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Muhammad Nasir Ullah has received a BS degree in Electronic Engineering from International Islamic University, Islamabad (IIUI) Pakistan in Jun 2012 and an integrated MS + Ph.D. degree in Bio-Convergence Engineering from Korea University, Seoul, South Korea under the supervision of Professor Jung-Yeol Yeom in Feb 2020. His Ph.D. thesis was focused on detector design for Nuclear Medicine (NM) system and NM-Ultrasound hybrid systems.
His area of research interest is radiation detection and measurement for medical applications. He has been working on detector design for Positron Emission Tomography (PET) system, intraoperative gamma probe detector, beta/gamma discrimination, and hybrid Ultrasound-gamma probe. He has also been working on frontend discrete circuit designs for various types of radiation and Ultrasound (US) detectors. He has published 6 peer-reviewed articles as the first author while 2 as co-author. He also has 4-patents under his name in S. Korea.

Honors & Awards

  • Ph.D. Scholarship, Korea University, Seoul, South Korea (2015-2020)
  • Final Year Project Award, International Islamic University, Islamabad, Pakistan (2012)
  • Best Paper Award, Korea University, Seoul, South Korea (2019)
  • Trainee Grant, IEEE NSS/MIC (2016)
  • Trainee Grant, IEEE NSS/MIC (2020)

Professional Education

  • Doctor of Philosophy, Korea University (2020)
  • Bachelor of Science, Unlisted School (2012)
  • Integrated MS + PhD, Korea University, Seoul, South Korea, Bio-Convergence Engineering (2020)
  • BSEE, International Islamic University, Islamabad, Pakistan, Electronic Engineering (2012)

Stanford Advisors

Research & Scholarship


All Publications

  • Wavelength discrimination (WLD) detector optimization for time-of-flight positron emission tomography with depth of interaction information NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Ullah, M., Park, J., Pratiwi, E., Kim, G., Yeom, J. 2020; 982
  • Wavelength discrimination (WLD) TOF-PET detector with DOI information PHYSICS IN MEDICINE AND BIOLOGY Ullah, M., Pratiwi, E., Park, J., Lee, K., Choi, H., Yeom, J. 2020; 65 (5): 055003


    Depth-of-interaction (DOI) encoding can contribute to improving spatial resolution uniformity and sensitivity in positron-emission-tomography (PET) scanners. In addition, time-of-flight (TOF) PET scanners with DOI encoding have received considerable interest because of their potential for improving the spatial resolution, sensitivity, and image quality of the overall system. In this study, a new DOI detector configuration utilizing scintillators' emission wavelength is proposed, and experimental results on the energy, timing, and DOI performance of the detector are provided. The DOI information from the proposed phoswich-type detector can be acquired at the detector level without complex signal processing by utilizing a single optical filter with customized optical properties. For this, we used either a short pass filter (SPF) or a long pass filter (LPF) that allows light photons of a specific wavelength to pass. The two-layered phoswich detector was configured with two scintillators with different photon-emission spectra. In this study, we used Ce:GAGG (3?mm????3?mm????10?mm) and LYSO:Ce (3?mm????3?mm????10?mm) as the top and bottom layer scintillators, respectively. A digital silicon photomultiplier (dSiPM) was used as the photosensor and for data acquisition. The phoswich detector was placed in the center of two dSiPM pixels, where one of the dSiPM pixels was covered with the optical filter, and the light guide was placed on the other pixel. The detector was tested for energy, timing, and DOI encoding performance. When an SPF was used, the energy resolutions of 16.2% and 11.8% were achieved for the Ce:GAGG (top layer) and LYSO:Ce (bottom layer) respectively without correcting for saturation effect. With a small (3?mm????3?mm????5?mm) LYSO crystal as the reference detector, CRTs (coincidence-resolving times) of 338?ps and 244?ps were recorded for the top and bottom layers respectively. The detector configuration also provides an excellent DOI-separation figure-of-merit (FoM) value of 1.9. In the case of LPF, the energy resolutions of 12.0% and 12.9% were achieved for the Ce:GAGG (top layer) and LYSO:Ce (bottom layer), respectively. CRTs (coincidence resolving times) of 314?ps and 263?ps were recorded for the top and bottom layers, respectively. The DOI-separation FoM value of 1.5 was achieved in this setup. Results show that the proposed method can provide excellent discrete DOI positioning accuracy without compromising the timing performance of the detector.

    View details for DOI 10.1088/1361-6560/ab6579

    View details for Web of Science ID 000519034300001

    View details for PubMedID 31874462

  • Collimators for Gamma Dual Energy CT Arch-Detector: A Simulation Study JOURNAL OF THE KOREAN PHYSICAL SOCIETY Pratiwi, E., Bae, S., Lee, H., Ullah, M., Lee, B., Lee, K., Yeom, J. 2020; 76 (1): 79?85

    View details for DOI 10.3938/jkps.76.79

    View details for Web of Science ID 000511872400013

  • A new positron-gamma discriminating phoswich detector based on wavelength discrimination (WLD) NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Ullah, M., Park, C., Pratiwi, E., Kim, C., Choi, H., Yeom, J. 2019; 946
  • Investigation of Optical Properties of Ceramic Ce:GAGG by High Temperature Annealing JOURNAL OF THE KOREAN PHYSICAL SOCIETY Park, C., Ullah, M., Kim, C., Cho, S., Yeom, J. 2019; 75 (12): 962?67
  • Studies on sub-millimeter LYSO:Ce, Ce:GAGG, and a new Ce:GFAG block detector for PET using digital silicon photomultiplier NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT Ullah, M., Pratiwi, E., Park, J., Yamamoto, S., Kamada, K., Yoshikawa, A., Yeom, J. 2018; 911: 115?22
  • Instrumentation for Time-of-Flight Positron Emission Tomography NUCLEAR MEDICINE AND MOLECULAR IMAGING Ullah, M., Pratiwi, E., Cheon, J., Choi, H., Yeom, J. 2016; 50 (2): 112?22


    Positron emission tomography (PET) is a molecular imaging modality that provides information at the molecular level. This system is composed of radiation detectors to detect incoming coincident annihilation gamma photons emitted from the radiopharmaceutical injected into a patient's body and uses these data to reconstruct images. A major trend in PET instrumentation is the development of time-of-flight positron emission tomography (ToF-PET). In ToF-PET, the time information (the instant the radiation is detected) is incorporated for image reconstruction. Therefore, precise and accurate timing recording is crucial in ToF-PET. ToF-PET leads to better localization of the annihilation event and thus results in overall improvement in the signal-to-noise ratio (SNR) of the reconstructed image. Several factors affect the timing performance of ToF-PET. In this article, the background, early research and recent advances in ToF-PET instrumentation are presented. Emphasis is placed on the various types of scintillators, photodetectors and electronic circuitry for use in ToF-PET, and their impact on timing resolution is discussed.

    View details for DOI 10.1007/s13139-016-0401-5

    View details for Web of Science ID 000386256200004

    View details for PubMedID 27275359

    View details for PubMedCentralID PMC4870467

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