Conventional/Image Intensified Fluoroscopy

These flashcards cover key concepts and terms related to Conventional/Image Intensified Fluoroscopy.

Fluoroscopy

A technique invented by Thomas Edison that allows real-time imaging using x-ray.

First radiation related fatality

Clarence Dally.

First to document radiation damage

Dr. Mihran Kassabian.

Open fluoroscopy

The first practical application of fluoroscopy.

Disadvantages of open fluoroscopy

Dim images and high patient dose.

First image intensifier tube inventor

Russel H. Morgan.

Primary use of fluoroscopy

Dynamic studies.

Static images obtained by fluoroscopy

Spot views or scout images.

Location of the tube during fluoroscopy

Underneath the patient.

Location of the II during fluoroscopy

Above the patient.

Reason for tube placement under the patient

Reduces eye and thyroid dose.

Type of scatter that is more intense during fluoroscopy

Backscatter.

Typical mA for fluoroscopy techniques

Why is the dose higher than plain film x-ray?

It uses more time.

Radiographic technique mA compared to fluoroscopy

Radiographic technique has a higher mA.

ABC stands for

Automatic Brightness Control.

Function of Automatic Brightness Control (ABC)

Maintains a selected image brightness by automatically adjusting kVp, mA, or both.

AGC stands for

Automatic Gain Control.

Function of Automatic Gain Control (AGC)

Adjusts brightness at the monitor.

True or False: AGC can fix mottle in the image

False.

kVp range for BE (air contrast)

80-90.

kVp range for upper GI study

100-110.

kVp range for small bowel study

110-120.

kVp range for BE

110-120.

Why are there no mA ranges for common fluoroscopy studies?

mA will vary by thickness and response from ABC.

Units of illumination

Measured in units of lumen per square meter or lux.

Structures of the eye responsible for vision

Rods and cones.

Other name for photoreceptor cells

Photoreceptor cells.

Photoreceptor cell sensitive to low light levels

Rods.

Photoreceptor cell concentrated on the periphery of the retina

Rods.

Visual acuity of rods

Low.

Visual acuity also known as

Spatial resolution.

True or False: rods are color blind

True.

Photoreceptor cells sensitive to bright light

Cones.

Threshold for cone vision

100 lux.

Photoreceptor cells concentrated at the fovea centralis

Cones.

Ability to perceive fine detail

Visual acuity.

Ability to detect differences in light levels

Contrast perception.

True or False: cones are color blind

False.

Daylight vision also known as

Photopic vision.

Photopic vision uses

Cones.

The II takes advantage of what type of vision

Photopic vision.

Conventional fluoro viewed in which vision

Scotopic.

Night vision also known as

Scotopic vision.

Scotopic vision uses

Rods.

Purpose of II

To convert image firing x-rays into high-intensity visible light.

What did the II replace?

Conventional screen fluoro.

Visual acuity is greatest in what vision region?

Cone (Photopic).

Parts of an II tube

Input phosphor, photocathode, electrostatic focusing lens, accelerating anode, output phosphor.

Input phosphor diameters

Variable.

Diameter of the output phosphor

1 inch.

What accounts for minification?

Difference in size between input and output phosphor.

Potential difference between photocathode and anode

25 kV.

Input phosphor composition

Cesium Iodide (CsI).

Benefit of cesium iodide

Light pipes prevent dispersion and improve spatial resolution.

Source of electrons within the II tube

Photocathode.

The photocathode is made up of

Photoemissive metal.

Electrostatic focusing lens uses

Electron optics.

Purpose of electrostatic focusing lens

Pull and focus electrons from photocathode to output phosphor.

Process of focusing electrons into output phosphor

Minification.

Reason for increased brightness through minification

Electrons are concentrated, meaning more energy in a smaller space.

Charge of the accelerating anode

Positive charge of 25-30 kV.

Increase in kinetic energy at output phosphor compared to photocathode

50-75 times increase.

Light photons produced at output phosphor compared to input

50-75 times as many.

Site where electrons interact to produce light

Output phosphor.

Ratio of output light photons to input x-ray photons

Flux gain.

Formula for flux gain

Number of output light photons / Number of input x-ray photons.

Definition of minification gain

Ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor.

Minification gain formula

Input phosphor diameter^2 / Output phosphor diameter^2.

Alternate minification gain formula

Input area / Output area.

Product of minification gain and flux gain

Brightness gain.

Brightness gain range

5000 to 30000.

Brightness gain formula

Minification gain x Flux gain.

More precise measurement than brightness gain

Conversion factor.

Formula for conversion factor

Output phosphor illumination / Input exposure rate.

Type of multifield II with three numbers

Trimode.

Total field size of trimode (25cm/17cm/12cm)

25 cm.

Second mag level field size of trimode (25cm/17cm/12cm)

12 cm.

How electrostatic lenses increase magnification

Charge is increased, further compressing the beam.

Effect of voltage increase on electrostatic lenses

The focal point moves further from the output phosphor.

What shrinking the FOV means

Moving focal spot toward input or away from output.

Image change in magnification mode

It is dimmer.

How to account for loss of brightness in magnification mode

ABC increases mA.

True or False: increasing mag will increase patient dose

True.

Why spatial resolution increases with increased mag

More pixels per area of anatomy and vignetting.

Reduction in brightness at the periphery of the image

Vignetting.

Magnification mode results in

Better spatial resolution, better contrast resolution, increased patient dose.

Most commonly used television camera tube

Vidicon.

Size comparison of input surface of TV camera tube to output surface of II tube

Same size.

Advantages of television monitoring

Audience viewing and electronic storage for playback.

Ways TV camera tube is coupled to the II

Fiber optics bundle and lens bundling.

Pattern the electron beam scans in

Raster pattern.

Frequency of raster pattern

60 Hz.

Television Picture Tube or Cathode Ray Tube

CRT.

Form of image recording used

Film masked in lead diaphragms.

Image recording operates in what technique

Radiographic.

Image recording system functioning like a disposable camera

Photospot camera.

Image recording system using an automatic roll of film

Cine camera.

Scatter of x-rays, electrons, and light photons with in the II tube

Veiling glare.

Effect of veiling glare on contrast

Reduces contrast by increasing noise.