IEEE 2021 NSS MIC

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JOINT NSS MIC

Session chair: Goertzen , Andrew L. (University of Manitoba, The Winnipeg PET Imaging Centre, Winnipeg, Canada); Pozzi , Sara A. (University of Michigan, Department of Nuclear Engineering and Radiological Sciences, Ann Arbor, USA)
 
Shortcut: JS-02
Date: Tuesday, 19 October, 2021, 7:00 AM - 8:45 AM
Room: JOINT
Session type: Joint Session

Contents

Click on an contribution to preview the abstract content.

7:00 AM JS-02-01

Metascintillators: New results for TOFPET applications (#247)

P. Lecoq1, 2, G. Konstantinou2, L. Moliner Martinez1, R. Latella2, A. Gonzalez1, J. M. Benlloch1, J. Nuyts3

1 Polytechnic University, CSIC, I3M, Valencia, Spain
2 Multiwave Metacrystal SA, Geneva, Switzerland
3 KU Leuwen, Nuclear Medicine & Molecular Imaging MIRC, Leuwen, Belgium

Abstract

We report on the progress on realistic size metascintillator heterostructures for time-of-flight PET applications. The aim of this work was to optimize the performance of a first generation of metascintillators combining LYSO or BGO plates providing the required high stopping power and energy resolution, interleaved with fast scintillator plates producing a bunch of prompt photons from the energy leakage of the recoil photoelectric electron. 14 LYSO-based and 15 BGO-based metascintillator configurations have been studied. A detailed Monte Carlo simulation was first performed on each of these configurations to extrapolate from lab measurements the expected 511keV detector sensitivity and the Detector Time Resolution distribution (DTR) resulting from fluctuations in the amount of energy leakage to the faster scintillator. An analytic algorithm was then applied to determine an equivalent CTR from the random association of the DTR distributions from two similar metapixels in coincidence. This equivalent CTR is calculated in order to obtain the same variance in the reconstructed image as the combination of the DTR distributions of 2 metapixels. This approach allowed a selection of the most promising configurations. A few of them have been assembled, both LYSO- and BGO-based and measured in the lab on a coincidence bench with a 22Na radioactive source. Preliminary results confirm that with these simple, still non-optimised configurations an equivalent CTR of 150ps for BGO-based and 140ps for LYSO-based metapixels of realistic size can be obtained, these values being still limited by the choice of the simple and cheap fast scintillator for these first tests.  It will be shown that a second generation of metascintillators we are presently developing (being patented) using much faster nanocrystal-based scintillators and more elaborate geometries will significantly improve these already quite encouraging results.

Keywords: TOFPET, Time-of-Flight, scintillator, metamaterial, nanocrystal
7:15 AM JS-02-02

Architecture and Characterization of a CMOS 3D-Stacked FSI Multi-Channel Digital SiPM for Time-of-Flight PET Applications (#1376)

F. Gramuglia1, A. Muntean1, C. A. Fenoglio1, E. Venialgo4, M. - J. Lee2, S. Lindner1, M. Motoyoshi3, A. Ardelean1, C. Bruschini1, E. Charbon1

1 EPFL, Switzerland, STI, Neuchatel, Switzerland
2 KIST, Republic of Korea, Seoul, Republic of Korea
3 T-Micro, Miyagi, Japan
4 TUDelft, Department of Precision and Microsystems Engineering, Delft, Netherlands

Abstract

We discuss the architecture and characterization of an advanced frontside-illuminated (FSI) multi-channel digital silicon photomultiplier (MD-SiPM) fabricated in 0.18 µm/0.18 µm 3D-stacked CMOS technology. The top-tier chip houses the FSI photodetectors, while the bottom-tier chip is dedicated to photon timestamping, signal processing, and communication logic. The total chip size is of 7.5×4.2 mm2, comprising two arrays of 8×8 clusters, each composed of 64 single-photon avalanche diodes (SPADs).

The top-tier chip features two matrices of 64×64 SPADs, each connected to the bottom-tier chip by means of a dedicated metal through-silicon via. The bottom-tier chip features an event-driven time-stamping architecture with no fast clock distributed on chip. Time stamps are generated by 128+1 time-to-digital converters (TDCs) and a winner-take-all tree, used to determine the address of the first SPAD that fired. Each TDC is based on a multi-path gated ring oscillator and a bank of latches that captures the state of the oscillator upon photon detection. A counter extends the range to 18 bits with an LSB of 15 ps. The read-out architecture does offer the possibility of selective read-out and of random-access, which have proven invaluable for testing purposes.

A custom user interface has been designed in C++ to connect a host PC to the sensor via a Kintex-7 FPGA-based board. The user interface has been designed to allow full sensor and PCB configuration (voltages and TDC calibration parameters), sensor testing and result display. A laser-based setup has been assembled for electro-optical characterization of key parameters such as dark count rate, hot pixel distribution, TSV yield, response linearity and saturation. The corresponding measurements are complemented by preliminary radiation measurements on LYSO scintillators coupled to a Na-22 source.

Acknowledgment EPFL gratefully acknowledges thegenerous support of the Swiss National Science Foundation.
Keywords: 3D-integration, A-SiPM, D-SiPM, FSI, PET
7:30 AM JS-02-03

SPAD Microcells with 12.1 ps SPTR for SiPMs in TOF-PET Applications (#1371)

F. Gramuglia1, M. - L. Wu1, M. - J. Lee2, C. Bruschini1, E. Charbon1

1 EPFL, Switzerland, STI, Neuchatel, Switzerland
2 KIST, Republic of Korea, Seoul, Republic of Korea

Abstract

In this work, we present a single-photon avalanche diode (SPAD) microcell, at the core of each silicon photomultiplier, capable of delivering single-photon time resolution (SPTR) of 12.1 ps FWHM. The device, fabricated in 180 nm CMOS technology, measures 25, 50, and 100 µm and can be scaled to large arrays. The microcell features a localized quenching and active recharge circuitry and it achieves peak photon detection probability (PDP) of 55% at 480 nm and 6 V excess bias with a large sensitivity spectrum covering NUV, VIS, and NIR. The normalized dark count rate (DCR) is 0.2 cps/μm2 at the same excess bias. The SPAD microcell embeds active recharge circuitry capable of reducing the dead time to 3 ns. At this level, the measured afterpulsing probability is as low as 0.1% at the same excess bias.

AcknowledgmentThe Authors would like to thank Olivier Bernard for the fruitfull discussions and the technical supporton the laser setup. EPFL also gratefully acknowledges thegenerous support of the Swiss National Science Foundation.
Keywords: SPAD, SiPM, SPTR, PET, PDP
7:45 AM JS-02-04

Initial Demonstration of Quantum PET: 2D Positronium Lifetime Imaging Using a Pair of TOF Detectors (#704)

S. Takyu1, H. Tashima1, K. Shibuya2, F. Nishikido1, M. Takahashi1, T. Yamaya1

1 National Institutes for Quantum and Radiological Science and Technology, Institute for Quantum Medical Science, Chiba, Japan
2 University of Tokyo, Tokyo, Japan

Abstract

Positronium (Ps) may be generated in the human body during PET examinations. Ps is formed when a positron interacts with an electron and is quickly followed by annihilation yielding two photons. As the Ps lifetime reflects the surrounding electron density, we are aiming at its use for novel hypoxia PET imaging. The Ps lifetime is obtained from the time difference between the detection time of a prompt gamma ray and that of the annihilation photon. Sc-44 (half-life, 4 hours), which emits a positron and a 1157 keV prompt gamma ray almost at the same time, is a candidate radionuclide for clinical use, while it can be replaced by Na-22 for laboratory experiments. In addition to conventional TOF-PET, whole gamma imaging (WGI), PET combined with Compton camera, is expected to realize the Ps lifetime imaging. The source position can be localized at the intersection points between the line-of-response determined by the annihilation photon coincidence and the Compton cone determined by the prompt gamma ray. In this study, as a first step, we demonstrated a “quantum PET” concept, Ps lifetime imaging, by discriminating two materials with different Ps lifetimes. Two Hamamatsu TOF-PET module detectors having a 250 ps coincidence resolving time were oppositely placed at a distance of 10 cm. Two Na-22 sources covered with a thin film, each of which was sandwiched with each of two different standard materials, were placed at the middle point between the two module detectors. The standard materials had the known electron density corresponding to the Ps lifetimes of 1.62 ± 0.05 ns and 2.10 ± 0.05 ns, respectively. Extracting triple coincidence events of the 1275 keV prompt gamma ray and the annihilation photons from the measured data, a 2D projection PET image and the Ps lifetime spectrum of the pixel at each source position were obtained. The calculated Ps lifetimes were 1.64 ± 0.05 ns and 2.10 ± 0.07 ns, respectively, which provided the initial proof of the quantum PET concept.

Keywords: Positronium lifetime measurement, Oxygen sensing, Hypoxia imaging, Whole gamma imaging, Sc-44
8:00 AM JS-02-05

Titanium‐44 phantom production and PET imaging for photon activation analysis (#1268)

T. Fukuchi1, H. Kikunaga2, H. Haba3, S. Yamamoto4, Y. Watanabe1

1 RIKEN, Center for Biosystems Dynamics Research, Kobe, Japan
2 Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
3 RIKEN, Nishina Center for Accelerator-Based Science, Wako, Japan
4 Nagoya University, Department of Radiological and Medical Laboratory Science, Nagoya, Japan

Abstract

We have been developing an advanced PET system for multiple tracer imaging in the field of life science. The system, which we call multiple-isotope PET (MI-PET), can detect not only annihilation photons but also the prompt γ‐ray to identify the tracer nuclide by using the information of the prompt γ-ray coinciding with annihilation photons. In addition to bio-imaging, we are researching the possibility of application of MI‐PET for a photon activation analysis. In the photon activation analysis, positron emitter is produced from nonradioactive elements in an object by irradiation of the high-energy photons. However, in the photonuclear reaction, various radionuclides are produced other than objective positron emitter. Therefore, an extraction of the objective positron emitter from background activities is required for the PET imaging. To evaluate the performance of MI‐PET for this extraction imaging, we produced 44Ti/44Sc phantoms from titanium targets by irradiation of the high-energy photons, and performed an imaging experiment by MI-PET. As a result, we succeeded in reconstructing the 44Ti/44Sc phantom image using triple-coincidence of annihilation photons and the prompt γ‐ray in spite of approximately 67 times of background activities, which makes harder for imaging by conventional double‐coincidence PET imaging.

AcknowledgmentThis work was supported in part by JSPS KAKENHI Grant Number JP20K12704.
Keywords: Activation analysis, Gamma-ray, Phantoms, Positron emission tomography
8:15 AM JS-02-06

Establishing an Integrated Animal PET/CT/RT for Improving Current and Enabling New Preclinical Radiation Oncology Research (#1153)

X. Cheng1, D. Yang1, Y. Shao1

1 University of Texas Southwestern Medical Center, Department of Radiation Oncology, Dallas, Texas, United States of America

Abstract

One critical yet still missing imaging capability of all current commercial small animal CT image-guided irradiators (CT/RT) is the onboard PET functional image guidance. Such integrated PET/CT/RT would enable streamlined preclinical PET/CT image-guide radiation therapy (IGRT) research to significantly improve the accuracy of tumor delineation, radiation targeting, and workflow and efficiency, which should ultimately enhance the outcome and compatibility to clinical PET/CT IGRT for translational investigations, and potentially open the door for new and advanced, quantitative, molecular image-guided preclinical/translational radiation oncology research that are beyond the limit of CT/RT. To address this unmet technical challenge yet urgent research need, we have developed a compact, lightweight, yet still high-resolution small animal PET and successfully integrated it within an existing small animal CT/RT irradiator (XRD 225cX, PXI). PET provides an 8 cm diameter in-plane and 3.5 cm axial field of view (FOV), uniform ~1.1 mm spatial resolution within 6 cm diameter FOV and ~2% sensitivity at the center of FOV. PET/CT dual-modality image acquisition and co-registration were implemented and tested, and subsequently the images of both an ultra-micro hot-rods phantom filled with F-18 and a tumor-bearing mouse injected with FDG were also acquired and evaluated. The results show the accurate onboard PET/CT images were achieved and as expected the much clearly defined tumor volume and boundary were obtained with the PET functional image. In summary, the first preclinical integrated PET/CT/RT has been established, and its capability along with the potential advantage and additive value to the future preclinical/translational radiation oncology research were demonstrated. More quantitative studies, including the use of different animal tumor models, are ongoing and will be reported in the conference.

Acknowledgment

This study is supported in part by grants from National Institute of Health (1R01EB019438, 1R01EB019438-04S, 1R01CA218402) and a career development grant from the Department of Radiation Oncology, University of Texas Southwestern Medical Center.

Keywords: IGRT, PET, DOI, preclinical, irradiator
8:30 AM JS-02-07

A Process to Colorize and Assess Visualizations of Noisy X-Ray Computed Tomography Hyperspectral Data of Materials with Similar Spectral Signatures (#309)

J. Clifford1, E. Kemp1, B. Limpanukorn1, E. S. Jimenez1

1 Sandia National Laboratories, Albuquerque, New Mexico, United States of America

Abstract

Dimension reduction techniques have frequently been used to summarize information from high dimensional hyperspectral data, usually done in effort to classify or visualize the materials contained in the hyperspectral image. The main challenge in applying these techniques to Hyperspectral Computed Tomography (HCT) data is that if the materials in the field of view are of similar composition then it can be difficult for a visualization of the hyperspectral image to differentiate between the materials. We propose novel alternative methods of preprocessing and summarizing HCT data in a single colorized image and novel measures to assess desired qualities in the resultant colored image, such as the contrast between different materials and the consistency of color within the same object. Proposed processes in this work include a new majority-voting method for multi-level thresholding, binary erosion, median filters, PAM clustering for grouping pixels into objects (of homogeneous materials) and mean/median assignment along the spectral dimension for representing the underlying signature, UMAP or GLMs to assign colors, and quantitative coloring assessment with developed measures. Strengths and weaknesses of various combinations of methods are discussed. These results have the potential to create more robust material identification methods from HCT data that has wide use in industrial, medical, and security-based applications for detection and quantification, including visualization methods to assist with rapid human interpretability of these complex hyperspectral signatures.

Keywords: x-ray computed tomography, hyperspectral imaging, colorization, data visualization

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