Technique Chapter 1

Chapter 1: Radiation and Its Discovery

Objectives

• Describe the discovery of X-rays: Overview of events leading to x-ray discovery.

• Understand dual nature of x-ray energy: Explanation of x-rays behaving both like waves and particles.

• Characteristics of electromagnetic radiation: Key traits of EM radiation to be identified.

• Units of measurement for radiation: Different quantification methods and their differences will be detailed.

• Properties of x-rays: Fundamental characteristics explaining their behavior and usage.

• Fundamentals of radiation protection: Essential practices for protection from radiation.

Discovery of X-rays

• Date and Discoverer: X-rays discovered on November 8, 1895, by Dr. Wilhelm Conrad Roentgen.

• Nature of Discovery: Accidental; Roentgen observed effects on photographic plates.

• First Radiograph: Notable for the first radiograph taken of Mrs. Roentgen's hand.

• Recognition: First Nobel Prize for Physics awarded to Roentgen in 1901.

• Public Perception: Initially viewed as a novelty; it wasn't until 1898 that harmful effects of X-rays became known.

Skin Damage

• Skin Erythema: Condition referring to reddening and burning of the skin resulting from exposure to radiation.

X-rays as Energy

• Definition: X-rays are a form of electromagnetic radiation.

• Behavior: Exhibits dual nature behaving both as waves and particles.

  • Wave properties:

    • Wavelength: Distance between successive points in a wave.

    • Frequency: Number of wave cycles passing a point in a unit time; inversely related to wavelength.

  • Particle properties: Moves as photons representing energy packets.

The Electromagnetic Spectrum

• Spectrum Types:

  • Radio Waves: Used for broadcasting radio and television.

  • Microwaves: Utilized in cooking, radar, and various signals.

  • Infrared: Transmits heat from natural and man-made sources.

  • Visible Light: Allows for visual perception.

  • Ultraviolet: Absorbed by the skin, used in fluorescent tubes.

  • X-rays: Enables viewing of bodies and objects; important in medicine.

  • Gamma Rays: Employed in cancer treatment by killing cells.

Radiation Units of Measurement

• Systems Used: Two systems for quantifying radiation include conventional and international (SI).

• Units Comparison:

  • Exposure:

    • Conventional: Roentgen (R)

    • SI: Air kerma (Gy)

  • Absorbed dose:

    • Conventional: Radiation absorbed dose (rad)

    • SI: Gray (Gy)

  • Dose equivalent:

    • Conventional: Radiation equivalent in man (rem)

    • SI: Sievert (Sv)

  • Radioactivity:

    • Conventional: Curie (Ci)

    • SI: Becquerel (Bq)

Exposure

• Definition:

  • Roentgen (R): Measures ionization in air, indicating intensity of radiation.

  • Air kerma: Measures energy deposited in mass of air, in gray (Gy).

• Common Units: Exposure often expressed in smaller units, where 1 R = 1000 mR and 1 Gy = 1000 mGy.

Absorbed Dose

• Definition: Measures radiation energy transfer into matter (e.g., tissue).

  • Conversions:

    • 1 rad = 100 ergs per gram.

    • 1 gray (Gy) = 1 joule absorbed per kilogram.

    • 1 Gy = 100 rads.

    • Conversion factor: 0.01 heats rads to grays.

Dose Equivalent

• Purpose: Measured for occupational radiation exposure.

  • Units of measure:

    • Rem and Sv are used, derived from absorbed exposure multiplied by quality factor.

    • X- and gamma rays have quality factor of 1, equating rads to rem.

    • Conversion: 1 rad (0.01 Gy) = 1 rem (0.01 Sv).

Radioactivity

• Definition: Instability in atoms causes particles/energy emission from the nucleus (radioactive disintegration).

• Measurement Units:

  • Curie and Becquerel: Measure rates of nuclear decay.

• Half-life: Time needed for activity to drop to 50% of initial value.

• Radioisotopes: Used in nuclear medicine and radiation therapy.

Properties of X-rays

• Characteristics:

  • Invisible, electrically neutral, no mass, travel at light speed in vacuum.

  • Can’t be focused optically and forms polyenergetic beams.

  • Travel straight and can penetrate tissues, causing fluorescence and chemical changes in films.

  • Can produce secondary radiation and cause biological damage.

Fundamentals of Radiation Protection

• Principle: Minimize radiation dose utilizing ALARA (As Low As Reasonably Achievable) Principle.

  • Safety Practices:

    • Limit exposure time, maintain safe distance, maximize shielding.

    • Control size of x-ray exposure field.

    • Optimal combination of kVp (quality) and mAs (quantity) for diagnostic efficacy while reducing exposure.

    • Avoid unnecessary duplicate exams and screen for pregnancy.

    • Consistent mental checklist before radiographic procedures.