Voltage is defined as electrical pressure that forces an electrical current through a conductor. When the radiographer sets the voltage (kVp) on the console, this determines the penetrating power of the X-ray beam. Different size patients and body parts require different voltage settings. 1 ampere (amp) is equal to 1 coulomb flowing through a conductor each second. A coulomb is a specific quantity (63,000,000,000,000,000,000 electrons). By setting the amperage (mA) on the console, the radiographer controls the quantity of radiation per second used for the exam.
Modern X-ray equipment uses electronic timing devices to set exposure times. Technologists need to be able to calculate milliamp-seconds to control the total amount of radiation they are using to perform an X-ray examination. Modern timers express exposure times in milliseconds. Older timers express exposure durations in decimals or fractions of a second.
The radiographer must understand how the generator's rectification effects the output of radiation to be able to use different X-ray machines. Rectification essentially changes alternating current (supplied by the power company) to direct current (usable by the X-ray tube). Typical X-ray units have single-phase half-wave rectification; single-phase full-wave rectification; three-phase, 12-pulse rectification; or high-frequency rectification. The different generators vary in X-ray production efficiency. Understanding the differences in efficiency of the rectifiers is essential to setting accurate technical factors (kVp and mAs) on the console.
The function of the transformers in an X-ray generating system is to increase or decrease the voltage of the supplied electricity. X-ray production requires very high voltage (up to 150,000 for some examanations). If the X-ray unit is supplied with 440 volt electricity, the incoming voltage has to be "stepped-up" hundreds of times by the transformer to produce X-rays. When the radiographer sets the kVp on the console, the autotransformer (variable transformer) changes the voltage supplied to the X-ray tube and the penetrating power of the beam.
Insufficient image quality must be corrected before the films are submitted for reading by the radiologist (doctor who specializes in radiology). The radiographer must evaluate the image quality for accurate density (darkness), contrast, and clarity. These are largely controlled by setting technical factors. By thoroughly understanding the components of the X-ray generating system, the radiographer is able to make necessary corrections.