• Title/Summary/Keyword: Spin Echo Train

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An Improved Spin Echo Train De-noising Algorithm in NMRL

  • Liu, Feng;Ma, Shuangbao
    • Journal of Information Processing Systems
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    • v.14 no.4
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    • pp.941-947
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    • 2018
  • Since the amplitudes of spin echo train in nuclear magnetic resonance logging (NMRL) are small and the signal to noise ratio (SNR) is also very low, this paper puts forward an improved de-noising algorithm based on wavelet transformation. The steps of this improved algorithm are designed and realized based on the characteristics of spin echo train in NMRL. To test this improved de-noising algorithm, a 32 points forward model of big porosity is build, the signal of spin echo sequence with adjustable SNR are generated by this forward model in an experiment, then the median filtering, wavelet hard threshold de-noising, wavelet soft threshold de-noising and the improved de-noising algorithm are compared to de-noising these signals, the filtering effects of these four algorithms are analyzed while the SNR and the root mean square error (RMSE) are also calculated out. The results of this experiment show that the improved de-noising algorithm can improve SNR from 10 to 27.57, which is very useful to enhance signal and de-nosing noise for spin echo train in NMRL.

A New Technique or Dual $T_E$ Images Acquisition in Fast Spin Echo MR Imaging (고속 Spin Echo 자기 공명 영상법에서 두 가지 $T_E$ 영상을 얻기 위한 새로운 방법)

  • Cho, M.H.;Lee, S.Y.;Mun, C.W.;Cho, H.H.;Yi, W.
    • Proceedings of the KOSOMBE Conference
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    • v.1997 no.11
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    • pp.294-298
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    • 1997
  • In the magnetic resonance imaging, the fast spin echo imaging technique is a widely used clinical imaging method, since its scanning time is much shorter than the conventional spin echo imaging and it gives the almost same image quality. However, the fast spin echo technique has two times longer imaging time or the dual echo acquisition which can obtain a spin density image and a $T_2$-weighted image simultaneously. To overcome such a drawback, this paper proposes a new fast dual echo imaging technique which can give the same quality images at the single echo imaging time. The proposed technique reduces the imaging time by overlapping most of echo train data for each image reconstruction. In order to verify its validity and usability the human head experimental results which were obtained at the 0.3T permanent MRI system are presented.

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Multi-slice Multi-echo Pulsed-gradient Spin-echo (MePGSE) Sequence for Diffusion Tensor Imaging MRI: A Preliminary Result (일회 영상으로 확산텐서 자기공명영상을 얻을 수 있는 다편-다에코 펄스 경사자장 스핀에코(MePGSE) 시퀀스의 초기 결과)

  • Jahng, Geon-Ho;Pickup, Stephen
    • Progress in Medical Physics
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    • v.18 no.2
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    • pp.65-72
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    • 2007
  • An echo planar imaging (EPI)-based spin-echo sequence Is often used to obtain diffusion tensor imaging (DTI) data on most of the clinical MRI systems, However, this sequence is confounded with the susceptibility artifacts, especially on the temporal lobe in the human brain. Therefore, the objective of this study was to design a pulse sequence that relatively immunizes the susceptibility artifacts, but can map diffusion tensor components in a single-shot mode. A multi-slice multi-echo pulsed-gradient spin-echo (MePGSE) sequence with eight echoes wasdeveloped with selective refocusing pulses for all slices to map the full tensor. The first seven echoes in the train were diffusion-weighted allowing for the observation of diffusion in several different directions in a single experiment and the last echo was for crusher of the residual magnetization. All components of diffusion tensor were measured by a single shot experiment. The sequence was applied in diffusive phantoms. The preliminary experimental verification of the sequence was illustrated by measuring the apparent diffusion coefficient (ADC) for tap water and by measuring diffusion tensor components for watermelon. The ADC values in the series of the water phantom were reliable. The MePGSE sequence, therefore, may be useful in human brain studies.

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High Resolution 3D Magnetic Resonance Fingerprinting with Hybrid Radial-Interleaved EPI Acquisition for Knee Cartilage T1, T2 Mapping

  • Han, Dongyeob;Hong, Taehwa;Lee, Yonghan;Kim, Dong-Hyun
    • Investigative Magnetic Resonance Imaging
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    • v.25 no.3
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    • pp.141-155
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    • 2021
  • Purpose: To develop a 3D magnetic resonance fingerprinting (MRF) method for application in high resolution knee cartilage PD, T1, T2 mapping. Materials and Methods: A novel 3D acquisition trajectory with golden-angle rotating radial in kxy direction and interleaved echo planar imaging (EPI) acquisition in the kz direction was implemented in the MRF framework. A centric order was applied to the interleaved EPI acquisition to reduce Nyquist ghosting artifact due to field inhomogeneity. For the reconstruction, singular value decomposition (SVD) compression method was used to accelerate reconstruction time and conjugate gradient sensitivity-encoding (CG-SENSE) was performed to overcome low SNR of the high resolution data. Phantom experiments were performed to verify the proposed method. In vivo experiments were performed on 6 healthy volunteers and 2 early osteoarthritis (OA) patients. Results: In the phantom experiments, the T1 and T2 values of the proposed method were in good agreement with the spin-echo references. The results from the in vivo scans showed high quality proton density (PD), T1, T2 map with EPI echo train length (NETL = 4), acceleration factor in through plane (Rz = 5), and number of radial spokes (Nspk = 4). In patients, high T2 values (50-60 ms) were seen in all transverse, sagittal, and coronal views and the damaged cartilage regions were in agreement with the hyper-intensity regions shown on conventional turbo spin-echo (TSE) images. Conclusion: The proposed 3D MRF method can acquire high resolution (0.5 mm3) quantitative maps in practical scan time (~ 7 min and 10 sec) with full coverage of the knee (FOV: 160 × 160 × 120 mm3).