Review Questions Flashcards by Megan Ludlow

Acronym for older KV machines

GCSOS

How well did you know this?

Not at all

Perfectly

Energy for Grenz - Ray Therapy

20 KV

How well did you know this?

Not at all

Perfectly

Energy for Contact Therapy

40-50 KV

How well did you know this?

Not at all

Perfectly

Energy for Superficial Therapy

50-150 KV

How well did you know this?

Not at all

Perfectly

Orthovoltage

150-500Kv

How well did you know this?

Not at all

Perfectly

Supervoltage

500-1000kV

How well did you know this?

Not at all

Perfectly

What is difference between kVp and KeV

kVp is manmade and polyenergetic
KeV is monoenergetic

How well did you know this?

Not at all

Perfectly

Van De Graff generator, linear accelerator, betatron, microtron, and gamma ray like Co-60

Megavoltage Therapy

How well did you know this?

Not at all

Perfectly

Which megavoltage machine has a donut?

Betatron (circular accelerator)

How well did you know this?

Not at all

Perfectly

Betatron Energy

6-40MeV

How well did you know this?

Not at all

Perfectly

Which megavoltage machine has the downside of low dose photon rate due to the high need for electrons

Betatron

How well did you know this?

Not at all

Perfectly

Which megavoltage machine has the downside of 1000x the need for photons compared to electron alone

Betatron

How well did you know this?

Not at all

Perfectly

For microtron the more energy of electrons =

Increase radius traveled

How well did you know this?

Not at all

Perfectly

Megavoltage machine with oscillating electric field of a microwave accelerates electrons

Microtron

How well did you know this?

Not at all

Perfectly

Van de Graff Generator

2Mv-25MV

How well did you know this?

Not at all

Perfectly

Tomotherapy SAD

85cm

How well did you know this?

Not at all

Perfectly

Tomotherapy energy for tx and imaging

6MV for fx; 3.5 for imaging

How well did you know this?

Not at all

Perfectly

Why does tomo not have a flattening filter

Blurs itself out with 360 degree circulation

How well did you know this?

Not at all

Perfectly

Cyclotrons main clincial use

Protons

How well did you know this?

Not at all

Perfectly

Cyclotrons: Increase energy means_____

increased depth of Bragg Peak

How well did you know this?

Not at all

Perfectly

How many cyclotron can support how many gantry heads?

3-4

How well did you know this?

Not at all

Perfectly

What is the main source of protons

Hydrogen gas

How well did you know this?

Not at all

Perfectly

Cyclotron can also be used to

make radionuclides

How well did you know this?

Not at all

Perfectly

Cyclotron shape is?

double D’s

How well did you know this?

Not at all

Perfectly

Typical energy of proton therapy

70-250 MV

Spread out bragg peak (SOBP)

Variety of energies which are used to cover variety of energies

What has the highest binding energy?

Inner electron shell

how to calc the characteristic xray energy

it is M-K shell; M-L (difference in binding energies)

Why is atomic mass not a round number?

Weighted average due to abundance in isotopes

Resting mass for electrons and positrons

9.11 x 10^-31

Resting mass is in

Resting mass for protons

1.672 x 10 ^-27

Resting mass for Neutrons

1.675 x 10 ^-27

Rest energy for proton

938.3 MeV

Rest energy for Neutrons

939.6 MeV

Mean life

1.44(T1/2)

Decay constant is

ln2/(half life)

Electron capture is similar to and why

B+ since proton is becoming neutron

MODES of DECAY

Electron capture is more likely with

- Higher Z # or nucleus with lots of protons

Electron capture is when

an orbital e- gets captured by the nucleus, combines with proton and become a neutron

Compton effect; 90 degree scatter results in

.511MeV

Compton effect; 180 degree backscatter results in

.255MeV

Increased energy does what to forward peak

increases forward peak

Pair Production threshold

1.02 MeV

Neutron contamination is more likely with

10MV or higher

Total kinetic energy of all particles is the same before and after collison

Elastic collision

Kinetic energy is lost (lost energy goes to excitation, ionization or bremsstrahlung)

Inelastic collision

Electron stopping power

2MeV/Cm

atoms of the target become ionized or excited and lead to events resulting in biologic change

Direct action

Measure of the rate at which energy is transferred from ionizing radiation to soft tissue

LET (Linear Energy Transfer)

Best absorbers of neutrons

hydrogenous materials

Where is a beam defined at for flatness

10cm depth in water 80% (cant do edges due to penumbra)

How does flatness change with a depth shallower than 10cm and a depth deeper than 10cm

Shallow has lateral horns Deeper has a middle hump

Lateral horns are quantity or quality

quantity ( number of photons)

Flatness is quantity or quality

quantity ( number of photons)

flattening filter affect on output

4 times

Flattening filter affects quality or quantity

quantity ( number of photons) Can be quality as it hardens the beam

can you use same flattening filter for multiple energies

A flattening filter__________ The average energy and____________ the total radiation quantity

Increases , decreases

Which of the following decay modes is most prominent in the heavier elements

Alpha

An increase in KVP has a________ effect on electron output - while MAs has A___________ effect

Squared / direct

Which of the following photon interactions results in a scattered photos w/ less energy & an ejected orbital electron

Compton

Which of the following radiation measurement devices utilize a p-type and n type junction

Silicon diode

Which of the following organizations would be utilized to calibrate an ion chamber for a clinical site

ADCL

How would an increase in SSD affect geometric penumbra width

Increase

What factor has a indirect relationship w/ penumbra

SDD

Compared to photon mode electron mode uses a________ machine current and the___________ on the carousel

Lower / scattering foil

Half life of iodine 131

8.06 days

Half life of cesium 131

9.69 days

Half life of palladium 103

17 days

Half life of iodine 125

59.4 days

Half life of cobalt 60

5.26 years

Half life of indium 192

73.8 days

Half life of cesium 137

30.0 yrs

Half life of radon 222

3.83 days

Half life of radium 226

1626 yrs

A phenomenon in which one orbital electron taken by the nucleus and transforms a proton in to a neutron

Electron capture

Electron capture is shown in a nuclear decay on what side of the formula

Left side

Electron capture is competeing conversion with?

Positron decay

Another name for characteristic xrays produced by interactions of photons with the atom is

fluorescent xrays

Auger electrons ar more probable with

low z numbers

Decay mode atom with a deficit number of neutrons and their n/p ratios are lower

Positron emission

Mass energy difference between the parent and daughter atoms for B+ must be

1.02 MeV (positron emission)

Decay mode atom with excessive number of neutrons and their n/p ratios are high

Negatron emission/ B-

Mode of decay more common with high atomic number radiunuclides

alpha

a negatively charged electron emitted from a nucleus.

β− particle (negatron)

a positively charged electron emitted from a nucleus.

β+ particle (positron)

Mode of decay that is likened into "internal photoelectric effect"

Electron capture

Fusion of _______ into _______is the source of our sun’s energy.

hydrogen nuclei; helium nuclei

Example of Nuclear reactions

Fission/ fusion

Linac treatment head is shielded by

lead, tungsten, or lead–tungsten alloy