Dr. George Zentai Profile

Dr. George Zentai

Retired at Varian Medical Systems Inc

SPIE Involvement:

Author

Area of Expertise:

Digital x-ray imaging , Photoconductors , Amorphous semiconductors

Websites:

Company Website

Profile Summary

George Zentai joined Varian Medical Systems’ Ginzton Research Center (Mountain View, California) in 1998. He is a Senior Scientist and has been working as R&D Program Manager of Direct x-ray Sensor Development Projects. His team developed x-ray imagers both for medical and security applications, which went into production at Varian.
He gave many conference presentations; some of them invited ones, wrote several publications, and have many patents in the x-ray imaging field. He has also been involved in the development of low noise readout electronics, ASICs for flat panel digital imagers and special electronic testing methods. He has many years experience in photoconductor based imagers.
He has a Masters Degree in Electronics and a Ph.D. in Amorphous Semiconductors.
Previously he was Manager of Flat Panel X-ray Sensor Development at OIS (Optical Imaging Systems) and a visiting scientist at Argonne National Laboratory.
He is member of SPIE, senior member of IEEE and member of organizing and technical committees and co-chair of SPIE and IEEE conferences.

Publications (25)

Proceedings Article | 23 March 2015 Paper

Paper

Prototype 1.75 MV X-band linear accelerator testing for medical CT and industrial nondestructive testing applications

James Clayton, Daniel Shedlock, Steven Vanderet, George Zentai, Josh Star-Lack, Richard LaFave, Gary Virshup

Proceedings Volume 9438, 943813 (2015) https://doi.org/10.1117/12.2084394

KEYWORDS: Imaging systems, Prototyping, Nondestructive evaluation, X-rays, X-ray computed tomography, X band, Radiotherapy, Amorphous silicon, Metals, X-ray imaging

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Proceedings Article | 19 March 2014 Paper

Paper

Measurement of imaging properties of scintillating fiber optic plate

George Zentai, Arundhuti Ganguly, Josh Star-Lack, Gary Virshup, Hayley Hirsh, Daniel Shedlock, David Humber

Proceedings Volume 9033, 90333Q (2014) https://doi.org/10.1117/12.2043887

KEYWORDS: Modulation transfer functions, Imaging systems, X-rays, X-ray imaging, Fiber optics, Scintillators, Crystals, Fiber optics tests, Sensors, Copper

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Proceedings Article | 19 March 2014 Paper

Paper

MTF characterization in 2D and 3D for a high resolution, large field of view flat panel imager for cone beam CT

Jainil Shah, Steve Mann, Martin Tornai, Michelle Richmond, George Zentai

Proceedings Volume 9033, 90333V (2014) https://doi.org/10.1117/12.2043727

KEYWORDS: Modulation transfer functions, Sensors, Imaging systems, 3D metrology, 3D image processing, Image resolution, Tungsten, Breast, X-ray computed tomography, Spatial resolution

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Proceedings Article | 9 March 2014 Paper

Paper

Evaluation of different scintillators for 1MV NDE x-ray imaging

George Zentai, Arundhuti Ganguly, Gary Visrshup

Proceedings Volume 9064, 90640N (2014) https://doi.org/10.1117/12.2045998

KEYWORDS: X-rays, Imaging systems, Sensors, Modulation transfer functions, Fiber optics, Photons, Scintillators, Absorption, X-ray imaging, Copper

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Proceedings Article | 1 April 2011 Paper

Paper

X-ray imaging using K-edge filters

George Zentai

Proceedings Volume 7984, 798418 (2011) https://doi.org/10.1117/12.879188

KEYWORDS: X-rays, Iodine, X-ray imaging, Image filtering, Optical filters, Copper, Cerium, Aluminum, Europium, Absorption

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Proceedings Article | 19 March 2010 Paper

Paper

50 µm pixel size a-Se mammography imager with high DQE and increased temperature resistance

G. Zentai, L. Partain, M. Richmond, K. Ogusu, S. Yamada

Proceedings Volume 7622, 762215 (2010) https://doi.org/10.1117/12.845385

KEYWORDS: Imaging systems, Modulation transfer functions, Mammography, Molybdenum, X-rays, Aluminum, Temperature metrology, Image resolution, X-ray imaging, Breast

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Proceedings Article | 29 April 2008 Paper

Paper

High-energy (MeV) x-ray imaging with a mercuric iodide imager

G. Zentai, L. Partain

Proceedings Volume 6935, 69351Y (2008) https://doi.org/10.1117/12.776537

KEYWORDS: Imaging systems, Modulation transfer functions, X-rays, X-ray imaging, Photons, Absorption, Image resolution, Diagnostics, Copper, Spatial resolution

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Proceedings Article | 17 March 2007 Paper

Paper

Dark current and DQE improvements of mercuric iodide medical imagers

G. Zentai, L. Partain, R. Pavlyuchkova

Proceedings Volume 6510, 65100Q (2007) https://doi.org/10.1117/12.713848

KEYWORDS: Modulation transfer functions, Imaging systems, X-rays, X-ray imaging, Medical imaging, Photoresistors, Optical filters, Absorption, Electrodes, Photons

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Proceedings Article | 15 March 2006 Paper

Paper

Voltage injection and readout method for PCB (printed circuit board) testing

G. Zentai

Proceedings Volume 6177, 61770Z (2006) https://doi.org/10.1117/12.659064

KEYWORDS: Signal detection, Metals, Printed circuit board testing, Capacitive coupling, Foam, Detector arrays, Glasses, Capacitance, Electrodes, Sensors

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Proceedings Article | 26 October 2004 Paper

Paper

Dark current, sensitivity, and image lag comparison of mercuric iodide and lead iodide x-ray imagers

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Michael Schieber, Jerry Thomas

Proceedings Volume 5541, (2004) https://doi.org/10.1117/12.581223

KEYWORDS: Imaging systems, Crystals, X-ray imaging, Modulation transfer functions, Lead, X-rays, Sensors, Image resolution, Electrodes, Crystallography

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Proceedings Article | 6 May 2004 Paper

Paper

Mercuric iodide medical imagers for low-exposure radiography and fluoroscopy

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Barry Breen, A. Taieb, Ofer Dagan, Michael Schieber, Haim Gilboa, Jerry Thomas

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.535948

KEYWORDS: Imaging systems, Sensors, Electrodes, X-rays, X-ray detectors, Medical imaging, Radiography, Photoresistors, X-ray imaging, Modulation transfer functions

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Proceedings Article | 6 May 2004 Paper

Paper

Multiple-gain-ranging readout method to extend the dynamic range of amorphous silicon flat-panel imagers

Pieter Roos, Richard Colbeth, Ivan Mollov, Peter Munro, John Pavkovich, Edward Seppi, Edward Shapiro, Carlo Tognina, Gary Virshup, J. Micheal Yu, George Zentai, Wolfgang Kaissl, Evangelos Matsinos, Jeroen Richters, Heinrich Riem

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.535471

KEYWORDS: Imaging systems, Amplifiers, Capacitors, Calibration, Image processing, Signal processing, X-rays, Amorphous silicon, Gain switching, Image quality

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Proceedings Article | 6 May 2004 Paper

Paper

Improved properties of PbI2 x-ray imagers with tighter process control and using positive bias voltage

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Gary Virshup, Paul Bennett, Kanai Shah, Yuri Dmitriev, Jerry Thomas

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.535994

KEYWORDS: Imaging systems, X-rays, X-ray imaging, Modulation transfer functions, Lead, Amorphous silicon, Process control, Electrodes, Glasses, Electrons

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Proceedings Article | 20 January 2004 Paper

Paper

Characterization of mercuric iodide photoconductor for radiographic and fluoroscopic medical imagers

Barry Breen, Ofer Dagan, Leonid Melekhov, Michael Schieber, Haim Gilboa, George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Gary Virshup

Proceedings Volume 5198, (2004) https://doi.org/10.1117/12.510871

KEYWORDS: Photoresistors, Electrodes, X-rays, Imaging systems, Sensors, X-ray detectors, Image resolution, Aluminum, X-ray imaging, Palladium

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Proceedings Article | 1 August 2003 Paper

Paper

Detailed imager evaluation and unique applications of a new 20cmx25-cm size mercuric iodide thick film x-ray detector

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Gary Virshup, Barry Breen, Alexander Vilensky, Ofer Dagan, E. Meerson, M. Schieber, Haim Gilboa, Jerry Thomas

Proceedings Volume 5047, (2003) https://doi.org/10.1117/12.484035

KEYWORDS: Imaging systems, X-rays, Sensors, Modulation transfer functions, Photoresistors, X-ray detectors, Electrodes, Palladium, X-ray imaging, Nondestructive evaluation

Read Abstract +

We previously reported on 2"x 2" and 4" x 4" size imagers, direct digital radiography X-ray detectors, based on photoconductive polycrystalline mercuric iodide deposited on a flat panel thin film transistor (TFT) array, as having great potential for use in medical imaging, NDE, and security applications. Recently we successfully upgraded our mercuric iodide deposition technique to 20 cm x 25 cm size, the size required in common NDE and security imaging applications. A TFT array with a pixel pitch of 127 microns was used for this imager. The mercuric iodide direct conversion layers were vacuum deposited onto TFT array by Physical Vapor Deposition (PVD). In addition to successful imager scale up, more sophisticated, non-TFT based detectors were developed in order to improve analysis methods of the mercuric iodide photoconductor. Measurements on mercuric iodide photoconductor were performed using a 36 x 6 electrode array on a 10cm x 10cm substrate (total of 216 measurement points). The array is formed by 36 palladium stripes on the glass substrate, upon which the mercuric iodide is deposited, and 6 palladium stripes that are deposited on top of the mercuric iodide layer. These two sets of electrodes are oriented at 90 degrees to each other to create the measurement matrix. These detectors were evaluated in radiographic mode, continuous fluoroscopic mode and pulsed fluoroscopic mode. Mercuric iodide coatings with thickness ranging between 140 microns and 300 microns were tested using beams with energies between 40 kVp and 100 kVp utilizing exposure ranges typical for both fluoroscopic and radiographic imaging. Diagnostic quality radiographic and fluroscopic images at up to 15 pulses per second were demonstrated. We evaluated the dark current, sensitivity and MTF characteristics. The MTF is determined primarily by the aperture and pitch of the TFT array with Nyquist frequency of ~3.93 mm^-1 (127 micron pixel pitch). The MTF curve of a good quality HgI2 imager is very close to the theoretical sinc function. Image lag characteristics of mercuric iodide appear adequate for fluoroscopic rates.

Proceedings Article | 1 August 2003 Paper

Paper

A new unique electrostatic imager for nondestructive evaluation of printed circuit boards

George Zentai, Larry Partain, Cesar Proano, Syuji Yamaoka

Proceedings Volume 5047, (2003) https://doi.org/10.1117/12.484062

KEYWORDS: Imaging systems, Nondestructive evaluation, Electrodes, Dielectrics, Digital imaging, Electronics, Defect detection, Capacitance, Pulse generators, Printed circuit board testing

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Proceedings Article | 5 June 2003 Paper

Paper

Mercuric iodide and lead iodide x-ray detectors for radiographic and fluoroscopic medical imaging

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Gary Virshup, L. Melekhov, A. Zuck, Barry Breen, O. Dagan, A. Vilensky, Michael Schieber, Haim Gilboa, Paul Bennet, Kanai Shah, Yuriy Dmitriyev, Jerry Thomas, Martin Yaffe, David Hunter

Proceedings Volume 5030, (2003) https://doi.org/10.1117/12.480227

KEYWORDS: Imaging systems, X-rays, Lead, Modulation transfer functions, Photoresistors, Sensors, X-ray detectors, Medical imaging, X-ray imaging, Image resolution

Read Abstract +

Mercuric iodide (HgI₂) and lead iodide (PbI₂) have been under development for several years as direct converter layers in digital x-ray imaging. Previous reports have covered the basic electrical and physical characteristics of these and several other materials. We earlier reported on 5cm x 5cm and 10cm x 10cm size imagers, direct digital radiography X-ray detectors, based on photoconductive polycrystalline mercuric iodide deposited on a flat panel thin film transistor (TFT) array, as having great potential for use in medical imaging, NDT, and security applications. This paper, presents results and comparison of both lead iodide and mercuric iodide imagers scaled up to 20cm x 25cm sizes. Both the mercuric iodide and lead iodide direct conversion layers are vacuum deposited onto TFT array by Physical Vapor Deposition (PVD). This process has been successfully scaled up to 20cm x 25cm -- the size required in common medical imaging applications. A TFT array with a pixel pitch of 127 microns was used for this imager. In addition to increasing detector size, more sophisticated, non-TFT based small area detectors were developed in order to improve analysis methods of the mercuric and lead iodide photoconductors. These small area detectors were evaluated in radiographic mode, continuous fluoroscopic mode and pulsed fluoroscopic mode. Mercuric iodide coating thickness ranging between 140 microns and 300 microns and lead iodide coating thickness ranging between 100 microns and 180 microns were tested using beams with energies between 40 kVp and 100 kVp, utilizing exposure ranges typical for both fluoroscopic and radiographic imaging. Diagnostic quality radiographic and fluoroscopic images have been generated at up to 15 frames per second. Mercuric iodide image lag appears adequate for fluoroscopic imaging. The longer image lag characteristics of lead iodide make it only suitable for radiographic imaging. For both material the MTF is determined primarily by the aperture and pitch of the TFT array (Nyquist frequency of ~3.93 mm^-1 (127 micron pixel pitch).

Proceedings Article | 10 January 2003 Paper

Paper

Medical imaging with mercuric iodide direct digital radiography flat-panel x-ray detectors

Haim Gilboa, Asaf Zuck, O. Dagan, Alex Vilensky, B. Breen, A. Taieb, B. Reisman, H. Hermon, George Zentai, Larry Partain, Robert Street, S. Ready

Proceedings Volume 4784, (2003) https://doi.org/10.1117/12.450503

KEYWORDS: X-rays, Sensors, X-ray detectors, Image resolution, Signal attenuation, Selenium, Coating, Imaging arrays, X-ray imaging, Imaging systems

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Proceedings Article | 11 June 2002 Paper

Paper

Large area mercuric iodide thick film x-ray detectors for fluoroscopic (on-line) imaging

George Zentai, Larry Partain, Raisa Pavlyuchkova, Cesar Proano, Gary Virshup, Barry Breen, Asaf Zuck, Benjamin Reisman, A. Taieb, Michael Schieber

Proceedings Volume 4702, (2002) https://doi.org/10.1117/12.469906

KEYWORDS: X-rays, Imaging systems, Sensors, X-ray imaging, X-ray detectors, Image resolution, Modulation transfer functions, Imaging arrays, Nondestructive evaluation, Coating

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Proceedings Article | 3 May 2002 Paper

Paper

Large-area mercuric iodide x-ray imager

George Zentai, Larry Partain, Raisa Pavlyuchkova, Gary Virshup, Asaf Zuck, Leonid Melekhov, O. Dagan, Alexander Vilensky, Haim Gilboa

Proceedings Volume 4682, (2002) https://doi.org/10.1117/12.465604

KEYWORDS: Sensors, X-rays, X-ray imaging, Image resolution, X-ray detectors, Thin film coatings, Imaging arrays, Modulation transfer functions, Imaging systems, Signal attenuation

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Single crystals of mercuric iodide have been studied for many years for nuclear detectors. We have investigated the use of x-ray photoconductive polycrystalline mercuric iodide coatings on amorphous silicon flat panel thin film transistor (TFT) arrays as x-ray detectors for radiographic and fluoroscopic applications in medical imaging. The mercuric iodide coatings were vacuum deposited by Physical Vapor Deposition (PVD). This coating technology is capable of being scaled up to sizes required in common medical imaging applications. Coatings were deposited on 4 inches X 4 inches TFT arrays for imaging performance evaluation and also on conductive-coated glass substrates for measurements of x-ray sensitivity, dark current and image lag. The TFT arrays used included pixel pitch dimensions of both 100 and 139 microns. Coating thickness between 150 microns and 250 microns were tested in the 25 kVp-100 kVp x-ray energy range utilizing exposures typical for both fluoroscopic, and radiographic imaging. X-ray sensitivities measured for the mercuric iodide samples and coated TFT detectors were superior to any published results for competitive materials (up to 7100 ke/mR/pixel for 100 micron pixels). It is believed that this higher sensitivity, can result in fluoroscopic imaging signal levels high enough to overshadow electronic noise. Image lag characteristics appear adequate for fluoroscopic rates. Resolution tests on resolution target phantoms showed that resolution is limited to the Nyquist frequency for the 139 micron pixel detectors. The ability to operate at low voltages gives adequate dark currents for most applications and allows low voltage electronics designs. Mercuric Iodide coated TFT arrays were found to be outstanding candidates for direct digital radiographic detectors for both static and dynamic (fluoroscopic) applications. Their high x-ray sensitivity, high resolution, low dark current, low voltage operation, and good lag characteristics provide a unique combination of desirable imaging performance parameters.

Proceedings Article | 19 December 2001 Paper

Paper

Electrical properties of polycrystalline mercuric iodide x-ray detectors

Haim Hermon, Robert Street, Leonid Melekhov, Asaf Zuck, Alexander Vilensky, Steve Ready, George Zentai, Michael Schieber, Larry Partain

Proceedings Volume 4508, (2001) https://doi.org/10.1117/12.450792

KEYWORDS: Sensors, X-rays, X-ray detectors, Spatial resolution, Imaging arrays, X-ray imaging, Imaging systems, Amorphous silicon, Radiography, Image resolution

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Proceedings Article | 24 July 2001 Paper

Paper

Nondestructive imaging with mercuric iodide thick film x-ray detectors

Michael Schieber, Haim Hermon, Asaf Zuck, Alexander Vilensky, Leonid Melekhov, Michael Lukach, Evgenie Meerson, Yehezkel Saado, E. Shtekel, Benjamin Reisman, G. Zentai, L. Partain, E. Seppi, Raisa Pavlyuchkova, G. Virshup, Robert Street, Steve Ready

Proceedings Volume 4335, (2001) https://doi.org/10.1117/12.434200

KEYWORDS: Imaging systems, X-rays, Sensors, Image resolution, Nondestructive evaluation, X-ray detectors, Surface plasmons, X-ray imaging, Crystals, Electrodes

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Proceedings Article | 28 June 2001 Paper

Paper

Deposition of thick films of polycrystalline mercuric iodide x-ray detectors

Haim Hermon, Michael Schieber, Asaf Zuck, Alexander Vilensky, Leonid Melekhov, E. Shtekel, A. Green, O. Dagan, Steve Ready, Robert Street, E. Seppi, Raisa Pavlyuchkova, G. Virshup, G. Zentai, L. Partain

Proceedings Volume 4320, (2001) https://doi.org/10.1117/12.430922

KEYWORDS: Imaging systems, Sensors, X-ray imaging, X-rays, Electrodes, X-ray detectors, Imaging arrays, Dielectrics, Clocks, Physical vapor deposition

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SPIE Journal Paper | 1 April 1998

Charge-coupled device/fiber optic taper array x-ray detector for protein crystallography

Istvan Naday, Stephan Ross, Edwin Westbrook, George Zentai

OE, Vol. 37, Issue 04, (April 1998) https://doi.org/10.1117/12.10.1117/1.601789

KEYWORDS: Sensors, Charge-coupled devices, X-rays, X-ray detectors, CCD image sensors, Proteins, Crystals, X-ray imaging, Crystallography, Diffraction

Proceedings Article | 25 April 1997 Paper

Paper

Charge-coupled-device fiber optic taper array x-ray detector for protein crystallography

Istvan Naday, Stephan Ross, Edwin Westbrook, George Zentai

Proceedings Volume 3019, (1997) https://doi.org/10.1117/12.275187

KEYWORDS: Sensors, Charge-coupled devices, X-rays, X-ray detectors, Fiber optics, CCD image sensors, Proteins, Crystallography, X-ray imaging, Diffraction

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Showing 5 of 25 publications

Conference Committee Involvement (18)

Health Monitoring of Structural and Biological Systems X

21 March 2016 | Las Vegas, Nevada, United States

Health Monitoring of Structural and Biological Systems IX

9 March 2015 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VIII

10 March 2014 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VII

11 March 2013 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems VI

12 March 2012 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems V

7 March 2011 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems IV

8 March 2010 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems III

9 March 2009 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems II

10 March 2008 | San Diego, California, United States

Health Monitoring of Structural and Biological Systems

19 March 2007 | San Diego, California, United States

Health Monitoring and Smart NDE of Structural and Biological Systems V

27 February 2006 | San Diego, CA, United States

Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems V

26 February 2006 |

Nondestructive Detection and Measurement for Homeland Security III

7 March 2005 | San Diego, CA, United States

Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems IV

7 March 2005 | San Diego, CA, United States

Nondestructive Detection and Measurement for Homeland Security II

17 March 2004 | San Diego, CA, United States

Health Monitoring and Smart Nondestructive Evaluation of Structural and Biological Systems III

15 March 2004 | San Diego, CA, United States

Nondestructive Detection and Measurement for Homeland Security

4 March 2003 | San Diego, California, United States

Smart Nondestructive Evaluation and Health Monitoring of Structural and Biological Systems

3 March 2003 | San Diego, California, United States

Showing 5 of 18 Conference Committees

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