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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| show | Indirect TFT and direct TFT.
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| show | indirect uses phosphor, direct uses a photoconductor.
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| Systems that use phosphor (indirect detectors) and systems that use photoconductors (direct) differ by converting x-rays to electrical how? | show 🗑
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| show | charged coupling device (CCD) digital detector, and the flat-panel thin film transistor (TFT) digital detector. (difference between them is technical factors on how to convert light to electrical)
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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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| Which detector is not classified as a flat-panel digital detector but is available commercially? | show 🗑
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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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| show | x-ray scintillator (conversion layer usually cesium iodide or gradolinium), an amorphous silicon (a-Si) photodiode flat panel layer, with a thin-film transistor (TFT) (for reader of the electrical charges by the photodiode)
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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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| show | Csi- structured, Gradolinium- turbid
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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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| show | x-ray, scintillator- light, lens or fiber optic, CCD - electrical charge
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| show | scintillator, produce electron-hole pairs.
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| CCD. Bucket brigade? | show 🗑
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| show | The charge pattern from the readout of pixels (from the light of the scintillator falling on each pixel that produced electron-hole pairs...) is sent to the ADC for digitization. Then sent to computer for processing.
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| show | powdered. (this is why structured phosphor like Csi crystals are better)
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| TFT stands for? | show 🗑
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| show | an a-Si photodiode flat-panel layer
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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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| *** indirect detectors use a light sensitive photodiode to capture light from the ___________ phosphor such as _____ to produce electrical charges, the direct detectors use an ____ photoconductor to convert x-rays _____ into electrical charges. | show 🗑
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| show | To convert th elight from the x-ray detection scintillator into electrical charges.
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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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| show | consists of rows and columns that play a role in addressing and readout of the signal from each pixel.
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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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| show | sensing area
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| Fill factor is what? | show 🗑
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| Fill factor is expressed how? | show 🗑
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| show | spatial resolution and contrast resolution (detail and signal-to-noise)
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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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| X-ray scintillators are what for indirect flat panel TFTs? | show 🗑
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| show | utilize a scintillator layer such as CsI to convert photons into light, these light photons strike the a-Si photodiode, which converts them to electrical charges.
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| show | photons fall upon the a-Se photoconductor layered on top of a matrix of a a-Si TFT array. As xrays strike the a-Se, electral charges are created and the electrical field causes them to move towards the TFT elements where they are collected and stored.
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| show | initialization.
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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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| After the image is presented as "for processing" image, it then undergoes digital image _____________, and the resultant image is labeled a _________________ image. | show 🗑
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| ____ processing improves contrast/appearance for the radiologist. | show 🗑
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| Image obtained initially from the detector is referred to as what? | show 🗑
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| You base scaling the histogram on what? | show 🗑
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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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| show | bar test pattern, sharp-edged object, narrow slit.
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| show | math function that measures the ability of the detector to transfer its spatial resolution characteristics to the image.
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| An MTF of ____ represents a perfect detector. | show 🗑
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| High frequencies contain _____, low frequencies contain ______. | show 🗑
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| show | better
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| High MTF value at lower spatial frequencies means that the detector provides better _____. | show 🗑
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| show | the response of the detector to different levels of radiation exosure
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| What is DQE? | show 🗑
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| show | high
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| DQE can be expressed as : | show 🗑
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| show | 1
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| As the spatial frequencies increase, the DQE ______ | show 🗑
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| Image lag is aka | show 🗑
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| Image lag refers to: | show 🗑
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