Factors affecting X-ray beam Flashcards
What is X-ray beam quality?
Quality refers to the penetrating ability (average energy) of the X-ray beam.
How is X-ray beam quality measured.
Half-Value Layer (HVL) – Thickness of material needed to reduce beam intensity by 50%.
Peak kilovoltage (kVp) – Higher kVp = more penetrating beam.
Application in Medical Imaging:
Higher kVp is used for thicker body parts (e.g., abdomen) to ensure penetration, while lower kVp is used for soft tissues (e.g., chest).
What is X-ray beam quantity, and how is it controlled?
Quantity refers to the number of X-ray photons in the beam.
Controlled by mAs (milliampere-seconds), the product of tube current (mA) and exposure time (s).
How does mA affect X-ray beam intensity and quality?
mA increases the number of electrons hitting the target, increasing photon quantity (intensity).
Does not change photon energy (quality).
Application in Medical Imaging:
Higher mA = brighter image with less noise (better for dense tissues). Must balance with patient dose.
How is x-ray beam quantity applied to medical imaging.
- Increasing mAs improves image brightness and reduces noise but increases patient dose.
- Used to optimize image clarity (e.g., higher mAs for obese patients).
How does kVp influence X-ray beam quality and intensity?
kVp determines the maximum photon energy (quality): Higher kVp = more penetration.
Also increases intensity (more photons produced).
Application in Medical Imaging:
High kVp (e.g., 120 kVp) for chest X-rays (penetrates lungs); low kVp (e.g., 60 kVp) for extremities (better soft-tissue contrast).
How does target material affect X-ray production?
Higher atomic number (e.g., Tungsten) = more efficient X-ray production (higher intensity).
Affects energy spectrum (quality).
Application in Medical Imaging:
Tungsten targets are standard due to high efficiency and heat tolerance, optimizing image quality.
What is the effect of rectification on X-ray beam quality and intensity?
Increases mean photon energy (harder beam, better quality).
Boosts intensity (more consistent X-ray output).
How is rectification applied in medical imaging
Reduces patient dose by eliminating low-energy photons and shortens exposure time (less motion blur).
How does filtration impact X-ray beam quality and intensity?
Removes low-energy photons, improving beam quality (more uniform penetration).
Reduces intensity (fewer total photons).
How is filtration applied in medical imaging.
Aluminum filters are used to reduce skin dose (by removing non-penetrating photons) while maintaining diagnostic image quality.
intensity
is the rate of energy flow per unit area
Tube voltage
A parameter that determines the maximum energy of the X-ray photons.
How Rectification Affects X-ray Beam Intensity:
Increased X-ray Output:Rectification increases the overall output of x-rays because the voltage is maintained closer to the maximum value for a longer period during each cycle.
Shorter Exposure Times:The higher x-ray output allows for shorter exposure times to achieve the same image quality, reducing patient dose and motion blur.
Lower Patient Dose:
While the total radiation exposure is reduced due to shorter exposure times, the overall radiation dose to the patient can be lower because fewer low-energy photons contribute to the image.
