Prelim Topic 2 Flashcards
Basic process of nucmed
Injection of radiopharmaceutical
Pharmaceutical carries the radionuclide to the
organ being examined.
The target organ is localized.
Radionuclide in the target organ emits gamma
rays.
Gamma camera detects the gamma rays to
create a digital image.
Imaging procedures - referred to as
scanning scintigraphy
is the nuclear medicine laboratory technique for measuring trace amount of substances in the blood. (substances being measured with RIA are the least 1000 times less)
Radioimmunoassay (RIA)
In “ __ “ - in the living subject
Vivo
for brain, liver, lung, bone, kidney, heart, thyroid, and other organs for detection of a tumor. Whole body imaging for the detection of metastases.
Imaging studies
are thyroid uptake to determine thyroid function, renography for the investigation renal function, and blood volume measurement.
Non-imaging studies
Therapeutic Procedure -treatment of
Hyperthyroidism with I-131
In “ __ “ - in a glass
Vitro
measurement of hormones, enzymes, and other substances.
Radioimmunoassay
uses a __ of radioactive material (unsealed source)
small amount
Unsealed means?
Open
Uniqueness of Nuclear Medicine is that it
evaluates the __ of the organ
function
Two classes of nucmed imaging
Single photon imaging, positron imaging
includes Single Photon emission Computed tomography (SPECT), Uses radionuclides that decay by gamma emission
Single photon imaging
Includes Positron Emission Tomography (PET) Uses radionuclide that decay by positron emission
Positron Imaging
Two main categories of detectors
Gas filled detectors, scintillation detectors
Those that depend on ionization in which ionization is translated into electric current or impulses.
Gas filled detectors
those that depend on excitation.
Scintillation detectors
Radiation is sensed by
Detecting ionization of gas
The use of an ionization chamber. The generic design concept is a gas-filled chamber with __ and __ electrodes,
positive, negative
placed either at opposite sides of the chamber. A __ is created between two electrodes, but __ in the absence of exposure of the chamber to radiation.
potential difference, no current flows
3 types of gas filled detectors
Proportional counter, ionization chamber, geiger-muller counter
Are very sensitive type of personnel monitoring device Provides an instantaneous reading, but must be recalibrated daily Resembles a fountain pen Inside the dosimeter is an ionization chamber Normally used only in emergency situation immediate reading is necessary
Pocket dosimeter, pen dosimeter
Used to determine the amount of radioactivity in syringes or vials, Device that is used to measure, Radioactivity before Injecting to the Patient
Dose calibrator
The main difference between a __ and basic ionization chamber is greater applied voltage between electrodes Proportional chambers do not have wide application in clinical nuclear medicine. They are used in research In detection alpha and beta particles. useful is their ability to distinguish between alpha and beta radiation.
Proportional counters
an instrument for detecting and measuring the intensity of ionizing radiation Used as a survey meter __ counter is used for contamination control in nuclear medicine laboratories. They are not particularly useful as dosimeters
Geiger-muller
When ionizing particles pass through certain crystals, flashes of light or scintillation is emitted. The amount of light emitted is proportional to the amount of energy absorbed by the material. This type of detector is the most commonly used detector in nuclear medicine.
Scintillation detectors
The output signal form accumulated charge in radiation detectors is typically quite low
Pre-amplifier
- To amplify, if necessary, small signals from detectors
- To shape signals for remaining signal processing
main purposes of the preamplifier (or preamp):
The output signal form the preamplifier can still be quite low for traditional electronics in signal processing chain
Amplifier
- To amplify, the still relatively small pulses from the preamplifier
- To reshape the long signals from the preamplifier to minimize pulse-pileup at high
count rates and improve SNR
Main purpose of amplifier
• Is an electronic device used to determine which portion of the detected spectrum is used to create images.
• The PHA can be set to allow only selected energies to be
counted, and reduce the number of Compton scatter photons in the image.
• The PHA allows the operator either to set the upper and lower energy limits or to set a peak energy level and associated window.
Pulse height analyzer
Types of collimator
Pinhole Collimator
• Parallel hole Collimator
• Converging Multihole Collimator
• Diverging Multihole Collimator
HIGHEST RESOLUTION, This type of collimator provides the best spatial resolution and the lowest sensitivity of any collimator used in nuclear medicine, USED IN THROID SCANS
Pinhole collimator
Spatial Resolution: determined by the collimator
a. Diameter of aperture
b. Distance from both of the object
c. NaI crystal aperture
No magnification occurs with this type of collimator
Hole Diameter: 1mm
Hole length: 20 mm
MOST COMMON TYPE OF COLLIMATOR
Parallel hole collimator
Provides both enhanced spatial resolution and improved sensitivity. Used for imaging smaller objects (similar to pinhole) using a camera with a large FOV. Used to achieve magnified image with slightly improved spatial resolution.
Converging collimator
3 parts of PMT
photocathode, dynode, anode (collecting anode)
