Effective detective quantum efficiency of two detectors in a prototype digital breast tomosynthesis

Choi, Seokjin; Choi, Sunghoon; Lee, Dong‐Hoon; Kim, Yeseul; Choi, Young-Wook; Kim, Hee-Joung

doi:10.1016/j.ijleo.2018.10.094

Cited by 2 publications

(2 citation statements)

References 19 publications

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“…The development of such active pixel arrays using TFTs fabricated with polycrystalline silicon, a semiconductor material offering electron mobilities two orders of magnitude higher than a-Si:H as well as similar radiation damage resistance and the same large-area fabrication capabilities, is being explored (Koniczek et al 2020). In addition, active pixel arrays based on crystalline silicon (c-Si) transistors and fabricated using standard CMOS fabrication techniques are under investigation for use in digital breast tomosynthesis (DBT) (Zhao et al 2015, Peters et al 2016, Choi et al 2019. CMOS devices offer high frame rates by virtue of the high mobilities provided by c-Si as well as low lag, but are considerably more susceptible to radiation damage than a-Si:H devices and the fabrication process does not lend itself to economic manufacture of large area, monolithic devices.…”

Section: Introductionmentioning

confidence: 99%

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Shen¹,

Antonuk²,

El‐Mohri³

et al. 2023

Phys. Med. Biol.

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Objective. Polycrystalline mercuric iodide photoconductive converters fabricated using particle-in-binder techniques (PIB HgI2) provide significantly more detected charge per x-ray interaction than from a-Se and CsI:Tl converters commonly used with active matrix flat-panel imagers (AMFPIs). This enhanced sensitivity makes PIB HgI2 an interesting candidate for applications involving low x-ray exposures—since the relatively high levels of additive electronic noise exhibited by AMFPIs incorporating a-Se and CsI:Tl reduce detective quantum efficiency (DQE) performance under such conditions. A theoretical study is reported on an approach for addressing a major challenge impeding practical use of PIB HgI2 converters—the high lag exhibited by the material (over 10%) which would lead to undesirable image artifacts in applications involving acquisition of consecutive images such as digital breast tomosynthesis. Approach. Charge transport modeling accounting for the trapping and release of holes (thought to be the primary contributor to lag) was used to examine signal properties, including lag, of pillar-supported Frisch grids embedded in the photoconductor for 100 μm pitch AMFPI pixels. Performance was examined as a function of electrode voltage, grid pitch (center-to-center distance between neighboring grid wires) and the ratio of grid wire width to grid pitch. Main results. Optimum grid designs maximizing suppression of signal generated by hole transport, without significantly affecting the total signal due to electron and hole transport, were identified and MTF was determined. For the most favorable designs, additional modeling was used to determine DQE. The results indicate that, through judicious choice of grid design and operational conditions, first frame lag can be significantly reduced to below 1%—less than the low levels exhibited by a-Se. DQE performance is shown to be largely maintained as exposure decreases—which should help to maintain good image quality. Significance. Substantial reduction of lag in PIB HgI2 converters via incorporation of Frisch grids has been demonstrated through modeling.

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Section: Introductionmentioning

confidence: 99%

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Shen¹,

Antonuk²,

El‐Mohri³

et al. 2023

Phys. Med. Biol.

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“…One approach is to replace the arrays used in AMFPIs (Antonuk et al 1992, Zhao andRowlands 1995) with active pixel (AP) arrays-in which each pixel incorporates one or more amplification stages in the circuit (Fossum 1993). AP arrays based on crystalline silicon circuits are under investigation for use in DBT systems (Zhao et al 2015, Peters et al 2016, Choi et al 2019 and AP arrays based on polycrystalline silicon circuits (which provide the same advantages of very large-area, monolithic array fabrication and high radiation damage resistance offered by a-Si:H) are under development (Koniczek et al 2017(Koniczek et al , 2018(Koniczek et al , 2020. An alternative approach for improving the signal-to-noise ratio of AMPFIs is to replace existing a-Se and CsI:Tl converters with a converter offering significantly higher gain.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of the signal performance of HgI₂ x-ray converters incorporating a Frisch grid structure at mammographic energies

et al. 2021

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Active matrix, flat-panel imagers (AMFPIs) suffer from decreased detective quantum efficiency under conditions of low dose per image frame (such as for digital breast tomosynthesis, fluoroscopy and cone-beam CT) due to low signal compared to the additive electronic noise. One way to address this challenge is to introduce a high-gain x-ray converter called particle-in-binder mercuric iodide (PIB HgI2) which exhibits 3–10 times higher x-ray sensitivity compared to that of a-Se and CsI:Tl converters employed in commercial AMFPI systems. However, a remaining challenge for practical implementation of PIB HgI2 is the high level of image lag, which is believed to largely originate from the trapping of holes. Towards addressing this challenge, this paper reports a theoretical investigation of the use of a Frisch grid structure embedded in the converter to suppress hole signal—which would be expected to reduce image lag. The grid acts as a third electrode sandwiched between a continuous top electrode and pixelated bottom electrodes having a 100 μm pitch. Signal properties of such a detector are investigated as a function of VDR (the ratio of the voltage difference between the electrodes in the region below the grid to that above the grid), grid pitch (the center-to-center distance between two neighboring grid wires) and R GRID (the ratio of grid wire width to grid pitch) for mammographic x-ray energies. The results show that smaller grid pitch suppresses hole signal to a higher degree (up to ∼96%) while a larger gap between grid wires and higher VDR provide minimally impeded electron transport. Examination of the tradeoff between maximizing electron signal and minimizing hole signal indicates that a grid design having a grid pitch of 20 μm with R GRID of 50% and 65% provides hole signal suppression of ∼93% and ∼95% for VDR of 1 and 3, respectively.

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Effective detective quantum efficiency of two detectors in a prototype digital breast tomosynthesis

Cited by 2 publications

References 19 publications

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Theoretical investigation of the signal performance of HgI₂ x-ray converters incorporating a Frisch grid structure at mammographic energies

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Effective detective quantum efficiency of two detectors in a prototype digital breast tomosynthesis

Cited by 2 publications

References 19 publications

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Minimization of image lag in polycrystalline mercuric iodide converters through incorporation of Frisch grid structures for digital breast tomosynthesis

Theoretical investigation of the signal performance of HgI2 x-ray converters incorporating a Frisch grid structure at mammographic energies

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Theoretical investigation of the signal performance of HgI₂ x-ray converters incorporating a Frisch grid structure at mammographic energies