L4 - Viewing the image intensifier image and image intensifier problems

what is the size of the output phosphor in II

2.5-5cm

what is matched with the output

CCD

what does the output phosphor do

converts into electrons to light which directs it to CCD

how is the light from the output phosphor directed to the CCD

fiber optics

what does the CCD optics do

converts light into an electronic signal

the light is porportion ot the ___

radiaiton

1 fiber optic tube = x pixel

1

name steps from the xray source to operating console

xray source > patient > II > CCD > ADC > computer > electrons > DAC > operating console

why should the II be placed close to the patient

to maximize distance between xray source and patient

what happens to the electric signal from the CCD

signal is sent to the ADC and switched to digital signal

What is the photosensitive layer on the CCD

crystalline silicone

what happens when electrons hit the crystalline silicon

creates an electrical charge

what are the main characteristics of CCD

good spatial resolution, high DQE, high SNR

why do CCD have good DQE

no lateral spread of light with the fibre optic coupling, good signlaing caught. Lower patient dose

What are CCD not affected by

changes in magnetic fields

what are the problems in II

vignetting, image lag, pincushion/s distortion, veilinng glare, and image magnification

What is vignetting

decrease in brightness in the periphery of images

why does vignetting happens

the periphery is unfocused and not bright, shape of the input phosphor

what is image lag

persistance of an image before while the II is being moved. system cannot resolve the image as fast as the equipment is moving annd creates a blurred image

what is iamge bloom

intense brightness on the monitor because of the CR being moved thus there is no anatomy between II and xray tube

what are the 2 types of shape distortion

pincushion and s-distortion

what is pincushion

a type of shape disortion caused by the image from the curved input phosphor doesnt match with the output phosphor. worse in edges

what is S-distortion

Caused by the changing in magnetic fileds causing the trajectory of the electrons to move in an S pattern

what is veiling glare

light being reflected from the window of the output phosphor. this reduces iamge contrast. happens when moving from thick tissue to thin

what type of distortion is this

S distortion

what type of distortion is this

pincushion

what type of distortion is this

barrel