ESSENTIAL CONCEPTS OF RADIOLOGIC SCIENCE

I. Nature of Our Surroundings

Everything in the universe—what we see, touch, breathe—is composed of matter and influenced by energy. Radiology studies how energy (especially X-rays) interacts with matter (the human body).

II. Matter and Energy

Matter

  • Anything that has mass and occupies space.

  • Smallest unit: atom

  • States: solid, liquid, gas

  • In radiology, matter = patient tissues, equipment parts, shielding, etc.

Energy

  • The capacity to do work or cause change.

  • Forms:

    • Mechanical (movement)

    • Chemical

    • Electrical

    • Thermal

    • Nuclear

    • Electromagnetic (this includes X-rays)

Energy can convert from one form to another—this is what allows x-ray production.

III. Sources of Ionizing Radiation

Ionizing radiation = radiation with enough energy to remove electrons from atoms.
Sources:

Natural

  • Cosmic rays (from space)

  • Terrestrial radiation (radionuclides in soil)

  • Internal radionuclides (K-40 in the body)

  • Radon gas (the largest source)

Man-made

  • X-ray machines

  • Nuclear medicine

  • Consumer products (smoke detectors, older TVs)

IV. Discovery of X-rays

  • Discovered by Wilhelm Conrad Roentgen on November 8, 1895.

  • Observed fluorescence from a barium screen while experimenting with cathode rays.

  • He called them “X” because their nature was unknown.

This discovery began the field of diagnostic imaging.

V. Development of Modern Radiology

Key improvements:

  • Coolidge tube (1913) – stable x-ray tube design

  • CT (1970s)

  • MRI (1980s)

  • Digital radiography

  • Ultrasound advancements

  • Fluoroscopy modernization

Modern radiology shifted from static films to digital, faster, safer imaging with lower dose.

VI. Reports of Radiation Injury

Early radiologists did not use protection. Reported injuries:

  • Skin burns

  • Hair loss

  • Blood disorders

  • Cancers

  • Amputations
    These injuries led to the establishment of radiation safety standards.

VII. RADIATION PROTECTION

  • Modern radiation safety focuses on protecting patients because even low doses from routine X-rays can cause small but real long-term risks.

  • Fetuses (especially 1st trimester) are very sensitive to radiation.

  • As a student/technologist, you must learn to operate systems safely and avoid becoming too comfortable or complacent, because this leads to unnecessary exposure.

Always follow ALARA

ALARA = As Low As Reasonably Achievable
→ Reduce exposure by controlling:

  1. Time (shortest exposure possible)

  2. Distance (stay far from the source)

  3. Shielding (use protective barriers)

II. RADIATION PROTECTION DEVICES

1. Filtration

  • Metal filters (aluminum/copper) in the x-ray tube absorb low-energy x-rays.

  • These weak X-rays do not contribute to imaging but add to the patient's dose.

2. Collimation

  • Narrows the X-ray beam to the area of interest only.

  • Benefits:

    • Reduces radiation to nearby tissues.

    • Reduces scatter → better image contrast.

  • Light-locating collimators are most common.

3. Intensifying Screens

  • Films are placed between screens that emit light when exposed to X-rays.

  • Reduce patient dose by 95%, because light, not X-rays, exposes most of the film.

4. Protective Apparel

  • Aprons and gloves made of lead-impregnated material.

  • Used in fluoroscopy and some radiographic exams.

5. Gonadal Shielding

  • Protects ovaries/testes.

  • Used when:

    • Patient is of reproductive age.

    • Gonads are near the primary beam.

    • Shield does NOT interfere with the exam.

6. Protective Barriers

  • Control booth walls and windows are lead-lined.

  • Technologists remain behind them during exposures.

Important Patient Considerations

  • Avoid pelvic/abdominal x-rays during 1st trimester, unless necessary.

  • Avoid repeat exposures (they double the patient dose).

  • Use mechanical immobilizers; technologists should NEVER hold patients.

III. TEN COMMANDMENTS OF RADIATION PROTECTION

  1. Understand time, distance, and shielding.

  2. Avoid becoming complacent.

  3. Never stand in the primary beam.

  4. Always wear protective apparel when needed.

  5. Wear your radiation monitor at the collar, outside the apron.

  6. Never hold a patient; use devices or a family member.

  7. Holders must wear an apron and gloves.

  8. Use gonadal shielding when appropriate.

  9. Avoid pelvic imaging in pregnancy (especially first trimester).

  10. Collimate to the smallest field size.

VIII. Standard Units of Measurement

Physics uses three base quantities:

  1. Mass (kg)

  2. Length (m)

  3. Time (s)

Everything else is derived from them.

Derived Quantities

  • Volume → m³

  • Density → kg/m³

  • Velocity → m/s

  • Acceleration → m/s²

Special Quantities of Radiologic Science

Quantity

Traditional Unit

SI Unit

Exposure

C/kg

Air kerma (Gy_a)

Dose

J/kg

Gray (Gy_t)

Effective Dose

J/kg

Sievert (Sv)

Radioactivity

s⁻¹

Becquerel (Bq)

IX. BASIC MECHANICS

Mechanics: study of objects at rest (statics) and in motion (dynamics)

  1. Velocity (v)

How fast an object moves.
Formula:

v=dtv = \frac{d}{t}v=td​

Average Velocity Equation

Example:
A ball travels 60 m in 4 s.

v=15 m/sv = 15\ \text{m/s}v=15 m/s

  1. Average Velocity

vˉ=vo+vf2\bar{v}=\frac{v_o + v_f}{2}vˉ=2vo​+vf​​

Average Velocity Formula Physics

  1. Acceleration (a)

Rate of change of velocity.

a=vf−vota = \frac{v_f - v_o}{t}a=tvf​−vo​​

Acceleration Formula Isolated on White Stock Illustration ...

Example:
A dragster accelerates from 0 to 80 m/s in 10 s.

a=8 m/s2a = 8\ \text{m/s}^2a=8 m/s2

  1. NEWTON’S THREE LAWS OF MOTION

Law 1: Law of Inertia

  • An object stays at rest or moves in a straight line unless acted on by a force.

Law 2: Law of Force

F=maF = m aF=ma

  • Force is measured in newtons (N).

Law 3: Action–Reaction

  • Every action has an equal and opposite reaction.

  1. WEIGHT

Weight is a force caused by gravity pulling on mass.
Formula:

Wt=mgWt = mgWt=mg

  1. Momentum

  • Mass × velocity.

  1. Work

  • Force × distance.

    • W = Fd

  1. Power

  • Work per unit time.

    • P = W/t

  1. Energy

  • Ability to do work.

  • Measured in Joules.

  1. Heat

  • Energy is transferred due to a temperature difference.

  • Methods:

    • Conduction

    • Convection

    • Radiation

(Heat principles matter for X-ray tube cooling.)

X. Terminology for Radiologic Science

Common Numeric Prefixes

  • Milli- 10⁻³

  • Micro- 10⁻⁶

  • Kilo- 10³

  • Mega- 10⁶

  • Giga- 10⁹

Radiologic Units (again for clarity)

  • Gray (Gy) – absorbed dose

  • Sievert (Sv) – biological effect

  • Becquerel (Bq) – radioactivity

  • Air Kerma (Gyₐ) – exposure

XI. The Diagnostic Imaging Team

Radiologist

  • A medical doctor interprets images.

Radiologic Technologist (RadTech)

  • Performs imaging procedures safely and accurately.

Radiology Nurse

  • Assists with patient care, contrast administration.

Medical Physicist

  • Oversees equipment quality and radiation safety.

Radiographer Assistant / Support Staff

  • Helps with positioning, workflow, and clerical tasks.

Team goal: accurate diagnosis with minimal radiation dose.

IMPORTANT HISTORICAL DATES IN RADIOLOGY

(Key highlights only)

  • 1895 – Roentgen discovers X-rays

  • 1901 – Roentgen receives the first Nobel Prize

  • 1913 – Coolidge hot-filament x-ray tube

  • 1921 – Potter-Bucky grid

  • 1928 – Roentgen defined

  • 1948 – Image intensifier

  • 1973 – First CT system developed

  • 1973 – First MRI image

  • 1982 – PACS introduced

  • 1990 – Helical CT

  • 2000s–2020s – Rapid advancements in CT, DR, PET, MRI