Digital Fluoroscopy

Advantages of DFPDs over conventional fluoroscopy are what?

- contrast enhancement for low subject contrast structures -high detective quantum efficiency (DQE) -high dynamic range -freedom from various forms of distortion -rectangular shape which correspond to display monitors

Static DR detector pixels = ? Dynamic FPD pixels = ?

100-150 microns 200-300 microns

Many of these units have features that require operation at _____ or _____ mA, so it is possible for what?

200 to 300; possible patient exposure to become very excessive

A digital fluoroscopy unit usually has ____ viewing monitors so one can be used to display ________ images or to ________ previous images

2; subtraction; hold

The pulse width on these units can be adjusted from ___ to ___ milliseconds

3 - 10

With pulse progressive mode the usual frame rate is what?

30 frames per second

What is pulsed progressive mode?

A series of very short bursts of radiation rather than continuous exposure

You should keep radiologists and surgeon apprised of the what?

Accumulated fluoro time

With dual-use flat panel systems to operate in fluoroscopic mode, groups of 4 small pixels are __________ together to form larger pixels with dimensions of 200-300 microns

Binning

Dual-use flat-panel systems allow what?

Both radiography and fluoroscopy to be performed

Superimposition of the positive mask over an original image results in the ____________ of all pixel values leaving a featureless medium gray across the entire field, except for the ___________ which was present in only one of the two images

Canceling out; contrast medium

Digital subtraction techniques are used in _______________ procedures to dramatically improve the visibility of the contrast agent filled anatomy of interest

Cardiovascular

Indirect detectors use a ____________ coupled to an active matrix array of ____________ TFTs

Cesium iodide; amorphous silicon

Dynamic flat panels detectors can operate in either __________ mode or __________ mode

Continuous x-ray; pulsed x-ray

Image intensifier tunes are being replaced by what?

Dynamic flat panel detector system

_____________ subtraction uses the difference in x-ray absorption between tissues at different kVp levels

Energy

Image contrast is not as good for __________ subtraction as for ____________ subtraction but can be greatly improved by do,inning the two methods into what?

Energy; temporal; hybrid subtraction

With pulsed progressive mode fluoroscopy units can operate at an mA measured in the _________

Hundreds

With dual energy subtraction by taking exposures just above and just below the k-edge of iodine, the computer has a way to ________ the _________ and subtract all other ________ from it

Identify; iodine; tissue densities

Two types of dynamic FPDs are available being what? The physics of how these work is the same as what?

Indirect detectors and direct detectors Static flat panel detectors

What is a principle advantage of digital fluoroscopy over conventional fluoroscopy?

Is that Individual image frames made possible by the pulsed mode allow in image subtraction techniques to be used to enhance visualization of anatomical structures filled with Cm

Dual energy subtraction takes advantage of the _______ x-ray absorption for iodine

K-edge

Compared with static detectors, dynamic FPD have what?

Larger dimensions Larger matrix sizes (up to 2048x2048) Larger pixel sizes

A _________________ array, located below the detector produces a bright microsecond flash of light to erase ghost I,ages after each frame is exposed These ghost image are actually a change in _____________ of the detector after exposure, which shows up only on the next exposed image

Light-emitting diode (LET) Sensitivity

By selecting a 3 millisecond pulse width rather than the common 6 msec pulse width, patient exposure can be what?

Reduced by one-half

Dual energy subtraction requires the rapid ____________ of either the kVp or the filtration between two exposures To switch filters, they are rapidly placed on a spinning _________

Switching; fly wheel

_____________ subtraction uses the difference in time between exposures

Temporal subtraction

___________ subtraction is both more economical and technologically easier to achieve for the equipment, than ___________ subtraction

Temporal; energy

Temporal subtraction refers to using the difference in _________ to distinguish between exposures that will be subtracted from each other

Time

Most DFPDs have a ________ feature analogous to the "magnification mode" used on image intensifiers

Zoom

Although patient dose is saved by the gaps between exposure frames, extremely high _____ levels can cancel out this savings and high pt exposure can be a serious issue with these units

mA

Direct detectors use an AMA of ____________ TFTs

Amorphous selenium

Temporal subtraction 1. An exposure is made ________ the injected contrast agent reaches the anatomy of interest 2. From this image with no contrast agent present, the computer creates a __________ (black on white image by using reversal algorithms) 3. The computer then effectively ____________ the positive mask image over ___________ filled image, adding together the pixel values across the field

Before positive mask superimposes; negative contrast