iea - i workshop em pressão intracraniana - parte 6

Simpósio PICMI - Outubro/2011

Simpósio PICMI - Outubro/2011Simpósio PICMI - Outubro/2011

A Ressonância Magnética como um método de aferição da PIC

Alberto Tannús

CIERMag – IFSC - USP


Major items of this talk:

Basic ideas for verifying ICP; MRI methodologies; Existing facility


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)


From Geeraerts T et al., Crit Care. 2008;12(5):R114


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 Neurochirurgica Supplementum, 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)


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.)


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.


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);


CITESC (Ciencia, Inovação e Tecnologia em Saúde, 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);


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!!


Tune & match circuit

“Double crosses” (outperforms) the equivalent Birdcage structure

Our best approach: Double Crossed Saddle


Latest developed probes:Receiving coils for rodents – surface coils

C

C C

CM

CT

RFout

Tune & match circuit on reception


Rodents brain surface coils*:

* Tested also as transmit/receive

Anesthetics mask

Motion restriction


Results: Double Crossed Saddle

Actually a 20/31 system for now


Thank you!

iea - i workshop em pressão intracraniana - parte 6

Education

increased icp

raised icp

mr imaging

new methodologies

perfusion methods

basic ideas

mrimrs methodology mri

studies studies