Electromagnetic computation and modeling in <scp>MRI</scp>

Chen, Xin; Steckner, Michael

doi:10.1002/mp.12103

Cited by 12 publications

(8 citation statements)

References 183 publications

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“…Insertion of orthodontic appliances can impact on the oral environment by altering periodontal parameters [30], and tissue responses can also be affected by oral environment composition such as periodontitis [31], which might have a potential impact on results. Furthermore, a plethora of other factors such as diet and T1-weighted morphologic images display the relaxation of the nuclear spins, the alignment of which is affected by the magnetic field [32][33][34], indicating a higher accumulation of the contrast agent in the orthodontically-treated side of the jaw compared to the untreated side. Analysis of dynamic-contrast-enhanced MRI revealed no changes in AUC (area under the curve) and PE (peak enhancement) but reduced TTP (time to peak) and washout rate at the orthodontically-treated side compared to the control side, indicating an altered perfusion at the tension side of the periodontal ligament after four days of orthodontic treatment.…”

Section: Discussionmentioning

confidence: 99%

Local Vascularization during Orthodontic Tooth Movement in a Split Mouth Rat Model—A MRI Study

et al. 2020

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Orthodontic tooth movement to therapeutically align malpositioned teeth is supposed to impact blood flow in the surrounding tissues. Here, we evaluated actual vascularization in the tension area of the periodontal ligament during experimental tooth movement in rats (N = 8) with magnetic resonance imaging (MRI). We inserted an elastic band between the left upper first and the second rat molar; the right side was not treated and served as control. After four days of tooth movement, we recorded T1-weighted morphologic and dynamic-contrast-enhanced MRI sequences with an animal-specific 7 Tesla MRI to assess of local vascularization. Furthermore, we quantified osteoclasts and monocytes in the periodontal ligament, which are crucial for orthodontic tooth movement, root resorptions as undesirable side effects, as well as the extent of tooth movement using paraffine histology and micro-CT analysis. Data were tested for normal distribution with Shapiro–Wilk tests followed by either a two-tailed paired t-test or a Wilcoxon matched-pairs signed rank test. Significant orthodontic tooth movement was induced within the four days of treatment, as evidenced by increased osteoclast and monocyte activity in the periodontal ligament as well as by µCT analysis. Contrast enhancement was increased at the orthodontically-treated side distally of the moved upper first left molar, indicating increased vascularization at the tension side of the periodontal ligament. Accordingly, we detected reduced time-to-peak and washout rates. Our study using MRI to directly assess local vascularization thus seems to confirm the hypothesis that perfusion is enhanced in tension zones of the periodontal ligament during orthodontic tooth movement.

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Section: Discussionmentioning

confidence: 99%

Local Vascularization during Orthodontic Tooth Movement in a Split Mouth Rat Model—A MRI Study

et al. 2020

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“…Two more common types of CEM methods to perform RF coil design simulations are integral-equation solvers and differential-equation solvers (26). The preferred algorithm used for integral-equation solvers is the method of moments and the multilevel fast multipole method.…”

Section: Electromagnetic Modeling Methodsmentioning

confidence: 99%

A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging

Hernández

Kim

2020

Investig Magn Reson Imaging

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Radiofrequency (RF) coils are a vital part of magnetic resonance imaging (MRI). It is through RF coils that a magnetic flux (|B 1 |)-field is transmitted to the imaging object to excite protons, which, in turn, emit RF signals, which are then captured by the RF coils (1). The main function of the RF coils is to transmit (Tx) and receive (Rx) signals. When the imaging object is exposed to a strong magnetic (|B 0 |)-field of the MRI scanner, its spins are magnetized, aligning them with the |B 0 |-field. Consequently, a perpendicular magnetic field is excited using an RF Tx coil, and the RF magnetic pulse deviates the spins vector from the aligned direction of |B 0 |-field. The stronger the RF

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“…Already used to predict the mechanism of action for novel 10 kHz frequencies in deep brain stimulation (DBS) in generating moderate localized tissue heating, it may serve a role in creating new MR-safe electrodes and stimulation systems for dorsal column spinal cord stimulation as it has for DBS [9]. Electromagnetic (EM) modeling is a readily available technique utilized to predict how implanted medical devices interact with the MRI EM fields, and it is conceivable that this modality can be used to help develop novel device components that do not increase impedance over time to mitigate this issue [29].…”

Section: Postural Changesmentioning

confidence: 99%

Failure of SCS MR-Conditional Modes Due to High Impedance: A Review of Literature and Case Series

et al. 2020

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Introduction: Magnetic resonance imaging (MRI) conditional modes are a novel feature for certain Food and Drug Administration (FDA)approved spinal cord stimulation (SCS) devices. However, there is a paucity of literature around the limitation of MRI-conditional modes (''MRI safe''), specifically in clinical scenarios where urgent MRIs may be needed. One such limitation is load impedance, referring to the circuit's resistance to the current being generated by the system. High impedance can limit the MRIconditional mode capability, presenting potential harm to a patient undergoing an MRI or make an MRI unable to be completed. Methods: Three cases were identified, and informed consent was obtained. All information was obtained via retrospective chart review. Results: In this case series of three patients where MRI-conditional SCS systems were unable to be placed in ''MRI safe'' settings, preventing timely MRI study completion in the setting of high impedance, all three were required to undergo alternative imaging including CT scans, and two patients ultimately had the system explanted and one chose to be re-implanted after completion of scans. Conclusion: This case series highlights the need for further investigation of impedance in SCS systems and potential limitations for future MRI usage. The review of literature of impedance in SCS shows both device-and physiologic-related etiologies for changes in impedance that warrant consideration by the implanting physician.

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Electromagnetic computation and modeling in MRI

Cited by 12 publications

References 183 publications

Local Vascularization during Orthodontic Tooth Movement in a Split Mouth Rat Model—A MRI Study

Local Vascularization during Orthodontic Tooth Movement in a Split Mouth Rat Model—A MRI Study

A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging

Failure of SCS MR-Conditional Modes Due to High Impedance: A Review of Literature and Case Series

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