Imaging 2 - digital
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Physical basis for the CR image is the IP detector, which is made of a photostimulable phosphor (PSP) (3 steps): | show 🗑
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Two categories of flat panel DR detectors: | show 🗑
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show | indirect uses phosphor, direct uses a photoconductor.
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show | phosphor (indirect)- convert x-ray energy into electrical through an intermediate stage of light photons, photoconductors (direct) convert energy energy directly into electrical charge without the intermediate stage.
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2 types of indirect digital detectors? | show 🗑
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CCD digital detector is based on an _____ conversion process and uses a _______ to convert light to electrical signal. | show 🗑
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show | CCD
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4 main components of a CCD detector? | show 🗑
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show | captures the light, and is also an electrical charge readout device.
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show | detects x-rays and converts them into light
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An indirect flat-panel (TFT) digital detector uses several components to convert x-rays into light that is subsequently converted into electrical charges, these components are: | show 🗑
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show | cesium iodide (Csl) or gradolinium oxysulfide (Gd2O2S)
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(indirect flat panel (TFT) detectors) ______ crystals are deposited in a needle like fashion (_______ phosphor) and run in the direction of the x-ray beam. | show 🗑
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show | gradolinium oxysulfide crystals, (turbid phosphors)
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Csi crystals (______ phosphor). Gradolinium oxysulfide (_____ phosphor). | show 🗑
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show | X-ray detection of CR is inefficient and this affects image quality and dose, Spatial resolution of CR is less than FS radiography. CR IPs can easily be damaged. CR IPs must be transported to a separate image processor for image data extraction
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(flat panel DR) Selenium drum technology developed specifically for: | show 🗑
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CCD indirect digital detector order: | show 🗑
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CCD. Silicon chip is made of millions of pixels forming a matrix array of pixels. Light from the _____ falls upon each pixel to produce __________ (charges) in direct proportion to the amount of light falling upon them. | show 🗑
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CCD. Bucket brigade? | show 🗑
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CCD. What happens after the bucket brigade? | show 🗑
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show | powdered. (this is why structured phosphor like Csi crystals are better)
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show | thin-film transistor
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Indirect flat panel TFT detectors: following the x-ray scintillator (x-ray detection medium) is what? | show 🗑
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Indirect flat panel TFT detectors: a-Si photodiode layer is for what? | show 🗑
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show | collect and store the electrical charge produced in the a-Si photodiode array.
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show | scintillator phosphor such as CsI, a-Se photoconductor to convert x-rays directly
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Indirect TFT: the purpose of the a-Si photodiode layer is ? | show 🗑
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show | To collect and store the electrical charge produced in the a-Si photodiode array.
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show | amorphous selenium (a-Se)
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show | detects x-ray photons from the patient and converts them directly into electrical charges.
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Flat panel TFT: What is the matrix or active matrix array-whats it consist of? | show 🗑
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Flat panel TFT: each pixel contains what 3 things? | show 🗑
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show | x-ray photons passing through the patient. (since there isnt a CsI scintillator?)
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show | photodiode, storage capacitor.
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The ______________ of the pixel receives the data from the layer above it that captures x-rays that are converted to light (indirect) or electrical charges (direct). | show 🗑
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show | defined as the ratio of sensing area of the pixel to the area of the pixel itself
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Fill factor is expressed how? | show 🗑
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Fill factor affects what 2 things? | show 🗑
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show | high, large
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show | photodiode, to produce electrical charges. Photoconductor, directly into electrical charges.
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show | atomic number (Z#), density, and thickness of attenuating material.
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show | CsI and Gd2O2S (gradolinium)
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General operating principles/steps of indirect TFT? | show 🗑
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General operating principles/steps of direct TFT? | show 🗑
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Before the flat panel detector can be used, it must be prepared. This is referred to as __________. | show 🗑
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What is exposure latitude? | show 🗑
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EI does or does not represent an equivalent for patient dose entrance exposure? | show 🗑
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show | "for processing" image.
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show | post processing, "for presentation" image.
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show | post
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show | flat-field image.
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show | the exposure falling on the detector.
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Third step in image processing is ___________, where the adjusted or scaled raw data values are mapped to the "for presentation" values to display an optimum image. | show 🗑
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"processing optimization rules" are what | show 🗑
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the ability of the imaging system to resolve fine details present in an object is called | show 🗑
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3 tests to measure spatial resolution? | show 🗑
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What is the modulation transfer function? *** | show 🗑
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show | 1
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High frequencies contain _____, low frequencies contain ______. | show 🗑
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A system that has a higher spatial frequency at an MTF of .1 will show _____ spatial resolution than a system with below MTF of .1. | show 🗑
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show | contrast resolution
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Dynamic range of a digital detector is what | show 🗑
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What is DQE? | show 🗑
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show | high
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show | DQE= SNR 2out / SNR 2in
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A perfect digital detector would have a DQE of __. | show 🗑
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show | decreases rapidly
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Image lag is aka | show 🗑
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Image lag refers to: | show 🗑
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