Dr. Gonzalez-Montoro's research interests involve the development of novel Positron Emission Tomography (PET) instrumentation for an accurate in vivo imaging of the metabolic processes and the study of diseasses in humans and small animals.
In addition to obtain a high efficiency of PET scanners when combined with MRI or CT scanners, my research focusses on instrumentation projects related to enhance the sensitivity and 3D spatial, and/or temporal resolutions.

Honors & Awards

  • Ronald J. Jaszczak Graduate Award, IEEE Nuclear & Plasma Sciences Society (2020)

Professional Education

  • Bachelor of Science, Universidad De Valencia (2014)
  • Master of Science, Universidad De Valencia (2015)
  • Doctor of Philosophy, Universidad De Valencia (2019)

Lab Affiliations

All Publications

  • Study of optical reflectors for a 100ps coincidence time resolution TOF-PET detector design. Biomedical physics & engineering express Gonzalez-Montoro, A., Pourashraf, S., Lee, M. S., Cates, J. W., Levin, C. S. 2021


    Positron Emission Tomography (PET) reconstructed image signal-to-noise ratio (SNR) can be improved by including the 511 keV photon pair coincidence time-of-flight (TOF) information. The degree of SNR improvement from this TOF capability depends on the coincidence time resolution (CTR) of the PET system, which is essentially the variation in photon arrival time differences over all coincident photon pairs detected for a point positron source placed at the system center. The CTR is determined by several factors including the intrinsic properties of the scintillation crystals and photodetectors, crystal-to-photodetector coupling configurations, reflective materials, and the electronic readout configuration scheme. The goal of the present work is to build a novel TOF-PET system with 100 picoseconds (ps) CTR, which provides an additional factor of 1.5-2.0 improvement in reconstructed image SNR compared to state-of-the-art TOF-PET systems which achieve 225 - 400 ps CTR. A critical parameter to understand is the optical reflector's influence on scintillation light collection and transit time variations to the photodetector. To study the effects of the reflector covering the scintillation crystal element on CTR, we have tested the performance of four different reflector materials: Enhanced Specular Reflector (ESR) -coupled with air or optical grease to the scintillator; Teflon tape; BaSO4 paint alone or mixed with epoxy; and TiO2 paint. For the experimental set-up, we made use of 3*3*10 mm3 fast-LGSO:Ce scintillation crystal elements coupled to an array of silicon photomultipliers (SiPMs) using a novel "side-readout" configuration that has proven to have lower variations in scintillation light collection efficiency and transit time to the photodetector. Results show CTR values of 102.0±0.8, 100.2±1.2, 97.3±1.8 and 95.0±1.0 ps full-width-half-maximum (FWHM) with non-calibrated energy resolutions of 10.2±1.8, 9.9±1.2, 7.9±1.2, and 8.6±1.7 % FWHM for the Teflon, ESR (without grease), BaSO4 (without epoxy) and TiO2 paint treatments, respectively.

    View details for DOI 10.1088/2057-1976/ac240e

    View details for PubMedID 34488203

  • High-resolution time-of-flight PET detector with 100 ps coincidence time resolution using a side-coupled phoswich configuration. Physics in medicine and biology Lee, M. S., Cates, J. W., Gonzalez-Montoro, A., Levin, C. S. 2021; 66 (12)


    Photon time-of-flight (TOF) capability in positron emission tomography (PET) enables reconstructed image signal-to-noise ratio (SNR) improvement. With the coincidence time resolution (CTR) of 100 picosecond (ps), a five-fold SNR improvement can be achieved with a 40 cm diameter imaging subject, relative to a system without TOF capability. This 100 ps CTR can be achieved for aclinically relevantdetector design (crystal element length ≥20 mm with reasonably high crystal packing fraction) using a side-readout PET detector configuration that enables 511 keV photon interaction depth-independent light collection efficiency and lower variance in scintillation photon transit time to the silicon photomultiplier (SiPM). In this study, we propose a new concept of TOF-PET detector to achieve high (<2 mm) resolution, using a 'side-coupled phoswich' configuration, where two crystals with different decay times (taud) are coupled in a side-readout configuration to a common row of photosensors. The proposed design was validated and optimized with GATE Monte Carlo simulation studies to determine an efficient detector design. Based on the simulation results, a proof-of-concept side-coupled phoswich detector design was developed comprising two LSO crystals with the size of 1.9*1.9*10 mm3with decay times of 34.39 and 43.07 ns, respectively. The phoswich crystals were side-coupled to the same three 4*4 mm2SiPMs and detector performances were evaluated. As a result of the experimental evaluation, the side-coupled phoswich configuration achieved CTR of 107±3 ps, energy resolution of 10.5%±1.21% at 511 keV and >95% accuracy in identifying interactions in the two adjacent 1.9*1.9*10 mm3crystal elements using the time-over-threshold technique. Based on our results, we can achieve excellent spatial and energy resolution in addition to 100 ps CTR with this novel detector design.

    View details for DOI 10.1088/1361-6560/ac01b5

    View details for PubMedID 34106089

  • Evolution of PET Detectors and Event Positioning Algorithms Using Monolithic Scintillation Crystals IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES Gonzalez-Montoro, A., Gonzalez, A. J., Pourashraf, S., Miyaoka, R. S., Bruyndonckx, P., Chinn, G., Pierce, L. A., Levin, C. S. 2021; 5 (3): 282-305
  • Scalable electronic readout design for a 100 ps coincidence time resolution TOF-PET system. Physics in medicine and biology Pourashraf, S. n., Gonzalez-Montoro, A. n., Won, J. Y., Lee, M. S., Cates, J. W., Zhao, Z. n., Lee, J. S., Levin, C. S. 2021


    We have developed a scalable detector readout design for a 100 ps coincidence time resolution (CTR) time of flight (TOF) positron emission tomography (PET) detector technology. The basic scintillation detectors studied in this paper are based on 2×4 arrays of 3×3×10 mm³ "fast- LGSO:Ce" scintillation crystals side- coupled to 6×4 arrays of 3×3 mm² silicon photomultipliers (SiPMs). We employed a novel mixed-signal front-end electronic configuration and a low timing jitter Field Programming Gate Array (FPGA)-based time to digital converter (TDC) for data acquisition. Using a 22 Na point source, >10,000 coincidence events were experimentally acquired for several SiPM bias voltages, leading edge time-pickoff thresholds, and timing channels. CTR of 102.03 ± 1.9 ps full-width-at-half-maximum (FWHM) was achieved using single 3×3×10 mm³ "fast- LGSO" crystal elements, wrapped in Teflon tape and side coupled to a linear array of 3 SiPMs. In addition, the measured average CTR was 113.4 ± 0.7 ps for the side- coupled 2×4 crystal array. The readout architecture presented in this work is designed to be scalable to large area module detectors with a goal to create the first TOF-PET system with 100 ps FWHM CTR.

    View details for DOI 10.1088/1361-6560/abf1bc

    View details for PubMedID 33761476

  • Novel method to measure the intrinsic spatial resolution in PET detectors based on monolithic crystals NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Gonzalez-Montoro, A., Sanchez, F., Bruyndonckx, P., Canizares, G., Benlloch, J. M., Gonzalez, A. J. 2019; 920: 58–67
  • TOF studies for dedicated PET with open geometries Moliner, L., Ilisie, V., Gonzalez, A., Oliver, S., Gonzalez, A., Gimenez-Alventosa, V., Canizares, G., Lamprou, E., Alamo, J., Sanchez, F., Rodriguez, M. J., Benlloch, J. M. IOP PUBLISHING LTD. 2019
  • PET detector block with accurate 4D capabilities Lamprou, E., Aguilar, A., Gonzalez-Montoro, A., Monzo, J. M., Canizares, G., Iranzo, S., Vidal, L. F., Hernandez, L., Conde, P., Sanchez, S., Sanchez, F., Gonzalez, A. J., Benlloch, J. M. ELSEVIER SCIENCE BV. 2018: 132–36
  • Feasibility Study of a Small Animal PET Insert Based on a Single LYSO Monolithic Tube FRONTIERS IN MEDICINE Gonzalez, A. J., Berr, S. S., Canizares, G., Gonzalez-Montoro, A., Orero, A., Correcher, C., Rezaei, A., Nuyts, J., Sanchez, F., Majewski, S., Benlloch, J. M. 2018; 5: 328


    There are drawbacks with using a Positron Emission Tomography (PET) scanner design employing the traditional arrangement of multiple detectors in an array format. Typically PET systems are constructed with many regular gaps between the detector modules in a ring or box configuration, with additional axial gaps between the rings. Although this has been significantly reduced with the use of the compact high granularity SiPM photodetector technology, such a scanner design leads to a decrease in the number of annihilation photons that are detected causing lower scanner sensitivity. Moreover, the ability to precisely determine the line of response (LOR) along which the positron annihilated is diminished closer to the detector edges because the spatial resolution there is degraded due to edge effects. This happens for both monolithic based designs, caused by the truncation of the scintillation light distribution, but also for detector blocks that use crystal arrays with a number of elements that are larger than the number of photosensors and, therefore, make use of the light sharing principle. In this report we present a design for a small-animal PET scanner based on a single monolithic annulus-like scintillator that can be used as a PET insert in high-field Magnetic Resonance systems. We provide real data showing the performance improvement when edge-less modules are used. We also describe the specific proposed design for a rodent scanner that employs facetted outside faces in a single LYSO tube. In a further step, in order to support and prove the proposed edgeless geometry, simulations of that scanner have been performed and lately reconstructed showing the advantages of the design.

    View details for DOI 10.3389/fmed.2018.00328

    View details for Web of Science ID 000451693300002

    View details for PubMedID 30547030

    View details for PubMedCentralID PMC6279866

  • A scintillator geometry suitable for very small PET gantries Gonzalez, A. J., Gonzalez-Montoro, A., Aguilar, A., Canizares, G., Marti, R., Iranzo, S., Lamprou, E., Sanchez, S., Sanchez, F., Benlloch, J. M. IOP PUBLISHING LTD. 2017
  • Performance Study of a Large Monolithic LYSO PET Detector With Accurate Photon DOI Using Retroreflector Layers IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES Gonzalez-Montoro, A., Aguilar, A., Canizares, G., Conde, P., Hernandez, L., Vidal, L. F., Galasso, M., Fabbri, A., Sanchez, F., Benlloch, J. M., Gonzalez, A. J. 2017; 1 (3): 229–37
  • PETIROC2 based readout electronics optimization for Gamma Cameras and PET detectors JOURNAL OF INSTRUMENTATION Monzo, J. M., Aguilar, A., Gonzalez-Montoro, A., Lamprou, E., Gonzalez, A. J., Hernandez, L., Mazur, D., Colom, R. J., Benlloch, J. M. 2017; 12
  • Performance study of a PET scanner based on monolithic scintillators for different DoI-dependent methods JOURNAL OF INSTRUMENTATION Preziosi, E., Sanchez, S., Gonzalez, A. J., Pani, R., Borrazzo, C., Bettiol, M., Rodriguez-Alvarez, M. J., Gonzalez-Montoro, A., Moliner, L., Benlloch, J. M. 2016; 11
  • Pilot tests of a PET detector using the TOF-PET ASIC based on monolithic crystals and SiPMs JOURNAL OF INSTRUMENTATION Aguilar, A., Gonzalez-Montoro, A., Gonzalez, A. J., Hernandez, L., Monzo, J. M., Bugalho, R., Ferramacho, L., Benlloch, J. M. 2016; 11
  • Analysis of the Statistical Moments of the Scintillation Light Distribution With dSiPMs IEEE TRANSACTIONS ON NUCLEAR SCIENCE Conde, P., Gonzalez, A. J., Gonzalez, A., Hernandez, L., Bellido, P., Crespo, E., Iborra, A., Moliner, L., Rigla, J. P., Rodriguez-Alvarez, M. J., Sanchez, F., Seimetz, M., Soriano, A., Vidal, L. F., Benlloch, J. M. 2015; 62 (5): 1981–88