Lecture 5- Fluoro Flashcards
which of the following is not an attribute of a fluorscopy vs. radiography
d
what is flour used for
real time X-ray imaging of anatomy with X-ray contrast agents or devices.
what is the difference between fluoro and cine
cine is higher dose for diagnosis and device placement while fluoro is used for navigation and localization
what is angiography
injection of contrast into vessels
what is not in a fluoroscopy X-ray assembly
output phosphor
what interaction creates xrays
bremsstrahlung
does the cathode give or take electrons
cathode gives the electrons.
what do filters do and what do collimators do
filters reduce the low energy rays so it decreases overall patient dose. the collimator restricts the field of view
what is a KAP meter
it is a radiation soe meter
what is AERC
automatic exposure rate control that set dose to be reserved so increase or decrease output so that patient gets a higher or lower dose
why is the dose per image lower for fluoro
it is given over a longer time so they need a lower starting dose per image
what is typical per pulse for fluro, acquisition, digital subtraction, and digital radiography
10-40, 120-250, 2000-4000, 5000-10,000.
what is the problem with noise from electrical components
needs to be very low because the signal is already low
what are X-ray control parameters
peak tube potential, beam filter, current, pulse duration, frame rate per second, collimation and field of view
what is usually used as a filter
copper
what happens to the spectrum when a copper filter is used also draw the changes in HVL
copper filters are used and it shifts the energy to the right because lose lowe energy. Image contrast reduction but decreases the dose significantly while only lowers contrast csome
when is the machine on and off for fluro
it used to be on constantly then the receptor pulsed, but not the X-ray is mostly off and the receptor is always on
how does AERC contribute to image quality
it does not normalize image quality. it only controls the specified radiation dose. due to changes in subject contrast with changes in KVP and contribution of scatter, AERC does not result in equal images for each condition.
as patient thickness increases, the SNR
decreases
what are the drawbacks of large patients
as KVP increases the subject contrast decreases, and the dose increases as the current increases, aAS the pulse duration has to increase, the blur increases as well. High anode heting is required for larger focal spot and there is larger penumbral blur. As scatter to primary increases, the SNR decreases. the net effect is that large patient equals large dose which decreases image quality
what is the risk of using iodine as contrast
kidney nephropathy
what is attenuation
absorption and scatter of X-ray beam by the patient substantially reduces the X-ray beam intensity AERC
what is the primary source of occupation exposure to xray
scatter fom the patient
what happens to X-rays that do not interact with tissue
it is transmitted
X-rays that interact- what happens
they are attenuated, which leads to scatter or some energy absorbed which is the radiation dose
what is the formula for exponential attenuation
It=Ioe-ut It is the transmitted insanity, I0 is the incident intensity, u is the linear attenuation coefficient, and t is the thickness
what does differential attenuation do
it produces modulation in X-ray intensity, image contrast, and so this is how images look different as it goes through different tissue
thicker patients means what to KEVP
it needs increased KEVP
what happens to the contrast potential of iodine
it decreases rapidly further to the right and this lowers the contrast potential
what is forward scatter
these are rays that go towards the detector and contribute to noise and decreased quality of the image
what is side scatter
occupation radiation
what is back scatter
occupation and contributes to the higher dose overall
what does an anti scatter grid do
it transmitters 80-75% of the primary and it transmitts 10-30% of the scattered beam. It improves the signal to noise ratio
what is the bucky factor
how much the dose must increases to make up for the grid taking out some of the primary
what does the detector do
it creases a shadow then image
what is an image intensifier
it makes the image better by turning low energy things into higher energy things
what is not a part of an image intensifier
photoiodide
what does an input screen do
the cesium iodide scintillator covers the X-rays into visible light
what does the photocathode do
it concerts the visible light into free electrons
what is the k edge of the scintillator
33 kev
what is the photocathode made of
thin layer of antimony and alkali metals which emit electrons in response to visible light. very low conversion efficiency
what is a focusing electrode
it focuses on the photocathode onto the output screen
what is the brightness gain
it is the acclearation of electrons between the input screen and output screen
what is the brightness gain range
is it 2500 to 7000
what deformity can be caused by electron optics and speeding up
pincushion deformity
what is the role of the output screen
it is positively charged, so it attracts electrons and converts the moving electrons to visible light
what is optical coupling and what is it coupled to
output phosphor is attached to the camera, and it creaates the image
is higher or lower SNR better
higher
what is a CCD camera
it is a charge coupled device that couples the phosphor with the lines and aperture can lose SNR of it
what is a CMOS camera
light to electrons, but each puzzle has its own ADC and sends its own things, so no stepping between the detector
magnification mode with II
uses a smaller field of view, so it uses a small II area, so the entire area of output phosphor is used, and it increases the object plane-spatial resolution.
does the increased magnification increase dose
it used to increase dose because it needed to maintain the output phosphor intensity and electron density, but requires an increased intensity and increased technique
what is quantum detection efficiency
want to absorb lots of electrons and it is not a good decrepit of the detector to efficiently covery all X-ray fluency into a useful image
flat panel what is the shape of the electrophores
the electrophorus are discrete
what is the chemical used in this pixel
Cesium iodide
how is the electric charge propogated through flat panel detector array
electronic charge is released pixel by pixel, amplified, and converted to a digital value by an analog to digital converter. Utilizes solid state and miniaturized components. Electronic noise results in lost SNR for low dose fluoro
what happens to the stored charge in a flat panel detector
it is released, amplified, analog to digital, converted to digital, and sent to an image processor
what happens to magnification with flat panel
it becomes gridy looking
are images from fluro saved to the patient record
no
what happens with continuous fluror
it is X-ray beam is continually on and creates images at 30 fps, and it is still used for portable
what is pulsed fluoro
it is where the beam is switched on and off, and images at created at that rate. It is more common for angiography systems
what is the dose rate of cine compared to fluro
it is 10-20x the rate
are cine continuous or pulsed and are the images saved
images are saved, and it is at 15fps and the beam is pulsed and images are created at that rate
DSA what is it and whats the rate and what is it used for
dose rate is higher than flour and it is used for vascular imaging, and used for diagnosis
is DSA pulsed or continuous
it is pulsed and it is usually 2-4 fps
what is the point of DSA
it can subtract overlying anatomical noise for better vessel pictures
what are the methods behind DSA
acquire a mask of image of the anatomy, inject contrast into the vessel of interest. Acquire contrast image of the amantomy and contrast vessel then transform to subtract it
what happens to noise when you use DSA
it decreases the noise because it subtracts other random noise as well DSA source images are high dose and high SNR
what does a c-arm do
it can cone CT and recontruct the path of the arm
what is the issue with cone beam CT or c-arm
it has streak atrifacts and high density and moving objects- limited rotational range
what is the application of cone beam CT and angio
it can show native anatomy and measurements with device placement
cone beam and angio are applied to what for the heart procedure
TAVR
what happens to contrast in fluoro
signal difference between object of interest and neighboring anatomy
what happens to noise in fluoro
small area variation in signal intenstity due to random nature of X-ray production and detection
what happens to spatial resolution in fluoro
spatially lateral spread of signal within the imaging system. Penumbral blur, light spread, and X-ray scattering
what happens to signal difference in fluoro
grayscale intesntity difference between object of interest and surrounding image
what happens to resolution in fluoro
spatial precision which small objects and sharp edges are produced
what happens to noise in fluoro
random, small area, greyscale intensity variation due to the random nature of X-ray production, attenuation, and detection
what happens with when the signal increaseds with fixed noise
it can still be seen just fine, so sometimes the image is fine with more noise
what leads to blur in terms of modelign
the lateral spread of the signal when it is transformed from a point stimulus to a point spread function leads to blur. the spread is from convolution
flat panel does what with spatial resoltuon
flat panel has less things affecting spartial resolution
what happens to spatial resolution as the field of view increases
resolution decreases with field of view because larger input phosphor are is forced onto a discrete matrix. Resolution decreased with the field of view because large FP pixel matrix is forced on a a smaller matrix electronic display
what is image perception influenced by
technical image quality, image processing, visual acuity, experience, clinical context
what tissue gets the highest dose in fluoro
skin
what determines how the dose changes over a depth
inverse square law
what monitors tube output
it is from air karma, It is a virtual point in space.
what does air karma lack
correct Xray source to skin stance, correlation with skin irradiated, skin dose contribution from scatter internal to the patient
what is the maximum air karma for fluoro
87.3 mgy/min
what is the high level control max rate of fluoro
175 mgy/min
is the max air karma rate distance the same as the image receptor
no it is at 30 com from the X-ray tube which is not the IRP
is there a limit for maximum cine air karma rate
no
what patients are most likely to get skin injury
large patients and complex lifesaving procedures
what is the threshold dose for skin injury
2gy
