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The ultra-high-field MRI symposium
Early problems of = ultra-high=20 field Magnetic Resonance Imaging (MRI) have been overcome by successful=20 development of adequate hardware. In consequence big efforts have been = achieved=20 in structural imaging, as well in functional imaging. Basic scientists = and=20 physicians who work in ultra-high-field MRI in Europe and the USA, met = at the=20 Berlin Ultra-high-field Facility (BUFF), in the Max Dehlbr=C3=BCck = Centre (MDC),=20 Germany, to discuss their findings at the 1st annual symposium.
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According to the event organiser, Professor Thoralf Niendorf, head of = the=20 facility, the main goal of the symposium was to introduce the BUFF to = the=20 international UHF-MRI community and to initiate an annual gathering to = provide a=20 regular overview of state-of-the-art in UHF MRI, discussions on future=20 directions, foster joint explorations and initiate international=20 collaboration.
Giving an insight into work at the facility (launched in January = 2009, and=20 headed by Prof. Niendorf in August that year), he explained that it = possesses a=20 3-T, 7-T whole-body human MR scanner and 9.4-T animal MR-scanner. = Different=20 research teams, which include basic scientists, mathematicians, = engineers and=20 clinical scientists, focus on the development of UHF MR applications in=20 cardiovascular, neurological and cancer research.
Working with the 7-T whole body MRI scanner includes development of=20 appropriate hardware. =E2=80=98We received a very well designed MR = system. Due to the=20 early stage of the explorations there was limited extra ancillary = hardware=20 available -- RF-coils suitable for cardiac and body imaging, for = example. That=E2=80=99s=20 why we set up an environment where we build MR equipment and improve = existing=20 hardware,=E2=80=99 he explained. Several ultra-high-field centres = already have developed=20 prototypes of novel MR-coil hardware and are now in a process of having = this=20 hardware certified for clinical applications.
Barriers against 7-T going clinical
Dr Franz Schmitt, Director of Ultra-high-field MRI and Collaboration=20 Management in the Siemens AG Healthcare division, the first company = delivering a=20 7-T to Massachusetts General Hospital in 2001, lectured on the remaining = barriers for the 7-T to go clinical.
There are still regulatory obstacles. The 7-T is still neither CE = certified=20 nor other governing bodies. However, according to Dr Schmitt, in 2003 = the FDA=20 agreed to allow UHF MRI up to 7-T, but this is blocked by the regulatory = of=20 International Electrotechnical Commission (IEC). The International = Commission on=20 Non-Ionising Radiation Protection (ICNIRP), a non-governmental = organisation=20 officially recognised by the World Health Organization (WHO), changed = its=20 perspective in September 2009 and classified in a guideline the use of = up to 8-T=20 as safe in a controlled mode.
A directive of the European Parliament and of the European Council=20 (2004/40/EC), which is supposed to provide measures to protect workers = from=20 risks related to electromagnetic fields (EMF) requires special attention = for the=20 daily, routine use of UHF MRI in a clinical environment. In this = context, the=20 Alliance for MRI was formed in 2007. This body aims to safeguard the = future use=20 of MRI through an EU-wide exemption for use in medical and related = research from=20 any exposure limit values set in the Physical Agents 2004/40/EC (EMF) = Directive.=20 (Details on the Alliance for MRI are published in our Online Edition=20 www.european-hospital.com 01/06/2010) .
Another barrier against 7-T MRI going clinical is currently = associated with=20 the large, passively shielded magnets and their overall costs of = ownership.=20 Soon, this obstacle will be overcome due to the introduction of actively = shielded magnets, Dr Schmitt pointed out. In contrast to the passively = shielded=20 magnet, which requires tons of iron for shielding, the actively shielded = magnet=20 makes extra iron shielding almost obsolete. For example, a third of the = total=20 cost of the 7-T MRI at BUFF was spent on the iron shielding cage that = surrounds=20 the magnet.
Ultra-high-field MRI of the brain
During the meeting, UHF MRI pioneer Professor Lawrence L Wald, member = of the=20 A Martinos Centre for Biomedical Imaging in Charlestown, Massachusetts, = USA, and=20 associate Biophysicist at Massachusetts General Hospital, presented his = results=20 on depth-resolved laminar analyses of resting-state fluctuation = amplitude in=20 high-resolution 7-T in functional MRI (fMRI). In the past, high spatial=20 resolution MRI was feasible for structural or anatomical imaging only. = Achieving=20 a submillimetre spatial resolution in brain fMRI has been elusive as = yet, due to=20 the competing constraints of temporal resolution of 2-3s and image = quality.=20 Using the sensitivity advantage of 7-T MRI in conjunction with = dedicated,=20 home-built RF coils, Prof. Wald and team have been able to produce = functional=20 brain images that show subtle intracortical structures (0.5 mm) using = 7-T=20 fMRI.
Professor Arno Villringer, Director of the Department of Neurology at =
the Max=20
Planck Institute for Human Cognitive and Brain Sciences, Leipzig, =
Germany,=20
presented studies related to the pathogenesis of obesity in women and =
possible=20
indicators in the brain. With fMRI a 7-T, he said, it will be possible =
to detect=20
patterns of activation and deactivation of different sub-areas in the =
primary=20
somatosensory cortex where, up to now, only a blur of activation can be=20
seen.
Professor Ulrich Dirnagl, Deputy Executive Director of the =
Centre=20
for Stroke Research at the Charit=C3=A9 University Medicine, Berlin, =
also sets his=20
hope in functional UHF MRI. =E2=80=98MR is already in the pole position =
in the spectral=20
diagnosis in stroke and of course in gives us morphology, together with =
early=20
markers of tissue damage such as perfusion and diffusion weighted =
imaging,=E2=80=99 he=20
said, adding that from functional ultra-high-field MRI he expects early =
tissue=20
signatures, indicating a stroke, as well as more detailed insights into=20
pathophysiological brain changes.
UHF MRI in cardiology
Speaking on 7-T in cardiac imaging, Saskia van Elderen MD, of the = Department=20 of Radiology, Leiden University Medical Centre (LUMC), who collaborates = with=20 Professor Andrew Webb, said: =E2=80=98In a direct comparison with lower = field strength=20 3-T, increased signal-to-noise ratio, improved contrast-to-noise ratio = and=20 improved vessel sharpness were obtained at 7-T within a comparable scan=20 duration. The increase in signal-to-noise ratio can be traded for = spatial=20 resolution, which is interesting, for example, in vessel wall imaging,=20 visualising positive outward arterial remodelling one of the earliest = stages of=20 atherosclerosis.=E2=80=99
Pioneer in cardiac MRI, Professor Jeanette Schulz-Menger of the = Charit=C3=A9=20 Medical University, demonstrated that cardiac chamber quantification at = 7-T=20 using 2-D CINE FGRE is feasible and agrees closely with LV parameter = derived=20 from 2D CINE SSFP imaging at 1.5. The signal gain at 7-T helped to = identify=20 fine, subtle anatomic structures, such as pericardium, mitral and = tricuspid=20 valves and their associated papillary muscles, and trabeculae.
Tommy Vaughan, of CMMR in Minneapolis, USA, pointed out that 7-T CMR=20 applications become increasingly a research tool, including early = explorations=20 into the assessment of regional wall motion using tagging techniques and = the=20 assessment of the applicability and efficacy of SSFP imaging techniques = at 7-T.=20 According to Prof. Niendorf it should be noted that CMR at 7.0 T is = still in its=20 infancy and needs to continue to be very carefully validated against CMR = applications established at 1.5-T and 3-T.
The future
In the final session the future perspectives of UHF MRI were = assessed.
Outstanding in dimension is the project to build an 11.7 Tesla whole = body=20 system at Neurospin, a centre belonging to the Atomic Energy Commission = (CEA) in=20 France. Engineer Christopher J Wiggins PhD explained that the aim of = NeuroSpin=20 is to push the current limits of MRI and spectroscopy as far as possible = in=20 order to study the central nervous system (Further details:=20 www.european-hospital.com, a John Brosky report in our Online-Edition.=20 11/12/2009).
In his lecture, Professor Mark E Ladd, from the Erwin-Hahn-Institute = for=20 Magnetic Resonance Imaging in Essen, asked whether 7-T will go clinical = -- and=20 answered his own question: =E2=80=98Not yet=E2=80=99. Although technical = performance has been=20 demonstrated for particular cases, diagnostic performance preliminary in = very=20 small case studies, as yet there has been no demonstration of diagnostic = or=20 therapeutic impact, patient outcome, or societal efficacy.
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