NMCTB Domain I : Radiation Physics & Detection

Tc-99m Half Life

6 hours

Tc-99m Mode of Decay

Gamma

Tc-99m Energies

140 keV

Mo99 Half Life

66 hours

Mo99 Mode of Decay

Beta, Tc parent atom

Cs-137 Half Life

30 years

Cs-137 Mode of Decay

Beta

Cs-137 Energies

662 keV, sealed source

I-123 Half Life

13.2 hours

I-123 Mode of Decay

Gamma

I-123 Energies

159 keV

I-131 Half Life

8.04 days

I-131 Mode of Decay

Beta

I-131 Energies

364 keV

Co-57 Half Life

271.8 days

Co-57 Mode of Decay

Gamma

Co-57 Energies

122 keV, sheet sourced and markers

Xe-133 Half Life

5.25 days

Xe-133 Mode of Decay

Gamma

Xe-133 Energies

81 keV

Tl-201 Half Life

73.1 hours

Tl-201 Mode of Decay

Gamma

Tl-201 Energies

82 and 135 keV

Ga-67 Half Life

78.3 hours

Ga-67 Mode of Decay

Gamma

Ga-67 Energies

93 keV, 184 keV & 300 keV

In-111 Half Life

2.83 days

In-111 Mode of Decay

Gamma

In-111 Energies

173 & 245 keV

F-18 Half Life

110 minutes

F-18 Mode of Decay

Positron

F-18 Energies

511 keV

Cu-64 Half Life

12.7 hours

Cu-64 Mode of Decay

Positron

Cu-64 Energies

511 keV

Ga-68 Half Life

68 minutes

Ga-68 Mode of Decay

Positron

Ga-68 Energies

511 keV

N-13 Half Life

10 minutes

N-13 Mode of Decay

Positron

N-13 Energies

511 keV

Rb-82 Half Life

75 seconds

Rb-82 Mode of Decay

Positron

Rb-82 Energies

511 keV

Sr-89 Half Life

50.5 days

Sr-89 Mode of Decay

Beta

Sr-89 Energies

388 keV

Y-90 Half Life

64.1 hours

Y-90 Mode of Decay

Beta

Y-90 Energies

203 keV

Ra-223 Half Life

11 days

Ra-223 Mode of Decay

Alpha

Ra-223 Energies

84 keV

Lu-177 Half Life

6.7 days

Lu-177 Mode of Decay

Beta

Lu-177 Energies

113 keV

I-125 Half life

59.5 days

I-125 Mode of Decay

Gamma

I-125 Energies

35.5 keV

Sr-82 Half Life

25.3 days

Sr-82 Mode of Decay

Positron

Sr-82 Energies

511 keV

Rb-82 generator parent atom

What is radioactive decay?

An unstable atom has excess protons or neutrons and loses them through emission of particle radiation to create a more stable atom.

Positron Decay

An atom has too many protons, resulting in the transformation of a proton into a neutron, a positron which is ejected from the nucleus, and a neutrino.

Beta Decay

The atom has too many neutrons, results in the transformation of a neutron in the nucleus into a proton which stays in the nucleus, an electron which is ejected, and a neutrino.

Gamma Decay

Atom is generally unstable, the nucleus sheds excess energy by emitting a photon of light, no change occurs in the nucleus other than a loss of energy.

Alpha Decay

The atom has too many protons and neutrons, results in the formation of a new element with 2 less neutrons, can deliver large amounts of damaging E to cells and tissues very quickly.

How much of the beam do bremsstrahlung x-rays make up?

80-90%

What are bremsstrahlung x-rays?

Breaking radiation, a force field around the nucleus causes the incident electron to slow down and emit some of its energy in the form of an x-ray

What kind of decay is most likely to create bremsstrahlung radiation?

Beta Decay

Describe the emission spectrum of bremsstrahlung x-rays

Range of energies form a continuous emission spectrum and bell-shaped emission curve

Type and probability of interaction of radiation with matter depends on?

Type of radiation

Energy of radiation

nature of matter traversed

How are characteristic x-rays produced?

Electron ejected from atom, upper shell e- drops to lower vacancy, energy released is characteristic x-ray

Photoelectric Interaction

Occurs when all energy of the photon is transferred to an orbital electron, orbital electron is then ejected and termed a photoelectron.

Comptom Scatter

Incident photon interacts with atom, resulting in re-direction of photon w/ decreased energy and ejection of orbital electron from path.

Probability _____ as electron density increases in Compton Scatter.

Increases

Probability ______ as energy of photon increases in Compton Scatter.

Decreases

Probability _____ as Z increases in Compton Scatter.

Does NOT affect

As the angle increases (up to 180) in Compton scatter, how does the energy given to the recoil electron change?

The energy increases as angle increases.

What does the term "backscatter" describe in photoelectric interactions?

Compton interaction, 180 degree scattering angle.

Causes maximum energy transfer.

What material is used in well counters?

NaI(Tl) Crystal

Dose calibrators operate in what region?

Ionization Chamber Region

Ion Chambers measure what?

Exposure

What radiation detecting equipment in nuclear medicine uses a SCINTILLATOR?

Well counters

Uptake Probes

Gamma Cameras

PET Scanners

What radiation detecting equipment in nuclear medicine uses GAS?

Dose calibrators

Survey Meters

Dead Time

Period between the initial pulse and the time at which a second Geiger discharge, regardless of size, can be developed.

In GM meters, what is Recovery Time?

The time interval required for the tube to return to its original state and become capable of producing a second pulse of full amplitude.

In GM meters, what is Resolving Time?

The time interval required to develop a discharge whose amplitude exceeds the discrimination level --> it is the time to the next detectable event.

What is quenching?

Prevention of electron avalanches in GM meter caused by release of electrons.

What are some qualities of semiconductor detectors?

Great energy resolution

Low resolving time

High cost

What are common semiconductor detector types?

CZT, HPGe

What is the use of NaI (Tl) Crystal?

Gamma Camera

What is the use of an Ion Chamber?

Dose Calibrator

What is the use of the GM Meter?

Contamination

What is the use of a Solid-State?

PET

What are some examples of alpha emitters?

Ra-223 & Ac-225

What are some examples of beta emitters?

I-131, Sr-89, Y-90 & Lu-177

What are some examples of gamma emitters?

Tc-99m, Tl-201, Xe-133, In-111, Ga-67, I-123 & I-125

What are some examples of positron emitters?

F-18, N-13, Ga-68, Rb-82 & Cu-64

Electron Capture

Also known as inverse beta decay, an orbital electron is captured by the nucleus where it combines with a proton to form a neutron, characteristic x-ray production.