Radiopharmaceuticals and instrumentation

56 Gulf Prometric Radiographer (DHA, DOH, MOH, SCFHS, QCHP) practice questions on Radiopharmaceuticals and instrumentation, part of Nuclear Medicine. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Easy

   The half-life of fluorine-18 is approximately:

   1. A20 minutes
   2. B6 hours
   3. C110 minutes
   4. D2 minutes

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   Answer: C · 110 minutes

   F-18 has a half-life of about 110 minutes, which is long enough for delivery from a regional cyclotron to hospitals, and short enough to keep the dose acceptable.

   • A: About 20 minutes is the half-life of C-11.
   • B: 6 hours is the half-life of Tc-99m.
   • D: About 2 minutes is the half-life of O-15.

   Remember this

   F-18 half-life is about 110 minutes.

2. Question 2 · Medium

   I-123 is preferred over I-131 for diagnostic thyroid imaging mainly because I-123 has:

   1. AA 159 keV photon, no beta emission and a shorter half-life
   2. BA longer half-life of 8 days, which gives a better image
   3. CA 364 keV gamma ray that suits the low-energy collimator
   4. DBeta particles that destroy thyroid tissue and give a dose

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   Answer: A · A 159 keV photon, no beta emission and a shorter half-life

   I-123 has a half-life of 13.2 hours and emits a 159 keV gamma ray with no beta emission, so it gives a good image at a low dose. I-131 has a half-life of 8 days and emits beta particles, which makes it suitable for treatment and not for routine diagnostic imaging.

   • B: 8 days is the half-life of I-131.
   • C: 364 keV is a photon energy of I-131.
   • D: Beta particles that destroy tissue are the reason for I-131 therapy.

   Remember this

   I-123 is for imaging and I-131 for therapy.

3. Question 3 · Medium

   A lead container is placed around the eluate vial in a dose calibrator to check for Mo-99 breakthrough. This works because:

   1. ALead removes aluminium ions from the eluate in the vial
   2. BLead absorbs the 140 keV Tc-99m photons, but high-energy Mo-99 photons pass
   3. CLead converts the Mo-99 present in the vial into Tc-99m
   4. DMo-99 photons are absorbed and Tc-99m photons pass through the lead

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   Answer: B · Lead absorbs the 140 keV Tc-99m photons, but high-energy Mo-99 photons pass

   A lead shield of a few millimetres stops nearly all 140 keV photons of Tc-99m but lets a large part of the 740 and 778 keV photons of Mo-99 through. The remaining reading is the Mo-99 activity, which is then compared with the Tc-99m activity.

   • A: Lead does not take part in a chemical test.
   • C: Lead does not change a radionuclide.
   • D: The opposite is true: the lower-energy photons are stopped more easily.

   Remember this

   the lead shield blocks Tc-99m and passes Mo-99.

4. Question 4 · Medium

   A weekly bar-phantom study assesses mainly:

   1. ADose calibrator accuracy over time
   2. BSpatial resolution and linearity
   3. CEnergy resolution of the camera only
   4. DSterility of the radiopharmaceutical kit

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   Answer: B · Spatial resolution and linearity

   A bar phantom has lead bars of different widths and spacing. The smallest bars that can be separated show the resolution, and straight bars show the linearity of the image.

   • A: Dose calibrator accuracy is tested with reference sources.
   • C: Energy resolution is checked with the spectrum.
   • D: Sterility is tested in a pharmacy and not with a phantom.

   Remember this

   bar phantoms test resolution and linearity.

5. Question 5 · Medium

   A thin-layer chromatography test on a Tc-99m kit shows 12% of the activity as free pertechnetate. This result means that:

   1. ARadionuclidic purity is poor because of Mo-99 breakthrough
   2. BRadiochemical purity is only 88%, below the usual 90% minimum for kits
   3. CThe kit is acceptable because 88% is above 85%
   4. DChemical purity is acceptable because aluminium is low

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   Answer: B · Radiochemical purity is only 88%, below the usual 90% minimum for kits

   Radiochemical purity is the fraction of the radionuclide present in the desired chemical form. Most Tc-99m kit inserts require at least 90%, and some 92 to 95%, so 88% fails; free pertechnetate would give unwanted images of the stomach, thyroid and salivary glands. The limit for each kit is taken from its package insert.

   • A: Radionuclidic purity concerns other radionuclides such as Mo-99.
   • C: Most kits require at least 90%, so the kit should not be used.
   • D: Chemical purity concerns non-radioactive contaminants such as aluminium.

   Remember this

   Radiochemical purity is usually required to be at least 90%; check the kit insert.

6. Question 6 · Medium

   Which tracer is used for PET imaging of neuroendocrine tumours that express somatostatin receptors?

   1. AGa-68 DOTATATE
   2. BI-123 ioflupane
   3. CTc-99m sestamibi perfusion agent
   4. DF-18 sodium fluoride

   Answer and explanation in LearnFree account

7. Question 7 · Hard

   An FDG dose is calibrated at 370 MBq at 10:00. The patient is injected at 13:40. Using a half-life of 110 minutes, what activity will be injected?

   1. AAbout 278 MBq
   2. BAbout 46 MBq
   3. CAbout 92 MBq
   4. DAbout 185 MBq

   Answer and explanation in LearnFree account

8. Question 8 · Hard

   An FDG PET study shows a tumour with an activity concentration of 40 kBq/mL. The patient weighs 74 kg and the decay-corrected injected dose is 370 MBq. What is the SUV (body weight)?

   1. A2.0
   2. B8.0
   3. C0.8
   4. D80

   Answer and explanation in LearnFree account

9. Question 9 · Easy

   Which instrument is most suitable for finding low-level radioactive contamination on a bench or floor?

   1. AA gamma camera with a flood source
   2. BA personal film badge
   3. CA Geiger-Muller survey meter with a thin window
   4. DA re-entrant dose calibrator

   Answer and explanation in LearnFree account

10. Question 10 · Medium

    The parent radionuclide in a gallium-68 generator is:

    1. AMolybdenum-99, with a half-life of about 66 hours
    2. BGallium-67, with a half-life of about 78 hours
    3. CStrontium-82, with a half-life of about 25 days
    4. DGermanium-68, with a half-life of about 271 days

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11. Question 11 · Medium

    Filtered back projection in SPECT reconstruction is known to produce:

    1. AHigher noise only in the dark areas of the image
    2. BAutomatic and complete scatter correction
    3. CPerfectly uniform images with no noise at all
    4. DStreak artefacts near areas of intense activity

    Answer and explanation in LearnFree account

12. Question 12 · Hard

    A Mo-99/Tc-99m generator is calibrated at 37 GBq of Mo-99 on a Monday at 12:00. The half-life of Mo-99 is 66 hours. What activity of Mo-99 remains 5.5 days later?

    1. AAbout 25 GBq
    2. BAbout 9.25 GBq
    3. CAbout 18.5 GBq
    4. DAbout 4.6 GBq

    Answer and explanation in LearnFree account

13. Question 13 · Easy

    The instrument used to measure the activity of a vial or syringe before injection is:

    1. AA personal film badge worn on the chest of staff
    2. BA gamma camera used with a flood source
    3. CA Geiger-Muller survey meter held near the syringe
    4. DA dose calibrator, a well-type ionisation chamber

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14. Question 14 · Medium

    A patient exercised in the gym the previous evening before an FDG PET scan. What problem is likely?

    1. ADecreased FDG uptake in the brain only, with normal muscles
    2. BIncreased FDG uptake in skeletal muscles that may obscure findings
    3. CAbsent bladder activity because the kidneys are not working
    4. DFree pertechnetate seen in the stomach and the thyroid gland

    Answer and explanation in LearnFree account

15. Question 15 · Medium

    As the injected activity in a PET study increases, random coincidences:

    1. AFall in proportion to the increase of activity injected
    2. BStop completely once the timing window is narrowed
    3. CRise faster than trues, roughly with the square of the singles rate
    4. DStay constant whatever the activity in the field of view

    Answer and explanation in LearnFree account

16. Question 16 · Medium

    Compared with a low-energy high-resolution collimator, a low-energy all-purpose collimator has:

    1. ALower sensitivity and higher spatial resolution
    2. BThe same sensitivity and resolution
    3. CHigher sensitivity and lower spatial resolution
    4. DHigher sensitivity and higher spatial resolution

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17. Question 17 · Medium

    A medium-energy collimator is needed for imaging with which radionuclide?

    1. AIodine-123
    2. BGallium-67
    3. CTechnetium-99m
    4. DFluorine-18

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18. Question 18 · Hard

    A Tc-99m eluate contains 1,850 MBq of Tc-99m. A lead-sleeve measurement shows 250 kBq of Mo-99. The limit is 0.15 kBq of Mo-99 per MBq of Tc-99m. What is the correct conclusion?

    1. AThe ratio is 0.74 kBq/MBq, which is above the limit, so reject it
    2. BThe ratio is 0.135 kBq/MBq, within the limit, so the eluate is usable
    3. CThe ratio is 1.35 kBq/MBq, which is above the limit, so reject it
    4. DThe eluate cannot be assessed without knowing the half-life used

    Answer and explanation in LearnFree account

19. Question 19 · Medium

    Tc-99m sulphur colloid localises in the liver, spleen and bone marrow mainly because of:

    1. APhagocytosis by cells of the reticuloendothelial system
    2. BGlomerular filtration followed by tubular secretion
    3. CActive secretion by hepatocytes into the bile
    4. DBinding to hydroxyapatite on bone surfaces

    Answer and explanation in LearnFree account

20. Question 20 · Hard

    The dose calibrator constancy check with a Cs-137 source gives an expected reading of 9.40 and today's reading is 8.90. The tolerance is plus or minus 5%. What should be done?

    1. AThe deviation is 5.3%, so the instrument fails and must be checked
    2. BThe deviation is 3.5%, which is acceptable for patient doses
    3. CThe reading is correct because the source decays quickly
    4. DThe deviation is 0.5%, which is acceptable for patient doses

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21. Question 21 · Medium

    A patient with suspected abdominal infection has had leucocytes labelled with a radionuclide that allows imaging at 24 hours. Which radionuclide fits?

    1. AIndium-111 (oxine)
    2. BRubidium-82 chloride
    3. CFluorine-18 fluoride
    4. DOxygen-15 water

    Answer and explanation in LearnFree account

22. Question 22 · Easy

    What is the physical half-life of technetium-99m?

    1. AAbout 66 hours
    2. BAbout 8 days
    3. CAbout 110 minutes
    4. DAbout 6 hours

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23. Question 23 · Medium

    A pinhole collimator is most useful for:

    1. AReducing the radiation dose given to the patient
    2. BImaging small organs such as the thyroid with magnification
    3. CImaging the whole chest of an adult in one field of view
    4. DWhole-body bone scans in adult patients with metastases

    Answer and explanation in LearnFree account

24. Question 24 · Hard

    A 370 MBq Ga-68 dose is prepared at 08:00. The half-life is 68 minutes. At 10:16, how much activity remains?

    1. AAbout 92.5 MBq
    2. BAbout 123 MBq
    3. CAbout 46 MBq
    4. DAbout 185 MBq

    Answer and explanation in LearnFree account

25. Question 25 · Medium

    A daily uniformity (flood-field) test is performed mainly to detect:

    1. AThe radiation dose that the patient will receive afterwards
    2. BThe physical half-life of the source used for the test
    3. CPhotomultiplier tube drift or a crystal or collimator defect
    4. DThe Mo-99 breakthrough level in the eluate of a generator

    Answer and explanation in LearnFree account