Specialized/alternative imaging Flashcards
Fluoroscopy is
Form of radiography that uses real time imaging of internal structures with a continuous beam of x-rays
Not still pictures as traditional radiography
Primary function is to provide dynamic real-time imaging of anatomical structures
Diagnostic process is enhanced if veterinarian able to view certain activities within the body as they happen
How does fluoroscopy work
Uses low mA and high kV settings
Time not independently selected as image is created in real time
Controlled by radiographer through use of a foot switch
As long as foot switch is depressed an exposure is occuring
How does the fluoro table work to produce images
Radiation comes from under the table through the patient and onto an image intensifier
Image intensifier receives radiation and converts it to a visible light image – called photoemission
Image sent to a monitor
Image viewed is the opposite of an x-ray – positive image
Black and white areas are reversed
C-arms are an example of type of fluoroscopic unit
When to use fluoroscopy
Minimally invasive repair
Intraluminal stenting for treatment of tracheal collapse
Urethral and colonic obstructive disease
Vascular procedures
Contrast studies of the GIT
Safety concerns for fluoroscopy
Very similar to general radiography, but has real-time component
Recognize radiation generally comes from beneath table (opposite of regular radiography) so use appropriate safety measures
ie: don’t cover hands with gloves
Exposure times are much longer – try to minimize as much as possible for safety of both worker and patient
ALARA
What is computed tomography showing
Technique used to show, in detail, images of structures that lie in structures that lie in predetermined plane of tissue while blurring or eliminating structures above and below that set plane
Uses same principles with advantage of computer to enhance image and ability to show multiple images or “slices” of structures of interest
How does a CT scan work
Works by having x-ray tube connected to image receptor
X-ray tube moves in an arc across table and image receptor follows that arc exactly (but in opposite direction)
Structures at a set point (fulcrum) will remain in focus and structures above and below that point will be blurred
Object of interest is positioned at focal plane (fulcrum)
Tube and receptor are attached
As long as tube and receptor move in unison they will maintain uniform focal plane and produce an image in focus
Image blur of a CT is
Slice thickness determined by operator of CT
Slices thinner than a mm are able to be acquired
Employs x-ray machine that acquires images that look like slices in loaf of bread
Uses detectors and computer
X-ray tube rotates 360 degrees around a gantry (opening in center of machine where table enters)
Opposite the tube are several detectors that rotate at the same speed as the x-ray tube
Two types of CT
Conventional
Spiral/helical
Conventional CT images are
table moves in increments so that several images/slices are taken for a complete examination (start-stop)
Spiral/helical CT is
continuous rotation of tube head/detectors and motion of table
How does CT produce an image
The detector will translate the image into shades of grey on a matrix
Original tomographic principle remains: 1 tube – 1 detector
X-rays pass through patient and the attenuated beam is collected by detectors
Detectors convert photons to an electrical signal, which is then converted to digital signal, which is transmitted to the computer
Computer reconstructs the image
What happens to CT after image is taken
Scan data (raw data) from detectors is used to create the image
This information is very large so is only temporarily available from the scanner
Final image is either photographed onto films or saved on a network (PACS) as picture files
Newer technology able to convert 2D images into 3D
When would you use CT
Can be used for special contrast procedures such as:
Angiograms
Used to visualize abdominal organs
Infections within extremities
Cross-section imaging of both soft tissue and bone
Safety considerations for CT
kV and mAs used in CT much higher than standard radiography
Higher the technical factors in CT, the nicer the image
ALARA!
Scan time
Usually means the time it takes the x-ray tube to rotate 360 degrees around the patient
