Improving spatial resolution of high stopping power X- and gamma-ray cameras:

Gerstenmayer, Jean-Louis

doi:10.1016/s0168-9002(00)00833-0

Cited by 4 publications

(4 citation statements)

References 12 publications

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“…The concept of using segmented phosphor to increase the QE of area detectors has also been demonstrated. 6,7 Although the details of designing a high-QE flat panel detector require further investigation, we believe that the designs should follow these general rules: ͑1͒ The conversion layer of the detector ͑whether it is a direct or indirect͒ should be made of high density materials to achieve both high QE and high MTF; ͑2͒ if a large number of HDM converters are used in the conversion layer, they should be uniformly distributed so that QE is homogeneous across the detector; ͑3͒ the size of each HDM converter ͑as well as the size of each pixel of the TFT matrix͒ should be small compared to the intrinsic FWHM of the LSF to achieve the best MTF ͑the HDM converters should also be smaller than the electron range in the HDM so that most energetic electrons created in the converters can escape and generate ions in the medium͒; ͑4͒ the applied electric field to drive ions ͑or the optical segments to guide the optical photons͒ should be focused to the x-ray source to reduce the blurring due to oblique incidence of off-axis x rays. In addition, the HDM converters and the medium should have certain properties so that the detector has the highest possible DQE for a given QE and MTF.…”

Section: Discussionmentioning

confidence: 99%

“…2͑a͔͒ are mainly used to absorb x rays and convert them into energetic electrons, which, in turn, generate ions ͑in the case of direct conversion͒ or optical photons ͑in the case of indirect conversion͒ in the medium. The HDM converters could be metallic, e.g., made of W. 7,8 The medium of negligible density could be air for direct conversion or low-density organic phosphor for indirect conversion. In direct conversion, the ions generated in the medium are guided by an applied electric field with field lines focused toward the x-ray source ͑e.g., negative ions move up and positive ions move down along the field lines͒.…”

Section: The Modelmentioning

confidence: 99%

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Development of high quantum efficiency flat panel detectors for portal imaging: Intrinsic spatial resolution

Pang

Rowlands

2002

Medical Physics

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Recently developed flat panel detectors have been proven to have a much better image quality than conventional electronic portal imaging devices (EPIDs). They are, however, not yet the ideal systems for portal imaging application due to the low x-ray absorption, i.e., low quantum efficiency (QE), which is typically on the order of 2-4% as compared to the theoretical limit of 100%. The QE of current flat panel systems can be improved by significantly increasing the thickness of the energy conversion layer (i.e., amorphous selenium or phosphor screen). This, however, will be at the expense of a decrease in spatial resolution mainly due to x-ray scatter in the conversion layer (and also the spread of optical photons in the case of phosphor screen). In this paper, we investigate theoretically the intrinsic spatial resolution of a high QE flat panel detector with a new energy conversion layer that is much denser and thicker than that of current flat panel systems. The modulation transfer function (MTF) of the system is calculated based on a theoretical model using a novel approach, which uses an analytical expression for absorbed dose. It is found that if appropriate materials are used for the conversion layer, then the intrinsic MTF of the high QE flat panel is better than that of current EPIDs, and in addition they have a high QE (e.g., approximately 60%). Some general rules for the design of the conversion layer to achieve both high QE and high resolution as well as high DQE are also discussed.

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Section: Discussionmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Development of high quantum efficiency flat panel detectors for portal imaging: Intrinsic spatial resolution

Pang

Rowlands

2002

Medical Physics

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“…Segmentation method can be applied in order to improve the stopping power (macroscopic cross section) and reduce the effect of lateral energy spread on the resolution (sampling and averaging) [1] [2]. Of course, because of the X-ray pulse shortness and the electronic properties of the semiconductor, it is not possible to distinguish each photon inside a single shot.…”

Section: Introductionmentioning

confidence: 99%

Toward ultrafast high-DQE and multi-image CZT gamma-camera prospecting

et al. 2003

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The development of high frame rate imaging high energy X-rays detector system is discussed. The purpose of this paper is to highlight some of the issues involved in the development of high performance position sensitivex-and gamma-ray cameras for high frame rate imaging. New CZT technology has provided some prototypes offering more than 50% stopping power (and millimetric spatial resolution) for 5 MeV X-ray pulses. Some different CdTe and CdZnTe sensors were tested with MeV energy photons produced by the accelerators ELSA and ARCO (CEA Bruyères-le-Châtel). The first experimental results obtained at CEA with 20 ps long are very encouraging for high energy high frame rate imaging applications.

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“…In the case of Positron Emission Tomography (PET), better spatial resolution and detection efficiency need most often the use of shaped crystals of smaller sections (typically 1mm 2 ), of longer lengths (sometimes several tens of mm) and well defined section shapes. For industrial X-ray imaging, CdWO 4 crystals with cross-section of 0.6x0.6mm 2 are used, and some devices are proposed using BGO cylinders of 0.1mm diameter for better spatial resolution [2] (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Crystal Fibers and Thin Films for Imaging Applications

Pédrini

Dujardin

NATO Security Through Science Series

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Huge progress in the elaboration of crystal fibers and thin films of scintillating materials opens new opportunities for the improvement of imaging techniques and the design of new systems. It is particularly true in the case of medical imaging for which better spatial resolution and sensitivity are required for clear diagnostics in major diseases. Different techniques of elaboration of crystal fibers and thin films are presented with their advantages and drawbacks. For fibers, Laser Heated Pedestal Growth (LHPG), Micro Pulling-Down (MPD), Edge-defined Film-fed Growth (EFG) and Internal Crystallization Method (ICM) are described. Their merits are compared and some are adapted for industrial production. Their use in PET scanners and other detectors are promising to increase the spatial resolution. Two kind of scintillating thin films are of interest for imaging applications: films deposited on substrates through liquid phase and molecular beam epitaxy, sol-gel coating and pulsed laser deposition; films created by irradiation of crystals and containing color centers. Examples of applications are given concerning mainly X-ray imaging with high spatial resolution.

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Improving spatial resolution of high stopping power X- and gamma-ray cameras:

Cited by 4 publications

References 12 publications

Development of high quantum efficiency flat panel detectors for portal imaging: Intrinsic spatial resolution

Development of high quantum efficiency flat panel detectors for portal imaging: Intrinsic spatial resolution

Toward ultrafast high-DQE and multi-image CZT gamma-camera prospecting

Crystal Fibers and Thin Films for Imaging Applications

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