Shoichi Kanayama

Nuclear magnetic resonance imaging with high speed and interactive pulse sequence control

A nuclear magnetic resonance imaging capable of controlling a generation of a desired pulse sequence to be used interactively, realizing the adjustment of the pulse sequence easily and accurately, and realizing the high speed pulse sequence execution. The pulse sequence is automatically generated from a basic pulse sequence form and a parameter block storing the imaging parameters affected by the imaging conditions specified interactively. The pulse sequence is then automatically adjusted to an optimum setting by simulating an execution of the pulse sequence by using simulated RF pulses, gradient magnetic fields, static magnetic field, and nuclear spin density distribution, according to the characteristic parameters measured in advance. In the actual execution of the pulse sequence, the event codes stored in the event memory of the sequence controller are decoded by a plurality of decoders in parallel, and the rewriting of the event memory is realized by using a rewriting table having entries specifying a manner of rewriting each slot of each entry in the event memory, and flags in the event memory indicating an appropriate rewriting table entry for each slot.

Method/apparatus for NMR imaging using an imaging scheme sensitive to inhomogeneity and a scheme insensitive to inhomogeneity in a single imaging step

A nuclear magnetic resonance imaging scheme for imaging living body information related to the physiological function change in the living body. In this scheme, the pulse sequence realizes a first imaging scheme sensitive to functional information of the body to be examined and a second imaging scheme insensitive to the functional information of the body to be examined so as to obtain first and second types of the nuclear magnetic resonance images corresponding to the first and second imaging schemes, respectively, by a single execution of this pulse sequence. The functional information of the body to be examined is then obtained by processing the first and second types of the nuclear magnetic resonance images.

Method and apparatus for high speed magnetic resonance imaging with improved image quality

A nuclear magnetic resonance imaging method and apparatus, capable of obtaining images with high spatial resolution arid S/N ratio, reducing the influence of the inhomogeneity of the static magnetic field and the chemical shift artifacts, and improving the contrast in the T2 enhanced image and T1 enhanced image. The imaging uses the pulse sequence, including: application of RF pulses and slicing gradient magnetic field for exciting a desired region of the body to be examined; application of reading gradient magnetic fields which regularly fluctuate between a negative value and a positive value; application of initial phase encoding gradient magnetic field before the reading gradient magnetic field is applied; application of a predetermined pulse shaped phase encoding gradient magnetic field every time the reading gradient magnetic field changes polarity; and collection of the echo signals emitted from the desired region every time the reading gradient magnetic field changes polarity. This pulse sequence is repeated while sequentially changing a setting of the initial phase encoding gradient magnetic field applied.

Nuclear magnetic resonance imaging with patient protection against nerve stimulation and image quality protection against artifacts

A nuclear magnetic resonance imaging scheme capable of reducing the eddy currents induced within the living body outside of the imaging region, so as to protect the patient against the nerve stimulation due to the eddy currents, and obtaining the MR images at high image quality by protecting the image quality against the N/2 and chemical artifacts. The nerve stimulation is prevented by providing a shield member for shielding a nerve stimulation sensitive portion of the patient located outside of the imaging region from a change of the gradient magnetic fields. The artifacts are prevented by applying a reading gradient magnetic field which is repeatedly switching its polarity along a phase encoding gradient magnetic field applied at a rate of once in every two switchings of the reading gradient magnetic field, separating the acquired NMR signals resulting from odd and even turns of switchings of the reading gradient magnetic field as separate data sets, and re-constructing MR images from the separate data set for odd turns and even turns separately.

A quantitative index of intracranial cerebrospinal fluid distribution in normal pressure hydrocephalus using an MRI-based processing technique.

Abstract Our purpose was to quantify the intracranial cerebrospinal fluid (CSF) volume components using an original MRI-based segmentation technique and to investigate whether a CSF volume index is useful for diagnosis of normal pressure hydrocephalus (NPH). We studied 59 subjects: 16 patients with NPH, 14 young and 13 elderly normal volunteers, and 16 patients with cerebrovascular disease. Images were acquired on a 1.5-T system, using a 3D-fast asymmetrical spin- echo (FASE) method. A region-growing method (RGM) was used to extract the CSF spaces from the FASE images. Ventricular volume (VV) and intracranial CSF volume (ICV) were measured, and a VV/ICV ratio was calculated. Mean VV and VV/ICV ratio were higher in the NPH group than in the other groups, and the differences were statistically significant, whereas the mean ICV value in the NPH group was not significantly increased. Of the 16 patients in the NPH group, 13 had VV/ICV ratios above 30 %. In contrast, no subject in the other groups had a VV/ICV ratios higher than 30 %. We conclude that these CSF volume parameters, especially the VV/ICV ratio, are useful for the diagnosis of NPH.

Evaluation of noninvasive cerebrospinal fluid volume measurement method with 3D-FASE MRI

Hydrocephalus and cerebral atrophy are pathologies characterized by an abnormal increase in intracranial cerebrospinal fluid (CSF) volume accompanied by dilation of the cerebral ventricles and fissures. Measurements of the CSF volume are necessary to accurately assess the clinical course of such patients. A noninvasive and rapid CSF volume measurement method has been developed using heavily T2-weighted 3D-FASE MRI, which can selectively visualize the CSF with high signal intensities, and a region-growing method for extracting the CSF region. Volume measurement requires about 30 minutes, and the segmentation results of CSF are also used to create 3D displays showing the relevant anatomical information. The error in measured volumes was within 10% in phantom experiments. Intracranial and ventricular CSF volumes of normal volunteers ranged between 100 and 150 ml and between 10 and 20 ml, respectively, which agree with the values obtained by conventional methods. Increased intracranial and/or ventricular CSF volumes were observed in patients with hydrocephalus and patients with cerebral atrophy. The results suggest that the ratio of intracranial and ventricular CSF volumes could be useful for the evaluation of patients with neurological diseases.