Diagnostic Imaging of the Brain and Spinal Cord Flashcards Preview

DPT 736 Neuroanatomy > Diagnostic Imaging of the Brain and Spinal Cord > Flashcards

Flashcards in Diagnostic Imaging of the Brain and Spinal Cord Deck (9)
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1

Radiographs

-primary uses: skull fractures, foreign bodies, tumors in skull, calcified brain lesions
-often used before MRI to make sure there are no metal objects
-fluoroscopy: real time moving radiographic images
-advantages: inexpensive, easy access
-disadvantages: produces tissue ionization (neutral atom/molecule acquires a positive or negative charge which can cause cell mutation or death)

2

Cerebral Angiography

-basics: contrast material injected into carotids or vertebral arteries, radiographs
-primary uses: detection of vessels abnormality (position, occlusion, malformation, aneurysm, fistula), interventional radiography
-advantages: inexpensive, easy access
-disadvantages: tissue ionization

3

Ultrasonography

-basics: ultrasound waves through fontanelles or craniotomy, computer analyzes the time and intensity of echoes from the waves
-primary uses: positioning and size of internal structures, bleeding, edema
-advantages: inexpensive, fast, easy, portable equipment
-disadvantages: limited by echoes from the surrounding skull, cannot penetrate bone

4

Computed Tomography CT

-AKA CAT Scan
-basics: scanning apparatus rotates a narrow radiograph beam around the head, absorption proportions are converted to gray scale by computer
-best at detecting acute bleeds
-black=low density structure
-white=high density structure
-density changes pathologically: hyperemia or freshly clotted hemorrhage appears more dense, edematous tissue appears less dense
-cross section=1.5mm to 1cm thickness
-contrast material can also be utilized
-primary uses: calcifications, edema, hydrocephalus, tumors, cysts, hemorrhages, aneurysms, vascular malformations
-advantages: cross-section, decent resolution, non-invasive, fast, and safe
-disadvantages: tissue ionization

5

MRI

-basics: strong external magnetic field causes hydrogen atoms in water to spin and emit energy; radiofrequency fields are used to alter this magnetic alignment
-T1 weighted: highlights fat deposits, dark=water (CSF, edema), calcium; bright=lipids, gadolinium
-T2 weighted: highlights water, dark=calcium, bone; bright=water (CSF, edema)
-signal is picked up and analyzed
-primary uses: suspected tumors, infrastructure, demyelination, infarcts
-advantages: high resolution (better than CT), image can be obtained in any plane, no radiation
-disadvantages: bone poorly imaged, costly, slow, ferromagnetic implants

6

Specialized MRI Scans

-FLAIR: suppresses liquid signals (CSF); type of T2, free water is now dark but edematous tissue is bright, useful for MS
-DTI: diffusion of water; maps fibers, useful for MS, concussion, traumatic brain injury, ischemic stroke (can detect within 5 minutes)

7

MRA

-A=angiogram
-visualization of arteries
-useful for stenosis and aneurysms

8

fMRI

-measures increase in blood flow that accompanies neural activity; active brain areas
-blood oxygen level dependent imaging technique (BOLD); measures regional deoxygenation of venous blood
-uses T2 MRI

9

PET

-positron emission tomography
-basics: radioisotopes are inhaled or injected; radioactively tagged molecules bind to specific neurons; pairs of gamma rays from decaying positrons are detected by scanner, reconstructed with CT
-primary uses: major research and clinical tool for blood flow, brain metabolism, and other chemical processes
-advantages: visualization of different types of neutrons
-disadvantages: lack of detailed resolution, positron-emitting nuclides decay rapidly