Medical Physics Overview

Study Notes

Objective learning goals include Medical Physics, Physical Therapy, Health Physics, Modeling, and Homeostates.
Other learning objectives include: measurement, measurements of repetitive processes, measurements of nonrepetitive processes, accuracy & precision, and false positives and false negatives.

Medical Physics examines the forces within the body during activities, the body's work output, the relationship between EKG signals and the heart, how X-rays work, and the amount of radiation received from X-rays.
This subject covers the applications of physics to medicine.
Physics plays a role in medicine, but isn't as obvious as chemistry or biology's role.
Medical Physics has two main areas of study: the function of the human body and the practice of medicine.
It involves topics such as the physics of organ systems (eyes, ears, lungs, heart, circulation), stethoscopes, percussion, medical use of lasers, ultrasound, radiation, mechanics, heat, light, sound, electricity, and magnetism.

Physical therapy uses physical agents (like manipulation, massage, exercises, heat, and water) to diagnose and treat injuries and diseases.
This branch of medicine focuses on non-drug therapies for illness.

Medical physics is a sub-discipline of biophysics.
The scope of biophysics is broader, not limited to medicine.
It focuses on the physics of various organisms (including microbes) and overlaps with medical physics in areas like cellular transport.
Broad subdivisions include radiologic physics, radiation protection for patients, staff, and the public, and sometimes called health physics

Physicists believe the physical world is governed by laws, although the mathematical description can be too complex, especially in the human body.
Analogies (like comparing the eye to a camera) are commonly used to clarify complex biological systems.
Model simplification is common where real situations are usually more complex than the simplified models.
Some models, like comparing blood flow to electricity flow, involve seemingly unrelated phenomena.

A core characteristic of science is reproducible measurement of quantities of interest.
The growth of scientific understanding is often linked to improvements in measurement accuracy.
In the past, measurement was sometimes seen as less important than clinical skill; however, accurate measurement is now increasingly valued.
Common medical measurements have improved in accuracy and reproducibility over time.

X-rays give qualitative information about the inside of the body but may look different with different machines.
Pulse rate is approximately 70 per minute, and breathing rate is around 15 per minute.
Repetitive measurements (like pulse) often involve the number of repetitions per unit of time.

Accuracy refers to how close a measurement is to the accepted standard.
Precision refers to the reproducibility of a measurement.
Example: A person's height measured as 1.765 meters may be accurate to 0.003m.
Example: Temperature measurements of a patient taking 10 readings varied by 0.2 degrees, showing good precision.

Measurements can introduce errors.
The process of measurement (like blood pressure) can introduce uncertainty.
Patient characteristics (a woman vs a man) or other factors (appearance) may influence measurements
Measurement errors can sometimes lead to incorrect diagnoses.
Examples include false positives (incorrect diagnosis of a disease), false negatives (failing to diagnose a disease), and misleading laboratory values.
Research, new tests, better instruments, attention to accuracy during a measurement, and repeating measurements can reduce these errors.