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MRI as a Method for Assessing Intracranial Pressure: Advances and Methodologies

This symposium presentation discusses the use of MRI as a non-invasive tool for measuring intracranial pressure (ICP). Key topics include foundational concepts for verifying ICP, advanced MRI methodologies, and changes in brain morphology associated with increased ICP, such as enlarged ventricles and optic nerve sheath distention. The talk covers various imaging techniques, from conventional to dynamic MRI, and explores correlations between cerebral blood flow and ICP. The importance of specialized facilities for advanced MRI research is also highlighted.

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MRI as a Method for Assessing Intracranial Pressure: Advances and Methodologies

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Presentation Transcript

  1. Simpósio PICMI - Outubro/2011 A Ressonância Magnética como um método de aferição da PIC Alberto Tannús CIERMag – IFSC - USP

  2. Major items of this talk: • Basic ideas for verifying ICP; • MRI methodologies; • Existing facility

  3. Changes in morphology: •  An increased ICP would show as enlarged ventricles, which can be seen in the transverse sectioning; • Optic Nerve Sheath Diameter (ONSD) – US -> MRI: Increased ICP is transmitted through the cerebrospinal fluid surrounding the optic nerve, causing distention of the optic nerve sheath diameter (http://noninvasiveicp.com/node/47) • retro-bulbar optic nerve sheath diameter (ONSD) above 5.82mm predicts raised ICP in 90% of cases (http://www.sciencedaily.com/releases/2008/09/080910210531.htm)

  4. From Geeraerts Tet al., Crit Care. 2008;12(5):R114 

  5. Changes in morphology continued: •  Measurement of intracranial compliance (ICC) with dynamic magnetic resonance imaging (MRI) of blood and cerebrospinal fluid (CSF) flows to and from the brain (research of N J Alperin from University of Illinois at Chicago); (Alperin et al Acta NeurochirurgicaSupplementum, 2005, Volume 95, Part 4, 191-193) • MR imaging of the optic nerves and pituitary gland provided important clues for the diagnosis of idiopathic intracranial hypertension and showed a return to normal appearance after normalization of CSF pressure (Suzuki et al, AJNR Am J Neuroradiol 22:196–199, January 2001)

  6. Flow and perfusion methods: •  Cerebral Blood Flow and ICP: results demonstrated that CBF values span over a much narrower range as compared with ICP. It means no correlation, due to self regulatory mechanism of TCBF. (Alperin et al, ib.) • Gives rise to correlations of blood flow (velocity and profile) with TCBF; (one of our proposals.)

  7. Major items of this talk: • Basic ideas for verifying ICP; • MRI methodologies; • Existing facility

  8. Morphology: • Conventional imaging methods – RARE, TSE, IRSE etc.; • Fast Imaging methods – EPI; • Short TE methods – UTE, ZTE etc.; • Flow and diffusion: • Diffusion weighted imaging – DWI; • Image phase map for flow measurements; • Imaging methods for transverse velocity profile; • Spin Labeling for CBF and TCBF estimates – ASL, CASL, PASL.

  9. Major items of this talk: • Basic ideas for verifying ICP; • MRI methodologies; • Existing facility

  10. CIERMag (Centro de Imagens e Espectroscopia in vivo por RM): • One 2.0 Tesla 31 cm horizontal magnet running with a Bruker electronics (Avance III/ Paravision 5.1); • Capable to perform ANY MRI/MRS methodology; • MRI and MRS Probes for small rodents and small primates (up to 450g), and for different nuclear species on demand; • Pending conclusion of special facility to accommodate a 4.7 Tesla 33 cm bore horizontal magnet; • Pending conclusion of the fully Digital MRI/MRS Spectrometer to operate this and other systems (ToRM 15 Project);

  11. CITESC (Ciencia, Inovação e TecnologiaemSaúde, unidade de São Carlos): • One 1.5 Tesla whole body scanner with patient/ volunteer agenda (clinical research); • One 1.5 Tesla (or one 0.35 Tesla) whole body scanner for technological development (may be used for clinical experiments on new methodologies involving hardware development);

  12. Probes: why focus on them? • Diversity of anatomies – no single probe for all studies; • Studies at the limit of sensitivity; • Large number of nuclei of interest; • Methodologies requiring dedicated hardware (e. g. split transmit coil ASL – avoid MT); • Flexibility of studies – would you touch a US$35k probe to configure it for a new experiment? • Better build your own!!

  13. Our best approach: Double Crossed Saddle Tune & match circuit “Double crosses” (outperforms) the equivalent Birdcage structure

  14. Latest developed probes:Receiving coils for rodents – surface coils C CM C C CT RFout Tune & match circuit on reception

  15. Rodents brain surface coils*: Anesthetics mask Motion restriction * Tested also as transmit/receive

  16. Results: Double Crossed Saddle Actually a 20/31 system for now

  17. Thank you!

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