NMTCB Radiation Physics & Detection 3

Question 1

The resolving time correction formula for a detector with observed count rate n and dead time τ gives the true count rate as:

Accepted Answer

N = n / (1 - nτ)

Answer

For a paralyzable or non-paralyzable detector approximation at moderate count rates, true count rate N = n/(1 - nτ) corrects for events lost during dead time.

Question 2

Internal conversion coefficient (α) is defined as the ratio of:

Accepted Answer

Internal conversion electron emission rate to gamma ray emission rate

Answer

The internal conversion coefficient α = Ne/Nγ, where Ne is the number of conversion electrons and Nγ is the number of gamma rays emitted per unit time.

Question 3

Which detector type is used in PET scanners primarily because of its:

Accepted Answer

Ability to detect coincident 511 keV annihilation photons with high stopping power

Answer

PET detectors must efficiently stop 511 keV photons and detect coincident pairs; scintillators like LSO/LYSO with high density and Z provide this stopping power.

Question 4

The Bateman equations describe:

Accepted Answer

Buildup and decay kinetics of daughter nuclides in a radioactive decay chain

Answer

Bateman equations give the activity of each member of a radioactive decay series as a function of time, accounting for both production and decay of each nuclide.

Question 5

Energy resolution of a scintillation detector is expressed as:

Accepted Answer

FWHM of a photopeak divided by the peak centroid energy, expressed as a percentage

Answer

Energy resolution (%) = (FWHM/E₀) × 100, where FWHM is the full width at half maximum of the photopeak and E₀ is the photopeak centroid energy.

(NMTCB) Nuclear Medicine Technology Certification Board Practice Test

(NMTCB) Nuclear Medicine Technology Certification Board Practice Test

NMTCB Radiation Physics & Detection 3