Introduction to Neuroimaging - PowerPoint PPT Presentation

Loading...

PPT – Introduction to Neuroimaging PowerPoint presentation | free to view - id: 10b482-ZDc1Z



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Introduction to Neuroimaging

Description:

Introduction to Neuroimaging – PowerPoint PPT presentation

Number of Views:1415
Avg rating:3.0/5.0
Slides: 70
Provided by: aaron123
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Introduction to Neuroimaging


1
Introduction to Neuroimaging
Aaron S. Field, MD, PhD Assistant Professor of
Radiology Neuroradiology Section University of
WisconsinMadison
Updated 7/17/07
2
Neuroimaging Modalities
  • Magnetic Resonance (MR)
  • MR Angiography/Venography (MRA/MRV)
  • Diffusion and Diffusion Tensor MR
  • Perfusion MR
  • MR Spectroscopy (MRS)
  • Functional MR (fMRI)
  • Nuclear Medicine
  • Single Photon Emission Computed Tomography
    (SPECT)
  • Positron Emission Tomography (PET)
  • Radiography (X-Ray)
  • Fluoroscopy (guided procedures)
  • Angiography
  • Diagnostic
  • Interventional
  • Myelography
  • Ultrasound (US)
  • Gray-Scale
  • Color Doppler
  • Computed Tomography (CT)
  • CT Angiography (CTA)
  • Perfusion CT
  • CT Myelography

Duplex
3
Radiography (X-Ray)
4
Radiography (X-Ray)
  • Primarily used for spine
  • Trauma
  • Degenerative Dz
  • Post-op

5
Fluoroscopy (Real-Time X-Ray)
  • Fluoro-guided procedures
  • Angiography
  • Myelography

6
Fluoroscopy (Real-Time X-Ray)
7
Fluoroscopy (Real-Time X-Ray)
Digital Subtraction Angiography
8
Fluoroscopy (Real-Time X-Ray)
Digital Subtraction Angiography
9
Digital Subtraction Angiography
Indications
  • Aneurysms, vascular malformations and fistulae
  • Vessel stenosis, thrombosis, dissection,
    pseudoaneurysm
  • Stenting, embolization, thrombolysis (mechanical
    and pharmacologic)
  • Ability to intervene
  • Time-resolved blood flow dynamics (arterial,
    capillary, venous phases)
  • High spatial and temporal resolution
  • Invasive, risk of vascular injury and stroke
  • Iodinated contrast and ionizing radiation

Advantages
Disadvantages
10
Fluoroscopy (Real-Time X-Ray)
Myelography
Lumbar or cervical puncture Inject contrast
intrathecally with fluoroscopic
guidance Follow-up with post-myelo CT (CT
myelogram)
11
Myelography
Indications
  • Spinal stenosis, nerve root compression
  • CSF leak
  • MRI inadequate or contraindicated
  • Defines extent of subarachnoid space, identifies
    spinal block
  • Invasive, complications (CSF leak, headache,
    contrast reaction, etc.)
  • Ionizing radiation and iodinated contrast
  • Limited coverage

Advantages
Disadvantages
12
Ultrasound
13
Ultrasound
Indications
  • Carotid stenosis
  • Vasospasm - Transcranial Doppler (TCD)
  • Infant brain imaging (open fontanelle acoustic
    window)
  • Noninvasive, well-tolerated, readily available,
    low cost
  • Quantitates blood velocity
  • Reveals morphology (stability) of atheromatous
    plaques
  • Severe stenosis may appear occluded
  • Limited coverage, difficult through air/bone
  • Operator dependent

Advantages
Disadvantages
14
Ultrasound Gray Scale
Gray-scale image of carotid artery
15
Ultrasound Gray Scale
Plaque in ICA
Gray-scale image of carotid artery
16
Ultrasound - Color Doppler
Peak Systolic Velocity (cm/sec) ICA Stenosis
( diameter) 125 225 50 70 225
350 70 90 gt350 gt90
17
Computed Tomography (CT)
18
Computed Tomography
A CT image is a pixel-by-pixel map of X-ray beam
attenuation (essentially density) in
Hounsfield
Units (HU)
HUwater 0
Bright hyper-attenuating or hyper-dense
19
Computed Tomography
Typical HU Values
Air 1000 Fat 100 to 40 Water 0 Other
fluids (e.g. CSF) 020 White matter 2035 Gray
matter 3040 Blood clot 5575 Calcification gt1
50 Bone 1000 Metallic foreign body gt1000
Brain
20
Computed Tomography
Attenuation High or Low?
  • High
  • Blood, calcium
  • Less fluid / more tissue
  • Low
  • Fat, air
  • More fluid / less tissue

Air 1000 Fat 100 to 40 Water 0 Other
fluids 020 White matter 2035 Gray
matter 3040 Blood clot 5575 Calcification gt1
50 Bone 1000 Metallic foreign body gt1000
21
(No Transcript)
22
Computed Tomography
Soft Tissue Window Bone Window
23
Computed Tomography
24
Computed Tomography
Scan axially
stack and re-slice in any plane
2D Recons
25
CT Indications
  • Skull and skull base, vertebrae
  • (trauma, bone lesions)
  • Ventricles
  • (hydrocephalus, shunt placement)
  • Intracranial masses, mass effects
  • (headache, N/V, visual symptoms, etc.)
  • Hemorrhage, ischemia
  • (stroke, mental status change)
  • Calcification
  • (lesion characterization)

26
Skull and skull base, vertebrae
Fractures
27
Skull and skull base, vertebrae
Multiple Myeloma
Osteoma
28
Ventricles
Hydrocephalus
29
Intracranial masses, mass effects
Solid mass
Cystic mass
30
Intracranial masses, mass effects
L hemisphere swelling
Generalized swelling
31
Acute Hemorrhage
Intraparenchymal Subarachnoid
Subdural Epidural
32
Acute Ischemia
Loss of gray-white distinction and swelling in
known arterial territory
33
Calcification
Hyperparathyroidism
34
CT Angiography
  • Rapid IV contrast bolus
  • Dynamic scanning during arterial phase
  • Advanced 2D and 3D Reconstructions
  • 2D multi-planar (sagittal, coronal)
  • Volumerendered 3D recons

35
CT Angiography - Head
36
CT Angiography - Head
Circle of Willis
Vascular Malformations
Aneurysms
37
CT Angiography - Neck
Carotid bifurcations
Vertebral arteries
Aortic arch
38
CT Angiography 3D Volume Rendering
39
CT Angiography - Indications
  • Atherosclerosis
  • Thromboembolism
  • Vascular dissection
  • Aneurysms
  • Vascular malformations
  • Penetrating trauma

40
CT Perfusion
41
Hemodynamic Parameters Derived From
Concentration-Time Curves
Bolus arrival
Vein
Artery
42
Hemodynamic Parameter Maps
Transit Time (sec)
Blood Flow (mL/min/g)
Blood Volume (mL/g)
43
CT Myelography
  • Spinal CT immediately following conventional
    myelogram
  • Cross-sectional view of spinal canal along with
    spinal cord and nerve roots
  • Assess spinal stenosis/nerve root compression
    (e.g. disc
    herniation, vertebral fracture, neoplasm)

44
CT Myelography
45
CT Myelography
46
Magnetic Resonance (MR)
Hydrogen proton in water or fat
MRI
47
Magnetic Resonance Imaging
48
RF Radio Frequency energy
Received signal
magnetic field
49
MRI Safety The Magnet is Always On!
50
Magnetic Resonance Safety
MRI Safety Test Will it Move? Torque? Get
hot? Pass a current? Malfunction? Become a
projectile? Get stuck in scanner?
  • Typically safe
  • Orthopedic hardware
  • Surgical clips, staples, sutures (older devices
    must be checked!)
  • Intravascular stents/filters
  • Typically unsafe
  • Cardiac pacemakers (and other
    electrical devices)
  • Some older aneurysm clips
  • Metal fragments in orbit (1 case
    report)
  • Oxygen tanks, carts, chairs, stools, IV poles,
    gurneys, etc.
  • Some cosmetics, tattoos, jewelry, hairpins, etc.
  • Pager, watch, wallet, ID badge, pen, keys,
    pocketknife, etc.

This is an incomplete list and there are many
exceptions to every rule When in doubt,
check it out!
51
Magnetic Resonance
Excited protons relax back to equilibrium

T2
T1
Relaxation rates depend on local molecular
environment
52
Magnetic Resonance
53
Magnetic Resonance
T2
T1
Arachnoid Cyst
54
Magnetic Resonance
T2 T2 w/ fat suppression
55
Magnetic Resonance
T2 T2 w/ fat suppression
56
Magnetic Resonance
T2 T2 w/ water
suppression
(T2-FLAIR)
57
Magnetic Resonance
Accentuating blood/calcium
blooming
T2
T2
58
Diffusion MR Imaging
NORMAL
CYTOTOXIC EDEMA (Acute Ischemia)
Diffusion ? MR Signal ?
59
Magnetic Resonance
Imaging Diffusion
DWI
Highly sensitive to acute ischemia within a
few hours! No other imaging is more sensitive to
acute ischemia although perfusion imaging
reveals hypoperfused tissue at risk for
ischemia
Acute left MCA infarction
60
Magnetic Resonance Angiography
Axial source images
reformatted to maximum intensity projections
(MIP) Multiple projections allow 3D-like display
No need for IV contrast!
61
Time-Resolved MRA (TRICKS)
IV contrast bolus reveals temporal dynamics
62
Magnetic Resonance Angiography with Perfusion MR
MRA Perfusion MR
63
Magnetic Resonance
Tissue contrast in MR may be based on
  • Proton density
  • Water/fat/protein content
  • Metabolic compounds (MR Spectroscopy)
  • e.g. Choline, creatine, N-acetylaspartate,
    lactate
  • Magnetic properties of specific molecules
  • e.g. Hemoglobin
  • Diffusion of water
  • Perfusion (capillary blood flow)
  • Bulk flow (large vessels, CSF)

64
IV Contrast in Neuroimaging
  • CT Iodine-based
  • Iodine is highly attenuating of X-ray beam
    (bright on CT)
  • MRI Gadolinium-based
  • Gadolinium is a paramagnetic metal that hastens
    T1 relaxation of nearby water protons (bright on
    T1-weighted images)
  • Tissue that gets brighter with IV contrast is
    said to enhance (Brightness, in and of itself,
    is not enhancement!)
  • Enhancement reflects the vascularity of tissue,
    but
  • The blood-brain barrier keeps IV contrast out of
    the brain!
  • Enhancement implies BBB is absent or
    dysfunctional
  • Remember Some brain anatomy lives outside the
    BBB

65
IV Contrast in Neuroimaging
Enhancement
  • Vessels
  • Meninges
  • pachy dura
  • lepto pia-arachnoid
  • Circumventricular organs (structures outside BBB)
  • Pineal gland
  • Pituitary gland
  • Choroid plexus
  • Absent/leaky BBB
  • Some tumors
  • Inflammation
  • Infarction

66
Enhancement
T1
T1C
Hemorrhagic melanoma metastasis
67
IV Contrast Is it Indicated?
Typically not
Typically yes
  • Trauma
  • R/O hemorrhage
  • Hydrocephalus
  • Dementia
  • Epilepsy
  • Neoplasm
  • Infection
  • Vascular disease
  • Inflammatory disease

Always best to provide detailed
indication! Radiologist will protocol exam
accordingly
68
MR vs. CT
CT
MR
  • Advantages
  • Simpler, cheaper, more accessible
  • Tolerated by claustrophobics
  • No absolute contraindications
  • Fewer pitfalls in interpretation
  • Better than MR for bone detail
  • Disadvantages
  • Ionizing radiation
  • IV contrast complications
  • Need recons for multi-planar
  • Limited range of tissue contrasts
  • Advantages
  • Much broader palette of tissue contrasts
    (including functional and molecular) yields
    greater anatomic detail and more comprehensive
    analysis of pathology
  • No ionizing radiation
  • Direct multi-planar imaging
  • IV contrast better tolerated (in most pts.)
  • Disadvantages
  • Higher cost, limited access
  • Difficult for unstable patients
  • Several absolute contraindications (cardiac
    pacer, some aneurysm clips, etc.)
  • Claustrophobics may need sedation
  • Image interpretation more challenging
  • Lacks bone detail

69
Introduction to Neuroimaging
Aaron S. Field, MD, PhD Assistant Professor of
Radiology Neuroradiology Section University of
WisconsinMadison
About PowerShow.com