Low-Field Whole Body Systems

Kaufman, Léon; Kramer, David; Carlson, Joseph W.; Arakawa, M

doi:10.1002/9780470034590.emrstm0277

Cited by 3 publications

(2 citation statements)

References 18 publications

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“…4,8 It is well recognized that MRI provides lower bone contrast than CT and suffers from spatial distortions which vary by scanner, scan sequence, and the object being scanned. [9][10][11][12][13][14][15][16][17][18] MRI use is limited, for example, in stereotactic surgery of the brain unless geometric distortion correction has been performed. 14,15 Similarly, shape registration-based motion measurement requires submillimeter model accuracy for many clinically relevant measurement scenarios.…”

Section: Introductionmentioning

confidence: 99%

Can magnetic resonance imaging–derived bone models be used for accurate motion measurement with single‐plane three‐dimensional shape registration?

Morooka

Hamai

Miura

et al. 2007

Journal Orthopaedic Research

129

117

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The purpose of this study was to compare three-dimensional (3D) kinematic measurements from single-plane radiographic projections using bone models created from magnetic resonance imaging (MRI) and computed tomography (CT). MRI is attractive because there is no ionizing radiation, but geometric field distortion and poor bone contrast degrade model fidelity compared to CT. We created knee bone models of three healthy volunteers from both MRI and CT and performed three quantitative comparisons. First, differences between MRI-and CT-derived bone model surfaces were measured. Second, shape matching motion measurements were done with bone models for X-ray image sequences of a squat activity. Third, synthetic X-ray images in known poses were created and shape matching was again performed. Differences in kinematic results were quantified in terms of root mean square (RMS) error. Mean differences between CT and MRI model surfaces for the femur and tibia were À0.08 mm and À0.14 mm, respectively. There were significant differences in three of six kinematic parameters comparing matching results from MRI-derived bone models and CT-derived bone models. RMS errors for tibiofemoral poses averaged 0.74 mm for sagittal translations, 2.0 mm for mediolateral translations, and 1.48 for all rotations with MRI models. Average RMS errors were 0.53 mm for sagittal translations, 1.6 mm for mediolateral translations, and 0.548 for all rotations with the CT models. Single-plane X-ray imaging with modelbased shape matching provides kinematic measurements with sufficient accuracy to assess knee motions using either MRI-or CT-derived bone models. However, extra care should be taken when using MRI-derived bone models because model inaccuracies will affect the quality of the shape matching results. ß

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Section: Introductionmentioning

confidence: 99%

Can magnetic resonance imaging–derived bone models be used for accurate motion measurement with single‐plane three‐dimensional shape registration?

Morooka

Hamai

Miura

et al. 2007

Journal Orthopaedic Research

129

117

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“…They permit different configurations such as open-access MRI systems [ 3 – 5 ]; however, they are very bulky and heavy. Resistive magnets produce weaker fields, are less expensive [ 18 ] and exhibit smaller fringe fields than superconducting magnets owing to their low fields of operation. They have over the years sought a share of popularity in the commercial sphere, however, have been disadvantaged on several fronts as discussed in the next section.…”

Section: Introductionmentioning

confidence: 99%

Approaches in cooling of resistive coil-based low-field Magnetic Resonance Imaging (MRI) systems for application in low resource settings

2021

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Magnetic Resonance Imaging (MRI), a non-invasive method for the diagnosis of diverse health conditions has experienced growing popularity over other imaging modalities like ultrasound and Computer Tomography. Initially, proof-of-concept and earlier MRI systems were based on resistive and permanent magnet technology. However, superconducting magnets have long held monopoly of the market for MRI systems with their high-field (HF) strength capability, although they present high construction, installation, and siting requirements. Such stringent prerequisites restrict their availability and use in low-middle income countries. Resistive coil-based magnet, albeit low-field (LF) in capacity, represent a plausible boost for the availability and use of MRI systems in resource constrained settings. These systems are characterized by low costs coupled with substantial image quality for diagnosis of some conditions such as hydrocephalus common is such regions. However, the nature of resistive coils causes them to heat up during operation, thus necessitating a dedicated cooling system to improve image quality and enhance system longevity. This paper explores a range of cooling methods as have been applied to resistive magnets, citing their pros and cons and areas for improvement.

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MRICOM–MRI COntrast Modelling using 2D T1–T2 correlation spectra and relaxation signatures

Wright

Warner

Venturi

et al. 2010

Magnetic Resonance Imaging

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Low-Field Whole Body Systems

Cited by 3 publications

References 18 publications

Can magnetic resonance imaging–derived bone models be used for accurate motion measurement with single‐plane three‐dimensional shape registration?

Can magnetic resonance imaging–derived bone models be used for accurate motion measurement with single‐plane three‐dimensional shape registration?

Approaches in cooling of resistive coil-based low-field Magnetic Resonance Imaging (MRI) systems for application in low resource settings

MRICOM–MRI COntrast Modelling using 2D T1–T2 correlation spectra and relaxation signatures

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