Single isocenter dynamic conformal arcs-based radiosurgery for brain metastases: Dosimetric comparison with Cyberknife and clinical investigation.

Purpose: To compare the dosimetric quality of automatic multiple brain metastases planning (MBM) with that of Cyberknife (CK) based on the clinical tumor condition, such as the tumor number, size, and location. Methods: 76 treatment plans for 46 patients treated with CK were recalculated with the MBM treatment planning system. Conformity index (CI), homogeneity index (HI), gradient index (GI), lesion underdosage volume factor (LUF), healthy tissue overdose volume factor (HTOF), geometric conformity index (g) and mean dose to normal organs were compared between CK and MBM for tumor number, size, shape and distance from the brainstem or chiasm. Results: The results showed that the mean brain dose was significantly smaller in MBM than CK. CI did not differ between MBM and CK; however, HI was significantly more ideal in CK (p = 0.000), and GI was significantly smaller in MBM (P = 0.000). LUF was larger in CK (p = 0.000) and HTOF and g was larger in MBM (p = 0.003, and 0.012). For single metastases, CK had significantly better HTOF (p = 0.000) and g (p = 0.002), but there were no differences for multiple tumors. Brain dose in MBM was significantly lower and CI was higher for tumors < 30 mm (p = 0.000 and 0.000), whereas HTOF and g for tumors < 10 mm were significantly smaller in CK (p = 0.041 and p = 0.016). Among oval tumors, brain dose, GI and LUF were smaller in MBM, but HTOF and g were smaller in CK. There were no particular trends for tumors close to the brainstem, but HTOF tended to be smaller in CK (0.03 vs. 0.29, p = 0.068) for tumors inside the brainstem. Conclusions: MBM can reduce the brain dose while achieving a dose distribution quality equivalent to that with CK.

19-core MCF transmission system using EDFA with shared core pumping coupled via free-space optics.

We report the development of a space division multiplexed (SDM) transmission system consisting of a 19-core fiber and 19-core Erbium-doped fiber amplifier (EDFA). A new 19-core fiber with an improved core arrangement was employed to achieve a low aggregated inter-core crosstalk of -42 dB at 1550 nm over 30 km. The EDFA uses shared free-space optics for pump beam combining and isolation, thus is SDM transparent and has some potential for cost reduction. 19.6 dB to 23.3 dB gain and 6.0 dB to 7.0 dB noise figure were obtained for each SDM channel at 1550 nm. System feasibility for SDM transmission over 1200 km was demonstrated with 100 Gb/s PDM-QPSK signals.

Super-Nyquist-WDM transmission over 7,326-km seven-core fiber with capacity-distance product of 1.03 Exabit/s · km.

We show super-Nyquist-WDM transmission technique, where optical signals with duobinary-pulse shaping can be wavelength-multiplexed with frequency spacing of below baudrate. Duobinary-pulse shaping can reduce the signal bandwidth to be a half of baudrate while controlling inter-symbol interference can be compensated by the maximum likelihood sequence estimation in a receiver. First, we experimentally evaluate crosstalk characteristics as a function of channel spacing between the dual-channel DP-QPSK signals with duobinary-pulse shaping. As a result, the crosstalk penalty can be almost negligible as far as the ratio of baudrate to frequency spacing is maintained to be less than 1.20. Next, we demonstrate 140.7-Tbit/s, 7,326-km transmission of 7 × 201-channel 25-GHz-spaced super-Nyquist-WDM 100-Gbit/s optical signals using seven-core fiber and full C-band seven-core EDFAs. To the best of our knowledge, this is one of the first reports of high-capacity transmission experiments with capacity-distance product in excess of 1 Exabit/s · km.

110.9-Tbit/s SDM transmission over 6,370 km using a full C-band seven-core EDFA.

We confirm the feasibility of 100-Tbit/s-class trans-oceanic SDM transmission. Using seven-core fiber spans with seven-core full C-band EDFAs, 7 × 264-channel quasi-Nyquist-WDM 60-Gbit/s PDM-QPSK signals are transmitted over 6,370 km.

Investigation on multi-core fibers with large Aeff and low micro bending loss.

To realize large effective area (Aeff) multi-core fibers (MCFs), the design to suppress the cross-talk and the influence of the cladding diameter on the micro bending loss were investigated. As a result, the MCFs with large Aeff over 100 µm(2) and low micro bending loss were successfully fabricated. The results indicate the importance of fiber design to realize large Aeff MCFs including fiber diameters, which largely affect the micro bending loss property. Additionally, MCF with large Aeff, low attenuation loss and suppressed cross-talk was successfully realized by optimizing the fiber design. The cross-talk properties could be estimated by the simulation based on the coupling power theory taking the influences of the longitudinal fluctuation of core diameter into account.

Reversibility of cognitive disorder after treatment of dural arteriovenous fistulae.

INTRODUCTION: Dural arteriovenous fistulae (DAVF) occasionally lead to cognitive disorders whose reversibility after DAVF treatment remains unclear. We studied changes on pre- and post-treatment magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) scans in ten patients with cognitive disorder due to DAVF. METHODS: We studied the symptoms, pre- and post-treatment MRI scans, SPECT findings, and mini-mental state examination (MMSE) and treatment results in ten patients with cognitive disorder due to DAVF. They were divided into two groups; the post-treatment MMSE score exceeded 25 points in group 1 (n = 6) and was lower than 24 points in group 2 (n = 4). RESULTS: In the six group 1 patients, pretreatment diffusion-weighted images (DWI) showed hyperintense areas, and SPECT scans demonstrated the preservation of vasoreactivity after acetazolamide challenge. In the four group 2 patients, pretreatment SPECT demonstrated hypoperfusion areas that coincided with the hyperintense areas seen on DWI; there were areas with marked disturbance in vasoreactivity. The post-treatment MMSE score in groups 1 and 2 improved by 13.7 +/- 2.4 and 3.8 +/- 1.0 points, respectively; the difference was significant at p < 0.01. CONCLUSION: In patients with cognitive disorder due to DAVF, the preservation of vasoreactivity on SPECT after acetazolamide challenge indicates that their cognitive disorder may be reversible by DAVF treatment.

Design of all-solid leakage channel fibers with large mode area and low bending loss.

We investigate a novel design for all-solid large mode area (LMA) leakage channel fibers (LCFs) for high-power Yb-doped fiber lasers and amplifiers, based on a single down-doped-silica rod ring surrounding a seven-cell pure-silica core, aiming for effectively single-mode behavior and low bending loss characteristics. Through detailed numerical simulations based on the finite element method (FEM), we find that the proposed all-solid LMA-LCFs, having a seven-cell core and two different sizes of down-doped rods, can achieve sufficient differential mode loss and much lower bending loss, as compared with a previously-reported LCF with a one-cell core and six large down-doped-silica rods.

Raman amplification characteristics of As2Se3 photonic crystal fibers.

We present the dispersion and Raman amplification characteristics of As2Se3 photonic crystal fibers (PCFs). We compare the gain characteristics with conventional As2Se3 fibers and find that the Raman gain efficiency in PCFs can be improved by a factor of more than 4. This allows us to either use a small length of the fiber or to use the low pump power to attain similar gain characteristics. Numerical simulations reveal that a peak gain of 10 dB can be achieved in a 1.1 m long PCF when it is pumped at 1.5 microm in wavelength with an input power of 500 mW.

Treatment and prognosis of brain metastases from gynecological cancers.

Brain metastases from gynecological cancers were retrospectively investigated in 18 patients who were treated between 1985 and 2006. Six patients received surgical resection followed by radiotherapy, and 12 patients received only radiotherapy. The median survival for all patients was 4.1 months (range 0.7-48.2 months), and the actuarial survival rates were 11% at both 12 months and 24 months. Univariate analysis showed that treatment modality, extracranial disease status, total radiation dose, number of brain metastases, and Karnofsky performance status (KPS) all had statistically significant impacts on survival. Two patients survived for more than 2 years, and both had single brain metastasis, inactive extracranial disease, 90-100% KPS, and were treated with surgical resection followed by radiotherapy. Improvements in neurological symptoms were observed in 10 of the 12 patients treated with palliative radiotherapy, with median duration of 3.1 months (range 1.5-4.5 months). The prognoses for patients with brain metastases from gynecological cancers were generally poor, although selected patients may survive longer with intensive brain tumor treatment. Palliative radiotherapy was effective in improving the quality of the remaining life for patients with unfavorable prognoses.

Cognitive function of patients with brain tumor in pre- and postoperative stage.

BACKGROUND: Nobody knows whether cognitive dysfunction affects survival. Furthermore, it is unknown whether the dysfunction is caused by the tumor itself or by its treatment. METHODS: Patients with 20 gliomas (LGG, 7; MG, 13 [AG, 4; GM, 9]) in the right brain (nondominant) and 11 gliomas (LGG, 1; MG, 10 [AG, 6; GM, 4]) in the left brain (dominant) were studied. Thirty-four patients with meningioma were also studied. Cognitive function was evaluated by the 3MS examination, and propriety of radical resection of tumor was reviewed. RESULTS: Cognitive function pre-Op and post-Op was normal in patients with LGG and MGs in the right brain but decreased before an Op in all patients with MG in the left brain, and they did not normalize after Op. In patients with MG in left brain, the test of temporal and spatial orientation, first recall, similarities, 4-legged animals, mental reversal, and writing decreased after Op. Cognitive hypofunction before or after Op did not correlate with tumor malignancy and degree of tumor resection. CONCLUSION: Firstly, radical Op should aim at improvement of cognitive function for patients with glioma in the right brain, and for patients with glioma in the left brain, QOL should be thought about without expecting improvement of cognitive function. Secondly, improvement of cognitive function cannot be anticipated in patients with meningioma in the left brain. Aged patients older than 75 years require carefulness in Op. Then, damage of the cingulated gyrus and corpus callosum should be avoided in the left brain. This study emphasizes that clinicians should be careful in the evaluation of cognitive function in glioma and meningioma treatment.

Treatment and prognosis of brain metastases from breast cancer.

BACKGROUND: To analyze retrospectively the results of treatments for patients with brain metastases from breast cancer. MATERIALS AND METHODS: The records of 65 breast cancer patients with brain metastases who were treated between 1985 and 2005 were reviewed. For brain metastases, 11 patients (17%) were treated with surgical resection followed by radiotherapy, and the remaining 54 patients were treated with radiotherapy alone. Systemic chemotherapy was also administered to 11 patients after brain radiotherapy. RESULTS: The overall median survival for all patients was 6.1 months (range, 0.4-82.2 months). In univariate analysis, treatment modality, Karnofsky performance status (KPS), administration of systemic chemotherapy, extracranial disease status and total radiation dose each had significant impact on overall survival, and in multivariate analysis, treatment modality, KPS and administration of systemic chemotherapy were significant prognostic factors. Eight patients survived for more than 2 years after the diagnosis of brain metastases, and all these patients were treated with surgical resection and/or systemic chemotherapy in addition to radiotherapy. For the 45 patients treated with palliative radiotherapy (without systemic chemotherapy), the improvements in neurological symptoms were observed in 35 patients (78%), with the median duration of improvement of 3.1 months (range, 1.5-4.4 months). CONCLUSIONS: The prognoses for patients with brain metastases from breast cancer were generally poor, although selected patients may survive longer with intensive brain tumor treatment, such as surgical resection and/or systemic chemotherapy in addition to brain radiotherapy. For patients with unfavorable prognoses, palliative radiotherapy was effective in improving the quality of the remaining lifetime.

Cell cycle checkpoint and apoptosis induction in glioblastoma cells and fibroblasts irradiated with carbon beam.

This study was conducted in order to evaluate the cytotoxicity of high linear-energy-transfer (LET) ionizing radiation (IR) on glioblastoma cells and fibroblasts using different modes of cell inactivation assays. Two human glioblastoma cell lines with or without p53-mutation, and fibroblasts were used as materials. Gamma rays and 290 MeV/u carbon beams with LET values of 20, 40, 80 keV/mum were used. To evaluate cell inactivation, we used colony formation assay, morphological detection of apoptosis, and flow-cytometry. Serial expressions of p53 and p21 were analyzed by immunoblotting. High-LET IR reduced the reproductive potency of these cells to identical levels in spite of differences in gamma-sensitivity, and yield of cell death correlated to LET values. A p53-wild-type glioblastoma cell line demonstrated a higher yield of apoptosis than other cell lines, whereas fibroblasts hardly displayed any cell death indicating senescence-like growth arrest even after high LET IR. A p53-mutant tumor cell line demonstrated very low yield of cell death with prominent G2/M arrest. Results of radiosensitivity differ according to what mode of cell inactivation is selected. While fibroblasts depend on G1 block after IR, G2/M blocks may play crucial roles in the radioresistance of p53-mutant glioblastoma cells.

Design of single-moded holey fibers with large-mode-area and low bending losses: the significance of the ring-core region.

One of the major trends in optical fiber science is to be able to obtain fibers with large-mode-area (LMA), optimized for various applications such as high power delivery, fiber amplifiers, and fiber lasers. In order to ensure the high beam quality and the ultimate controllability of the damage threshold in the fiber's material, it is required to have a LMA property and of course to operate in a single mode fashion. While the conventional fibers have some difficulties in providing simultaneously LMA, single mode operation, as well as low macro-bending loss characteristics, all-silica holey fibers are highly attractive candidates for realizing LMA single-mode fibers with low bending losses. In this paper, we present a novel type of effectively single-mode holey fibers with effective mode area of about 1400 mum(2), small allowable bending radius as small as 5 cm, good beam quality factor of 1.15, and high confinement losses exceeding 1 dB/m for the higher-order mode at 1.064-mum wavelength.

Hyperfractionated radiotherapy and multi-agent chemotherapy (procarbazine, ACNU and vincristine) for high-grade gliomas: a prospective study.

AIM: To evaluate the feasibility, efficacy and toxicity of hyperfractionated radiotherapy and multi-agent chemotherapy, including procarbazine, nimustine (ACNU) and vincristine, in adults with high-grade gliomas. MATERIALS AND METHODS: Radiotherapy was administered using two fractions per day of 1.2 Gy to a total dose of 72 Gy. The chemotherapy consisted of procarbazine (90 mg/m2 orally, days 1 to 14), ACNU (80 mg/m2 intravenously, day 1) and vincristine (0.5 mg/m2 intravenously, days 1 and 8) and was administered during and after radiotherapy, up to a maximum of four courses. RESULTS: From September 1997 to August 1999, a total of ten patients (five with glioblastoma and five with grade 3 gliomas) were enrolled. All ten patients were able to complete a total dose of 72 Gy hyperfractionated radiotherapy with one course of concurrent chemotherapy. Of eight assessable patients, three (38%) had an objective response, comprising two CR and one PR. The median time to progression was 10.7 months and the median survival time of all patients was 15.0 months. Although grade 4 leukopenia and grade 4 thrombocytopenia occurred in 10% and 10% of all patients, respectively, these were transient and no patients developed neutropenic fever or intracranial hemorrhage. No serious non-hematological or late toxicities occurred. CONCLUSION: Hyperfractionated radiotherapy and multi-agent chemotherapy using procarbazine, ACNU and vincristine is safe and well tolerated for high-grade gliomas.

Bending-insensitive single-mode hole-assisted fibers with reduced splice loss.

We propose and demonstrate a novel type of bending-insensitive single-mode hole-assisted fiber that has a doped core and two layers of holes with two different airhole diameters. The fiber has a 9.3 microm mode field diameter, a bending loss of 0.011 dB/turn at 1.55 microm for a bending diameter of 10 mm, and a cutoff wavelength below 1.1 microm. The fiber can be fusion spliced to a conventional single-mode fiber with low loss.

Design and characterization of single-mode holey fibers with low bending losses.

As the fiber-to-the-home network construction increased, optical fiber cables are demanded to be easier to handle and require less space. Under this situation, a single mode fiber (SMF) permitting small bending radius is strongly requested. In this paper, we propose and demonstrate a novel type of bending-insensitive single-mode holey fiber that has a doped core and two layers of holes with different air-hole diameters. The fiber has a mode field diameter of 9.3 microm at 1.55 microm and a cutoff wavelength below 1.1 microm, and shows a bending loss of 0.011 dB/turn at 1.55 microm for a bending radius of 5 mm and a low splice loss of 0.08 dB per fusion-splicing to a conventional SMF.

Endlessly single-mode holey fibers: the influence of core design.

In this paper we evaluate the cut-off properties of holey fibers (HFs) with a triangular lattice of air holes and the core formed by the removal of a single (HF1) or more air holes (HF3 and HF7). With the aid of finite-element simulations we determine the single-mode and multi-mode phases and also find the air hole diameters limiting the endlessly single-mode regime. From calculations of V and W parameters we find that in general HF1 is less susceptible to longitudinal non-uniformities compared to the other designs for equivalent effective areas. As an example we illustrate this general property for the particular case of a macro-bending induced loss.