2Y03 Lecture 2, 2023 - Radiographic Imaging and Instrumentation I (PDF)

Radiographic Imaging and Instrumentation I Module 1 Unit 1.1: X-Ray Production & Image Quality Lecture 2: Radiation and the atom 1 • Radiation. • EM Radiation. • Atom • Binding Energy What are we doing today? Radiation Energy that travels through space or matter Diagnostic Imaging – 2 types:...

Radiographic Imaging and Instrumentation I Module 1 Unit 1.1: X-Ray Production & Image Quality Lecture 2: Radiation and the atom 1 • Radiation. • EM Radiation. • Atom • Binding Energy What are we doing today? Radiation Energy that travels through space or matter Diagnostic Imaging – 2 types: • Electromagnetic and Particulate Electromagnetic Radiation (EMR) Types of Electromagnetic (EM) radiation: ✴ visible light, radio waves and x-rays. • EM radiation has no mass • Vacuum – max. speed ≈ 3.0 x 108 m/s Electromagnetic Radiation (EMR) • EMR travels in straight lines. • EMR – wavelength (λ), frequency (f), and the energy per photon (E) • EMR spectrum 6 Electromagnetic Radiation (EMR) •Waves •Particle like units of energy called photons or quanta Electromagnetic Radiation (EMR): • Amplitude • Wavelength (λ) • Period • Frequency (f) Wave Characteristics Electromagnetic Radiation (EMR): Wave Characteristics c= λf • Wavelengths of x-rays and gamma rays = nanometers (nm) • 1 nm = 10-9 m • Frequency is expressed in Hertz (Hz) • 1 Hz = 1 cycle/sec = 1 sec-1 Electromagnetic Radiation (EMR): Particle Characteristics • EM radiation can exhibit particle like behaviour when interacting with matter. • Particle like bundles of energy = photons • Energy of a photon E = hf = hc/λ Electromagnetic Radiation (EMR): Particle Characteristics h (Planck’s constant) = 6.63 x 10-34 J/s = 4.15 x 10-18 keV/s When E is expressed in keV and λ in nm then: • E(keV) = 1.24/λ (nm) • Energies of photons → electron volts (eV) • 1 eV → is the energy acquired by an electron as it moves through a potential difference of 1 volt Electromagnetic Radiation (EMR): Particle Characteristics E = hf E = hc/λ If E is to be expressed in eV and λ in metres, then: E = 1.24 x 10-6/λ or 1.24/λ (nm) Electromagnetic Radiation (EMR): Questions??? The atom: Structural review • Smallest division of an element. • Nucleus • Shells or orbits = electrons • Radius of a nucleus ≈ 10-14m The atom: Name the element…… The atom: Distribution of Orbital Electrons • K, L , M ,N and so on……… • 2n2 , where n denotes quantum no. of the shell. • Deficit. • Atomic number and distance. The atom: Name the element…… The atom: Binding Energy • Energy required to remove an electron completely from the atom. • Incoming photon must have energy equal to or greater to remove an electron. • Electron from higher energy state falls down. The atom: Binding Energy Let’s look at tungsten (W) first and hydrogen (H) on the next slide • Z = 74 for W • K shell for W, Kb= -69,500 eV (To be ejected). • L shell for W, Kb= - 11,000 eV • 69,500 eV – 11,000 = 58,500 eV Bushberg Fig. 2-7 69,500 eV – Transition energy = EM radiation emitted The atom: Binding Energy Hydrogen, Z= 1 • K shell, Kb= -13.5 eV • L shell, Kb= -3.4 eV If K shell electron ejected, then: 13.5 eV – 3.4 eV = 10.1 eV Bushberg Fig. 2-7 (Transition energy) = EM radiation emitted • 2 types of radiation used in diagnostic imaging. • EM radiation. • Structure of the atom. • Binding energy. Summary Readings •Unit 1.1 in course manual • Chapter 1 and 2 – Bushberg • Chapter 1, 3 (pg. 36-47), 4 and 5 – Bushong