Neuro Imaging Flashcards
1
Q
- diagnostic that uses numerous x-rays shots as cross-sectional slices
- digital images reassembled by computers and produces a “3-dimensional” image
- the dark image is least dense objects, bright is the most dense (air < CSF < soft tissue < blood < bone)
- keep in mind laterality, observing patient from an inferior view
A
CT/CAT (computer aided tomography) scan
2
Q
What are the advantages and disadvantages of CT scan?
A
- advantages: fast (excellent for trauma situations, quick for detecting brain bleeds), good for skull and facial bone imaging for fracture
- disadvantages: lower resolution on soft tissue/brain, cannot detect acute ischemic strokes (aka, just b/c someone appears to be having a stroke and CT is negative from stroke, that does not mean they aren’t actually having one)
*Dr. Chou said this important info*
3
Q
What is the common post-traumatic presentation of an epidural hematoma?
A
- epidural hematoma: fast arterial bleed out of the dura (commonly the middle meningeal A. from a skull fx)
- dura separating from skull but dura is strongly attached at cranial sutures (thus blood does not cross suture lines), this forms elliptical/lemon/lens shape
- classic patient hx: head trauma sustained > unconscious > lucid interval (no sx) > loss of mental status (due to cranial pressure)
4
Q
What is the common post-traumatic presentation of a subdural hematoma?
A
- subdural hematoma: rapid change in velocity > stretch damages bridging veins under dura
- common in elderly patients due to reduced brain volume increasing strain on veins
- blood is not restricted by suture lines, but is limited by falx cerebri (wider spread), creates a crescent/banana shape
- increased pressure > brain herniation (life threatening)
- classic patient hx: elderly patient on blood thinners that falls and sustains head injury
5
Q
- diagnostic that uses powerful magnetic field and radiofrequency waves to manipulate protons in water and fat which generates an image
A
MRI (magentic resonance imaging)
6
Q
What is the basic “sequence” of an MRI?
A
- magnetic field lines up randomly aligned protons
- radiofrequency pulse > changes proton aligment in magnetic field
- radiofrequency pulse deactivates > protons realign w/ magnetic field > release energy which is read by MRI machine
7
Q
What are the advantages and disadvantages of an MRI?
A
- advantages: highest resolution, very good for defining structure/soft tissue lesions (different sequences and images, example T1 vs T2 in the photo)
- disadvantages: slow imaging technique can cause claustrophobia in some patients, no metal implants can be used (aneurysm clip is okay, some pacemakers are MRI safe), sensitive to movement (movement artifact on imaging), not as good at imaging bones lesions/fx
*Dr. Chou high yield info*
8
Q
What is the purpose of changing the MRI sequence and how is this done?
A
- purpose: changing sequence changes color of tissues/fluids > produces contrast between different structures
- change by: repetition time (TR, time between RF pulses); time echo (TE, time between RF pulse and receipt of energy from protons)
9
Q
How will a T1 weighted MRI sequence appear on imaging and what is it best used for?
A
- T1 will look like normal anatomy: white matter = white/light gray; gray matter = gray/dark gray
- good for assessing anatomy/soft tissue tumors, easy to see disruption of BBB (by contrast leak > blood is bright)
10
Q
How does the T2 weight MRI sequence appear on imaging and what is the indication for use?
A
- T2 will appear opposite of T1, white matter is dark gray
- indication: good for seeing demyelination (white matter injury on R image)
- con: difficult to visualize inflammation next to ventricle
11
Q
In what situation would you want to use a T2 FLAIR MRI sequence?
A
(FLAIR = fluid attenuated inversion recovery; similar contrast to regular T2 but CSF appears dark)
- indication: checking for inflammation near ventricles
12
Q
How do you decide to use either CT or MRI?
A
CT
- advantages: very fast, excellent for imaging acute hemorrhage or trauma (facial bones)
- disadvantages: difficulty imaging soft tissue/brain structure, cannot detect acute ischemic stroke
MRI
- advantages: highest res, can add sagittal plane view, excellent for differentiating soft tissue and brain structures, obtain in a non-emergent event where acute bleed is not suspected and patient may have had CT in the past, also when you are planning on referring to neuro or surg
- disadvantages: slow, motion artifact
*Dr. Chou high yield content*
13
Q
What is contrast used for in imaging?
A
- used to find things that disrupt BBB (nml brain will not appear different)
- CT uses iodine contrast, MRI use gadolinium (both can cause kidney injury)
14
Q
- used to view brain vasculature, neck vasculature, and circle of willis (done by fluoroscopy, CT, or MRI)
- indications: stroke/TIA, aneurysm, vascular malform
A
angiography
15
Q
- maps out brain activity
- detects changes in blood flow (blood flow a/w neuronal activation, regions responding to diff stim, regions executing diff tasks)
- mostly used in research, some clinical use
A
functional MRI
17
Q
- diagnostic where dye is injected below the dura (intrathecal) and imaged by fluoroscopy
- helps visualize space between nerves and structures around it: spinal stenosis/herniated discs, masses on SC, spondylosis/arthritis
- uncommon modality, replaced by CT/MRI, may be obtained if MRI cannot be tolerated
A
myelography
18
Q
- diagnostic that uses echolocation to produce an image
- transducer creates _______ w/ piezoelectric material in the transducer
- able to differentiate soft tissue structures well
- indications: point of care used for quick dx and guiding procedures
A
ultrasound
19
Q
- diagnostic used to assess arterial supply to brain
- after TIA or ischemic stroke
- assesses for carotid artery stenosis (plaque build up > clots)
A
carotid ultrasound
20
Q
What is the purpose of doing ultrasound guided procedures?
A
- easy bed side needle guidance
- can target nerves for procedures (ex. steroids)
- can be used for nerve blocks for surgery w/ local anesthesia instead of placing patient under general anesthesia
23
Q
- used to detect injury to cornea
- steps for procedure: topically applied to coat eye, blinking used to spread, shine slit lamp blue light
- injured corneal tissue will shine bright green, highlights foreign bodies
A
fluorescein stain
