Influences anode heel effect and sourced to image distance.
Filtration
Inherent and added filtration were discussed.
Brief overview of compensation filters.
Introduction to Collimation
Definition of Collimation: Removal of x-rays from the x-ray beam to allow only a specific portion to reach the patient.
X-Ray Production Process
X-Ray Tube: X-rays produced isotropically (360 degrees).
Filters:
Inherent Filters: Glass envelope, conducting oil, and x-ray window.
Added Filtration: Metal sheets to further filter the beam.
Collimator: Machine that shapes the x-ray beam using lead sheets.
How Collimators Work
Lead Sheets: High atomic number, attenuate x-ray beam (photoelectric effect).
Field Size Adjustment: Parallel sheets of lead can move to adjust how many x-rays pass through.
Light Source:
Shines onto a mirror at 45 degrees.
Allows visualization of the x-ray field matching the collimated beam.
Visible light indicates the x-ray field area on the patient.
Benefits of Collimation
Reduces Patient Exposure: Less x-ray exposure to areas outside the field of interest.
Improves Image Quality:
Reduces scatter radiation, which creates noise in images.
Results in better spatial resolution and contrast.
Spectrum Impact:
Collimation does not change the energy spectrum of x-rays reaching the patient (unlike filtration).
Types of Collimators
Various shapes available:
Square and rectangular collimators.
Circular collimators and specialized shapes for specific x-ray types.
Next Steps in Learning
Upcoming discussion on the x-ray circuit:
Primary circuit, secondary circuit, and filament circuit.
Introduction to frame string and characteristic radiation production.
Conclusion
Collimation is a powerful tool for enhancing image quality while minimizing patient dose. Further understanding of the x-ray circuit will follow in the next lecture.