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  1. 1. MEDICAL IMAGING Nada Fitrieyatul Hikmah
  2. 2. Why Medical Imaging? • Motivation: Need to “see” inside the body • Options: ✓ Open the body and take a look (most invasive) ✓ Endoscopic cameras (minimally invasive) ✓ Medical imaging (noninvasive) • Goal: To assist with identifying and/or diagnosing medical conditions
  3. 3. Medical Imaging Theory Every medical imaging system can be thought of as a black box that transmits energy into the body and then receives energy out of the body and does something with that energy to make an image. ❑ What kind of energy? ❑ What are the effects on the body? ❑ What are the effects on the image?
  4. 4. Timeline of Medical Imaging • 1895 – First X-ray image (Roentgen) • 1950s – Ultrasound Imaging (Ludwig, Wild, etc.) • 1971 – Magnetic Resonance Imaging, i.e. MRI (Damadian) • 1972 – X-ray computed tomography, i.e. CT (Hounsfield & Cormack)
  5. 5. Visualizing the heart with… • Here are the four primary imaging methods that can be used to see the heart. • Each one of these images have advantages and disadvantages.
  6. 6. Imaging System Resolution • Temporal resolution ➔ how fast an image can be recorded? (Ultrasound is the best temporal resolution) • Spatial resolution ➔ how blurry an image will be? ➔ The ability to resolve two points in space. • The worst spatial resolution = x- ray • The best spatial resolution = MRI
  7. 7. Visualizing the heart with… • The worst spatial resolution = x-ray ➔ it looks more blurry. • The best spatial resolution = MRI ➔ we can see borders between different chambers. • Ultrasound is the best temporal resolution ➔ we can see things in real time.
  8. 8. X-RAY IMAGING Nada Fitrieyatul Hikmah
  9. 9. Outline • What are x-rays? • How are they created? • How do they interact with our body? • Safety requirements • Example of Uses • Advantages and disadvantages
  10. 10. Cost Comparison • Q: What is the cheapest medical imaging modality available for doctors to visualize internal structures non-invasively? • A: X-rays are the cheapest and most widely used form of medical imaging.
  11. 11. The Genesis of Projection X-Rays • 1895: First discovered by Professor Wilhelm Roentgen ➔ Soon afterward, Roentgen used x-rays to image his wife’s hand. • 1896: First diagnostic x-ray used to show the fractured wrist of Eddie McCarthy. • 1901: Roentgen won the first Nobel Prize in Physics for this discovery.
  12. 12. Electromagnetic (EM) Radiation • X-rays are a form of electromagnetic radiation. • EM radiation is energy that exhibits wave-like behavior as it travels through space. • EM radiation is carried by “particles” known as photons.
  13. 13. Various Forms of EM Radiation
  14. 14. Atomic Structure • Atom contains three main components: electrons (gray), protons (red), and neutrons (blue). • Electrons orbit the nucleus of the atom and are negatively charged. • Protons form part of the nucleus and are positively charged. The total number of protons defines the type of atom (or element). • Neutrons form the remainder of the nucleus. Which element is represented here??
  15. 15. Electron Structure • Electrons orbit the nucleus in different shells (e.g., K, L, M) • The K shell is closest to the nucleus.
  16. 16. Ionization • Ionization ➔ The process of knocking an electron out of an atom (e.g. with EM radiation) to form an ion. • Each one of dots or represent electrons orbiting nucleus of the atom ➔ then comes EM radiation ➔ then knock the element out of its shell ➔ becomes free electron. • What is the charge of this ion?
  17. 17. Ionization Energy • Mininum energy required to ionize an atom. ❑ The msaller atoms are really close to that positively charged nucleus and they want to remain neutral. ❑The smaller atoms have a higher ionization energy than the larger atom.
  18. 18. X-ray interactions with matter • X-rays interact with electrons by knocking them out of the atom (i.e. ionizing radiation). X-ray interact with matter in 3 primary ways :
  19. 19. Compton Scattering • X-rays scatter with longer wavelengths than the incident x-ray. • Shift in wavelength increases with scattering angle, according to the Compton formula:
  20. 20. Where do x-rays come from? • X-rays come from an x- ray tube. • X-ray tubes are typically made of glass and have some heated filaments.
  21. 21. X-ray Tube • X-ray tube has cathode and some electrical wires to heat up the electrons on the cathode then smash into the anode ➔ generate some x-rays by generating the EM radiation from the high-speed electrons then slam to anode plate.
  22. 22. X-ray Imaging (1)
  23. 23. X-ray Imaging (2)
  24. 24. X-ray Imaging (3)
  25. 25. X-ray Imaging (4)
  26. 26. X-ray Imaging (5)
  27. 27. Jones Fracture • Avulsion of the 5th proximal metatarsal. • Occurs due to a sudden force under the foot, such as when landing from a high jump on to another player’s foot when playing basketball.
  28. 28. Bone Fracture Classifications • Simple ➔ the skin remains wholly intact. • Compound ➔ fractured bone breaks the skin.
  29. 29. Dental Radiography • Used to diagnose cavities, hidden molars, etc. • The x-rays are coming from outside of your mouth and the film in inside your mouth.
  30. 30. Mammography
  31. 31. Adverse Effects of Ionizing Radiation • A single ionizing radiation emission can ionize many atoms along its path. • An ion’s electrical charge can lead to unnatural chemical reactions inside cells. ❑ Broken DNA chains ❑ Apoptosis (cell death) ❑ Mutations (can cause cancer) • X-rays are used sparingly today because of these risks.
  32. 32. Radiation Dose and Dose Rate (1) Risk of harm depends on the dose and the dose rate (the time the body is exposed to radiation).
  33. 33. Radiation Dose (2)
  34. 34. Radiation Dose (3)
  35. 35. Radiation Dose (4)
  36. 36. Geiger Counter • How do we know how much dose we’re getting? • Geiger Counter ➔ Registers how much the gas it contains get ionized by incoming particles of radiation and converts that information into an electronic signal.
  37. 37. X-ray Protective Equipment
  38. 38. X-ray Pros and Cons Advantages : • Relatively inexpensive • Can identify bone structures Disadvantages : • Poor soft tissue contrast • Birth defects (if used to image pregnant women) • Radiation poisoning at high dose with long exposure times-induced cancers • Effects are negligible when imaging for bone fractures because the required radiation doses are low with short exposure times.