Medical Imaging | OCR A-Level Physics A (H556)
Medical Imaging
- 82 questions
- 8 subtopics
- Module 6: Particles and medical physics
- Paper 2 and Paper 3
Physics applied to diagnosis: how X-rays are produced and attenuated, CAT scanning, the gamma camera and PET, and ultrasound including the Doppler technique..
It covers the X-ray tube, x-ray attenuation and imaging, cAT scanning, medical tracers and the gamma camera, pET scanning, ultrasound and the piezoelectric transducer, acoustic impedance and reflection and doppler ultrasound.
Sample questions from Medical Imaging
Answer each one closed book first, then open the answer.
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The X-ray tube
What is the function of the anode in an X-ray tube?
Show the answer
The anode is a positive electrode that accelerates electrons towards the target metal. -
X-ray attenuation and imaging
What is pair production in the context of X-ray attenuation?
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A high-energy photon converts into an electron-positron pair near a nucleus. -
CAT scanning
What is the role of computer software in a CAT scanner?
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It processes detector signals to reconstruct cross-sectional images. -
Medical tracers and the gamma camera
What is the role of the scintillator in a gamma camera, and what material is typically used?
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The scintillator is a crystal (typically sodium iodide) that converts incoming gamma photons into flashes of visible light. -
PET scanning
What happens to a positron emitted from a tracer in PET scanning before detection occurs?
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The positron travels a short distance before encountering an electron, resulting in annihilation. -
Ultrasound and the piezoelectric transducer
How does an ultrasound transducer emit ultrasound waves?
Show the answer
An electrical potential is applied to a piezoelectric crystal, causing it to deform and vibrate, producing ultrasound waves. -
Acoustic impedance and reflection
What happens when ultrasound meets a boundary between two media with different acoustic impedances?
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Partial reflection of the ultrasound occurs at the boundary. -
Doppler ultrasound
In the Doppler ultrasound equation, what does the angle θ represent?
Show the answer
The angle between the ultrasound beam direction and the direction of blood flow.
The 8 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| The X-ray tube | Recall questions on the heated filament, target and accelerating potential difference, and how X-ray photons are produced. | 8 |
| X-ray attenuation and imaging | Recall questions on simple scatter, the photoelectric effect, Compton effect and pair production, the attenuation equation I = I₀e^(−μx), how intensity falls through an absorber, and barium and iodine contrast media. | 11 |
| CAT scanning | Recall questions on how a CAT scanner collects and reconstructs X-ray data, and its advantages over conventional X-ray images for depth, soft tissue contrast and small density differences. | 8 |
| Medical tracers and the gamma camera | Recall questions on technetium-99m as a tracer, the collimator, scintillator, photomultiplier tubes and computer of a gamma camera, diagnosing organ function, and the costs of expensive scanners. | 12 |
| PET scanning | Recall questions on positron-electron annihilation, fluorine-18 tracers, 511 keV gamma photons, coincidence detection and lines of response, forming PET images, uses in cancer and neurology, and cyclotron supply. | 14 |
| Ultrasound and the piezoelectric transducer | Recall questions on the piezoelectric effect, ultrasound frequencies, how a transducer emits and detects ultrasound, and A-scans and B-scans. | 11 |
| Acoustic impedance and reflection | Recall questions on Z = ρc, the fraction of intensity reflected at a boundary, and why a coupling gel is needed. | 10 |
| Doppler ultrasound | Recall questions on the Doppler effect in ultrasound, the Doppler equation for blood speed with calculations, the factor of 2 and why the beam must be angled to the blood flow. | 8 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
OCR A-Level Physics A Active Recall Guide
Every topic, not just this one. 1,862 questions with their answers.