image production 4.2 102720 Flashcards
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
The material needed to reduce the intensity of the beam by 1/10 is called
Tenth-value layer
Beam quality is commonly discussed half-value layer
When a quality control test is performed to ensure that the PENETRATING ABILITY OF THE XR BEAM is accurate, the result must be within what amount of the control panel setting
50%
The primary type of grid used
focused
The portion of the II tube that converts electron energy to visible light is
output phosphor
The portion of the II tube that converts visible light to electrons
photocathode
The input phosphor of the II tube converts
XR energy to visible light
XRs exiting pt strike input phospher as it glows with visible light
Total brightness gain achieved using an image intensifier equals
Flux gain times minification gain
PROGRAMS THAT DEAL with the safe and reliable operation of equipment
Quality control
PROGRAMS THAT ADDRESS all aspects of the delivery of radiology services are called
Quality assurance
An image intenifiers conversion factor is expressed as the ratio of
the luminance of the output phosphor to the exposure rate at the input phosphor
The collimator must be accurate to the level of
=/- 2% of the SID
QUALITY CONTROL STANDARD
KVP must be accurate to within
10% of the control panel settings
or 4-6 KVP
Exposure linearity (mA) must be accurate to within
10%
Exposure reproducibility (AEC) must be accurate to within
5%
The test that measures the accuracy of adjacent mA station is
Exposure linearity (5%)
The test that measures the accuracy of successive exposures (AEC) is
Exposure reproducibility (5%)
The accuracy of the timer must be within
5% of the time chosen for exposures over 10ms
Fluoroscopy exposure rate may not exceed
100mGyair per minute
It is measured in-air at table top
The feature that automatically adjusts KVP and mA during fluoroscopy is called
ABC
Automatic Brightness Control
Resolution of the television system may be measured using the following tool
Resolution per test pattern
An IIs conversion factor is expressed as the ratio of
The luminance of the output phosphor to the exposure rate at the input phosphor
The number of mAs used for analog fluoroscopy is
3 to 5
This is asking mA actually used and not the setting of the mA at control panel
Marks on the focal track of the anode resulting from bombardment of electrons are called
pitting
Effective quality control and quality assurance programs are required for accreditation by
The Joint Commission (TJC)
Rep of TJC reguarly visit healthcare facilities
