Neurodiagnostics Flashcards
What imaging modalities are available for dogs and cats with CNS disease?
- radiography
- contrast radiography
- ultrasonography
- scintigraphy
- CT
- MRI**
- thermography
What are the 5 major indications for radiography for diagnosing CNS disease?
- screening for bony lesions
- skull/vertebral tumors
- spinal fractures/luxations
- skull fractures
- diskospondylitis, vertebral physitis
How can image quality of radiographs be improved? How is it used to make diagnoses?
general anesthesia
- prelude and screen before myelography and MRI
- intraoperative implant positioning
- NOT commonly used as a primary form of imaging
Although myelography is not commonly performed, what is considered some advantages? Disadvantages? What can it be combined with?
speed, availability, cost
side effects common, poor image quality compared to MRI
CT
What are the 2 ways of injecting contrast for myelography? What side effect is most common?
- cisternal
- lumbar - better quality images, safer
seizures, neurological deficits - most common in large dogs with neck issues
What is computed tomography? How does it work?
X-rays and computers used to create cross-sectional images with 3D reconstruction capabilities
different tissues will attenuate X-rays to different degrees, resulting in different linear attenuation coefficients (Hounsfield units)
- bone = white (+1000 HU)
- air = black (-1000 HU)
- fluid = gray (0 HU)
How are CT images manipulated?
- choose a central gray color to the HU of the tissue of interest = window level (WL)
- choose number of shade allowed in the image = window width (WW)
What is the purpose of narrowing and widening WW of CT images?
NARROWING = soft tissue, like brain parenchyma, to improve contrast resolution (WL 35, WW 150)
WIDENING = tissues with good contrast already, like bone (WL 420, WW 1500)
What is the purpose of contrast CT?
administration of IV non-ionic iodinated contrast to highlight areas of BBB disruptions
What is the most common type of CT performed? How does this compare to conventional?
3rd generation - images acquired by rapid rotation of W-ray tube 360 degrees around the patient as the table moves = spiral-shaped continuous data set without any gaps
planar sections take of patient with gaps
What is CT especially helpful for diagnosing?
- acute brain injuries
- brain and spine imaging
(can be combined with myelography)
What are 4 advantages to CT imaging?
- fast
- less expensive to maintain than MRI
- good for imaging bone and acute hemorrhage
- 3D reconstruction capability
What are 3 disadvantages to CT imaging?
- ionizing radiation
- beam hardening artifact - low-energy photons are absorbed more than the high-energy photons, resulting in streaking and cupping
- less soft tissue detail compared to MRI
What are the 5 most common uses of CT imaging?
- acute brain injuries
- spinal trauma with fracture/luxation
- after hours emergency when MRI is not available
- pre-operative planning
- post-operative assessment of implants
What are the 2 major ways of obtaining a CSF sample? What can alter results?
- cisternal - C1-C2
- lumbar - L4-L5 larger, L5-L6 smaller
(general anesthesia)
hemorrhage can increase cell count and protein levels