Research - Flat Panel Imaging Group

Facilities: Our research is primarily conducted in a pleasant, off-campus environment where the state-of-the-art facilities include multiple measurement and engineering labs equipped with dedicated x-ray sources and sophisticated hardware and software tools.

Disciplinary Reach of Research: The research involves electrical and mechanical engineering as well as radiation, imaging and device physics. The research also encompasses experimental design, computer simulation, and empirical prototype evaluation.

Resource Sharing: In compliance with NIH policy on resource sharing, Final Research Data can be obtained for those publications supported by NIH funding, and for which such Data exist, by contacting the principle investigator, Dr. Larry Antonuk.

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An Advanced Technology Flat-Panel Imager for Fluoroscopy

PSI3 Pixel
Schematic 3D-rendering of four prototype pixels.
(Click to change viewpoint)

Purpose: Our goal is the development of a new generation of large area, solid-state, digital x-ray imagers whose performance attains the theoretical limits imposed by the fundamental signal and noise characteristics of the incident radiation. The imagers are based on array substrates comprising millions of pixels incorporating pixel-level amplification circuits based on thin-film, poly-crystalline silicon transistors.

Background: Following extensive research by our group and others, flat-panel imagers have become ubiquitous for projection and tomographic medical imaging. Their uses range from the treatment of cancer using high-energy radiation beams to diagnosis of disease and interventional procedures. However, today's flat-panel technology suffers from significant limitations that improvement to the signal-to-noise properties would overcome.

Impact: The improved performance expected from the technology we are developing is expected to result in improved image quality at significantly lower radiation dose to the patient. This, along with other capabilities such as extremely high frame rates, will allow the technology to facilitate advanced applications such as very low dose fluoroscopy, breast and chest tomosynthesis, dual-energy imaging and cone-beam computer-tomography for breast, angiographic and other procedures.

Approach: In partnership with industrial collaborators, we design, fabricate and evaluate sophisticated prototype imagers in which the pixel circuits incorporate out-of-plane and three-dimensional circuit architectures comprising in-pixel amplification structures. A recent working prototype, which represents an order-of-magnitude increase in complexity compared to contemporary designs, is shown in the nearby illustration.

Project Funding: This research is support by the National Institutes of Health / National Institute of Biomedical Imaging and Bioengineering (R01-EB000558) as well as by our department.

Recent Publications:
  1. El-Mohri et al., Med. Phys. 36(7), 3340-3355, 2009
  2. Antonuk et al., Med. Phys. 36(7), 3322-3339, 2009
  3. Antonuk et al., SPIE Medical Imaging, 725814, 2009
  4. Antonuk et al., Mater. Res. Soc. Symp. Proc. 1066, 1066-A19-03, 2008.
  5. Du et al., Phys. Med. Biol. 53(5), 1325-1351, 2008. PMCID: PMC2706137
  6. Antonuk et al., SPIE Medical Imaging, 69130I, 2008
  7. El-Mohri et al., Med. Phys. 34(1), 315-327, 2007.
  8. Li et al., J. Appl. Phys. 99, 064501-1 to 064501-7, 2006.
  9. Su et al., Phys. Med. Biol. 50(12), 2907-2928, 2005.
  10. Kang et al., IEEE Trans. Nuc. Sc. 52(1), 38-45, 2005.
  11. Antonuk et al., SPIE Vol. 5745, Physics of Medical Imaging, 2005: 18-31.
  12. Antonuk et al., SPIE Vol. 5368, Physics of Medical Imaging, 2004: 127-138.
  13. Kang et al., Conference record contribution to 2003 IEEE-MIC held in Portland Oregon, October 20-24, 2003
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A High Quantum Efficiency Flat-Panel Radiotherapy Imager

MV CBCT Setup
MV CBCT Setup
(Click to replay animation)

Purpose: The aim of the research is to develop new forms of x-ray detectors for the megavoltage flat-panel imagers that are used for radiation therapy in cancer treatment. The ultimate goal is to facilitate visualization of soft tissues in tomographic images acquired at low, clinically practical doses. Toward these ends, detectors based on segmented crystalline scintillators or polycrystalline photoconductive materials are being developed for use with large area, flat-panel imagers based on array substrates comprising ~105 pixels.

Background: Following pioneering research conducted by our group, flat-panel imagers have become the gold standard for creating projection images of the patient using the high-energy, x-ray treatment beams employed in radiotherapy. However, the low x-ray detection efficiencies (~1%) of present megavoltage imagers strongly limit the clinical utility and potential of such devices.

Impact: The significant improvements in detection efficiency sought in our research will make it possible to achieve soft-tissue contrast, even at the lowest doses delivered by the treatment machines. Moreover, such improvements will also make the acquisition of tomographic imaging information (requiring ~102 projection images) at the same dose presently required for a single projection image. Such improvement in capability is expected to significantly assist in the fundamental medical objective of maximizing the dose to the tumor while minimizing dose to surrounding, normal tissue.

Approach: In partnership with industrial collaborators, we design, fabricate and evaluate sophisticated prototype imagers comprising x-ray detectors with efficiencies ranging from ~7% to 50%. These prototypes are subject to extensive performance evaluation, including computed tomography demonstrations using set-ups such as that depicted in the nearby illustration.

Project Funding: This research is support by the National Institutes of Health / National Cancer Institute (R01-CA51397) as well as by our department.

Recent Publications:
  1. El-Mohri et al., Phys. Med. Biol. 56, 1509-1527, 2011. PMCID: PMC3062516
  2. Wang et al., Phys. Med. Biol. 55, 3659-3673, 2010. PMCID: PMC2909124
  3. Zhao et al., Med. Phys. 37(6), 2738-2748, 2010. PMCID: PMC2885944
  4. Wang et al., Med. Phys. 36(12), 5707-5718, 2009. PMCID: PMC2797046
  5. Wang et al., Med. Phys. 36(7), 3227-3238, 2009. PMCID: PMC2805354
  6. Wang et al., Med. Phys. 35(1), 145-158, 2008. PMCID: PMC2920060
  7. Daniel et al., Sensors and Actuators A140, 185-193, 2007. PMCID: PMC2151745
  8. Sawant et al., Med. Phys. 34(5), 1535-1545, 2007.
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