Lesson 4 Flashcards

1
Q

presence of radiation is indicated by
ticking, chirping or beeping sound

A

PULSE MODE

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2
Q

the instrument response is
expressed in mR/hr or R/hr

A

RATE MODE

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3
Q
  • Used in instruments designed to
    measure the intensity of
    radiation
  • Accumulate the signal and
    respond with a total exposure
    (mGya or Gya)
A

INTEGRATED MODE

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4
Q
  • mGya or Gya
  • The practice of measuring the
    intensity of radiation
A

DOSIMETRY

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5
Q
  • Instrument designed to detect and
    measure radiation
  • The radiation-measuring devices
A

DOSIMETERS

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6
Q
  • The earliest radiation detection
    device
  • The primary means of radiation
    detection and measurement
  • Limited range, sensitive, and
    energy-dependent
  • Personnel monitoring
  • Emulsion reading
A

PHOTOGRAPHIC EMULSION

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7
Q

TWOPRINCIPAL APPLICATIONS
OF FILM:

A
  • The making of a radiograph
  • The radiation monitoring of
    personnel (film badge)
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8
Q
  • 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)
A

GAS-FILLED RADIATION
DETECTOR

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9
Q
  • Used widely as a device to
    measure radiation intensity
  • Used to detect radioactive
    contamination
A

GAS-FILLED RADIATION
DETECTOR

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10
Q

THREE TYPES OF GAS-FILLED RADIATION
DETECTOR

A
  • IONIZATION CHAMBER
  • PROPORTIONAL COUNTERS
  • GEIGER-MULLER COUNTER
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11
Q
  • Has more molecules available for
    ionization
  • more sensitive
A

LARGE CHAMBERS

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12
Q

The instrument of choice for
measuring radiation intensity

A

IONIZATION CHAMBER

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13
Q
  • Survey for radiation levels mR/hr–
  • Portable survey instrument
  • Dose Calibrator
  • Ion chamber dosimeter
A

IONIZATION CHAMBER

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14
Q
  • A portable ion chamber survey
    instrument
  • The most familiar
A

PORTABLE SURVEY INSTRUMENT
(CUTIE PIE)

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15
Q
  • A configuration of an ion chamber
  • Another application of precision
    ion chamber
A

DOSECALIBRATOR

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16
Q
  • Most accurate ion chamber (specific
    measurement output intensity)
  • used for precise calibration of
    the output intensity of diagnostic x-ray
    imaging systems
A

ION CHAMBER DOSIMETER

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17
Q
  • Sensitive instruments
  • Detect only Alpha and Beta
    radiation
A

ION CHAMBER DOSIMETER

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18
Q
  • A sensitive portable survey
    instrument
  • Capable of detecting and
    indicating SINGLE IONIZING
    EVENTS
  • Least likely to be used as x-ray
    detector
A

GEIGER-MULLER COUNTER

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19
Q
  • is the emission of light by a thermally
    stimulated crystal following irradiation
  • When heated, it emits visible light
A

THERMOLUMINESCENCE
DOSIMETRY (TLD)

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20
Q

BASIC PRINCIPLE OF TLD:

A
  • PLANCHET (SPECIAL DISK)
  • PMTUBE(photomultiplier tube)
  • TLD ANALYZER
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21
Q

where the TLD phosphor is placed on

A

PLANCHET (SPECIAL DISK)

22
Q

light sensitive and light measuring
vacuum tube (convert photons into
electric signal)

A

PM TUBE (photomultiplier tube)

23
Q

electronic instruments designed to
measure and analyze radiation and
automatically relate this to exposure or
dose through a conversion factor

A

TLD ANALYZER

24
Q
  • 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)
A

LITHIUM FLUORIDE (LiF)

25
- more sensitive to ionizing radiation can measure doses: less than - 1 mrad (moderate accuracy)
CALCIUM FLUORIDE (activated with manganese) (CaF2:Mn)
26
- OSL monitors the amount of radiation received by the amount of light emitted - Radiation dosimeter adapted for personnel monitoring (newest) - Used for both patient and personnel radiation monitoring
OPTICALLY STIMULATED LUMINESCENCE DOSIMETRY (OSL)
27
OSL MULTISTEP PROCESS:
- Exposure to ionizing radiation (exposed) - Laser illumination (read) - Measurement of the intensity of stimulated light emission (analyzed)
28
Advantage of OSL over TLD
- More sensitive than TLD - OSL has a precision of 10Gyt
29
one who interpret and record monthly exposure records of each RT
HEALTH PHYSICIST / RADIATION SAFETY OFFICER
30
- Pack of photographic film used for approximate measurement of radiation exposure to radiation workers - Most economical type of personnel radiation monitor - Consist of a small case w/ a piece of film placed b/n different filters
FILM BADGE / FILM DOSIMETER
31
FILM BADGE / FILM DOSIMETER Filters:
- Copper - Tin - Aluminum - Plastic
32
- Sensitive devices for x-rays and gamma rays - Measures radiation intensities as low as single-photon interactions
SCINTILLATION DETECTOR
33
● Basis for the gamma camera ● Used as image receptor for several types of digital imaging system ● Used in the detectors arrays of CT imaging system Used to monitor the presence of contamination ● Used to monitor low levels of radiation
SCINTILLATION DETECTOR
34
TYPES OF SCINTILLATION DETECTOR IN STATE
● liquid ● gases ● solids
35
- An imaging device used in nuclear medicine - Also used in CT and digital radiography imaging system
GAMMA CAMERA
36
GAMMA SPECTROMETRY
- Uses scintillation detector as an energy-sensitive device - Uses pulse height analysis
37
- Nearly all noble gases - Applications are rare- detection efficiency is very low and probability of interaction is small
GAS SCINTILLATION DETECTORS
38
- Biologic molecules are mixed with a liquid scintillation phosphor - Used frequently to detect low-energy beta emission from carbon-14 and tritium - Detection: 100% for beta radiation
LIQUID SCINTILLATION DETECTORS
39
- Inorganic crystals; most widely used scintillation phosphors - Thallium-activated sodium iodide (Nal:TI) Incorporated into gamma camera - Thallium-activated cesium iodide (CsI:TI) Incorporated into image-intensifier (fluoro) tubes as the input phosphor and into flat panel DR image receptors
SOLID SCINTILLATION DETECTORS
40
● An electron vacuum tube ● Contains a number of elements ● Converts light flashes from the scintillator into an electronic signal of pulses
PHOTOMULTIPLIER (PM) TUBE
41
- Allows the light flash to be reflected internally to the window - Also necessary to seal the crystal hermetically
ALUMINUM SEAL
42
one that prevents the crystal from coming into contact with air or moisture
Hermetic seal
43
absorbs moisture NOTE: most scintillation crystals are BLANK
Hygroscopic
44
● The portion of the glass envelope that is coupled to the scintillation crystal ● Crystal window and PM tube window: sandwiched together with silicone grease ● Rationale: to provide optical coupling so that light emitted by scintillator is transmitted to the interior of the PM tube with minimum loss
WINDOW
45
● A device that emits electrons when illuminated ● (cesium, antimony, bismuth) ● Photoemission- a process wherein electrons are emitted from the photocathode
PHOTOCATHODE
46
- The first series of plate-like elements - Function: amplify the electron pulse through secondary electron emission
DYNODES
47
the ratio of secondary electrons to incident electrons
Dynode Gain
48
provides structural support for the internal elements and maintains the vacuum inside the tube
Glass envelope
49
the last plate like element of the PM tube
Collecting Electrode / Collimator
50
a structure that provides support for the glass envelope and internal structure
BASE
51
provides an initial state of pulse amplification
PREAMPLIFIER