Production of X-Rays – Key Vocabulary

A comprehensive set of vocabulary flashcards covering the components, physics, and operational factors involved in X-ray production.

Wilhelm Conrad Roentgen

German physicist who discovered X-rays in 1895 and received the 1901 Nobel Prize in Physics.

X-ray Tube

Vacuum glass envelope containing a cathode and anode where electrons are accelerated to produce X-rays.

Cathode

Negative electrode of an X-ray tube housing the tungsten filament and focusing cup.

Anode

Positive electrode of an X-ray tube that contains the tungsten target where X-rays are generated.

Tungsten

High-Z metal (Z=74) with a melting point of 3370 °C used for filaments and targets in X-ray tubes.

Thermionic Emission

Release of electrons from a heated tungsten filament in the cathode.

Dual Focus Filaments

Two separate cathode filaments that provide small and large focal spots for diagnostic imaging.

Focal Spot

Area on the anode target struck by electrons; smaller for diagnostic and larger for therapeutic X-rays.

Line Focus Principle

Technique of angling the anode target (6–17°) to create a small effective focal spot while maintaining heat load.

Heel Effect

Variation in X-ray intensity that decreases from cathode side to anode side due to target self-absorption.

High-Voltage Circuit

Section of the X-ray system providing accelerating potential via a step-up transformer and autotransformer.

Low-Voltage Circuit

Circuit supplying low voltage, high current to heat the filament through a step-down transformer.

Step-Up Transformer

Device that raises incoming voltage to the kilovolt range for electron acceleration.

Step-Down Transformer

Device that lowers line voltage to heat the filament with high current.

Autotransformer

Variable transformer used for stepwise kVp adjustment in the high-voltage circuit.

Rheostat

Variable resistor allowing continuous adjustment of voltage or current in the circuit.

Choke Coil

Filament current controller placed in the low-voltage circuit (mA control).

Self-Rectified Unit

X-ray machine where current flows only when the anode is positive, producing X-rays on one half-cycle.

Voltage Rectification

Conversion of alternating current so electrons always flow from cathode to anode.

Half-Wave Rectification

Rectifier configuration that suppresses the inverse half-cycle, producing X-rays on alternate pulses.

Full-Wave Rectification

Four-rectifier setup that makes both AC half-cycles useful, doubling pulse frequency of X-ray output.

Bremsstrahlung X-rays

Continuous spectrum radiation produced when high-speed electrons decelerate near a nucleus.

Characteristic X-rays

Discrete energy photons emitted when an inner-shell vacancy is filled by an outer-shell electron.

Critical Absorption Energy

Minimum electron energy required to eject a specific inner-shell electron from an atom.

X-ray Energy Spectrum

Graph showing heterogeneous photon energies: continuous bremsstrahlung plus discrete characteristic peaks.

Quality (Penetrability)

Relative ability of an X-ray beam to penetrate matter; related to photon energy.

Quantity (Photon Number)

Total number of X-ray photons in the beam; influenced by tube current and filtration.

Efficiency (X-ray Production)

Ratio of X-ray output energy to electron input energy; increases with atomic number and kVp.

Anode Target Material

High-Z substance (e.g., tungsten) chosen to maximize bremsstrahlung efficiency and characteristic energy.

Tube Voltage (kVp)

Peak potential difference determining maximum photon energy and overall beam quality.

Tube Current (mA)

Rate of electron flow from cathode to anode; directly proportional to X-ray quantity.

Beam Filtration

Use of materials (e.g., aluminum) to absorb low-energy photons, reducing quantity and raising average energy.

Compensating Filters

Special filters placed in the beam to even out intensity differences caused by the heel effect or patient anatomy.

Copper Anode

Backing material for the tungsten target that conducts heat away, often cooled by oil, water, or air.