Introduction to Radiologic Physics and Electronics

Course Structure and Objectives

• First Semester Focus: The curriculum begins with some basic electronics, including the study of matter and energy. This material builds toward understanding the construction and function of the x-ray tube.
• Second Semester Focus: The latter half of the course covers how x-rays interact with matter (specifically the human body) and how they are produced.
• Physics Background: The instructor acknowledges that some students have previously taken physics while others have not. The content is designed to be accessible, and students are encouraged to seek help if the material becomes difficult.

Administrative Guidelines and Academic Performance

• Evaluation Criteria: Quizzes and exams are based directly on the PowerPoint slides and any information provided during class lectures. The instructor emphasizes that anything said in class is "fair game" for testing.
• Mathematical Requirements: The course only requires basic algebra. There is no trigonometry or calculus involved. Students struggling with algebra are encouraged to reach out for resources.
• Kahoot Sessions: The app Kahoot is used for game-based review sessions, usually the day before a quiz or exam.
  • Guideline: Many questions from the Kahoot sessions will appear on the quizzes.
  • Warning: The instructor strongly advises against studying only from Kahoot, noting that students who do so often fail. It should be used as a guideline and a way to get into the right "headspace," but the underlying material must be mastered.
• Student Engagement: Students are expected to read a few slides ahead before each class to facilitate discussion. The instructor finds lecturing to a non-interactive room boring and encourages questions, interaction, and even funny anecdotes.
• Academic Integrity: The instructor maintains a zero-tolerance policy for cheating, noting it is easy to catch and results in unpleasant consequences.

Ethics and Patient Care in Radiology

• Humanistic Approach: Every patient must be treated as a human being. The instructor emphasizes that one day, everyone will be on the receiving end of medical services.
• Professionalism vs. Apathy: Even on difficult work days, technicians should not be rude, indifferent, or apathetic toward patients.
• Personal Anecdote: The instructor shared a negative experience at "Start MRI" in Wayne. Despite suffering from a fractured $L5$ vertebrae and being in pain, the staff was apathetic and rude, making for a poor medical experience.
• Instructor Background: The instructor is not technically an employee of the school. He is employed by a consulting firm and has been in the medical field for over $30$ years. He provides services for the radiation oncology department downstairs and volunteers his time to teach this course for free as a way of "paying it forward."

Fundamental Principles of Energy and X-Ray Production

• Kinetic Energy Comparison: To explain how an x-ray tube works, the instructor uses the metaphor of throwing an object.
  • An object at rest has no energy. To make it move, energy must be added, giving it velocity ($v$).
  • Acceleration: Adding energy to an object causes it to accelerate.
  • Kinetic Energy Definition: The energy of motion.
• Energy Transfer Process:
  • Chemical energy from food is converted into mechanical energy by muscles/arms.
  • That energy is transferred to an object as kinetic energy.
  • When the object hits a target (like a board), the kinetic energy must be converted into other forms because it stops. These forms include sound waves, vibration of the board, and eventually heat dissipated into the environment.
• X-Ray Tube Operation:
  • Instead of a physical object like a gadget, the tube uses an electron (a fundamental particle).
  • The electron is accelerated within the x-ray tube and hits a target.
  • Conversion: Upon impact, some energy is converted into x-rays, but the vast majority of the energy is converted into heat.
  • Imaging: X-rays exit the tube and either pass through or are absorbed by the patient. They hit an imager (previously film, now an electronic digital imaging plate) behind the patient to create an image.
• Vehicle Analogy: The instructor compared energy transfer to a car crash. Accelerating a car gives it speed; hitting an object forces the energy to go somewhere, such as deforming the metal and squishing the vehicle components.

Standard Units of Measurement

• Metric System Usage: Science and medicine rely on standard units. Traditional units like pounds ($lb$), ounces ($oz$), and feet ($ft$) are generally not used, except occasionally by nurses for patient height and weight.
• Core Units:
  • Time: Measured in seconds ($s$).
  • Mass: Measured in grams ($g$) and kilograms ($kg$).
  • Length: Measured in meters ($m$) and centimeters ($cm$).
• Volume and Medication: Medications are measured in milliliters ($mL$), which is equivalent to grams ($g$) when discussing fluids. One should never use ounces for injections.
• Standard Clinical Distances: In the clinic, imaging plates are often placed at standard distances: $100\,cm$, $150\,cm$, or $180\,cm$.

The Critical Importance of Unit Specificity

• Mathematical Accuracy: Numbers on exams or in the field are meaningless without units. For example, being promised "$100$ an hour" to dig a ditch is unfavorable if the units are "pennies" rather than "dollars."
• Medical Safety: In medicine, specifying units is a matter of life and death. For nuclear imaging, stating an injection was "$6.2$" is insufficient and dangerous—it must be specified as curies, millicuries ($mCi$), or microcuries ($\mu Ci$).
• The Mars Polar Lander Case Study: This space probe crashed on Mars due to a unit conversion error. An American team provided calculations in miles and miles per second, while a European team assumed the units were kilometers and kilometers per second. This failure to specify units led to the total loss of the probe.
• Radiation Oncology Risks: In radiation oncology, using the wrong units or failing to pay attention can result in patient death. While rare, it is a serious reality of the field.

Scientific Prefixes in Radiography

• Common Prefixes:
  • Mega: ($10^6$)
  • Kilo: ($10^3$)
  • Centi: ($10^{-2}$)
  • Milli: ($10^{-3}$)
• Application in Physics: These prefixes are used to describe the energy of photons and x-rays.
  • Example: Instead of saying "$100,000$ electron volts," one would say "$100$ kilovolts" ($100\,kVp$) or "$100$ kiloelectron volts" ($100\,keV$).

Questions & Discussion

• Student Inquiry: The instructor invited questions throughout the session to encourage participation.
• Logistics: The instructor mentioned that he would email a copy of the materials to everyone and addressed a minor technical issue with a reading prompt not working correctly.