Angio A Flashcards
what is DSA
- diagnostic imaging method that uses a computer to convert the attenuated x-ray beam into digital information, which can be manipulated and /or stored
- involve removing or subtracting background structures from an image so that only contrast media filled structures remain
what is zero image
- images taken before contrast administered
- shows only bony structure
what is mask image
image reversal to create positive mask image
what is series image
- dynamic images that were exposed while contrast was being administered through an artery during “angio cine”
- power injector administers contrast through catheter in patient’s right femoral artery to vessel of interest
- images are taken in rapid sequence
- these images will be processed later for subtraction
difference between single plane and bi-plane system
single plane
- usually larger II size = larger FOV
- save space
bi-plane
- naming of plane: A-B, AP-Lat
- usually smaller footprint “II size”
advantages of bi-plane system
- save contrast
- save time
- true 3D relationship
what is pulsed fluoroscopy
- used as a method of reducing radiation dose, particularly when the pulse rate is reduced
difference between fluoroscopy and image acquisition
fluoro
- continuous display of images normally without recording, except LIH and store fluoro
acquisition
- discrete (spot image) or multiple images recorded in sequence
- run or cine
characteristics of angiographic x-ray tube
- high anode rotating speed, about 10,000rpm
- small tube angle, between 7 and 10 degrees
function of collimators
- limits the x-ray beam to an area of the operator’s choice
- reduces exposure to patient by reducing volume of tissue at risk
- reduces scatter radiation at image receptor
- dual-shape collimators
what are partially absorbent filters used for
control the bright spots produced by the lung tissue bordering the heart
what is high filtration
additional copper/ aluminium filters
- reduce skin dose by more than 70%
- preferentially absorb the lower energy photons
- some system offers variable extra filtration that is automatically set according to patient weight and angulation of C-arm
how does magnification mode affect radiation output
ABC increases patient dose with increased MAG
characteristics of viewing monitors
- clean
- compact
- light
- manoeuvrable
how is series images acquired
- as the c-arm rotates around the patient
- can be viewed as a cine loop, or used to reconstruct as cone-beam CT images with or without background subtracted
how is multiple oblique 2D view acquired
- in one rotation and contrast injection, hence more info than just AP and lateral on a pathology
- mask run done before contrast run
contrast injected speed
- consistent speed
- faster in abdo angiography
- slower in lymphangiography
major components of automatic electromechanical injectors
- control panel
- pressure mechanism
- syringes
- warming system
what type of imagings are there
injection delay
scan delay
DSA image manipulation
- noise smoothing
- edge enhancement
- re-masking
- pixel shift
- landmarking
- overlay
- road map
- quantitative measurements
what is image manipulation
- an attempt to decrease visual prominence of noise
- reduce resolution
what is edge enhancement
- increase the visibility of small structures with moderate high contrast
- increases noise level
what is re masking
- if initial mask is inadequate because of patient motion, improper technique or other reasons, later image scan can be used as mask image
what is pixel shift
- if patient moves between the acquisition, image obtained will be registered exactly to the same pixel of image matrix
- eliminated by re-registering of mask
- done by shifting mask image over the series image
- hence better superimposition of image obtained
what is land-marking
adjusting the % of background on any subtracted images
what is overlay
- ordinary live fluoroscopy procedure and all background information will be seen during live fluoro
what is road mapping
- creation of roadmap mask: the post contrast frame with the highest vessel opacification is identified –> roadmap mask
- live fluoro with subtraction
what is quantitative measurements
normal left ventricular ejection fraction ranges from 55-70%
