• Title/Summary/Keyword: 자기 이상

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2.5 Dimensional EM Modeling considering Horizontal Magnetic Dipole Source (수평 자기쌍극자 송신원을 이용한 2.5차원 전자탐사 모델링)

  • Kwon Hyoung-Seok;Song Yoonho;Son Jeong-Sul;Suh Jung-Hee
    • Geophysics and Geophysical Exploration
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    • v.5 no.2
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    • pp.84-92
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    • 2002

  • In this study, the new modeling scheme has been developed for recently designed and tested electromagnetic survey, which adapts horizontal magnetic dipole with $1\;kHz\~1\;MHz$ frequency range as a source. The 2.5-D secondary field formulation in wavenumber domain was constructed using finite element method and verified through comparing results with layered-earth solutions calculated by integral equations. 2-D conductive- and resistive-block models were constructed for calculating electric field, magnetic field and impedance - the ratio of electric and magnetic fields which are orthogonal each other. This study showed that electric field and impedance are superior in identifying 2-D isolated-body model to magnetic field. In particular, impedance gives more stable results than electric field with similar spatial resolving power, because electric field is divided by magnetic field in impedance. Thus the impedance analysis which uses electric and magnetic fields together would give better result in imaging the shallow anomalies than conventional EM method.

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Transient Abnormalities on Magnetic Resonance Imaging after Absence Seizures (결신발작 이후 확인된 일시적인 자기공명영상 이상 1예)

  • Yoo, Hye Won;Yoon, Lira;Kim, Hye Young;Kwak, Min Jung;Park, Kyung Hee;Bae, Mi Hye;Lee, Yunjin;Nam, Sang Ook;Kim, Young Mi
    • Journal of the Korean Child Neurology Society
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    • v.26 no.4
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    • pp.280-283
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    • 2018

  • Magnetic resonance imaging (MRI) is recommended for patients with epileptic seizures to rule out an underlying focal lesion. However, abnormalities in idiopathic generalized epilepsy, including childhood absence epilepsy, cannot usually be identified using brain imaging modalities such as MRI. Peri-ictal MRI abnormalities have been most commonly reported secondary to status epilepticus and are rarely observed in patients with focal seizures and generalized tonic-clonic seizures. Transient peri-ictal MRI abnormalities in absence epilepsy are extremely rare. A five-year-old girl presented with a three-day history of absence seizures that persisted despite continued treatment with sodium valproate. Electroencephalography showed bursts of generalized 3-Hz spike-and-wave discharges, during and after hyperventilation. Abnormal cortex thickening in the left perisylvian region was detected on T2-weighted brain MRI, and cortical dysplasia or a tumor was suspected. The patient started treatment with lamotrigine and was seizure-free after one month. The abnormal MRI lesion was completely resolved at the two-month follow-up. We report on a patient with childhood absence epilepsy and reversible brain MRI abnormalities in the perisylvian region. To our knowledge, this is the first report of transient MRI abnormalities after absence seizures. Transient peri-ictal MRI abnormalities should be considered for differential diagnosis in patients with absence seizures and a focal abnormality on brain MRI.

  • https://doi.org/10.26815/jkcns.2018.26.4.280 인용