Dr. Haim Gilboa Profile

Dr. Haim Gilboa

Vice President Engineering at Real Time Radiography Ltd

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Publications (7)

Proceedings Article | 6 May 2004 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 | 20 January 2004 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

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

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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 | 5 June 2003 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

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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

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 | 3 May 2002 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 | 16 April 1993 Paper

Noncontact temperature monitoring of semiconductors by optical absorption edge sensing

Michael Adel, Yaron Ish-Shalom, Shmuel Mangan, Dario Cabib, Haim Gilboa

Proceedings Volume 1803, (1993) https://doi.org/10.1117/12.142924

KEYWORDS: Semiconducting wafers, Absorption, Temperature metrology, Reflection, Semiconductors, Wafer-level optics, Reflectance spectroscopy, Reflectivity, Databases, Plasma etching

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