Honors & Awards

  • Outstanding Achievement in Graduate Studies Award, University of Waterloo (2014)
  • Doctoral Thesis Completion Award, University of Waterloo (2013)
  • SPIE Optics and Photonics Education Scholarship, SPIE (2013)
  • Faculty of Engineering Graduate Scholarship, University of Waterloo (2012)
  • Ontario Graduate Scholarship (OGS), Government of Ontario (2012)
  • President?s Graduate Scholarship, University of Waterloo (2012)
  • Savvas Chamberlain Graduate Scholarship, University of Waterloo (2012)
  • Waterloo Institute for Nanotechnology (WIN) Nano-fellowship, WIN (2012)
  • University of Waterloo Graduate Student Scholarship, University of Waterloo (2010-2011)
  • Provost Doctoral Entrance Award for Women, University of Waterloo (2009)

Professional Education

  • Bachelor of Science, Unlisted School (2003)
  • Doctor of Philosophy, University of Waterloo (2014)
  • Master of Science, KNToosiUniversityofTechnology (2006)

Stanford Advisors


All Publications

  • Characterization of Optically Sensitive Amorphous Selenium Photodetector at High Electric Fields IEEE TRANSACTIONS ON ELECTRON DEVICES Ghaffari, S., Abbaszadeh, S., Ghanbarzadeh, S., Karim, K. S. 2015; 62 (7): 2364-2366
  • Enhanced Dark Current Suppression of Amorphous Selenium Detector With Use of IGZO Hole Blocking Layer IEEE TRANSACTIONS ON ELECTRON DEVICES Abbaszadeh, S., Tari, A., Wong, W. S., Karim, K. S. 2014; 61 (9): 3355-3357
  • Low Dark Current Amorphous Silicon Metal-Semiconductor-Metal Photodetector for Digital Imaging Applications IEEE ELECTRON DEVICE LETTERS Ghanbarzadeh, S., Abbaszadeh, S., Karim, K. S. 2014; 35 (2): 235-237
  • Raman and AFM mapping studies of photo-induced crystallization in a-Se films: substrate strain and thermal effects Canadian Journal of Physics Lindberg, G. P., O'Loughlin, T., Gross, N., Reznik, A., Abbaszadeh, S., Karim, K. S., Belev, G., Hunter, D. M., Weinstein, B. A. 2014

    View details for DOI 10.1139/cjp-2013-0586

  • Enhanced Detection Efficiency of Direct Conversion X-ray Detector Using Polyimide as Hole-Blocking Layer SCIENTIFIC REPORTS Abbaszadeh, S., Scott, C. C., Bubon, O., Reznik, A., Karim, K. S. 2013; 3


    In this article we demonstrate the performance of a direct conversion amorphous selenium (a-Se) X-ray detector using biphenyldisnhydride/1,4 phenylenediamine (BPDA/PPD) polyimide (PI) as a hole-blocking layer. The use of a PI layer with a-Se allows detector operation at high electric fields (?10 V/?m) while maintaining low dark current, without deterioration of transient performance. The hole mobility of the PI/a-Se device is measured by the time-of-flight method at different electric fields to investigate the effect of the PI layer on detector performance. It was found that hole mobility as high as 0.75 cm(2)/Vs is achievable by increasing the electric field in the PI/a-Se device structure. Avalanche multiplication is also shown to be achievable when using PI as a blocking layer. Increasing the electric field within a-Se reduces the X-ray ionization energy, increases hole mobility, and improves the dynamic range and sensitivity of the detector.

    View details for DOI 10.1038/srep03360

    View details for Web of Science ID 000327535200005

    View details for PubMedID 24285255

  • Characterization of Low Dark-Current Lateral Amorphous-Selenium Metal-Semiconductor-Metal Photodetectors IEEE SENSORS JOURNAL Abbaszadeh, S., Allec, N., Karim, K. S. 2013; 13 (5): 1452-1458
  • Evaluating noise reduction techniques while considering anatomical noise in dual-energy contrast-enhanced mammography MEDICAL PHYSICS Allec, N., Abbaszadeh, S., Scott, C. C., Karim, K. S., Lewin, J. M. 2013; 40 (5)


    The authors describe modifications to previously developed cascaded systems analysis to include the anatomical noise in evaluation of dual-energy noise reduction techniques. Previous models have ignored the anatomical noise in theoretical analysis of noise reduction techniques. The inclusion of anatomical noise leads to more accurate estimation of potential noise reduction improvements and optimization.The model is applied to dual-energy contrast-enhanced mammography. The effect of linear noise reduction filters on the anatomical noise is taken into account using cascaded systems analysis. The noise model is included in the ideal observer detectability for performance evaluation of the noise reduction techniques.Dual-energy image noise with and without including the effect of anatomical noise in noise reduction technique analysis is reported. The theoretical model is compared with clinical images from a previous dual-energy contrast enhanced mammography clinical study and good agreement is observed. The results suggest that the inclusion of anatomical noise in the evaluation and comparison of noise reduction techniques is highly warranted for more accurate analysis.This work establishes a useful extension to dual-energy cascaded systems analysis for maximizing image quality using noise reduction techniques. The extension includes the effect of linear image filtering, such as that used for noise reduction, on anatomical noise. The results suggest that the inclusion of anatomical noise in the evaluation of noise reduction techniques can lead to more accurate optimization, noise, and performance estimations.

    View details for DOI 10.1118/1.4799841

    View details for Web of Science ID 000318553900029

    View details for PubMedID 23635274

  • Measurement of UV from a Microplasma by a Microfabricated Amorphous Selenium Detector IEEE TRANSACTIONS ON ELECTRON DEVICES Abbaszadeh, S., Karim, K. S., Karanassios, V. 2013; 60 (2): 880-883
  • Including the effect of motion artifacts in noise and performance analysis of dual-energy contrast-enhanced mammography PHYSICS IN MEDICINE AND BIOLOGY Allec, N., Abbaszadeh, S., Scott, C. C., Lewin, J. M., Karim, K. S. 2012; 57 (24)


    In contrast-enhanced mammography (CEM), the dual-energy dual-exposure technique, which can leverage existing conventional mammography infrastructure, relies on acquiring the low- and high-energy images using two separate exposures. The finite time between image acquisition leads to motion artifacts in the combined image. Motion artifacts can lead to greater anatomical noise in the combined image due to increased mismatch of the background tissue in the images to be combined, however the impact has not yet been quantified. In this study we investigate a method to include motion artifacts in the dual-energy noise and performance analysis. The motion artifacts are included via an extended cascaded systems model. To validate the model, noise power spectra of a previous dual-energy clinical study are compared to that of the model. The ideal observer detectability is used to quantify the effect of motion artifacts on tumor detectability. It was found that the detectability can be significantly degraded when motion is present (e.g., detectability of 2.5 mm radius tumor decreased by approximately a factor of 2 for translation motion on the order of 1000 ?m). The method presented may be used for a more comprehensive theoretical noise and performance analysis and fairer theoretical performance comparison between dual-exposure techniques, where motion artifacts are present, and single-exposure techniques, where low- and high-energy images are acquired simultaneously and motion artifacts are absent.

    View details for DOI 10.1088/0031-9155/57/24/8405

    View details for Web of Science ID 000312106200019

    View details for PubMedID 23202244

  • K-Edge Imaging Using Dual-Layer and Single-Layer Large Area Flat Panel Imagers IEEE TRANSACTIONS ON NUCLEAR SCIENCE Allec, N., Abbaszadeh, S., Fleck, A., Tousignant, O., Karim, K. S. 2012; 59 (5): 1856-1861
  • Investigation of Hole-Blocking Contacts for High-Conversion-Gain Amorphous Selenium Detectors for X-Ray Imaging IEEE TRANSACTIONS ON ELECTRON DEVICES Abbaszadeh, S., Allec, N., Ghanbarzadeh, S., Shafique, U., Karim, K. S. 2012; 59 (9): 2403-2409
  • The effect of the substrate on transient photodarkening in stabilized amorphous selenium JOURNAL OF NON-CRYSTALLINE SOLIDS Abbaszadeh, S., Rom, K., Bubon, O., Weinstein, B. A., Karim, K. S., Rowlands, J. A., Reznik, A. 2012; 358 (17): 2389-2392
  • Single-layer and dual-layer contrast-enhanced mammography using amorphous selenium flat panel detectors PHYSICS IN MEDICINE AND BIOLOGY Allec, N., Abbaszadeh, S., Karim, K. S. 2011; 56 (18): 5903-5923


    The accumulation of injected contrast agents allows the image enhancement of lesions through the use of contrast-enhanced mammography. In this technique, the combination of two acquired images is used to create an enhanced image. There exist several methods to acquire the images to be combined, which include dual energy subtraction using a single detection layer that suffers from motion artifacts due to patient motion between image acquisition. To mitigate motion artifacts, a detector composed of two layers may be used to simultaneously acquire the low and high energy images. In this work, we evaluate both of these methods using amorphous selenium as the detection material to find the system parameters (tube voltage, filtration, photoconductor thickness and relative intensity ratio) leading to the optimal performance. We then compare the performance of the two detectors under the variation of contrast agent concentration, tumor size and dose. The detectability was found to be most comparable at the lower end of the evaluated factors. The single-layer detector not only led to better contrast, due to its greater spectral separation capabilities, but also had lower quantum noise. The single-layer detector was found to have a greater detectability by a factor of 2.4 for a 2.5 mm radius tumor having a contrast agent concentration of 1.5 mg ml(-1) in a 4.5 cm thick 50% glandular breast. The inclusion of motion artifacts in the comparison is part of ongoing research efforts.

    View details for DOI 10.1088/0031-9155/56/18/009

    View details for Web of Science ID 000294787300011

    View details for PubMedID 21852727

  • Low Dark-Current Lateral Amorphous-Selenium Metal-Semiconductor-Metal Photodetector IEEE ELECTRON DEVICE LETTERS Abbaszadeh, S., Allec, N., Wang, K., Karim, K. S. 2011; 32 (9): 1263-1265
  • Gas Sensitive Porous Silver-Rutile High-Temperature Schottky Diode on Thermally Oxidized Titanium IEEE SENSORS JOURNAL Hossein-Babaei, F., Abbaszadeh, S., Esfahani, M. S. 2009; 9 (3): 237-243

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