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Yoshimasa Mori

Publications and source records attributed to Yoshimasa Mori.

11 recordsLinked to original sources
PubMed2006

Stereotactic imaging for radiosurgery: localization accuracy of magnetic resonance imaging and positron emission tomography compared with computed tomography.

Computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) provide complementary information for treatment planning in stereotactic radiosurgery. We evaluated the localization accuracy of MRI and PET compared with CT. Two kinds of phantoms applicable to the Leksell G stereotactic skull frame (Elekta, Tokyo) were developed. Deviations of measured coordinates at target points (x = 50, 100, 150; y = 50, 100, 150) were determined on different axial planes (z = 30-140 for MRI and CT study and Z = 50-120 for PET and CT study). For MRI, the deviations were no more than 0.8 mm in each direction. For PET, the deviations were no more than 2.7 mm. For both imaging modalities studied, accuracy was at or below the imaging resolution (pixel size) and should be considered useful for clinical stereotactic planning purposes.

Fluorodeoxyglucose F18↗
PubMed2006

Stereotactic radiosurgery as a salvage treatment for recurrent epipharyngeal carcinoma.

Fourteen patients with recurrent epipharyngeal carcinoma (EPC) were treated by gamma knife stereotactic radiosurgery. The tumor volume ranged from 0.3 to 80 ml (median 18.9 ml). Treatment was done with a tumor margin dose of 10-27 Gy (median 15 Gy). The median follow-up period was 15 months (range 2-47 months). Ten patients were alive and 4 were dead at the end of the follow-up period. In 6 patients (43%), the tumor disappeared or decreased in size until the end of the follow-up period. In 2 (14%), the tumor remained unchanged in size. In 6 (43%), the tumor showed regression initially but was enlarged later. A second radiosurgery was performed in 4 of those 6 cases and the tumor decreased in size again in 3 of them. Thus, the overall control rate of local tumor was 79% (11/14). In selected patients with recurrent EPC, stereotactic radiosurgery can be considered as a salvage treatment producing local control.

Adult↗
PubMed2006

Stereotactic radiosurgery as a salvage treatment for recurrent skull base adenoid cystic carcinoma.

Twelve patients (15 lesions) with recurrent skull base adenoid cystic carcinoma (ACC) were treated by Gamma Knife stereotactic radiosurgery (SRS). The tumor volume ranged from 2 to 103 ml (median 15 ml). Treatment was prescribed at the 40-60% isodose line and ranged from 10 to 18 Gy (median: 13.0 Gy). The median follow-up period was 18 months (range 3-55). Six patients were alive and 6 dead at the end of the follow-up period. Only 1 patient died from local tumor recurrence. Ten among 15 tumors treated by SRS decreased in size until the end of the follow-up period or the patients' death. Three remained unchanged in size. Two tumors initially regressed but then increased in size. In selected patients with recurrent skull base ACC, SRS can be considered as a salvage treatment with good local control.

Adolescent↗
PubMed2006

Malignant lymphoma arising in the cerebral parenchyma adjacent to a parasagittal meningioma.

A 70-year-old woman with an asymptomatic parasagittal meningioma had been under observation with follow-up imaging for 2 years. She gradually developed motor weakness in the left hand. Magnetic resonance (MR) imaging disclosed a newly developed well-enhanced area in the cerebral parenchyma adjacent to the stable original meningioma. The new lesion was enhanced more intensely and less well demarcated. We suspected that the meningioma had enlarged into the brain parenchyma, although MR imaging suggested a border between the extra-axial and intra-axial portions. Craniotomy was performed. Two separate tumors were identified with quite different histological features. The extra-axial tumor was identified as benign transitional meningioma and the intra-axial tumor as diffuse large cell type malignant lymphoma. Immunostaining revealed the lymphoma had B cell origin. After surgical resection, stereotactic radiosurgery was performed for the residual lymphoma. The original site of the lymphoma remained free from relapse, but another lesion developed in the right frontal lobe 3 months later and chemotherapy was performed. The main concern for follow-up imaging of asymptomatic meningioma without surgical resection is growth of the meningioma. However, development of new different tumors is possible, although thought to be rare.

Aged↗
PubMed2006

[Radiosurgery].

Despite the abundant reports on clinical efficacy of radiosurgery (high-dose focused radiation) for the treatment of brain tumors, vascular malformations, and functional disease, limited histological information is available after treatment that might allow a better understanding of the response of the target and the surrounding brain to the delivered radiation. The use of animal models provides the opportunity to clarify these relationships and answer several other key questions arising in clinical practice. In this paper reported series of animal studies on radiosurgery were reviewed.

Animals↗
PubMed2005

Long-term outcomes in patients with vestibular schwannomas treated using gamma knife surgery: 10-year follow up.

OBJECT: Gamma knife surgery (GKS) has been a safe and effective treatment for vestibular schwannomas in both the short and long term, although less is known about long-term outcomes in the past 10 years. The aim of this study was to clarify long-term outcomes in patients with vestibular schwannomas treated using GKS based on techniques in place in the early 1990s. METHODS: Eighty patients harboring a vestibular schwannoma (excluding neurofibromatosis Type 2) were treated using GKS between May 1991 and December 1993. Among these, 73 patients were assessed; seven were lost to follow up. The median duration of follow up was 135 months. The mean patient age at the time of GKS was 56 years old. The mean tumor volume was 6.3 cm3, and the mean maximal and marginal radiation doses applied to the tumor were 28.4 and 14.6 Gy, respectively. Follow-up magnetic resonance images were obtained in 71 patients. Forty-eight patients demonstrated partial tumor remission, 14 had tumors that remained stable, and nine demonstrated tumor enlargement or radiation-induced edema requiring resection. Patients with larger tumors did not fare as well as those with smaller lesions. The actuarial 10-year progression-free survival rate was 87% overall, and 93% in patients with tumor volumes less than 10 cm3. No patient experienced malignant transformation. CONCLUSIONS: Gamma knife surgery remained an effective treatment for vestibular schwannomas for longer than 10 years. Although treatment failures usually occurred within 3 years after GKS, it is necessary to continue follow up in patients to reveal delayed tumor recurrence.

Adolescent↗
PubMed2005

Long-term results of gamma knife surgery for growth hormone-producing pituitary adenoma: is the disease difficult to cure?

OBJECT: The authors conducted a study to determine the long-term results of gamma knife surgery for residual or recurrent growth hormine (GH)-producing pituitary adenomas and to compare the results with those after treatment of other pituitary adenomas. METHODS: The series consisted of 67 patients. The mean tumor diameter was 19.2 mm and volume was 5.4 cm3. The mean maximum dose was 35.3 Gy and the mean margin dose was 18.9 Gy. The mean follow-up duration was 63.3 months (range 13-142 months). The tumor resolution rate was 2%, the response rate 68.3%, and the control rate 100%. Growth hormone normalization (GH < 1.0 ng/ml) was found in 4.8%, nearly normal (< 2.0 ng/ml) in 11.9%, significantly decreased (< 5.0 ng/ml) in 23.8%, decreased in 21.4%, unchanged in 21.4%, and increased in 16.7%. Serum insulin-like growth factor (IGF)-1 was significantly decreased (IGF-1 < 400 ng/ml) in 40.7%, decreased in 29.6%, unchanged in 18.5%, and increased in 11.1%, which was almost parallel to the GH changes. CONCLUSIONS: Gamma knife surgery was effective and safe for the control of tumors; however, normalization of GH and IGF-1 secretion was difficult to achieve in cases with large tumors and low-dose radiation. Gamma knife radiosurgery is thus indicated for small tumors after surgery or medication therapy when a relatively high-dose radiation is required.

Adenoma↗
PubMed2005

Long-term results of gamma knife surgery for the treatment of craniopharyngioma in 98 consecutive cases.

OBJECT: The authors analyzed the long-term outcomes of gamma knife surgery (GKS) for residual or recurrent craniopharyngiomas after microsurgery and the effects of dose reduction. METHODS: A total of 107 patients with craniopharyngiomas were treated with GKS at Komaki City Hospital during the past 12 years, and 98 patients were followed up for 6 to 148 months (mean 65.5 months). The mean tumor diameter and volume were 18.8 mm and 3.5 ml, respectively. These tumors were treated with a maximal dose of 21.8 Gy and a tumor margin dose of 11.5 Gy by using a mean of 4.5 isocenters. Final overall response rates were as follows: complete response 19.4%, partial response 67.4%, tumor control 79.6%, and tumor progression 20.4%. Reducing the tumor margin dose resulted in decreased therapeutic response and increased tumor progression, although the rate of visual and pituitary function loss also decreased. Among the factors examined, age (for adults) and the nature of the tumor (cystic or mixed) were statistically significant favorable and unfavorable prognostic factors, respectively. The actuarial 5- and 10-year survival rates were 94.1 and 91%, respectively. The progression-free survival rates were 60.8 and 53.8%, respectively. Patient outcomes were reportedly excellent in 45 cases, good in 23, fair in four, and poor in three; 16 patients died. Deterioration both in vision and endocrinological functions were documented as side effects in six patients (6.1%). CONCLUSIONS: Stereotactic GKS is safe and effective, in the long term, as an adjuvant or boost therapy for residual or recurrent craniopharyngiomas after surgical removal and has minimal side effects. New treatment strategies must be devised to manage these tumors.

Adolescent↗
PubMed2003

[Gamma knife radiosurgery].

Gamma knife radiosurgery has become a new treatment modality in the field of neurosurgery since the first gamma knife was brought into Japan in 1990. Advances in applications of new indications and long-term results have been continued to evolve during the past 12 years. Based on the experience of more than 4,500 cases treated by gamma knife at Komaki City Hospital, long-term results of arteriovenous malformations (AVMs), metastatic brain tumors, acoustic neurinomas, meningiomas and trigeminal neuralgias are presented. Radiosurgery has become a novel treatment modality, especially for AVM, acoustic neurinoma and meningioma, which were once only treatable by conventional surgery, and shows a high cure rate in AVM cases and high control rate in benign tumors without major complications. The effects of radiosurgery for metastatic brain tumors have been thought to be superior to fractionated radiotherapy due to high response and control rates, and patients showed improved quality of life although no prolongation of the life span was obtained. Gamma knife treatment for trigeminal neuralgia has been shown to be effective and less invasive than microvascular decompression, and is useful for cases resistant to conventional therapies and as an initial treatment as well.

Brain Neoplasms↗
PubMed2002

Radiosurgery for residual or recurrent nonfunctioning pituitary adenoma.

OBJECT: Nonfunctioning pituitary adenomas comprise approximately 30% of all pituitary tumors. The purpose of this retrospective study is to evaluate the efficacy and role of gamma knife radiosurgery (GKS) in the management of residual or recurrent nonfunctioning pituitary adenomas. METHODS: A review was conducted of the data obtained in 42 patients who underwent adjuvant GKS at the University of Pittsburgh between 1987 and 2001. Prior treatments included transsphenoidal resection, craniotomy and resection, or conventional radiotherapy. Endocrinological, ophthalmological, and radiological responses were evaluated. The duration of follow-up review varied from 6 to 102 months (mean 31.2 months). Fifteen patients were observed for more than 40 months. The mean radiation dose to the tumor margin was 16 Gy. Conformal radiosurgery planning was used to restrict the dose to the optic nerve and chiasm. Tumor control after GKS was achieved in 100% of patients with microadenomas and 97% of patients with macroadenomas. Gamma knife radiosurgery was equally effective in controlling adenomas with cavernous sinus invasion and suprasellar extension. No patient developed a new endocrinological deficiency following GKS. One patient's tumor enlarged with an associated decline in visual function. Another patient experienced a deterioration of visual fields despite a decrease in tumor size. CONCLUSIONS: Gamma knife radiosurgery can achieve tumor control in virtually all residual or recurrent nonfunctioning pituitary adenomas. Dose sparing facilitates tumor management even when the adenoma is close to the optic apparatus or invades the cavernous sinus.

Adenoma↗