Pharmaceutical Drugs and Dosage: Radiopharmaceuticals - 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*^{−λ}^{t}

Here,
radioactivity, typically represented by curie, *C*_{i}, can also be expressed as disintegrations per minute
(dpm), since one *C _{i}* = 3.7
× 10

*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.

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