Medical Physics: Terminology and Basics

Terminology, Modeling, and Measurement in Medical Physics

• Terminology is the science of terms, and medical physics is a term that overlaps two fields: medicine and physics.
• Medical physics concerns the study of various fields of physics in the body, including:
  • Physical parameters that affect the body, such as pressure, force, energy, power, and electricity.
  • The physics of body organs and systems, such as vision, hearing, skeletal, pulmonary, cardiovascular, and nervous systems.
  • Applications of physics in medicine, including laser, sound, and ultrasound, X-rays, CT scans, MRI, ECG, EEG, and radioisotopes.

Standard and Non-Standard Units in Medicine

• Standard units are used to measure quantities in medicine, such as force in newtons, work in joules, and power in watts.
• Non-standard units are special units used in medicine, such as mmHg or cmHg for pressure, and kilocalorie or calorie for energy.

Repetitive and Non-Repetitive Measurements

• Repetitive measurements are quantities that are repeated at regular intervals, such as heart rate, breathing rate, and electrical signals from the brain.
• Non-repetitive measurements are quantities that are not repeated uniformly, such as the time it takes for the kidney to remove waste from the blood, food digestion, and nerve signals.

Accuracy of Measurement

• Measurements in medicine should be very accurate to avoid risky results.
• Measurement errors can occur due to instrumentation, technical, or psychological reasons.
• Inaccurate measurements can lead to false negative or false positive errors, which can have serious consequences.

Reducing Diagnostic Errors and Measurement Uncertainties

• Ways to reduce errors and uncertainties include:
  • Researching causes of misleading laboratory test values.
  • Repeating measurements.
  • Taking care when taking measurements.
  • Developing new clinical tests.
  • Improving instrumentation.
  • Using reliable instruments.
  • Calibrating instruments relative to standard or already calibrated instruments.

Medical Measurements and Treatment

• Medical measurements that physicians should take before deciding on treatment include:
  • Routine measurements, such as body temperature, pulse rate, blood pressure, and body weight.
  • Other required tests, such as laboratory investigations, body signals investigations, and machinery measuring instruments.
  • Specialized measurements, such as sound, light, and laser applications in medicine.

Applications of Physics in Medicine

• Sound in medicine:
  • General properties of sound.
  • The stethoscope.
  • Ultrasound pictures of the body.
  • Ultrasound to measure motion.
  • Physiological effects of ultrasound in therapy.
• Light in medicine:
  • Measurement of light and its units.
  • Applications of visible light in medicine.
  • Applications of microscopes in medicine.
• Physics of the eyes and vision:
  • Defective vision and its correction.
  • Instruments used in ophthalmology.
• Laser applications in medicine:
  • Generation of laser light.
  • Applications to medicine.
• Physics of diagnostic X-rays:
  • Production of X-ray beams.
  • How X-rays are absorbed.
  • Fluoroscopy.
  • CT scans.
• Physics of nuclear medicine:
  • Units of radioactivity.
  • Basic instrumentation of nuclear medicine.
  • Radiation doses in nuclear medicine.
• Physics of radiation therapy:
  • Dose units in radiotherapy.
  • Principles of radiation therapy.
• Radiation detection:
  • Biological effects of ionizing radiation.
  • Radiation protection in radiation therapy.
  • Magnetic resonance imaging (MRI).