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Biomedical subjects

Naoki Suzuki

Publications and source records attributed to Naoki Suzuki.

At least 37 records · Page 2Linked to original sources
PubMed2005

Estimation of dislocation after total hip arthroplasty by 4-dimensional.

We constructed a 4-dimensional musculoskeletal model for patients who have undergone total hip arthroplasty (THA), which aimed to simulate the movement of the patient's inner body structure and estimate the complications that can arise with THA. The model reflects patient-specific characteristics of the bone geometry, implant alignment and hip movement. In order to estimate the direction of the muscle force and the length of the muscles, we developed a string-type muscle model that represents the route of the muscles. The strings expand and contract according to the movement of the origin and insertion location of the muscle. We developed models for the seven muscles related to movement of the hip joint. By using this model, clinicians will be able to predict the possibility of dislocation or recognize the actual causes of dislocation, as well as any possible influences the muscle may have on dislocation.

Arthroplasty, Replacement, Hip↗
PubMed2005

Analysis of masticatory muscle condition using the 4-dimensional muscle model for a patient with square mandible.

The present study was conducted to ascertain characteristics of mandibular movements in patients with SQM, observe the kinetics of masticatory muscles using a four-dimensional (4D) muscle model, and kinetically investigate the etiology of Square Mandible (SQM). As results, 1, In the maximum opening position, location of the condyle was beyond the articular tubercle for volunteer, but within the mandibular fossa for SQM patient. 2, While the temporal muscle of volunteer was markedly expanded, that of SQM patient was not. 3, In both volunteer and SQM during left lateral excursion, the right mandibular condyle moved to a position slightly before the lowest point of the articular tubercle. The 4D muscle model showed that the cause of limited mouth opening in SQM patient was insufficient expansion of the temporal muscle, and not dysfunction of the opening muscles. Insufficient expansion of the temporal muscle stresses the masseter muscle and leads to hypertrophy of the masseter muscle and hyperplasia of the mandibular angle, resulting in the unique facial configuration.

Adult↗
PubMed2005

Construction of a high-tech operating room for image-guided surgery using VR.

This project aimed to construct an operating room to implement high dimensional (3D, 4D) medical imaging and medical virtual reality techniques that would enable clinical tests for new surgical procedures. We designed and constructed such an operating room at Dai-san Hospital, the Jikei Univ. School of Medicine, Tokyo, Japan. The room was equipped with various facilities for image-guided, robot and tele- surgery. In this report, we describe an outline of our "high-tech operating room" and future plans.

Facility Design and Construction↗
PubMed2005

Tele-surgical simulation system for training in the use of da Vinci surgery.

Laparoscopic surgery including robotic surgery allows the surgeon to be able to conduct minimally invasive surgery. A surgeon is required to master difficult skills for this surgery to compensate for the narrow field of view, limitation of work space, and the lack of depth sensation. To counteract these drawbacks, we have been developing a training simulation system that can allow surgeons to practice and master surgical procedures. In addition, our system aims to distribute a simulation program, to provide a means of collaboration between remote hospitals, and to be able to provide a means for guidance from an expert surgeon. In this paper, we would like to show the surgery simulation for da Vinci surgery, in particular a cholecystectomy. The integral parts of this system are a soft tissue model which is created by the sphere-filled method enabling real-time deformations based on a patient's data, force feedback devices known as a PHANToM and the Internet connection. By using this system a surgeon can perform surgical maneuvers such as pushing, grasping, and detachment in real-time manipulation. Moreover, using the broadband communication, we can perform the tele-surgical simulation for training.

Computer Simulation↗
PubMed2005

Acute myocardial infarction caused by simultaneous occlusion of the right coronary artery and the left anterior descending coronary artery probably due to coronary spasm: a case report.

A 56-year-old man had an attack of chest pain associated with ST-segment elevation in both the inferolateral and anteroseptal leads on electrocardiography. Emergency coronary angiography showed thrombus in the mid right coronary artery and total occlusion in the distal left anterior descending coronary artery. Intravenous heparin infusion and antiplatelet therapy were given without other coronary intervention. After 1 week, repeat coronary angiography showed neither significant stenosis nor thrombus in the coronary arteries. Severe coronary artery spasm in the left coronary artery was induced by the provocation test with intracoronary injection of 50 microg acetylcholine. He had an uneventful hospital course. This unique case demonstrated intracoronary thrombus formation in the right coronary artery and left anterior descending coronary artery simultaneously due to suspected coronary spasm.

Coronary Angiography↗
PubMed2004

Four-dimensional model of the lower extremity after total hip arthroplasty.

We have developed a four-dimensional (4D) model of the lower extremities after total hip arthroplasty in patients. The model can aid in preventing complications such as dislocation and wearing of the sliding surface. The skeletal structure and implant alignment were obtained from CT data. We applied registration method using CAD data to estimate accurate implant alignment from scattered CT data. The reconstructed three-dimensional (3D) skeletal model was combined with motion capture data that were acquired by an optical tracking system. We displayed the patient's skeletal movement and analyzed several parameters that relate to complications. The patient's skeletal model was superimposed onto video footage that was taken by a synchronized and calibrated digital video camera. For validation of the measurement error in this system, we used open MRI to evaluate the relative movement between skin markers and bones. This system visually represents not only the 3D anatomical structure, but also 4D dynamic functions that include the time sequential transitions of components and their positions. The open MRI results indicated that the average error in hip angle was within 5 degrees for each static posture. This system enables clinicians to analyze patient's motions on the basis of individual differences. We found that our system was an effective tool in providing precise guidance of daily postoperative motions that was individualized for each patient. This system will be applicable for surgical planning, assessment of postoperative activities, and the development of new surgical techniques, materials, and prosthetic designs.

Adolescent↗
PubMed2004

Usefulness of coronary flow reserve immediately after primary coronary stenting in predicting wall motion recovery in patients with anterior wall acute myocardial infarction.

This study examined whether coronary flow reserve (CFR) measured immediately after primary coronary stenting could predict wall motion recovery in patients who have acute myocardial infarction. CFR significantly correlated with the change of wall motion score (r = 0.68, p <0.0001), and the optimal cut-off value of CFR for predicting wall motion recovery was 1.4 (sensitivity 85%, specificity 94%).

Coronary Circulation↗
PubMed2004

Novel dysferlin mutations and characteristic muscle atrophy in late-onset Miyoshi myopathy.

Miyoshi myopathy is characterized by weakness of the calf muscles during early adulthood. We report a case of late-onset Miyoshi myopathy presenting at 48 years of age, with novel mutations in the dysferlin gene. Muscle computed tomography clearly revealed severe atrophy in the soleus and medial gastrocnemius muscles. Even older patients with atrophy in the posterior compartment of the distal lower extremities and a relatively high serum creatine kinase level should be examined for the dysferlin gene.

Dysferlin↗
PubMed2004

A novel system of four-dimensional motion analysis after total hip arthroplasty.

We have developed a novel system of four-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities. This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system's measurements, open MRI was used to evaluate positions of skin markers against bones in five healthy volunteers in various postures. No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture. The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.

Adolescent↗
PubMed2004

Effects of rotation on measurement of lower limb alignment for knee osteotomy.

The purposes of this study were to clarify the effects of rotation on two-dimensional measurement of lower limb alignment for knee osteotomy using a three-dimensional method and to determine whether this 3-D simulation method could help with planning of knee osteotomy. We developed computer software to calculate femorotibial angle (FTA) and hip-knee-ankle angle (HKA) and simulate knee osteotomy from a CT-based 3-D bone model of the lower limb. Lower limb rotation on anteroposterior long-standing radiographs was measured by superimposing the 3-D bone models. Changes in alignment with limb rotation were calculated using the software. FTA after virtual closed-wedged osteotomy was measured for a hypothetical case of a rotation error of the osteotomy plane in reattaching the proximal cutting surface to the distal cutting surface. For 31 varus knees in 20 patients with medial compartment arthritis, the mean rotation angle, relative to the epicondylar axis, with variable limb position was 7.4 +/- 3.9 degrees of internal rotation (mean +/- SD), ranging from 8 degrees of external rotation to 14 degrees of internal rotation; the mean changes in FTA and HKA were 3.5 +/- 2.2 degrees (range, 0.4-8.6) and 1.6 +/- 1.3 degrees (range, 0.2-4.9), respectively. The FTA "flexion angle" (lateral view alignment from neutral AP) and the absolute HKA "flexion angle" correlated with the change in FTA and HKA with limb rotation, respectively (FTA, R = 0.999; HKA, R = 0.993). The mean change in FTA after virtual closed-wedged osteotomy was 3.2 degrees for internal and external 10 degrees rotation errors in reattaching the osteotomy plane. Rotation may affect measurement of lower limb alignment for knee osteotomy, and 3-D methods are preferable for surgical planning.

Adult↗
PubMed2004

Sphere-filled organ model for virtual surgery system.

We have been developing a virtual surgery system that is capable of simulating surgical maneuvers on elastic organs. In order to perform such maneuvers, we have created a deformable organ model using a sphere-filled method instead of the finite element method. This model is suited for real-time simulation and quantitative deformation. Furthermore, we have equipped this model with a sense of touch and a sense of force by connecting it to a force feedback device. However, in the initial stage the model became problematic when faced with complicated incisions. Therefore, we modified this model by developing an algorithm for organ deformation that performs various, complicated incisions while taking into account the effect of gravity. As a result, the sphere-filled model allowed our system to respond to various incisions that deform the organ. Thus, various physical manipulations that involve pressing, pinching, or incising an organ's surface can be performed. Furthermore, the deformation of the internal organ structures and changes in organ vasculature can be observed via the internal spheres' behavior.

Animals↗
PubMed2004

[Verification of precision by 4-dimensional analysis of mandibular movement].

PURPOSE: The 4-dimensional human body model that combines reconstructed 3-dimensional image data (CT and MRI) and exercise data of the human body is widely applied in the medical field. We have applied this technique to assess mandibular movement, particularly in dentistry, and developed a 4-dimensional system of analyzing mandibular movement. The aim of this study was to determine the accuracy of this analysis system. METHODS: A dry skull mandible was fixed at several mandibular positions and the skull-mandible relationship was measured at each position by two procedures: CT scanning was performed and a 3-dimensional image was reconstructed from image data that were regarded as true values; then, optical measurement markers attached to the dental arch were measured 3-dimensionally and calculated as positional measurement values. The measurement values were compared with the corresponding true values to identify measurement errors of the analysis system. RESULTS: The root-mean-square (RMS) errors of the 4-dimensional analysis system of mandibular movement were, on average, 0.41 mm and 0.43 degrees. CONCLUSIONS: These findings suggest that our 4-dimensional analysis system has sufficient measurement accuracy for mandibular movements.

English Abstract↗
PubMed2004

[Present and future developments of the virtual surgery and tele-virtual surgery system].

One of the applications available now in the medical field is the virtual surgery system. This system allows surgeons a safe place to master surgical techniques and to plan surgical procedures before the operation. To provide the system for use in a clinical situation, a soft tissue model and a force feedback device suited for the surgery is required. In this paper, we would like to introduce our virtual surgery system, which possesses a soft tissue model that can show accurate, real-time deformation and is equipped with a force feedback device that allows the user to experience the tactile sensations. In addition, we will introduce our tele-virtual surgery simulation system for training in the procedures used in robotic surgery.

Computer Graphics↗
PubMed2003

A linear-array freehand 3-D endoscopic ultrasound.

Recognition of the clinical importance of linear-array endoscopic ultrasound (EUS) has increased. In this study, we developed a linear-array 3-D EUS, a miniature position sensor attached to the tip of the echoendoscope used in freehand scanning. To evaluate the geometrical accuracy of the 3-D reconstruction of the system, the diameter of a sphere-shaped phantom (38 mm) was determined by five examiners and five measurers. Measured size of the sphere was 39.03 +/- 1.29 mm, with variance between examiners and measurers, and interaction of examiners with measurers was not significant. In animal and clinical studies, the system facilitated anatomical interpretation of the EUS images, especially in the pancreatobiliary area and vascular images. We concluded that this system is both accurate and reproducible, and may resolve difficulties in linear-array EUS.

Analysis of Variance↗
PubMed2003

Role of elevated platelet-associated immunoglobulin G and hypersplenism in thrombocytopenia of chronic liver diseases.

BACKGROUND AND AIM: Thrombocytopenia typically worsens with the progression of liver disease and can become a major clinical complication. Several mechanisms that contribute to thrombocytopenia have been proposed, including hypersplenism accompanied by increased platelet sequestration, platelet destruction mediated by platelet-associated immunoglobulins (PAIgG), and diminished platelet production stimulated by thrombopoietin (TPO). The purpose of the present study was to evaluate the role of each of these mechanisms in patients with liver disease-associated thrombocytopenia. METHODS: Twenty-nine patients with liver cirrhosis (LC), 20 of whom were hepatitis C virus (HCV)-seropositive, 29 chronic hepatitis (CH) patients, 24 of whom were HCV-seropositive, and 16 control patients without liver or hematopoetic disease were enrolled in this study. Serum TPO levels, PAIgG, and liver-spleen volumes were determined and correlation analyses were performed. RESULTS: No differences in serum TPO levels were observed among the three groups. The PAIgG levels were significantly elevated in CH and LC patients (mean +/- SD: 56.5 +/- 42.3 and 144.6 +/- 113.6 ng/107 cells, respectively) compared with the controls (18.9 +/- 2.5 ng/107 cells, P < 0.001 for both). Spleen volume was significantly higher only in LC (428 +/- 239) compared with CH (141 +/- 55) and control (104 +/- 50 cm3) (P < 0.001), while liver volume was not significantly different between the three groups. Correlation analyses demonstrated a significant negative correlation between platelet count with PAIgG (r = - 0.517, P < 0.001) and spleen volume (r = - 0.531, P < 0.001), and no relationship between platelet count and serum TPO level (r = 0.076). CONCLUSIONS: Serum TPO level may not be directly associated with thrombocytopenia in patients with chronic hepatitis and liver cirrhosis. In contrast, spleen volume and PAIgG are associated with thrombocytopenia in such patients, suggesting that hypersplenism and immune-mediated processes are predominant thrombocytopenic mechanisms.

Adult↗
PubMed2003

[MR spectroscopy findings of a case of intravascular malignant lymphoma: usefulness for differential diagnosis].

We report a 49-year-old previously healthy woman with acute onset of decrease in attention, dysarthria and ataxia, accompanied by drowsiness. On admission, there were cloudness of consciousness, hallucination and left hemiparesis. Cerebrospinal fluid study revealed a cell count of 1/mm3, and the cytology was class I with a slight increase in protein. MRI of the brain performed on admission showed multiple gadolinium-enhanced lesions with a T2 weighted high intensity area in the cerebral white matter. At first the patient was diagnosed as acute disseminated encephalomyelitis (ADEM), and treated with methylprednisolon pulse therapy. Soon after, she showed transient clinical improvement, but her condition soon worsened. MR spectroscopy revealed elevated choline peak, decreased NAA peak and lactate peak, which indicated a neoplastic lesion. The brain biopsy disclosed diffuse intravascular lymphoma (IVL). MRS was useful in the differential diagnosis of IVL from ADEM.

Brain↗
PubMed2003

A robotic surgery system (da Vinci) with image guided function--system architecture and cholecystectomy application.

We have developed a data fusion system for the robotics surgery system "da Vinci". The data fusion system is composed of an optical 3D location sensor and a digital video processing system. The 3D location sensor is attached to the da Vinci's laparoscope and measures its location and direction. The digital video processing system captures the laparoscope's view and superimposes 3D patient's organ models onto the captured view in real-time. We applied the system to "da Vinci" and examined this system during a cholecystectomy. In this experiment, the surgeon was able to observe the inner conditions of the organs with a stereo view.

Cholecystectomy↗