Neuroradiology

From IKE

Contents 1 Brain imaging 1.1 Plain X-Rays 1.2 Pneumoencephalogray (PEG) 1.3 Computerized tomography (CT) 1.3.1 Advantages 1.3.2 Disadvantages 1.4 MRI 1.4.1 Basics 1.4.2 Advantages 1.4.3 Disadvantages 1.5 Functional MRI (fMRI) 1.6 Perfusion imaging 1.7 Vascular imaging 2 Spinal imaging 2.1 Plain films 2.2 Myelography 2.3 Nuclear medicine bone scan 2.4 CT 2.5 MRI

Brain imaging

Plain X-Rays

• skull films are of limited value
• will show fractures, but other imaging is usually required in trauma
• rarely done for neuroimaging

Pneumoencephalogray (PEG)

• historical interest only
• Combined with cerebral angiography and plain X-Rays, this was the only radiographic investigation of the CNS available until the early 1970s

Computerized tomography (CT)

Advantages

• fast
• relatively inexpensive
• accessible
• good for common lesions such as hemorrhage, tumours, degenerative spinal lesions

Disadvantages

• Radiation dosage
• limited field of view
• artifact from bone (especially in posterior fossa and brainstem)
• may be insensitive to some conditions such as MS and early strokes

MRI

Basics

• based on magnetic properties of hydrogen
• Very sensitive to changes in water content of tissues
• T1 and T2 relaxation determines signal from tissue and appearance of images

Advantages

• More sensitive than CT to many conditions (MS, early strokes) due to better tissue contrast resolution
• Multiplanar imaging is easy
• no artifact from bone (particularly in the posterior fossa)

Disadvantages

• Slower
• More expensive
• Less accessible, with long waiting lists (up to 1 year!)
• Claustrophobia, pacemakers, and old aneurysm clips are contraindicated

Functional MRI (fMRI)

• research technique that is now moving into clinical application
• Allows for the localization of brain function

Perfusion imaging

• Can use either CT or MR to measure cerebral blood flow by tracking a bolus of IV contrast through cerebral circulation with rapid, sequential scans
• Can be useful in acute stroke, to select patients for thrombolysis
• Helps identify salvageable brain
• Can aid in ascertaining prognosis

Vascular imaging

• DSA (Digital subtraction angiography) - very invasive and has relatively high risk
• MR Angiography - non-invasive, and relatively low risk; good survey tool
• CT Angiography - uses IV contrast; also a good screening technique
• Ultrasound - non-invasive, anatomic or physiologic information; excellent screening technique for carotid bifurcation atherosclerotic disease

Spinal imaging

Plain films

• gives normal anatomy of cervical and thoracic spine
• Excellent bone detail, but no information on spinal cord or nerve roots

Myelography

• intrathecal water-soluble contrast material injected vial lumbar or C1-2 puncture to outline cord and nerve roots
• Invasive, with side effects
• Excellent visualization of nerve roots

Nuclear medicine bone scan

• low resolution images
• high sensitivity to any process involving bone turnover
• Very non-specific

CT

• Images the lumbar spine better than the cervical spine
• Throws off lots of radiation, and doesn't show spinal cord well

MRI

• best survey exam
• Wide field of view
• best for soft tissues
• not bad for bone
• multiplanar