| Date | May 2016 | Marks available | 1 | Reference code | 16M.3.hl.TZ0.25 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Outline | Question number | 25 | Adapted from | N/A |
Question
Radioactive isotopes are used in a variety of medical procedures including medical imaging and radiotherapy.
Lead-212 is a radioisotope that is used in the treatment of cancer. It is produced from another radioisotope by alpha decay. Formulate the equation for its production.
Identify one advantage of using Targeted Alpha Therapy (TAT) and one form of cancer commonly treated by this method.
Advantage:
Cancer treatment:
Technetium-99m, used for radioimaging scans, has a half-life of 6.01 hours. Calculate the mass of a 5.80×10−9 g dose remaining after 24.04 hours.
Outline an ethical implication of using nuclear treatments in medicine.
Markscheme
\({}_{84}^{216}{\rm{Po}} \to {}_2^4{\rm{He + }}{}_{82}^{212}{\rm{Pb}}\)
correct reactant
correct alpha particle
Atomic numbers not required for mark.
Accept “α”/“\({}_2^4\alpha \)” for “\({}_2^4{\rm{He}}\)”.
Advantage:
selectively kills cancer cells/targets cancer cells only
OR
does not damage healthy cells
Do not accept “targets cancer”. Reference must be made to “cells”.
Cancer treatment:
melanoma
OR
leukemia
OR
rectal
OR
breast
OR
ovarian
OR
prostate
OR
pancreatic
OR
cancers that spread around the body/produce metastasis/dispersed cancers
Accept “skin cancer”.
ALTERNATIVE 1:
\(\lambda \ll = \frac{{\ln 2}}{{6.01}} \gg \approx 0.115 \ll {{\rm{h}}^{ - 1}} \gg \)
«remaining mass = 5.80×10-9×e-0.115 × 24.04=»3.63×10-10 «g»
ALTERNATIVE 2:
\( \ll \frac{{24.04}}{{6.01}} = \gg 4 \ll {\rm{half lives}} \gg \)
\( \ll \frac{{5.80 \times {{10}^{ - 9}}}}{{{2^4}}} = \gg 3.63 \times {10^{ - 10}} \ll {\rm{g}} \gg \)
Award [2] for correct final answer.
risk vs benefit «patient and environment»
OR
providing adequate information to patients about risks
OR
security concerns if nuclear radioactive material ended up with terrorists
OR
cultural resistance/superstition/lack of education
OR
«potential» exposure of health workers «to radioactivity»
OR
proper training «in radioactive hazards» not always given to workers
OR
proper disposal of radioactive materials
Accept other valid ethical implications (note that risk of cancer to the patient is not an ethical issue, while risk of cancer to the health worker is).
Do not accept “security concerns” alone – there must be some reference to an ethical implication.
