Question
Question
Nuclear medicine uses small amounts of radioisotopes to diagnose and treat some diseases.
a. State two common side effects of radiotherapy.
b. Explain why technetium-99m is the most common radioisotope used in nuclear medicine.
c. $25.0 \mu \mathrm{g}$ of iodine-131, with a half-life of 8.00 days, was left to decay.
Calculate the mass of iodine-131, in $\mu \mathrm{g}$, remaining after 32.0 days. Use section 1 of the data booklet.
▶️Answer/Explanation
Markscheme
a. Any two of:
hair loss
fatigue
nausea
sterility
skin reaction
diarrhoea
vomiting
damage to lymph system
urinary/bladder changes
anxiety/emotional problems
joint/muscular stiffness
loss of appetite
sore/dry mouth
loss of weight
secondary cancer
b. Any two of:
half-life is 6 hours/long enough for a scan to occur
OR
half-life short enough not to remain in body
NOTE: Accept “short half-life so patient is not exposed to lots of ionizing radiation”.
decay releases «low energy» gamma rays
OR
gamma rays less likely to be absorbed by cells
can form several «coordination» complexes
NOTE: Accept “can exist in many oxidation states “so can form multiple complexes»” OR “chemically versatile “so can act as a tracer by bonding to several bioactive compounds»”.
«low-energy» radiation/gamma-rays can be detected by common X-ray equipment
c. ALTERNATIVE 1
4 half-lives
$1.56 « \mu \mathrm{g}$ of iodine-131 remain»
ALTERNATIVE 2
$m=25.0\left(\frac{1}{2}\right)^{\frac{32.0}{8.00}}$
$1.56 \varkappa \mu \mathrm{g}$ of iodine-131 remain»
ALTERNATIVE 3
$\Lambda=《 \frac{\ln 2}{8.00} »=8.66 \times 10^{-2}$ «day $^{-1} »$
$m=« 25.0 \mathrm{e}^{-8.66 \times 10^{-2} \times 32.0}=» 1.56 \ll \mu \mathrm{g}$ of iodine-131 remain»