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KEY COMPONENTS OF PET AND GAMMA CAMERA, 3 (DIFFERENCES BETWEEN THE TWO…
KEY COMPONENTS OF PET AND GAMMA CAMERA
Both cameras have
SCINTILLATOR CRYSTAL
Made of sodium iodide with trace amounts of thallium (NaI)(TI)
Absorbs γ-rays and convert into light signal
PHOTOMULTIPLIER TUBE (PMT)
Coupled to the NAL(TI) crystal via
light pipes
Size of the signal is proportional to the energy of the absorbed photon
Receive pulse of light and convert into an electron
And amplify that signal significantly so that it can be read and interpreted
HEIGHT ANALYZER
Detects the intensity of the signal, and thus the energy of the incident absorbed photons,
uses only photons from the radionuclide when forming the final image
MAIN CONCEPT
Based on the scintillation process
Using phosphor crysral and photomultiplier
To produce analog and digital signals and create an image
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DIFFERENCES BETWEEN THE TWO CAMERAS
Designs
Working principle
The use of collimator
Use collimator
Types of collimator
a. Parallel
b. Pinhole
c. Diverging
2 more items...
To improve image resolution when near
1:1 ratio between object and image
Designed to eliminate scattered photons that would degrade image
Designed as series of holes that allow (γ-rays) through inside metal honeycomb pattern
Absorbs gamma-ray (γ-rays) that do not travel parallel to the plates
improving image resolution
i. Does not require a collimator
ii. More sensitive than SPECT and higher count rate
iii. More advantageous in term of spatial resolution, statistical quality and quantitative accuracy
i. Based on the annihilation coincidence of the two photons emitted in opposite direction
ii. Two detector elements on opposite sides of the object are used to detect paired annihilation photons
i. One or more gamma camera heads mounted onto a special rotating gantry
ii. Gamma camera rotates about the patient, acquiring a projection
image at each angle
Incorporated into the SPECT imaging system
Incorporated into multiple rings detectors that surround around the patient
Gamma Camera
PET Camera
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HOW THE CAMERAS WORK ??
γ-rays that emitted from the patients are collected by the camera
γ-rays strike a scintillation crystal
Flashes of light are detected by an array of PMT
PMT capture the flash, convert to eletrons and amplify the signal.
Signals from the PMT go through an analog-to-digital converter and then to a pulse height analyzer.
Detects the intensity of the signal, and thus the energy of the incident absorbed photons,
Uses only photons from the radionuclide when forming the final image
convert photons into light signal
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