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Questions and Answers
What is the function of the Cesium Iodide (CsI) layer in a flat panel detector?
How is the charge from X-rays transmitted in a flat panel detector?
What differentiates Direct Radiography from cassette-based systems?
What allows Direct Radiography to have faster image processing?
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What component is essential for converting an analog signal to digital in Direct Radiography?
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Which technology does not involve imaging plates or removable hardware?
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What happens when x-rays hit CdTe in the process described?
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What materials are used as photo conductors in fat panel detectors?
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Which of the following describes the direct conversion process?
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What helps in achieving a sharper image in the direct conversion process?
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Which material does flat-panel a-Se detectors use compared to a-Si detectors?
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Why is flat-panel a-Se technology considered more efficient?
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What is the main function of the scintillator layer in indirect conversion flat panel detectors?
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Which material is NOT associated with direct conversion in flat panel detectors?
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Why is pure silicon not used alone in direct conversion detectors?
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What does digital radiography (DR) use to capture data during object examination?
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In indirect conversion, what is the proportional relationship that the generated electrical charge represents?
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How is the incident x-ray radiation converted in digital radiography (DR)?
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What is another name for flat panel detectors used in DR?
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Which of the following statements about cesium iodide (CsI) in direct conversion is correct?
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What characteristic of CsI helps reduce the scattering of light in direct conversion detectors?
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Which feature of flat panel detectors provides high sensitivity for radiographic applications?
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What is an advantage of using flat panel detectors in digital radiography?
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What does direct radiography eliminate the need for?
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Which component is used in direct radiography to turn X-rays into an electrical charge?
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What type of detector does direct radiography use?
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What is one advantage of direct radiography over computed radiography?
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How does a direct conversion flat panel detector work in direct radiography?
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What does TFT in direct radiography stand for?
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Which process is eliminated by using TFT in direct radiography?
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In what field was direct radiography first adopted?
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Study Notes
Digital Radiography (DR)
- Advanced form of x-ray inspection that produces a digital radiographic image instantly on a computer
- Uses x-ray sensitive plates to capture data during object examination
- Incident x-ray radiation is converted into an equivalent electric charge and then to a digital image through a detector sensor
Flat Panel Detectors
- Provide high-quality digital images with better signal-to-noise ratio and improved dynamic range
- Work on two different approaches: indirect conversion and direct conversion
Indirect Conversion
- Flat panel detectors have a scintillator layer that converts x-ray photons to photons of visible light
- Utilize a photo diode matrix of amorphous silicon to convert light photons into an electrical charge
- Charge is proportional to the number and energy of x-ray photons interacting with the detector pixel and the amount and density of material that has absorbed the x-rays
Direct Conversion
- Silicon alone is not sensitive enough to the energy of x-ray quanta used in diagnostic radiology
- Therefore, the silicon layer is covered with a scintillator material, cesium iodide (CsI) known as intensifying screens
- CsI absorbs the X-ray quanta and transfers them to light, which is detected by the a-Si, converting light to electrical charge
The Process
- X-rays hit CsI or CdTe
- Light hits a-Si
- Electrons and holes are drawn toward the positive bias, and holes are stored in the charge storage wells beneath the electrodes
- When enough charge is stored, a voltage runs across the a-Si, and the electronics read this voltage
Fat Panel Detectors
- Use photo conductors like amorphous Si, CdSe, or Copper Telluride (CdTe) on a multi-micro electrode plate
- Providing the product charge, information on both types of detectors read for thin film transistors
The Direct Conversion Process
- When x-ray photons impact the photo conductor (amorphous Selenium), they are directly converted to electronic signals, which are amplified and digitized
- Thus, there is no scintillator lateral spread of light photons, ensuring a sharper image
Flat-panel: a-Se
- Uses selenium instead of silicon
- No need for Cesium Iodide (CsI) layer
- A more direct technology
- More efficient and electric bits are avoiding shadow minimum as electrons build in a field
- More expensive but has good spatial resolution and is more efficient than the a-Si detectors
Direct Digital Radiographic Receptor
- DR Image Converter
- Directly converts X-ray to an electrical signal
- X-rays hit the detector where pixels are arranged in a matrix
- These pixels each hold a charge that depends on the intensity of the X-ray
- This charge gets converted into an electrical signal
- An analog to digital converter converts the signal into information that the computer can process
Direct Radiography
- A type of digital radiography like CR, but is more digital in the sense that there is no cassette, removable imaging hardware or equipment that physically reads the imaging plates
- Has digital imaging sensors built into the x-ray table or equipment to the system, meaning that the images are captured directly onto the digital system, allowing for faster image processing and reduced costs
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Description
Test your knowledge of Digital Radiography, a digital x-ray inspection technique that produces instant digital images. Learn about x-ray sensitive plates, detector sensors and more.
