• 센서학회지
• /
• 제26권4호
• /
• pp.245-250
• /
• 2017

A novel method to implement a birdcage-type receiving coil sensor for use in a magnetic resonance imaging(MRI) system has been demonstrated employing a flexible printed circuit board (FPCB) fabrication technique. Unlike the conventional methods, the two-dimensional shape of the coil sensor is first implemented as a FPCB and then it is attached to the surface of a cylindrical supporting structure to implement the three-dimensional birdcage-type coil sensor. The proposed method is very effective to implement object-specific MRI coil sensors especially for small animal measurements in research and preclinical applications since the existing well-developed FPCB-based techniques can easily meet the requirements on accuracies and costs during coil implement process. The performances of the coil sensor verified through $^1H$ 1.5T MRI measurements for small animals and it showed excellent characteristics by providing a high spatial precision and a high signal-to-noise ratio.

• 한국의학물리학회지:의학물리
• /
• 제13권2호
• /
• pp.85-89
• /
• 2002

목적 : 사람에 비하여 크기가 현저히 작은 동물의 자기공명영상 촬영을 위하여 상용으로 인체에 적용하는 Head 코일보다 원통 반지름이 작은 Low-Pass Type Birdcage 코일을 제작함으로써 보다 큰 신호대잡음비 (Signal-to-Noise Ratio. SNR)를 얻고자 하였다. 방법 : 자기공명영상을 얻기 위해 Spin Echo 펄스시퀀스와 Fast Spin Echo 펄스시퀀스를 사용하였다. T1 강조영상을 얻기 위한 Spin Echo 펄스시퀀스의 매개변수는 TR/TE=300/17 ㎳, Matrix=256$\times$256, Field Of View (FOV)=150 mm, Slice Thickness=2 mm 이었다. T2 강조영상을 얻기 위한 Fast Spin Echo 펄스시퀀스의 매개변수는 TR/TE=3000/96 ㎳, Matrix=256$\times$256, Field Of View (FOV)=150 mm, Slice Thickness=2 mm 이었다. 원통의 지름이 13 cm인 Birdcage 코일은 12개의 elements로 구성되어 있으며 길이는 22 cm로 제작되었다. 결과 : 코일 원통의 반지름의 크기에 따른 SNR을 비교하기 위하여 인체용 Knee 코일과 동물용으로 제작된 코일을 이용하여 각각의 팬톰 영상을 획득하였다. 팬톰 영상으로부터 측정된 SNR의 값을 통해 반지름이 작은 동물용 코일의 SNR이 더 크다는 걸 확인할 수 있었다. 토의 및 결론 : 본 연구를 통하여 같은 형태의 Birdcage 코일일 경우 원통의 반지름에 따라 SNR이 다르며, 특히 반지름이 작을 때 SNR이 더 크다는 것을 알 수 있었다. 따라서 코일의 크기에 비해 촬영하고자 하는 대상물의 부피가 작은 경우 대상물의 부피에 맞추어 코일을 제작하면 SNR이 보다 뛰어난 영상을 얻을 수 있을 것으로 사료된다.

• 한국전자파학회논문지
• /
• 제11권6호
• /
• pp.976-983
• /
• 2000

본 논문은 MRI용 RF 코일로 널리 사용되고 있는 Birdcage type의 RF 코일을 FDTD 방법을 이용해서 해석, 설계하였다. 기존의 저자장(1T, 1.5T) MRI용 RF 코일의 해석 방법은 코일의 공진 주파수를 얻기 위해서 LC 등가 회로를 사용하였으며 코일 내부의 필드 분포를 얻기 위하여 Biot-Savart 법칙을 이용한 방법이 널리 사용되어 왔다. 그러나 3T이상의 고주파에서 동작하는 RF 코일의 해석에는 위의 방법이 커다란 오차를 일으킬 수 있다. 따라서 본 논문에서는 고주파 해석이 가능한 전파 (Full Wave) 해석 방법인 FDTD 방법을 이용하여 3T MRI용 RF 코일을 해석하고 설계하였다. 또한 FDTD 방법을 이용하여 본 논문에서 실제 제작된 Birdcage type과 Spiral type RF 코일에 적용하여 이 방법의 타당성을 실험적으로 검증하였으며 Spiral type의 RF 코일이 B1 field 균일도면에서 Highpass Birdcage type보다 우수함을 수치 해석적으로 검증하였다.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.363-364
• /
• 2002

We describe quadrature type surface coil for functional magnetic resonance imaging at 3T MRI system. The coil consisted of two coplanar resonators and was used as both transmitter and receiver. The signal-to-noise ratio (SNR) of the coil was compared with that of a standard birdcage head coil. Visual cortex activation on normal subjects using LED flicker was performed. The SNR of surface coil was found to be better than that of the conventional head coil.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1997년도 추계학술대회
• /
• pp.291-293
• /
• 1997

A new quadrature RF coil is designed for Breast MR Imaging. Quadrature RF coils for MRI have been useful to improve the signal-to-noise ratio (SNR) by "$\sqrt{2}$" using two orthogonal RF coils in combination. A modified Breast Quadrature coil is designed. It is a modified type of the high-pass birdcage coil. To reduce the field distortion, by using current feeding, the field pattern is optimized to achieve a quadrature circularly-polarized field pattern. The coil has been implemented for receive-only mode, and tested by phantom imaging. The experimental results show the utility of the proposed RF coil.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1996년도 추계학술대회
• /
• pp.161-164
• /
• 1996

An actively-shielded $r^{2}$-gradient coil has been developed for brain localized MRI or MRS. Spatial localization is very useful for spatial volume selection in MRI or MR Spectroscopy(MRS). The radial(or $R^{2}-$) gradient coil is useful in reducing the artifact or in improving the SNR by selecting the volume with less number of RF pulses. It is, however, difficult to implement the coil with a gradient intensity strong enough to use it for practical whole-body MRI system. For example, the smallest volume size for selection is just 6 cm in diameter with a 250 Ampere of current driving for a whole-body system (in case of 70-cm-diameter). In this study, an asymetric $r^{2}$-coil with a small diameter of 35 cm has been designed and implemented for brain localized MRI or MRS. An 8-rod high-pass-type birdcage RF coil has also been implemented. The coil set has been developed for 1.0 Tesla Medison MRI system and its performance has been verified experimentally.

• 대한자기공명의과학회:학술대회논문집
• /
• 대한자기공명의과학회 2001년도 제6차 학술대회 초록집
• /
• pp.137-137
• /
• 2001

Purpose： The purpose of this study was to identify cerebral cortices related with sexual arousal fro visual sexual stimulation in healthy males using BOLD-based functional MR imaging Method： Sixteen male volunteers with sexually potent(mean age：24) were examined for thi study. Functional MRI was performed on a 1.5T MR scanner(GE Signa Horizon) with birdcage-type head coil. In this study, blood oxygenation level dependent(BOLD) technique was utilized to create fMR image reflecting local brain activities. The BOLD-based fMRI d were obtained from 7 oblique planes using gradient-echo EPI with $90^{\circ}$flip angle, 50ms TE 6000ms TR, $26cm{\times}26$ cm FOV, $128{\times}128$ matrix, and 10mm slice thickness. The sexual stimulation paradigm consisted of two alternating periods of rest and activati and it began with a 1 minute rest, followed by a 2 minute stimulation by a documentary a erotic video film. Brain activation maps were generated by cross-correlation of imag acquired during rest and activation periods. The index of activation was used to compare t number of pixels activated by each task in each volunteer, where the significance of th differences was evaluated by using Students t-test.