Multi-channel hexagonal surface coils for 1.5T MRI scanner

Eighteen consecutive patients with spinal cord symptoms of sudden or relatively sudden onset were examined with magnetic resonance imaging (MRI). The examinations were performed on a 0.3 tesla permanent/resistive imaging system using solenoidal surface coils. MRI revealed epidural tumour in five patients, intramedullary tumour in one, epidural abscess in one, myelitis in two, spontaneous intraspinal epidural haematoma in two, disc herniation in two, traumatic lesions in four and no abnormality in one patient. MRI was found to be capable of non-invasively and painlessly detecting and exactly defining the extent of intraspinal and paraspinal lesions. In some cases the nature of the lesion could be inferred from specific signal characteristics, which is a unique property of MRI. The results strongly suggest that MRI is superior to myelography and other imaging methods and should be regarded as the examination of choice in the emergency examination of patients with spinal cord symptoms.

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Design of microstrip-based surface coils for low-field small-bore MR applications

Concepts in Magnetic Resonance Part B Magnetic Resonance Engineering ◽

10.1002/cmr.b.21219 ◽

2012 ◽

Vol 41B (4) ◽

pp. 111-119 ◽

Cited By ~ 2

Author(s):

Youngseob Seo

Keyword(s):

Surface Coils ◽

Low Field

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Now you see it, now you don't: optimal parameters for interslice stimulation in concurrent TMS-fMRI

10.1101/2021.05.28.446111 ◽

2021 ◽

Author(s):

Catriona L Scrivener ◽

Jade B Jackson ◽

Marta Morgado Correia ◽

Marius Mada ◽

Alexandra Woolgar

Keyword(s):

Single Channel ◽

Signal To Noise Ratio ◽

Brain Activity ◽

Surface Coil ◽

Acquisition Time ◽

Surface Coils ◽

Human Participant ◽

Set Up ◽

Promising Avenue ◽

Slice Acquisition

The powerful combination of transcranial magnetic stimulation (TMS) concurrent with functional magnetic resonance imaging (fMRI) provides rare insights into the causal relationships between brain activity and behaviour. Despite a recent resurgence in popularity, TMS-fMRI remains technically challenging. Here we examined the feasibility of applying TMS during short gaps between fMRI slices to avoid incurring artefacts in the fMRI data. We quantified signal dropout and changes in temporal signal-to-noise ratio (tSNR) for TMS pulses presented at timepoints from 100ms before to 100ms after slice onset. Up to 3 pulses were delivered per volume using MagVenture's MR-compatible TMS coil. We used a spherical phantom, two 7-channel TMS-dedicated surface coils, and a multiband (MB) sequence (factor=2) with interslice gaps of 100ms and 40ms, on a Siemens 3T Prisma-fit scanner. For comparison we repeated a subset of parameters with a more standard single-channel TxRx (birdcage) coil, and with a human participant and surface coil set up. We found that, even at 100% stimulator output, pulses applied at least -40ms/+50ms from the onset of slice readout avoid incurring artifacts. This was the case for all three setups. Thus, an interslice protocol can be achieved with a frequency of up to ~10 Hz, using a standard EPI sequence (slice acquisition time: 62.5ms, interslice gap: 40ms). Faster stimulation frequencies would require shorter slice acquisition times, for example using in-plane acceleration. Interslice TMS-fMRI protocols provide a promising avenue for retaining flexible timing of stimulus delivery without incurring TMS artifacts.

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Volume and surface coil simultaneous reception (VSSR) method for intensity inhomogeneity correction in MRI

Technology and Health Care ◽

10.3233/thc-213149 ◽

2021 ◽

pp. 1-12

Author(s):

Lin Wu ◽

Tian He ◽

Jie Yu ◽

Hang Liu ◽

Shuang Zhang ◽

...

Keyword(s):

Bias Field ◽

Correction Method ◽

Surface Coil ◽

Intensity Inhomogeneity ◽

Acquisition Time ◽

Surface Coils ◽

In Vivo Experiments ◽

Inhomogeneity Correction ◽

Volume Coil

BACKGROUND: Addressing intensity inhomogeneity is critical in magnetic resonance imaging (MRI) because associated errors can adversely affect post-processing and quantitative analysis of images (i.e., segmentation, registration, etc.), as well as the accuracy of clinical diagnosis. Although several prior methods have been proposed to eliminate or correct intensity inhomogeneity, some significant disadvantages have remained, including alteration of tissue contrast, poor reliability and robustness of algorithms, and prolonged acquisition time. OBJECTIVE: In this study, we propose an intensity inhomogeneity correction method based on volume and surface coils simultaneous reception (VSSR). METHODS: The VSSR method comprises of two major steps: 1) simultaneous image acquisition from both volume and surface coils and 2) denoising of volume coil images and polynomial surface fitting of bias field. Extensive in vivo experiments were performed considering various anatomical structures, acquisition sequences, imaging resolutions, and orientations. In terms of correction performance, the proposed VSSR method was comparatively evaluated against several popular methods, including multiplicative intrinsic component optimization and improved nonparametric nonuniform intensity normalization bias correction methods. RESULTS: Experimental results show that VSSR is more robust and reliable and does not require prolonged acquisition time with the volume coil. CONCLUSION: The VSSR may be considered suitable for general implementation.

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