X-Ray Imaging Fundamentals

X-Ray Imaging Fundamentals

• Automatic Brightness Stabilization (ABS): Compensates for changes in tissue density.
• X-Ray Production: Bremsstrahlung and Characteristic interactions create x-ray photons at the anode.
• Spine Assessment: Full standing x-rays evaluate spinal curvature.
• Patient Communication: Describe sensations children might experience during procedures.
• Patient as Radiation Source: Patients can scatter radiation, especially during fluoroscopy.
• Jugular Notch Location: Located at the level of T2-T3 in sthenic patients.
• Digital Imaging System: Directly converts x-ray photons into electrical signals.
• Imaging Technology: Uses amorphous selenium (a-Se) and thin-film transistor (TFT) array.
• Non-Ionizing Interaction: Coherent scattering does not cause ionization.
• Vascular Access Catheters: Groshong and Hickman catheters.
• Distal Femur Lateral Projection: Knee flexion of 45 degrees required.
• kVp and mAs: kVp (kilovoltage peak) controls quality, mAs (milliampere-seconds) quantity.
• Inverse Square Law: Radiation intensity decreases with the square of the distance. This is crucial for dose calculations.

Photon Interactions with Matter

• Photoelectric Effect: High-energy photons are absorbed by the patient when interacting with a k-shell electron. This creates contrast. Lower photon energies are more likely to interact in this manner.
• Compton Scattering: Photons interact with outer shell electrons, are scattered, and lose energy. This produces scatter radiation, which is a source of image fog and occupational exposure..
• Coherent Scattering: Low-energy photons change direction without losing energy, and are not ionizing.
• Attenuation: Partial absorption of the x-ray beam as it travels through the patient. This is due to the differential absorption of different tissues in the body to the x-ray beam.

SI Units

• Absorbed Dose (Gy): Energy absorbed per unit mass.
• Dose Equivalent (Sv): Considers both absorbed dose and radiation quality. X-ray weighting factor is 1. High LET radiation will have a higher weighting factor.
• Exposure (C/kg): Measure of ionization in air.
• Effective Dose (Sv): Accounts for the different risks of exposure to various types of tissues (a weighted average), in terms of risk.
• Air Kerma (Gy): Kinetic energy released per unit mass in air.

Dose-Response Relationships

• Stochastic Effects: Increased probability of an effect, not severity. Increased dose equals increased probability of effects.
• Deterministic Effects: Increased severity of an effect, not probability. Increased dose equals increased severity of tissue reactions.
• LET (Linear Energy Transfer): Amount of energy transferred per unit length of tissue.

Radiation Bioeffects & Protection

• Radiation Exposure Thresholds: Some effects, like cataractogenesis, have a dose threshold below which they are not observed.
• Acute Radiation Syndrome (ARS): Hemopoietic, Gastrointestinal, Central Nervous System syndromes following high radiation doses..
• Dose Area Product Meter (DAP): Measures an area and gives a more precise area of dose exposure.
• ALARA Principle: As Low As Reasonably Achievable.
• Secondary Radiation: Scatter and leakage radiation.
• Attenuation: Describes changes in the x-ray beam as it passes through the patient.
• Photoelectric Interaction & Radiography: Photoelectric interaction produces contrast by absorption of photons.
• Compton Interaction & Fluoroscopy: Compton scattering creates scatter, which is relevant for occupational and patient dose in fluoro.
• Radioactive Units: Gray, Becquerel, Sievert.
• Linear Energy Transfer (LET): Varies between radiation types.
• Radiographer's Cumulative Exposure: 220 mSv for a 22-year-old radiographer.
• Public's Annual Effective Dose Limit: 1.0 mSv for frequent exposure. Different values apply for infrequent exposures.
• Protective Barriers: Secondary barriers must have certain minimum values.
• Scatter Beam Intensity: Scatter intensity is significantly less than the primary beam, particularly at longer distances.
• Inverse Square Law and Distance: The inverse square law shows a strong relationship between distance and radiation intensity.
• Source-Skin Distance (Fluoroscopy): Minimum 15 inches.

This quiz covers key concepts in X-ray imaging, including Automatic Brightness Stabilization, X-ray production methods, and the assessment of spinal curvature. It also explores the technology behind digital imaging systems and patient communication during procedures. Test your knowledge on various imaging techniques and their practical applications.