NMTCB Radiation Physics & Detection 5

Question 1

The Bragg peak phenomenon associated with charged particle beams describes:

Accepted Answer

The sharp increase in energy deposition near the end of a charged particle's range in matter

Answer

As a heavy charged particle slows near the end of its range, its interaction cross-section increases dramatically, causing a sharp peak in energy deposition (the Bragg peak).

Question 2

For a counting system, the minimum detectable activity (MDA) is primarily determined by:

Accepted Answer

Background count rate, detector efficiency, and counting time

Answer

MDA depends on the background count rate (which creates statistical uncertainty), detector efficiency (converting decays to counts), and counting time (reducing statistical uncertainty).

Question 3

The backscatter peak observed in a pulse height spectrum is caused by:

Accepted Answer

Photons that undergo Compton scattering in shielding material and enter the detector at ~180° scatter angle

Answer

Photons Compton-scattered through approximately 180° in surrounding shielding lose maximum energy and enter the detector with ~200 keV (for 662 keV source), creating the backscatter peak.

Question 4

Transient equilibrium differs from secular equilibrium in that during transient equilibrium:

Accepted Answer

Parent and daughter have similar half-lives and daughter activity exceeds parent activity at equilibrium

Answer

In transient equilibrium, the parent half-life is only moderately longer than the daughter's, so at equilibrium the daughter activity slightly exceeds the parent activity due to the branching factor.

Question 5

The isobar line on a Segré chart connects nuclides that have:

Accepted Answer

The same mass number (A) but different atomic numbers (Z)

Answer

Isobars share the same mass number A = Z + N but have different numbers of protons and neutrons, appearing as diagonal lines on the Z vs N chart.

(NMTCB) Nuclear Medicine Technology Certification Board Practice Test

(NMTCB) Nuclear Medicine Technology Certification Board Practice Test

NMTCB Radiation Physics & Detection 5