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Biomedical subjects

K Takakura

Publications and source records attributed to K Takakura.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1997

Morphological change in tumor endothelial cells induced by natural-type human tumor necrosis factor.

The effects of natural-type human tumor necrosis factor (nh-TNF) on tumor endothelial cells of experimental brain tumors were investigated electron microscopically. Tumor vessels with hypertrophic endothelial cells were observed 12 and 24 hr after an intralesional administration of 5,000 U of nh-TNF. Increased biosynthetic organelles such as the Golgi complex and rough endoplasmic reticulum were evident in the plump cytoplasms. These endothelial cells resembled those in high endothelial venules (HEV) functionally characterized by the high permeability of leukocytes. In addition, close interactions between these endothelial cells and leukocytes were observed. Our findings indicated that nh-TNF could promote the morphological change in tumor endothelial cells into HEV-like cells.

Animals↗
PubMed1997

Primary intracranial germ cell tumors: a clinical analysis of 153 histologically verified cases.

The authors analyzed 153 cases of histologically verified intracranial germ cell tumors. The histological diagnosis was germinoma in 63 patients (41.2%), teratoma in 30 (19.6%), and other types of tumors in 60 patients (39.2%). The patients were treated by a consistent policy of surgical removal with histological verification followed by radiation therapy with or without chemotherapy. The 10- and 20-year survival rates of patients with pure germinoma were 92.7% and 80.6%, respectively. The 10-year survival rates of patients with mature teratoma and malignant teratoma were 92.9% and 70.7%, respectively. Patients with pure malignant germ cell tumors (embryonal carcinoma, yolk sac tumor, or choriocarcinoma) had a 3-year survival rate of 27.3%. The mixed tumors were divided into three subgroups: 1) mixed germinoma and teratoma; 2) mixed tumors whose predominant characteristics were germinoma or teratoma combined with some elements of pure malignant tumors; and 3) mixed tumors with predominantly pure malignant elements. The 3-year survival rates were 94.1% for the first group, 70% for the second group, and 9.3% for the third group, and the differences were statistically significant. Twenty-six patients with malignant tumors received chemotherapy that consisted of cisplatin and carboplatin combinations with or without radiation therapy. However, chemotherapy was not significantly more effective than radiation therapy alone. From these treatment results, the authors classified tumors into three groups with different prognoses and proposed a treatment guideline appropriate for the subgroups.

Adolescent↗
PubMed1997

[Management of increased intracranial pressure in metastatic brain tumor].

Metastatic brain tumors generally accompany huge peripheral edema, and half of the cases have multiple lesions. Thus, one must manage the increased intracranial pressure (IICP). Ideally, local control of the tumor progression by surgical removal with radiation or radiosurgery is the best method to reduce IICP. We usually use a glyceol or steroids as medical treatment. Steroids are effective for peripheral edema, and we have used them for inoperable patients over the long term. One should estimate the condition of the primary lesion, systemic metastasis, and intracranial lesion in order to determine the therapy to assure patients the best quality of life.

Brain Neoplasms↗
PubMed1997

[Objective evaluation of selective peripheral denervation for spasmodic torticollis].

The authors evaluated the results of selective peripheral denervation (SPD) of posterior rami of the cervical spinal nerves and/or the accessory nerve for spasmodic torticollis. Five patients underwent seven operations in total and the results were evaluated with the modified Tsui's score which was used in the clinical trial of botulinum toxin (BTX) for torticollis in Japan. The preoperative score was 10.8 +/- 2.2 (mean +/- S.D.) and the postoperative score was 1.4 +/- 1.7. The score changes indicated the effects of the operation as "excellent" in four cases and "good" in one case. These results indicate that SPD is superior to BTX in terms of control of symptoms in spasmodic torticollis. After the initial operation, however, two patients showed the so-called "mole-hitting game phenomenon" in which normal muscles develop abnormal contraction after denervation of abnormal muscles. This forced us to perform the second operations. Although this phenomenon was first described in botulinum toxin treatment, this is probably the first report in surgically denervated cases.

Adult↗
PubMed1996

Management of huge pituitary adenomas.

Management of huge pituitary adenoma (more than 5 cm in diameter) is one of the most important issues on the treatment of pituitary tumors. We have analyzed the therapeutic modality and the result of our cases. From 1967 to 1983, 50 patients with huge adenoma (14.1%) out of a total 354 pituitary adenomas were surgically treated. The operative mortality was 25% for radical transcranial (TC) approach (10/40), 14% (1/7) for transsphenoidal (TS) approach and 0% (0/3) for combined two stage operations. From long-term follow-up, excellent prognoses were observed in only 44% of the patients treated by radical TC operation. After 1984, we have employed partial removal by TS surgery at the first stage, followed by reoperation by TS or TC surgery with or without radiotherapy or bromocriptine in case by case. Seventeen huge pituitary adenomas out of a total 700 pituitary adenomas were operated. There was no mortality nor major complications. The two stage operation with initial TS surgery is recommended for the management of huge pituitary adenomas.

Adenoma↗
PubMed1996

Solitary metastasis to the choroid plexus of the lateral ventricle. Report of three cases and a review of the literature.

Three cases of cancer metastasis to the choroid plexus of the lateral ventricle are reported. The metastases were from sigmoid colon cancer, renal cell carcinoma and pulmonary cancer, and were located in the trigone in two cases and the right inferior horn in one. Total removal was accomplished in all cases without any complications. In addition, eight reported cases of single brain metastasis to the choroid plexus of the lateral ventricle, including clinical and radiological features, are discussed. Peritumoral edema on computed tomographic (CT) scan or magnetic resonance (MR) imagining was found to be an important feature of metastasis developing at this site.

Aged↗
PubMed1996

Nitric oxide synthase induction and relaxation in lipopolysaccharide-treated gastric fundus muscle of rats.

To investigate whether L-arginine/nitric oxide (NO) pathway activated after treatment with lipopolysaccharide (LPS) could relax the gastric fundus smooth muscle, we made functional examinations and measured NO synthase activity by the conversion of radiolabelled L-arginine to L-citrulline in rat gastric fundus strips treated with LPS in vitro. L-arginine caused a relaxation of the mucosa-free gastric fundus strips which had been treated with LPS for 6 h in vitro and then contracted by PGF2alpha beforehand. This relaxation was partially reversed by N(G)-nitro-L-arginine (a nitric oxide synthase inhibitor) or methylene blue (a soluble guanylate cyclase inhibitor). Ca(2+)-independent NO synthase activity was induced after LPS-treatment. Co-incubation with LPS and cycloheximide for 6 h inhibited the relaxation to L-arginine and the induction of NO synthase. On the other hand, Ca(2+)-dependent NO synthase activity was decreased after LPS-treatment. These results strongly suggest that Ca(2+)-independent NO synthase is induced by endotoxin in the gastric fundus muscle, resulting in inhibition of the contractile response.

Animals↗
PubMed1996

Neuroimaging studies of postobliteration nidus changes in cerebral arteriovenous malformations treated by gamma knife radiosurgery.

BACKGROUND: Following radiosurgical treatment, the majority of patients with arteriovenous malformations (AVMs) are periodically examined by means of computed tomography (CT) and magnetic resonance imaging (MRI) to assess the attainment of nidus obliterations, as well as adverse radiation effects in the surrounding brain. However, few neuroimaging studies of the long-term results following complete obliterations, confirmed by angiography, have been published to date. METHODS: CT, MRI, magnetic resonance (MR) angiographic and angiographic images, obtained after angiographic confirmation of complete nidus obliteration, were reviewed in 11 AVM patients treated with gamma knife radiosurgery. The period between angiographic confirmation of nidus obliteration and these most recent examinations was 12-84 months (mean, 29 months). RESULTS: In ten patients who were assessed by CT, the obliterated nidus was shown to be isodense (eight cases). A significant time-related decrease in contrast enhancement was observed within 1 to 2 postobliteration years (five/seven cases). Eight patients were evaluated by MRI. On T1-weighted imaging, the nidus was shown to be hypointense (six cases) or a mixture of hypointense and isointense areas (two cases). On T2-weighted imaging, nidus intensity varied more than than observed on T1-weighted imaging, and time-related intensity increases were observed (two/seven cases). No flow-signal void was demonstrated in any of these cases. In four of the seven cases, in which serial postobliteration follow-up MRI studies were conducted, significant gadolinium enhancement persisted 3 years or more after obliteration (maximum of 7 years). No vascular abnormalities were demonstrated in seven patients who were assessed by conventional angiography and/or MR angiography. CONCLUSIONS: Radiosurgery-induced changes in a nidus may continue for several years after angiography has shown complete AVM obliteration.

Adolescent↗
PubMed1996

Polycystic ovaries: implications of diagnosis with MR imaging.

PURPOSE: To review the prevalence and clinical usefulness of a previously described magnetic resonance (MR) imaging finding of polycystic ovarian disease. MATERIALS AND METHODS: MR images of the uterine adnexa of 1,074 consecutive female patients suspected of having various gynecologic diseases were retrospectively reviewed for the presence of an MR imaging finding that has been described for polycystic ovarian disease. RESULTS: The prevalence of the previously described MR imaging finding of polycystic ovarian disease was 1.1% (12 of 1,074). Of the 12 patients, five had confirmed polycystic ovarian disease. Seven had no clinical or endocrinologic findings suggestive of polycystic ovarian disease. Six of these patients had endocrinologic findings related to ovarian dysfunction (n = 5) or had undergone hormonal therapy (n = 1). The other patient had vaginal agenesis but no clinical or endocrinologic evidence of abnormal ovarian function. CONCLUSION: The finding of multiple peripheral ovarian cysts at MR imaging may not be specific for polycystic ovarian disease.

Adnexa Uteri↗
PubMed1996

Gamma Knife radiosurgery for meningiomas: four cases of radiation-induced edema.

We review 48 cases of meningioma treated with Gamma Knife radiosurgery. The mean marginal dose was 15 Gy and the mean follow-up was 12 months. Follow-up computed tomography and magnetic resonance imaging showed tumor shrinkage in 19 cases, central necrosis in 1 case, loss of contrast enhancement in 1 case, and no change in 27 cases. We noted 4 cases of radiation-induced edema in supratentorial meningiomas.

Adult↗
PubMed1996

Is unchanged tumor volume after radiosurgery a measure of outcome?

We report three patients who underwent Gamma Knife radiosurgery for benign tumors (meningioma, neurinoma and hemangioblastoma), in whom an 'unchanged tumor volume' demonstrated by postirradiation follow-up neuroimaging could be regarded as a successful treatment results, as compared with preradiosurgery tumor growth. It is our view that unless significant tumor growth has been observed before radiosurgery, 'unchanged in size' after radiosurgery cannot be regarded as a successful treatment result. Because relatively few hemangioblastoma patients have been treated radiosurgically, this report emphasizes the course of one case with hemangioblastoma.

Adult↗
PubMed1996

Hemodynamic study of the anterior communicating artery.

BACKGROUND AND PURPOSE: The anterior communicating artery (ACoA) is a site of predilection for intracranial saccular aneurysms causing subarachnoid hemorrhage. ACoA aneurysms are frequently associated with an asymmetrical circle of Willis. In such cases, the ACoA is probably exposed to high hemodynamic stress caused by a considerable shunt flow across the ACoA to the distal segment of the contralateral anterior cerebral artery (ACA). In the present study, the flow pattern and flow-induced shear stress in the ACoA complex that may initiate aneurysmal lesions were studied under steady and pulsatile flow conditions. METHODS: Flow visualization was studied with dye injection and birefringent flow visualization in symmetrical and asymmetrical models of various sizes of ACoA. The distribution of wall shear stress was measured using an electrochemical method based on a diffusion-controlled reaction of ferricyanide ion to ferrocyanide ion at a platinum electrode embedded in the wall of the ACoA model. RESULTS: With equal flow rate (Reynolds number 150 to 600), vortical flow was formed in the mouth of the ACoA, and no cross flow through the ACoA was observed. The wall shear stress on the mid-wall of the ACoA was almost zero. However, as soon as the flow rate became unequal, a cross flow through the ACoA was observed. The stagnation point also appeared at the medial junction of the ACoA and ACA. The wall shear stress increased to a very high level at the wall of the ACoA and around the stagnation point. CONCLUSIONS: Geometric changes from the symmetrical to the asymmetrical ACoA develop higher shear stress on the ACoA than critical values and the stagnation point at the ACoA junction. A combination of these hemodynamic factors is considered to play an important role in initiation of aneurysm.

Blood Flow Velocity↗
PubMed1996

Antitumor activity of natural-type human tumor necrosis factor on experimental brain tumors in rats.

The effects of intralesional injection of newly synthesized natural-type human tumor necrosis factor (nh-TNF) on experimental brain tumors in rats were investigated. The repeated injection of 5,000 U of nh-TNF into the tumor resulted in the prolongation of the survival time of the rats. More than half of the nh-TNF treated tumors were red, and were characterized by histopathological features of marked congestion of tumor vessels. Fibrin formations were also found in the tumor vessels. These histological findings were not observed in the control tumors. Furthermore, coagulative necrosis was observed in the center of some reddish tumors. Leukocytes adhering to vascular endothelium and infiltration of the leukocytes were also observed in the tumors of nh-TNF treated rats. In the immunohistochemical examination, these infiltrated cells were primarily polymorphonuclear leukocytes and macrophages. Expression of intercellular adhesion molecule-1 (ICAM-1) increased on the tumor endothelial cells after the administration of nh-TNF. These results suggest that repeated injection of nh-TNF has a therapeutic effect on brain tumors through its extensive influences on tumor vasculature.

Animals↗
PubMed1996

Inhibin alpha and beta A subunit messenger ribonucleic acids expression in human pituitary adenomas: studies by quantitative reverse transcription-polymerase chain reaction.

Inhibin alpha and beta A subunit messenger ribonucleic acid (mRNA) levels were measured quantitatively by reverse transcription-polymerase chain reaction (RT-PCR) in human pituitary adenomas. The inhibin alpha subunit mRNA levels were undetectably low in cultured adenoma tissues, but beta A mRNA were 0.383 +/- 0.074 in 3 GH adenomas, 0.672 +/- 0.140 in 3 prolactinomas and 0.957 +/- 0.414 molecules/cell in 3 non-functioning adenomas. The addition of 10(-8) M activin A decreased the beta A mRNA levels within 4 h in 1 of 3 GH adenomas, 2 of 3 prolactinomas and 2 of 3 non-functioning adenomas, though the decreases were not statistically significant. The results showed an abundance of beta A subunit mRNA compared with alpha subunit mRNA in all human pituitary adenomas and a local role for activin in its own production through inhibin beta A mRNA subunit expression.

Adenoma↗
PubMed1996

Demonstration of activin in normal pituitary and in various human pituitary adenomas by immunohistochemistry.

Inhibins and activins have been known to modify the secretion of various pituitary hormones. To study whether inhibins and activins are present in human pituitary tissues, immunohistochemical studies with antisera to activin A and inhibin alpha subunit were performed on 9 human pituitary adenoma tissue specimens and one sample of normal pituitary tissue adjacent to one adenoma. Activin immunoreactivities were demonstrated in the cytoplasms of one GH and one PRL and two non-functioning adenomas and one normal pituitary tissue, but they were negative in one PRL, one ACTH, one FSH and two non-functioning adenomas. Thus, the presence and absence of activin in the same type of adenoma in regard to hormone production, suggested that the difference in immunostaining simply reflected the difference in the activin concentration. In contrast to this, inhibin alpha subunit immunoreactivity was not found in any of the tissues studied. These data suggested a local synthesis of activin in the normal pituitary as well as various kinds of pituitary adenoma tissues and its local role in the human pituitary gland.

Activins↗