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

Zentai, George; Partain, L. D.; Pavlyuchkova, Raisa; Proano, Cesar; Virshup, G. F.; Melekhov, Leonid; Zuck, Asaf; Breen, Barry; Ofer, Dagan,; Vilensky, A. I.; Schieber, M.; Gilboa, H.; Bennet, Paul; Shah, K.S.; Dmitriyev, Y.; Thomas, Jerry A.; Yaffe, Martin J.; Hunter, David M.

doi:10.1117/12.480227

Cited by 46 publications

(21 citation statements)

References 15 publications

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“…However, at low electric fields (i.e., <0.4 V µm −1 ) the trend is reversed due to a significant reduction in fluoroscopic signal caused by the polarization effect noted in the discussion of figure 9(a) data. This behaviour has been independently observed by others (Zentai et al 2003) on similar film detectors.…”

Section: Radiographic and Fluoroscopic Measurementssupporting

confidence: 79%

The tris(trimethylsilyl)silyl group in organic, coordination and organometallic chemistry

Корнев¹

2004

Russ. Chem. Rev.

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The signal properties of polycrystalline mercuric iodide (HgI 2 ) film detectors, under irradiation conditions relevant to mammographic, radiographic, fluoroscopic and radiotherapy x-ray imaging, are reported. Each film detector consists of an ∼230 to ∼460 µm thick layer of HgI 2 (fabricated through physical vapour deposition or a screen-print process) and a thin barrier layer, sandwiched between a pair of opposing electrode plates. The high atomic number, high density and low effective ionization energy, W EFF , of HgI 2 make it an attractive candidate for significantly improving the performance of active matrix, flat-panel imagers (AMFPIs) for several x-ray imaging applications. The temporal behaviour of current from the film detectors in the presence and in the absence of radiation was used to examine dark current levels, the lag and reciprocity of the signal response, x-ray sensitivity and W EFF . The results are discussed in the context of present AMFPI performance. This study provides performance data for a wide range of potential medical x-ray imaging applications from a single set of detectors and represents the first investigation of the signal properties of polycrystalline mercuric iodide for the radiotherapy application.Z Su et al

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Section: Radiographic and Fluoroscopic Measurementssupporting

confidence: 79%

The tris(trimethylsilyl)silyl group in organic, coordination and organometallic chemistry

Корнев¹

2004

Russ. Chem. Rev.

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“…3 Earliest results indicated that we were able to produce acceptable sensitivity (>6 µC/R*cm 2 ) but the dark current was high (>100pA/mm 2 ) with negative bias. We also observed high image lag, close to 50%.…”

Section: Test Results With A-si Tft Imagermentioning

confidence: 95%

“…Wide bandgap semiconductors are finding new application areas in the development of digital x-ray imaging technologies [3][4][5][6][7][8] . A common detector design incorporates a semiconductor converter layer deposited directly upon a thin film transistor array that provides both pixellation and switching capability.…”

Section: Introductionmentioning

confidence: 99%

Improved properties of PbI 2 x-ray imagers with tighter process control and using positive bias voltage

et al. 2004

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Vapor deposited lead iodide films show a wide range of physical attributes dependant upon fabrication conditions. High density is most readily achieved with films less than 100 µm. Thicker films, with lessening density, often show lower response (gain) as charge collection becomes less efficient. Lack of consistency in density throughout a deposition invariably leads to non-uniform electronic properties, which is challenging to both model and predict. To overcome this, tighter control of deposition parameters is required during the slow growth process (<10 µm/hour). Lead iodide films are characterized in forms of planar devices deposited onto conductive glass and active pixel arrays deposited onto a-Si TFT arrays 1 . Electronic properties (e.g. leakage current, gain) show little variation that can be traced to substrate choice. Films generally provide less than 100 pA/mm 2 leakage current as they show saturation in gain (at approximate fields of 1 V/µm). We recently modified our readout electronics to accept positive bias. Using positive bias on the top electrode provides better charge collection for the lower mobility electrons and (despite process variability) better quality films can provide sensitivities greater than 6 µC/R*cm 2 , with only partial x-ray absorption, and show less than 20 pA/mm 2 dark current.

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“…Recently, many research groups have programs to develop alternative direct conversion materials such as PbO, PbI 2 , HgI 2 , or other solid-state photoconductors [2,3,4,5]. Even though all these materials show promise in their higher efficiency of charge generation, so far, each has some basic properties that requires improvement.…”

Section: Introductionmentioning

confidence: 98%

Selenium detector with a grid for selenium charge gain

Lee

2005

Medical Imaging 2005: Physics of Medical Imaging

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Amorphous selenium direct-conversion x-ray detectors have been used successfully for full field digital mammography (FFDM) and digital radiography (DR). Such detectors characteristically exhibit high spatial resolution and conversion efficiency that is a function of the applied electric field [1]. At an electric field of 10 volts per micron, about 50 electron volts of photon energy are required to generate an electron-hole pair in a typical amorphous selenium x-ray conversion layer. At FFDM and DR imaging x-ray energies each absorbed photon can generate only about 250 to 1000 electronhole pairs. Each absorbed x-ray photon is only contributing 4x10 -17 to 1.6x10 -16 coulombs of imaging charge. On the noise side, detectors operating at room temperature have a basic thermal (kTC) noise of 300 to 600 electrons per pixel from the image charge storage capacitor. Electronic noise from the front-end charge amplifier is also amplified by one plus the ratio of the TFT data line capacitance and the feedback capacitance of the charge amplifier. Medical imaging applications must therefore employ low noise thin film transistor (TFT) arrays, low data line capacitance and low noise charge integration amplifiers to achieve high signal-to-noise ratio (SNR) and detective quantum efficiency (DQE).To achieve quantum-noise limited imaging results with the lowest practical x-ray exposure dose, it is desirable to include an additional low-noise gain stage in the x-ray conversion layer. This is particularly important for the application of dynamic imaging or for tomosynthesis where x-ray dose per frame is very limited. A new structure for an amorphous selenium detector that employs an internal biased gain grid to cause avalanche-gain within the x-ray conversion layer is being proposed. A signal charge amplification of at least 10X can be achieved without introducing excessive noise. Quantum-limited image detection should then be attainable for even very low exposures.

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

Cited by 46 publications

References 15 publications

The tris(trimethylsilyl)silyl group in organic, coordination and organometallic chemistry

The tris(trimethylsilyl)silyl group in organic, coordination and organometallic chemistry

Improved properties of PbI 2 x-ray imagers with tighter process control and using positive bias voltage

Selenium detector with a grid for selenium charge gain

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