image production 4.2 102720 Flashcards
(48 cards)
What regulates the duration of XR production
Timer
Most equipment uses electronic timer
What is located in the XR circuit between the high voltage transformer and the XR tube
Rectifier
Which of the following meausres tube current
mA meter
Current is flow of e measured in mA
What device spins at 10,000-12,000 rpm
Anode
High speed anodes spin at 10,000-12,000 rotations per minute.
What device uses maximum heat storage ability of the tube to deliver mAs
Falling Load Generator
FLG allows extremely short exposure times
What is the source of bremsstrahlung and characteristics rays
XRs produced by 2 different interactions
that occur between incident electrons fr cathode and tungsten atoms of the anode
What device increases voltage approximately 500 times
Step-up transformer
This where voltage is boosted to KV levels
What is the most commonly used AEC
Ionization chamber
This is located between patient and IR.
Phototimer are seldom used
What device always delivers the shortest exposure time possible
Falling Load Generator
Coupled with a timer exposure accurate to .001s, 1/1000, 1 ms
What device is turned by a rotor
anode
Pressing rotor button activates motor that turns anode.
Which of the following is located between the pt and the IR
Ionization chamber
Wafer thin chamber containing gas that is ionized by XRs passing thru.
At predetermined level of ionization exposure is terminated.
The filament is kept warm by
A standby current fr the time the XR machine is turned on.
The machine keeps filament warm between exposures.
Activating the rotor
reduces tube life
Each time rotor is activated thermonic emission begins to occur at filament. The heating of filament causes tungsten.
When making an exposer the tech should
activate the rotor and exposure switch in one continuous motion
bc it reduces XR tube life
The process of thermonic emission causes
Electrons to boil off the filament
This causes space charge/ or electron cloud to form around filament
The force with which the electron stream passes from cathode to anode is a result of ____________ passing thru the XR tube
kilovoltage
Voltage is the force behind the movement of electrons in a circuit
Heat is produced in XR tube as
electrons interact with the target material
Due primarly to bremsstrahlung at the anode
Most of the energy conversion in the XR tube produces
Heat
99% of incident electrons of kinetic enegy is converted to heat energy. 1% converted to XR energy.
XRs are produced as incident electrons are slowed going past the nuclei of target atoms by a process called
Bremsstrahlung
As incident electrons fly past the atomic nuclei and they are slowed causing production of heat and XRs are also produced by the characteristic interaction.
XRs are produced as incident electrons collide with inner shell electrons in target atoms by a process called
characteristic
As incident electrons dislodge, K-shell electrons in target material outer shell electrons fall inward to fill the holes
Properties of XRs
- affect film emulsion
- scatter and produce secondary radiation
- invisible to the human eye
- travel in bundles of energy called photons/quanta
- can ionize matter and gas
- cause phosphors to fluoresce
The XR beam is
heterogeneous or polyenergetic- consisting of many different energies (wavelengths)
homogeneous- all ray possess the same energy
The XR emission spectrum consists of
discrete spectrum (characteristic) and continuous spectrum (brem)
The primary purpose of filteration is
radiation protection
Hardening the beam for imaging
Longwavelength = soft rays
