Neuro-radiology Exam 6

What positions are skull radiographs taken in? (2)

• AP

• Lateral

What is the benefit of using skull radiographs?

• Used a lot for foreign bodies

  • Hardware: clip, coil, ventricular shunt catheters

• Initial imaging for a trauma if CAT scan is delayed

• Fractures or metastatic tumors: radiolucent

• Sinus disease: opacification, air-fluid levels

What positions are cervical spine radiographs taken in? (3)

• AP

• Lateral

• Odontoid (open mouth to see articulation of C1, C2, and the dens)

Used for initial spine clearance in trauma survey (C7 and C7-T1 junctions)

What positions are thoracic spine radiographs taken in? (2)

• AP

• Lateral 

What positions are lumbar spine radiographs taken in? (4)

• AP

• Lateral

• Oblique

• +/- flexion/extension

What positions are sacral spine radiographs taken in? (3)

• AP

• Lateral

• Oblique

What is the mechanism of CT scans?

• Takes multiple axial x-ray films at successive layers to get 2nd generation reconstructions

What are the different densities of CT scan? (7)

• Brain → isodense → gray

• Bone → dense → white 

• CSF/water → hypo-dense → dark gray 

• Air → hypo-dense → dark gray

• Blood 

  • Acute → dense (due to iron) → white

  • Subacute → isodense → gray

  • Chronic → hypo-dense → dark gray

What are the benefits of CT scan with no contrast? (4)

• Good to look at fluid filled spaces

  • Assess patterns of hemorrhage

  • Determine ischemic vs hemorrhagic stroke

• Bone window evaluation for fractures

• Assess ventricular size

• Spine

  • Cervical, thoracic, and lumbo-sacral: axial and sagittal reconstructions, assess function and instrumentation

What are the benefits of CT scan with contrast? (3)

Indications 

• Infection

• Vascular 

• Neoplasm 

What do we have to be aware of when giving contrast for CT scan? (2)

• Allergies: range from mild flushing to anaphylaxis

  • Can pre-medicate: steroids, Benadryl, GI prophylaxis

• Cannot give if Cr > 1.5

  • Can be given to dialysis patient

What are the benefits and drawbacks for CT angiography?

Benefit

• Evaluates vasculature and tissue: one step above CT with contrast

  • Uses a larger bolus (large bore IV) at timed intervals

Drawback

• May be obscured by metallic metal (orthodontic)

What are the benefits of using MRI? (6)

• Good for assessing soft tissue and anatomic detail 

  • Higher the T → better magnet → clearer image

• No radiation 

• Good for assessing acute ischemia and demyelination

• Good for assessing posterior fossa

• Good for brainstem evaluation 

• Good for surgical planning 

What are the different MRI sequences? (9)

• T1: normal

• T2: abnormalities show up

• PD: evaluation of menisci and gray/white matter

• STIR: determine old vs new fracture

• DWI/ADC: ischemia/abscess/infection

• FLAIR: white matter abnormalities

• In-Out: characterize adrenal lesion

• GE: detect blood products

• SE: fewer susceptibility artifacts

What are the limitations to using MRI? (5)

• Cannot do if there is metal containing iron

• Cost and availability

• Claustrophobia

• Body habitus

• Renal failure

What are the benefits of Gadolinium (1) vs no Gadolinium (4)

Without

• Acute stroke evaluation

• Congenital lesion

• Screening

• Renal failure

With

• Breakdown of BBB (tumor, infection, vasculitis)

What is the benefit of SPECT?

• Measures tissue metabolism

  • Can differentiate Alzheimer’s (overall decreased uptake) from vascular dementia (patchy decreased uptake)

  • Immediately following seizure can show seizure focus

What is the benefit of PET?

• Evaluates brain metabolism 

  • More detailed: can pick up smaller areas of metabolic activity

  • Brain tumors

  • Stroke

  • Dementias

What is the benefit of cerebral blood flow scan?

• Show anywhere that BBB has been disrupted 

• Can show brain death: shows lack of blood flow to the brain with presence of blood flow to the scalp 

What are the general principles behind MRI special tests MRA/MRV, functional MRI, and diffusion tensor imaging

MRA/MRV

• Assesses blood flow

• MRV requires contrast

• May overestimate stenosis

fMRI

• Lights up areas of the brain that are functioning while the patient is performing a specific task

DTI

• Demonstrates directions of diffusion in white matter tracts

What are the general principles of special studies CSF flow and ultrasound?

CSF flow studies

• Use cine MRI that is coupled with heart rate to track CSF flow through ventricular system

Ultrasound

• Can use trans-cranial doppler for vasospasm, stroke, and flow

What is the benefit of using CT myelography?

• Useful in patients who cannot have a MRI

• Allows for visualization of the space of the spinal canal, spinal cord, nerve roots, and meninges by using intrathecal contrast

  • Detect pathology of spinal cord: spinal cord injury, cysts, tumors

What are the benefits (1) and limitations (4) for cerebral angiography?

Benefits 

• Gold standard for visualizing internal vasculature 

Limitations 

• Requires catheter access via femoral or brachial routes (invasive)

• Allergy to iodinated contrast

• Need anesthesia support

• Complications: blood vessel damage, bleeding, and stroke