Review questions answers

Review questions

13.1 Scintigraphy is used to detect radioisotopes that emit which kind of radiation?

A.      Alpha

B.      Beta

C.      Gamma

D.      Delta

13.2 Which radiation is the most penetrating?

A.      Alpha

B.      Beta

C.      Gamma

D.      Delta

13.3 Which radiation is the least penetrating?

A.      Alpha

B.      Beta

C.      Gamma

D.      Delta

13.4 Artificial radioisotopes are produced by bombarding atoms of stable, naturally occurring elements with fast-moving …

A.      Electrons

B.      Protons

C.      Neutrons

D.      Atoms

13.5 Which one of the following is the most commonly used radioisotope in medical applications today?

A.      Technetium

B.      Molybdenum

C.      Iodine

D.      Carbon

13.6 Containers that are used to safely store and transport radioisotopes must be made of which metal?

A.      Iron

B.      Aluminum

C.      Copper

D.      Lead

13.7 Which of the following statement is not correct?

A.      Isotope has the same proton number but different neutron number

B.      Isotope has different mass

C.      All the isotopes are radioactive

D.      None of the above

13.8 An archeologist finds that an artifact containing 14C was found to contain 3 disintegrations per minute (dpm) of radioactivity. Knowing from literature that the half-life of 14C is 5700 years and that the decay rate of a fresh 14C sample is 15 dpm, how much age would the archeologist assign to the artifact?

13.9 The doctor prescribed a dose of 30 mCi of a particular radioisotope to a patient. The hospital has this radioisotope in inventory, pur-chased 9 days ago at 600 mCi/g. Knowing from literature that this radioactive element has a half-life of 6 days, how much dose in grams should the pharmacist dispense for the patient?

13.10 Which one of the following is not a key consideration to improve radiation safety?

A.      Time

B.      Temperature

C.      Distance

D.      Shielding

13.11 Which one of the following is a handheld device used for the detec-tion of ionizing radiation by laboratory safety personnel?

A.      PET scanner

B.      SPECT scanner

C.      Geiger–Muller counter

D.      Scintillation counter

13.12 Radionuclides typically decay by α-particle, β-particle, or γ-ray emission. For diagnostic radiopharmaceuticals, which type of decay is preferable?

A.      α-particle emission

B.      β-particle emission

C.      γ-ray emission

D.      All of the above

Answers:

13.1 C.

13.2 C.

13.3 A.

13.4 C.

13.5 A.

13.6 D.

13.7 C.

13.8 The rate equation of decay of a radioactive compound, which follows a nonlinear first-order exponential rate kinetics given by

N(t ) = N(0)e^−λt

Here, radioactivity, typically represented by curie, C_i, can also be expressed as disintegrations per minute (dpm), since one C_i = 3.7 × 10¹⁰ Bq or dps = 2.22 × 10¹² dpm.

N(0) = 15 dpm

t = ? years

t_1/2 = 5,700 years

N(t) = 3 dpm

Where, λ, the rate of decay can be calculated as

λ= ln2/ t_1/2 = 0. 693/ t_1/2 = 0.693/5700 = 1.216 ×10⁻⁵ year⁻¹

Thus,

3= 15e^{−1.216 ×10−5 t}

or

ln3 = ln15 − 1.216 × 10⁻⁵ × t

or

t = ln 15 − ln3 / (1.216 ×10⁻⁵) = 132, 378 years

13.9 The rate equation of decay of a radioactive compound, which fol-lows a nonlinear first-order exponential rate kinetics given by

N(t ) = N(0)e^−λt

N(0) = 600 mCi/g

t = 9 days

t_1/2 = 6 days

N(t) = ? mCi/g

Where, λ, the rate of decay can be calculated as

λ = ln2/ t_1/2 = 0. 693/ t_1/2 = 0.693/6 = 0.1155 day⁻¹

ln N (t ) = ln N (0) − λt

ln N (t ) = ln600 − 0. 1155 × 9 = 5.3574

N(t ) = e^5.3574 = 212 .18.

Thus, at the end of 9 days, the radioactivity left in the compound is ~212 mCi/g.

Therefore, to dispense 30 mCi of radioactivity to the patient, the pharmacist would need to dispense, 30/212 = 0.14 g of compound.

13.10 B.

13.11 C.

13.12 C.