Lange Equipment Operation and Quality Assurance

Output Phosphor of Image Intensifier Image

brighter, inverted, minified

Input Phosphor of Image Intensifier Image

magnified, distorted, dimer

Primary/Low Voltage X-Ray Circuit Components

autotransformer, kV meter, exposure switch, timer circuit

Secondary/High Voltage X-Ray Circuit

mA meter, rectifier, x-ray tube

X-Ray Circuit

Digital Image Viewing

1.low light level desirable

2.too much light causes images to appear dark

3.bright light cause pupils to constrict causing images to appear dark

Image Intensification FOV Decreases

output screen image magnified, mA increases, output screen image has improved resolution

X-Ray Tube Targets Heat Capacity Factors

rotation and diameter of anode and focal spot size

Equalization

computer software operation, removes densities that veil image details, compresses contrast scale

Alternating Current

Half Wave Rectification

Full Wave Rectification

Direct Current

3 Phase 6 Pulse

3 Phase 12 Pulse

High Frequency

Flat Panel Fluoroscopy Advantages

greater maneuverability, improved contrast resolution, eliminate need for ADC, considerably smaller size and weight

Blur

unsharp edges of tiny radiographic details

Collimator Evaluation

semiannually

Improve Spatial Resolution of Image-Intensified Images

very thin input phosphor layer, small input phosphor diameter, use magnification mode

X-Ray Tube Characteristics/Qualities

1.target material should have high atomic number and high melting point

2.useful beam emerges from port window

3.cathode assembly receives both low and high voltages

AEC Device

parallel-plate ionization chamber that receives particular charge as x-ray photons travel through it

Total X-Ray Photons Produced at Target Factors

tube current, target material, kV²

Single-Phase Anode Heat Hazard

0.6mm focal spot, 60 kV, 12 mAs

Radiographic Rating Charts

enable radiographer to determine maximum safe milliamperage, exposure time, and kilovoltage for particular exposure and particular x-ray tube

Lowest Heat Exposure

use large focal spot and smaller mAs value

Heat Units Equation

kVp x mAs x MF(3 phase, 6 phase, high)

Cathode Filament Material

thoriated tungsten; liberates electrons through thermionic emission when heated to white hot(incandescence)

Glass Envelope

preserves vacuum necessary for efficient x-ray production

Rotating Anode Material

light weight molybdenum disk with beveled focal track at periphery and stem

Focal Track Material

tungsten rhenium alloy

Focusing Cup Material

nickel; directs liberated filament electrons to the focal spot

Automatic Exposure Rate Control

compensate for changes in patient/part thicknesses, FOV, and OID during flat panel detector fluoroscopic procedures

Large Exposure to Cold Anode or Exceeding Tube Limitation Effects

cracking of anode, rotor-bearing damage, pitting/localized melting of focal track, vaporized tungsten deposits on glass envelope causing decreased tube output

Vaporized Tungsten on Glass Envelope Effects

decreased tube output, acts as additional filtration, possible puncture of glass envelope

kV and HVL Relationship

direct; as one increases the other increases

Window Width Decreases

contrast scale decreases

Solid-State Diode Rectifiers

circuit devices that permits electrons to flow in only one direction; convert AC to DC

Scintillation Types

amorphous silicon, cesium iodide, gadolinium oxysulfide

AEC Backup Timer

protect patient from overexposure and protect x-ray tube from excessive heat

Generator

device that converts mechanical energy to electrical energy

Inherent Filtration

x-ray tube’s glass envelope and its oil coolant; built in filtration that is permanent part of tube head; 0.5-1mm Al equivalent

Slit Camera

measures focal spot size and spatial resolution

Mobile Equipment Requirements

1.exposure switch must be dead man type

2.radiographer must alert individuals in area before making the exposure

3.lead apron must be carried with unit and worn by radiographer during exposure

4.exposure cord must be at least 6ft

Anode Focal Track Pitting Cause

repeated frequent overloading

Collimator Advantages

variety of field sizes available and more efficient beam restriction

Star Pattern

evaluates focal spot accuracy as function of geometric blur

Metallic Element Tungsten Characteristics

readily dissipation of heat, high melting point, high atomic number

Grid Ratio

height of lead strips divided by distance between them

3 Phase 6 Pulse Ripple

13%

Triple Field Image Intensifier Highest Patient Dose

its 12in mode; due to increase electrostatic focusing lenses voltage that causes magnification and dimmer image and mA increased automatically to compensate for it

Image Intensifier with Highest Patient Dose

smaller diameter anodes

3 Phase 12 Pulse Ripple

4%

Voltage Ripple

percentage drop from maximum voltage each pulse of current experiences

High Frequency Generator Ripple

1%

Single Phase Generator Ripple

100%

Bremsstrahlung Radiation

high speed electron decelerated as it is attracted to tungsten atom nucleus, changes its course, and energy released during braking action

Characteristic Radiation

incident electron ejects a K-shell electron and L-shell electron drops into its place and energy liberated

Image Intensifier Parts

input phosphor, photocathode, focusing lenses, accelerating anode, output phosphor

Digital Imaging Components

computer manipulation of image and formation of electronic image on radiation detector

Charge Coupled Device(CCD)

replace image intensifier’s television camera tube in digital fluoroscopy

Radiographic Equipment Check for Linearity and Reproducibility

required annually

Quality Control

regular measurement and evaluation of radiographic equipment components and their performance

Digital Imaging Examples

CT, MRI, CR

Fluoroscopy Automatic Brightness Control

adjust kV and mA

Current

amount of electric charge flowing per second

Voltage

potential difference existing between 2 points

Resistance

property of circuit that opposes current flow

Capacitance

quantity of stored electricity

Radiographic kV Settings Evaluation

required annually

Beam Splitter

device that directs the light emitted from the image intensifier to various viewing and imaging apparatus

Image Intensifier Tube Input Phosphor

convert x-rays to light

Inherent Filtration Contributions

x-ray tube glass envelope and x-ray tube port window

Digital Imaging Subject Contrast

signal differences within the remnant beam

X-Ray Tube

Rotor and Stator Operation

both operate on principle of electromagnetic induction; stator located outside and rotor located inside; both function to rotate the anode

Total Brightness Gain

flux gain x minification gain

Complementary Metal Oxide Semiconductors(CMOS) Advantages

less expensive and much greater speed; produce less image quality

Picture Archiving and Communication System(PACS)

used for reception, display, storage of digital images

Half Value Layer(HVL)

thickness of an absorber that will decrease intensity of beam to ½ its original value

Increase in Heat of the Filament

cause increase in mA due to more electron release during thermionic emission and incandescence

Grid Rule

always use when using high kV and radiographing a large/dense body part

Greatest Detail Sharpness Combinations

smallest target angle and smallest actual focal spot

Image Intensifier Tube

CCD Advantages over Television Cameras in Image Intensification

compact size, improved resolution, higher DQE

X-Ray Tube Rating Chart Maximum Safe kV Requirements

mA, exposure time, and focal spot size

CR Spatial Resolution Increase

PSP crystal size decreases and laser beam size decreases

3 Phase X-Ray tube Voltage

87%-96% of maximum value, nearly constant potential

Proper Projection of Light in Collimator Requirements

focal spot and light bulb distance must be exactly the same distance from the center of the mirror

Image Intensifier Input Phosphor Material

cesium iodide

AEC Essential Function

terminate x-ray exposure once IR is correctly exposed

Grid Interspace Material

aluminum(resists moisture, sturdier, smoother appearance) and plastic fiber(moisture causes warping)

Transformer Law Voltage

V_s/V_p=N_s/N_p

Transformer Law Intensity

N_s/N_p=I_p/I_s

Autotransformer Operation

principle of self induction

Autotransformer Adjustment

kV

Filament Circuit Adjustment

proper current and voltage to x-ray tube filament for proper thermionic emission

Rectifier Circuit Adjustment

changes AC to unidirectional current

Fluoroscopy Brightness Factors

mA, kV, patient thickness

Bremsstrahlung Radiation