Flouroscopy Flashcards
What is Luminescence
When material absorb energy and emit light
Two categories: fluorescence and phosphorescence
What is flouroscence
the light is emitted very quickly in milliseconds
What is phosphorescence
The light Is emitted more slowly
Process of Luminescence
x-ray hit phosphor material containing valence band electrons
electrons promoted to a higher energy level
they drop back quickly or slowly
Light is emitted
What is fluoroscopy
imaging technique that uses X-rays to obtain real-time moving images of the interior of an object.
Components of the fluoroscopic imaging chain
x-ray tube
x-ray generator: high freq units and high output
image receptor: image intensifier or amorphous selenium flat panel detector
x-ray table
image monitoring system
connection for X-ray tube and imaging system
What is charge coupled devices
Photosensitive silicon chops that can be used to convert light to a digital video iamge
advantages of CCDs
does not produce artefacts like conventional fluoro
greater sensitivity to light
lower patient dose
no warm up required
What is an image intensifier
a device which is used to convert incident radiation to a light image to be viewed, recorded and photographed
components or elements of image intensifier
input phosphor or photocathode
electrostatic focusing lense
accelerating anode
output phosphor
Input phosphor
made of glass with coat of caesium iodide CsI crystals
converts photons to light photons
CsI is used because; higher resolution, greater packing density
Electrostatic focusing lenses
Set of positively charged electrodes placed inside the surface of the glass envelope
Focus and accelerate the electrons as they travel towards the output phosphor
Anode
Allows passage of electrons to output phosphor
Positively charged electrode that attracts the electron towards the output phosphor
Multifield image intensifier or magnifcation technique
Allows fluoroscopy image to be magnified electronically
Disadvantage of MII/Magnification technique
due to the decrease in minification gain, mA must be increased to main image brightness
significant increase in patient dose
FOV decreased
types of multifield intensifiers
Dual focus: 2 different FOVs
Tri focus: allows for a choice of 3 input phosphor
magnification in flat panel detectors
magnification performed simply by digitally enlarging the display
slight loss of resolution
no increased patient dose
Image intensifiers artefacts
Vignetting
Pincushion distortion
Veiling glare
S distortion
What is vignetting
Decrease in image brightness at the lateral portions of image
What is pincushion distortion
caused by projecting image from a curved surface onto a flat surface
Veiling glare
Caused by light reflection from a window of output phosphor which reduces contrast
S distortion
Warping of the image along an s-shaped axis caused by strong magnetic fields
Applications of Fluoroscopic imaging
barium studies Endoscopic studies (ERCP) fertility studies (HSG) angiographic studies interventional studies cardiac studies orthopaedic procedures
methods for digital flouroscopy - image intensifier tube digital fluoroscopy systems
standard fluoroscopic units feed the image from the television camera directly to the monitor for immediate viewing
analogue signals from camera is first sent through an ADC then through a microprocessor circuit which processes the image
methods for digital flouroscopy - flat panel digital fluoroscopy systems
uses similar flat-panel image detectors to those used in DDR systems
flat-panel detectors replace the II and TV camera combination and feeds the image info directly to an image processor
Digital fluoroscopy- image display
digitally generated image can be displayed on the monitor either monocrome grey-scale images or with bi-stable images
bistable images is which the pixels are either black or white with no shades of grey
monitor scan display modes
continuous flouroscopy mode
pulsed interlaced scan mode
pulsed progressive scan mode
slow scan mode
Advantages of Digital fluoroscopy
last frame hold road mapping digital temporal fitting image enhancement image restoration
Considerations for flat-panel detectors
read out rate
pixel element size
pixel fill factor
mobile fluoroscopic equipment components
two units: intensifier/flat-panel detectors and workstation unit
intensifier consists of a c-arm: variety of movements and an x-ray tube
workstation unit: various handles for movement and positioning, power switch and exposure switch, controls for radiographic settings and PACS system connection
mobile fluoroscopic equipment components cont.
advanced image quality enhancement software
abilty to save and swap images between monitors
contrast controls
brake pedal
x-ray tube: stationary and rotating anode
mobile fluoroscopic equipment components cont 2
generator and range of exposures
TV camera
