Biomedical subjects

Yoshikazu Nakajima

Publications and source records attributed to Yoshikazu Nakajima.

17 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

Medical application of an infrared free-electron laser: selective removal of cholesterol ester in carotid artery atheromatous plaques.

OBJECT: . The purpose of this study was to determine the effectiveness of infrared free-electron laser (FEL) irradiation of cholesterol esters in human carotid artery (CA) atheromas. METHODS: The degradation of cholesterol ester was estimated from changes in the infrared absorption spectra acquired using microscopic transmission Fourier transform infrared spectroscopy. An FEL emitting radiation at 5.75-microm wavelengths and a power density of 15.9 W/cm2 was used to treat intimal slices of extirpated human arterial atherosclerotic plaques. Peak signals derived from an ester bond of cholesterol ester decreased in height as irradiation time increased and disappeared completely after 180 seconds. No other change was observed in the infrared absorption spectrum after 180 seconds of irradiation, and no histological damage was noted. CONCLUSIONS: The authors concluded that FEL irradiation can remove cholesterol ester selectively from human atheromatous CA plaques. This novel technique differs from previous approaches involving conventional lasers.

Atherosclerosis↗

PubMed2005

Assessment of the three-dimensional relationship of the ossific nuclei and cartilaginous anlagen in congenital clubfoot by 3-D MRI.

PURPOSE: Radiographic measurement is the usual method used to objectively determine the extent of a congenital clubfoot deformity. Although radiographs have been used clinically to estimate the size and location of tarsal bones through measurements of the ossific nuclei, it is not clear to what extent these relationships are actually reflected in these measurements. So, we used a 3-D MRI system that could more objectively estimate sizes and positional relationships. MATERIAL AND METHOD: We evaluated 5 patients with unilateral congenital clubfoot deformity. Magnetic resonance imaging was performed of both feet using 1.5-T magnet. Based on the resulting magnetic resonance imaging volume data, a three-dimensional surface bone model was reconstructed by the Marching Cubes method. We used this model to perform a comparative analysis of the volume and volume ratio of each cartilaginous anlage and ossific nucleus, the length of the talus and the calcaneus, and the position of the center of gravity of ossific nuclei within the cartilaginous anlagen. We measured the relationship between the ossific nuclei and cartilaginous anlagen in the talus and calcaneus of patients with unilateral clubfoot deformity. RESULT: In clubfeet talus volume was reduced by 20.1% and calcaneal volume was reduced by 15.7%. Furthermore, the volume of the talar ossific nucleus was reduced by 42.6% and that of the calcaneal ossific nucleus was reduced by 12.1%. The length of the clubfoot talus was 8.2% shorter than normal, and that of the calcaneus was 4.8% shorter. CONCLUSION: The assessment technique presented herein was shown to be useful in ascertaining the various pathological characteristics associated with clubfoot.

Calcaneus↗

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

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↗

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

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

STUDY DESIGN: Kinematics of the upper cervical spine during head rotation were investigated using three-dimensional magnetic resonance imaging (MRI) in healthy volunteers. OBJECTIVES: To demonstrate in vivo intervertebral coupled motions of the upper cervical spine. SUMMARY OF BACKGROUND DATA: Although various in vivo and in vitro studies have identified the normal movement patterns of the upper cervical spine, no previous studies have accurately analyzed in vivo three-dimensional intervertebral motions of the upper cervical spine during head rotation. METHODS: Fifteen healthy volunteers underwent three-dimensional MRI of the upper cervical spine using a 1.0-T imager in progressive 15 degrees steps during head rotation. Segmented three-dimensional MRIs of each vertebra in the neutral position were superimposed over images taken at other positions, using voxel-based registration. Relative motions between occiput (Oc) and atlas (C1) and between C1 and axis (C2) were measured and described with 6 degrees of freedom by rigid body Euler angles and translations. RESULTS: Mean (+/- SD) maximum angles of axial rotation in Oc-C1 and C1-C2 were 1.7 +/- 1.5 degrees and 36.2 +/- 4.5 degrees to each side, respectively. Increases in angle of axial rotation in C1-C2 became smaller with increased head rotation, indicating axial rotation in C1-C2 displayed nonlinear motion. Coupled lateral bending with axial rotation was observed in the direction opposition to that of axial rotation in Oc-C1 (mean, 4.1 +/- 1.4 degrees) and C1-C2 (mean, 3.8 +/- 3.0 degrees). Coupled extension with axial rotation occurred at both C0-C1 (mean, 13.3 +/- 4.9 degrees) and C1-C2 (mean, 6.9 +/- 3.0 degrees). CONCLUSIONS: We developed an innovative in vivo three-dimensional motion analysis system using three-dimensional MRI. In vivo coupled motions of the upper cervical spine investigated using this system supported the results of the previous in vitro study.

Adult↗

PubMed2004

Src family kinase inhibitor PP1 reduces secondary damage after spinal cord compression in rats.

The synthetic pyrazolopyrimidine, 4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (PP1) is a novel, potent, and selective inhibitor of Src family tyrosine kinases. Vascular permeability appears to be mediated by vascular endothelial growth factor (VEGF), which requires the activation of downstream Src family kinases to exert its function. This study investigates the effects of PP1 on vascular permeability and inflammatory response in a rat spinal cord compression model. Ten minutes after compression, PP1 (PP1 group) or the vehicle only (control group) was administered. On days 1, 3, and 7 after compression, the spinal cords were removed and examined histopathologically to determine the expression of VEGF and the extent of edema and inflammation. The dryweight method was used to measure the water content of the spinal cords. The mRNA levels of tumor necrosis factor a (TNFalpha) and interleukin 1beta (IL-1beta), which is related to inflammatory responses, were measured with a real-time polymerase chain reaction (RT-PCR) system 6 h after compression. Although VEGF expression was similar in both groups, the extent of contusional lesion in the PP1 group was reduced by approximately 35% on day 3. Moreover, the water content on days 1, 3, and 7 was significantly reduced and macrophage infiltration on days 3 and 7 was dramatically reduced in the PP1 group. TNF and IL-1beta mRNA expression in the PP1 group were also significantly reduced. These results indicate that PP1 reduces secondary damage after spinal cord injury.

Animals↗

PubMed2004

Improvement of depth position in 2-D/3-D registration of knee implants using single-plane fluoroscopy.

Two-dimensional (2-D)/three-dimensional (3-D) registration techniques using single-plane fluoroscopy are highly important for analyzing 3-D kinematics in applications such as total knee arthroplasty (TKA) implants. The accuracy of single-plane fluoroscopy-based techniques in the determination of translation perpendicular to the image plane (depth position), however, is relatively poor because a change in the depth position causes only small changes in the 2-D silhouette. Accuracies achieved in depth position using conventional 2-D/3-D registration techniques are insufficient for clinical applications. Therefore, we propose a technique for improving the accuracy of depth position determination in order to develop a system for analyzing knee kinematics over the full six degrees of freedom (6 DOF) using single-plane fluoroscopy. In preliminary experiments, the behaviors of errors for each free variable were quantified as evaluation curves by examining changes in cost function with variations in the free variable. The evaluation curve for depth position was more jagged, and the curve peak less pointy, compared to the evaluation curves of the other five variables, and the curve was found to behave differently. Depth position is therefore optimized independently of the other variables, using an approximate evaluation curve of depth position prepared after initial registration. Accuracy of the proposed technique was evaluated by computer simulation and in vitro tests, with validation of absolute position and orientation performed for each knee component. In computer simulation tests, root-mean-square error (RMSE) in depth position was improved from 2.6 mm (conventional) to 0.9 mm (proposed), whereas for in vitro tests, RMSE improved from 3.2 mm to 1.4 mm. Accuracy of the estimation of the remaining two translational and three rotational variables was found to be almost the same as that obtained by conventional techniques. Results of in vivo tests are also described in which the possibility of full 6 DOF kinematic analysis of TKA implants is shown.

Algorithms↗

PubMed2004

Effects of aging and postmenopausal hypoestrogenism on skin elasticity and bone mineral density in Japanese women.

Skin collagen content and bone mass decrease with aging. Loss of collagen from the skin might decrease its elasticity. We investigated associations between skin elasticity, bone mineral density (BMD), age, and menopausal hypoestrogenism. Thirty-eight healthy Japanese postmenopausal women were studied (mean age, 55.7 +/- 5.9 yr; range, 48 to 71). Skin elasticity was measured using a suction device applied to the dorsal right forearm. BMD values of L2 to 4 vertebral bodies were measured by dual-energy X-ray absorptiometry. Age showed significant negative correlations with both skin elasticity and BMD (r = -0.57, p<0.001 and r = -0.40, p<0.05, respectively). Years since menopause also showed significant negative correlations with both skin elasticity and BMD (r = -0.51, p<0.01 and r = -0.41, p<0.05, respectively). We also found a positive correlation between skin elasticity and BMD in these postmenopausal women (r = 0.44, p<0.01). In conclusion, we demonstrated declining skin elasticity and bone mass in postmenopausal women to possibly be age- and estrogen-related. Additionally, decreased skin elasticity might serve as a predictor of bone loss in postmenopausal women.

Absorptiometry, Photon↗

PubMed2004

Ruptured aneurysm arising from the proximal end of an azygos anterior cerebral artery--case report.

A 59-year-old woman presented with subarachnoid hemorrhage. Conventional angiography and three-dimensional computed tomography (3-D CT) angiography showed a saccular aneurysm at the junction of the azygos anterior cerebral artery (ACA) and the left A1 segment. This aneurysm was associated with a fenestration of the right hypoplastic A1 segment. The aneurysm neck was completely clipped, preserving the azygos ACA and other perforators. Aneurysm of the azygos ACA is almost always located at the distal bifurcation, and rarely at the proximal end. Proximal azygos ACA aneurysm can mimic anterior communicating artery aneurysm. Therefore, accurate preoperative diagnosis is critical using 3-D CT angiography as well as conventional angiography, and close follow up of patient is necessary to monitor for development of a de novo aneurysm at the distal bifurcation of the azygos ACA.

Aneurysm, Ruptured↗

PubMed2003

Investigation of the surgically treated and untreated unruptured cerebral aneurysms of the anterior circulation.

BACKGROUND: The natural history of unruptured cerebral aneurysms and the surgical risks are modified by several factors including size, location, and presence of subarachnoid hemorrhage (SAH). The main confusion arises because the backgrounds of the past reports describing the natural history or the surgical complication of unruptured cerebral aneurysms were different. The present study aimed to adjust the backgrounds and investigate the surgical indication with close monitoring of both surgically treated and untreated unruptured cerebral aneurysms. METHODS: In the past 9 years, 201 patients who had unruptured anterior circulation aneurysms were monitored. The decision of the operation was not randomized. The patients were divided into three subgroups by the size of the aneurysms (small group: below 5 mm, medium group: between 5 and 15 mm, large group: over 15 mm). In both surgically untreated and treated patients, overall mortality and morbidity corresponding to Rankin score II or worse was counted as unruptured aneurysm related event. The ratio of event free was compared between surgically treated and untreated patients using Log-rank test. RESULTS: In untreated patients, SAH was noted in 1 in the small group and 4 in the medium group. The annual rupture rate of the medium group was 12 times higher than that of the small group. In surgically treated patients, overall mortality and morbidity of the surgery was 2.3% in the small group, 3.6% in the medium group, and 20% in the large group. One surgically treated patient had SAH because of regrowth of aneurysm. When ratio of event free was compared, no significant advantage of surgery was noted in the small group and in all of the patients. However, the benefit of surgery was significant in the medium group (Log-rank p = 0.0189). CONCLUSIONS: The present results indicated that prophylactic surgery has a benefit for the medium-size aneurysms (5-15 mm) of the anterior circulation. For large aneurysms, individual investigation is necessary because of the variety of surgical difficulties, and the complex symptoms because of rupture and the mass effect as well as cerebral embolism. In small aneurysms, careful observation may be a reasonable choice unless the aneurysm is at a specially high risk of rupture.

Aged↗

PubMed2003

Neuronal apolipoprotein E is not synthesized in neuron after focal ischemia in rat brain.

Apolipoprotein E (ApoE) is a major apolipoprotein in the central nervous system (CNS) that plays an important role in Alzheimer's disease. It may also be involved in other CNS disorders including ischemic injury. We investigated the changes of ApoE protein and mRNA expression in the brain with middle cerebral artery occlusion (MCAO) to clarify its origin after focal ischemia in rats. Increased ApoE immunoreactivity was recognized in astrocytes 3-14 days after MCAO in the affected side of cortex, and in neurons 4-14 days after MCAO in the same area. ApoE immunoreactivity was also detected in macrophages in the ischemic core 3-14 days after MCAO. In contrast, ApoE mRNA was expressed in astrocytes and macrophages, but not in neurons. These results suggested that neuronal ApoE was not synthesized in neurons, but derived from astrocytes.

Animals↗

PubMed2003

A novel isoindoline, porritoxin sulfonic acid, from Alternaria porri and the structure-phytotoxicity correlation of its related compounds.

Novel zinniol-related compound 3, named porritoxin sulfonic acid, with an isoindoline skeleton was isolated from the culture liquid of Alternaria porri. The structure was determined to be 2-(2"-sulfoethyl)-4-methoxy-5-methyl-6-(3'-methyl-2'-butenyloxy)-2,3-dihydro-1H-isoindol-1-one. The phytotoxic activities of three isoindolines (1-3) were evaluated in a seedling-growth assay against stone leek and lettuce.

Alternaria↗

PubMed2003

Efficacy of moderate hypothermia in patients with severe head injury and intracranial hypertension refractory to mild hypothermia.

OBJECT: This study was performed to determine whether moderate hypothermia (31 degrees C) improves clinical outcome in severely head injured patients whose intracranial hypertension cannot be controlled using mild hypothermia (34 degrees C). METHODS: Twenty-two consecutive severely head injured patients who fulfilled the following criteria were included in this study: an intracranial pressure (ICP) that remained higher than 40 mm Hg despite the use of mild hypothermia combined with conventional therapies; and a Glasgow Coma Scale score of 8 or less on admission. After the failure of mild hypothermia in combination with conventional therapies; patients were exposed to moderate hypothermia as quickly as possible. As brain temperature was reduced from 34 to 31 degrees C, the volume of intravenous fluid infusion was increased significantly from 1.9 +/- 0.9 to 2.6 +/- 1.2 mg/kg/hr (p < 0.01), and the dose of dopamine infusion increased significantly from 4.3 +/- 3.1 to 8.2 +/- 4.4 microg/kg/min (p < 0.01). Nevertheless, mean arterial blood pressure and heart rate decreased significantly from 97.1 +/- 13.1 to 85.1 +/- 10.5 mm Hg (p < 0.01) and from 92.2 +/- 13.8 to 72.2 +/- 14.3 beats/minute at (p < 0.01) at 34 and 31 degrees C, respectively. Arterial base excess was significantly aggravated from -3.3 +/- 4 at 34 degrees C to -5.6 +/- 5.4 mEq/L (at 31 degrees C; p < 0.05). Likewise, serum potassium concentration, white blood cell counts, and platelet counts at 31 degrees C decreased significantly compared with those at 34 degrees C (p < 0.01). In 19 (86%) of 22 patients, elevation of ICP could not be prevented using moderate hypothermia. In the remaining three patients. ICP was maintained below 40 mm Hg by inducing moderate hypothermia; however, these three patients died of multiple organ failure. These results clearly indicate that moderate hypothermia induces complications more severe than those induced by mild hypothermia without improving outcomes. CONCLUSIONS: The authors concluded that moderate hypothermia is not effective in improving clinical outcomes in severely head injured patients whose ICP remains higher than 40 mm Hg after treatment with mild hypothermia combined with conventional therapies.

Adolescent↗

PubMed2002

Successful percutaneous transluminal angioplasty for hepatic artery stenosis in an infant undergoing living-related liver transplantation.

A 1-yr-old girl underwent a living-related liver transplant, with reconstruction of hepatic artery of 2 mm in diameter under microscopy. She developed intestinal perforation requiring closure on day 4 post-transplant and suffered from hepatic artery stenosis (HAS) on post-transplant day 9. Conservative therapies, such as intravenous or transluminal administration of anti-coagulants, vasodilators or fluids, were unsuccessful and caused remarkable general edema and multiple arrhythmias as a result of increased preload. On day 15 post-transplant, because flow velocity was remarkably reduced (as shown by Doppler ultrasound) the patient underwent percutaneous transluminal angioplasty (PTA) using a kit for coronary angioplasty. The balloon catheter was inflated [first: 1.5 mm diameter, 4 atmospheric pressure (a.p.) for 30 seconds (s); second: 2.0 mm diameter, 4 a.p. for 30 s; third: 2.5 mm diameter, 10 a.p. for 30 s]. The stenosis was successfully dilated without any complication. The patient has been doing well with normal liver functions for 4 months after PTA. From this experience, PTA can be performed for HAS after liver transplantation, even in an infantile case, with a careful technique and a special device.

Angioplasty, Balloon↗

PubMedDate not supplied

In vivo elbow biomechanical analysis during flexion: three-dimensional motion analysis using magnetic resonance imaging.

The purpose of this article is to evaluate in vivo 3-dimensional kinematics of the elbow joint during elbow flexion. We studied the ulnohumeral and radiohumeral joint noninvasively in 3 elbows in healthy volunteers using a markerless bone registration algorithm. Magnetic resonance images were acquired in 6 positions of elbow flexion. The inferred contact areas on the ulna against the trochlea tended to occur only on the medial facet of the trochlear notch in all of the elbow positions we tested. The inferred contact areas on the radial head against the capitellum occurred on the central depression of the radial head in all of the tested elbow positions except for 135 degrees flexion, where the anterior rim of the radial head articulates with the capitellum.

Adult↗