X-Ray History & Radiation Units
He discovered X-rays on November 8, 1895.
Who is Wilhelm Conrad Roentgen?
The percentage of kinetic electron energy converted into thermal energy at the anode target.
What is ~99%?
The negative electrode inside the x-ray tube that acts as the source of electrons.
What is the cathode?
The primary exposure factor that controls electron speed and beam quality (penetrating power).
What is kVp (Kilovoltage peak)?
The foundational radiation protection rule summarized by the acronym ALARA.
What is As Low As Reasonably Achievable?
This SI unit measures the absorbed dose of radiation energy in tissue.
What is the Gray ($\text{Gy}_t$)?
The process where heating a tungsten filament causes it to "boil off" outer-shell electrons.
What is thermionic emission?
The atomic number (Z) of tungsten, making it ideal for withstanding target heat and producing x-rays efficiently.
What is 74?
The mAs resulting from an exposure setting of 400 mA at 0.25 seconds.
What is 100 mAs?
The three cardinal rules of radiation protection.
What are Time, Distance, and Shielding?
This unit measures overall relative biological risk to humans across whole-body ionizing radiation exposure.
What is Effective Dose (measured in Sieverts/rem)?
The continuous x-ray production mechanism caused by the slowing down or braking of incoming electrons near a tungsten nucleus.
What is Bremsstrahlung interaction?
The negatively charged component that condenses and directs the electron cloud toward the anode target.
What is the focusing cup?
The geometric effect where slanting the target angle creates a smaller effective focal spot while maintaining a larger physical actual focal spot.
What is the line-focus principle?
The total minimum aluminum equivalent beam filtration required for standard x-ray machines.
What is 2.5 mm Al equivalent?
The standard conversion showing how many rads equal 1 Gray.
What is 100 rads?
The minimum kinetic energy required by a projectile electron to produce a K-shell characteristic x-ray photon in tungsten.
What is 69.5 keV?
The motor components consisting of stators outside the tube and a rotor inside that spin the rotating anode.
What is an induction motor?
The radiation intensity phenomenon that makes the x-ray beam stronger on the cathode side than on the anode side.
What is the anode heel effect?
The exact thickness of absorbing material needed to reduce x-ray beam intensity by 50%.
What is the Half-Value Layer (HVL)?
The quantity equal to D X Wr X Wt.
What is Effective Dose (E)?
The kinetic energy of a Bremsstrahlung photon created when a 120 keV electron passes a nucleus and exits with 40 keV of remaining energy.
What is 80 keV?
This generator component converts alternating current (AC) into direct current (DC) using diode pairs.
What is a rectifier?
The generator type that produces a high-frequency waveform with less than 1% voltage ripple.
What is a High-Frequency (HF) generator?
The primary reason major organizations recommend discontinuing routine gonadal shielding in pelvic/abdominal imaging.
What is diagnostic interference/misplaced shielding causing repeat exposures (or significantly lower doses from modern digital systems)?