A LevelPhysicsOCRExam Questions6. Particles & Medical Physics6.12 Diagnostic Methods in Medicine

Diagnostic Methods in Medicine (OCR A Level Physics)

Exam Questions

28 mins4 questions
Easy
Medium
1a2 marks

The medical tracer technetium-99m is used in imaging organs such as the brain.

a)
Explain the advantages of using technetium-99m for this purpose.

[2]

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1b3 marks
b)
A gamma-camera uses powerful computers and sophisticated software to produce three- dimensional images of the patient’s organ.

Name and describe the remaining three main components of the gamma camera.

[3]

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1a4 marks

Fluorine-18 is a common radioactive isotope used in positron emission tomography (PET).
Fluorine-18 emits positrons. A patient is injected with a radiopharmaceutical containing fluorine-18.

a)
Describe how a PET scanner is used to locate an area of increased activity within the patient.

[4]

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1b3 marks
b)
The half-life of fluorine-18 is 110 minutes.

Calculate the time t in minutes for the activity of the radiopharmaceutical to decrease to 30% of its initial activity.





t = ................................... minutes [3]

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1c1 mark
c)
PET scanners are not available in all hospitals. This is because fluorine-18 requires expensive on-site particle accelerators and fluorine-18 has a very small ‘shelf-life’.
Suggest the impact this may have on the treatment and diagnosis of patients in the country.

[1]

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24 marks

The medical tracer fluorine-18 is used in positron emission tomography (PET).
Fluorine-18 is a beta-plus emitter with a short half-life.

Describe how the fluorine-18 nuclei are located in a patient using a PET scanner.

[4]

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3a7 marks
a)
The nuclear reaction below shows how the isotope of fluorine-18 (straight F presubscript 9 presuperscript 18) is made from the isotope of oxygen-18 (straight O presubscript 8 presuperscript 18).



straight O presubscript 8 presuperscript 18 space plus space straight p presubscript 1 presuperscript 1 space rightwards arrow space straight F presubscript 9 presuperscript 18 space plus space straight n presubscript 0 presuperscript 1 space plus space straight gamma

The oxygen-18 nucleus is stationary and the proton has kinetic energy of 0.25 × 10−11 J.
The binding energy of the straight O presubscript 8 presuperscript 18 nucleus is 2.24 × 10−11 J and the binding energy of the straight F presubscript 9 presuperscript 18nucleus is 2.20 × 10−11 J. The proton and the neutron have zero binding energy.

i)
Explain why a high-speed proton is necessary to trigger the nuclear reaction shown above.


 [2]
ii)
Estimate the minimum wavelength straight lambda of the gamma ray photon (straight gamma).

straight lambda = ..................................................... m [3]

iii)
Fluorine-18 is a positron emitter.
Name a medical imaging technique that uses fluorine-18 and state one benefit of the technique.


 [2]

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3b4 marks
b)
Describe how the components of a computerised axial tomography (CAT) scanner can produce high-quality images of the internal structures of a patient.
[4]

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