High-Field MR Imaging (Medical Radiology)

The thalamus was also segmented at 1. Although several sequences have been investigated for the visualization of basal ganglia structures at clinical field strengths, DBS structures such as the motor part of the STN, and certain regions within the thalamus, such as the ventrolateral nuclei, need to be displayed more distinctively in order to rely on these images solely for targeting.

Several studies identified deep-brain sub structures at ultra-high field using different MRI contrasts. These studies, reviewed below, show the high potential of ultra-high field MRI to accurately identify and delineate thalamic, parathalamic and subthalamic nuclei. Table 3 shows detailed scanning parameters of the described studies, referred to by line numbers. Since the installation of the first ultra-high field MR scanner, several studies investigated the visualization of deep-brain structures at ultra-high field in vivo Table 4.

Overview of the basal ganglia and related sub structures that have been identified using different protocols at ultra-high field MRI. These findings were later confirmed in sagittally recorded slices with similar acquisition parameters Table 3 -2 Novak et al. In , the same group showed that on GE phase images Table 3 -3 , within the SN, the SN pars dorsalis and SN pars lateralis had a higher signal intensity than the matrix of the SN, and within the RN, the medullary lamella showed a higher signal intensity than the RN pars oralis Abduljalil et al.

A more detailed description of the visualization of the basal ganglia at 7T with three different scanning sequences, exploiting T1-weighted, T2-weighted and susceptibility-weighted imaging, was published in Table 3 Also, SWI allowed visualization of varying levels of contrast within the RN and two of the laminae within the GP lamina pallidi medialis and incompleta , thus also distinguishing between the GPi and the GPe. Within the thalamus, it showed intensity variations corresponding to the locations of the ventral intermediate nucleus Vim , the anterior and medial boundaries of the pulvinar, and the boundary of the nucleus ventralis caudalis as identified with the Schaltenbrand and Wahren atlas Schaltenbrand et al.

Examples of structures identified at ultra-high field. A Adopted with permission from Abosch et al. Ultra-high field 7T susceptibility-weighted axial and coronal images show a clearly delineated subthalamic nucleus STN , a boundary between the STN and substantia nigra, and heterogeneous signal intensity in the red nucleus. B Adopted with permission from Deistung et al. Axial 7T susceptibility map displaying a the head of the caudate nucleus, b anterior limb of the internal capsule, c putamen, d external capsule, e anterior commissure, f external globus pallidus, g lamina pallidi medialis, h pallidum mediale externum, i lamina pallidi incompleta, j pallidum mediale internum, k posterior limb of internal capsule, l subthalamic nucleus, and m red nucleus.

C Adopted with permission from Deistung et al. E,J show overlays of substructures of the thalamus according to the Schaltenbrand et al. In , Eapen et al. In two later studies, susceptibility maps were investigated. The use of susceptibility maps generated from three single-echo GE phase data sets with different head positions Table 3 also facilitated detailed visualization of structures Deistung et al. It provided discrimination between the subnuclei within the SN, and allowed for accurate discrimination of the STN from the SN and surrounding gray matter and white matter. Furthermore, within the GP, these maps showed the lamina pallidi medialis and lamina pallidi incompleta Figure 1B.

The RN displayed substructures in the susceptibility maps, facilitating identification of the medullary lamella, and the RN pars oralis and RN pars dorsomedialis showed a significantly increased susceptibility, compared to the RN pars caudalis. Finally, within the thalamus clear intensity variations were observed on these susceptibility maps corresponding to the Vim, pulvinar, lateral and medial geniculate nucleus, dorsomedial nucleus, and dorsal nuclei group as identified with the Schaltenbrand and Wahren atlas Schaltenbrand et al.

In two other studies by Kerl et al. In one study, DWI Table 3 was used to estimate the pathways between seven regions of interest: Seven pathways could be successfully identified: These projections were also used to create subparcellations of the SN, possibly corresponding to the SN pars reticulata and SN pars compacta; subdivisions of the STN into a dorsolateral and ventromedial part; subdivisions of the GPe into medial, lateral and rostro-ventral parts; subdivisions of the GPi into laterocaudal, rostral, and mid portions; and many subdivisions within the thalamus.

When scanning ex vivo , even higher resolution and higher SNR can be obtained due to the possibility of longer scan times and less movement artifacts. Although fixed tissue may suffer from altered tissue properties, such as decreases in T1 and T2 Tovi and Ericsson, and a decreased diffusion coefficient D'Arceuil et al. Several studies employed ex-vivo imaging for investigating the deep-brain structures at ultra-high field Table 4. In , the STN and its surroundings were explored at 9. On these T1-weighted images Table 3 , the RN and SN, which displayed heterogeneous signal intensity, could be visualized Soria et al.

Furthermore, a hypointense signal band was seen between the SN and STN facilitating easy separation of the two structures. Also the anteromedial part of the STN was relatively hypointense compared to the posterolateral portion, which might be related to the subdivision of the STN in a limbic, associative and sensorimotor part. These studies show that ultra-high field MRI can aid substantially in the identification of small sub structures including the separation between the STN and SN and the laminae within the GP both ex vivo and in vivo.

In addition to the qualitative description of the visibility of deep-brain structures with ultra-high field MRI, comparisons between different sequences and image reconstruction methods have been made see Table 5. In a previously mentioned study from , magnitude, phase-weighted magnitude SWI , and phase images of a GE dataset Table 3 -3 , were compared for their capability to visualize sub structures Abduljalil et al. On magnitude images the SN and RN showed up hypointense and on phase images, substructures within the SN could be distinguished as well.

Ultra-High-Field MR Neuroimaging

The combined magnitude and phase images added little extra to the magnitude and phase images separately. The mapping methods consisted of a a multi-orientation method using images acquired with differing head positions, b a regularized single-orientation method, and c a threshold-based single-orientation method.

Most structures were identified in the SW images see Table 4 , followed by the T2-weighted images Figure 2. The T1-weighted images showed no obvious structures. Adopted with permission from Abosch et al. The susceptibility-weighted images show the highest detail followed by the T2-weighted images. Qualitative analysis by a neuroanatomist revealed that susceptibility maps in general facilitated the most detailed visualization of structures.

Finally, in a recent study by the same group, the CNR between several brain stem structures and their surroundings were compared between sequences Table 3 In addition to comparisons between different sequences, some studies compared similar sequences between different field strengths see Table 6.

In a study, the difference between a 7T GE image Table 3 -4 and a 1. Visual inspection showed that the 7T image displayed better contrast, SNR and resolution. However, comparison is difficult because the acquisition parameters of the 1. A thorough quantitative investigation of the visibility of the STN related to field strength was performed in Cho et al.

Furthermore, all quantitative measures increased with field strength, and the SNR and contrast were significantly improved at 7T compared to 1. Finally, the two studies by Kerl et al. This makes it possible to compare the SNRs and CNRs of the different studies between field strengths, when adjusted for voxel size, although it should be noted that for the T1- and T2-weighted images different sequences were used between field strengths.

However, the CNRs of both structures were substantially higher on all the 7T sequences than on the corresponding 3T sequences. Overview of studies that compare scan protocols between field strengths. Adapted with permission from Cho et al. These studies suggest that 7T MRI can better facilitate accurate targeting of deep brain structures than 1. Accurate visualization of deep-brain structures is important to improve our understanding of their anatomy, connectivity and function, and for improved surgical targeting for DBS in movement and psychiatric disorders. To date, targeting based on direct visualization of DBS targets with T2-weighted 1.

Structures that have been identified at ultra-high field include: The improved visualization of the basal ganglia with ultra-high field MRI discussed here provides good perspectives for clinical practice.

Magnetic resonance imaging - Wikipedia

The clear delineation of DBS target structures and their possible subdivisions may aid in more accurate targeting, which may reduce negative side effects and shorten surgery duration, or it may even allow surgery under general anesthesia. Furthermore, ultra-high field MRI also shows potential for more accurate diagnosis and monitoring of basal ganglia diseases due to, for example, improved identification of the SN pars compacta and SN pars reticulata, which may in its turn facilitate improved patient specific treatments. In addition, ultra-high field MRI promises to be a versatile tool in clinically oriented research of the deep brain nuclei.

It might help us to improve our current understanding of the functionality of the healthy basal ganglia and its disease processes with high resolution functional MRI and connectivity analyses. When in the end considering the optimal scan protocol for visualizing the DBS targets for clinical purposes at ultra-high field, both image quality and practical requirements need to be taken into account. In terms of hardware, it is recommended to use a head coil with a high number of receive channels i. This has been shown to improve the SNR de Zwart et al.

• Southern Star: Destiny Romance.
• Improved Visualization of the Brain at 7T.
• ONE STEP AT A TIME (Hugo the Happy Starfish - Educational Childrens Book Collection 5).

In terms of scan protocol, based on the described literature, we recommend to use a 3D multi-echo GE sequence with an isotropic resolution of 0. The 3D sequence facilitates small and isotropic voxel sizes, which ensures good resolution in every plane which is important for distinguishing the STN from the SN.

Since the basal ganglia are located within the same axial oblique slab of approximately 4—5 cm thickness, we advise to shorten scan time by covering only this part of the brain. If more time reduction is required, partial Fourier imaging, elliptical k-space coverage, or parallel imaging can be considered as well. When planning a DBS surgery, the MR images are often registered to CT images, resulting in images that both display the stereotactic frame from the CT image as well as contrast within the brain.

This registration may be more reliable, however if a whole brain MR image is available as an intermediate step. Despite these promising results concerning accurate and high-resolution visualization of the small deep brain sub structures, several issues still need to be addressed before they can routinely be employed in direct targeting for DBS. Firstly, ultra-high field images have an increased risk of geometrical distortions compared to 1.

The severity of these distortions at 7T in deep-brain regions has been investigated in several studies. One study compared the coordinates of marker points in a phantom imaged with 1. The maximum distortion in either x-, y-, or z-direction at 7T was 1. Furthermore, the fewest distortions were observed in the center of the phantom. Furthermore, the midbrain region, containing many DBS targets, required the least correction. Quantitative comparison showed that the distances of the T2-weighted images were significantly less than 1 mm suggesting that affine registration of T1- and T2-weighted 7T images to CT images can already provide MR images with midbrain distortions comparable to those of 1.

The field strength of the magnet is measured in teslas — and while the majority of systems operate at 1. Most clinical magnets are superconducting magnets, which require liquid helium. Lower field strengths can be achieved with permanent magnets, which are often used in "open" MRI scanners for claustrophobic patients.

Each tissue returns to its equilibrium state after excitation by the independent relaxation processes of T1 spin-lattice ; that is, magnetization in the same direction as the static magnetic field and T2 spin-spin ; transverse to the static magnetic field. To create a T1-weighted image, magnetization is allowed to recover before measuring the MR signal by changing the repetition time TR. This image weighting is useful for assessing the cerebral cortex, identifying fatty tissue, characterizing focal liver lesions and in general for obtaining morphological information, as well as for post-contrast imaging.

To create a T2-weighted image, magnetization is allowed to decay before measuring the MR signal by changing the echo time TE. This image weighting is useful for detecting edema and inflammation, revealing white matter lesions and assessing zonal anatomy in the prostate and uterus. The standard display of MRI images is to represent fluid characteristics in black and white images, where different tissues turn out as follows:.

MRI has a wide range of applications in medical diagnosis and more than 25, scanners are estimated to be in use worldwide. MRI is the investigation of choice in the preoperative staging of rectal and prostate cancer and, has a role in the diagnosis, staging, and follow-up of other tumors.

MRI is the investigative tool of choice for neurological cancers, as it has better resolution than CT and offers better visualization of the posterior cranial fossa , containing the brainstem and the cerebellum. The contrast provided between grey and white matter makes MRI the best choice for many conditions of the central nervous system , including demyelinating diseases , dementia , cerebrovascular disease , infectious diseases , Alzheimer's disease and epilepsy. Cardiac MRI is complementary to other imaging techniques, such as echocardiography , cardiac CT , and nuclear medicine.

Its applications include assessment of myocardial ischemia and viability , cardiomyopathies , myocarditis , iron overload , vascular diseases, and congenital heart disease. Applications in the musculoskeletal system include spinal imaging , assessment of joint disease, and soft tissue tumors. Hepatobiliary MR is used to detect and characterize lesions of the liver , pancreas , and bile ducts. Focal or diffuse disorders of the liver may be evaluated using diffusion-weighted , opposed-phase imaging, and dynamic contrast enhancement sequences. Extracellular contrast agents are used widely in liver MRI and newer hepatobiliary contrast agents also provide the opportunity to perform functional biliary imaging.

Anatomical imaging of the bile ducts is achieved by using a heavily T2-weighted sequence in magnetic resonance cholangiopancreatography MRCP. Functional imaging of the pancreas is performed following administration of secretin. MR enterography provides non-invasive assessment of inflammatory bowel disease and small bowel tumors.

Navigation menu

MR-colonography may play a role in the detection of large polyps in patients at increased risk of colorectal cancer. Magnetic resonance angiography MRA generates pictures of the arteries to evaluate them for stenosis abnormal narrowing or aneurysms vessel wall dilatations, at risk of rupture. MRA is often used to evaluate the arteries of the neck and brain, the thoracic and abdominal aorta, the renal arteries, and the legs called a "run-off". A variety of techniques can be used to generate the pictures, such as administration of a paramagnetic contrast agent gadolinium or using a technique known as "flow-related enhancement" e.

Techniques involving phase accumulation known as phase contrast angiography can also be used to generate flow velocity maps easily and accurately. Magnetic resonance venography MRV is a similar procedure that is used to image veins. In this method, the tissue is now excited inferiorly, while the signal is gathered in the plane immediately superior to the excitation plane—thus imaging the venous blood that recently moved from the excited plane.

MRI for imaging anatomical structures or blood flow do not require contrast agents as the varying properties of the tissues or blood provide natural contrasts. However, for more specific types of imaging, exogenous contrast agents may be given intravenously , orally , or intra-articularly. Anaphylactoid reactions are rare, occurring in approx. Although gadolinium agents have proved useful for patients with renal impairment, in patients with severe renal failure requiring dialysis there is a risk of a rare but serious illness, nephrogenic systemic fibrosis , which may be linked to the use of certain gadolinium-containing agents.

The most frequently linked is gadodiamide , but other agents have been linked too. In Europe, where more gadolinium-containing agents are available, a classification of agents according to potential risks has been released. An MRI sequence is a particular setting of radiofrequency pulses and gradients, resulting in a particular image appearance.

Magnetic resonance spectroscopy MRS is used to measure the levels of different metabolites in body tissues. The MR signal produces a spectrum of resonances that corresponds to different molecular arrangements of the isotope being "excited". This signature is used to diagnose certain metabolic disorders, especially those affecting the brain, [66] and to provide information on tumor metabolism. Magnetic resonance spectroscopic imaging MRSI combines both spectroscopic and imaging methods to produce spatially localized spectra from within the sample or patient. The spatial resolution is much lower limited by the available SNR , but the spectra in each voxel contains information about many metabolites.

Because the available signal is used to encode spatial and spectral information, MRSI requires high SNR achievable only at higher field strengths 3 T and above. However, recent compressed sensing -based software algorithms e. Real-time MRI refers to the continuous imaging of moving objects such as the heart in real time. This gives a temporal resolution of 20—30 ms for images with an in-plane resolution of 1. Real-time MRI is likely to add important information on diseases of the heart and the joints, and in many cases may make MRI examinations easier and more comfortable for patients, especially for the patients who cannot hold their breathings or who have arrhythmia.

The lack of harmful effects on the patient and the operator make MRI well-suited for interventional radiology , where the images produced by an MRI scanner guide minimally invasive procedures.

Technology Report ARTICLE

Such procedures use no ferromagnetic instruments. Some specialized MRI systems allow imaging concurrent with the surgical procedure. More typically, the surgical procedure is temporarily interrupted so that MRI can assess the success of the procedure or guide subsequent surgical work. In guided therapy, high-intensity focused ultrasound HIFU beams are focused on a tissue, that are controlled using MR thermal imaging. This technology can achieve precise ablation of diseased tissue. MR imaging provides a three-dimensional view of the target tissue, allowing for the precise focusing of ultrasound energy.

The MR imaging provides quantitative, real-time, thermal images of the treated area. This allows the physician to ensure that the temperature generated during each cycle of ultrasound energy is sufficient to cause thermal ablation within the desired tissue and if not, to adapt the parameters to ensure effective treatment. Hydrogen has the most frequently imaged nucleus in MRI because it is present in biological tissues in great abundance, and because its high gyromagnetic ratio gives a strong signal.

However, any nucleus with a net nuclear spin could potentially be imaged with MRI. Such nuclei include helium -3, lithium -7, carbon , fluorine , oxygen , sodium , phosphorus and xenon Gaseous isotopes such as 3 He or Xe must be hyperpolarized and then inhaled as their nuclear density is too low to yield a useful signal under normal conditions. Moreover, the nucleus of any atom that has a net nuclear spin and that is bonded to a hydrogen atom could potentially be imaged via heteronuclear magnetization transfer MRI that would image the high-gyromagnetic-ratio hydrogen nucleus instead of the low-gyromagnetic-ratio nucleus that is bonded to the hydrogen atom.

Multinuclear imaging is primarily a research technique at present. However, potential applications include functional imaging and imaging of organs poorly seen on 1 H MRI e. Inhaled hyperpolarized 3 He can be used to image the distribution of air spaces within the lungs. Injectable solutions containing 13 C or stabilized bubbles of hyperpolarized Xe have been studied as contrast agents for angiography and perfusion imaging. Multinuclear imaging holds the potential to chart the distribution of lithium in the human brain, this element finding use as an important drug for those with conditions such as bipolar disorder.

MRI has the advantages of having very high spatial resolution and is very adept at morphological imaging and functional imaging. MRI does have several disadvantages though. This problem stems from the fact that the population difference between the nuclear spin states is very small at room temperature. For example, at 1. Improvements to increase MR sensitivity include increasing magnetic field strength, and hyperpolarization via optical pumping or dynamic nuclear polarization.

There are also a variety of signal amplification schemes based on chemical exchange that increase sensitivity. To achieve molecular imaging of disease biomarkers using MRI, targeted MRI contrast agents with high specificity and high relaxivity sensitivity are required. To date, many studies have been devoted to developing targeted-MRI contrast agents to achieve molecular imaging by MRI. Commonly, peptides, antibodies, or small ligands, and small protein domains, such as HER-2 affibodies, have been applied to achieve targeting. To enhance the sensitivity of the contrast agents, these targeting moieties are usually linked to high payload MRI contrast agents or MRI contrast agents with high relaxivities.

In the UK, the price of a clinical 1. Pre-polarizing MRI PMRI systems using resistive electromagnets have shown promise as a low-cost alternative and have specific advantages for joint imaging near metal implants, however they are likely unsuitable for routine whole-body or neuroimaging applications. MRI scanners have become significant sources of revenue for healthcare providers in the US. This is because of favorable reimbursement rates from insurers and federal government programs.

In the US, the Deficit Reduction Act of significantly reduced reimbursement rates paid by federal insurance programs for the equipment component of many scans, shifting the economic landscape. Many private insurers have followed suit. This covers three basic scans including one with an intravenous contrast agent as well as a consultation with the technician and a written report to the patient's physician. MRI is in general a safe technique, although injuries may occur as a result of failed safety procedures or human error.

The safety of MRI during the first trimester of pregnancy is uncertain, but it may be preferable to other options. Peripheral nerve stimulation, which is related to the speed of switching gradients, is also monitored and limited. It is not field strength—dependent. Currently, only 2 contrast injectors and a radiofrequency identification device chip are approved for 7T scanners.

Ultra-high-field MR imaging has great potential to display in vivo subtle abnormalities that are not detectable at lower field strengths. Increasing the field strength provides opportunities to visualize subtle anatomic abnormalities associated with disease; reveal spatially varying metabolite ratios between smaller structures; isolate functional signal that is more tightly coupled to underlying neuronal activity; image microvasculature and blood products in great detail; and tap into the signal from nuclei other than protons, revealing new information about cellular activity.

By using novel RF pulse and pulse sequence designs, we can overcome the technical barriers confounding ultra-high-field MR imaging and fully exploit the SNR advantage and enhanced contrast to visualize the brain in unprecedented detail. The combination of high-resolution anatomic, spectroscopic, and functional MR imaging at 7T has the potential to be a powerful, noninvasive toolset for improved diagnosis and treatment of a wide range of neurologic diseases and disorders.

Continued technical development of new signal transmission and readout methods is needed to overcome the physical limitations of performing high-field imaging in vivo within reasonable times and appropriate safety limits. Additional clinical studies are needed to demonstrate the value of 7T for disease diagnosis, treatment, and management.

It is expected that continued advances in high-field imaging will lead to a new understanding of neurologic disease and improved detection and treatment of such diseases. These will propel the field forward. We would like to thank Dr Christina Triantafyllou for providing information on the prevalence and availability of high-field MR imaging scanners and Dr Bernd Stoeckel for his input on current technical capabilities and limitations of 7T scanners. National Institutes of Health, Comments: Some of the images included in this article were obtained as part of my research at Mount Sinai.

National Center for Biotechnology Information , U. Author manuscript; available in PMC Oct 1. Author information Copyright and License information Disclaimer. Translational and Molecular Imaging Institute P. Indicates open access to non-subscribers at www. See other articles in PMC that cite the published article. Table Relationship of imaging parameters and main magnetic field strength. Open in a separate window. Vascular and Functional Imaging Increasing the field strength provides opportunities for MR imaging contrast mechanisms, including improved susceptibility, blood oxygen level-dependent BOLD and flow-dependent contrast.

MR Spectroscopic Imaging The chemical shift differences among metabolite resonances are directly proportional to field strength Table. DTI The increased SNR at 7T, coupled with improved receiver coils, has been shown to increase the certainty and accuracy of determining DTI-based parameters such as fractional anisotropy, compared with 3T and 1. Multinuclear Imaging Greater SNR provides a signal boost to nuclei other than protons, such as sodium 23 Na and phosphorus 31 P , which provide a means of probing important cell processes, different metabolic pathways, and new relaxation mechanisms.

Brain Tumors Ultra-high-field MR imaging may be applied in different ways to better visualize brain tumor pathology. Alzheimer Disease One early pathologic change in Alzheimer disease is neuronal loss in specific subfields of the hippocampus. Psychiatric Illness The etiology of mood and anxiety disorders such as major depressive disorder remains poorly understood.

Technical and Physical Limitations The present use of ultra-high-field MR imaging is limited by technical and patient concerns. B 0 Inhomogeneity B 0 inhomogeneity directly scales with field strength Table. B 1 Inhomogeneity One of the most difficult problems to overcome at high magnetic fields is the severe B 1 inhomogeneity over the volume of interest. Changing Relaxation Behavior Relaxation constants change as a function of field strength Table. Increased Chemical Shift Localization Error MR spectroscopy is planned within a volume of interest specified at the scanner.

Engineering Solutions Solutions to some of the technical issues at 7T include customized RF pulse and pulse sequence designs to produce uniform transmission profiles while minimizing deposited RF energy SAR. Customized RF Pulses and Pulse Sequences Creative RF pulse and pulse sequence design may be used to overcome many of the physical limitations of existing hardware so that the full signal gain and enhanced contrast afforded by 7T may be exploited.

Tailored RF Pulses to Compensate for B 1 Inhomogeneities Another solution to B 1 inhomogeneity is to create pulses that are specifically designed to compensate for the nonuniformities in the B 1 field. Parallel Imaging and Lower Flip Angle Schedules Parallel imaging may be used in conjunction with segmented readouts to accelerate acquisition times to overcome some of the SAR limitations and B 0 field distortions.

Specialized Parallel Transmit Hardware Another method to gain more control over the transmitted B 1 profile is to use specialized hardware solutions such as parallel transmit arrays. Multinuclear Imaging When imaging nuclei other than hydrogen, different physical considerations come into play. Practical Considerations Siting The ease of siting a 7T magnet has greatly improved in recent years.

Cost One factor in operating a 7T scanner has been helium boil-off. Patient Experience Risks at 7T are similar to those at 1. Transitory Physiologic Effects With regard to patient comfort level, the 7T scanner is very similar to 3T, except for limited transitory physiologic effects. Noise Levels, RF Energy Deposition, and Peripheral Nerve Stimulation Noise levels, RF energy deposition, and peripheral nerve stimulation are presently minimized by adherence to the conservative safety guidelines set by regulatory bodies such as the FDA and institutional safety committees.

Implantable Devices Currently, only 2 contrast injectors and a radiofrequency identification device chip are approved for 7T scanners. Conclusions and Future Directions Ultra-high-field MR imaging has great potential to display in vivo subtle abnormalities that are not detectable at lower field strengths.

Acknowledgments We would like to thank Dr Christina Triantafyllou for providing information on the prevalence and availability of high-field MR imaging scanners and Dr Bernd Stoeckel for his input on current technical capabilities and limitations of 7T scanners. Clow H, Young IR. Magnetic Resonance Imaging of the Brain and Spine. MRI at 7 Tesla and above: J Magn Reson Imaging. Ultrahigh field magnetic resonance imaging and spectroscopy. Cytoarchitecture of the human cerebral cortex: MR microscopyof excised specimens at 9.

Vascularization of the Cerebellum and the Brain Stem. Ultra-high field 7T MRI: First clinical study on ultra-high-field MR imaging in patients with multiple sclerosis: High-resolution 7T MRI of the human hippocampus in vivo. Subfields of the hippocampal formation at 7T MRI: Human hippocampal subfields in young adults at 7.

Within-digit functional parcellation of Brodmann areas of the human primary so-matosensory cortex using functional magnetic resonance imaging at 7 Tesla. Spin-echo fMRI in humans using high spatial resolutions and high magnetic fields. Dual-echo arteriovenography imaging with 7T MRI. Mayer D, Spielman DM. Detection of glutamate in the human brain at 3 T using optimized constant time point resolved spec-troscopy. Signal to noise ratio and uncertainty in diffusion tensor imaging at 1.

Evaluation of a modified Stejskal-Tanner diffusion encoding scheme, permitting a marked reduction in TE, in diffusion-weighted imaging of stroke patients at 3 T. Feinberg DA, Setsompop K. Ultra-fast MRI of the human brain with simultaneous multi-slice imaging. Improving diffusion MRI using simultaneous multi-slice echo planar imaging. The potential of relaxation-weighted sodium magnetic resonance imaging as demonstrated on brain tumors. Sodium MRI using a density-adapted 3D radial acquisition technique. In vivo 35Cl MR imaging in humans: SodiumMRimagingofacute and subacute stroke for assessment of tissue viability.

Neuroimaging Clin N Am. Loss of cell ion homeostasis and cell viability in the brain: Curr Top Dev Biol. Sodiumimagingofhumanbrain at 7 T with channel array coil. High-resolution sodium imaging of human brain at 7 T. AdvancedMR methods at ultra-high field 7 Tesla for clinical musculoskeletal applications. A method for estimating in-tracellular sodium concentration and extracellular volume fraction in brain in vivo using sodium magnetic resonance imaging.

Hippocampal sclerosis in temporal lobe epilepsy: Longitudinal brain imaging of five malignant glioma patients treated with bevacizumab using susceptibility-weighted magnetic resonance imaging at 7 T. Clinical magnetic resonance imaging of brain tumors at ultrahigh field: Top Magn Reson Imaging. Using high-resolution MR imaging at 7T to evaluate the anatomy of the midbrain dopami-nergic system.

Imaging of patients with hippocampal sclerosisat 7 Tesla: Madan N, Grant PE. New directions in clinical imaging of cortical dysplasias. Cerebral cavernous hemangiomas at 7 Tesla: Advances in ultra-high field MRI for the clinical management of patients with brain tumors. Quantitative tissue sodium concentration mapping of the growth of focal cerebral tumors with sodium magnetic resonance imaging.

Quantitative sodium MR imaging and sodium bioscales for the management of brain tumors. Tissue sodium concentration inhuman brain tumors asmeasured with 23NaMR imaging. Quantitative susceptibility mapping differentiates between blood depositions and calcifications in patients with glioblastoma. Semiquantitative assessment of intratumoral susceptibility signals using non-contrast-enhanced high-field high-resolution susceptibility-weighted imaging in patients with gliomas: Differentiation of glioblastoma and primary CNS lymphomas using susceptibility weighted imaging.

Quantitative in vivo magnetic resonance imaging of multiple sclerosis at 7 Tesla with sensitivity to iron. Prominent perivenular spaces in multiple sclerosis as a sign of perivascular inflammation in primary demyelination. Seven-Tesla magnetic resonance imaging: A pathophysiological frame work of hippocampal dysfunction in ageing and disease. A novel imaging marker.