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Nuclear Medicine > Instrumentation > Flashcards

Instrumentation Flashcards

1
Q

Instruments are designed for what?

A

DESIGNED TO DETECT RADIATION OR TO MEASURE RADIATION, OR TO DO BOTH.

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2
Q

4 Types Instruments

A

PULSE MODE – THE PRESENCE OF RADIATION IS INDICATED BY A TICKING, CHIRPING, OR BEEPING SOUND.

RATE MODE – THE INSTRUMENT RESPONE IS EXPRESSED IN MILLIROENTGEN PER HOUR OR ROENTGEN PER HOUR.

INTEGRATE MODE – USUALLY INSTRUMENTS
ARE DESIGNED TO MEASURE THE INTENSITY OF
RADIATION. THEY ACCUMULATE THE SIGNAL
AND RESPOND WITH A TOTAL EXPOSURE. SUCH
APPLICATION IS CALLED “DOSIMETRY”.

Dosimeters – are radiation measuring devices

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3
Q

As radiation passes through gas, it ionizes atoms of the gas. The electrons released in ionization are detected as an electrical signal that is proportional to the radiation intensity.

A

Gas-Filled Detectors

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4
Q

Most familiar type of ion chambers.

This is used principally for area radiation surveys.

How much can it detect?

A

PORTABLE ION CHAMBER SURVEY INSTRUMENT

10 μGy (1mR/hr) to several thousand
Gy/hr (R/hr)

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5
Q

3 Types of Gas Filled Detectors

A

1.) Ionization Chambers
2.) Proportional Counters
3.) Geiger-Muller Detectors

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6
Q

What is RI and P in gas filled detectors?

A

R - Region of Combination

I - Ionized Region

P - Proportional Regions ( Create Secondaty Electrons)

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7
Q

Used in Nuclear Medicine to measure or assay accurately quantities of radioactive material.

Unit: MegaBecquerel (MBq) and millicurie (mCi)

  • Remember: 1 mCi = 37 MBq
  • QAQC: Daily Constancy and Reproducibilty
A

Dose Calibrator

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8
Q

Sensitive instruments that are used primarily as stationary laboratory instruments for the assay of small quantities of radioactivity

A

Proportional Counters

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9
Q

It is the ideal gas-filled chamber and this is the
region in which Geiger Counters operate

A

G-M Region

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10
Q

In _____ , _______ introduced the first successful detector of individual alpha particles

A

1908, Geiger

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11
Q

Introduction in __________ of the __________________ marked the introduction of modern electrical devices into radiation research.

A

July 1928 of the Geiger-Müller Counter

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12
Q

Types of GM Counter

A

Survey Meter and Contamination Meter

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13
Q

CD?

A

Region of Continous Discharge

In this condition of continuous discharge, the
instrument is useless for the detection of
radiation, and continued operation in this region

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14
Q

It is the basis for the Gamma Camera in Nuclear Medicine
, detector arrays of CT Imaging Systems, and Image Receptor
of several types of Digital Imaging System

A

SCINTILLATION DETECTORS

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15
Q

TYPES OF SCINTILLATION DETECTORS

They can also be used to measure radiation the _____ or _________

A

SOLID, LIQUID, NOBLE GAS, LIQUID SCINTILLATION and GAS

Rate Mode or Integration Mode

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16
Q

Can be made to respond to radiation by
scintillation. This is rare because the detection efficiency is very low and the probability of interaction therefore is small

A

NOBLE GAS

17
Q

Used frequently in research laboratory to detect low-energy beta emiissions from Carbon-14 ( 14C) and Tritium ( 3H). Nearly 100% detection efficiency for beta radiation.

A

LIQUID SCINTILLATION

18
Q

Most widely used scintillation phosphors; have been incorporated into CT Imaging system detector array

A

INORGANIC CRYSTALS

19
Q

Incorporated in gamma cameras

A

NaI:Tl

20
Q

Incorporated into Image-Intensifier Tube’s
Input Phosphor and into flat panel digital radiography.

A

Cs:Tl

21
Q

Modern scintillation detector materials used in CT Imaging System

A

Cadmium Tungstate

22
Q

Light produced during scintillation is emitted
_________

A

Isotopically

23
Q

A __________ is one that prevents the crystal from coming into contact with air or moisture.

A

Hermetic seal

24
Q

Is an electron vacuum tube that contains a number of elements. The tube consists of a glass envelope, which provides structural support for the internal elements and
maintains the vacuum inside the tub

A

PHOTOMULTIPLIER TUBE (PM TUBE)

25
Q

Through this application, unknown gamma
emitters can be identified and more sensitive
radioisotope imaging can be accomplished by
counting only those pulses with energy that
represents total gamma ray absorption.

A

PULSE HEIGHT ANALYSIS

26
Q

OCCUPATIONAL RADIATION MONITORING

A

It is required when there is any likelihood that an individual will receive more than 1/10 of the recommended dose limit.

27
Q

ACTIVE DOSIMETERS

A

Used in a hazardous environment, such as a nuclear reactor or other places with a high chance at higher radiation levels.

Designed to let the wearer know how much
radiation they have been exposed and are
often equipped with a notification feature to
let you know when you are approaching a
pre-set limit of radiation exposure.

Instruments – Electronic Personal Dosimeters (EPD) and Pen Dosimeters

28
Q

PASSIVE DOSIMETERS

A

Used when you are exposed to only low
radiation levels, or only occasionally
exposed to radiation.

It records the amount of radiation over
time but is not analyzed in real-time.

Used in hospitals by personnel who are
exposed to low level of radiation.

Used also by miners.

29
Q

Film Badge

A
  • It is similar to dental radiographic film and sandwhiched
    between metal filters inside a plastic holder.

*Two metal filters: Aluminum and Copper – it allows estimation of the x-ray energy.

  • The optical density on the exposed and processed film is
    related to the exposure received.
  • Carefully controlled calibration, processing, and analyzing
    conditions are necessary for it be measured accurately.
  • ADVANTAGES: Inexpensive, Easy to handle, easy to process, and reasonably accurate.
  • DISADVANTAGES: It can’t read exposures less than 10 mR, It cannot be reused, It can’t be worn for longer than 1 month because of possible fogging caused by temperature and humidity.
30
Q

THERMOLUMINISCENT DOSIMETER (TLD)

A

Uses LITHIUM FLUORIDE (LiF) with Z=8 in a crystalline form.

  • When exposed to x-rays, the TLD absorbs energy and stores it in the form of excited electrons.
  • When HEATED, these excited electrons fall back to their normal state with the emission of visible light.
  • The intensity of visible light is measured with a Photomultiplier Tube (PMT) or Photodiode and is proportional to the radiation dose received
    by the crystal.
  • 1960s, Cameron and coworkers at the University of Wisconsin experimented with some thermoluminiscent materials and were able
    to show that exposure to ionizing radiation caused some materials to
    glow particulary brightly when subsequent heated.
  • ADVANTAGES: It is more sensitive and accurate than Film Badge, It can measure as low as 5 mR, and It can be worn for intervals up to 1 year.
  • DISADVANTAGE: Expensive than Film Badge.
31
Q

OPTICALLY STIMULATED LUMINISCENCE (OSL)

A
  • This is worn and handled just as film badges and TLDs and approx. same size.
  • Light is emitted when an OSL crystal is illuminated.
  • Developed by Landauer (1990s).
  • It uses Aluminum Oxide.
  • Irradiation of Aluminum Oxide stimulates some electrons
    into an excited state. During processing, laser light stimulates these electrons, causing them to return to their
    ground state with the emission of visible light.
  • One Advantage over TLD: It can measure as low as 1 mR.
  • Disadvantage: Expensive than TLDs and Film Badge

Nuclear Medicine (9 decks)

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