University of Guyana
Health Sciences Faculty
BMI2202
Lecturer: Ms.Schimze Sagon
Presenter: Miracle Cambridge
• At the end of this presentation you should be able to:
• To define pneumonia
• To identify factors that predispose to pneumonia
• State how each of the factors can cause pneumonia
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The control unit is the part of the x ray
system that allows the operator to
control technical factors.
Functions on the control unit
• on/ off
• Regulate incoming power
• Kvp selection
• Time selection
• mA selection
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• There are three principle controls to a standard x ray system
• Current control (mA)
• The voltage control (kV)
• Timers
The console will have control for
• Focal spot (is the area of the anode surface which receives the beam of
electrons from the cathode)
• Line voltage compensation
The controls for the system are usually house in a panel.
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Power supply
• Panel power on/off
Autotransformer
1.Line compensation
• Line meter
• Primary side adjustment
Kvp selection
• Secondary side adjustment
variable turns ratio
Filament circuit power
mA selector
• Precision resistor
• Meter
Kvp selector
• Major / minor taps
• Meter (pre reading)
Time selector
• Circuit types
• Exposure switch
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Line compensator: This is where the voltage from the wall plug-in is measured and
then stabilized to 220 Volts for the x-ray circuit.
Autotransformer: Has a single winding and sends voltage to the filament and high
voltage circuit
A. Selects the major or minor kvp and steps the voltage up to
kilovolts
kvp meter: measures the electrical potential of the x-ray tube.
Exposure switch: used to complete the x-ray exposure. It regulates the length of the
exposure.
filament circuit: where we have the ammeter, or the mA selector, which selects the
tube current to heat the filament.
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• The number of electron emitted by the filament is determined by the
temperature of the filament.
• The filament operate at currents between 3 and 6 A
• Tube current is controlled through a separate circuit
• .The voltage is provided by the taps of the autotransformer
• The voltage is then delivered to the filament transformer
• The selection of the small or large filament is connected to the mA
selection
.
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Setting the desired kvp will determine the voltage applied
to the step up transformer in the high voltage section of
the machine
Kvp determine the quality of the x ray beam.
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• Timers are used in the system so that radiographer starts the exposure and the timers stops it.
• The timer circuit is separate from the other main circuit of the x ray circuit of the x ray system.
Type of Timers
• Mechanical timers
• Electronic timers
Selecting time: control time it takes to charge the capacitor
Activating exposure also begin storage of charge in the capacitor
• MAs timers :a special type of timer that accurately control tube current and exposure time
• The product of mA and time(mAs) determine the number of x ray photon emitted and the density
on the film
• Monitors the product of mA and terminates the exposure when the desired mAs has been attained.
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• An electric meter, or energy meter, is a device that measures
the amount of electric energy consumed by x-ray console .
• The kvp meter accelerating voltage is measured .
• The mAs meter which measures the current going to the xray tube.
• The pre-reading kvp meter: indicates anticipated kvp.
• Exposure switch: it initates time and terminates the exposure.
• Line monitor : supplies precise voltage to filament circuit and
high voltage transformer.
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• Quantity refers to the number of x ray photon in the beam.
• As the number of photon increase the beam intensity increases
• Quantity is affected by changes in mA( tube current) and
Changes in Kvp.
• Changes in mA Tube current is the rate of electron flow from
filament to Target
• As the tube current increase the number of incoming electron
striking target increases
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• Quality refers to the overall energy of the beam
• Quality is directly affected changes in kvp (maximum voltage
applied across an x ray tube)
• The increase in kvp increase the speed with which incoming
electron strike the target
• Hence as the kvp increase more higher energy photon are
included in the beam.
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• Current mA
• Voltage kvp
• time
• Increase in quantity ; no
changes in quality
• An increase in quality and
quantity
• Altering the time setting
influences the quantity of
x-rays and image density
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• Conventional imaging control units was manually worked Parts
of the control unit on either on or behind the image receptor.
• Digital image the control unit is located in the control room and
all the parts was place together and there is automatic and
manual input.
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• (RADIOLOGIC SCIENCE FOR TECHNOLOGISTS_ PHYS, BIOL & PROTECTION)
Stewart C. Bushong ScD FACR FACMP-Radiologic Science for Technologists_ Physics,
Biology, and Protection, 10e-Mosby (2012).
• Diagnostic Radiology Physics
• Bushong, Stewart C. Radiologic Science for Technologists: Physics, Biology, and
Protection. Mosby, 2017.
• Carlton, Richard R., and Arlene McKenna Adler. Principles of Radiographic Imaging: An
Art and a Science. Fifth edition. Clifton Park, New York: Delmar/Cengage Learning, 2013.
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