Medical Physics

What Medical Physics covers

Medical Physics is examined in Unit A2 3, Medical Physics — examined, one of three optional units (Single Award takes one, Double Award two). It covers body temperature and clinical thermometers, blood pressure readings and the sphygmomanometer, heart activity experiments and EEG traces, X-ray tubes, radiographs and CT scans, flexible endoscopes, optical fibres and lasers, ultrasound A-scans, B-scans and acoustic impedance, MRI scanning and gamma camera imaging, alpha, beta and gamma radiation and half-life and Radiopharmaceuticals, radiotherapy and radiation protection.

The 9 subtopics

Each one has its own page.

• Body temperature and clinical thermometersNormal core temperature, digital, infrared ear, forehead, liquid-in-glass and strip thermometers, thermistors, choosing a thermometer, hypothermia, fever and the narrow survivable range.Open →
• Blood pressure readings and the sphygmomanometermmHg and kPa conversion, Korotkoff sounds, mercury, aneroid and digital sphygmomanometers, cuff size and reliable readings, white coat hypertension, low readings and pulse pressure.Open →
• Heart activity experiments and EEG tracesPulse sensors and dataloggers, ECG voltage, interference and a heart rate calculation, EEG alpha, beta, theta and delta waves, spike-and-wave patterns, and EEG changes in injury and disease.Open →
• X-ray tubes, radiographs and CT scansThe cathode, high voltage, tungsten anode, rotation, vacuum, casing, collimator and filter of an X-ray tube, maximum photon energy, radiograph contrast, half-value thickness and CT scanning.Open →
• Flexible endoscopes, optical fibres and lasersTotal internal reflection and cladding, a worked critical angle, coherent and incoherent bundles, endoscope channels and tools, lasers in surgery, keyhole surgery and cleaning endoscopes.Open →
• Ultrasound A-scans, B-scans and acoustic impedanceUltrasound frequencies and probes, specific acoustic impedance and the intensity reflection coefficient with worked values, coupling gel, A-scans and B-scans, echo depth, frequency choice and wavelength.Open →
• MRI scanning and gamma camera imagingWhat MRI detects, its magnet, radio-frequency pulses and gradient coils, tissue contrast, safety and drawbacks, and the collimator, scintillator and photomultipliers of a gamma camera.Open →
• Alpha, beta and gamma radiation and half-lifeAlpha, beta and gamma radiation and their dangers, ionisation, activity and decay constant, physical half-life, measuring protactinium half-life, modelling decay with dice, and worked decay calculations.Open →
• Radiopharmaceuticals, radiotherapy and radiation protectionExternal beam radiotherapy and fractionation, brachytherapy, iodine-131, tracers and technetium-99m, rubidium-82 and PET, thallium-201, effective half-life, dosimeters and protection, and background correction.Open →

What you need to know

Answer each one before you reveal it.

Take Medical Physics further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Physical half-life vs Biological half-life

  Physical half-life: time for the activity of a radioactive sample to fall to 50% of its starting value. Biological half-life: time for natural metabolic processes to clear 50% of a substance from the body.

• Coherent bundle vs Incoherent bundle

  Coherent bundle: fibres kept in matching positions at both ends so that a picture is carried. Incoherent bundle: fibres arranged randomly that deliver light but cannot carry a picture.

• A-scan vs B-scan

  A-scan: ultrasound display of echo spikes against time along one line. B-scan: ultrasound display building a two-dimensional picture from dots of varying brightness.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What is the normal core body temperature of a healthy adult?

   Model answer

   Normal core body temperature is about 37 °C. A healthy reading usually lies between about 36.5 °C and 37.5 °C.

2. 2

   Why does a temperature taken in the armpit usually read lower than core temperature?

   Model answer

   The armpit is a skin site that loses heat to the surroundings. An armpit reading is typically about 0.5 °C below core temperature.

3. 3

   How does a digital clinical thermometer measure temperature?

   Model answer

   A digital thermometer has a thermistor in its tip, whose resistance changes with temperature. A circuit converts the resistance into a temperature shown on a display.

4. 4

   How does the resistance of a thermistor change as it warms?

   Model answer

   The resistance of a negative temperature coefficient thermistor falls as its temperature rises. A small temperature change gives a large, easily measured change in resistance.

5. 5

   How does an infrared ear thermometer work?

   Model answer

   An infrared ear thermometer detects the infrared radiation emitted by the eardrum. A hotter eardrum emits more infrared, and a sensor converts the reading into a temperature.

6. 6

   Why is the eardrum a good site for estimating core temperature?

   Model answer

   The eardrum shares its blood supply with the hypothalamus, the brain's temperature control centre. Eardrum temperature therefore closely follows core temperature.

What is inside Levo

Six ways to work the same material.

Medical Physics revision questions

What does Medical Physics cover in CCEA A-Level Life and Health Sciences?

9 subtopics: body temperature and clinical thermometers, blood pressure readings and the sphygmomanometer, heart activity experiments and eeg traces, x-ray tubes, radiographs and ct scans, flexible endoscopes, optical fibres and lasers, ultrasound a-scans, b-scans and acoustic impedance, mri scanning and gamma camera imaging, alpha, beta and gamma radiation and half-life and radiopharmaceuticals, radiotherapy and radiation protection. Each one has its own page with questions and model answers.

How is Medical Physics organised?

By the CCEA 0008 specification, subtopic by subtopic, so it matches the order you are taught it in.