Fluoro - Part 2 Flashcards
Static imaging system that is used with an optical lens system incorporating a beam-splitting mirror
-light from II output layer exposes photographic film
-requires approx. 1/2 the radiation dose of the cassette spot filming system
Photo spot devices
-attached to a port on the optical distributor of an II and can record rapid sequences of images on 35 mm film
-can capture rapid motion
-utilizes very short radiographic pulses
Cine radiography cameras
Attached to the front of the II and allows the acquisition of radiographic images
-when an image is required, the operator places cassette directly in front of the II
-radiographic pulse of X-rays is used to create an appropriate exposure
Spot film devices
T/F
In digital fluoro, spatial resolution is determined both by the image matrix and by the size of the II
True
*spatial resolution is limited by pixel size
What two types of IR are used in digital fluoro?
Charge coupled device (CCD)
Flat panel image receptor (FPIR)
T/F
The IR in the digital fluoro system replaces the TV camera tube on the output of the II
True
What is the sensing component of a CCD?
A layer of crystalline silicon
Mounted on the output phosphor of the II tube and is coupled through fibre optics or a lens system
Charged coupled device
Composed of cesium iodide/amorphus silicon pixel detectors
Much smaller and lighter and is manipulated more easily than an image intensifier
Flat panel image receptor
T/F
In conventional fluoro, the II is limited by non-uniform resolution and contrast resolution from center to periphery, but digital FPIR is uniform over the entire receptor and does not degrade with age
True
What SNR was present in conventional fluoro?
200:1
What SNR is necessary for digital fluoro?
1000:1
What are some advantages of flat panel display over CRT monitors?
-easier to view and manipulate
-better resolution
-lightweight, easy to see
-can be ceiling mounted
Xray exposure is not continuous and has gaps of no exposure between each image frame
Pulsed fluoro
T/F
Pulsed fluoro can reduce patient dose and decrease the visibility of patient motion
True
T/F
For pulsed fluoro, the xray generator must be capable of switching on and off very rapidly
True
Time required for the xray tube to be switched on and reach selected levels of kvp and mAs
Interrogation time
Time required for the xray tube to be switched off
Extinction time
The time that the xray tube is energized
Duty cycle
-reduced dose to patient
-increased image noise
Low dose rate
-reduced image noise
-increased dose to patient
High dose rate
What is the principal advantage of digital fluoro exams?
Digital subtraction techniques that are possible and the enhanced visualization of vasculature that results from venous injection of contrast material
DSA - digital subtraction angiography
T/F
DF provides better contrast resolution through post processing of image subtraction
True
Achieved when an image obtained at one time is subtracted from an image obtained at a later time
Temporal subtraction
-mask mode
-time interval difference mode
Occurs when patient motion occurs between the mask image and a subsequent image
Misregistration artifact
Solution:
Pixel shifting - reregistration of the mask
Remasking - use another image as the mask image
What happens with ABC when the generator increases mAs?
-contrast preserved
-patient dose increases
The ability to resolve fast moving objects
Temporal resolution
T/F
Fluoro images provide excellent temporal resolution but are relatively noisy
True
Digitizing the fluoroscopic images and performing real time averaging in computer memory for display
Frame averaging
* individual frames are weighted and averaged into a single display image
What is the principal advantage of DF?
Digital subtraction techniques
*DSA - digital subtraction angiography
Achieved when an image obtained at one time is subtracted from an image obtained at a later time
Temporal subtraction
What are the 2 methods commonly used for temporal subtraction?
Mask mode
Time interval difference mode (TID)
Results in the successive subtraction of contrast filled vessels
Mask mode
An initial pulsed exposure is made after injection of contrast media, before the bolus reaches the anatomy under investigation
Mask image
Occurs when patient motion occurs between the mask image and a subsequent image
Misregistration artifact
Solution:
Pixel shifting - reregistration of the mask
Remasking - use another image as the mask image
Uses two alternating energy xray beams to provide a subtraction image
Energy subtraction
Combination of temporal and energy subtraction techniques
-filled mask mode procedure
Hybrid subtraction
A special application of DSA used to create a map of vascular anatomy that aids the navigation of catheters
Roadmapping
Where should the xray tube and II be positioned in relation to the patient?
Xray tube - under
II - above
