• Title, Summary, Keyword: MRI Compensator

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Pumping-up Current Characteristics of Linear Type Magnetic Flux Pump

  • Chung, Yoondo;Muta, Itsuya;Hoshino, Tsutomu;Nakamura, Taketsune;Ko, Taekuk
    • Progress in Superconductivity and Cryogenics
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    • v.6 no.2
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    • pp.29-34
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    • 2004
  • The linear type flux pump aims to compensate a little bit decremental persistent current of the HTS magnet in NMR and MRI spectrometers. The flux pump mainly consists of DC bias coil, 3-phase AC coil and Nb foil. The persistent current in closed superconductive circuit can be easily adjusted by the 3-phase AC current, its frequency and the DC bias current. In the experiment, it has been investigated that the flux pump can effectively charge the current in the load coil of 543 mH for various frequencies in 18 minutes under the DC bias of 10 A and the AC of 5 $A_{rms}$. The maximum magnitudes of pumping current and load magnet voltage are 0.72 A/min and 20 ㎷, respectively. Based on simulation results by the FEM are proved to nearly agree with experimental ones.

A Study on Indirect Attachment Method of Compensation Materials to Increase Signal Intensity in Magnetic Resonance Imaging (자기공명영상검사 시 신호강도를 높이기 위한 보상물질의 간접부착 방식에 관한 연구)

  • Son, Soon-Yong
    • The Journal of the Korea Contents Association
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    • v.17 no.7
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    • pp.437-442
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    • 2017
  • Previously, studies on compensation material to increase the signal intensity have been conducted which does not affect the reading of images. However, the compensation material has a concern on patient infection as it is attached directly on the skin. Therefore, in this study, we tested an indirect attachment of the compensation material as an alternative method of the direct attachment. The silicon compensation material was fabricated in the form of a cylindrical bar and attached to each element of the 8 channel head coil. Then the signal intensities of the water phantom pre and post application of the silicon were measured. T1 and T2-weighted images were acquired using an 8-channel head coil and a 3.0T superconducting MRI. Signal intensities were measured by using an image measuring program. Paired t-test was used to verify if there were significant differences. The signal intensity before application of the silicon was significantly increased by 3.39% and 2.62% in T1 and T2 weighted images, respectively. Although the indirect attachment method had a limitation to completely replace the existing method, it was considered to be useful in patients with infectious diseases such as diabetic complications since it had a meaningful improvement in signal intensity based on the filling factor increase.

Usefulness of Prone Position on PET-CT in Breast Cancer (유방암 PET-CT 검사에서 Prone(복와위)자세의 유용성 평가)

  • Park, Hoon-Hee;Kim, Sei-Yung;Kim, Jung-Yul;Park, Min-Soo;Lim, Han-Snag;Jung, Suk;Kang, Chun-Goo;Kim, Jae-Sam;Lee, Chang-Ho;Lee, Yung-Joo
    • The Korean Journal of Nuclear Medicine Technology
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    • v.12 no.1
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    • pp.44-48
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    • 2008
  • Purpose: In FDG-PET/CT of breast cancer, a sensitivity was 80~96% and a specificity was 75~95% commonly. It was valuable to identify a cancer in early stage been difficult in Mammography. Most of the PET/CT scans have been examined on supine position, so, the image of breast has been acquired by reconstructed whole body scan image. However, using prone position with a compensator, a shape of breast was reassembly shown to be real by gravity. Therefore, the purpose of this study was to evaluate diagnostic value of prone position in FDG PET-CT of breast cancer. Materials and Methods: 30 female patients with doubtful or positive breast cancer were examined. The PET-CT whole body scan was acquired at 60 minutes after $^{18}F$-FDG injection on Supine position. Then, regional breast spot scan was progressed on prone position using a compensator. Each image was evaluated by physicians blinded to patient's data, and statistical analysis did through SUVs measured in PET-CT images. Results: In 27 of 30 patients, prone position was shown accurate discrimination and diagnostic value, but in another 3 patients had a lesion 1cm below, PET-CT couldn't detect it, unlike MRI. Consequently, prone position distinguished a lesion better than Supine position, because of low degree of metamorphosis by gravity. The SUVs analysis of each position was significant (p value=0.004). Conclusion: In PET-CT of breast cancer, prone position could detect micrometastasis as well as primary lesion, better than supine position. Therefore, this study proposes that any technical change considered morphological feature like prone position can offer adequate and useful diagnostic information, together with complementary quantitative analysis.

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