Detection of tissue pH with quantitative chemical exchange saturation transfer magnetic resonance imaging.

Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) has emerged as a novel means for sensitive detection of dilute labile protons and chemical exchange rates. By sensitizing to pH-dependent chemical exchange, CEST MRI has shown promising results in monitoring tissue statuses such as pH changes in disorders like acute stroke, tumor, and acute kidney injury. This article briefly reviews the basic principles for CEST imaging and quantitative measures, from the simplistic asymmetry analysis to multipool Lorentzian decoupling and quasi-steady-state reconstruction. In particular, the advantages and limitations of commonly used quantitative approaches for CEST applications are discussed.

Causes of anxiety among teachers giving face-to-face lessons after the reopening of schools during the COVID-19 pandemic: a cross-sectional study.

BACKGROUND: Coronavirus infections are spreading rapidly worldwide, and primary and middle schools are closed in many countries. After the state of emergency was lifted in Japan, schools have reopened, and teachers are conducting face-to-face classes while maintaining safety precautions. This study aimed to assess the factors contributing to infection-related anxiety and educational anxiety among teachers conducting face-to-face classes during the COVID-19 pandemic after schools reopened. METHODS: This questionnaire-based cross-sectional study was conducted with 263 primary and middle school teachers in the Shinagawa area of Tokyo (October 10-30, 2020). The questionnaire assessed the type of school (primary or middle school), sex, age, and factors contributing to infection-related anxiety and educational anxiety that arose from the pandemic. The levels of anxiety and the factors contributing to anxiety were assessed using a 5-point Likert scale ranging from 1 (not at all) to 5 (very anxious). RESULTS: In an analysis of the data of 237 participants excluding the missing data, many teachers reported feeling infection- and education-related anxiety. A majority of the participants were women (n = 152, 64.1%), and the mean age of the participants was 39.8 ± 11.3 years. A stepwise multiple regression analysis identified six factors for infection-related anxiety as significant (R2 = 0.61, p < 0.001). Among these variables, the largest partial regression coefficient value was reported for the following reason: "I feel anxious because we cannot ensure the safety of teachers themselves or of their families" (ß = 0.37, p < 0.001). For educational anxiety, four of six reasons were identified as significant (R2 = 0.64, p < 0.001). Among these, "anxiety about the students' home situations" (ß = 0.41, p < 0.001) and "delay in education (students' side)" (ß = 0.27, p < 0.001) had stronger associations with anxiety compared to the others. CONCLUSION: In-person education during the COVID-19 pandemic has caused teachers to experience anxiety. This report provides useful information by highlighting the reasons for infection-related anxiety and educational anxiety that teachers experience in face-to-face classes during a pandemic. Even if the coverage of a COVID-19 vaccine becomes widespread worldwide, we will still be combating COVID-19 infections for at least a few years. Given concerns regarding such infections, to ensure students' right to education, it is essential to understand why teachers feel anxious and to determine appropriate measures to decrease such anxiety.

Continuous Glibenclamide Prevents Hemorrhagic Transformation in a Rodent Model of Severe Ischemia-Reperfusion.

BACKGROUND: Endovascular thrombectomy (EVT) is highly effective but may also lead to hemorrhagic transformation (HT) and edema, which may be more pronounced in severe ischemia. We sought to determine whether glibenclamide can attenuate HT and edema in a severe ischemia-reperfusion model that reflects EVT. METHODS: Using a transient middle cerebral artery occlusion (tMCAo) rodent model of stroke, we studied two rat cohorts, one without rt-PA and a second cohort treated with rt-PA. Glibenclamide or vehicle control was administered as an intravenous bolus at reperfusion, followed by continuous subcutaneous administration with an osmotic pump. RESULTS: Compared to vehicle control, glibenclamide improved neurological outcome (median 7, interquartile range [IQR 6-8] vs. control median 6 [IQR 0-6], p = 0.025), reduced stroke volume (323 ± 42 vs. 484 ± 60 mm3, p < 0.01), swelling volume (10 ± 4 vs. 28 ± 7%, p < 0.01) and water content (84 ± 1 vs. 85 ± 1%, p < 0.05). Glibenclamide administration also reduced HT based on ECASS criteria, densitometry (0.94 ± 0.1 vs. 1.15 ± 0.2, p < 0.01), and quantitative hemoglobin concentration (2.7 ± 1.5 vs. 6.2 ± 4.6 uL, p = 0.011). In the second cohort with rt-PA coadministration, concordant effects on HT were observed with glibenclamide. CONCLUSIONS: Taken together, these studies demonstrated that glibenclamide reduced the amount of edema and HT after severe ischemia. This study suggests that co-administration of glibenclamide may be worth further study in severe stroke patients treated with EVT with or without IV rt-PA.

Mapping tissue pH in an experimental model of acute stroke - Determination of graded regional tissue pH changes with non-invasive quantitative amide proton transfer MRI.

pH-weighted amide proton transfer (APT) MRI is sensitive to tissue pH change during acute ischemia, complementing conventional perfusion and diffusion stroke imaging. However, the currently used pH-weighted magnetization transfer (MT) ratio asymmetry (MTRasym) analysis is of limited pH specificity. To overcome this, MT and relaxation normalized APT (MRAPT) analysis has been developed that to homogenize the background signal, thus providing highly pH conspicuous measurement. Our study aimed to calibrate MRAPT MRI toward absolute tissue pH mapping and determine regional pH changes during acute stroke. Using middle cerebral artery occlusion (MCAO) rats, we performed lactate MR spectroscopy and multi-parametric MRI. MRAPT MRI was calibrated against a region of interest (ROI)-based pH spectroscopy measurement (R2 = 0.70, P < 0.001), showing noticeably higher correlation coefficient than the simplistic MTRasym index. Capitalizing on this, we mapped brain tissue pH and semi-automatically segmented pH lesion, in addition to routine perfusion and diffusion lesions. Tissue pH from regions of the contralateral normal, perfusion/diffusion lesion mismatch and diffusion lesion was found to be 7.03 ±â€¯0.04, 6.84 ±â€¯0.10, 6.52 ±â€¯0.19, respectively. Most importantly, we delineated the heterogeneous perfusion/diffusion lesion mismatch into perfusion/pH and pH/diffusion lesion mismatches, with their pH being 7.01 ±â€¯0.04 and 6.71 ±â€¯0.12, respectively (P < 0.05). To summarize, our study calibrated pH-sensitive MRAPT MRI toward absolute tissue pH mapping, semi-automatically segmented and determined graded tissue pH changes in ischemic tissue and demonstrated its feasibility for refined demarcation of heterogeneous metabolic disruption following acute stroke.

A generalized ratiometric chemical exchange saturation transfer (CEST) MRI approach for mapping renal pH using iopamidol.

PURPOSE: To extend the pH detection range of iopamidol-based ratiometric chemical exchange saturation transfer (CEST) MRI at sub-high magnetic field and establish quantitative renal pH MRI. METHODS: Chemical exchange saturation transfer imaging was performed on iopamidol phantoms with pH of 5.5 to 8.0 and in vivo on rat kidneys (n = 5) during iopamidol administration at a 4.7 T. Iopamidol CEST effects were described using a multipool Lorentzian model. A generalized ratiometric analysis was conducted by ratioing resolved iopamidol CEST effects at 4.3 and 5.5 ppm obtained under 1.0 and 2.0 µT, respectively. The pH detection range was established for both the standard ratiometric analysis and the proposed resolved approach. Renal pH was mapped in vivo with regional pH assessed by one-way analysis of variance. RESULTS: Good-fitting performance was observed in multipool Lorentzian resolving of CEST effects (R2 s > 0.99). The proposed approach extends the in vitro pH detection range to 5.5 to 7.5 at 4.7 T. In vivo renal pH was measured to be 7.0 ± 0.1, 6.8 ± 0.1, and 6.5 ± 0.2 for cortex, medulla and calyx, respectively (P < 0.05). CONCLUSIONS: The proposed ratiometric approach extended the iopamidol pH detection range, enabling the renal pH mapping in vivo, which is promising for pH imaging studies at sub-high or low fields with potential clinical applicability. Magn Reson Med 79:1553-1558, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

pH-sensitive MRI demarcates graded tissue acidification during acute stroke - pH specificity enhancement with magnetization transfer and relaxation-normalized amide proton transfer (APT) MRI.

pH-sensitive amide proton transfer (APT) MRI provides a surrogate metabolic biomarker that complements the widely-used perfusion and diffusion imaging. However, the endogenous APT MRI is often calculated using the asymmetry analysis (MTRasym), which is susceptible to an inhomogeneous shift due to concomitant semisolid magnetization transfer (MT) and nuclear overhauser (NOE) effects. Although the intact brain tissue has little pH variation, white and gray matter appears distinct in the MTRasym image. Herein we showed that the heterogeneous MTRasym shift not related to pH highly correlates with MT ratio (MTR) and longitudinal relaxation rate (R1w), which can be reasonably corrected using the multiple regression analysis. Because there are relatively small MT and R1w changes during acute stroke, we postulate that magnetization transfer and relaxation-normalized APT (MRAPT) analysis increases MRI specificity to acidosis over the routine MTRasym image, hence facilitates ischemic lesion segmentation. We found significant differences in perfusion, pH and diffusion lesion volumes (P<0.001, ANOVA). Furthermore, MRAPT MRI depicted graded ischemic acidosis, with the most severe acidosis in the diffusion lesion (-1.05±0.29%/s), moderate acidification within the pH/diffusion mismatch (i.e., metabolic penumbra, -0.67±0.27%/s) and little pH change in the perfusion/pH mismatch (i.e., benign oligemia, -0.04±0.14%/s), providing refined stratification of ischemic tissue injury.

Tissue Characterization with Quantitative High-Resolution Magic Angle Spinning Chemical Exchange Saturation Transfer Z-Spectroscopy.

Chemical exchange saturation transfer (CEST) provides sensitive magnetic resonance (MR) contrast for probing dilute compounds via exchangeable protons, serving as an emerging molecular imaging methodology. CEST Z-spectrum is often acquired by sweeping radiofrequency saturation around bulk water resonance, offset by offset, to detect CEST effects at characteristic chemical shift offsets, which requires prolonged acquisition time. Herein, combining high-resolution magic angle spinning (HRMAS) with concurrent application of gradient and rf saturation to achieve fast Z-spectral acquisition, we demonstrated the feasibility of fast quantitative HRMAS CEST Z-spectroscopy. The concept was validated with phantoms, which showed excellent agreement with results obtained from conventional HRMAS MR spectroscopy (MRS). We further utilized the HRMAS Z-spectroscopy for fast ex vivo quantification of ischemic injury with rodent brain tissues after ischemic stroke. This method allows rapid and quantitative CEST characterization of biological tissues and shows potential for a host of biomedical applications.

Comparison of image sensitivity between conventional tensor-based and fast diffusion kurtosis imaging protocols in a rodent model of acute ischemic stroke.

Diffusion kurtosis imaging (DKI) can offer a useful complementary tool to routine diffusion MRI for improved stratification of heterogeneous tissue damage in acute ischemic stroke. However, its relatively long imaging time has hampered its clinical application in the emergency setting. A recently proposed fast DKI approach substantially shortens the imaging time, which may help to overcome the scan time limitation. However, to date, the sensitivity of the fast DKI protocol for the imaging of acute stroke has not been fully described. In this study, we performed routine and fast DKI scans in a rodent model of acute stroke, and compared the sensitivity of diffusivity and kurtosis indices (i.e. axial, radial and mean) in depicting acute ischemic lesions. In addition, we analyzed the contrast-to-noise ratio (CNR) between the ipsilateral ischemic and contralateral normal regions using both conventional and fast DKI methods. We found that the mean kurtosis shows a relative change of 47.1 ± 7.3% between the ischemic and contralateral normal regions, being the most sensitive parameter in revealing acute ischemic injury. The two DKI methods yielded highly correlated diffusivity and kurtosis measures and lesion volumes (R(2) ⩾ 0.90, p < 0.01). Importantly, the fast DKI method exhibited significantly higher CNR of mean kurtosis (1.6 ± 0.2) compared with the routine tensor protocol (1.3 ± 0.2, p < 0.05), with its CNR per unit time (CNR efficiency) approximately doubled when the scan time was taken into account. In conclusion, the fast DKI method provides excellent sensitivity and efficiency to image acute ischemic tissue damage, which is essential for image-guided and individualized stroke treatment.

Fast diffusion kurtosis imaging (DKI) with Inherent COrrelation-based Normalization (ICON) enhances automatic segmentation of heterogeneous diffusion MRI lesion in acute stroke.

Diffusion kurtosis imaging (DKI) has been shown to augment diffusion-weighted imaging (DWI) for the definition of irreversible ischemic injury. However, the complexity of cerebral structure/composition makes the kurtosis map heterogeneous, limiting the specificity of kurtosis hyperintensity to acute ischemia. We propose an Inherent COrrelation-based Normalization (ICON) analysis to suppress the intrinsic kurtosis heterogeneity for improved characterization of heterogeneous ischemic tissue injury. Fast DKI and relaxation measurements were performed on normal (n = 10) and stroke rats following middle cerebral artery occlusion (MCAO) (n = 20). We evaluated the correlations between mean kurtosis (MK), mean diffusivity (MD) and fractional anisotropy (FA) derived from the fast DKI sequence and relaxation rates R1 and R2 , and found a highly significant correlation between MK and R1 (p < 0.001). We showed that ICON analysis suppressed the intrinsic kurtosis heterogeneity in normal cerebral tissue, enabling automated tissue segmentation in an animal stroke model. We found significantly different kurtosis and diffusivity lesion volumes: 147 ± 59 and 180 ± 66 mm3 , respectively (p = 0.003, paired t-test). The ratio of kurtosis to diffusivity lesion volume was 84% ± 19% (p < 0.001, one-sample t-test). We found that relaxation-normalized MK (RNMK), but not MD, values were significantly different between kurtosis and diffusivity lesions (p < 0.001, analysis of variance). Our study showed that fast DKI with ICON analysis provides a promising means of demarcation of heterogeneous DWI stroke lesions.

Monitoring of filter patency during carotid artery stenting using near-infrared spectroscopy with high time-resolution.

We aimed to evaluate the usefulness of a newly developed, near-infrared spectroscopy (NIRS) device for monitoring hemodynamic changes during carotid artery stenting (CAS), as a means to detect filter obstruction due to distal embolism. We evaluated 16 patients with internal carotid artery (ICA) stenosis during the CAS procedure, using a NIRS system that can monitor not only changes in oxygenation of hemoglobin (Hb), but also the fluctuation of oxyhemoglobin (oxy-Hb) synchronized with heartbeat. The NIRS system detected a marked decrease of oxy-Hb and an increase of deoxyhemoglobin (deoxy-Hb) during ICA occlusion in patients without anterior cross circulation (ACC). Patients with ACC showed much smaller changes. The analysis of oxy-Hb fluctuation made it possible to detect occurrence of no-flow in the absence of Hb concentration changes. The amplitude of oxy-Hb fluctuation in the no/slow-flow group was significantly smaller than that in the normal-flow group. Our results indicate that the present high time-resolution NIRS device, which can measure oxy-Hb fluctuation, is superior to conventional NIRS for detecting filter obstruction.

Investigation of the possibility of using an augmented reality-based endotracheal aspiration simulation tool for nursing education.

AIM: We developed an augmented reality technology-based endotracheal aspiration simulation tool (the AR tool) consisting of three modes: a mode for nursing students to learn endotracheal aspiration by themselves (learning mode); a mode for repeated practice (practice mode); and a mode for confirmation testing (test mode). This study aimed to compare the learning outcomes of the AR tool with traditional training mannequins and identify potential uses and improvements of the AR tool. METHODS: We invited students, and faculty members from the three universities who agreed to cooperate in conducting this study. Fifty-four students and nine faculty members agreed to participate in this study. The students were divided into two groups. One group was to study with the AR tool and the other group was to study with the traditional half-body training mannequin for suction. The students in both groups were asked to demonstrate endotracheal aspiration on another full-body type training mannequin which could be used as a patient with a tracheostomy (Skill test). Group interviews with faculty members focused on the topic of the AR tool's potential use in nursing education and improvement needed. RESULTS: There was little significant difference in the skill test results of endotracheal aspiration of students in both groups. The students and faculty members both expressed an interest in the AR tool. They said it was suitable for self-study of endotracheal aspiration. CONCLUSIONS: This AR tool is an effective teaching tool for learning the sequence of endotracheal suctioning, although there are some areas that need improvement.

Monitoring of hemodynamic change in patients with carotid artery stenosis during the tilt test using wearable near-infrared spectroscopy.

Transient ischemic attack (TIA) is a major complication in patients with carotid artery stenosis. Patients with severe stenosis sometimes complain of orthostatic dizziness, such as syncope. The purpose of this study was to examine the usefulness of near-infrared spectroscopy (NIRS) for evaluating cerebral circulation in patients with carotid artery stenosis during head-up tilt test (HUTT). Fourteen patients with carotid artery stenosis and nine normal control subjects participated. In addition to blood pressure monitoring, hemoglobin (Hb) values (oxy-Hb, deoxy-Hb, and total Hb) were recorded by a wearable NIRS instrument with a high time resolution during HUTT. Oxy-Hb, which decreased initially when the test table was elevated, subsequently increased in normal volunteers and patients with carotid artery stenosis and did not differ significantly between the two groups. However, the oxy-Hb reduction in the carotid artery stenosis group (-0.02 ± 0.03 a.u.) at 30 s after elevation of the table was significantly larger than in the normal group (0.02 ± 0.02 a.u., P < 0.01). Our results indicate that oxy-Hb reduction in patients with carotid artery stenosis may be related to orthostatic dizziness. We concluded that NIRS monitoring is useful for evaluating cerebral autoregulation in patients with severe carotid artery stenosis.

Anatomical variation of superior petrosal vein and its management during surgery for cerebellopontine angle meningiomas.

No systematic study is yet available that focuses on the surgical anatomy of the superior petrosal vein and its significance during surgery for cerebellopontine angle meningiomas. The aim of the present study was to examine the variation of the superior petrosal vein via the retrosigmoid suboccipital approach in relation to the tumor attachment of cerebellopontine angle meningiomas as well as postoperative complications related to venous occlusion. Forty-three patients with cerebellopontine angle meningiomas were analyzed retrospectively. Based on the operative findings, the tumors were classified into four subtypes: the petroclival type, tentorial type, anterior petrous type, and posterior petrous type. According to a previous anatomical report, the superior petrosal veins were divided into three groups: Type I which emptied into the superior petrosal sinus above and lateral to the internal acoustic meatus, Type II which emptied between the lateral limit of the trigeminal nerve at Meckel's cave and the medial limit of the facial nerve at the internal acoustic meatus, and Type III which emptied into the superior petrosal sinus above and medial to Meckel's cave. In both the petroclival and anterior petrous types, the most common vein was Type III which is the ideal vein for a retrosigmoid approach. In contrast, the Type II vein which is at high risk of being sacrificed during a suprameatal approach procedure was most frequent in posterior petrous type, in which the superior petrosal vein was not largely an obstacle. Intraoperative sacrificing of veins was associated with a significantly higher rate of venous-related phenomena, while venous complications occurred even in cases where the superior petrosal vein was absent or compressed by the tumor. The variation in the superior petrosal vein appeared to differ among the tumor attachment subtypes, which could permit a satisfactory surgical exposure without dividing the superior petrosal vein. In cases where the superior petrosal vein was previously occluded, other bridging veins could correspond with implications for the crucial venous drainage system, and should thus be identified and protected whenever possible.

Glibenclamide reduces secondary brain injury in a SAH rat model by reducing brain swelling and modulating inflammatory response.

BACKGROUND: Early brain injury (EBI) after subarachnoid hemorrhage (SAH) is a new therapeutic target. Sulfonylurea receptor 1 (SUR1) is expressed in nerve cells, glial cells, and vascular endothelial cells in EBI. SUR1 promotes intracellular inflow of Na and Ca ions, resulting in cell swelling and depolarization, and finally cell death. Glibenclamide reduced cerebral edema and mortality in a basic study of cerebral ischemia. However, the effects of glibenclamide on EBI have not been fully elucidated. This study examined the inhibitory effect of glibenclamide on EBI. METHODS: Rats were divided into the sham group, SAH-control group, and SAH-glibenclamide group. The water content of the brain was measured using the dry-wet method. In addition, the brain was divided into the cortex, putamen, and hippocampus, and expression of inflammatory cytokines was evaluated by the polymerase chain reaction method. In addition, microglia in the brain were evaluated immunohistologically. RESULTS: Water content of the brain was significantly decreased in the SAH-glibenclamide group compared to the SAH-control group. Interleukin-1beta (IL-1ß), tumor necrosis factor alpha (TNFα), and nuclear factor-kappa B significantly increased in the cerebral cortex after SAH. IL-1ß and TNFα in the cortex were significantly decreased in the SAH-glibenclamide group compared to the SAH-control group. Immunohistochemical staining confirmed that SAH causes extensive microglial activation in the brain, which was suppressed by glibenclamide. CONCLUSIONS: The present study showed that glibenclamide suppressed cerebral edema and activation of microglia and hypersecretion of inflammatory cytokines. Glibenclamide is a potential therapeutic method which may significantly improve the functional prognosis.

Phospholipase Cdelta3 regulates RhoA/Rho kinase signaling and neurite outgrowth.

Phospholipase Cδ3 (PLCδ3) is a key enzyme regulating phosphoinositide metabolism; however, its physiological function remains unknown. Because PLCδ3 is highly enriched in the cerebellum and cerebral cortex, we examined the role of PLCδ3 in neuronal migration and outgrowth. PLCδ3 knockdown (KD) inhibits neurite formation of cerebellar granule cells, and application of PLCδ3KD using in utero electroporation in the developing brain results in the retardation of the radial migration of neurons in the cerebral cortex. In addition, PLCδ3KD inhibits axon and dendrite outgrowth in primary cortical neurons. PLCδ3KD also suppresses neurite formation of Neuro2a neuroblastoma cells induced by serum withdrawal or treatment with retinoic acid. This inhibition is released by the reintroduction of wild-type PLCδ3. Interestingly, the H393A mutant lacking phosphatidylinositol 4,5-bisphosphate hydrolyzing activity generates supernumerary protrusions, and a constitutively active mutant promotes extensive neurite outgrowth, indicating that PLC activity is important for normal neurite outgrowth. The introduction of dominant negative RhoA (RhoA-DN) or treatment with Y-27632, a Rho kinase-specific inhibitor, rescues the neurite extension in PLCδ3KD Neuro2a cells. Similar effects were also detected in primary cortical neurons. Furthermore, the RhoA expression level was significantly decreased by serum withdrawal or retinoic acid in control cells, although this decrease was not observed in PLCδ3KD cells. We also found that exogenous expression of PLCδ3 down-regulated RhoA protein, and constitutively active PLCδ3 promotes the RhoA down-regulation more significantly than PLCδ3 upon differentiation. These results indicate that PLCδ3 negatively regulates RhoA expression, inhibits RhoA/Rho kinase signaling, and thereby promotes neurite extension.

[A case of late recurrence of urothelial carcinoma in an ileal conduit after radical cystectomy and ileal conduit diversion for bladder cancer].

Recurrence of urothelial cancer in an ileal conduit after radical cystectomy is rare. A 79-year-old man suffered bladder cancer (UC cTisN0M0 G2＞3) and underwent total cystectomy with ileal conduit. He had recurrence of the right renal pelvis carcinoma 6 years after the total cystectomy, and was treated by right radical nephroureterectomy (pT3 G2＝3). The patient had another episode of recurrence in the ileal conduit 13 years after the initial operation. The entire ileal conduit (UC, G3, ew (-)) was resected and left cutaneous ureterostomy was performed. This case suggests that long-term follow-up is necessary after radical cystectomy and ileal conduit for urinary diversion.

High-dose-infliximab-associated Cerebral Venous Sinus Thrombosis: A Case Report and Review of the Literature.

A 28-year-old woman experienced severe headache and right homonymous hemianopia after receiving high-dose infliximab for Crohn's disease. Computed tomography showed hemorrhagic infarction in the left temporal and parietal lobes. An angiogram revealed left transverse to sigmoid sinus occlusion and a stagnated Labbe vein. The patient was treated surgically and achieved a good outcome. Inflammatory bowel diseases are known to accompany venous and arterial thrombosis in 1-2% of cases. Recently, infliximab has been suggested to increase this possibility. A case of Crohn's disease presenting with cerebral sinus thrombosis in the remission period during long-term/high-dose use of infliximab is presented. In addition, infliximab-associated thrombosis cases were reviewed.

Effect of transient forebrain ischemia on flavoprotein autofluorescence and the somatosensory evoked potential in the rat.

In order to evaluate the effect of cerebral ischemia on the flavoprotein fluorescence (FPF), we compared the changes in the FPF and somatosensory evoked potential (SEP) during transient cerebral ischemia in the rat. We measured the FPF and SEP simultaneously via a cranial window made over the right sensorimotor cortex during the left median nerve stimulation in F344 rats. We compared change in FPF and SEP during cerebral ischemia for 60 min. The rCBF were rapidly recovered after reperfusion. However, the recovery rates of the FPF were significantly faster than those of the SEP after reperfusion. These findings indicate that activity-dependent changes of the FPF do not necessarily correlate with the electrical activity after transient cerebral ischemia.

Comparison of somatosensory evoked potentials and cerebral blood oxygenation changes in the sensorimotor cortex during activation in the rat.

The relationship between changes in cerebral blood oxygenation and neuronal activity remains to be fully established. We compared somatosensory evoked potentials (SEP) and evoked cerebral blood oxygenation (CBO) changes in the sensorimotor cortex of the rat. In rats anesthetized with urethane and alpha-chloralose, we measured SEP and CBO using visible light spectroscopy (VLS) during neuronal activity. Increase of stimulus frequency caused a decrease of SEP amplitude, but an increase in concentration changes of deoxy-Hb and oxygen saturation. The difference in frequency responses between SEP and CBO might be caused by activation of inhibitory neurons, which could suppress excitatory neurons at high stimulus frequencies; activation of inhibitory neurons could reduce SEP amplitude, and increase oxygen saturation due to an increase of evoked cerebral blood flow.

Bedside assessment of cerebral vasospasms after subarachnoid hemorrhage by near infrared time-resolved spectroscopy.

We examined the usefulness of near infrared time-resolved spectroscopy (TRS) for detection of vasospasm in subarachnoid hemorrhage (SAH). We investigated seven aneurysmal SAH patients with poor clinical conditions (WFNS grade V) who underwent endovascular coil embolization. Employing TRS, we measured the oxygen saturation (SO(2)) and baseline hemoglobin concentrations in the cortices. Measurements of TRS and transcranial Doppler sonography (TCD) were performed repeatedly for 14 days after SAH. In four of the seven patients, the SO(2) and hemoglobin concentrations measured in the brain tissue of the middle cerebral artery territory remained stable after SAH. However, in three patients, TRS revealed abrupt decreases in SO(2) and total hemoglobin between 5 and 9 days after SAH. Cerebral angiography performed on the same day revealed severe vasospasms in these patients. Although TCD detected the vasospasm in two of three cases, it failed to do so in one case. TRS could detect vasospasms after SAH by evaluating the cortical blood oxygenation.