Question 20N.3.hl.TZ0.17b
| Date | November 2020 | Marks available | [Maximum mark: 3] | Reference code | 20N.3.hl.TZ0.17b |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Discuss | Question number | b | Adapted from | N/A |
Technetium-99m is the most commonly used isotope for diagnostic medicine.
Discuss the properties that make a radioisotope suitable for diagnosis.
[3]
Any three of:
«easily» detected/traced
OR
«gamma-radiation of approximately» same frequency as X-rays «so can be detected using existing X-ray equipment» ✔
short/intermediate half-life «hence does not remain in body for long time» ✔
weak ionizing radiation «less harmful»
OR
low amount of radiation produced «so less harmful»
OR
energy of photons is low ✔
form «variety of» compounds that are absorbed by «different» organs
OR
«chemically» binds to many biologically active compounds ✔
excreted quickly «from body» ✔
Some excellent answers were seen for this question; often candidates were hitting four of the assigned marking points, though a few candidates confused diagnosis and radiotherapy. Nearly everyone got a mark for "short half-life", however. This question was much better answered than in previous sessions.
