Fluoroscopy

P1 IR

Fluoroscopy

To provide real-time, dynamic viewing of anatomic structures.

Examinations that show the motion of circulation or internal structures

What are dynamic studies in fluoroscopy?

As a continuous image while the x-ray tube is energized.

How is the image viewed during a fluoroscopic examination?

Spot Film

A radiograph taken during fluoroscopy to preserve a specific image for further study.

Fluoroscopy

It used for examination of moving internal structures and fluids.

Spot Film

A method allows a radiologist to permanently record an image during fluoroscopy without interrupting the exam

Spot Film

A small static image recorded on a small-format image receptor during fluoroscopy.

A routine x-ray examination, except for its specialized use in angiography.

What type of x-ray examination is fluoroscopy considered?

Angiography

The fluoroscopic visualization of blood vessels.

Neuroradiology

vascular radiology

What are the two main areas of angiography?

Interventional Radiology

What is the modern term used for angiographic procedures?

Under the patient couch, with the image receptor above the patient.

Where is the x-ray tube usually located in a fluoroscopic system?

On a television monitor or flat-panel monitor.

Where is the fluoroscopic image displayed during image-intensified fluoroscopy?

Less than 5 mA

At what tube current (mA) does fluoroscopy typically operate?

Because the x-ray beam is continuous and exposure time is much longer.

Why is patient dose higher in fluoroscopy than in radiography despite lower mA?

The body part being examined

What determines the kVp used during a fluoroscopic examination?

Automatic Brightness Control (ABC)

What feature automatically maintains image brightness during fluoroscopy?

Image illumination and visual physiology.

What additional knowledge is required to interpret fluoroscopic images effectively?

Lux (lumens per square meter).

In what units is illumination measured?

Approximately 100 to 1000 lux.

Under what illumination levels are radiographs typically viewed?

They are similar (100–1000 lux)

How do illumination levels in image-intensified fluoroscopy compare to those used for radiographs?

Rods

Cones

What structures detect light when it reaches the retina?

More than 100,000

Approximately how many rods and cones are found per square millimeter of retina?

In the fovea centralis, at the center of the retina.

Where are cones primarily concentrated in the retina?

In the peripheral retina

Where are rods most numerous in the retina?

Rods

Which photoreceptors are more sensitive to low light levels?

About 2 lux

What is the approximate threshold for rod vision?

100 lux

What is the approximate threshold for cone vision?

Cones

Which photoreceptors are capable of responding to intense light levels?

Photopic Vision (Daylight)

Which type of vision is associated with cones?

Scotopic Vision (Night)

Which type of vision is associated with rods?

Cones

Which photoreceptors are better at perceiving small objects and fine detail?

Visual Acuity

What is the term for the eye’s ability to perceive fine detail?

Cones

Which photoreceptors are better at detecting differences in brightness levels?

Contrast Perception

What is the term for detecting differences in brightness levels?

Cones

Which photoreceptors are responsible for color vision?

Approximately 555 nm (green light).

Under scotopic conditions, at what wavelength is the eye most sensitive?

Patient Anatomy

kVp

mA

What factors primarily affect fluoroscopic image brightness?

kVp

mA

Which factors can the radiologic technologist control during fluoroscopy?

High kVp

Low mA

What general kVp–mA combination is preferred for fluoroscopy?

Radiologist

Radiologic Technologist

Who determines the precise fluoroscopic technique used?

Image-intensifier Tube

To convert the image-forming x-ray beam into a high-intensity visible-light image.

Cesium Iodide (Csl)

What material is used for the input phosphor of the image-intensifier tube?

About 300 μm, with crystals approximately 5 μm in diameter.

Approximately how thick is the CsI input phosphor layer?

Photocathode

A thin metal layer bonded directly to the input phosphor.

Cesium

Antimony Compounds

What materials typically compose the photocathode?

Photoemission

What process occurs when the photocathode emits electrons after light stimulation?

About 50 cm.

What is the approximate length of the image-intensifier tube?

Approximately 25,000 volts (25 kV) between the photocathode and anode.

What voltage accelerates electrons within the image-intensifier tube?

Zinc cadmium sulfide

What material is commonly used for the output phosphor?

Electron Optics

The engineering methods used to control and focus electron paths from the photocathode to the output phosphor

Electrostatic focusing lenses

What devices control electron focuses within the image-intensifier tube?

Approximately 50 to 75 light photons.

How much light does each photoelectron produce at the output phosphor?

Flux Gain

The ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor.

Minification Gain

The increase in image brightness caused by reducing the image size from input phosphor to output phosphor.

Flux Gain

Minification Gain

What two factors contribute to increased image illumination in an image intensifier?

Brightness Gain

The ability of the image intensifier to increase image illumination.

Minification Gain

The ratio of the square of the diameter of the input phosphor to the square of the diameter of the output phosphor.

50 to 300

What is the typical conversion factor range of image intensifiers?

5000 to 30,000.

What brightness gain corresponds to image intensifier conversion factors?

105-mm film

What film size does the spot-film camera use?

Internal scatter radiation

What causes a reduction in contrast in image intensifiers?

Multifield image intensifiers.

What type of image intensifiers is most commonly used?

25/17/12 cm (diameter of the input phosphor).

What is the most popular size for trifield image intensifier tubes?

Television Camera

Converts the light image from the output phosphor into an electrical signal that is sent to the monitor.

Thermionic television camera tube

Solid-state charge-coupled device (CCD)

What are the two main methods to convert visible images on the output phosphor into electronic signals?

Supplies a constant electron current by thermionic emission and forms it into an electron beam.

What is the function of the electron gun in the television camera tube?

Converts light into an electrical signal

What is the purpose of the target assembly in the camera tube?

A fiberoptic bundle.

the simplest method of coupling the image intensifier to a television camera?

Lens Coupling

What type of coupling is required for cine or photospot cameras?

Accepts light from the output phosphor and converts it into a parallel light beam

What is the function of the objective lens in lens coupling?

Divides the light beam so part goes to the television camera and part to the film camera.

What is the purpose of the beam-splitting mirror?

television picture tube, also called the cathode ray tube (CRT)

What is the heart of the television monitor?

MODULATION

a change in a quantity or signal in response to another quantity or signal and is widely used in medical imaging.

Horizontal Traces

The electron beam then is turned off and it returns to the left side of the screen as shown.

Interlace

The movement of the electron beam that creates two interwoven television fields.

Vertical Retrace

The electron beam is turned off again and undergoes to the top of the screen.

Vertical Resolution

It is determined by the number of scan lines.

Horizontal Solution

It is determined by bandpass.

Bandpass

It is expressed in frequency (Hz) and describes the number of times per second that the electron beam can be modulated.

one-on-one mode

When the entire film is exposed at one time

two-on-one mode

When only half of the film is exposed at a time, two images

Photospot Camera

It is similar to a movie camera except that it exposes only one frame when activated. It receives its image from the output phosphor of the image-intensifier tube and therefore requires less patient exposure than is required by the cassette-loaded spot film