Amorphous Silicon Image Sensor Arrays

Powell, M. J.; French, I. D.; Hughes, J.B.; Bird, N.C.; Davies, O S; Glasse, C.; Curran, J.E.

doi:10.1557/proc-258-1127

Cited by 50 publications

(12 citation statements)

References 11 publications

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“…With the gate pulse width of 12 ts nearly complete charge readout (> 98 %) is achieved, and hence there is only a small contribution of the readout process to image lag (cf. 3…”

Section: Demonstrator Performancementioning

confidence: 99%

<title>Fluoroscopic x-ray imaging with amorphous silicon thin-film arrays</title>

et al. 1994

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The dream ofan all-solid state large area x-ray image sensor with digital readout and full dynamic performance will most probably find a first realisation in two-dimensional thin-film amorphous silicon arrays. In this paper we address in particular the evaluation of the limits of the signal/noise ratio in this concept. Using small prototype detectors measurements of MTF and noise power spectra have been made as a function of x-ray dose. The results are given in terms of the detective quantum efficiency (DQE) as a function of dose and spatial frequency. We further present an analysis of the different noise so rces and their dependence on the detector parameters, and we provide estimates on the maximum signals that may be achieved per unit dose. The intrinsic lag of the amorphous silicon photodiodes causes a second problem area with this type ofx-ray detectors. Especially in radiography/fluoroscopy mixed applications, memory effects may not be negligible.

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“…With the gate pulse width of 12 ts nearly complete charge readout (> 98 %) is achieved, and hence there is only a small contribution of the readout process to image lag (cf. 3…”

Section: Demonstrator Performancementioning

confidence: 99%

<title>Fluoroscopic x-ray imaging with amorphous silicon thin-film arrays</title>

et al. 1994

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“…In the indirect method the phosphor layer is used to absorb x rays and the resultant light photons are detected by an active matrix array with a single photo-diode and thin film transistor TFT switch at each pixel. 4,5,6,7 The photodiode absorbs the light given off by the phosphor in proportion to the x-ray energy absorbed. The TFTs are used to readout the stored charge to produce a digital image.…”

Section: Introductionmentioning

confidence: 99%

Effect of depth-dependent modulation transfer function and K-fluorescence reabsorption on the detective quantum efficiency of indirect-conversion flat-panel x-ray imaging systems using CsI

Rowlands

Zhao

2001

Medical Imaging 2001: Physics of Medical Imaging

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A theory of the imaging behavior of structured phosphor layers is developed based on linear analysis and Monte Carlo modeling and tested by comparison with experiments. The experiments include: modulation transfer function (MTF) measured as a function of spatial frequency f on CsI phosphor layers of different thicknesses and optical properties (e.g. presence or absence of reflective backing layer). These measurements on structured screens were used to establish phosphor parameters (e.g. absorption and scattering lengths). In addition, MTF(f), Wiener noise power spectra [NPS(f)] and detective quantum efficiency [DQE(f)] measurements were obtained from the literature for x-ray image intensifiers and indirect conversion flat panel detectors constructed using CsI layers. These results were compared with the theory using the previously established phosphor parameters. The effects of K-fluorescence and depth dependence of the MTF on DQE (i.e. Lubberts' effect) were investigated.

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“…This widely perceived need has, in turn, stimulated considerable innovation resulting in a remarkable variety of [3] 450 256x240 61440 11.5x10.8 124 [4] 450 512x560 286720 23.0x25.2 580 [5] 450 512x560 286720 23.0x25.2(x4) 2318 [6] 270 64x40 2560 1.7x1.1 1.9 [2] 200 192x192 36864 3.8x3. 8 14.4 [7] 200 1024x1024 1048576 20x20 400 [8] 127 1536x1920 2929920 19.5x24.4 476 [9] 127 1536x1920 2929920 19.5x24.4 476 [10] 127 1536x1920 2929920 19 [13] 100 notavailable n.a. n.a.…”

Section: Introductionmentioning

confidence: 99%

Large-area 97-μm pitch indirect-detection active-matrix flat-panel imager (AMFPI)

et al. 1998

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The development of the highest resolution, large-area, active-matrix, flat-panel imager (AMFPI) thus far reported is described. This imager is based on a 97 jtm pixel pitch array with each pixel comprising a single a-Si:H TFT coupled to a discrete a-Si:H n-i-p photodiode. While the initial configuration chosen for fabrication is a 2048x2048 pixel array, a larger monolithic array format of 3072x4096 pixels is also permitted by the design. When coupled to an overlying scintillator such as a phosphor screen or CsI:Tl, the array allows indirect detection of incident radiation. The array is operated in conjunction with a recently completed electronic acquisition system featuring asynchronous operation, a large addressing range, fast analog signal extraction and digitization, and 16-bit digitization. This imager, whose empirical characterization will be reported in a subsequent paper, was developed as an engineering prototype to allow investigation of the performance limits of the most aggressive array designs permitted by present active-matrix technology. The development of this new imager builds upon knowledge acquired from the iterative design, fabrication, and quantitative evaluation of earlier engineering prototypes based on a series of 127 im pitch arrays. This paper summarizes the general program of research leading to this new device and puts this in the context of world-wide developments in indirect and direct detection AMFPI technology. Some limitations of present AMFPI technology are described, and possible solutions are discussed.Specifically, the incorporation of multiplexers based on poly-crystalline silicon circuitry into the array design, to facilitate very high resolution imagers, are proposed. In addition, strategies to significantly improve AMFPI performance at very low exposures, such as those commonly encountered in fluoroscopy, involving the reduction of additive noise (such as through lower preamplifier noise) and the enhancement of system gain (such as through the use of lead iodide) are discussed and initial calculations illustrating potential levels ofperformance are presented.

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Amorphous Silicon Image Sensor Arrays

Cited by 50 publications

References 11 publications

<title>Fluoroscopic x-ray imaging with amorphous silicon thin-film arrays</title>

<title>Fluoroscopic x-ray imaging with amorphous silicon thin-film arrays</title>

Effect of depth-dependent modulation transfer function and K-fluorescence reabsorption on the detective quantum efficiency of indirect-conversion flat-panel x-ray imaging systems using CsI

Large-area 97-μm pitch indirect-detection active-matrix flat-panel imager (AMFPI)

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