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This paper presents a dynamic analysis of a hybrid serial-parallel robot. The hybrid serial-parallel robot has the features of both high rigidity of the parallel manipulator and wide workspace of the serial manipulator. Thanks to these advantages, the robot is appropriate for multi-tasking machining such as milling, drilling, deburring and grinding. To operate the robot at a high speed, a dynamic analysis on the motion and dynamic load is required. For the analysis, a dynamic analysis program was developed using multi-body dynamics. Using the developed analysis program, the joint reaction force and driving force of the actuator were analyzed. The results can be used in designing a hybrid serial-parallel robot to achieve high positioning accuracy and operation at a high speed.

The antiarrhythmic clofilium is an efficient blocker of hERG1 potassium channels that are strongly expressed in the heart. Therefore, derivatives of clofilium that emit positrons might be useful tools for monitoring hERG1 channels in vivo. Fluoro- clofilium (F-clofilium) was synthesized and its channel-blocking properties were determined for hERG1 and hEAG1 channels expressed in HEK?293 cells and in Xenopus oocytes. When applied extracellularly in the whole-cell patch-clamp configuration, F-cloflium exhibited a slower onset of block when compared with clofilium, presumably owing to its lower membrane permeability. When applied in the inside-out configuration at the intracellular membrane side, it blocked hEAG1 channels almost as efficiently as clofilium (IC50 1.37 nM and 0.83 nM, respectively). Similar results were obtained for hERG1, showing F-clofilium is a potent hERG1 and hEAG1 channel blocker once it has reached the intracellularly accessible target site at the channel. Using the (18)F-labeled analog we studied the in vivo binding and distribution of F-clofilium in mice and a dog. Greatest activity was found in kidneys and bones. A small but significant enrichment of activity in the dog myocardium known for its expression of cERG1 channels allowed to depict the myocardium of a living dog by PET. Thus, F-clofilium is a useful tool for imaging hERG channels in living organisms.

Background Mycosis fungoides palmaris et plantaris (MFPP), characterized by hyperkeratotic patches or plaques confined to the palms and soles, is rare and easy to misdiagnose because of the clinical similarity to psoriasis, cutaneous inflammatory dermatoses, and dermatophytic infections. The literature about MFPP mostly consists of case reports with short-term follow-up. Objective Our purpose was to evaluate the clinicopathologic features, T-cell receptor (TCR) gene rearrangement findings, and prognosis of MFPP. Patients and methods This retrospective study has been reviewed in the clinicopathologic, TCR γ gene rearrangement findings and follow-up study of 12 patients with MFPP. Results The duration of diseases ranged from 9 months to 25 years with a mean duration of 5.3 years. Clinically, hyperkeratotic patches and plaques were observed in all cases, with 6 cases having developed on the palms and soles and 6 cases on the palms only. In TNM classifications, all cases were confined to T1N0M0 (stage IA) showing an early stage of mycosis fungoides (MF). Histopathologic findings revealed marked hyperkeratosis, parakeratosis with plasma, epidermotropism, convoluted lymphocytes, haloed lymphocytes, dense infiltrate of lymphocytes in all 12 cases (100%), Pautrier's microabscess in 9 cases (75%), a wiry bundle of collagen in 11 cases (91.7%) and basilar epidermotropism in 3 cases (25%). TCR γ gene rearrangement was performed except for one case and monoclonality was detected in 10 of 11 cases. In the comparison group with cutaneous inflammatory dermatoses, all cases showed polyclonality. Treatment was done with Re-PUVA (acitretin and PUVA), ultraviolet A1, as well as systemic acitretin and methotrexate. Most patients showed a good response. In the follow-up study of 9 cases for a mean period of 47.6 months, only one patient's skin lesions were extended to the trunk and face, but the other patients had no sign of extracutaneous involvement. Limitations These results were obtained from patients with MFPP in Korea. A cooperative study with other ethnic groups will be helpful. Conclusions If a patient has recalcitrant palmoplantar dermatosis, MFPP should be suspected and histopathologic studies with TCR gene rearrangement should be done for early diagnosis of MFPP.

A new post-processing approach based on "edge flow" and curvelet transform is proposed for the suppression blocking artifacts in block discrete cosine transform (BDCT) compressed images. Firstly, by exploiting the edge flow correlations, edge information in the compressed images is extracted and protected, while blocky noise in the smooth background regions is smoothed out by an edge flow-directed filter in the wavelet domain. Then, the curvelet transform coefficients in different subbands are filtered with adaptive thresholds that are obtained according to the edge flow boundary map. The advantage of the new method is that it retains sharp features in images and, compared with other wavelet-based methods, it is capable of achieving higher peak signal-to-noise ratio (PSNR) improvement as well as giving visually very pleasing images.

A new SOLPN (self-organizing learning Petri net)-based rate control algorithm for an MPEG encoder is proposed. The idea is to use SOLPN to realize the RD (rate distortion) model, which is self-organized on line and adaptively updated frame by frame. The method does not require off-line pre-training; hence it is geared toward real-time coding. The comparative results on the examples suggest that our proposed rate control schemes encode video sequences with fewer frame skips, providing good subjective quality and higher PSNR, compared to VM18.

Multi-leaf collimator (MLC) systems are frequently used to deliver photon-based radiation, and allow conformal shaping of treatment beams. Many proton beam centers currently make use of aperture and snout systems, which involve use of a snout to shape and focus the proton beam, a brass aperture to modify field shape, and an acrylic compensator to modulate depth. However, it needs a lot of time and cost of preparing treatment, therefore, we developed the manual MLC for solving this problem. This study was carried out with the intent of designing an MLC system as an alternative to an aperture block system. Radio-activation and dose due to primary proton beam leakage and the presence of secondary neutrons were taken into account during these iterations. Analytical calculations were used to study the effects of leaf material on activation. We have fabricated tray model for adoption with a wobbling snout (30×40 cm2 ) system which used uniform scanning beam. We designed the manual MLC and tray and can reduce the cost and time for treatment. After leakage test of new tray, we upgrade the tray with brass and made the safety tool. First, we have tested the radio-activation with usually brass and new brass for new manual MLC. It shows similar behavior and decay trend. In addition, we have measured the leakage test of a gantry with new tray and MLC tray, while we exposed the high energy with full modulation process on film dosimetry. The radiation leakage is less than 1%. From these results, we have developed the design of the tray and upgrade for safety. Through the radio-activation behavior, we figure out the proton beam leakage level of safety, where there detects the secondary particle, including neutron. After developing new design of the tray, it will be able to reduce the time and cost of proton treatment. Finally, we have applied in clinic test with original brass aperture and manual MLC and calculated the gamma index, 99.74% between them.

The purpose of this study is to perform a dosimetric evaluation of amplitude-based respiratory gating for the delivery of volumetric modulated arc therapy (VMAT). We selected two types of breathing patterns, subjectively among patients with respiratory-gated treatment log files. For patients that showed consistent breathing patterns (CBP) relative to the 4D CT respiration patterns, the variability of the breath-holding position during treatment was observed within the thresholds. However, patients with inconsistent breathing patterns (IBP) show differences relative to those with CBP. The relative isodose distribution was evaluated using an EBT3 film by comparing gated delivery to static delivery, and an absolute dose measurement was performed with a 0.6 cm3 Farmer-type ion chamber. The passing rate percentages under the 3%/3 mm gamma analysis for Patients 1, 2 and 3 were respectively 93.18%, 91.16%, and 95.46% for CBP, and 66.77%, 48.79%, and 40.36% for IBP. Under the more stringent criteria of 2%/2 mm, passing rates for Patients 1, 2 and 3 were respectively 73.05%, 67.14%, and 86.85% for CBP, and 46.53%, 32.73%, and 36.51% for IBP. The ion chamber measurements were within 3.5%, on average, of those calculated by the TPS and within 2.0%, on average, when compared to the static-point dose measurements for all cases of CBP. Inconsistent breathing patterns between 4D CT simulation and treatment may cause considerable dosimetric differences. Therefore, patient training is important to maintain consistent breathing amplitude during CT scan acquisition and treatment delivery.

To achieve more efficient usage of channel bandwidth and provide better protection for the media payload transmitted over lossy packet-switched networks, we introduce a new scheme of generic uneven level protection (ULP) forward error correction. The scheme provides different protection levels for data of different significance within a packet. The ULP scheme is designed to be independent from the nature of the media that it protects, and it is very flexible for any protection configuration the user might need without using any out-of-band signaling. Simulation using a video stream transmitted over a lossy packet-switched network shows that the ULP algorithm achieves significant gain for the quality of the transmission over a wide range of network conditions.

A new optimization method was investigated. This method is distinguished from other existing optimization methods by additional constraints and reduction of unknown variables. It was tested on two ideal cases and the potential of the idea could be verified.

Purpose: As a part of developing treatment planning system, auto‐optimization method was designed to determine photon energy spectrum and the shape of dose profile with various field sizes.Method and Materials: The initial distribution of energy spectrum was designed using approximate formulation. Multi‐spectrum kernels were constructed with the determine photon energy fluence using published mono‐energy kernel, and collapse cone convolution algorithm was implemented to calculate PDDs and dose profiles by considering the effects of beam hardening with depth, kernel tilting, beam softening with off axis distance, off axis ratio, and finite beam source size. Objective function was defined with the sums of differences between measured PDD or dose profiles and calculated PDD or dose profiles. Auto‐optimization method based on steepest decent method was used to minimize objective function by calculating gradient values at each iteration.Results: Determined energy spectrums were not similar to rear photon spectrums, but calculated PDDs showed good agreements with measured data. The dose error beyond build‐up depth was less than 2 % at any depth. Some under‐estimated results (>5%) were showed at the buildup regions ( 30 x30 cm2) because not considering electron contamination. Calculated dose profiles were also well agreed with measured dose profiles (

We, here, present the study on the crystalline behavior of TiO2 in the presence of SiO2 and its optical property at low SiO2 content region from x equals 0 and 0.12 in the (1-x)TiO2-xSiO2 system. From X-ray diffraction, it is observed that just a small addition of SiO2 into TiO2-SiO2 films has made a rutile peak completely vanish. Anatase peaks were decreased in intensity and broadened with the increase in added SiO2 content. Besides, anatase peak was shifted to the large d-spacing and its means that Si ions have incorporated into TiO2. However, the anatase peak shift was saturated above 8 mol%. These facts confirmed that incorporated Si ions inhibited the phase transition between the rutile and the anatase and the crystallization of anatase is also suppressed with SiO2 addition. The anatase band frequency (approximately 140 cm-1) shift to the higher one in Raman spectra and the appearance of the band due to Si-O-Ti vibration in IR spectra indicates clearly that the SiO2 incorporation happens as SiO2 is added in films. The surface topography observed by SEM and AFM shows that the surface becomes smooth and the TiO2 crystallite become smaller with increasing SiO2 content. UV-Visible transmittance spectra showed that all films have good transparency up to about 90% in visible region.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Purpose: We investigated feasibility and advantage of integrating apparent diffusion coefficient (ADC) map for radiation palnning to determine the dose escalation region and evaluated the biolgocial planning reflected on tumormalignancy.Method and Materials: Multimodal image sets of glioma and astrocytoma were acquired with CT, contrast‐enhanced T1, fluid attenuated inversion recovery (FLARE), and diffusion weighted (DW) magnetic resonance (MR)images. ADC map was obtained from DW images and it was converted into the ADC ratio map divided by the average ADC of normal parenchyma in contralateral brain. ADC ratio was used as quantitative criteria representing tumormalignancy and gross tumor volume (GTV) was differentiated by the level of the ADC ratio. GTV of each mulimodal images and stratified regions by ADC ratio were registered on CT using rigid registration. The biological planning using multmodal images was assessed by dose volume histogram and normal tissue complication probability (NTCP). Results: Multimodal images and ADC ratio map were complementary to describe more reliable tumor contour. More progreesed tumor region was distinguished in GTV and location of the most malignant tumor in 3D space was also resolved using the profile of ADC ratio. The advanced radiation treatment planning reflected on biological tumor characteristic was performed using the ADC map and dose escalation was achieved with similar NTCP level of conventional planning. Conclusion: ADC ratio was useful to stratify the tumor in regard to malignancy and it was suggeted a quantitative biological criteria to dermine the dose escalation region for effective treatment results. Biological treatment planning based on the ADC ratio map could support practical adaptive radiation therapy.

Purpose:Intensity modulated radiation therapy has been a very popular and effective treatment technique for the treatment of prostate, head & neck and liver etc. Meanwhile, another innovative treatment technique, intensity modulated arc therapy, was developed to complement some drawbacks of IMRT like long treatment time and low MU efficiency. Since the IMAT completes the treatment just within one or two rotations, it is not easy to get optimized leaf sequences in a deterministic way. In this study, we tried to get optimized IMAT treatment plan by genetic algorithm. Method and Materials: First, the start/end positions of MLC leaves at each rotation angle with 10° interval were selected as optimization variables and encoded into genetic chromosomes. They experience genetic operations such as generation, selection, crossover, mutation and reproduction and the most optimized solution remains in the end of iteration. The constraint of maximum leaf speed was included in these operations. And the fitness of each population was evaluated by DVH volume constraint based objective function. IMAT dose distribution was calculated as a weighted sum of MLC shape at each angle and related Dij matrix similar to IMRTdose calculation. The algorithm was implemented in our treatment planning system and the dose distributions and DVHs of single and double gantry rotation cases were compared. Results: IMAT plan gave comparable results with conventional IMRT even with single gantry rotation and there was not significant improvement in double gantry rotations. Genetic algorithm required about 3,000 generations to reach optimized value due to its stochastic nature. Conclusion: It was possible to optimize IMAT plan with genetic algorithm and the results are optimized MLC leaf sequences readily deliverable in general linear accelerators. It can be an efficient method to solve IMAT optimization problem despite of relative slow convergence.

This paper presents a new error-resilient scheme for the as- yet-defined H.263++ (backward-compatible with both H.263+ and H.263) standard of Question 15/Study Group 16 in International Telecommunication Union (ITU). The key idea is the layered protection of video bitstream in the context of data partitioning scheme, which can be realized by doing adaptive insertion of part of encoded video stream as the redundancy according to channel status and the importance of the syntax. Since the additional data at each layer can help on decoding with increased reliability picture quality can be improved. Also, number of frames decoded is increased with aid of the additional layer.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Sir, Cutis vertices gyrata (CVG) is characterized by thickening of the scalp, which becomes raised to form ridges and furrows resembling the cerebral gyri, which cannot be flattened by traction or pressure. The diagnosis is based on clinical features, and further investigations are needed to demonstrate the precise typical features. We describe how three-dimensional magnetic resonance imaging (3D MRI) can be used to visualize the extent of the lesions in primary non-essential CVG.

Purpose: To evaluate the dosimetric effects of patients setup errors and breathing movement on whole breast irradiation with conventional hard wedge (HW) and field‐in‐field (FIF) techniques. Methods: A total of 10 patients who received whole breast irradiation were chosen for this study. We performed radiation treatment planning for whole breast irradiation with two techniques; conventional hard wedge (HW) and field‐in‐field (FIF). On the subject of each patients, ‐ original plan‐was created using the general clinical planning technique and then we generated ‐ isocenter shift plan‐and ‐ gantry angle shift plan‐to evaluate dose variation according to change of isocenter and gantry angle. In our study, the isocenter was shifted by 0.6 cm for the right‐left, 0.5 cm for superior‐inferior, and 1.4 cm for anterior‐posterior direction refer to Kinoshita et al. study. Assuming that breast shape changes subtly, the gantry angle was shifted from 1° to 5° each tangential fields. To analysis the plan quality this study calculated a dose‐volume histogram (DVH) and the dose indices that are mean dose of CTV, CTV D95, CTV V95, lung V20, heart V40 and PTV dose improvement (PDI) index. Results: When isocenter of lung and heart shifted in the right‐left and superior‐inferior direction, ‐ isocenter shift plan‐showed no significant variation from ‐ original plan‐for most of the indices. However, a significant difference was found in V95 of CTV with isocenter shift in anterior‐posterior direction by assuming the patient shifted in the posterior direction. Shifts in gantry angle slightly affected lung and heart, and smaller changes were seen in PTV. Conclusions: This study evaluated the dosimetric effects of gantry angle and isocenter shift for simulating patients setup errors and breathing motion. The effects of patient and breast changes during treatment could have influence on dose distribution of OARs as well as that of PTV.

Purpose: To determine the required radiation dose and to compensate the dose distribution during the fractionated adaptive radiation therapy, correlation of dose and individual bioluminescence responses of 4T1 breast cancers cells was evaluated using the in‐vivo bioluminescence tomography (BLT) images. Methods: After a dose of 20 Gy in a single fraction was delivered by 200‐kV X‐ray beams to six female BALB/c mice, radiation responses of the cancer cells were monitored with BLT images in every 2–3 days. The dose distributions on mice were predicted in Monte Carlo simulation using EGSnrc codes (BEAMNRC and DOSXYZNRC). As the bioluminescence distributions were deformed onto the dose maps by applying the vector fields acquired in contour‐based rigid and deformable registration, mathematical correlation of dose and bioluminescence was analyzed. The spatial and quantitative bioluminescence variations were also mapped on the computed tomography images to track the proliferation and metastasis characteristics particularly in tumor marginal progression. Results: Radiation treatment showed the negative correlation between radiation dose and bioluminescence intensity with covariance of up to ‐ 0.4. By comparing and categorizing the bioluminescence responses depending on doses in treated and untreated mice group, amount of delivered dose and the field size could be adjusted for more effective control of cancer cells. Spatial tracking of the bioluminescence variations on anatomical coordinates provided useful tool to differentiate the infiltrative cancer cells. Conclusion: Quantitative BLT images were a useful tool to evaluate dose‐related molecular bioluminescence responses of cancer cells of radiation treatment. Required effective doses would be adaptively delivered based on the BLT images according to the radiation treatment scheme and characteristics of the cancer cells. This research was supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST). (Grant No.2009‐00420)

Purpose: Metal artifacts generated by dental implants cause dose discrepancy in intensity‐modulated radiation therapy (IMRT) of head‐and‐neck cancer cases due to the inaccurate predicted doses. To determine the effective metal artifact reduction (MAR) method presenting minimum dose errors with delivered dose, dosimetric impact of different MAR methods were evaluated in radiation treatment plans. Methods: MAR was implemented using Euler elastic and curvature based sinogram inpainting (EECSI) algorithm, volume clustering with Hounsfield unit (HU) overriding (VCU), and multimodal image‐based correction (MIC). When delivered doses were calculated on the corrected computed tomography (CT) images by employing the same plan parameters in the reference IMRT plan (Planref), dose errors were analyzed with dose‐volume histograms (DVHs), monitor unit, and dose conformity of target volumes. Dosimetric impacts were also estimated using the biophysical evaluation parameters in three oropharyngeal patients. Results: Optimized fluence in the Planref resulted in overdose up to 5% in the salivary glands and spinal cords on the corrected CT images, while the overdose in target volumes increased tumor control probability of 3–7%. Target doses in peripheral regions affected by the surrounded dark pixels were deformed and decreased conformity. The DVHs of organs at risk (OAR) and target volumes also showed the 5–8% volume gap in the prescription dose range. As the efficient MAR is employed into the head‐and‐neck IMRT plans, more accurate predicted doses of primary structures would be achieved, even if the dose differences of each MAR method are small less than 2–3%. Conclusion: EEECSI and VCU were useful methods to reduce the metal artifacts and to predict more accurate delivered doses. Since dental artifacts cause dose variation in peripheral region of target volumes and OAR, dose calculation on corrected CT images using efficient MAR techniques and dose verification would be encouraged in head‐and‐neck IMRT plans.

Purpose: Impacts of sensitometric curve depending on scanning parameters and post‐operative processes to correct active layer and background effects on radiochromic film dosimetry were investigated to determine the key factors for more accurate dose verification. Method and Materials: Dose discrepancies were evaluated in the 60°‐enhanced dynamic wedged field and intensity‐modulated beams using the GafChromic EBT2 films and the software developed in‐house. Dosimetric effects were analyzed as the following conditions were applied: adjustment of the scanning contrast and brightness, background corrections in relative and absolute mode using non‐irradiated or irradiated film corresponding delivered dose levels, and active layer correction to lessen the thickness difference of the response material. Maximum dose and pass ratio applied the gamma criteria (distance‐to‐agreement of 3 mm and dose difference of 3%) were compared with planning system results in the wedged and the modulated field, respectively. Results: Absolute dose discrepancies of 3–6 %, pass ratio difference of 1–9% were generated by the effect of the applied sensitometric curve. Dose discrepancies were lower than 1% according to the correction methods of background or active layer correction. Slope variations of sensitometric curves led to different dose differences at each dose range. Thus under the same scanning conditions, lower pass ratio was represented in modulated beams, although the discrepancy at the point of maximum dose was decreased in wedged field. When the exposed film was used for background correction, dose differences in the portion of irradiated field were reduced, but the pass ratio was not improved because of the non‐uniform film response according to the dose levels. Conclusion: Determination of the sensitometric curve influenced by the scanning parameters was the primary factor to the dose differences. Under the selection of the sensitometric curve and post‐operative correction methods, dose discrepancy can be minimized for required radiochromic film dosimetry.

Purpose: As a part of patient specific QA for IMRT plans, customized program was developed to evaluate accurate dose distribution of IMRT plans using 120 Leaf dMLC. It is designed to make 2D dose map, where mid‐leaf, inter‐leaf, rounded leaf end transmission dose, tongue and groove (T&G) effects, scattered dose from dMLC as well as primary beam dose were calculated with high resolution (1 mm). Method and Materials: Mid‐leaf, interleaf transmission dose, scattered dose from dMLC were measured by films with various collimatorfield sizes at 6 MV X‐ray on Varian 21Ex. The transmission dose from T&G was calculated using superposition of single slit‐beam kernel extracted from measured open beam profile. The transmission dose from rounded leaf end was calculated along the distance from leaf end. By analyzingMLCsequence file of IMRT plans and measured dosimetric data of dMLC, intensity matrix per segmented MU was produced. 2D kernel profile produced by 1×1 mm2 pencil beam was derived from measured 10×10 cm2 profile by iterative method using line search optimization algorithm. Then primary dose map was reconstructed using superposition‐convolution method with intensity matrix and kernel profile. Extra dose from dMLC per segmented MU was also added to the primary dose map. Results: Reconstructed 2D dose map could explain contributions of primary beam dose, and extra doses resulted from the movement of leaves. The transmission dose from rounded leaf end was increased up to 10% to the total dose when leaves had little motion. Mid‐leaf or interleaf transmission dose also could contribute average 10% to the total dose. Conclusion: Our program can explain unwanted dose distribution due to the movement of dMLC. And it could be expected to be an alternative method instead of film dosimetry, or can be used to complement the drawback of 2D‐array detector with poor resolution.

Purpose: We evaluated the dosimetric accuracy of dose calculation with a convolution/superposition (C/S) and a pencil‐beam algorithm with the use of the multiple inhomogeneous head and neck phantom for intensity modulated radiation therapy(IMRT)treatment plan. Method and Materials: The inhomogeneous head and neck phantom for IMRTquality assurance (QA) was housed in a custom‐designed package for efficient evaluation of the measured doses using the different materials and various detectors. Comparisons of measured and deconvolved beam profile obtained from a Gaussian fitting approaches were performed using the real penumbra width to remove ionization chamber size effect. The relative dosimetry obtained with the single‐beam dose calculation algorithm was also compared to the MapCheck measurements for a head and neck IMRTtreatment plans. The accuracy of IMRTdose calculations with the C/S and pencil‐beam algorithms were also investigated with respect to measurements used in head and neck phantom in the presence of inhomogeneities. Results: The deconvolved penumbra was 2.2 mm and calculated value was 2.6 mm with pencil‐beam algorithm. The differences between calculated dose and measured dose with the MapCheck were less than 4.0% for the horizontal profile of IMRT head and neck treatment plan. The differences for the C/S and pencil‐beam dose calculation algorithms were within 5.0% in average target doses.Ionization chamber experiments showed approximately 2.5% better agreement than the glass rod detector. Conclusion: Our results show that accurate measurements of the penumbral region with consideration of inhomogeneities improve the accuracy of the dose calculation algorithms predicted by the treatment planning system. Therefore, it is important to choose an appropriate detector

During operations, neurosurgeons usually perform multiple temporary occlusions of parental artery, possibly resulting in the neuronal damage. It is generally thought that neuronal damage by cerebral ischemia is associated with extracellular concentrations of the excitatory amino acids. In this study, we measured the dynamics of extracellular glutamate release in 11 vessel occlusion (VO) model to compare between single occlusion and repeated transient occlusions within short interval. Changes in cerebral blood flow were monitored by laser-Doppler flowmetry simultaneously with cortical glutamate level measured by amperometric biosensor. From real time monitoring of glutamate release in 11 VO model, the change of extracellular glutamate level in repeated transient occlusion group was smaller than that of single occlusion group, and the onset time of glutamate release in the second ischemic episode of repeated occlusion group was delayed compared to the first ischemic episode which was similar to that of single 10 min ischemic episode. These results suggested that repeated transient occlusion induces less glutamate release from neuronal cell than single occlusion, and the delayed onset time of glutamate release is attributed to endogeneous protective mechanism of ischemic tolerance.