PubMed Health⌕ Search

Biomedical subjects

K Masamune

Publications and source records attributed to K Masamune.

17 recordsLinked to original sources
PubMed2001

System for robotically assisted percutaneous procedures with computed tomography guidance.

We present the prototype of an image-guided robotic system for accurate and consistent placement of percutaneous needles in soft-tissue targets under CT guidance inside the gantry of a CT scanner. The couch-mounted system consists of a seven-degrees-of-freedom passive mounting arm, a remote center-of-motion robot, and a motorized needle-insertion device. Single-image-based coregistration of the robot and image space is achieved by stereotactic localization using a miniature version of the BRW head frame built into the radiolucent needle driver. The surgeon plans and controls the intervention in the scanner room on a desktop computer that receives DICOM images from the scanner. The system does not need calibration, employs pure image-based registration, and does not utilize any vendor-specific hardware or software features. In the open air, where there is no needle-tissue interaction, we systematically achieved an accuracy better than 1 mm in hitting targets at 5-8 cm from the fulcrum point. In the phantom, the orientation accuracy was 0.6 degrees, and the distance between the needle tip and the target was 1.04 mm. Experiments indicated that this robotic system is suitable for a variety of percutaneous clinical applications.

Biopsy, Needle↗
PubMed1999

A new safe laparoscopic manipulator system with a five-bar linkage mechanism and an optical zoom.

This paper describes a new type of laparoscopic manipulator system designed with regard to its safety and sterilization in medical settings. It consists of a laparoscope manipulator using a five-bar linkage mechanism, an optical zoom called the automatic microzoom laparoscope, and a man-machine interface called the Head-Mouse system. The movement of the laparoscope manipulator in the X-Y plane determines the angle of the laparoscope, and the optical zoom substitutes for back-and-forth movements. This system achieves intrinsic safety and ease of sterilization due to limitations in the range of movement. The system achieves high reliability because of the simplicity of both its mechanism and its software. The newly developed optical zoom avoids the possibility of contact with organs by eliminating the back-and-forth movements of the laparoscope required for close-up observation while preserving a high-quality laparoscopic image. The Head-Mouse system for man-machine interface was designed to avoid incorrect inputs by the surgeon. To evaluate the performance of this newly developed system, an experiment was conducted in which a surgeon used the system to perform an in vivo laparoscopic cholecystectomy on a pig.

Animals↗
PubMed1997

Bile-induced DNA strand breaks and biochemical analysis of bile acids in an experimental model of anomalous arrangement of the pancreaticobiliary ducts.

A canine experimental model for the anomalous arrangement of the pancreaticobiliary ducts (APBD) was made to investigate the effects of bile acids on carcinogenesis. Seven adult mongrel dogs underwent dorsal pancreatico-cholecystostomy to serve as a functional model for APBD, and six dogs underwent the same procedure with the pancreatic duct ligated as a control group. Bile from the gallbladder was taken 14 months after surgery for bile acid analysis by HPLC. DNA strand breaks in HeLa cells induced by the bile were also investigated in situ by nick translation method. As a result, the fraction of cholic acid tended to be lower, and that of deoxycholic acid slightly higher in APBD-dogs (N.S.). The ursodeoxycholic acid percentage in APBD-dogs significantly decreased compared with that in the control and normal dogs (p < 0.05). Extremely high frequency of DNA strand breaks was shown in only two out of seven APBD-dogs. In those two dogs, the cholic acid percentage decreased and that of deoxycholic acid increased extremely. These findings suggest that the alteration of the bile composition in APBD caused frequent DNA strand breaks and repair which might lead to gene mutation and biliary tract carcinoma.

Animals↗
PubMed1996

Analysis of c-Ki-ras oncogene and p53 immunocytochemistry in the gallbladder mucosa of an experimental dog model of anomalous arrangement of the pancreaticobiliary ducts.

Anomalous arrangement of the pancreaticobiliary ducts is a congenital condition which predisposes the affected person to biliary tract carcinoma. We developed an experimental dog model of anomalous arrangement of the pancreaticobiliary ducts to investigate the mechanism of carcinogenesis in this condition. We used this model to analyze point mutations in the c-Ki-ras gene, and to assess the expression of mutant p53 protein in the gallbladder mucosa. The histopathological appearance of the gallbladder mucosa was also examined. Glandular structures were seen in four of seven (57%) gallbladders examined 14 months after the surgical creation of an anastomosis between the gallbladder and the pancreatic duct. Goblet cells were seen in two of seven gallbladders (29%). However, dot-blot hybridization and immunohistochemical study did not reveal any mutations in the c-Ki-ras gene, or any over-expression of the p53 protein in the specimens. These results show that the gallbladder mucosa is damaged by refluxing pancreatic juice in this dog model of anomalous arrangement of the pancreaticobiliary ducts, but that severe damage may be necessary to induce mutations in the c-Ki-ras proto-oncogene, or in the p53 gene.

Animals↗
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↗
PubMed1993

Bile duct atresia following extended right hepatectomy because of a tumor.

A 19 month old male infant with a mesenchymal hamartoma of the liver underwent an extended right hepatectomy. Serum bilirubin gradually rose until 3 months after the surgery, and obstructive jaundice and acholic stools were manifested at 6 months. Percutaneous transhepatic cholangio-drainage was performed. Cholangiography showed dilation of the intrahepatic bile duct of the residual lateral segment and complete obstruction of the extrahepatic bile duct. A second operation for reconstruction of the biliary tract was performed 10 months after the first surgery. No aspect of an extrahepatic biliary tract was found. Histological inspection of a surgical specimen of remnant tissue revealed only cicatricial connective tissue without any biliary structures. The clinical course has been uneventful for 18 months since the second surgery. The cause of bile duct atresia in this case is strongly suggested to be an ischemic change due to devascularization of the extrahepatic biliary tract following hepatic resection because of a tumor. To prevent this kind of complication, hepatico-enterostomy should be performed close to the cut surface of the liver.

Biliary Atresia↗
PubMed1993

A case of biliary stricture caused by cavernous transformation of the portal vein.

A case is reported of extrahepatic obstruction of the portal vein with the unusual complication of obstructive jaundice that resulted from compression of the common bile duct caused by cavernous transformation of the varicose network. It is surgically impossible to repair choledochal stenosis resulting from enlarged varices in the vicinity of the common bile duct. In this case, internal drainage from the biliary duct to the duodenum using a silastic tube and a reservoir implanted in the subcutaneous space successfully eliminated the jaundice.

Adolescent↗
PubMed1993

A case of urethral prolapse in a young girl.

Urethral prolapse is rarely reported in the pediatric literature. We report a 4 year old female with urethral prolapse and discuss the etiology and the treatments in children documented in the literature.

Child, Preschool↗
PubMed1993

A newborn case of extrarenal malignant rhabdoid tumor.

Malignant rhabdoid tumor is initially differentiated from renal tumors and characterized by extremely rapid growth. We report a newborn case of extrarenal malignant rhabdoid tumor and review the literature.

Diagnosis, Differential↗
PubMed1992

Intra-operative total enteroscopy for the management of Peutz-Jegher's syndrome.

We present a case of Peutz-Jegher's syndrome in an 18 year old female who was followed for gastrointestinal polyps for 13 years from the age of 5 years. The patient was treated four times with surgical or endoscopic polypectomy for gastrointestinal polyps. At the age of 14 years, a combined surgical and endoscopic approach for the management of Peutz-Jegher's syndrome was carried out. A large polyp of the ileum required enterotomy for its removal, and another smaller polyp of the upper jejunum was identified and removed by intra-operative total enteroscopy via the anus. Intra-operative enteroscopy allows one to identify polyps that would previously have been missed. A more complete polypectomy can be performed using this technique, allowing the patient with Peutz-Jegher's syndrome a longer interval between laparotomies and a reduction in symptoms attributed to polyps.

Adolescent↗
PubMed1992

Unusual cases of benign stricture of the biliary tract.

Three patients, i.e., two adults and one child, with unusual benign stricture of the extrahepatic biliary duct are reported. Case 1 is a 63-year-old male with obstructive jaundice caused by a sclerotic vascular ring formed by the right hepatic artery and its branch. Case 2 is an 18-year-old male with obstructive jaundice due to stricture of the common bile duct caused by compression of enlarged collateral varicose veins, so-called cavernous transformation following extrahepatic obstruction of the portal vein. Case 3 is a 19-month-old boy complicated with biliary obstruction resulting from ischemic changes of the biliary duct at 10 months after extended right hepatectomy for mesenchymal hamartoma of the liver. The definitive diagnosis was made on the basis of imaging evaluations and the surgical findings. They have been free of jaundice and have shown an uneventful clinical course after the surgical interventions.

Adolescent↗
PubMed1992

A case of femoral hernia in a child.

A 9-year-old boy with a painless reducible swelling in the right groin was admitted to our hospital. The diagnosis of a right external inguinal hernia was made, but no inguinal hernial sac was found at operation. On further examination, the diagnosis of femoral hernia was confirmed. Radical operation for the femoral hernia was performed using McVay's procedure, and there has been no recurrence since the operation. In the Japanese literature, 25 cases of femoral hernias have been reported in children aged 1 month-9 year (average age, 4 years). The sex ratio of M:F was 2:3. Eleven cases were on the right side, 7 were on the left, and 5 were bilateral. The rate of irreducible femoral hernia was 48% (12/25 cases). Femoral hernias in children are very rare and often misdiagnosed as inguinal hernias. Correct diagnosis was made in only three cases (12%). Careful examination and awareness of the possibility of femoral hernia in children are very important when dealing with groin swelling in children.

Child↗
PubMed1989

Characterization of the bacterial population structure in an anaerobic-aerobic activated sludge system on the basis of respiratory quinone profiles.

Bacterial respiratory quinones were used as biomarkers for studying the bacterial population structure, especially the content of Acinetobacter species, in a laboratory-scale anaerobic-aerobic activated sludge system and in the standard aerobic system. All tested sludges contained both ubiquinone and menaquinone, with a molar ratio of about 1:0.5. High-performance liquid chromatography showed that ubiquinone with eight isoprene units (Q-8) was present as the predominant ubiquinone, Q-10 was the second most common type, and Q-9 and other homologs were minor components in the anaerobic-aerobic sludge and the standard aerobic sludge. Bacteriological examination indicated that, in both sludge systems, Q-8-containing bacteria constituted a large proportion of the aerobic heterotrophic bacterial flora, but only a few strains with Q-9 were found. These findings demonstrate that the population of Acinetobacter species, which contain Q-9 as the major quinone, is negligible in those environments. The present results suggest that the introduction of anaerobic conditions into the aerobic batch process has little influence on the bacterial community structure.

Aerobiosis↗
PubMedDate not supplied

Three-dimensional medical imaging display with computer-generated integral photography.

A 3-D display system for medical imaging by computer-generated integral photography (IP) has been developed. Real 3-D images are generated from 3-D medical images and displayed by simple structure. Each point in 3-D space is reconstructed by the convergence of rays from many pixels on the computer display through the lens array. Only the coordinate of the best point is computed for each pixel on the display. The locations of images projected within 40mm from the display were found to be less than 2.0mm in error. Projected images could be observed with motion parallax within 10 degrees from the front of the display.

Algorithms↗
PubMedDate not supplied

Development of a tracking method for image analysis of time-lapse deformation of trabecular structure in a human bone.

A new method to track the deformation of the trabecular structure in a human bone, which determines the dynamic characteristics of bone, was developed using elastic matching. This is a kind of image analysis. By comparing two 3-D images of the same bone taken at different times, this method computes displacement of any points in the bone during the period. This method makes it possible to demonstrate the behavior of the trabecular structure to mechanical loads and to estimate changes in the strength of a bone.

Bone Diseases↗