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Date May 2017 Marks available 1 Reference code 17M.3.hl.TZ2.26
Level HL Paper 3 Time zone TZ2
Command term State Question number 26 Adapted from N/A

Question

Targeted Alpha Therapy (TAT) is a technique that involves using alpha-radiation to treat leukemia and other dispersed cancers.

Yttrium-90 and lutetium-177 are used in radiotherapy.

Explain why alpha-radiation is particularly suitable for this treatment.

[2]
a.i.

Outline how the alpha-radiation in TAT is directed to cancer cells.

[1]
a.ii.

Identify the type of radiation emitted by these two radioisotopes.

[1]
b.i.

State an equation for the one-step decay of yttrium-90.

[1]
b.ii.

The half-life of lutetium-177 is 6.75 days. Calculate the percentage remaining after 27 days.

[1]
b.iii.

Markscheme

more damaging than other radiation types
OR
very damaging to «cancer» cells
OR
high ionizing density «of alpha particles»

absorbed within a very short range of emission
OR
causes little damage to surrounding tissues

 

Accept “high ionizing power «of alpha particles»” for M1. 

Accept “low penetrating power «of alpha particles»” for M2.

[2 marks]

a.i.

«radioactive isotope/radionuclide/alpha-emitter» administered using carrier drug/protein/antibodies

[1 mark]

a.ii.

beta/β «radiation»

[1 mark]

b.i.

9039Y9040Zr+β

 

Accept "01e/e/e" OR "01β/β"

Accept ECF from (b) (i) if incorrect radiation identified, eg, 9039Y8637Rb+42He

[1 mark]

b.ii.

ALTERNATIVE 1:
«4 half-lives»
6.25 «%»

ALTERNATIVE 2:
«NtN0(0.5)tt1/2=100(0.5)276.75=» 6.25 «%»

[1 mark]

b.iii.

Examiners report

[N/A]
a.i.
[N/A]
a.ii.
[N/A]
b.i.
[N/A]
b.ii.
[N/A]
b.iii.

Syllabus sections

Options » D: Medicinal chemistry » D.8 Nuclear medicine (HL only)

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