PURPOSE: B1 field of birdcage RF (radiofrequency) coil that is used most for brain imaging in magnetic resonance imaging (MRI) decreases toward endring from the coil center. We investigated how much RF B1 homogeneity effect the endcap shield brings form the coil center as it towards to endcap region. MATERIALS AND METHODS: We compared RF B1 field distribution by each finite difference time domain (FDTD) simulations for lowpass, highpass and hybrid birdcage RF coils. We selected the highpass birdcage RF coil that was the highest RF B1 field condition as simulation result, and studied how much RF B1 homogeneity effect was occurred when endcap shield was applied to endring area. RESULTS: B1 field of the highpass birdcage RF coil was higher than other birdcage RF coil types as simulation result. However, the RF B1 homogeneity was lower than other coil types. RF B1 field of highpass birdcage RF coil with endcap shield is similar with RF B1 field of hybrid birdcage RF coil and the overall RF B1 homogeneity in sagittal direction was better. CONCLUSION: In this paper, proposed method can apply improving RF B1 homogeneity of RF coil in clinical examination.
Magnetic Resonance Imaging* ; Neuroimaging

No abstract available.
Magnetic Resonance Imaging* ; Relaxation*

No abstract available.
Breast* ; Magnetic Resonance Imaging*

Many different forms of the neurosurgical robots have been suggested for stereotactic surgery. Recently, their position accuracies exceed the ones of the conventional stereotactic devices and their assisting role for the surgeon are helpful by reducing the procedure and the operation time. Recent advancements of the position and image sensing technologies such as CT, MRI, dynamic position tracking sensing, etc., encourages the devotion of researchers to put more effort to treat the uncertainties such as brain shift, unexpected brain movements etc. In this trend, the more adequate, efficient, cost-effective structure of the surgical robot needs to be investigated. Thus, in this paper, the structure of the typical neurosurgical surgical robot and their position accuracies are reviewed and the desirable design aspects are addressed.
Brain ; Magnetic Resonance Imaging

Many different forms of the neurosurgical robots have been suggested for stereotactic surgery. Recently, their position accuracies exceed the ones of the conventional stereotactic devices and their assisting role for the surgeon are helpful by reducing the procedure and the operation time. Recent advancements of the position and image sensing technologies such as CT, MRI, dynamic position tracking sensing, etc., encourages the devotion of researchers to put more effort to treat the uncertainties such as brain shift, unexpected brain movements etc. In this trend, the more adequate, efficient, cost-effective structure of the surgical robot needs to be investigated. Thus, in this paper, the structure of the typical neurosurgical surgical robot and their position accuracies are reviewed and the desirable design aspects are addressed.
Brain ; Magnetic Resonance Imaging

No abstract available.
Hippocampus* ; Magnetic Resonance Imaging*

No abstract available.
Hippocampus* ; Magnetic Resonance Imaging*

PURPOSE: A new compressed sensing technique by iterative truncation of small transformed coefficients (ITSC) is proposed for fast cardiac CINE MRI. MATERIALS AND METHODS: The proposed reconstruction is composed of two processes: truncation of the small transformed coefficients in the r-f domain, and restoration of the measured data in the k-t domain. The two processes are sequentially applied iteratively until the reconstructed images converge, with the assumption that the cardiac CINE images are inherently sparse in the r-f domain. A novel sampling strategy to reduce the normalized mean square error of the reconstructed images is proposed. RESULTS: The technique shows the least normalized mean square error among the four methods under comparison (zero filling, view sharing, k-t FOCUSS, and ITSC). Application of ITSC for multi-slice cardiac CINE imaging was tested with the number of slices of 2 to 8 in a single breath-hold, to demonstrate the clinical usefulness of the technique. CONCLUSIONS: Reconstructed images with the compression factors of 3-4 appear very close to the images without compression. Furthermore the proposed algorithm is computationally efficient and is stable without using matrix inversion during the reconstruction.
Magnetic Resonance Imaging, Cine*

No abstract available.
Hemangioma* ; Magnetic Resonance Imaging*

No abstract available.
Hematoma* ; Magnetic Resonance Imaging*