The phase information of magnetic resonance (MR) phase image can be used in many MR imaging techniques, but phase wrapping of the images often results in inaccurate phase information and phase unwrapping is essential for MR imaging techniques. In this paper we analyze the causes of errors in phase unwrapping with the commonly used Goldstein Brunch-cut algorithm and propose an improved algorithm. During the unwrapping process, masking, filtering, dipole- remover preprocessor, and the Prim algorithm of the minimum spanning tree were introduced to optimize the residues essential for the Goldstein Brunch-cut algorithm. Experimental results showed that the residues, branch-cuts and continuous unwrapped phase surface were efficiently reduced and the quality of MR phase images was obviously improved with the proposed method.
Algorithms ; Magnetic Resonance Imaging ; methods

The required time of conventional magnetic resonance spectroscopic imaging technique is too long to be applied to clinic. It is necessary to develop the fast methods for magnetic resonance spectroscopic imaging. Nowadays there are 7 kinds of methods presented, which come from MRI techniques. In this contribution the conventional spectroscopic imaging and 7 sorts of fast spectroscopic imaging are elaborated. It is envisaged that more rapid imaging techniques will be designed, if these arbitrary trajectory reconstruction methods in MRI are applied to spectroscopic imaging.
Magnetic Resonance Imaging ; methods ; trends ; Magnetic Resonance Spectroscopy ; methods

Magnetic Particle Imaging (MPI) is a new medical imaging tool, which was born at the beginning of the 21st century. Compared with traditional imaging techniques, the preliminary research indicates that MPI shows higher sensitivity, resolution and imaging speed. This article presents the principle of MPI, its recent development from three different perspectives is introduced.
Diagnostic Imaging ; Magnetic Phenomena ; Magnetic Resonance Imaging ; methods ; Molecular Imaging

The paper introduces a method of self-gated signal's collection based on TrueFisp sequence, during self-gated cardiac magnetic resonance imaging. There is no significant difference in its image quality and only a slight loss in efficiency in comparison with MRI images by ECG-based triggering.
Electrocardiography ; methods ; Magnetic Resonance Imaging ; methods

The accurate diagnosis and staging of hepatic fibrosis is crucial for treatment and prognosis of liver disease. The current gold standard is liver biopsy, but it cannot be used in population-based screening, and has well known drawbacks if used for monitoring of disease progression or treatment results. Functional MR, as a non-invasive method, is increasingly used in hepatic fibrosis and became the current hot spot. Most recently available functional MR imaging techniques including diffusion weighted imaging, perfusion weighted imaging and MR spectroscopy can detect cirrhosis or fibrosis reasonably accurately. However, to date only MR elastography has been able to stage fibrosis or diagnose mild disease. MR diffusion weighted appears next most promising.
Diffusion Magnetic Resonance Imaging ; Humans ; Liver Cirrhosis ; classification ; diagnosis ; Magnetic Resonance Imaging ; methods ; Magnetic Resonance Spectroscopy

Grounding technique is very important to ensure the human safety, imaging devices' safety and the devices' reliable running. This paper expatriates the principles of the grounding safety, interference rejection earth, and the grounding modes and the mode selection for each imaging devices and equipments, and related grounding requirements.
Equipment Safety ; methods ; Magnetic Resonance Imaging ; instrumentation

Calculation methods of coil sensitivity in parallel MRI were elaborated, compared and analyzed.
Algorithms ; Magnetic Resonance Imaging ; instrumentation ; methods

This study examined the effect of different b values on diffusion-weighted MR imaging (DWI) of human prostate by using single-shot spin echo echo planar imaging (SE-EPI) sequences, observed the normal appearances and measured apparent diffusion coefficient (ADC) values in anatomical regions of normal prostate. Twenty-four healthy volunteers (mean age: 32 y) were studied by using a 1.5T system with a phased array surface multicoil. Two kinds of single-shot SE-EPI sequence were used to perform DWI in the prostate in volunteers, with five b values being 0, 30, 300, 500 to 1000 s/mm(2). The image quality with different imaging parameters was analyzed and the ADC values in anatomical regions of normal prostate were measured. DWI of prostate was successfully obtained in all volunteers. The images were of good quality, without artifacts containing pixels within the prostate. The contrast was good between the different anatomical regions of the prostatic gland, i.e., the peripheral zone (PZ), which exhibited higher signal intensity, and the central gland (CG). Signal intensity contrast was related to the magnitude of b values. The ADC values in PZ and CG were (1.27+/-0.22)x10(-3) mm(2)/s and (1.01+/-0.17)x10(-3) mm(2)/s, respectively. The ADC values were found to be significantly higher in PZ than in CG (P<0.05, paired t-test). Significant differences were found between the slice-selecting component and both the read-out and phase-encoding components of the ADC values. It is concluded that SE-EPI is a suitable DWI sequence for human prostate. The contrast between PZ and CG is good when b values are low, while the diffusion and ADC values are accurate when b values are high. ADC values are higher in PZ than in CG in normal prostate. Diffusional anisotropy is present in normal prostatic tissue.
Magnetic Resonance Imaging/*methods ; Prostate/*anatomy & histology

During magnetic resonance imaging, motion and flow artifacts often severely decrease image quality. The mechanisms of these kinds of artifacts are very complex. This article reviewed the pre-handling techniques of motion and flow artifacts, such as changing magnetic resonance imaging parameters, using spatial pre-saturation pulse sequences, gating and triggering techniques of suppressing respiratory motion artifact, as well as the progress of magnetic resonance pulse sequences in suppressing motion and flow artifacts, The paper briefly introduced post-processing techniques of suppressing motion and flow artifacts.
Artifacts ; Magnetic Resonance Imaging ; methods ; Motion

A mechanical shimming method and device for permanent magnet of MRI system has been developed to meet its stringent homogeneity requirement without time-consuming passive shimming on site, installation and adjustment efficiency has been increased.
Magnetic Resonance Imaging ; instrumentation ; methods ; Magnets