Radiation Dose Measurement Techniques

Questions and Answers

What is required to determine the dose rate in the ionization chamber?

Calculating the mass of gas only

Measuring the current due to ionization (correct)

Knowing the type of radiation

Assessing the temperature of the chamber

What is the value of the W in the example given?

33 eV ip–1 (correct)

40 eV ip–1

10 eV ip–1

15 eV ip–1

When the absorbed dose rate in the wall is 10 mGy h–1, what is the resulting current?

$1.23 × 10^{-10}$ A

$1.23 × 10^{-11}$ A (correct)

$7.67 × 10^{-7}$ A

$2.78 × 10^{-11}$ A

How much gas is contained in the chamber described in the example?

0.15 g Signup and view all the answers

What does the ratio of the mass stopping power of the wall and the gas indicate in the calculation?

Energy absorbed per unit mass Signup and view all the answers

What does the variable $Ṅ_g$ represent in the context of the calculations?

Rate of ion-pair production in the gas Signup and view all the answers

Why are simple electrometer circuits necessary for this measurement?

They can measure currents below 10–14 A Signup and view all the answers

What relationship does Eq.(12.12) establish regarding the current?

It involves the absorbed dose and the mass stopping power Signup and view all the answers

At which neutron energy does the probability, P(E), reach its maximum value according to the provided data?

20.0 MeV Signup and view all the answers

What characteristic of tissue is significantly affected by neutron energy according to the content?

Chemical composition Signup and view all the answers

In order for the absorbed dose in tissue to be accurate when measuring neutrons, what two conditions need to be met?

Walls and gas are tissue equivalent Signup and view all the answers

What does the Bragg–Gray principle primarily ensure when measuring neutron energy interactions?

Accuracy of dose measurements Signup and view all the answers

How does the response of the carbon wall of a chamber differ from that of soft tissue when exposed to a field of mixed energies?

It does not account for lighter elements. Signup and view all the answers

What is the relationship established by the equation P(E) = DnC(E) / DγC?

Neutron dose to photon dose ratio Signup and view all the answers

Which neutron energy has a probability, P(E), value closest to 0.15 based on the data provided?

0.5 MeV Signup and view all the answers

Which element is notably absent in the carbon wall according to the context, affecting its neutron response?

Hydrogen Signup and view all the answers

What is the absorbed dose delivered by neutrons to soft tissue determined in the example?

13.4 mGy Signup and view all the answers

What relationship does the equation P(E)Dn = 0.149 Dn suggest?

The neutron tissue dose Dn is a function of an absorbed dose. Signup and view all the answers

What must be true about a tissue-equivalent neutron chamber's wall thickness?

It should be at least as thick as the range of a proton with maximum energy. Signup and view all the answers

In monitoring mixed gamma-neutron radiation fields, why is it necessary to determine the individual contributions to absorbed dose?

To assign proper quality factors for neutron contributions. Signup and view all the answers

If a tissue-equivalent ionization chamber registers 0.082 mGy h–1, what would this reading represent?

Combined dose from gamma and neutron radiation Signup and view all the answers

What does the reading of the C CO2 chamber represent when exposed to mixed radiation?

It combines both gamma radiation and neutron contributions. Signup and view all the answers

How can one infer the individual doses of gamma and neutrons from the readings of two different chambers?

Through a difference method using both readings. Signup and view all the answers

What is the purpose of using tissue-equivalent gases and plastics in neutron dose measurement?

To effectively replicate human tissue interactions with radiation. Signup and view all the answers

What effect does using a larger number of neutron histories have on the calculated quantities?

Reduces variance while increasing computer time Signup and view all the answers

What is the shape of the curve for total dose as neutrons penetrate the soft-tissue slab?

It builds up in the first few centimeters and then decreases Signup and view all the answers

Which curve in the study indicates the dose from gamma rays resulting from slow-neutron capture?

Eγ Signup and view all the answers

At which depth range does the gamma-dose curve show a maximum?

6 cm to 14 cm Signup and view all the answers

What incident energy of neutrons was used in the Monte Carlo calculations mentioned?

5-MeV Signup and view all the answers

What type of particles primarily contributes to the dose indicated by the curve labeled EH?

Heavy recoil nuclei (O, C, N) Signup and view all the answers

What happens to the energy of neutrons as they penetrate deeper into the soft tissue?

They are absorbed and lose energy Signup and view all the answers

What does the depth-dose curve for charged particles in the figure represent?

The relationship between depth and dose for non-thermal neutrons Signup and view all the answers

What is the average energy loss for other nuclei in soft tissue compared to the maximum energy loss?

Approximately one-half the maximum energy loss Signup and view all the answers

What does the first-collision dose represent in radiation dosimetry?

The dose delivered by neutrons making only a single collision Signup and view all the answers

When is the first-collision dose closely approximated to the actual dose in soft tissue?

When the mean free path is large compared to the target dimensions Signup and view all the answers

What is the macroscopic cross section of a 5-MeV neutron in soft tissue?

0.051 cm–1 Signup and view all the answers

In the provided example, what is the density of hydrogen atoms used for calculations?

5.98 × 10^22 cm–3 Signup and view all the answers

What is the mean energy loss per collision for 5-MeV neutrons in the context of the example?

2.5 MeV Signup and view all the answers

With which element do fast neutrons primarily deposit most of their energy in tissue?