Search PubMed⌕ Search

Biomedical subjects

Y Masutani

Publications and source records attributed to Y Masutani.

9 recordsLinked to original sources
PubMed2006

Liver CT image processing: a short introduction of the technical elements.

In this paper, we describe the technical aspects of image analysis for liver diagnosis and treatment, including the state-of-the-art of liver image analysis and its applications. After discussion on modalities for liver image analysis, various technical elements for liver image analysis such as registration, segmentation, modeling, and computer-assisted detection are covered with examples performed with clinical data sets. Perspective in the imaging technologies is also reviewed and discussed.

Humans↗
PubMed2004

Diffusion property following functional hemispherectomy in hemimegalencephaly.

Diffusion-tensor imaging (DTI), a unique magnetic resonance technique for analysis of diffusion-anisotropy of the brain, can identify subtle white matter changes in vivo. To investigate changes of truncated neurofibers, DTI was conducted prior to and following functional hemispherectomy in a female infant for refractory epilepsy associated with hemimegalencephaly. Anisotropy of the amputated pyramidal tract decreased relative to the unaffected side after surgery, which reflects secondary degeneration in neurofibers. In DTI applied to infants, differentiation between developmental changes and changes associated with the current phenomenon must be evaluated cautiously. Standardization of diffusion-tensor analysis of developmental change is desirable.

Adult↗
PubMed2003

Three-dimensional white matter tractography by diffusion tensor imaging in ischaemic stroke involving the corticospinal tract.

Diffusion tensor MR imaging (DTI) provides information on diffusion anisotropy, which can be expressed with three-dimensional (3D) white matter tractography. We used 3D white matter tractography to show the corticospinal tract in eight patients with acute or early subacute ischaemic stroke involving the posterior limb of the internal capsule or corona radiata and to assess involvement of the tract. Infarcts and the tract were shown simultaneously, providing information on their spatial relationships. In five of the eight patients, 3D fibre tract maps showed the corticospinal tract in close proximity to the infarct but not to pass through it. All these patients recovered well, with maximum improvement from the lowest score on manual muscle testing (MMT) up to the full score through rehabilitation. In the other three patients the corticospinal tract was shown running through the infarct; reduction in MMT did not necessarily improve favourably or last longer, other than in one patient. As 3D white matter tractography can show spatial relationships between the corticospinal tract and an infarct, it might be helpful in prognosis of gross motor function.

Aged↗
PubMed1998

Augmented reality visualization system for intravascular neurosurgery.

We aimed to construct an augmented reality-based visualization system to support intravascular neurosurgery and evaluate it in clinical environments. Three-dimensional (3D) vascular models are overlaid on motion pictures from X-ray fluoroscopy by 2D/3D registration using fiducial markers. The models are reconstructed from 3D data obtained from X-ray computed tomographic angiography or from magnetic resonance angiography using the marching-cube algorithm. Intraoperative X-ray images are mapped as texture patterns on a screen object which is displayed with the vascular models. Distortion of X-ray fluoroscopy is eliminated by a new technique of screen mesh deformation. A quantity called reprojection distance was introduced to evaluate the reliability of the displayed images. It predicts the maximum registration error around the registered objects. Analyses of reprojection distances were performed using synthetic data consisting of marker coordinates with 2D or 3D errors. The tolerance of reprojection distance for the clinical environment was determined to be 3.0 mm. The system was tested in two clinical cases in which reprojection distances of 2.6 and 2.09 mm were obtained. Construction and evaluation of our prototype system were successfully carried out. Further development is planned employing a range sensor to permit markerless registration.

Computer Graphics↗
PubMed1997

Volumegraph (overlaid three-dimensional image-guided navigation). Clinical application of augmented reality in neurosurgery.

OBJECTIVE: We have developed an overlaid three-dimensional image (Volumegraph)-guided navigation system that allows navigation during operative procedures. The three-dimensional image is superimposed on the patient's head and body via a semi-transparent mirror. The Volumegraph can display three-dimensional images in the air by a light beam which is based on CT/MRI. METHOD: The system consists of a Volumegraph (thin plate of three-dimensional recorded medium), a Volumegraphscope and an original designed triangular-shaped marker system for registration. The three-dimensional data obtained from CT and MRI before the operation were processed by a computer. Such image data are applied for preoperative investigation to recognize the three-dimensional structure of organs and tumor. These reconstructed three-dimensional images were superimposed and registered at the patient's head according to a fiducial marker (registration). Then the operator can operate with this three-dimensional-image-guided navigation system. RESULTS: Based on clinical application in 7 cases, the system was found to be advantageous because the surgical procedures could be navigated easily by augmented reality in the surgical field. Invisible parts of the surgical field were supplemented with the overlaid three-dimensional images (Volumegraph) as if it were the virtual operative field. At another time, spatial positioning and overlaid visualization by the Volumegraph was useful for identifying anatomical structures and functional location in the image. CONCLUSION: This preliminary study of overlaid three-dimensional-image-guided navigation demonstrated its clinical usefulness. The application of augmented reality in the surgical field makes it possible to do a neurosurgical intervention easily and accurately.

Brain Neoplasms↗
PubMed1995

Development of an MRI-compatible needle insertion manipulator for stereotactic neurosurgery.

A variety of medical robots for stereotactic neurosurgery has been developed in recent years. Almost of all these robots use computed tomography (CT) to scan the brain of the patient before and during surgery. Currently, we are developing a needle insertion manipulator for magnetic resonance imaging (MRI)-guided neurosurgery. MRI techniques, including MRI angiography and functional MRI, are attractive for the development of interventional MRI therapies and operations. If a robot were available, these therapies would be minimally invasive, with more accurate guidance than is possible with current CT-guided systems. Actuation of a robot in an MRI environment is difficult because of the presence of strong magnetic fields. Therefore, the robot must be constructed of nonmagnetic materials. The system frame was manufactured using polyethylene terephthalate (PET) and was actuated using ultrasonic motors. Accuracy-evaluation procedures and phantom tests have been performed. The total accuracy of the system was approximately 3.0 mm. No artifacts caused by the manipulator were observed in the images.

Brain↗
PubMedDate not supplied

Automated segmentation and visualization of the pulmonary vascular tree in spiral CT angiography: an anatomy-oriented approach based on three-dimensional image analysis.

A new method for automated segmentation of the pulmonary vascular tree in spiral CT angiography was developed based on 3D image analysis techniques and anatomic knowledge. For efficient and effective segmentation, an anatomy-oriented approach was introduced, in which several anatomic structures are segmented sequentially and the properties of each segmented structure are used for the next step of segmentation and for validation of intermediate results. By use of clinical data of 12 patients, parameters for segmentation were analyzed and optimized. The effectiveness of the segmentation method was evaluated through the visual assessment by comparison between images of the segmentation results by volume rendering and images of maximum intensity projection of the original volume data.

Angiography↗
PubMedDate not supplied

Automated segmentation of colonic walls for computerized detection of polyps in CT colonography.

PURPOSE: A new method for fully automated segmentation of the colonic walls in volumetric CT data was developed for limitation of the search space in computerized detection of polyps. METHOD: For reliable segmentation, an anatomy-oriented approach was used, in which several anatomical structures are segmented in addition to the colon for utilization of their properties. RESULTS: The segmentation method was validated by use of 14 data sets, consisting of cases positive for colonic polyps. We found that the segmented colonic walls included all of the polyps. A subjective rating of the results was performed based on several criteria for visualization of anatomic detail of the colonic wall and mucosal surface. Except for a few cases in which insufflation of the colon was insufficient, all of the results included >95% of the colonic walls. CONCLUSION: This method for colonic wall segmentation is reliable and the segmentation results are applicable in both visualization of the colon and computer-aided diagnosis in the detection of polyps in CT colonography.

Automation↗