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Chapter 7 IE

Imaging Equipment

TermDefinition
Primary Circuit (Low Voltage) Begins at Main Power switch on the control console of Radiography unit & leads to the Primary Coil of High tension transformer
Secondary Circuit (High Voltage) Begins at the Secondary Coil of the step-up transformer.
Junction Box Where the radiography unit control console is connected.
High Voltage Transformer and electromagnetic device that will increase or decrease the voltage of alternating current. Consists of 2 iron coils wrapped w/ windings of electrical wire.
Radiographic units may be divided into 2 parts. Primary and Secondary Circuits
In an xray machine the high voltage transformer increases the? Low voltage of the Primary Circuit to High Voltage needed by the Secondary Circuit...
6 Major Components included in Primary section of Circuit.... Autotransformer, kilovolt peak meter, line voltage compensator, filament circuit, circuit breaker and timers.
Autotransformer special type transformer used w/ the major & minor kVp selctors to provide a means to vary (V) magnitude thru Step-Up and Step-Down transformer.
Kilovolt Peak Meter connected to the autotransformer. It's function is to display the Potential Difference in kilovolts going to the high voltage transformer.
Line Voltage Compensator Connected across or in parallel w/ Primary Circuit to Autotransformer. Function is to increase or decrease Line Voltage if there is a drop in surge line voltage. Any change in Voltage will cause a change in output of radiation.
Filament Circuit Connected to the autotransformer. Function is to supply current to the filament of the Radiographic Tube.
Circuit Breaker Protective device used to automatically terminate the current.
Timers Duration of exposure time is controlled by a switch in timing circuit.
Synchronous Timer Is controlled and driven by an electrical synchronous motor.
Electronic Timer Impulse & mAs
mAs Timer An electronic timer used to control and terminate the time when correct mAs are reached. Which also protects the tube current.
Impulse Timer A precise timing circuit that operates w/ an alternating current. The circuit is energized to variable time intervals from milliseconds to seconds and is Accurate.
Automatic Timer Automatically terminates the exposure when the correct amount of radiation (density) has reached the film. Accuracy depends on positioning the anatomical part being filmed.
Phototimers Utilizes a light sensitive photo multiplier tube place behind a fluroscent screen.
Ionization Chamber Utilizes a chamber located between patient and film. This chamber measures the amount of radiation reaching the film and shuts off the exposure at a predetermined setting.
What are the 2 types of Timer Test? Electric Meter (single phase) and Electric mAs Meter (3 phase)
Milliameter (mA) Meter is used to measure the current in milliamperes flowing through the radiographic tube. It connects in series w/ High Voltage Circuit.
Rectifiers are used to change alternating current to direct current or flow in one direction.
Alternating Current is used in the Primary Circuit for 2 reasons... It is the type of electricity supplied by the electrical utility. Transformers will only work on alternating current.
Direct Current is neccessary to operate the Radiographic Tube so... Electrons can be produced and kept flowing in once direction.
Rectification is controlled in modern equipment by a device called Diodes
Half Wave Rectification decreased negative voltage, impulse current and has 2 diodes.
Full Wave Rectification Most efficent and has positive and negative voltage with 4 diodes.
High Voltage Cables 2 cables, 1 for cathode and 1 for anode side. designed to prevent any electrical hazzard.
Important facts to know 1.The electrical capacity of the unit in terms of mA & kVp. 2.The limitaion of any unit, especially portables. 3. The purpose and combinations of exposure factors- the mA, time (s) and kVp selections.4. The purpose and effectiveness of radiographic access
Accessory Items cassettes, grid cassettes, film printers, compression bands, tape & sponges.
Caliper A measuring device to measure the volume of tissue thickness of a body part.
Penetration is controlled by... kVp
Technique factors are determined to protect against.... overexposure or underexposure
Fixed kilovoltage technique Uses an optimum kilovoltage that will penetrate a given part of the body.
Variable kilovoltage technique rarely used
kVp controls penetration but produces.... scatter as it is increased and results in reduced contrast in recorded image.
APR- Automatic Program Radiography Uses microcomputers to determine kVp & mAs (time)
High kVp Technique are designed to utilize high kVp for penetration. Usually from 100 kVp and greater.These are used for barium studies or chest films.
Cassettes Used to provide mechanical support and protection for the film and contains intensifying screens.
Screens Purpose is to intensify the action of radiation.
Created by: kristiew1