Clinical Diffusion Imaging

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Clinical Diffusion Imaging

• Lawrence N. Tanenbaum, M.D. FACR
• Seton Hall University - NJ Neuroscience Institute
  
• Edison Imaging JFK Medical Center
• www.drtmasters.com drt_at_drtmasters.com
• Edison, New Jersey

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Diffusion imaging

• detection random motion of water molecules
• translation of water over short distances
• DW pulse sequence
• apply large gradient pulse
• impart phase modulation
• wait
• spins diffuse away randomly
• apply reverse pulse
• rephase (abnormal) stationary spins (retain
  signal)
• (normal) moving spins remain dephased

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Diffusion Imaging
principles
Disease Causes Restricted Molecular Motion
Diffusion Gradients Sensitize to Motion
Increased Image Intensity
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Diffusion imagingdefinitions

• individual direction images
• images obtained with diffusion gradient applied
  in X, Y or Z direction
• corpus callosum
• allows diffusion of water molecules along
  orientation of fibers
• restricts diffusion of water perpendicular to
  fiber orientation

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Diffusion imagingisotropic diffusion image

• isotropic images
• combined, trace weighted images
• combination of individual direction images

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Diffusion imagingisotropic diffusion image

• advantages
• direction specific variations in diffusion
  eliminated
• increase conspicuity of subtle ischemia
• improved SNR

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TechniqueDW-EPI

• 8200 / min
• B 800 (ES, HS) 1200 (TS) s / mm2
• single shot SE EPI
• 5 mm / 0 mm
• 96 x 128, 1 nex
• 24 x 19 FOV
• 30 locations, 3 directions, 033
• trace weighted, B0 images generated by scanner

Mardi Gras NO 2001
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1000
B value
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TwinSpeed
B 1200 TE 69.9
B 2000 TE 79.1
B 3000 TE 87.6
B 4000 TE 94.4
B 6000 TE 105.2
B 5000 TE 100.2
B 7000 TE 109.7
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high SNR
DWI
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no ASSET
8 channel head coil 1.5 T
ASSET
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1200 B 3 Tesla
ASSET
no ASSET
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153
253
30 slc
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no ASSET
ASSET
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ASSET x 2
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PROPELLER FSE Periodically Rotated Overlapping
ParallEL lines with Enhanced Reconstruction
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DWI
Propeller FSE
ssEPI
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3T Diffusion imaging
Propeller FSE
ssEPI
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propeller
EPI
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Conventional DWI PROPELLER DWI
Images courtesy of Barrow Neurological Institute
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Diffusion imagingindications

• TIA and infarction
• demyelinating disease
• lesion characterization
• tractography

Steamboat 2001
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Diffusion imaging

• conventional MRI techniques limited in the
  detection of hyperacute stroke
• DW techniques sensitive within minutes of onset
  of infarction

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Diffusion imaginginfarction

• diffusion measurably slower in regions of
  ischemia when compared to normal brain
• cell swelling with restriction of motion between
  cells
• intracellular shift of water (cytotoxic edema)
• slower diffusion environment

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Diffusion imagingprinciples

• diffusion gradients sensitize MR Image to motion
  of extracellular water
• more motion darker image

Freely Diffusing Water Dark
Restricted Diffusion Bright
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B 1200
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Hyperacute infarction
35 minutes
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Hyperacute infarction
35 minutes
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1.5 T
0.2 T
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Line Scan DWI
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0.2T
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Technique0.2 T Profile LSDI

• SR 25 gradients
• 367 / min
• B 800 s / mm2 , S-I direction
• 7.5 mm / 0 mm
• 64 x 64, 1 nex, 2.02 kHz BW
• 26 FOV, fAP
• 18 locations, 741

Orlando 2000
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0.35T LSDI
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0.35T ssEPI
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0.35 T
DW EPI b value 1000 s/mm2 128 x 128 whole
brain in 20 seconds
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ssEPI
0.7T OpenSpeed
LSDI
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Open MR Diffusion Imaging Comparison of Line
Scan Diffusion Imaging at 0.2T With Diffusion
Weighted EPI at 1.5T in Patients With Recent
Infarction

• Tanenbaum LN, Borden N, Eshkar NE, Verro P, Sen S
• JFK Medical Center-New Jersey Neuroscience
  Institute
• Seton Hall School of Graduate Medical Education
• Edison, New Jersey

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Materials and Methods

• 21 consecutive patients with symptoms of recent
  infarction and positive findings on 1.5T DWEPI
  (GE Signa SR120) were evaluated on a clinical
  0.2T open system (GE Profile SR17) with LSDI.

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Overall comparisonFriedman test

• 0.2T LSDI (plt0.0001) and DWEPI 1.5T (plt0.0001)
  superior to 1.5 T FLAIR in the detection of
  recent infarction

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ResultsSensitivity 0.2T LSDI

• 22 recent infarcts seen on DWEPI at 1.5T
• Readers 1 and 2
• 20 definite infarcts (90.9)
• 1 possible infarct (4.5 )
• 1 no infarction (4.5 )

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1.5T FLAIR
1.5T DWEPI
0.2T DWLSI
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Diffusion imagingdefinitions

• diffusion weighted image
• randomly moving spins dephase
• see relatively LOW signal in normal tissues
• relatively static spins rephase
• see HIGH signal in areas of low diffusion
• ADC map
• isotropic image of apparent diffusion
  coefficient, trace image
• areas of low diffusion have LOW signal intensity

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e-b(ADC)
T2W e-b(ADC)
Trace weighted
ADC
Exponential ADC
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Diffusion imaginginfarction

• ADC decreases 30 - 60 with ischemia in
  experimental models.
• with permanent vascular occlusion ADC decreases
  highly correlate with areas of ultimate
  infarction volume.
• regional decreases in ADC can reverse after early
  reperfusion
• reversal accurately predicts size of infarction

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Lesion aging
T2
FLAIR
DW-EPI
Tampa 2001
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1.5 T
0.2 T
Steamboat 2001
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0.2T DWI
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Evaluation of Diffusion Weighted EPI and FLAIR
in Patients with Subacute Ischemic Symptoms

• LN Tanenbaum, BA Johnson, BP Drayer,
• JC Friel, P Verro and RG Hoffman
• New Jersey Neuroscience Institute
• Seton Hall School of Graduate Medical Education
• Edison, New Jersey

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Results Change in diagnosis with DW-EPI29
patients with clinical stroke

• no infarct
• possible infarct to additional infarct 4
  (7)
• definite infarct
• no infarct
• possible infarct to definite infarct 35
  (59)
• possible infarct
• definite infarct to no infarct
  5 (8)
• no change from FLAIR 15
  (25)

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venous infarction
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Diffusion imaginginfarction

• sensitive almost immediately
• appears to reflect clinical outcome
• distinguish between TIA and silent CVA
• differentiate acute and chronic infarction
• socioeconomic impact

Pusan 2000
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Lesion characterization
new onset seizures
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Case study Diagnosis Infarction
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Lesion characterization
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Lesion characterization
ADC map
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vasogenic edema
BBBB
DWI
ADC
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Diffusion imagingdemyelinating disease

• characterize and detect regions of active
  demyelination
• most / many contrast enhancing lesions show high
  signal on (moderate B) DW images
• some lesions with altered diffusion do not
  enhance at 0.1 mmol/kg
• enhance at 0.2 - 0.3 ?
• avoid (cost of) gadolinium?

Kuala Lumpur 2000
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1.5 T Excite 8 channel coil 1024 x 384 3 mm
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Trace
B0
ADC
Exponential
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hematoma
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prolonged seizure activity
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lymphoma
M. Maya MD
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lymphoma
M. Maya MD
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