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Medical Physics > Ionizing Radiation (Radioactivity) > Flashcards

Ionizing Radiation (Radioactivity) Flashcards

1
Q

What is radioactivity?

A

It is the spontaneous disintegration of nuclei with simultaneous emission of alpha, beta and gamma rays.

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2
Q

What are alpha rays?

A

Alpha particles, (alpha rays/alpha radiation), consists of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus.

4/2He

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3
Q

What is the equation used for alpha rays?

A

A/Z X –> (A-4)/(Z-2) Y + 4/2 He

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4
Q

What is the charge of alpha rays?

A

Alpha rays are POSITIVELY charged.

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5
Q

What are beta rays?

A

A beta particle, (beta ray/beta radiation) (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus during the process of beta decay.

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6
Q

What is the equation used for beta rays? for electons? for positrons?

A

A/Z X –> (A)/(Z+1) Y + e^- + v

A/Z X –> (A)/(Z-1) Y + e^+ + v

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7
Q

What are the two possible forms of beta decay?

A

β− decay (produce electrons)
β+ decay (produce positrons)

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8
Q

What are gamma rays?

A
  • very short electromagnetic waves
  • formed due to an energy change within the atomic nucleus
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9
Q

What do gamma emissions change? atomic number, or atomic mass?

A

neither!

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10
Q

What is the equation used for gamma rays?

A

80/m Br –> 80/m Br + y

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11
Q

What is ionising radiation?

A

the radiation that carries enough energy to ionise the atoms or molecules.

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12
Q

What is a half-life?

A

a measure of the tendency of the nucleus to “decay” and the time required for a quantity to reduce to half of its initial value.

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13
Q

What is the equation used to calculate a species half life?

A

T = ln2/ℷ

ℷ- radioactive decay constant = average life time

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14
Q

What is “activity” in physics?

A

the rate of decay per second

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15
Q

What is the equation for calculating the Activity (A) of an isotope?

A

A = ln2 * N / T

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16
Q

What is the SI unit of isotopic activity?

A

Bq - Becquerel

17
Q

What is 1 Bq (Becquerel) equal to?

A

1 decay / second

18
Q

What is the law of radioactive decay?

A

The number of radioactive nuclei decreases exponentially over time (ln).

19
Q

What are the three principles of radiation protection?

A

1) time
2) distancing
3) shielding

20
Q

What is the half-value layer?

A

the thickness of material at which the intensity of radiation has been reduced by half.

21
Q

What is the linear attenuation coefficient (lu (micro))?

A

a size that is inversely proportional to thickness of a layer required to reduce the intensity of radiation to magnitude of e.

22
Q

What are the main ionising radiation types?

A

alpha
beta
gamma
X-rays
rays

23
Q

What are the products of radioactivity?

A

alpha, beta and gamma

24
Q

What is “penetration power”?

A

The power (length) of an electron beam transmitted for a substance.

25
Q

What is an alpha particle?

A

a nuclear of helium

26
Q

What does a neutron divide into?

A

Neutron –> positron + electron + antineutrino
n0–> p+ + e- + ve

27
Q

What is the helium particle?

A

an alpha particle

28
Q

What are the different X-ray sources?

A
29
Q

What kind of spectrum does the x-ray tube have?

A

continuous

30
Q

What is the daily maximal radiation exposure to not have problems?

A

25 rems

31
Q

What is the daily radiation exposure that leads to death in less than 2 months?

A

> 600 rems

32
Q

What does exposure to radiation lead to?

A

DNA damage

33
Q

What are the two ways radiation can damage DNA?

A

1) Indirect (through a free radical of water)
2) Direct

34
Q

What type of scan can be created using radiation? What does it screen for?

A

Computed tomography, (CT scans), are medical imaging tests that use ionizing radiation to create cross-sectional (slices) pictures inside selected areas of the body from different angles.
- The images can show internal organs, blood vessels, soft tissues, and bones.

35
Q
A

Medical Physics (8 decks)

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