Bio


Shirin Pourashraf was born in Darreh Shahr, Ilam, Iran.
She started her graduate studies with research interests expanded to microelectronics, and very large scale integrated (VLSI). She worked with Professor Masoud Sayedi at Isfahan University of Technology (IUT), Iran, and Professor Jaime Ramirez-Angulo at New Mexico State University, USA, respectively for her Masters, and Ph.D., focusing on integrated Circuit (IC) design. She designed, fabricated, experimentally tested, and validated the performance of several innovative digital, analog, and mixed-signal building block ICs mainly in 180 nm CMOS Technology. After her Ph.D., she joined Molecular Imaging and Instrumentations Laboratory (MIIL) at Stanford, to work under the supervision of Professor Craig Levin, an expert in positron emission tomography (PET).
In MIIL, Shirin Pourashraf has been leading a challenging Medical Imaging hardware project to build a 16-module partial-ring Time of Flight (TOF)-PET Scanner with 100 ps coincidence time resolution (CTR), specifically by designing compact high-speed and low-noise/jitter custom electronic readouts. The system is currently scaling up, that upon completion, ~100 ps CTR results in >5-fold signal-to-noise-ratio (SNR) improvement in PET scanner, increasing its ability to detect and quantify metastatic malignant lesions (cancer/tumor) or alternatively, can substantially reduce scanning times or injected activity of/to the patience.

Honors & Awards


  • 2024 IEEE NSS/MIC/RTSD Trainee Grant, Tampa, Florida, USA, 2024 IEEE Nuclear Science, Medical Imaging and Room Temperature Semiconductor Detector Conference (2024 July)
  • 2023 IEEE NSS/MIC/RTSD Trainee Grant, Vancouver, Canada, IEEE Nuclear Science Symposium & Medical Imaging Conference (2023 July)
  • 2023 Stanford Bio-X Travel Award, Bio-X at Stanford University (2023 August)
  • 2022 Valentin T. Jordanov Radiation Instrumentation Travel Grant, 2022 IEEE Nuclear Science, Medical Imaging and Room Temperature Semiconductor Detector Conference (2022 September)
  • 2022 IEEE NSS/MIC/RTSD Trainee Grant, Milano, Italy, IEEE 29th Nuclear Science Symposium & Medical Imaging Conference (2022 July)
  • Stanford Cancer Imaging Training (SCIT ) Fellowship; NIH T32 Award, NIH (National Institute of Health): National Cancer Institute (2022 Feb. to 2024 Feb.)
  • 2022 Stanford Bio-X Travel Award, Bio-X at Stanford University (2022 Agust)
  • 2021 IEEE NSS/MIC/RTSD Trainee Grant, Japan, IEEE 28th Nuclear Science Symposium & Medical Imaging Conference (2021)
  • 2020 IEEE NSS/MIC/RTSD Trainee Grant, Boston, Massachusetts, United States., IEEE 27th Nuclear Science Symposium & Medical Imaging Conference (2020)
  • Research grant; 1R01EB02512501, NIH (National Institution of Health) (2019-2024)
  • Research grant; 5R01CA21466903, NIH (National Institution of Health) (2019-2024)
  • 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)
  • 2018 Outstanding Graduate Assistantship Award, Graduate School, New Mexico State University (2018)
  • 2017 Outstanding Teaching Assistant Award, Klipsch School of Electrical and Computer Engineering Department, New Mexico State University (2017)
  • 2002 Talented Students Association Award, Shahid Chamran University of Ahvaz (2002)

Professional Education


  • Ph.D., New Mexico State University, NM, USA, Electrical Engineering/Mixed-Signal Integrated Circuit (IC) Design (2018)
  • Master of Science, Isfahan University Of Technology (IUT), Electrical Engineering/Microelectronics (2011)
  • Bachelor of Science, Shahid Chamran University of Ahvaz, Electrical Engineering (2007)

Stanford Advisors


Patents


  • Shirin Pourashraf, Joshua W. Cates, and Craig S. Levin. "United States Patent PCT/US23/79151 Electronic Timing Channel Readout with Multiplexing Capabilities Cross-Reference to Related Applications", Stanford University

Current Research and Scholarly Interests


I am mainly working on designing high-speed and low-noise/jitter instrumentation, and data acquisition electronics for building a partial ring TOF-PET system to achieve ~100 ps CTR and 50 cm FOV. This means a > 2-fold signal-to-noise-ratio (SNR) improvement relative to the best commercially-available PET scanner; ∼214-250 ps CTR Siemens Biograph.
This highly compact TOF-PET system will be integrated to a CT scanner for acquiring both functional and structural information in clinical imaging.

All Publications


  • A Scalable Dynamic TOT Circuit for a 100 ps TOF-PET Detector Design to Improve Energy Linearity and Dynamic Range IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES Pourashraf, S., Cates, J. W., Levin, C. S. 2024; 8 (3): 237-247
  • Highly Compact and Scalable 100 ps CTR 3D Positioning TOF-PET Detector Sub-Unit 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD) Pourashraf, S., Innes, D., Cates, J., Levin, C. 2023
  • Cherenkov Radiation-Based Coincidence Time Resolution Measurements in BGO Scintillators FRONTIERS IN PHYSICS Gonzalez-Montoro, A., Pourashraf, S., Cates, J. W., Levin, C. S. 2022; 10
  • Investigation of Electronic Signal Processing Chains for a Prototype TOF-PET System with 100 ps Coincidence Time Resolution IEEE Transactions on Radiation and Plasma Medical Sciences Pourashraf, S., Gonzalez-Montoro, A., Lee, M., Cates, J. W., Won, J. Y., Lee, J. S., Levin, C. S. 2022; 6 (6): 690 - 696
  • 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
  • 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

  • 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