Bio


Shirin Pourashraf is from Darreh Shahr, Ilam, Iran. She received the M.S. degree from the Department of Electrical and Computer Engineering, Isfahan University of Technology, Isfahan, Iran, in 2011, and the Ph.D. degree from New Mexico State University, Las Cruces, NM, USA, in 2018.
Her field of studies was the design and test of low-voltage/low-power and high performance analog/digital/mixed-signal building blocks.
She authored several journal papers during her Ph.D., and was the recipient of the Outstanding Teaching Assistant Award from the Klipsch School of Electrical and Computer Engineering, New Mexico State University, in 2017 and the Outstanding Graduate Assistantship Award from the Graduate School of New Mexico State University in 2018.
Dr. Pourashraf is currently a Postdoctoral Fellow Scholar in the Department of Radiology, Molecular Imaging Instrumentation Laboratory (MIIL) working on TOF-PET Imaging; specifically exploring, and designing instrumentation, and data acquisition electronics to improve time-of-flight resolution in PET detectors.

Honors & Awards


  • 2021 IEEE NSS/MIC/RTSD Trainee Grant, Japan, IEEE Nuclear Science Symposium & Medical Imaging Conference (2021)
  • 2020 IEEE NSS/MIC/RTSD Trainee Grant, Boston, Massachusetts, United States., IEEE Nuclear Science Symposium & Medical Imaging Conference (2020)
  • Research grant; 1R01EB02512501, NIH (National Institution of Health) (2019-present)
  • Research grant; 5R01CA21466903, NIH (National Institution of Health) (2019-present)
  • 2019 IEEE NSS/MIC/RTSD Trainee Grant, Manchester, United Kingdom., IEEE Nuclear Science Symposium & Medical Imaging Conference (2019)
  • Granted Xilinx Kintex-7 KC705 FPGA Evaluation Kit and associated licenses., Xilinx University Donation Program (2019)
  • Outstanding Graduate Assistantship Award, Graduate School, New Mexico State University (2018)
  • Outstanding Teaching Assistant Award, Klipsch School of Electrical and Computer Engineering Department, New Mexico State University (2017)
  • Talented Students Association Award, Shahid Chamran University of Ahvaz (2002)

Professional Education


  • P.hD., New Mexico State Univ. NM, USA, Electrical Engineering, IC Design (2018)
  • Master of Science in Engr, Isfahan University Of Technology (2011)
  • Bachelor of Elec Engineering, Shahid Chamran University (2007)

Stanford Advisors


Current Research and Scholarly Interests


I am working on TOF-PET Imaging; specifically exploring, and designing instrumentation, and data acquisition electronics to improve time-of-flight resolution in PET detectors.

All Publications


  • 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

    Abstract

    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

  • 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

    Abstract

    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

  • 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
  • Studies of a Scalable Electronic Readout Design for a 100 ps Coincidence Time Resolution TOF-PET System Pourashraf, S., Won, J. Y., Gonzalez-Montoro, A., Lee, M., Cates, J. W., Zhao, Z., Lee, J. S., Levin, C. S. IEEE Nuclear Science Symposium & Medical Imaging Conference (IEEE NSS-MIC), Boston, Massachusetts, United States. 2020
  • Study of Optical Reflectors Used in Scintillation Detectors that Achieve 100 ps Coincidence Time Resolution for TOF-PET Gonzalez-Montoro, A., Pourashraf, S., Lee, M., Cates, J. W., Levin, C. S. IEEE Nuclear Science Symposium & Medical Imaging Conference (IEEE NSS-MIC). 2020
  • Investigation of Analog and Digital Signal Processing Chains for a Prototype TOF-PET System with 100 ps Coincidence Time Resolution Pourashraf, S., Gonzalez-Montoro, A., Lee, M., Cates, J. W., Won, J. Y., Zhao, Z., Lee, J. S., Levin, C. S. IEEE Nuclear Science Symposium & Medical Imaging Conference (IEEE NSS-MIC). 2020
  • Gain and Bandwidth Enhanced Class-AB OTAs Pourashraf, S., Ramirez-Angulo, J., Roman-Loera, A., Gangineni, M., IEEE IEEE. 2019: 778–81
  • Pulse Shape Discrimination and Energy Measurement in Phoswich Detectors Using Gated-Integrator Circuit Pourashraf, S., Cates, J. W., Lee, M., Levin, C. S., IEEE IEEE. 2019
  • ±0.25 V Low-voltage Class-AB CMOS Capacitor Multiplier and Precision Rectifiers. IEEE Transaction on Very Large Scale Integrated Systems (TVLSI) Pourashraf, S., Ramirez-Angulo, J., Hinojo Montero, J., González-Carvajal, R., Lopez-Martin, A. J. 2018
  • Ultra Low Voltage Gate Driven Bandpass PGA with Constant Bandwidth Pourashraf, S., Ramirez-Angulo, J., Diaz-Sanchez, A., IEEE IEEE. 2018
  • Continuous and Discrete Time Low Voltage Analog Circuits in 16 nm CMOS Technology. Pourashraf, S., Ramirez-Angulo, J., Díaz-Armendariz , A. 2018 IEEE International Symposium on Circuits and Systems (ISCAS). 2018
  • An Amplified Offset Compensation Scheme and its Application in a Track and Hold Circuit. IEEE Transactions on Circuits and Systems II (TCAS-II) Pourashraf, S., Ramirez-Angulo, J., Cabrera-Galicia, A. R., Lopez-Martin, A. J., González-Carvajal, R. 2018; 65 (4): 416 - 420
  • An Op-amp Approach for Bandpass VGAs with Constant Bandwidth. IEEE Transactions on Circuits and Systems II (TCAS-II) Pourashraf, S., Ramirez-Angulo, J., Algueta-Miguel, J., Lopez-Martin, A. J., González-Carvajal, R. 2018; 65 (9): 1144 - 1148
  • A Highly Efficient Composite Class-AB-AB Miller Op-amp with High Gain and Stable from 15 pF up to Very Large Capacitive Loads. IEEE Transaction on Very Large Scale Integrated Systems (TVLSI) Pourashraf, S., Ramirez-Angulo, J., Lopez-Martin, A. J., González-Carvajal, R. 2018; 26 (10): 2061 - 2072
  • ±0.18 V Supply Gate Driven PGA with 0.7 Hz to 2 kHz Constant Bandwidth and 0.15 µW Power Dissipation. International Journal of Circuit Theory and Application (IJCTA) Pourashraf, S., Ramirez-Angulo, J., Lopez‐Martin, A. J., González-Carvajal, R., Díaz‐Sánchez, A. 2017; 46 (2): 272-279

    View details for DOI 10.1002/cta.2380

  • Offset compensation in a track and hold circuit. Pourashraf, S., Ramirez-Angulo, J., Cabrera-Galicia, A. R., Lopez-Martin, A. J., González-Carvajal, R. 2017 IEEE 60th International Midwest Symposium on Circuits and Systems (MWSCAS). 2017
  • A super class-AB OTA with high output current and no open loop gain degradation. Pourashraf, S., Ramirez-Angulo, J., Lopez-Martin, A. J., González-Carvajal, R. 2017 IEEE 60th International Midwest Symposium on Circuits and Systems (MWSCAS). 2017
  • Super Class-AB OTA without Open Loop Gain Degradation Based on Dynamic Cascode Biasing. International Journal of Circuit Theory and Application (IJCTA) Pourashraf, S., Ramirez-Angulo, J., Lopez-Martin, A. J., González-Carvajal, R. 2017; 45 (5): 2111-2118
  • High current efficiency class-AB OTA with high open loop gain and enhanced bandwidth. IEICE Letters, Electronics Express Pourashraf, S., Ramirez-Angulo, J., Roman-Loera, A., Lopez-Martin, A. J., Diaz-Sanchez, A., González-Carvajal, R. 2017; 14 (17): 20170719

    View details for DOI 10.1587/elex.14.20170719

  • Implementation of a Low Power 16-bit Radix-4 Pipelined SRT Divider Using a Modified Data Driven Dynamic Logic (D3L) Structure. Microelectronics Journal Pourashraf, S., Sayedi, S. 2013; 44 (12): 1165-1174
  • A low power D3L 16-bit radix- 4 pipelined SRT divider. Pourashraf, S., Sayedi, S. 2012 25th IEEE Canadian Conference on Electrical and Computer Engineering (CCECE). 2012
  • A novel 4∶2 compressor for high speed and low power applications. Pourashraf, S., Sayedi, M. 2010 18th IEEE Iranian Conference on Electrical Engineering. 2010