“MR Diffusion Tensor Imaging and Fiber Tracking in 5 Spinal Cord Astrocytomas.” American Journal of Neuroradiology 27, no. “Characterization and Limitations of Diffusion Tensor Imaging [r]
(1)Le Van Tan Cao Thien Tuong Cho Ray Hospital
24.8.2019
Technical DTI in spinal cord
Limitations and DTI technical adjustments
(2)2
Dxx Dxy Dxz
Dyx Dyy Dyz
Dzx Dzy Dzz
λ1 0 0 0 λ2 0 0 0 λ3
o DTI raised as an technical optimization of DWI that allow to assess the main diffusional direction within an anisotropic ti
e2 λ3
tissue
o For this aim, motion probing gradients are applied in several directions (at least 6 up to 128) to calculate the main diffusion vectors in a 3 x matrix.
Anisotropic diffusion :
λ1 >> λ2 ≈ λ3
e1λ1 o Thus, perpendicular vectors
(eigenvectors) are generated
which each one has a
diffusional value (eigenvalue) measured in mm2/s: λ1, λ2
andλ3. Isotropic
diffusion : λ1 ≈ λ2 ≈ λ3
On its longitudinal orientation, spinal cord demonstrated
demonstrated
anisotropic facilitated diffusion due to the inner cord structure (white matter funiculus) with a dominant
movement from head to foot
Thanks to these characteristics, spinal cord can be adequately evaluated using DTI.
(3)Eigenvalues for each voxel are calculated from the directional maps
= average of λ1 & λ2 & λ3
E i l t t ADC
Mean
Mean Diffusivity (MD)Diffusivity (MD)
Equivalent to ADC
= principal axis λ1
Represents water diffusivity parallel to axons
Also referred to as axial diffusivity
= average of λ2 & λ3
Represents water diffusivity perpendicular to axons
Longitudinal
Longitudinal diffusivity (LD) diffusivity (LD)
Radial
Radial diffusivity (RD) diffusivity (RD)
= ranges from 0-1 (isotropic to completely anisotropic)
Evaluatesglobal anisotropy
WM is bright (more anisotropic)
Decreases when LD↓ or when RD↑
Fractional
Fractional Anisotropy Anisotropy (FA)(FA)
Anisotropic diffusion along white matter tracts
Interstitial Edema
Increases in spacing between p g
cell membranes increases the mean diffusivity (MD)
↑ Trace signal
↑ ADC
A.M. Rutman, D. Peterson, W. Cohen, M. Mossa‐Basha
(4)4 Primary injury to myelin
Fewer membranes to hinder perpendicular water motion perpendicular water motion ↑ MD
↑ RD
↓ FA
Primary injury to axons
Disruption of parallel Disruption of parallel
(longitudinal) water motion along WM fiber tracts
↑ MD
↓ LD
↓ FA
A.M. Rutman, D. Peterson, W. Cohen, M. Mossa‐Basha University of Washington Department of Radiology
AKA Fiber Direction Map or Diffusion texture map Voxels are assigned colors based on anisotropy and direction
– Red = Left - Right
(5)MD TRACE FA TRACTOGRAPHY
Khoa CĐHA ‐ BVCR
DTI Parameter 3T Skyra
TR/TE 2000/65ms
0
Flip angle 900
FOV 280 mm
Thickness 3 mm
Direction 20
B values 0, 1000
(6)6
Multiple interfaces between bone, epidural fat (chemical shift) and CSF: increase the readout (chemical shift) and CSF: increase the readout artifact.
Pulsation artifacts from aorta, heart or CSF: induce phase errors.
The spinal cord has a small diameter and is located in a deep position: It is difficult to achieve a full SNR with high spatial resolution
If Single-Shot EPI is used, add parallel imaging to reduce susceptibility artifacts and scan time
Use Multi-Shot EPI if available.
Use cardiac triggering to reduce pulsation artifacts.
(7)S i l C d I f t Spinal Cord Infarct Spinal Cord Trauma Spinal Cord Tumors
As with brain imaging, DWI is becoming an important tool for detection of cord infarct
DWI is more sensitive and specific than conventional MRI abnormalities
Diffusion restriction appears earlier than T2 findings on conventional MRI (high Trace signal, low ADC)
h t 3h ft t t lth h t ti th h ld i
as short as 3h after symptom onset, although exact time threshold remains unclear
Enables the confident diagnosis of infarct
In chronic infarct, ADC may become increased as encephalomalacia develops
A.M. Rutman, D. Peterson, W. Cohen, M. Mossa‐Basha
(8)8 MRI Conventional MRI
is used to image cord compression and injury compression and injury from extramedullary hemorrhage or
disc/fracture fragment retropulsion
DTI can be sensitive to
h t t
T2 Trace ADC FA
changes not apparent on conventional MRI
T2 Trace ADC FA
Khoa CĐHA ‐ BVCR
Tractography can delineate the pattern of fiber disruption Can help predict outcome by evaluating continuity of fibers through a traumatic lesion
T2 Tractography
S. RAJASEKARAN, R. M. KANNA, A. P. SHETTY J Bone Joint Surg Br 2012;94‐B:1024–31
(9)A t t l ti ith DTI
Tractography may reveal fiber displacement in ependymomas and fiber infiltration in astrocytomas.
Ependymoma evaluation with DTI AstrocytomaLandi A, World J Clin Cases 2016evaluation with DTI Ducreux D, AJNR. 2006
Lasbleiz J, J Radiol 2006
DTI tractography can delineate WM tracts in delineate WM tracts in relation to tumors and other mass lesions, and can help guide surgical treatment. DTI can predict resectability pre-operatively, DTI may be
t ti l t l f t t t
T2 Trace ADC Tractography
a potential tool for treatment monitoring specially for detection of recurrence
T2 Trace ADC T2
(10)10 DTI is a non-invasive technique that allows to assess
microstructure of spinal cord structures and to perform spinal cord 3D tractography reconstructions.
DTI may be a potential tool for early detection of
abnormalities in the spinal cord, a complementary tool to conventional MRI in spine cord lesions evaluation
DTI and tractography can delineate WM tracts relative to the tumor and aid in tumor mapping and surgical planning Can help predict outcome by evaluating continuity of fibers through a traumatic lesion.
1 Vargas, Maria Isabel, Jacqueline Delavelle, Helmi Jlassi, Bénédict Rilliet, Magalie Viallon, Christoph D Becker, and Karl-OlofLövblad “Clinical Applications of Diffusion Tensor Tractography of the Spinal Cord.” Neuroradiology 50, no (October 2, 2007): 25–29
2 Thurnher, Majda M., and Roland Bammer “Diffusion-Weighted MR Imaging (DWI) in Spinal Cord Ischemia.” Neuroradiology 48, no 11 (November 2006): 795–801
3 Weidauer, Stefan, Michael Nichtweiss, Heinrich Lanfermann, and Friedhelm E Zanella “Spinal Cord Infarction: MR Imaging and Clinical Features in 16 Cases ” Neuroradiology 44 no 10 (October 2002): 851–57
MR Imaging and Clinical Features in 16 Cases Neuroradiology 44, no 10 (October 2002): 851 57
4 Alblas, Cornelis L., Willem H Bouvy, Geert J Lycklama Nijeholt, and Jelis Boiten “Acute Spinal-Cord Ischemia: Evolution of MRI Findings.” Journal of Clinical Neurology (Seoul, Korea) 8, no (September 2012): 218–23 Shanmuganathan, K., R P Gullapalli, J Zhuo, and S E Mirvis “Diffusion Tensor MR Imaging in Cervical Spine
Trauma.” American Journal of Neuroradiology 29, no (April 1, 2008): 655–59
6 Chang, Yongmin, Tae-Du Jung, Dong Soo Yoo, and Jung Keun Hyun “Diffusion Tensor Imaging and Fiber Tractography of Patients with Cervical Spinal Cord Injury.” Journal of Neurotrauma 27, no 11 (September 7, 2010): 2033–40
7 Kim, J, Moritani T “MRI diagnosis of spinal cord lesions with emphasis on diffusion-weighted imaging: characteristic findings, differential diagnoses and imaging pitfalls.” Electronic Presentation Online System, European Congress of Radiology 2012 Poster No.: C-1924 doi: 10.1594/ecr2012/C-1924
8 Setzer, Matthias, Ryan D Murtagh, F Reed Murtagh, Mohammed Eleraky, Surbhi Jain, Gerhard Marquardt, Volker Seifert and Frank D Vrionis “Diffusion Tensor Imaging Tractography in Patients with Intramedullary Tumors: Seifert, and Frank D Vrionis Diffusion Tensor Imaging Tractography in Patients with Intramedullary Tumors: Comparison with Intraoperative Findings and Value for Prediction of Tumor Resectability.” Journal of Neurosurgery: Spine 13, no (September 1, 2010): 371–80
9 Ducreux, D., J.-F Lepeintre, P Fillard, C Loureiro, M Tadié, and P Lasjaunias “MR Diffusion Tensor Imaging and Fiber Tracking in Spinal Cord Astrocytomas.” American Journal of Neuroradiology 27, no (January 1, 2006): 214–16
10 Vedantam, Aditya, Michael B Jirjis, Brian D Schmit, Marjorie C Wang, John L Ulmer, and Shekar N Kurpad “Characterization and Limitations of Diffusion Tensor Imaging Metrics in the Cervical Spinal Cord in Neurologically Intact Subjects.” Journal of Magnetic Resonance Imaging: JMRI 38, no (October 2013): 861–67
(11) hinhanhykhoa.com