Acquisition System

Is Photostimulable Phosphor Plate (PSP) direct or indirect?

Indirect

Photostimulable Phosphor Plate Layers

• Protective layer

• Phosphor layer

• Support layer

What does PSP phosphor layer contain?

Barium fluorohalide with europium

What do barium fluorohalide and europium do?

• Absorbs x-rays

• Traps electrons

respectively

Slow scan

Direction plate moves along roller system

Fast scan

direction helium neon red laser scans the plate perpendicular to direction of travel

What determines the pixel size in the scanning assembly

Sampling frequency of the laser

A thin film transistor array is present in what kind of detector?

Direct and indirect flat panel detector

What are the square cells of a thin film transistor array called? What does the acronym stand for?

• DEL

• Detector element

What are the components of a DEL? What does each component do?

• Active area/active layer (captures image)

• Electrical components (image data storage & release)

What is the composition and function of the direct FPD active layer?

• made of amorphus selenium (absorbs x-rays and coverts them into electrons)

What additional layer does an indirect FPD have?

Scintillator layer

What is the composition and function of the indirect FPD scintillator layer?

made of cesium iodide or gadolinium oxysulfide (absorbs x-rays and converts them into light)

What is the composition and function of the indirect FPD active layer?

Made of amorphous silicon (absorbs light and converts it the electrons)

What are the pieces of electrical components in both direct and indirect FPD electrical components?

• Capacitor (stores electrons)

• Thin film transistor (signal readout)

What is the difference between a scintillator layer composed a cesium iodide vs gadolinium oxysulfide?

• Cesium iodide: columnar structure that acts like micro-fiber optic tunnels

• Gadolinium Oxysulfide: turbid structure that causes the light to scatter

• CsI produces better spatial resolution and GadOx has a more lateral spread

Charges Coupled Devices are used in direct or indirect detectors? What do they need to accompany them?

• Indirect detector

• Scintillator layer

What are the two methods a scintillator converts x-rays into light?

• Lens-coupled

• Fiberoptic-coupled

What are the individual cells in a CCD called? What components do they contain?

Pixels

• Active layer (image acquisition and storage of electrons)

• Electrical component (Image data release)

What is the composition and function of the active layer in a CCD?

Made of silicon (absorbs light, converts light into electrons, stores electrons)

What is the composition and function of the electrical component in a CCD?

Made of polysilicon (charge readout)

What method does CCD use to extract data?

Bucket Brigade: top row empties into readout register, succeeding rows follow with charges moves verticallly then horizontally

What does CMOS stand for? What is its function?

Complementary Metal-Oxide Semiconductor

• Captures x-rays

How is CMOS different that a CCD?

• Uses less power than CCD to operate

• Tend to be less expensive

• Pixels read out individually

What mechanism is use to convert data?

Analog to Digital Converter

What are an ADCs two functions?

• Sampling: extracts data points from the analog signal

• Quantization: measures electrical signals and assigns discrete numericla values to them

  • Values are based on bit depth