Published online August 16, A dedicated head-only MRI scanner for point-of-care imaging. Initial phantom studies for an office-based low-field MR system for prostate biopsy.

Int J Comput Assist Radiol Surg. Ghazinoor S, Crues JV 3rd, Crowley C. Low-field musculoskeletal MRI. Klein HM. Low-Field Magnetic Resonance Imaging. Schick F, Pieper CC, Kupczyk P, et al.

Invest Radiol. Hori M, Hagiwara A, Goto M, Wada A, Aoki S. Low-field magnetic resonance imaging: Its history and renaissance. Low-Field Magnetic Resonance Imaging: A New Generation of Breakthrough Technology in Clinical Imaging. Needle Heating During Interventional Magnetic Resonance Imaging at 1.

Advocating the Development of Next-Generation, Advanced-Design Low-Field Magnetic Resonance Systems. Susceptibility artifacts from metallic markers and cardiac catheterization devices on a high-performance 0. Magn Reson Imaging. Webb AG. Magnetic Resonance Technology: Hardware and System Component Design.

Royal Society of Chemistry; Buckley BW, MacMahon PJ. Radiology and the Climate Crisis: Opportunities and Challenges—Radiology In Training. Multisection fat-water imaging with chemical shift selective presaturation.

Frahm J, Haase A, Hänicke W, Matthaei D, Bomsdorf H, Helzel T. Chemical shift selective MR imaging using a whole-body magnet. Am J Respir Crit Care Med. Bhattacharya I, Ramasawmy R, Javed A, et al. Assessment of Lung Structure and Regional Function Using 0. Oxygen-enhanced functional lung imaging using a contemporary 0.

NMR in Biomedicine. Self-gated 3D stack-of-spirals UTE pulmonary imaging at 0. Campbell-Washburn AE, Suffredini AF, Chen MY. High-Performance 0. High-performance low field MRI enables visualization of persistent pulmonary damage after COVID Campbell-Washburn AE, Malayeri AA. T2-weighted lung imaging using a 0.

Published online Evaluation of myocardial infarction by cardiovascular magnetic resonance at 0. JACC Cardiovasc Imaging.

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Curr Cardiol Rep. Published online February 2, High- Versus Low-Field MR Imaging. Radiologic Clinics of North America. Knee Surgery, Sports Traumatology, Arthroscopy.

Physica Medica. Diagnostic abdominal MR imaging on a prototype low-field 0. Abdom Radiol NY. Campbell-Washburn AE, Mancini C, Conrey A, et al. Evaluation of hepatic iron overload using a contemporary 0. Deoni SCL, Medeiros P, Deoni AT, et al.

Development of a mobile low-field MRI scanner. Sheth KN, Mazurek MH, Yuen MM, et al. Assessment of Brain Injury Using Portable, Low-Field Magnetic Resonance Imaging at the Bedside of Critically Ill Patients. JAMA Neurol. Published online September 8, Portable, Bedside, Low-field Magnetic Resonance Imaging in an Intensive Care Setting for Intracranial Hemorrhage Accessed March 5, abstract Moser E, Laistler E, Schmitt F, Kontaxis G.

Ultra-High Field NMR and MRI—The Role of Magnet Technology to Increase Sensitivity and Specificity. Ultra high resolution imaging of the human head at 8 tesla: 2K× 2K for Y2K.

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Wu W, Miller KL. Image formation in diffusion MRI: A review of recent technical developments. Abduljalil AM, Schmalbrock P, Novak V, Chakeres DW.

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Journal of Neuroimaging. x Öz G, Deelchand DK, Wijnen JP, et al. Niesporek SC, Nagel AM, Platt T. Multinuclear MRI at Ultrahigh Fields. Top Magn Reson Imaging. Platt T, Ladd ME, Paech D. Andre JB, Bresnahan BW, Mossa-Basha M, et al. Toward Quantifying the Prevalence, Severity, and Cost Associated With Patient Motion During Clinical MR Examinations.

J Am Coll Radiol. Federau C, Gallichan D. Motion-Correction Enabled Ultra-High Resolution In-Vivo 7T-MRI of the Brain. PLoS One. Mattern H, Sciarra A, Lüsebrink F, Acosta-Cabronero J, Speck O. Prospective motion correction improves high-resolution quantitative susceptibility mapping at 7T.

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Published online March 10, Quantitative evaluations of geometrical distortion corrections in cortical surface-based analysis of high-resolution functional MRI data at 7T. Heilmaier C, Theysohn JM, Maderwald S, Kraff O, Ladd ME, Ladd SC.

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ECG-based gating in ultra high field cardiovascular magnetic resonance using an independent component analysis approach. J Cardiovasc Magn Reson. Chen I, Saha S. Analysis of an Intensive Magnetic Field on Blood Flow. Electromagnetic Biology and Medicine. Safety of human MRI at static fields above the FDA 8 T guideline: sodium imaging at 9.

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Two different SAR measures relevant to clinical MR scanning follow from these, namely local 10 g SAR and the whole body SAR. As the terms suggest the local SAR is defined as the peak SAR value after spatial averaging over any 10 g of tissue, whereas the partial or whole body SAR is spatially averaged over the entire body and can be estimated from the total RF power deposited in the body.

At low field the SAR increases as the square of the operating frequency [ 40 ]. The same legal SAR-regulations are applicable to UHF-MRI as at lower field strengths. Testing uses an American Standards of Tests and Measurements ASTM standard [ 41 ].

The assumption when using the phantoms recommended by the ASTM which mimic the dielectric properties of tissue is that the spatial distribution of the EM field is well-characterized, which means that the position of the highest electric field, and therefore highest heating, can be predicted and thermal measurements can, therefore, be performed at that location.

However, at 7 T the wavelength of the EM fields in the tissue-mimicking materials is ~13 cm [ 42 ], which means that wave interference occurs inside the phantom which makes prediction of the location of maximum heating much more difficult.

Therefore, many high field studies have deviated from the strict guidelines of the ASTM standard, or have attempted to measure the electric fields directly.

It should be noted that, despite wave interference effects, many groups have shown that these do not always lead to a higher local relative to global SAR [ 42 , 43 ]. Taken all these effects into account, it has been shown that the whole body SAR does not show a quadratic relationship, but more closely adheres to a linear increase with field above 3 T [ 42 ].

There is then, typically, a further factor-of-two safety margin built into the scanning limits. One of the areas of very active research at high field is the use of transmit array technology, in which the transmit RF coil consists of a number of independent channels, each of which can be separately controlled in terms of the magnitude and phase of the transmit power.

These systems have been commercially released for 3 T dual-transmit from all three major vendors and are available for up to eight channels on 7 and 9. This higher risk is caused by the very nature of parallel transmit: tailoring the RF distribution by constructive and destructive interference.

As an example, if one or more transmit coils were to malfunction, the local power deposition can be higher than the calculated level due to the absence of an element of destructive interference. The safety considerations of parallel transmit are, however, not an UHF-MRI specific safety issue, but a more generic safety issue [ 44 ].

These vibrations are coupled into the magnet structure and are manifested as acoustic noise [ 45 , 46 ]. Since the forces are proportional to the strength of the magnetic field, one would expect higher noise levels for higher magnetic fields, as indeed has been noted for example in the 0.

However, the amount of acoustic noise produced by an MRI scanner depends critically on the engineering of the gradient coil and the imaging sequences used, and this non-linearity is making direct predictions highly non-trivial.

In terms of UHF-MRI measurements, echo planar imaging was found to be only slighter louder dB at the entrance-bore of a 7 T scanner than on a clinical 3 T scanner dB made by the same manufacturer, although the imaging sequences were not specifically designed to be comparable [ 39 ].

Also, a conference abstract showed similar maximum noise levels dB for sinusoidal EPI acquired at 7 T as on lower field MRI scanners [ 48 ]. From a practical point-of-view, a very important difference is that commercial head-coils for 7 T MRI are designed with a multi-channel 32 or 16 array insert which is much more tightly fitting than standard head coils at 3 T, making it impossible to employ double ear protection ear plugs plus headphones at 7 T, and one has, therefore, to rely solely on ear plugs.

It is, therefore, not surprising that approximately one-third of the participants undergoing a 7 T MRI examination reported acoustic noise as an important distress factor [ 49 ]. These findings are similar to studies co-ordinated by the high field group in Essen, Germany [ 51 , 52 ].

The long scan duration on average 72 min was the main reason for discomfort, with vertigo and the requirement to lie completely still noted as other sources of discomfort.

In patients, a parallel questionnaire was filled in after a 1. The main differences between experiences at the two field strengths arose from the longer exam duration, the higher acoustic noise, the lower room temperature, and reduced contact with the operator due to lack of clinical experience of the operator.

It should be noted that none of these effects are intrinsic to high field imaging per se: many institutions limit the total scanning time to 1 h, the same as for a 3T scan, and have experienced technicians running the systems.

Regarding specific sensations, the main differences were the more severe experience of vertigo at 7T as well as feelings of nausea, headache, fear, unreality, and experiences of sweat attacks, light flashes, and tachycardia. However, the average score for these sensations, except for the vertigo, was very low 0.

Taken together, these data suggest that besides issues related specifically to a research as compared to clinical-setting and operation long examination times, long time lying still, poor operator communication , the most prominent side-effect of UHF-MRI is increased dizziness, probably caused by vestibular effects as discussed previously.

An informal survey among the UHF sites present at the ISMRM ultra-high field MRI workshop in Noordwijk in showed a wide variation in local policies at 7 T for scanning subjects with implants.

com , the official site of the Institute for Magnetic Resonance Safety, Education, and Research. As of March , however, this site had only tested three objects at 7 T: two contrast agent delivery systems and a human-implantable microchip, all labelled Conditional 5.

Some sites required proper testing according to the ASTM guidelines, whereas others relied on their local testing procedures. The ASTM guidelines include testing procedures for displacement force, torque, RF heating, and the influence on image quality [ 53 , 54 ].

Whereas the first two testing procedures are rather straightforward, as outlined earlier positioning of the implant at the worst case location for RF-heating testing is much more challenging at UHF than for lower fields, due to the substantially increased non-uniformity and asymmetric nature of the EM fields in conducting samples, i.

It has been suggested that EM-simulations should first be performed in order to obtain a good indication of the worst case situation, before actual measurements are performed [ 55 ]. In general, one has to be very careful with implants whose dimensions are close to one-half wavelength, as for lower fields [ 56 ].

Although at quite a few UHF-sites the profile of scanned subjects is restricted to 20—30 year old healthy subjects, as is for example the case for sites focusing on normal cognition or technical development, an increasing number of sites are also including older subjects as well as patients see e.

Both simulations as well as phantom experiments of these wires showed that the maximum temperature rise is less than 1. No adverse effects have been observed after more than 20 volunteers with dental retainer wires have undergone head 7 T scans. However, it should be noted that this study focused on the practical safety issues without adhering strictly to the ASTM guidelines.

When scanning older subjects and patients, one of the more frequently seen implants are cardiac stents. Unfortunately, there are relatively few data available on the displacement force or torque although one ISMRM-abstract tested twenty stents and recorded a maximum deflection angle of 33°, which is smaller than the gravitational force [ 58 ].

Potential heating due to RF deposition has been investigated by Santoro et al. who showed a temperature rise around 3 °C near the tip of the stent for a 60 min scan at a SAR-level three times higher than the IEC guidelines.

However, in practice more than one cardiac stent is frequently implanted and the quoted study did not show whether combinations of more than one stent can also be considered safe. Of course, this is a challenging question, since the exact positioning of the stents with respect to each other and occurrence of partial overlap as well as difference in total length, provides a very large parameter space to investigate.

The group of Vanderbildt tested 28 different implants and objects ranging from aneurysm clips and biopsy tissue markers to an armor-piercing bullet!

Nine of the 28 objects showed a deflection angle of greater than 45°, which according to the ASTM guidelines could pose a safety risk.

Among these nine objects, several are actually considered conditionally safe or even MR safe at 3T. Using the argument that the UHF-MRI scanners do not have a body-coil, the authors only tested the RF heating for brain implants which would be located inside the head-coil.

The temperature rise did not exceed the 1 °C during Besides these studies, other published articles describe safety studies of aneurysm clips [ 59 ], implants for ear-nose-throat surgery [ 60 ], upper eye implants [ 61 ], cranial fixation plates [ 62 ], an EEG-cap [ 63 ], intraocular lenses [ 64 ], actuators [ 65 ], ballistic objects [ 66 ], and extracranial neurosurgical implants [ 67 ].

During more than a decade of experience with UHF-MRI, no severe adverse effects have been reported and all studies on subjective acceptance of UHF-MRI have shown good acceptance both by normal volunteers as well as patients.

The only important side-effect that is frequently reported is vertigo resulting in the most extreme cases in nausea. Until a few years ago, this was mainly attributed to rapid patient table-motion through an inhomogeneous magnetic field, but the latest studies have indicated that a more plausible cause is vestibular activation due to Lorenz forces on ion currents in the semicircular loops.

These forces can also cause involuntary eye motion, i. Taking all these observations into account, the conclusion is that UHF-MRI is, safety-wise, highly comparable to clinical systems at 3 or 1. However, the legal status of UHF-MRI as well as official documentation is currently lagging well behind the lower field strengths.

Acceptance of the amendment to the IEC standards to increase the first level control operating mode to 8 T would open up the possibility of CE-marking of UHF-MRI scanners, as well as formal FDA approval for clinical scanning.

Although not changing many applications at UHF-MRI in practice, because scientific experiments with normal volunteers as well as patients would still require IRB approval, it would ease the way for diagnostic clinical use of UHF-MRI.

Due to the lack of formal approval of UHF-MRI scanners, in many countries it is troublesome or indeed impossible to obtain financial reimbursement for clinical UHF-MRI scans, even in situations in which UHF-MRI would enhance diagnosis compared to 3T MRI alone.

Of course, the vendors of UHF-MRI would still need to do the formal application for FDA-approval and CE-marking even after the potential change by the IEC to approve use of UHF-MRI in the first level control operating mode. Currently, the main problem for deciding whether to scan subjects with implants is the lack of exchange of results of safety tests performed at the different UHF sites.

Although several sites publish some findings of their safety tests, many more implants have been tested completely or partially in the different institutes than have not been published in official journals.

This lack of publication as well as the scatter of the few published studies throughout diverse journals, can probably be explained by the necessary time-investment to publish these results and the lack of interest in accepting publications of safety testing on a single implant by the different journals.

There is also disagreement as to how valid the ASTM testing method established for 3 T and 1. In general, it is agreed that careful simulations of the electric fields encountered at the anatomical location of the implant should guide the phantom experiments [ 55 ]. Simulations should be performed in a wide variation of body compositions and dimensions to be able to discern the worst case scenario.

Some guidelines on the how to perform these simulations as well as how to provide convincing evidence that in a phantom experiment a realistic worst case scenario has truly been tested would be very helpful. Overall, a general repository of test results, for example hosted by the International Society for Magnetic Resonance in Medicine, would represent a big step forward in promoting clinical use of UHF-MRI.

Moenninghoff C, Maderwald S, Theysohn JM, Kraff O, Ladd ME, El HN, van de Nes J, Forsting M, Wanke I. Imaging of adult astrocytic brain tumours with 7 T MRI: preliminary results. Eur Radiol. Article PubMed Google Scholar. Lupo JM, Chuang CF, Chang SM, Barani IJ, Jimenez B, Hess CP, Nelson SJ.

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Initial results of cardiac imaging at 7 Tesla. Article CAS PubMed Central PubMed Google Scholar. Graessl A, Renz W, Hezel F, Dieringer MA, Winter L, Oezerdem C, Rieger J, Kellman P, Santoro D, Lindel TD, Frauenrath T, Pfeiffer H, Niendorf T.

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Design of a radiative surface coil array element at 7 T: the single-side adapted dipole antenna. Kraff O, Bitz AK, Kruszona S, Orzada S, Schaefer LC, Theysohn JM, Maderwald S, Ladd ME, Quick HH. An eight-channel phased array RF coil for spine MR imaging at 7 T. Invest Radiol.

Vossen M, Teeuwisse W, Reijnierse M, Collins CM, Smith NB, Webb AG. A radiofrequency coil configuration for imaging the human vertebral column at 7 T. J Magn Reson. McDougall MP, Cheshkov S, Rispoli J, Malloy C, Dimitrov I, Wright SM. Quadrature transmit coil for breast imaging at 7 Tesla using forced current excitation for improved homogeneity.

J Magn Reson Imaging. doi: van de Bank BL, Voogt IJ, Italiaander M, Stehouwer BL, Boer VO, Luijten PR, Klomp DW. Ultra high spatial and temporal resolution breast imaging at 7T. Beenakker JW, van Rijn GA, Luyten GP, Webb AG.

High-resolution MRI of uveal melanoma using a microcoil phased array at 7 T. Van der Kolk AG, Hendrikse J, Zwanenburg JJ, Visser F, Luijten PR. Clinical applications of 7 T MRI in the brain. Eur J Radiol. Moser E, Stahlberg F, Ladd ME, Trattnig S. Versluis MJ, van der Grond J, van Buchem MA, van Zijl P, Webb AG.

High-field imaging of neurodegenerative diseases. Neuroimaging Clin N Am. MRI at 7 Tesla and above: demonstrated and potential capabilities. Excellent review of the current status of ultra - high field MRI both regarding technical challenges and solutions as well as clinical applications.

Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health.

Criteria for significant risk investigations of magnetic resonance diagnostic devices. Accessed April Basic document stating that MRI up to 8 Tesla is considered a non - significantly risk device for human subjects older than 1 month.

International Commission on Non-Ionizing Radiation Protection. Wide Bore High Field MRI A High Field MRI helps doctors identify medical conditions at their earliest and most treatable stages. Working together with our highly skilled staff, our radiologists provide expertise in nearly every type of imaging including the following specialty areas: Neuroradiology Musculoskeletal imaging Breast imaging Abdominal imaging Pediatric imaging What will I experience during an MRI?

You will be asked to lie down on a table and remain still for the entirety of the procedure, which is comprised of a series of sequences each lasting from two to fifteen minutes for a total of 15 to 45 minutes.

Slight movement is allowed between sequences. The table will slide into a tunnel-like cavity of the MRI machine that photographs your body at regular increments. A Technologist may administer a contrast material in order to enhance visibility depending on particular body parts in need of imaging.

If needed, a saline solution will be injected through an arm or hand IV drip, which causes a cool sensation at the injection site. You will hear loud tapping or thumping noises during the procedure as part of the imaging process. You will be able to communicate with the technologist any time during the procedure even though the technologist must leave the room for the duration of the process.

DO Read the general instructions on our home page. Wear comfortable clothing that does not contain metal or zippers. For abdominal studies, please abstain from eating or drinking four hours prior to exam.