xray physics chpt. 25

flux gain formula

# of output light photons / # of input x-ray photons

magnification mode results in:

1.better spatial resolution 2.better contrast resolution 3.higher patient dose

in a 25/17/12 multifield image intensifier (ii) which produces a smaller field of view and thus a more magnified image?

12 cm mode

Most image intensifiers have a brightness gain of?

5,000-30,000

a ___ converts the light signal from the output phosphor to an electronic signal

CCD

flow of the intensifier: the xray interacts with the input phosphor made of ___, which converts xrays to light. Then the light is converted to electrons by the __________ which is made of antimony cesium. The electrostatic focusing _____ directs the electrons from the _________ to the output phosphor. Then the output phosphor made of ZnCdS converts the electrons to _______.

CsI (cesium iodide) photocathode lenses photocathode light

magnification gain equation

MG= (Di/D0)^2 Di= diameter of input phosphor D0= diameter of output phosphor

A function of the fluoroscopic unit that maintains the overall appearance of the fluoroscopic image by automatically adjusting the kVp, mA or both

automatic brightness control (ABC)

the ability of the image intensifier to increase the illumination level of the image is called:

brightness gain

BG = MG x FG

brightness gain = magnification gain x flux gain

what is the input phosphor of the image intensifier made of?

cesium iodide (CsI)

_______ __________ _________ method to electronically convert the visible image on the output phosphor of the ii into an electrical signal

charge-coupled device

Where is the image intensifier located?

contained within a glass vacuum tube which amplifies the signal to brighten

duel field vs. trifield magnification

duel= 2 input sizes trifield= 3 input sizes

the photocathode turns light into __________.

electrons

this part of the image intensifier maintains a precise electron path from the photocathode to the output phosphor and is located along the length of the image intensifier

electrostatic focusing lens

the ________ is used for examinations of moving internal structures and fluids

fluoroscope

type of xray for dynamic, real time visualization of structures

fluoroscopy

Ratio of the number of light photons at the output phosphor to the number of x-rays at the input phosphor

flux gain

the ability of an amplifier to increase the power of input signals

gain

what kind of technique is preferred for fluoroscopic studies?

high kVp and low mA

what is required for fluoroscopic studies for maximum image detail?

high levels of image brightness

the fluoroscopy television camera is attached to the __ with a lens coupling to accommodate a cine or a spot film camera

ii ( image intensifier )

Device that electronically improves and enhances radiographic images and transmits them to a television monitor

image intensifier

Complex electronic device that receives the image-forming x-ray beam and converts it into a visible-light image of high intensity

image intensifier tube

When magnification is increased while using an intensification tube, the patient's exposure ______.

increases

the part of the image intensifier that turns xrays to light?

input phosphor

Xrays that exit the patient and enter the image intensifier first interact with the

input phosphor(which is cesium iodide CsI)

part of the image intensifier that must be flawless and cannot disperse light?

input window

during each phase of the image intensifier, the signal gets:

larger (intensified)

what is the desired mA for fluoro studies?

less than 5 mA

the input phosphor turns xrays to ________.

light

the output phosphor turns electrons to ______

light

what needs to increase to compensate for a smaller field in a multifield ii?

mA automatically increases

mulifield image intesifiers produce different _________ of the image

magnification

The use of a smaller dimension of a multifield image intensifier tuble always results in a what

magnified image

"Fluoroscopy" is used to record ________:

moving body parts

Most image intensifiers are

multifield type

what is the charge of the photocathode?

negative

the electron lens use varying voltage to channel e- to the ______ _________

output phosphor

the part of the ii where accelerated electrons interact and produce light

output phosphor

the television camera tube converts light image from the ______ __________ of the image intensifier into an electrical signal that is sent to the television monitor

output phosphor

the part of the image intensifier that minimizes light reflection

output window

Photoemission occurs at the

photocathode

the _________ emits electrons when illuminated by the input phosphor

photocathode

the part of the image intensifier that turns light into electrons?

photocathode

Electron emission that follows light stimulation

photoemission

a smaller field in an ii results in less ________ and a ________ image

photons; dimmer

the kVp for fluoroscopic studies depend on what?

pt thickness of the body part being examined

structures in the eyes that are responsible for the sensation of vision are:

rods and cones

mA For fluoroscope studies are dependent on:

selected brightness, automatic brightness control, and pt. thickness

the part of the image intensifier that is glass or ceramic base for the phosphor (input phosphor)

substrate

the video signal is amplified and is transmitted by cable to the _________ _______, where it is transformed back into a visible image

television monitor

the 25/17/12 cm is a type of:

trifield tube image intensifier where the numbers represent 3 different field sizes of the input phosphor

the tv camera tube that is most used in television fluoroscopy

vidicon

the output phosphor is composed of

zinc cadmium sulfide (ZnCdS)