Advanced Imaging Flashcards
How does CT work?
X-ray generator and detector rotate around the patient wiring images, data is reformatted into different planes and windows to optimize a valuation of different structures
5 indications for CT
- to better characterize Ossetia injury – surgical planning (fracture repair, osseous debridement) – imaging of the skull – to assess vascularity – guidance for FNA/biopsy
Six advantages of CT
– Shorter exam time
(– lower risk of anesthesia and we’re coming to you – can be done in conjunction with other procedures without excessive and seizure/recumbency time – motion artifact less of an issue)
– excellent osseous detail – Great for image guided procedures – better spatial resolution - less expensive – standing units now available
Four disadvantages of CT
– ionizing Radiation
– contrast resolution not as good as MRI
– anesthesia still required
– limitations based on bore size and limits of x-ray penetration
**how MRI works
– Uses a strong magnetic field and radio frequency pulses to develop a digital image
– hydrogen protons in different tissues respond differently
Four indications for MRI
-when most complete a valuation is desired and distal appendicular skeleton (lesion extent, severity, involvement of other structures)
– soft tissue injury within hoof capsule expected
– imaging the brain
– when early intervention needed (confirmation of septic arthritis/osteomyelitis)
Three advantages of MRI
– Excellent contrast resolution (gold standard for soft tissue)
– only modality that allows for a valuation of trabecular bone fluid (inflammation, contusion, Edema)
– standing magnets available (limitations)
Six disadvantages of MRI
– Longer examination time
– expensive
–anatomy that can be imaged is limited by bore size
– Quality dependence on field strength
– extremely focused exam
– image interpretation requires expertise
What diagnostic should be performed before to acquire a more accurate MRI
Multiple blocks pirate imaging – more detailed walking pattern = more accurate MRI
High field MRI systems – Four advantages and four disadvantages
Advantages – superior image quality, reduced scan time with thin slices, large field of view, and general decreased artifacts
Disadvantages – cost, reduced availability to patients, General anesthesia, position can be difficult
Lowe field MRI systems – four advantages and four disadvantages
Advantages – lower cost, more available, most do not require general Anesthesia, easy positioning of the horse
Disadvantages – lower image resolution, small field of view, anesthetized studies take a long time, more artifact often due to motion
Three times to choose a High field MRI
Mild lameness/subtle injury suspected,
major diagnosis is joint disease (cartilage imaging)
lameness localizes proximal to foot
Four times to choose a lower field MRI
– Anesthesia contra indicated or not worth the risk
– more severe injuries suspected
– lameness reliably localized to the front
– serial recheck examinations
How nuclear scintigraphy works
A radiopharmaceutical is administered IV, that emits gamma rays bound to methylene diphosphonate (MDP). MDP has an affinity for hydroxyapatite crystals in bone. Increased radiopharmaceutical uptake in areas of abnormal osteoblast maturation and mineralization. Emery is embedded from the body undetected by a gamma camera and converted into an electrical signal. Final image represents an anatomical map displaying regions of various degrees of increased bone turnover.
Nuclear scintigraphy - three phases of image acquisition and timing of those phases
- Vascular flow phase – immediate
- Soft tissue phase – within 10 minutes
- Bone phase – 2 to 3 hours
