Biomedical subjects

Shinichi Tamura

Publications and source records attributed to Shinichi Tamura.

At least 19 recordsLinked to original sources

PubMed2006

Kinematics of the cervical spine in lateral bending: in vivo three-dimensional analysis.

STUDY DESIGN: Kinematics of the cervical spine during lateral bending were investigated using a novel system of three-dimensional motion analysis. OBJECTIVES: To demonstrate in vivo intervertebral coupled motions of the cervical spine during lateral bending of the neck. SUMMARY OF BACKGROUND DATA: No previous studies have successfully documented in vivo three-dimensional intervertebral motions of the cervical spine during lateral bending. METHODS: Twelve healthy volunteers underwent three-dimensional magnetic resonance imaging (MRI) of the cervical spine in 7 positions with 10 degrees increments of lateral bending. Relative motions of the cervical spine were calculated automatically by superimposing a segmented three-dimensional-MRI of the vertebra in the neutral position over images of each position using volume registration. RESULTS: Mean maximum lateral bending of the cervical spine to one side was 1.6 degrees to 5.7 degrees at each level. Coupled axial rotation opposite to lateral bending was observed in the upper cervical levels (Oc-C1, 0.2 degrees ; C1-C2, 17.1 degrees ), while in the subaxial cervical levels, it was observed in the same direction as lateral bending except for at C7-T1. Coupled flexion-extension motion was small at all vertebral levels (<1.1 degrees). CONCLUSIONS: We succeeded in identifying in vivo coupled motions of the cervical spine in lateral bending for the first time.

Adult↗

PubMed2006

Longitudinal quantitative evaluation of lesion size change in femoral head osteonecrosis using three-dimensional magnetic resonance imaging and image registration.

It remains controversial whether some lesions of femoral head osteonecrosis regress during the natural course of the disease. With image registration, accurately matched image sets of the same subject can be acquired at different times. We applied image registration to evaluate lesion size change and assessed accuracy and usefulness compared to volume measurements and a conventional method. We also investigated whether lesions regress with this technique and with volume measurements. Baseline and 1 year minimum follow-up scans were conducted on 25 patients (31 hips) without radiological evidence of collapse. A three-dimensional (3D) spoiled gradient recalled echo sequence was used in the coronal direction (slice thickness = 2 mm; slice pitch = 1 mm). Size change was evaluated on all contiguous pairs of matched images after image registration. As a conventional method, coronal images (slice thickness = 5 mm) were reconstructed, and size change was evaluated on the five representative coronal slices. Evaluation with the conventional method identified eight lesions with apparent reduction; assessments using image registration and volume measurements identified three lesions, all within a year of initial steroid treatment and remaining at ARCO stage I at follow up. Evaluation of lesion size change using image registration was comparable to volume measurements. Inaccurate estimation of lesion size change due to mismatching of slice planes can be excluded. We demonstrated that some early lesions detected less than a year after initial steroid treatment can show size reduction with image registration as well as with volume measurements.

Adolescent↗

PubMed2006

Novel display technique for reference images for visibility of temporal change on radiographs--color digital summation radiography.

PURPOSE: The present study investigated color digital summation radiography (CDSR) as a novel display technique for reference images for the visibility of temporal change on radiographs. In CDSR, only the parts with temporal differences are displayed in color. Moreover, all other parts are displayed in gray scale. MATERIALS AND METHODS: CDSR was defined as "radiographs combined by the additive color mixture method". The visibility of simulated nodules located in the lung fields and mediastinum was evaluated by 12 radiologists (mean experience, 9.8 years; range, 1-26 years) for 24 conventional radiographs and CDSR for 6 color patterns. A five-point rating system (5, very good; 4, good; 3, adequate; 2, poor; 1, very poor) was used. RESULTS: The mean scores (average +/- standard deviation) for the visibility of simulated nodules were as follows: magenta, 3.88 +/- 0.90; blue, 3.08 +/- 0.72; green, 3.04 +/- 0.86; red, 3.00 +/- 0.98; cyan, 2.71 +/- 0.86; and yellow, 2.50 +/- 0.72. Compared to conventional radiography in gray scale, at 1.21 +/- 0.41, all six color patterns for CDSR displayed significantly improved scores (p<0.001). CONCLUSION: CDSR might represent a useful technique for reference images from chest digital radiography.

Angiography↗

PubMed2005

[Development of three-dimensional kinematic analysis system for artificial knee implants using X-ray fluoroscopic imaging].

To achieve quantitative assessment of 3D dynamic motion of artificial knee implants under clinical conditions, we developed a 3D kinematic analysis system using X-ray fluoroscopic imaging. The 3D pose-estimation technique for knee implants was built on a 2D/3D registration algorithm, which determines the spatial pose for each femoral and tibial component from the knee implant contours and computer-assisted design (CAD) models of the implant. In order to validate the accuracy of the 3D pose estimation and the system, computer simulation and in vitro tests were performed using images of knee implants taken in 10 different poses with respect to X-ray focus. Computer simulation tests showed that the root mean square errors (RMSE) for all variables were less than 1.0 mm 1.0 degrees. In vitro tests showed that the RMSE for translation perpendicular to the X-ray image plane was about 1.5 mm, while the accuracy of the remaining two translational and three rotational variables was found to be sufficient for analyzing knee kinematics. Computation time in 3D pose estimation was then obtained in less than 30 seconds for each frame. In clinical application, dynamic movement in deep knee bending was quantitatively analyzed, and the feasibility and effectiveness of the system was demonstrated.

Algorithms↗

PubMed2005

Application of 3D-MR image registration to monitor diseases around the knee joint.

PURPOSE: To estimate the accuracy and consistency of a method using a voxel-based MR image registration algorithm for precise monitoring of knee joint diseases. MATERIALS AND METHODS: Rigid body transformation was calculated using a normalized cross-correlation (NCC) algorithm involving simple manual segmentation of the bone region based on its anatomical features. The accuracy of registration was evaluated using four phantoms, followed by a consistency test using MR data from the 11 patients with knee joint disease. RESULTS: The registration accuracy in the phantom experiment was 0.49+/-0.19 mm (SD) for the femur and 0.56+/-0.21 mm (SD) for the tibia. The consistency value in the experiment using clinical data was 0.69+/-0.25 mm (SD) for the femur and 0.77+/-0.37 mm (SD) for the tibia. These values were all smaller than a voxel (1.25 x 1.25 x 1.5 mm). CONCLUSION: The present method based on an NCC algorithm can be used to register serial MR images of the knee joint with error on the order of a sub-voxel. This method would be useful for precisely assessing therapeutic response and monitoring knee joint diseases; normalized cross-correlation; accuracy.

Algorithms↗

PubMed2005

Usefulness of three-dimensional multidetector-row CT images for preoperative evaluation of tumor extension in primary breast cancer patients.

PURPOSE: Usefulness of three dimensional (3D) multidetector-row CT (MDCT) images for preoperative evaluation of tumor extension was studied in primary breast cancer patients. METHODS: 3D-MDCT tumor images of 143 tumors in 143 patients with primary breast cancer were created with the volume rendering method. The transverse tumor size (TS) and vertical tumor size (VS) were then measured in an anterior-posterior view of the 3D-MDCT images. The pathological tumor size was determined according to a map of the tumor spread prepared by pathologists using multi-sliced (3-5 mm intervals) surgical specimens and compared with the tumor size on 3D-MDCT images. RESULTS: First, the optimal method for creating 3D-MDCT tumor images was determined for the first 40 patients (learning set), resulting in a fairly good correlation of tumor size on 3D-MDCT images with pathological tumor size (r = 0.983 for TS and r = 0.958 for VS). We then carried out a validation study on the next 103 patients (validation set). The 3D-MDCT tumor size's strong correlation with the pathological tumor size demonstrated a high rate of accuracy (r = 0.974 for TS and r = 0.977 for VS). Subset analyses according to histological type showed that correlation coefficients were r = 0.979 for TS and r = 0.981 for VS of invasive ductal carcinomas (n = 88), r = 0.948 for TS and r = 0.970 for VS of ductal carcinomas in situ (n = 10), and r = 0.984 for TS and r = 0.976 for VS of invasive lobular carcinomas (n = 5). CONCLUSION: 3D-MDCT images can assess breast cancer tumor extension highly accurately, and thus seems to be useful for planning the extent of resection in breast conserving surgery.

Adult↗

PubMed2005

Visualization of femorotibial contact in total knee arthroplasty using X-ray fluoroscopy.

The purpose of this study was to build a visualization technique of the femorotibial contact in fixed-bearing total knee arthroplasty (TKA) using X-ray fluoroscopy, and to apply this technique to a TKA patient during dynamic motion. In vivo kinametcis of the metallic knee implant was determined using a 2D/3D registration technique, which uses computer assisted design (CAD) model of the implant to estimate the 3D pose of radiopaque metallic femoral and tibial components from a single-plane fluoroscopic image. In fixed-bearing TKA, a 3D pose of radiolucent tibial polyethylene insert can be determined from the estimated pose of the tibial component. To visualize femorotibial contact, the proximity between surfaces of femoral component and tibial insert was calculated, and mapped onto the insert surface model. For the clinical application, dynamic states of contact on the tibial insert were observed including axial rotation and unilateral loading during knee flexion, and post-cam contact of posterior stabilized TKA. The present technique provided us new information and enabled us to better understand the relationship between in vivo knee kinematics and articular shape of the implant.

Arthroplasty, Replacement, Knee↗

PubMed2005

Application of three-dimensional magnetic resonance image registration for monitoring hip joint diseases.

The purpose of this study was to estimate the accuracy of a method in which three-dimensional (3D) magnetic resonance (MR) volume registration is used for monitoring hip joint disease. Data were analyzed using a normalized cross-correlation (NCC) algorithm involving a user-selected 3D box including the proximal femur. Most of the femoral head was not included in the 3D box because it can become deformed during the course of disease. The accuracy of registration around the femoral head was evaluated using five phantoms and clinical MR data of 17 patients with hip joint disease. In the phantom experiment, registration accuracy was evaluated using four fiducial markers attached to the femoral head. In the experiment using clinical data, registration accuracy was evaluated using a landmark in the femoral head. The registration accuracy in the phantom and clinical experiment was 0.43+/-0.18 mm (S.D.) and 1.12+/-0.46 mm (S.D.), respectively. The former is a value less than half the minimum dimension of a voxel (1.25 x 1.25 x 1.0 mm). Although the latter is slightly larger than the minimum dimension of a voxel, actual errors would be smaller because of the uncertainty in landmark localization. In conclusion, the present method based on an NCC algorithm can be used to accurately register serial MR images of the femoral heads with an error on the order of a voxel. We believe that this method is sufficiently accurate for monitoring hip joint diseases.

Algorithms↗

PubMed2005

In vivo three-dimensional wrist motion analysis using magnetic resonance imaging and volume-based registration.

This study represents a new attempt to non-invasively analyze three-dimensional motions of the wrist in vivo. A volume-based registration method using magnetic resonance imaging (MRI) was developed to avoid radiation exposure. The primary aim was to evaluate the accuracy of volume-based registration and compare it with surface-based registration. The secondary aim was to evaluate contributions of the scaphoid and lunate to global wrist motion during flexion-extension motion (FEM), radio-ulnar deviation (RUD) and radial-extension/ulnoflexion, "dart-throwing" motion (DTM) in the right wrists of 12 healthy volunteers. Volume-based registration displayed a mean rotation error of 1.29 degrees +/-1.03 degrees and a mean translation error of 0.21+/-0.25 mm and was significantly more accurate than surface-based registration in rotation. Different patterns of contribution of the scaphoid and lunate were identified for FEM, RUD, and DTM. The scaphoid contributes predominantly in the radiocarpal joint during FEM, in the midcarpal joint during RUD and almost equally between these joints during DTM. The lunate contributes almost equally in both joints during FEM and predominantly in the midcarpal joint during RUD and DTM.

Biomechanical Phenomena↗

PubMed2005

Successful non-T-cell-depleted HLA-haploidentical 3-loci mismatched bone marrow transplantation.

A 17-year-old boy with therapy-related acute myelocytic leukemia (FAB classification-M0) successfully received allogeneic non-T-cell depleted (non-TCD) bone marrow transplantation (BMT) from his 3-loci HLA-mismatch mother, although pre-BMT detection of feto-maternal microchimerism was negative. The BMT was performed with reduced intensity conditioning (total body irradiation; 4 Gy, fludarabine; 20 mg/m(2) x 6, and melphalan; 70 mg/m(2) x 2) and short-course methotrexate and tacrolimus for GVHD prophylaxis. Complete donor chimera was obtained on day 19, associated with Grade 3 acute GVHD (skin: Stage 1, liver: Stage 0, gut: Stage 3) that was well controlled with immunosuppressive therapies. At day 200 of transplantation, he was in complete remission with no signs of chronic GVHD. Our case suggests that non-TCD HLA-haploidentical 3-loci mismatched BMT can be safely performed from mother to offspring even when feto-maternal microchimerism is barely detectable with the current detection procedure.

Adolescent↗

PubMed2005

Involvement of the Toll-like receptor 9 signaling pathway in the induction of innate immunity by baculovirus.

We have previously shown that mice inoculated intranasally with a wild-type baculovirus (Autographa californica nuclear polyhedrosis virus [AcNPV]) are protected from a lethal challenge by influenza virus. However, the precise mechanism of induction of this protective immune response by the AcNPV treatment remained unclear. Here we show that AcNPV activates immune cells via the Toll-like receptor 9 (TLR9)/MyD88-dependent signaling pathway. The production of inflammatory cytokines was severely reduced in peritoneal macrophages (PECs) and splenic CD11c(+) dendritic cells (DCs) derived from mice deficient in MyD88 or TLR9 after cultivation with AcNPV. In contrast, a significant amount of alpha interferon (IFN-alpha) was still detectable in the PECs and DCs of these mice after stimulation with AcNPV, suggesting that a TLR9/MyD88-independent signaling pathway might also participate in the production of IFN-alpha by AcNPV. Since previous work showed that TLR9 ligands include bacterial DNA and certain oligonucleotides containing unmethylated CpG dinucleotides, we also examined the effect of baculoviral DNA on the induction of innate immunity. Transfection of the murine macrophage cell line RAW264.7 with baculoviral DNA resulted in the production of the inflammatory cytokine, while the removal of envelope glycoproteins from viral particles, UV irradiation of the virus, and pretreatment with purified baculovirus envelope proteins or endosomal maturation inhibitors diminished the induction of the immune response by AcNPV. Together, these results indicate that the internalization of viral DNA via membrane fusion mediated by the viral envelope glycoprotein, as well as endosomal maturation, which releases the viral genome into TLR9-expressing cellular compartments, is necessary for the induction of the innate immune response by AcNPV.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Response to imatinib mesylate in a patient with idiopathic hypereosinophilic syndrome associated with cyclic eosinophil oscillations.

A 26-year-old man with idiopathic hypereosinophilic syndrome (HES) was treated with imatinib mesylate following a 5-year history of prednisolone therapy. The patient had hypereosinophilia (absolute eosinophil counts >1500/microL) occurring in cyclic oscillations as well as histologically diagnosed eosinophilic vasculitis, bursitis, and periodic soft-tissue swellings. Laboratory data revealed high levels of serum tryptase and increased numbers of mast cells in the bone marrow, but serum interleukin 5 levels were within the normal range. The disease initially responded well to 100 mg/day of imatinib mesylate but recurred 8 weeks later. Thereafter, a daily 200-mg dose was temporarily effective. Despite the response to imatinib, the FIP1L1-PDGFRA fusion gene was not detected by fluorescence in situ hybridization analysis. Additional molecular and cytogenetic studies showed neither translocations of platelet-derived growth factor receptor (PDGFR) genes nor mutations in the c-KIT or the PDGFR genes. Although imatinib mesylate is a choice of treatment for patients with HES, its precise molecular mechanism in individual cases remains to be clarified.

Adult↗

PubMed2005

Three-dimensional ultrasound imaging of breast cancer by a real-time intraoperative navigation system.

BACKGROUND: In order to achieve a good cosmetic result without increasing the risk of ipsilateral breast cancer recurrence after breast conserving surgery, it is very important to minimize the resection volume of the breast without compromising the negativity of the surgical margin. For this purpose, it is necessary to obtain precise information on tumor extension. We therefore developed a three-dimensional (3-D) ultrasound navigation system for breast cancer surgery, which can be performed in the operating room just before surgery. METHODS: We obtained 3-D breast tumor images by the 3-D ultrasound navigation system in 40 patients with primary breast cancer (stage 0-II) who underwent mastectomy or breast conserving surgery. The tumor size was measured in a coronal view of the 3-D tumor image and compared with the tumor size obtained from a pathological map of the tumor extension. RESULTS: We obtained 3-D tumor images in 38 patients (success rate=95%). The tumor size in the images showed a very strong correlation with the pathological tumor size (r=0.898). The difference in tumor size between the 3-D images and pathology was less than 1 cm in 29 tumors (76.3%) and less than 2 cm in 36 (94.7%). On the other hand, the difference in tumor size between palpation and pathology was less than 1 cm in 19 out of 38 tumors (50.0%) and less than 2 cm in 29 tumors (76.3%). The absolute difference between the 3-D images and pathology was significantly less than that between palpation and pathology (p=0.0197). CONCLUSIONS: Our 3-D ultrasound navigation system is useful in visualizing breast tumor extension and is more accurate than palpation. The system is expected to be helpful in deciding on the appropriate surgical margin in breast cancer surgery, resulting in a better cosmetic outcome without increasing the risk of surgical margin positivity.

Adult↗

PubMed2005

Estimation of contrast of refraction contrast imaging compared with absorption imaging-basic approach.

PURPOSE: We discuss the usefulness of the refraction contrast method using highly parallel X-rays as a new approach to minute lung cancer detection. The advantages of refraction contrast images are discussed in terms of contrast, and a comparison is made with absorption images. MATERIALS AND METHODS: We simulated refraction contrast imaging using globules with the density of water in air as models for minute lung cancer detection. The contrast intensified by bright and dark lines was compared on a globule with the contrast of absorption images. We adopted the Monte Carlo simulation to determine the strength of the profile curve of the photon counts at the detector. RESULTS: The obtained contrasts were more intense by two to three digits than those obtainable with the absorption contrast imaging method. CONCLUSION: The contrast in refraction contrast imaging was more intense than that obtainable with absorption contrast imaging. A two to three digit improvement in contrast means that it is possible to greatly reduce the exposure dose necessary for imaging. Therefore, it is expected to become possible to detect the interfaces of soft tissues, which are difficult to capture with conventional absorption imaging, at low dosages and high resolution.

Absorption↗

PubMed2005

Ray tracing analysis of overlapping objects in refraction contrast imaging.

We simulated refraction contrast imaging in overlapping objects using the ray tracing method. The easiest case, in which two columnar objects (blood vessels) with a density of 1.0 [g/cm3], run at right angles in air, was calculated. For absorption, we performed simulation using the Snell law adapted to the object's boundary. A pair of bright and dark spot results from the interference of refracted X-rays where the blood vessels crossed. This has the possibility of increasing the visibility of the image.

Angiography↗

PubMed2004

Kinematics of the subaxial cervical spine in rotation in vivo three-dimensional analysis.

STUDY DESIGN: Three-dimensional intervertebral motions of the subaxial cervical spine during head rotation were investigated in healthy volunteers using three-dimensional magnetic resonance imaging (MRI). OBJECTIVES: To document intervertebral coupled motions of the subaxial cervical spine during rotation. SUMMARY OF BACKGROUND DATA: In vivo three-dimensional kinematics of the subaxial cervical spine in rotation have not previously been well described, since they are too complicated to follow using conventional radiography or computed tomography techniques. METHODS: Ten healthy volunteers underwent three-dimensional MRI of the cervical spine in 11 positions with 15 degrees increments during head rotation using a 1.0-T imager. Relative motions of the subaxial cervical spine were calculated by automatically superimposing a segmented three-dimensional MRI of the vertebra in the neutral position over images of each position using volume registration. Three-dimensional motions of adjacent vertebrae were represented with 6 df (6 degrees of freedoms) by Euler angles and translations on the coordinate system defined by Panjabi, then visualized in animations using surface bone models. RESULTS: Mean axial rotation of the subaxial cervical spine in maximum head rotation (69.5 degrees ) was 2.2 degrees at C2-C3, 4.5 degrees at C3-C4, 4.6 degrees at C4-C5, 4.0 degrees at C5-C6, 1.6 degrees at C6-C7, and 1.5 degrees at C7-T1. Coupled lateral bending with axial rotation was observed in the same direction as axial rotation at all levels (C2-C3, 3.6 degrees ; C3-C4, 5.4 degrees; C4-C5, 5.0 degrees ; C5-C6, 5.3 degrees ; C6-C7, 4.9 degrees ; C7-T1, 1.2 degrees ). Coupled extension with axial rotation occurred in the middle cervical region (C2-C3, 1.4 degrees ; C3-C4, 2.3 degrees ; C4-C5, 1.5 degrees ), while in the lower cervical region, flexion was coupled with axial rotation (C5-C6, 0.9 degrees ; C6-C7, 2.4 degrees ; C7-T1, 3.0 degrees ). CONCLUSIONS: We investigated intervertebral motions of the subaxial cervical spine during head rotation using a three-dimensional imaging system, and obtained the first accurate depictions of in vivo coupled motion. These findings will be helpful as the basis for understanding abnormal conditions.

Adult↗

PubMed2004

Surface-based registration accuracy of CT-based image-guided spine surgery.

Registration is a critical and important process in maintaining the accuracy of CT-based image-guided surgery. The aim of this study was to evaluate the effects of the area of intraoperative data sampling and number of sampling points on the accuracy of surface-based registration in a CT-based spinal-navigation system, using an optical three-dimensional localizer. A cadaveric dry-bone phantom of the lumbar spine was used. To evaluate registration accuracy, three alumina ceramic balls were attached to the anterior and lateral aspects of the vertebral body. CT images of the phantom were obtained (1-mm slice thickness, at1-mm intervals) using a helical CT scanner. Twenty surface points were digitized from five zones defined on the basis of anatomical classification on the posterior aspects of the target vertebra. A total of 20 sets of sampling data were obtained. Evaluation of registration accuracy accounted for positional and rotational errors. Of the five zones, the area that was the largest and easiest to expose surgically and to digitize surface points was the lamina. The lamina was defined as standard zone. On this zone, the effect of the number of sampling points on the positional and rotational accuracy of registration was evaluated. And the effects of the additional area selected for intraoperative data sampling on the registration accuracy were evaluated. Using 20 surface points on the posterior side of the lamina, positional error was 0.96 mm +/- 0.24 mm root-mean-square (RMS) and rotational error was 0.91 degrees +/- 0.38 degrees RMS. The use of 20 surface points on the lamina usually allows surgeons to carry out sufficiently accurate registration to conduct computer-aided spine surgery. In the case of severe spondylosis, however, it might be difficult to digitize the surface points from the lamina, due to a hypertrophic facet joint or the deformity of the lamina and noisy sampling data. In such cases, registration accuracy can be improved by combining use of the 20 surface points on the lamina with surface points on other zones, such as on the both sides of the spinous process.

Analysis of Variance↗

PubMed2004

Automated segmentation of necrotic femoral head from 3D MR data.

Segmentation of diseased organs is an important topic in computer assisted medical image analysis. In particular, automatic segmentation of necrotic femoral head is of importance for various corresponding clinical tasks including visualization, quantitative assessment, early diagnosis and adequate management of patients suffering from avascular necrosis of the femoral head (ANFH). Early diagnosis and treatment of ANFH is crucial since the disease occurs in relatively young individuals with an average age of 20-50, and since treatment options for more advanced disease are frequently unsuccessful. The present paper describes several new techniques and software for automatic segmentation of necrotic femoral head based on clinically obtained multi-slice T1-weighted MR data. In vivo MR data sets of 50 actual patients are used in the study. An automatic method built up to manage the segmentation task according to image intensity of bone tissues, shape of the femoral head, and other characters. The processing scheme consisted of the following five steps. (1) Rough segmentation of non-necrotic lesions of the femur by applying a 3D gray morphological operation and a 3D region growing technique. (2) Fitting a 3D ellipse to the femoral head by a new approach utilizing the constraint of the shape of the femur, and employing a principle component analysis and a simulated annealing technique. (3) Estimating the femoral neck location, and also femoral head axis by integrating anatomical information of the femur and boundary of estimated 3D ellipse. (4) Removal of non-bony tissues around the femoral neck and femoral head ligament by utilizing the estimated femoral neck axis. (5) Classification of necrotic lesions inside the estimated femoral head by a k-means technique. The above method was implemented in a Microsoft Windows software package. The feasibility of this method was tested on the data sets of 50 clinical cases (3000 MR images).

Automation↗