Medical Physics Overview

Medical Physics

• Medical physics is the field that overlaps medicine and physics, involving the application of physics to the function of the human body in health and disease, as well as the practice of medicine.
• The field of medical physics has several subdivisions, including:
  • Radiological physics: involves the application of physics to radiological problems, including the use of radiation in diagnosis and treatment.
  • Health physics: involves radiation protection of patients, workers, and the general public.
  • Medical electronics (medical engineering): deals with instruments used in monitoring body functions and diagnosis, as well as surgical aids.
  • Applications of x-ray and ultrasound in medicine.

Medical Physics Techniques

• Diagnostic techniques:
  • Tethoscope
  • Manometer (blood pressure)
  • Sphygmomanometer
  • Electrocardiograph (ECG)
  • Electroencephalograph (EEG)
  • Electromyography (EMG)
  • Thyroid function using I¹³¹
  • Computer tomography (CT scan)
  • Ultrasound
  • Tuning fork
  • Magnetic Resonance Imaging (MRI)
  • Flow meter
  • Spirometer (to study lung function)
  • Audiometer
  • Optics
  • Laser
  • Gamma camera (to study kidney, liver, and lung function)
• Therapy techniques:
  • Radiotherapy
  • High voltage
  • Ultrasound
  • Infrared
  • Radio frequency
  • Heating
  • Laser
• Patient monitoring techniques:
  • ECG
  • Spirometer
  • Blood pressure
  • Thermometer

Measurement

• Measurement is a key characteristic of science, and its growth is closely related to the ability to measure quantities of interest.
• In medicine, early efforts to measure quantities of chemical interest were often scorned as detracting from the skill of the physician.
• Examples of common measurements in medicine include:
  • Weight
  • Pulse
  • Temperature
  • Blood pressure
  • X-ray exposure
  • Radiation dose
  • Volume measurements

Forces on and in the Body

• Forces in the body:
  • Gravitational force (F=mg): responsible for the formation of varicose veins in the legs.
  • Electrical force: involves attractive and repulsive forces between static electrical charges and magnetic forces produced by moving electrical charges.
  • Nuclear force: includes strong and weak nuclear forces, which hold the nucleus together and are involved in electron decay.
• Forces on the body:
  • Statics forces: involve equilibrium, where the sum of forces in any direction is equal to zero, and the sum of torques about an axis is also equal to zero.
  • Dynamic forces: involve acceleration and deceleration, and are important when the body is moving and hitting another body.
  • Frictional forces: occur when a person is walking, and involve the transmission of force from the foot to the ground.

Levers in the Body

• The muscle and bone system of the body acts as levers, which can be classified into:
  • First class levers: where the fulcrum point is between the muscle force and the weight.
  • Second class levers: where the weight is between the fulcrum point and the muscle force.
  • Third class levers: where the muscle force is between the fulcrum point and the weight.

Examples of Forces

• Example 1: a person walking at 1 m/sec bumps into a wall and stops in 0.05 sec, developing a force of 1200 N.
• Example 2: a person walking at 1 m/sec hits their head on a steel beam, stopping in 0.5 cm in 0.01 sec, developing a force of 400 N. If the time is increased to 0.04 sec, the force developed is 100 N.
• Example 3: frictional forces occur when a person is walking, with a horizontal frictional component of force (Fv) and a vertical (normal) component of force (N) existing on the heel as it strikes the ground.