Neurovascular Non Contrast-Enhanced MR Angiography at 3T
Neurovascular Non Contrast-Enhanced MR Angiography at 3T
MR angiography (MRA) has become essential in the treatment of neurovascular diseases,
 including ischemic stroke - the first cause of disability in occidental countries, vascular
 malformations such as aneurysms, arteriovenous fistulas and malformations, whose treatments
 are improving year after year.

 MRA is an alternative to digital substracted angiography (DSA), circumventing th use of
 endovascular catheterism, irradiation and injection of iodinated contrast agent.
 Contrast-Enhanced MRA (CE-MRA) with gadolinium injection is currently the reference standard
 for vascular MR exploration but still presents many limitations inherent to the injection of
 contrast medium. Hence, the synchronization of the acquisition with bolus contrast injection
 limits the improvement of spatial and temporal resolutions and requires an accurate
 synchronization of the acquisition with the arrival of the bolus.

 Moreover, the acquisition can be repeated as required as it does not require any contrast
 injection.

 Besides, the increase in nephrogenic systematic fibrosis clinical cases, which would be
 secondary to gadolinium chelates injection, in patients with chronic renal insufficiency has
 restricted the use of CE-MRA. More than 500 cases were described to date in the world.

 Its occurrence is currently estimated around 4 % for patients in terminal chronic renal
 insufficiency and its mortality around 30 %.

 According to the recommendations of AFSSAPS from August, 2007, two gadolinium contrast agent
 (Gadodiamide-OMNISCAN *, General Electric HealthCare and Gadopentetate Dimeglumine-MAGNEVIST
 *, Bayer HealthCare) are contraindicated if the glomerular filtration rate is lower than 30
 ml/mn.

 Non-contrast enhanced MR angiography (NCE MRA) techniques have been proposed to provide
 complete and non-invasive investigation of the vasculature, thus offering patients with
 chronic renal insufficiency, as well as pregnant or nursing women a surrogate with no side
 effects.

 Moreover, the use of high field (3T) MR imaging offers improved signal to noise ratio.
 Combined with the use of phased array coils and parallel imaging, new NCE MRA sequences can
 achieve juxta-millimeter isotropic spatial resolution and temporal resolution of about 50 ms
 close to those of cerebral DSA.

 These sequences allow a joint hemodynamical and morphological assessment of lesions, both at
 the cervical and cerebral levels, whether at diagnosis or during patient follow-up
The main objective is to evaluate the quality of the NCE images obtained in the exploration
 of neurovascular diseases, at the cervical and cerebral levels.

 Secondary objectives are:

 -  to compare the NCE MRA sequences with the CE MRA sequences used in the clinical routine.

 -  to evaluate the anatomic and hemodynamic changes observable with sequences in the
 follow-up of patients, particularly those treated with partial embolization or
 radiosurgery.

 By circumventing the limitation to short bolus duration synchronization, the new dynamic
 sequences have the potential to achieve higher temporal resolution without compromising
 spatial resolution. Arteries and arteriovenous shunts may be more precisely identified and,
 due to a better visibility of small vessels allow a more accurate dynamic analysis.

 Finally, the sequence being derived from arterial spin labeling, and differing from time of
 flight or phase contrast sequences, should allow for an exploration less dependent on the
 vascular geometry with better anatomical analysis. For example, the tendency to overestimate
 arterial stenoses could be reduced.

 The robustness of sequences allow the non-invasive monitoring of patients including it
 possible to monitor the hemodynamic changes after radiosurgery or embolization.
Inclusion Criteria:

 -  Men and women over 18 years

 -  Any adult patient known or clinically suspect to present a neurovascular disease
 (arterial stenosis ou arteriovenous malformations), the assessment of which requires
 an MRA or patient having an arteriovenous malformation for which treatment by
 embolization or radiosurgery is indicated multidisciplinary meeting and followed in
 the ordinary course of this treatment

 -  Patient able of accepting protocol information

 -  Patient who received information about the protocol and had not expressed its
 opposition to participate

 Exclusion Criteria:

 -  A contraindication to MRI, in particular pacemakers or implantable defibrillators,
 cochlear implants, neurosurgical clips, intra-orbital or brain metallic foreign
 bodies, endo prothesis since less than 4 weeks or osteosynthesis material since less
 than 6 weeks

 -  Contraindication to the injection of contrast agent: pregnancy, lactation, history of
 allergic reaction to contrast agent injection

 -  Hemodynamically unstability, acute respiratory failure, a precarious condition or a
 need for continuous monitoring incompatible with the constraints of MR imaging

 -  Patient with severe kidney with Glomerular Filtration rate < 30 ml/min

 -  Persons subject to major legal protection (safeguarding justice, guardianship,
 trusteeship), persons deprived of liberty