Physics Ch. 15– fluoro

When and who developed the first commercial fluoroscope

1896 by Thomas Edison

The first commercial fluoroscope allowed for _________ radiographic examination

Dynamic

with the first fluoroscope, radiation dose was _____ and the image was _____

High; dim

When was the image intensifier introduced

1950s

What did the image intensifier do to the image

Brightened and made indirect viewing possible

What is the difference between the mA used in image intensified fluoroscopy and mA used in radiographic mode

Image intensified uses low mA

Radiographic mode uses higher mA

What mA is used in image intensified fluoroscopy

0.5-5 mA

What mA is used in radiographic mode

50-1200 mA

Low mA allows for

increased fluoro time

Control panel includes a timer that buzzes audibly when ______ of xray fluoroscopic time has been used

5 min

The continuous beam is active using a

Deadman's switch

where is tube located in fluoro

under the table

An electronic vacuum tube that converts the remnant beam to light, then electrons, then back to light, increasing the light intensity in the process.

image intensifier

Basic parts of the image intensifier

input phosphor

photocathode

Focusing lenses

accelerating anode

output phosphor

The input phosphor faces the patient, absorbs the remnant beam, and emits

Light

Emitted light exposes the photocathode, which emits

Electrons in proportion to light intensity

______ are needed to result in one emitted electron.

Many light photons

order of image intensifier

Input phosphor to light

Light to electrons

Back to light

Increases light intensity

Emitted electrons are accelerated to the output phosphor by the _______ and "focused" on the output phosphor by the _______

Accelerating anode; electrostatic focusing lenses

What is the result from image intensifiers

Increased image brightness

an expression of the ability of an image intensifier tube to increase the brightness of the image.

brightness gain

Traditionally, brightness gain was found by

multiplying the flux gain by the minification gain

It is now common practice to express the increase in brightness with

conversion factor

An expression of the luminance at the output phosphor divided by the input exposure rate.

conversion factor

What is the efficiency of the image intensifier with a higher conversion factor?

Greater

What happens to the image intensifier's ability to increase brightness?

Deteriorates with tube age

Brightness gain formula

brightness gain = minification gain x flux gain

flux gain formula

Flux Gain = # of Output Light Photons/# of Input X-ray Photons

A function of the fluoroscopic unit that maintains the overall appearance of the intensified image (contrast and brightness).

Automatic brightness control (ABC)

ABC automatically adjusts

kVp, mA, or both

T or F

With automatic brightness control, the operator can select a desired brightness level

True

What increases voltage to the electrostatic focusing lens?

Magnification mode

With image intensifier, magnification mode is going to do what to patient dose

Increase

Magnification factor formula for fluoro

Full size input diameter/selected input diameter

What does magnification do to fluoroscopist's ability to see small structures and patient dose

Improves ability to see small structures

Increases patient dose

What does magnification mode do to spatial resolution

improves

Spatial resolution in a typical fluoro system is

4-6 lp/mm

misrepresentation of the true size or shape of an object

distortion

Unequal magnification of an image creates a

pincushion appearance

Pincushion appearance causes

Loss of brightness around periphery

What results when insufficient information is present to create the image

image noise

Solution for insufficient information present to create image

Increase mA

The viewing system now

Television monitor

series of optical lenses that focus the image from the output phosphor on the camera tube

Optical lens system

What diverts some of the light to the desired spot-filming device

Beam-splitting mirror

What converts the electronic signal into a visible image

Television monitor

The television monitor converts electronic signal to

Visible image

Spatial resolution of image intensifier

5 lp/mm

Spatial resolution of monitor

1-2 lp/mm

A static imaging process using a radiographic cassette to obtain an image

cassette spot filming

Cassette spot filming is done using a

Film camera

A static imaging system that is used with an optical lens system incorporating a beam-splitting mirror

Photospot camera

What did early versions of digital fluoroscopy add between camera tube and monitor

ADC and computer

What replaced the camera tube and improved digital fluoroscopy

Charge-coupled device (CCD) with ADC

A device that takes the video (analog) signal & divides it into a number of bits (1s &0s) that the computer "understands"

analog-to-digital converter (ADC)

The number of bits that the signal is divided into determines

Contrast resolution

What is necessary for the computer to process and display the image

ADC

What may be used in the place of an image intensifier

flat panel detector

Indirect capture detector

cesium iodide and amorphous silicon

Direct capture detector

amorphous selenium

T or F

FPDs are much lighter and more compact, and they produce a digital signal directly

True

What replaced image intensifiers

FPD

Current dynamic versions of FPD are capable of up to?

60 frames per second

Advantages of using flat panel detectors in place of an image intensifier

- They reduce tower size, bulk, and weight.

- They replace spot filming and other devices.

- They do not degrade with age, are more durable, have better contrast resolution, have higher detective quantum efficiency (DQE), have a wider dynamic range, present a rectangular field providing more information, and have the postprocessing options common to digital images.

- They do not exhibit most image artifacts seen with image intensifiers

FPD reduce the patient's radiation dose by as much as

50%

FPD fluoroscopy operate in radiographic mode of what mA

50-1200 mA

T or F

FPD operate in radiographic mode and additional radiographic images are not needed

True

does FPD have a higher or lower spatial resolution than image intensified systems

Higher

What must be charted

Fluoro time

Cumulative air kerma

Dose Air Product

What allows for virtual collimation without exposing the patient

Last image hold (LIH)

Frame averaging reduces patient dose and image noise by

averaging multiple frames together

Frame averaging does what to spatial resolution

Decreases

automatically adjusts the tube current, voltage, filtration, and pulse with to maintain exposure to the flat panel detector.

Automatic exposure rate control (AERC)

the selection of a smaller field of view (FOV).

electronic magnification

a design of the unit that rapidly turns the x-ray beam on and off during operation.

pulsed fluoroscopy

What does pulsed fluoroscopy do to patient dose

Decreases

In digital systems, what does increases magnification do to patient dose

No increase

how many pulses occur per second of operation; how many exposures occur per second.

Pulse rate

the length of each pulse.

pulse width

What will save single images or a fluoro sequence loop to memory. Then can be post processed and maintained in the patient's permanent record

Last image hold (LIH) and fluoro loop save

What specifies the intensity of x-rays at a given point in air at a known distance from the focal spot or source of x-rays and the cumulative or total air kerma will be monitored during the fluoroscopic procedure.

Air kerma

Air Kerma stands for

kinetic energy released in matter

Other dose displays that provide indicators of patient radiation risk and should be documented in the patient's record.

DAP and KAP

Liquid crystal layer sandwiched between polarizing layers

Liquid Crystal Display (LCD)

Contains a layer of gas filled pixels, and when the gas in ionized, they release UV radiation, simulating phosphor coating in the cell, producing visible light

Plasma monitors

In plasma monitors, when gas in pixels is ionized, they release

UV radiation

Produces equipment to monitor equipment performance and minimize patient dose.

QC programs

Quality control is a team effort among the

Radiographer, radiologist, and medical physicists

T or F

The radiographer may be responsible for the operational inspection of the equipment.

True

Who should conduct and interpret the performance inspection and testing of the equipment as well as oversee the entire quality control monitoring program.

Medical physicist