MEDICAL IMAGING

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MEDICAL IMAGING

• Dr. Hugh Blanton
• ENTC 4390

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Lecture 1

• EM Introduction

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Mass

• Mass?Measure of the resistance of a body to
  acceleration.
• eg.
• Newtons 2nd Law

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Mass

• kg (kilograms) is a lot of mass in the nuclear
  physics world.
• Define
• 1 atomic mass unit (amu) 1/12 mass of 1 atom of
  Carbon 12

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Energy

• Energy ?The ability to do work.
• For electrical forces

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Electron-Volt

• For 1 electron moving in a 1V potential
  difference,
• Define this as 1 electron-Volt (eV)

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Conservation of Mass

• c is the speed of light

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EM Radiation
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• Two ways to transfer energy from one body to
  another
• particlekinetic energy
• wavepropagation of a disturbance.
• EM radiation has properties of both of thesethe
  wave/particle duality.

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Waves

• Longitudinal wavesdisturbance in the direction
  of propagation.
• eg. sound

Animation courtesy of Dr. Dan Russell, Kettering
University
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• Transverse wavesdisturbance perpendicular to
  direction of propagation.
• eg. waves in the ocean

Animation courtesy of Dr. Dan Russell, Kettering
University
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• Regardless of the type of wave, they can be
  characterized by
• wavelength (l)
• frequency (f)
• phase (f)
• velocity (n)
• amplitude

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• Wave characteristics of EM radiation
• EM radiation can be seen to be a transverse wave
  of particular oscillations of electric and
  magnetic fields.

perpendicular magnetic field (force)
oscillatory electric field (force)
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• EM radiation has wave characteristics such as
• reflection
• refraction
• interference

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• Particle characteristics of EM radiation
• Particles of EM radiation are called quanta or
  photons.
• Photons can be thought of as wave packets of
  electric and magnetic fields

perpendicular magnetic field (force)
oscillatory electric field (force)
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• h is Plancks constant

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Example

• What is the frequency and l for 100 keV photons?

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• What is the frequency and l for 100 keV photons?

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EM Radiation
Low E, long lActs like wave.
High E, short lActs like particles.
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• Scientists have observed that electromagnetic
  radiation has a dual "personality."
• Besides acting like waves.
• It acts like a stream of particles (called
  "photons") that have no mass.
• The photons with the highest energy correspond to
  the shortest wavelengths.

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• Electromagnetic waves are produced by the motion
  of electrically charged particles.
• These waves are also called "electromagnetic
  radiation" because they radiate from the
  electrically charged particles.
• They travel through empty space as well as
  through air and other substances.