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Emerging Applications and New Concepts in Medical Imaging

Session chair: Badawi , Ramsey D. (University of California, Davis, Departments of Radiology and Biomedical Engineering, Davis, USA); Ziegler , Sibylle (University Hospital LMU Munich, Nuclear Medicine, München, Germany)
Shortcut: M-13
Date: Friday, 22 October, 2021, 9:15 AM - 11:15 AM
Room: MIC - 1
Session type: MIC Session


Click on an contribution to preview the abstract content.

9:15 AM M-13-01

A γ-PET Prototype: Detector Characterization, Commissioning and first Imaging (#801)

T. M. Binder1, 2, V. Anagnostatou1, M. Safari1, K. Kamada4, H. G. Kang3, M. Nitta1, A. Zoglauer5, K. Parodi1, T. Yamaya3, P. G. Thirolf1

1 Ludwig-Maximilians_Universität Munich, Chair for experimental and medical physics, Garching, Germany
2 KETEK GmbH, Munich, Germany
3 Institute for Quantum Medical Science, National Institutes for Quantum and Radiological Science and Technology (QST), Chiba, Japan
4 C&A Corporation, Sendai, Japan
5 University of California at Berkeley, Space Sciences Laboratory, Berkeley, United States of America


The γ-PET imaging modality is capable of detecting triple-coincidences of two positron-annihilation photons and a higher-energetic gamma-ray from the deexcitation of an excited β+ - decay daughter nucleus, resulting in a potential sensitivity improvement compared to conventional PET. γ-PET can be realized either by combining a conventional PET scanner with (one or more) Compton camera arms, converting a PET scanner by inserting a scatterer array into a ring of PET detectors or by a number of Compton camera arms. We developed a γ-PET prototype consisting of two 16×16 GAGG scintillator arrays (1.6 mm crystal pitch) as PET arrangement and a single Compton camera arm consisting of a GAGG array (as scatterer) followed by a 16×17, 17×18 and 18×18 three-layered staggered LYSO array (1.4 mm crystal pitch) (absorber) placed perpendicular to the PET detectors. All scintillators were read-out using SiPM arrays. The prototype was characterized by acquiring PET and Compton data of a 22Na point source. While in PET-only mode, a spatial resolution (SR) of 2 mm (FWHM) with an accuracy (Δx/y= x/ytrue – x/yrecon) of ~100 μm could be demonstrated by shifting the source along a line in 1 mm steps, in Compton-only mode a SR (FWHM) of 3.6 mm (6.0 mm) [8.7 mm] was achieved at a source-to-detector distance of 11 mm (50 mm) [55 mm] with an angular resolution measure of 15.7° (8.2°) [7.6°]. The obtained accuracy in the detector plane was found to be ~1 mm. Simultaneously taken Compton and PET data were combined and resulted in a good 3D imaging capability with an accuracy along the x-axis of 1.5 mm and ~300 μm along the y/z plane (PET imaging plane) and a spatial resolution in this plane of 2.9 mm. Even though the rather limited covered solid angle of the first prototype, triple-coincidences could be detected. The functionality of the prototype for PET, Compton and γ-PET imaging was demonstrated.


Supported by BFS, EU MSCA-IF “HYPPOCRATE, EU ERC Consolidators Grant “SIRMIO” and the NIRS-QST.

Keywords: Gamma-PET, triple-coincidences, Compton camera, PET, SiPM
9:30 AM M-13-02

pO2 measurement using positronium (#22)

K. Shibuya1, 2, H. Saito1, F. Nishikido2, H. Tashima2, M. Takahashi2, T. Yamaya2

1 University of Tokyo, Graduate School of Arts and Sciences, Tokyo, Japan
2 National Institute for Quantum and Radiological Science and Technology, Quantum Life and Medical Science Directorate, Chiba, Japan


We propose a new method to increase the amount of information obtained from PET using positronium (Ps). Ps is a hydrogen-like atom consisting of a positron and an electron and is formed spontaneously in the human body during a PET scan. Because the lifetime of Ps, i.e., to decay into gamma-ray photons, depends on the chemical environment, especially the oxygen partial pressure (pO2), new biomedical information can be obtained by measuring the lifetime of Ps. In this work, we measured the Ps lifetimes in three samples: N2-saturated water (pO2=0 mmHg), air-saturated water (pO2=159 mmHg), and O2-saturated water (pO2=750 mmHg), and confirmed that the decay rate (the inverse of the lifetime) was linearly related to pO2. The linearity is because the probability of Ps encountering O2 molecules is proportional to pO2. The uncertainty of the measurement corresponds to a pO2 resolution of 17 mmHg with 100 million counts  (or 5 mmHg with 1 billion counts) from the region-of-interest. This resolution is sufficient to distinguish the pO2 of cancer cells (ca. 6 mmHg) from the pO2 of healthy cells (ca. 41 mmHg) in a human liver. Therefore, the Ps lifetime can be applied for imaging hypoxic cancer cells, which are resistant to radiotherapy as well as chemotherapy. Implementation of Ps lifetime imaging in PET requires localized positional information, i.e. a combination with a time-of-flight kernel or Compton cone; this is because a distribution of pO2 in vivo would mix Ps lifetime components via projective observation in PET, and the localized positional information can reduce the mixing. In addition, we will discuss a mathematical approach, i.e., inverse Laplace transform, to resolve the mixed components.


This work was partially funded by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant nos. 21K03416, 20H05667 and 20K12683.

Keywords: PET, positronium lifetime, hypoxia imaging, cancer, inverse Laplace trasform
9:45 AM M-13-03

Quantum sensing of pH around local environment via cascade photon angular correlation in nuclear medicine imaging (#436)

F. Sensui1, M. Uenomachi2, K. Shimazoe1, 5, H. Z. Zhong1, H. Takahashi1, H. Tomita3, K. Kamada4

1 University of Tokyo, Graduate School of Engineering, Tokyo, Japan
2 RIKEN, Nishina Center for Accelerator-BasedScience, Saitama, Japan
3 University of Nagoya, Nagoya, Japan
4 University of Tohoku, Sendai, Japan
5 PRESTO-JST, Tokyo, Japan

This work was partially carried out with the support of Isotope Science Center, The University of Tokyo.


Nuclear medical imaging, such as PET and SPECT, provides very high sensitivity in molecular functional imaging. Our group has been developing DPECT (Double Photon Emission CT) to enhance nuclear medicine diagnostics using cascade nuclides that emit multiple gamma rays simultaneously. There is an angular correlation between the two gamma rays, which depends on the local surroundings of the nuclide. Thus, it is possible to detect the local environment around the nuclide by examining the angular correlation of the emitted gamma rays. Here, we proposed and investigated a novel sensing and imaging method to detect pH and chemical state around the radioisotope tracer by monitoring the change in angular correlation of cascade nuclides. A proof-of-concept study shows the capability to detect different pH along with the accumulation imaging with the proposed technique, which can be used for a highly accurate cancer imaging method in the future. We measured the angular correlation of pH-adjusted 111InCl3 aqueous solution with GAGG scintillators and a collimator. There was no significant change in the angular correlation among the samples with pH 1~3. However, for the samples with pH 5 or higher, a decrease of about 5% was observed around the 90 degree emission angle, while an increase of 5% was observed around 0 degree and 180 degree. By applying the degree of change in the angular correlation to collimator-based imaging, We succeeded to make multiple samples imaging and perform positional decomposition by imaging and pH decomposition by angular correlation simultaneously.

Keywords: Angular Correlation, Double Photon, Nuclear Medicine, Quantum Sensing
10:00 AM M-13-04

Imaging of hydroxyl radical (OH-) distributions using luminol water during irradiation of low-energy X-rays (#197)

S. Yamamoto1, T. Yabe1, Y. Hirano1

1 Nagoya University, Graduate School of Medicine, Nagoya, Japan


Hydroxyl radicals (OH-) play important roles in the biological effects of radiation exposure or radiation therapy, and the distribution of OH- in water during irradiation of radiations are of interest. However, real-time measurement of OH- distribution during irradiation has not yet been achieved because the detection of OH- has been difficult. To make such distribution measurements possible, we attempted imaging of the light emitted from luminol water during irradiation of low-energy X-rays. Imaging of the light emitted from luminol water was carried out using a cooled charge-coupled device (CCD) camera as X-rays were irradiated to the luminol water at a lower energy than the Cherenkov-light threshold, i.e., 100 kVp. The light emission of luminol water was 25 times higher than that of water, and clear images of light distributions were measured for the luminol water. We also carried out such imaging of luminol water using the addition of a radical scavenger to the luminol water so as to confirm that the emitted light was from the OH- produced in water. With the addition of the radical scavenger to the luminol water, the light intensity decreased as the weight of the scavenger increased. With these results, we confirmed that the detected light distribution in luminol water could be attributed to the OH- produced by the X-ray irradiation.

Keywords: hydroxyl radical, X-rays, luminol water, optical imaging, distribution
10:15 AM M-13-05

Imaging of polarized components of Cerenkov-light of water during high-energy X-ray irradiation and application for dose distribution measurement (#844)

C. Toyonaga1, S. Yamamoto1, T. Yabe1, 2, K. Okudaira2, K. Yogo1, Y. Hirano1

1 Nagoya University, Graduate School of Medicine, Nagoya, Japan
2 Nagoya University Hospital, Nagoya, Japan


Measurements of high-energy X-ray dose distribution from the medical linear accelerators (LINAC) are important for quality control (QC) of the system. Although optical imaging is useful for measuring the X-ray dose distribution, depth profiles showed underestimation in the deep area due to the angular dependency of the Cerenkov-light generated in water. In this study, we used a polarizer to separate the polarized components in Cerenkov-light, and corrected the angular dependency of the Cerenkov-light. A water phantom, a cooled charge-coupled device (CCD) camera, and a polarizer plate were installed in the black box. 6 MV and 10 MV X-rays were irradiated from the upper side of the water phantom, and the Cerenkov-light generated in water was imaged by changing the polarization axis of the polarizer plate with a cooled CCD camera. With the polarizer parallel to the beam, the intensity was ~50 % higher than that measured with the polarizer perpendicular to the beam and we could obtain two types of images with different distributions. By subtracting the image measured with the polarizer perpendicular to the beam from the image measured with the polarizer parallel to the beam, we could obtain the image of only the components polarized in the forward direction. By subtracting the polarized components image from the image measured without polarizer, we could obtain the image with smaller angular dependency of Cerenkov-light. By the correction, we succeeded to obtain a distribution almost the same as the dose distribution. We conclude that polarizer plate can improve the accuracy of the dose distribution in opti

Keywords: polarization, optical imaging, X-ray beams, LINAC, Cerenkov-light
10:30 AM M-13-06

A Benchtop High-Sensitivity X-ray Fluorescence Emission Tomography (XFET) System Comprising Full Ring CdTe Spectrometers and Liquid-metal-jet-based X-ray Source (#1208)

X. Nie1, A. V. Avachat2, 3, E. M. Zannoni2, 1, L. Cai1, M. Anastasio2, 3, P. L. Riviere4, L. Meng1, 3

1 University of Illinois at Urban Campaign, Department of Nuclear, Plasma and Radiological Engineering, Urbana, Illinois, United States of America
2 University of Illinois at Urban Campaign, Department of Bioengineering, Urbana, Illinois, United States of America
3 University of Illinois at Urban Campaign, Beckman Institute of Advanced Science and Technology, Urbana, Illinois, United States of America
4 University of Chicago, Department of Radiology, Chicago, Illinois, United States of America


    Benchtop X-ray fluorescence emission tomography (XFET) is an emerging imaging modality that images spatial distribution and concentration of high-Z elements. XFET measures the emission of characteristic X-rays from a sample under radiation excitation without destroying the sample. Metal-based antitumor drugs are widely used in cancer therapy. For instance, cisplatin (Pt-based) plays a major role in the treatment of bladder, head, and neck, ovarian, testicular, and non-small cell lung cancers. Additionally, metal-based nanoparticles (NPs) have gained increasing interest as a novel carrier for investigating targeted drug delivery and therapeutic effect. However, XFET is seriously constrained by the low signal-to-noise ratio, high dose, and long acquisition time, resultant from the small cross section of X-ray photons to stimulate X-ray fluorescence from the target metal atoms and high Compton background.

   In this presentation, we report our development of a high-performance full-ring XFET system that consists of 20 ultrahigh HEXITEC CdTe detectors coupled to multi-slit collimators and a liquid metal-jet-based x-ray source toward providing an ultrahigh sensitivity for XFET of high-Z metal elements contained in nanoparticles.

Keywords: X-ray, Fluorescence, XFET, CdTe, liquid jet source
10:45 AM M-13-07

Simultaneous readout from an integrated gamma-ultrasound probe (#1277)

Y. Park1, 2, G. Kim1, 2, M. N. Ullah3, 1, K. - S. Lee1, H. Choi4, J. - Y. Yeom1, 2

1 Korea University, Bioengineering, Seoul, Republic of Korea
2 Korea University, Interdisciplinary Program in Precision Public Health, Seoul, Republic of Korea
3 Stanford University, Radiology, School of Medicine, California, United States of America
4 Kumoh National Institute of Technology, Medical IT Convergence Engineering, Gumi, Republic of Korea


We propose a highly integrated Gamma-Ultrasound (γ-US) probe and data acquisition system for intraoperative applications. A highly integrated detector was designed to detect gamma radiation as well as ultrasound signal simultaneously. The novel detector consists of a piezoelectric crystal attached to a tungsten compound as the backing material while a small hole was created in the middle of tungsten body for placing a Ce:GAGG scintillator for radiation detection. The silicon photomultiplier (SiPM) was attached to one end of the scintillator. An integrated receiver circuit was also designed to acquire the US and Gamma signal simultaneously using a single readout channel. The data was acquired using an oscilloscope and processed with MATLAB in a computer. The signal to noise ratio (SNR) and axial resolution of 16.3 dB and 1.55 mm were achieved respectively for the US. In the case of the gamma probe, the energy resolution of full-width-half-maximum (FWHM) was 21.2% for Co-57 gamma radiation while 3.2 mm spatial resolution was acquired. Scanning experiments of a water tank with a sealed radiation source and a non-radioactive plastic plate as target was also performed to validate the feasibility of the proposed dual-modality γ-US probe.

AcknowledgmentThis research was funded by the National Research Foundation of Korea (NRF) grant funded by the government (MSIT) (No. 2020R1A2C2007376, No. 2020M2A8A4023713)
Keywords: Dual-modality, Gamma, Intraoperative probe, Ultrasound
11:00 AM M-13-08

Imaging simulation of simultaneous PET and SPECT with collimator detectors having a pinhole aperture (#1130)

M. Nitta1, H. Tashima2, T. Yamaya2, K. Parodi1

1 Ludwig Maximilian University Munich, Medical Physics, Munich, Bavaria, Germany
2 National Institutes for Quantum and Radiological Science and Technology, Chiba, Japan


SPECT and PET are commonly used in clinical nuclear medicine and pre-clinical molecular imaging. In order to obtain projection data, PET detects annihilation photons by coincidence measurement while SPECT detects gamma-ray via a mechanical collimator. Therefore, the difference in imaging principle prevents multi-functional simultaneous imaging, which helps diagnosis, dynamic analysis of metabolism, development of drug delivery systems. In this study, we proposed a novel nuclear medicine device to obtain simultaneous multi-functional images of SPECT and PET tracers. Our idea was to substitute a mechanical collimator for SPECT to a collimator detector, a layered pixelated scintillation detector having a collimator hole. A pinhole aperture was formed by removing the scintillators. We conducted a Monte-Carlo simulation to show the feasibility. We defined a detector unit composed of a collimator detector and a bottom detector. The collimator detector was configured with GAGG scintillators with a pixel size of 1.5 mm x 1.5 mm x 5 mm composing a 33 x 33 x 3 array. A pinhole aperture was created by removing 1 x 1, 3 x 3, and 5 x 5 scintillator pixels from the 1st, 2nd, and 3rd layers, respectively. The bottom detector was placed to obtain projection data for SPECT was composed of a 48 x 48 array of 1 mm x 1 mm x 10 mm GAGG scintillators. We arranged 16 detector units to form a ring of 300 mm in diameter for human head imaging. We modeled 141 keV gamma-ray sources and positron sources. We evaluated the sensitivity and reconstructed images of those sources by the energy discrimination. The sensitivity for the SPECT radionuclide and the PET radionuclide was 0.042%(421 counts/MBq) and 0.92% respectively at the center of the scanner. Both PET and SPECT spherical sources with a diameter of 4 mm and with 8 mm separation was clearly resolved. The result showed the proposed device is feasible in obtaining both SPECT and PET images simultaneously.

Keywords: SPECT, PET, simultaneous imaging, multi-funcitional imaging, dual isotope imaging

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