Lesson 4 Flashcards
presence of radiation is indicated by
ticking, chirping or beeping sound
PULSE MODE
the instrument response is
expressed in mR/hr or R/hr
RATE MODE
- Used in instruments designed to
measure the intensity of
radiation - Accumulate the signal and
respond with a total exposure
(mGya or Gya)
INTEGRATED MODE
- mGya or Gya
- The practice of measuring the
intensity of radiation
DOSIMETRY
- Instrument designed to detect and
measure radiation - The radiation-measuring devices
DOSIMETERS
- The earliest radiation detection
device - The primary means of radiation
detection and measurement - Limited range, sensitive, and
energy-dependent - Personnel monitoring
- Emulsion reading
PHOTOGRAPHIC EMULSION
TWOPRINCIPAL APPLICATIONS
OF FILM:
- The making of a radiograph
- The radiation monitoring of
personnel (film badge)
- Consist of a cylinder filled with air
and a central collecting electrode - Cylinder of gas- (air ) ( xenon
used to measure rays in some ct
scanners)
GAS-FILLED RADIATION
DETECTOR
- Used widely as a device to
measure radiation intensity - Used to detect radioactive
contamination
GAS-FILLED RADIATION
DETECTOR
THREE TYPES OF GAS-FILLED RADIATION
DETECTOR
- IONIZATION CHAMBER
- PROPORTIONAL COUNTERS
- GEIGER-MULLER COUNTER
- Has more molecules available for
ionization - more sensitive
LARGE CHAMBERS
The instrument of choice for
measuring radiation intensity
IONIZATION CHAMBER
- Survey for radiation levels mR/hr–
- Portable survey instrument
- Dose Calibrator
- Ion chamber dosimeter
IONIZATION CHAMBER
- A portable ion chamber survey
instrument - The most familiar
PORTABLE SURVEY INSTRUMENT
(CUTIE PIE)
- A configuration of an ion chamber
- Another application of precision
ion chamber
DOSECALIBRATOR
- Most accurate ion chamber (specific
measurement output intensity) - used for precise calibration of
the output intensity of diagnostic x-ray
imaging systems
ION CHAMBER DOSIMETER
- Sensitive instruments
- Detect only Alpha and Beta
radiation
ION CHAMBER DOSIMETER
- A sensitive portable survey
instrument - Capable of detecting and
indicating SINGLE IONIZING
EVENTS - Least likely to be used as x-ray
detector
GEIGER-MULLER COUNTER
- is the emission of light by a thermally
stimulated crystal following irradiation - When heated, it emits visible light
THERMOLUMINESCENCE
DOSIMETRY (TLD)
BASIC PRINCIPLE OF TLD:
- PLANCHET (SPECIAL DISK)
- PMTUBE(photomultiplier tube)
- TLD ANALYZER
where the TLD phosphor is placed on
PLANCHET (SPECIAL DISK)
light sensitive and light measuring
vacuum tube (convert photons into
electric signal)
PM TUBE (photomultiplier tube)
electronic instruments designed to
measure and analyze radiation and
automatically relate this to exposure or
dose through a conversion factor
TLD ANALYZER
- most widely used TLD material
- Effective atomic no. of 8.2; which has photon absorption properties similar to that of soft tissue (nearly a tissue equivalent dosimeter)
LITHIUM FLUORIDE (LiF)