Whole-body magnetic resonance imaging at 0.05 Tesla

Zhao, Yujiao; Ding, Ye; Lau, Vick; Man, Christopher; Su, Shi; Xiao, Linfang; Leong, Alex T. L.; Wu, Ed X.

doi:10.1126/science.adm7168

Cited by 10 publications

(1 citation statement)

References 84 publications

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“…Compared with other emerging techniques like low-field MRI [37], whole-body UST is faster (~10 seconds per 2D slice) with comparable or finer resolution (~1 mm), and it does not require a shielded room or magnet-compatible environment. Further, it is more portable, more open, and less noisy than MRI.…”

Section: Discussionmentioning

confidence: 99%

Whole-Body Human Ultrasound Tomography

Wang,

Garrett,

et al. 2024

Preprint

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Ultrasonography is a vital component of modern clinical care, with handheld probes routinely used for a variety of applications. However, handheld ultrasound imaging is limited by factors such as the partial-body field of view, operator dependency, contact-induced distortion, and lack of transmission contrast. Here, we demonstrate a new system enabling whole-body ultrasound tomography of humans in reflection and transmission modes. To generate 2D isotropically resolved images across the entire cross-section in vivo, we use a custom 512-element circular ultrasound receiver array with a rotating ultrasonic transmitter. We demonstrate this technique in regions such as the abdomen and legs in healthy volunteers. We also showcase two potential clinical extensions. First, we readily observe subcutaneous and preperitoneal abdominal adipose distributions in our images, enabling adipose thickness assessment over the body without ionizing radiation or mechanical deformation. Second, we demonstrate an approach for rapid (seven frame-per-second) biopsy needle localization with respect to internal tissue features. These capabilities make whole-body ultrasound tomography a potential practical tool for clinical needs currently unmet by other modalities.

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Section: Discussionmentioning

confidence: 99%

Whole-Body Human Ultrasound Tomography

Wang,

Garrett,

et al. 2024

Preprint

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Ultra‐low‐field magnetization transfer imaging at 0.055T with low specific absorption rate

Su,

Zhao,

Ding

et al. 2024

Magnetic Resonance in Med

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PurposeTo demonstrate magnetization transfer (MT) effects with low specific absorption rate (SAR) on ultra‐low‐field (ULF) MRI.MethodsMT imaging was implemented by using sinc‐modulated RF pulse train (SPT) modules to provide bilateral off‐resonance irradiation. They were incorporated into 3D gradient echo (GRE) and fast spin echo (FSE) protocols on a shielding‐free 0.055T head scanner. MT effects were first verified using phantoms. Brain MT imaging was conducted in both healthy subjects and patients.ResultsMT effects were clearly observed in phantoms using six SPT modules with total flip angle 3600° at central primary saturation bands of approximate offset ±786 Hz, even in the presence of large relative B0 inhomogeneity. For brain, strong MT effects were observed in gray matter, white matter, and muscle in 3D GRE and FSE imaging using six and sixteen SPT modules with total flip angle 3600° and 9600°, respectively. Fat, cerebrospinal fluid, and blood exhibited relatively weak MT effects. MT preparation enhanced tissue contrasts in T2‐weighted and FLAIR‐like images, and improved brain lesion delineation. The estimated MT SAR was 0.0024 and 0.0008 W/kg for two protocols, respectively, which is far below the US Food and Drug Administration (FDA) limit of 3.0 W/kg.ConclusionRobust MT effects can be readily obtained at ULF with extremely low SAR, despite poor relative B0 homogeneity in ppm. This unique advantage enables flexible MT pulse design and implementation on low‐cost ULF MRI platforms to achieve strong MT effects in brain and beyond, potentially augmenting their clinical utility in the future.

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Ultra‐low‐field magnetic resonance angiography at 0.05 T: A preliminary study

Su,

Hu,

Ding

et al. 2024

NMR in Biomedicine

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We aim to explore the feasibility of head and neck time‐of‐flight (TOF) magnetic resonance angiography (MRA) at ultra‐low‐field (ULF). TOF MRA was conducted on a highly simplified 0.05 T MRI scanner with no radiofrequency (RF) and magnetic shielding. A flow‐compensated three‐dimensional (3D) gradient echo (GRE) sequence with a tilt‐optimized nonsaturated excitation RF pulse, and a flow‐compensated multislice two‐dimensional (2D) GRE sequence, were implemented for cerebral artery and vein imaging, respectively. For carotid artery and jugular vein imaging, flow‐compensated 2D GRE sequences were utilized with venous and arterial blood presaturation, respectively. MRA was performed on young healthy subjects. Vessel‐to‐background contrast was experimentally observed with strong blood inflow effect and background tissue suppression. The large primary cerebral arteries and veins, carotid arteries, jugular veins, and artery bifurcations could be identified in both raw GRE images and maximum intensity projections. The primary brain and neck arteries were found to be reproducible among multiple examination sessions. These preliminary experimental results demonstrated the possibility of artery TOF MRA on low‐cost 0.05 T scanners for the first time, despite the extremely low MR signal. We expect to improve the quality of ULF TOF MRA in the near future through sequence development and optimization, ongoing advances in ULF hardware and image formation, and the use of vascular T1 contrast agents.

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Whole-body magnetic resonance imaging at 0.05 Tesla

Cited by 10 publications

References 84 publications

Whole-Body Human Ultrasound Tomography

Whole-Body Human Ultrasound Tomography

Ultra‐low‐field magnetization transfer imaging at 0.055T with low specific absorption rate

Ultra‐low‐field magnetic resonance angiography at 0.05 T: A preliminary study

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