Detector using a High-Altitude Balloon Flight (#594)

S. A. Abraham1, 2, Y. Zhu1, P. F. Bloser2, B. Sandoval3, J. Berry1, J. R. Deming4, G. Duran3, S. F. Nowicki2, Z. He1

1 University of Michigan, Nuclear Engineering and Radiological Sciences, Ann Arbor, Michigan, United States of America
2 Los Alamos National Laboratory, ISR-1 Space Science and Applications, Los Alamos, New Mexico, United States of America
3 Los Alamos National Laboratory, ISR-5 Space Instrument Realization, Los Alamos, New Mexico, United States of America
4 Los Alamos National Laboratory, ISR-4 Space Electronics and Signal Processing, Los Alamos, New Mexico, United States of America


In collaboration between the University of Michigan and Los Alamos National Laboratory, a pixelated CdZnTe (CZT) detector system, Orion Eagle, will be integrated into a hand-launched high-altitude balloon to demonstrate its operation in a space-like mixed-radiation environment. Orion Eagle was designed specifically for this balloon flight, with modifications made to the electrical and mechanical design to enable operation in the near-vacuum environment. Key design elements, pre-flight vacuum chamber tests, and details of the balloon flight will be discussed. The 3D position-sensing capabilities of pixelated CZT detectors allows for discrimination of background charged particles from gamma-ray events, eliminating the need for a conventional anticoincidence shield. Their unique capabilities on background rejection without an anticoincidence shield, ambient-temperature operation, gamma-ray imaging and near High Purity Germanium (HPGe) energy resolution motivate the use of CZT in future planetary exploration missions. A gamma-ray spectrometer with high energy resolution, high efficiency, low mass, low volume and high signal-to-noise ratio without the need for cyrogenics would significantly advance the state-of-the-art. The objective of the flight is to show that we can successfully detect gamma-rays while identifying/rejecting galactic cosmic rays and raise the Technical Readiness Level of pixelated CZT detector technology for space applications.


Research presented in this summary was supported by the National Nuclear Security Administration Defense Office of Nuclear Nonproliferation Research and Development. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration of the U.S. Department of Energy.

Keywords: CdZnTe, pixel detector, gamma-ray, space-like environment
12:30 PM JS-01-07

An application of a Si/CdTe Compton camera for the polarization measurement of radiative recombination x-rays (#233)

Y. Tsuzuki1, 2, S. Watanabe3, 2, S. Oishi4, N. Nakamura4, N. Numadate4, 5, H. Odaka1, 2, Y. Uchida6, H. Yoneda7, T. Takahashi2, 1

1 University of Tokyo, Department of Physics, Bunkyo, Japan
2 University of Tokyo, Kavli IPMU (WPI), Kashiwa, Japan
3 Japan Aerospace Exploration Agency, Institute of Space and Astronautical Science, Sagamihara, Japan
4 The University of Electro-Communications, Institute for Laser Science, Chofu, Japan
5 University of Tokyo, Komaba Institute for Science, Meguro, Japan
6 Hiroshima University, Department of Physics, Higashi-Hiroshima, Japan
7 RIKEN, Nishina Center, Wako, Japan


To measure the degree of polarization of hard x-rays emitted from highly charged heavy ions, in which relativistic and quantum electrodynamics effects are expected, we need a new polarimeter with higher sensitivity and accuracy than the status quo. We applied a Compton camera, which consists of pixelated multi-layer silicon (Si) and cadmium telluride (CdTe) semiconductor detectors, to observe recombination x-rays. We measured the degree of polarization of radiative recombination x-rays from highly charged krypton (Kr) ions. The uncertainty of the result is sufficiently small to probe important relativistic and quantum electrodynamics effects in future experiments.

AcknowledgmentThis research was supported by JSPS KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas `Toward new frontiers: Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams' 18H05458, 18H05463 and 19H05187, Grant-in-Aid for Scientific Research (A) 20H00153, and World Premier International Research Center Initiative (WPI), MEXT, Japan.
Keywords: cadmium telluride, Compton camera, radiative recombination, silicon, quantum electrodynamics
12:45 PM JS-01-08

CsPbBr3 Semiconductor Gamma Spectrometer (#1128)

Z. He1, M. Petryk1, Y. He2, M. G. Kanatzidis2

1 The University of Michigan, Nuclear Engineering and Radiological Sciences, Ann Arbor, Michigan, United States of America
2 Northwestern Universty, Department of Chemistry, Evaston, Illinois, United States of America


CsPbBr3 has been investigated as an alternative semiconductor gamma-ray spectrometer to CdZnTe, for its high stopping power and lower cost. Good energy resolution of 1.9% - 2.0% FWHM at 662 keV for single-pixel events was observed on a CsPbBr3 prototype detector with a thickness of 9.6 mm. This shows good spectroscopic resolution and high detection efficiency can be achieved on CsPbBr3 perovskite semiconductor detectors. The observed trapping of holes drifting through the entire 9.6 mm thickness is very small, indicating that the lifetime of holes is much longer than 120 us. Given the measured mobility of holes to be about 22 cm2/V.s, this leads to a hole mobility-lifetime product to be much higher than 2.6x10-3 cm2/V, the highest value observed experimentally. This high value of hole mu-tau is consistent with the observed good energy resolution.

AcknowledgmentThis material is based upon work supported by the Defense Threat Reduction Agency under Award # HDTRA12020002. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DTRA.
Keywords: CsPbBr3, Perovskite, semiconductor, gamma-ray spectrometers, room-temperature

Our exhibitors and sponsors – click on name to visit booth: