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Mid Flashcards

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1
Q

What are instruments designed to detect or measure radiation called?

A

Radiation detection instruments

These instruments generally operate in pulse or rate mode.

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2
Q

What mode indicates radiation with ticking, chirping, or beeping?

A

Pulse mode

This mode provides audible signals in response to detected radiation.

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3
Q

In rate mode, how is the instrument’s response measured?

A

mR/hr or R/hr

This indicates the rate of radiation exposure.

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4
Q

What is the purpose of dosimetry instruments?

A

To measure the intensity of radiation

They typically operate in integrate mode, accumulating total exposure.

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5
Q

What are dosimetry measuring devices called?

A

Dosimeters

These devices measure radiation exposure over time.

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6
Q

What was the earliest radiation detection device?

A

Photographic emulsion

It is still widely used for radiation detection measurements.

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7
Q

What are the two principal applications of film in diagnostic imaging?

A
  • Making a radiograph
  • Personnel radiation monitor (film badge)

Film plays a critical role in both imaging and monitoring radiation exposure.

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8
Q

What happens as radiation passes through gas in gas-filled detectors?

A

It ionizes atoms of gas

Electrons released during ionization are detected as a signal proportional to radiation intensity.

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9
Q

What is an example of a gas-filled detector that is also known as a survey meter?

A

Ionization chamber

This is the most common type of gas-filled detector.

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10
Q

What are proportional counters useful for?

A

Detecting the difference between alpha and beta radiation

These counters are sensitive instruments used in laboratory settings.

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11
Q

What is the function of Geiger-Muller counters?

A

Detecting impurities, especially in nuclear medicine facilities

They are widely used for general radiation detection.

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12
Q

What is a quenching agent in the context of Geiger-Muller counters?

A

A substance added to the filling gas to restore the counter’s original condition

Xenon is a common quenching agent used.

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13
Q

What occurs in scintillation detectors?

A

A flash of light is emitted from the absorption of ionizing radiation

The amount of light emitted is proportional to the energy absorbed.

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14
Q

What is a Thermo Luminescent Dosimeter (TLD)?

A

Most accurate scintillation detector that uses lithium fluoride (LiF) and can measure as low as 10 mrad to 10 rad.

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15
Q

What is an Optically Stimulated Luminescence (OSL) dosimeter?

A

Most sensitive scintillation detector that uses aluminum oxide and can measure as low as 1 mrad.

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16
Q

What is a Pocket Dosimeter?

A

Provides immediate reading, also known as pen dosimeter, and can measure 0-200 mR.

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17
Q

What is a Film Badge?

A

Least accurate dosimeter that can measure doses greater than 10 mR.

Common causes of film fog include temperature, humidity, and more than 1 month of use.

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18
Q

What are the two types of Radionuclide Production?

A

Natural - nuclear reactions that occur spontaneously with relatively long half-lives and heavy toxic elements. Artificial - produced by particle bombardment or electromagnetic irradiation.

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19
Q

What is a Radionuclide Generator?

A

Units that contain a radioactive parent nuclide with relatively long half-life that decays to a short-lived daughter nuclide.

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20
Q

How is Mo-99 produced?

A

Mo-99 is produced by the fission of U-235 (fission moly), chemically purified, and passed on to an anion exchange column composed of alumina (Al2O3).

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21
Q

How is To-99m obtained from the generator?

A

To-99m is milked or eluted by drawing sterile saline through the column in a vacuum vial.

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22
Q

What are some other examples of radionuclide generators?

A
  1. Tin-110 - Indium 110 generator 2. Strontium 82 - Rubidium-82 generator (cardiac PET) 3. Germanium 82 - Gallium-82 generator (Neuroendocrine PET)
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23
Q

What is a cyclotron?

A

A circular device in which charged particles such as protons and alpha particles are accelerated in a spiral path in a vacuum.

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24
Q

What are the components of a cyclotron?

A
  1. Dees - two halves of the circle where the proton is accelerated.
  2. Electric Field - accelerates proton by providing high kinetic energy.
  3. Magnetic Field - responsible for steering the protons in spiral motion.
  4. Deflector - directs the particles out through a window in the cyclotron to strike the target.
  5. Target - material to be bombarded by the proton, ejecting 2 neutrons from the nucleus after bombardment.
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25
What is a reactor?
Composed of fuel rods that are inherently unstable (uranium) which undergo fission, releasing 2-3 fast neutrons and 200MeV heat.
26
What is the role of a moderator in a reactor?
Slows fast neutrons making them thermal neutrons.
27
What are cadmium control rods?
They absorb neutrons in the reactor, controlling the speed of the reaction.
28
What are the two means of production in nuclear reactions?
Fission and neutron capture.
29
What are the characteristics of an ideal radionuclide?
• Pure gamma emitter - no particulate radiation. • Sufficient photon energy - 100-300keV for attenuation and detection. • Minutes to hours half-life. • HVL should be around organ dimension. • Monoenergetic.
30
What is TC-99m?
A radionuclide discovered in 1937 by Carlo Perrier and Emilio Serge from a sample of Mo-98 irradiated by neutrons and deuterons. ## Footnote Half-life 6 hours, Energy 140 keV (98.6%), Pure gamma emitter, Metastable - excited state of nucleus with measurable lifetime.
31
What is radionuclidic purity?
The fraction of total activity in the form of the desired radionuclide. For Tc-99m generator, there should be less Mo-99 in the eluate. ## Footnote STANDARD: <0.5 uCi Mo-99/mCi Tc-99m
32
What is chemical purity?
The fraction of wanted vs unwanted chemicals in the preparation, ensuring low presence of AI203 in the eluate. ## Footnote STANDARD: <10ug/ml (Aurintricarboxylic acid is used for colorimetric spot testing)
33
What is radiochemical purity?
The fraction of total radioactivity in the desired chemical form, ensuring that the expected valence state is +7. ## Footnote STANDARD: 95% of Tc-99m in +7 valence state.
34
What are radiopharmaceuticals?
Combination of radionuclide (detection) and pharmaceutical (carrier). ## Footnote They portray physiology, biochemistry, or pathology in the body and are also called radiotracers.
35
What is the localization mechanism in radiopharmaceuticals?
It includes various mechanisms such as active transport, compartmental localization, diffusion, phagocytosis, capillary blockade, and cell sequestration.
36
What is an example of active transport in radiopharmaceuticals?
Thyroid uptake scanning with iodine. ## Footnote This mechanism actively transports the radiopharmaceutical into the thyroid.
37
What is compartmental localization?
Blood pool scanning with human serum albumin or RBC. ## Footnote This method localizes the radiopharmaceutical within the blood pool.
38
What is diffusion in the context of radiopharmaceuticals?
Bone scanning using diphosphonates. ## Footnote This mechanism allows the radiopharmaceutical to diffuse into the bone.
39
What is phagocytosis in radiopharmaceutical imaging?
Radicoloids imaging of spleen, liver, and bone marrow. ## Footnote This mechanism involves the uptake of the radiopharmaceutical by phagocytic cells.
40
What is capillary blockade?
Lung scan using macroaggregates. ## Footnote This mechanism blocks capillaries to localize the radiopharmaceutical in the lungs.
41
What is cell sequestration?
Spleen scan with damaged RBC. ## Footnote This mechanism involves the sequestration of damaged red blood cells in the spleen.
42
What are the steps in the preparation of radiopharmaceuticals?
1. Sterilization 2. Addition of anti-microbial preservatives 3. Compounding 4. Labeling 5. Radiation Shielding.
43
What is the Anger Scintillation Camera?
A gamma camera that detects photons emitted from radioactive gamma decay and determines the two-dimensional location of the decay.
44
Who developed the gamma camera?
Hal O. Anger at Donner Laboratory in Berkeley, California in the 1950s.
45
What are the basic components of a gamma camera?
1. Gantry ## Footnote The gantry supports and moves the detector, with designs varying based on the system type.
46
What is a Cantilever Design?
A type of gantry used in imaging systems.
47
What is a Ring Type Gantry?
A type of gantry used in imaging systems.
48
What is a Collimator?
A device used to form a relationship between the original photon position and the position of the subsequent detection in the gamma camera.
49
What is the structure of a typical collimator?
Typically a 0.52 inch thick slab of lead, with a geometric array of holes in it. The lead in between each hole is called a septum.
50
What are the types of collimators?
1. Parallel Hole 2. Diverging Collimator 3. Converging Collimator 4. Pinhole Collimator
51
What is a Parallel Hole collimator?
Consists of an array of parallel holes, essentially perpendicular to the crystal face, presenting a real size image to the crystal face.
52
What is a Diverging Collimator?
Essentially upside down converging collimators, presenting a minified image of the real object to the crystal face.
53
What is a Converging Collimator?
Consists of an array of tapered holes that aim at a point in front of the collimators, presenting a magnified version of the real image.
54
What is a Pinhole Collimator?
Thick conical collimators with a single 2-5 mm hole in the bottom center, magnifying or minifying the image depending on the distance of the object from the collimator.
55
What is the function of a Detector?
Records the spatial distribution of radioactivity and its change over time, converting energy of incident photons into light and then into an electrical signal.
56
What is a Crystal in the context of scintillation cameras?
A device for converting gamma rays into visible light, scintillating when high energy photons interact with it.
57
What are the types of crystals used in scintillation cameras?
1. Sodium Iodide (NaI) Thallium activated 2. Cesium Fluoride (CsF) 3. Bismuth Germinate (BGO) 4. Barium Fluoride (BaF2) - used in PET Scan
58
What is a characteristic of NaI(TI)?
It is a hygroscopic material and is hermetically sealed against moisture to prevent yellowing.
59
What is the function of a Photomultiplier Tube?
Converts the light produced in the scintillation detector into an electrical signal, consisting of a photocathode that converts light photons into electrons.
60
What is a Cantilever Design?
A type of gantry used in imaging systems.
61
What is a Ring Type Gantry?
A type of gantry used in imaging systems.
62
What is a Collimator?
A device used to form a relationship between the original photon position and the position of the subsequent detection in the gamma camera.
63
What is the structure of a typical collimator?
Typically a 0.52 inch thick slab of lead, with a geometric array of holes in it. The lead in between each hole is called a septum.
64
What are the types of collimators?
1. Parallel Hole 2. Diverging Collimator 3. Converging Collimator 4. Pinhole Collimator
65
What is a Parallel Hole collimator?
Consists of an array of parallel holes, essentially perpendicular to the crystal face, presenting a real size image to the crystal face.
66
What is a Diverging Collimator?
Essentially upside down converging collimators, presenting a minified image of the real object to the crystal face.
67
What is a Converging Collimator?
Consists of an array of tapered holes that aim at a point in front of the collimators, presenting a magnified version of the real image.
68
What is a Pinhole Collimator?
Thick conical collimators with a single 2-5 mm hole in the bottom center, magnifying or minifying the image depending on the distance of the object from the collimator.
69
What is the function of a Detector?
Records the spatial distribution of radioactivity and its change over time, converting energy of incident photons into light and then into an electrical signal.
70
What is a Crystal in the context of scintillation cameras?
A device for converting gamma rays into visible light, scintillating when high energy photons interact with it.
71
What are the types of crystals used in scintillation cameras?
1. Sodium Iodide (NaI) Thallium activated 2. Cesium Fluoride (CsF) 3. Bismuth Germinate (BGO) 4. Barium Fluoride (BaF2) - used in PET Scan
72
What is a characteristic of NaI(TI)?
It is a hygroscopic material and is hermetically sealed against moisture to prevent yellowing.
73
What is the function of a Photomultiplier Tube?
Converts the light produced in the scintillation detector into an electrical signal, consisting of a photocathode that converts light photons into electrons.

NUCMED (2 decks)

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