081210 enrs improving brachial plexus imaging neurography
DESCRIPTION
Title: Improving Brachial Plexus Imaging: Is Neurography the Answer?Authors: Johnson JM, Andrews T, Lemos D, Filippi, C.Purpose/Aim1. To briefly review the anatomy and common pathologies involving the brachial plexus.2. To discuss the current standard imaging of the brachial plexus and the associated limitations.3. To introduce neurographic sequences such as IR-EPI, DW and T2 TSE.4. To briefly discuss DTI applications in evaluation of the brachial plexus.BackgroundMagnetic resonance (MR) imaging is the dominant technique for imaging of the brachial plexus due to its multiplanar capabilities, high signal contrast between soft tissues and superior imaging resolution. Many MRI techniques have been developed to identify the components of the brachial plexus and the surrounding anatomy; however, inadequate or non-uniform fat suppression can degrade the image quality causing insufficient contrast between nerves and surrounding tissues. Issues with pulsation and flow related artifacts in the adjacent vessels could also limit standard MR techniques.Thorough anatomic depiction of the brachial plexus is important for localization of brachial plexus tumors, evaluation of brachial plexus injuries and assessment of inflammatory and infectious disease within the surrounding tissues that affect the brachial plexus. Additional indications for brachial plexus imaging include but are not limited to trauma, metastatic invasion, vascular malformation, degenerative changes and in the evaluation of peripheral neuropathies. Current imaging recommendations for the brachial plexus includes multiplanar T1, T2, STIR and T1 weighted imaging post gadolinium. Evaluation of the brachial plexus is often done in concern with routine imaging of the cervical spine. MR neurography has been described using multiple sequences that are similar in high conspicuity between the nerve roots of the brachial plexus and the surrounding structures and the additional ability to depict a long trajectory of the brachial plexus on reformatted MIP images. Neurography has been described using standard T2-weighted short tau inversion recovery (STIR) images with and without gadolinium administration, inversion recovery (IR) echo planar imaging (EPI) and diffusion weighted (DW) images. Each of these sequences features distinct advantages and limitations including sequence specific artifacts.Tractography, based on diffusion tensor imaging (DTI), has also been described in the spine and peripheral nervous system (PNS) including the brachial plexus. DTI functions by quantitatively assessing the diffusion of water in its microenvironment within tissues. DTI may provide clinically relevant information and may depict abnormalities beyond the resolution of conventional anatomic MR techniques. Mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) map values may reflect microstructural changes in some pathological conditions. Potential uses of DTI include monitoring the effects of radiation and/or chemotherapeutics on the brachial plexus.The ideal imaging sequence of the brachial plexus has not yet been identified. The current focus on new techniques revolves around neurography, which relies on high peripheral nerve conspicuity compared to surrounding tissue, and tractography, which has the potential to identify and quantify nerve abnormalities not visible on standard structural images. Future advances in brachial plexus and peripheral nerve imaging should open the door to better quantification and monitoring of disease of the PNS and may also be useful in surgical planning. References:Doi et al. Cervical nerve root avulsion in brachial plexus injuries: magnetic resonance imaging classification and comparison with myelography and computerized tomography myelography. J Neurosurg (2002) vol. 96 (3 Suppl) pp. 277-84Filler et al. MR neurography and muscle MR imaging for image diagnosis of disorders affecting the peripheral nerves and musculature. NTRANSCRIPT
Improving Brachial Plexus Imaging: Is
Neurography the Answer?
Jason JohnsonTrevor Andrews
Diego LemosChristopher Filippi
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Disclosures
• Nothing to disclose
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Why image the brachial
Plexus?
• Trauma• Primary neural tumors• Metastatic disease• Pancoast tumor• Post radiation injury• Radiculopathy• Bony abnormalities
such as cervical ribs• Degenerative diseases• Etc...
Versalius
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Traditional Brachial Plexus Imaging
• Pros
• Familiar
• High signal contrast
• No post-processing
• Cons
• Indirect nerve visualization
• 2D, not well amenable to MIP
• Issues with inadequate/non-uniform fat suppression
• Pulsation and flow related artifacts in the adjacent vessels
• Anatomy not well visualized in orthogonal planes
Multiplanar 2D sequences, typically T1, T2 and T2 STIR
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Brachial Plexus Neurography
• MR neurography - techniques to improve the identification and to generate tissue specific images of nerves.
• Two major types:
• T2-based (water) neurography
• Diffusion neurographyIR-EPI; Zhang, Et al.
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T2-based Neurography
• Neurography has been described using T2-weighted STIR, IR EPI and DW imaging.
• Each sequence has pros and cons.
Oblique Coronal IR-EPI MIP
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Coronal Oblique IR-EPI MIP7
T2 Neurography Limitations
• Slow
• Post Processing
• Motion susceptible
• Not actually imaging the nerve
• Poor SNR
Cor IR-EPI MIP8
Diffusion Neurography / Tractography
• Based on DWI/DTI.
• DTI provides information beyond the resolution of conventional anatomic MR techniques.
• Mean fractional anisotropy (FA) and apparent diffusion coefficient (ADC) map values may reflect microstructural changes in some pathological conditions.
• Potential uses of DTI include monitoring the effects of radiation and/or chemotherapeutics on the brachial plexus. DW MIP Slab
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Diffusion Neurography Limitations
• Slow
• Post Processing
• Motion susceptible
• Validation DWIBS MIPs
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Future of Brachial Plexus Imaging
• Ideal imaging sequence for brachial plexus not yet identified.
• Current research focus appears to revolve around neurography and tractography.
• Future advances in brachial plexus should improve monitoring disease of the PNS and may also be useful in surgical planning and medical decision making.
• Need collaboration with clinicians to assess and improve our imaging techniques.
Neurography likely to be integral part of brachial plexus imaging in the future.
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References• Doi et al. Cervical nerve root avulsion in brachial plexus injuries: magnetic resonance imaging classification and
comparison with myelography and computerized tomography myelography. J Neurosurg (2002) vol. 96 (3 Suppl) pp. 277-84
• Filler et al. MR neurography and muscle MR imaging for image diagnosis of disorders affecting the peripheral nerves and musculature. Neurol Clin (2004) vol. 22 (3) pp. 643-82, vi-vii
• Siqueira et al. Management of brachial plexus region tumours and tumour-like conditions: relevant diagnostic and surgical features in a consecutive series of eighteen patients. Acta Neurochir (2009) vol. 151 (9) pp. 1089-1098
• Smith et al. Magnetic resonance neurography in children with birth-related brachial plexus injury. Pediatr Radiol (2008) vol. 38 (2) pp. 159-63
• Takahara et al. Diffusion-weighted MR neurography of the brachial plexus: feasibility study. Radiology (2008) vol. 249 (2) pp. 653-60
• Vargas et al. Diffusion tensor imaging (DTI) and tractography of the brachial plexus: feasibility and initial experience in neoplastic conditions. Neuroradiology (2010) vol. 52 (3) pp. 237-245
• Viallon et al. High-resolution and functional magnetic resonance imaging of the brachial plexus using an isotropic 3D T2 STIR (Short Term Inversion Recovery) SPACE sequence and diffusion tensor imaging. Eur Radiol (2008) vol. 18 (5) pp. 1018-23
• Zhang et al. Segmented echo planar MR imaging of the brachial plexus with inversion recovery magnetization preparation at 3.0T. J Magn Reson Imaging (2008) vol. 28 (2) pp. 440-4
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