Association between preoperative cortical magnetic susceptibility and postoperative changes in the cerebral blood flow on cognitive improvement following carotid endarterectomy.

INTRODUCTION: While patients who experience improved cognition following carotid endarterectomy (CEA) typically demonstrate restored brain perfusion after the procedure, it is worth noting that less than 50% of patients in whom postoperative cerebral blood flow (CBF) restoration is achieved actually show improved cognition after postoperatively. This suggests that factors beyond the mere restoration of CBF may play a role in postoperative cognitive improvement. Increased iron deposition in the cerebral cortex may cause neural damage, and quantitative susceptibility mapping (QSM) obtained using magnetic resonance imaging (MRI) quantifies magnetic susceptibility in the cerebral cortex, allowing for the assessment of iron deposition in vivo. The purpose of the present study was to determine whether preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA. METHODS: Brain MRI with a three-dimensional gradient echo sequence was preoperatively performed in 53 patients undergoing CEA for ipsilateral internal carotid artery stenosis (≥70%), and QSM with brain surface correction and vein removal was obtained. Cortical magnetic susceptibility was measured in the cerebral hemisphere ipsilateral to surgery on QSM. Preoperatively and at two months after the surgery, brain perfusion single-photon emission computed tomography (SPECT) and neuropsychological assessments were conducted. Using these collected data, we evaluated alterations in CBF within the affected hemisphere and assessed cognitive improvements following the operation. RESULTS: A logistic regression analysis showed that a postoperative greater increase in CBF (95% confidence interval [CI], 1.06-1.90; p = 0.0186) and preoperative lower cortical magnetic susceptibility (95% CI, 0.03-0.74; p = 0.0201) were significantly associated with postoperatively improved cognition. Although sensitivity, specificity, and positive- and negative-predictive values with the cutoff value lying closest to the upper left corner of a receiver operating characteristic curve for the prediction of postoperatively improved cognition did not differ between postoperative changes in CBF and preoperative cortical magnetic susceptibility, the specificity and the positive-predictive value were significantly greater for the combination of postoperative changes in CBF and preoperative cortical magnetic susceptibility (specificity, 95% CI, 93-100%; positive-predictive value 95% CI, 68-100%) than for the former parameter alone (specificity, 95% CI, 63-88%; positive-predictive value 95% CI, 20-64%). CONCLUSION: Preoperative cortical magnetic susceptibility as well as postoperative changes in CBF are associated with cognitive improvement after CEA.

Effect of three-hour ankle joint immobilization with an ankle foot orthosis on corticospinal excitability and ankle joint angle excursion during gait.

[Purpose] Ankle foot orthosis (AFO) is widely used to regain gait function after injuries and/or stroke; however, limited information is currently available on their effects. We herein examined the effects of three-hour immobilization with AFO on corticospinal excitability and ankle joint movement during gait in healthy volunteers. [Participants and Methods] The participants comprised of seven healthy volunteers. Corticospinal excitability and ankle joint excursions were evaluated before and after three hours of immobilization with left limb AFO. We measured motor evoked potentials in the tibialis anterior (TA) and gastrocnemius (Ga) muscles induced by transcranial magnetic stimulation. In a kinematic analysis, we focused on transition points, such as the timing from dorsiflexion to plantarflexion of the ankle joint and/or vice versa, during gait. [Results] Corticospinal excitability in TA and Ga both significantly decreased. During the normalized gait cycle (GC), ankle angles showed less dorsiflexion at 0% GC and 100% GC, and during loading response and mid-swing and terminal swing phases. Furthermore, less plantarflexion was observed during the initial swing phase. [Conclusion] This study showed that short-term ankle joint immobilization with AFO induces a significant decrease in corticospinal excitability and has an effect on ankle joint excursion during gait. Further studies are needed on the effects of long-term immobilization by AFO.

Obstacle avoidance movement-related motor cortical activity with cognitive task.

Lack of attention to obstacles on the floor or walking path may cause trip and fall accidents. The preparatory activity in the motor cortex to the perturbation associated with obstacle avoidance movements with cognitive task is still unclear. The purpose of this study was to investigate the motor cortical activity involved in the preparation and execution of concurrent obstacle avoidance movement and cognitive task. Twenty young adults were required to step over obstacles that were projected on the floor while performing a cognitive task. The electroencephalogram was recorded, and the movement-related cortical potentials (MRCP) aligned by foot dorsiflexion were evaluated. There was no significant difference in the number of contacts between the toe and the obstacle between the obstacle avoidance task and obstacle avoidance with cognitive task; however, the distance between the toe and the obstacle just before obstacle avoidance movement was significantly extended in the latter task. The amplitude and the onset of MRCP during the dual task were decreased and delayed, respectively, compared with the simple obstacle avoidance movement task. These results suggest that the young participants changed their clearance strategy to stepping over the obstacle during the concurrent motor and cognitive dual task to reduce motor cortical activity.

Computational fluid dynamics simulation wall model predicting air temperature of the nasal passage for nonhuman primates.

OBJECTIVES: Nasal passages adjust the temperature of inhaled air to reach the required body temperature for the lungs. The nasal regions of primates including humans are believed to have experienced anatomical modifications that are adaptive to effective conditioning of the atmospheric air in the habitat for a given species. Measurements of the nasal temperature are required to understand the air-conditioning performance for a given species. Unfortunately, repeated direct measurements within the nasal passage have been technically precluded in most nonhuman primates. MATERIALS AND METHODS: Computational fluid dynamics (CFD) simulation is a potential approach for examining the temperature profile in the nasal passage without any direct measurements. The CFD simulation model mainly comprises a computational model to simulate physiological mechanisms and a wall model to simulate the nasal passage's anatomical and physical properties. We used a computational model developed for humans and examined corrections for the developed wall model based on human properties for predicting its performance in Japanese macaques. RESULTS: This study confirmed that the epithelium layer thickness of the wall model affects the accuracy of the predictions for macaques. A convenient correction of the thickness based on body mass allows us to simulate the actual air temperature profile in macaques' nasal passage. DISCUSSION: The CFD simulations of the wall model corrected with body mass can be applied to other nonhuman primates and mammals. This convenient corrective approach allows us to examine the functional contributions of a specific morphology to the air-conditioning performance without any direct measurements to improve our understanding of primates' functional morphology and physical adaptations to the temperature environment in their habitat.

Assessment of Impaired Cerebrovascular Reactivity in Chronic Cerebral Ischemia using Intravoxel Incoherent Motion Magnetic Resonance Imaging.

BACKGROUND: The severity of chronic cerebral ischemia can be assessed using cerebrovascular reactivity (CVR) to acetazolamide (ACZ) challenge, which is measured by single-photon emission computed tomography (SPECT); however, this is an invasive method. We investigated whether intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) can assess impaired CVR in preoperative patients with chronic cerebral ischemia and compared it to SPECT-CVR. METHODS: Forty-seven patients with unilateral cervical carotid artery stenosis underwent diffusion-weighted MRI with 11 b-values in the range of 0-800 s/mm2 and cerebral perfusion SPECT with the ACZ challenge. The perfusion fraction (f) and diffusion coefficient (D) of the IVIM parameters were calculated using a bi-exponential model. The f and D values and these ratios of the ipsilateral middle cerebral artery territory against the contralateral side were compared with the CVR values of the affected side calculated from the SPECT data. RESULTS: The IVIM-f and D values in the affected side were significantly higher than those in the unaffected side (median: 7.74% vs. 7.45%, p = 0.027; 0.816 vs. 0.801 10-3mm2/s, p < 0.001; respectively). However, there were no significant correlations between the f or D values and SPECT-CVR values in the affected side. In contrast, the f ratio showed a moderate negative correlation with the SPECT-CVR values (r = -0.40, p = 0.006) and detected impaired CVR (< 18.4%) with a sensitivity/specificity of 0.71/0.90. CONCLUSION: The IVIM perfusion parameter, f, can noninvasively assess impaired CVR with high sensitivity and specificity in patients with unilateral cervical carotid artery stenosis.

Detection of impaired cerebrovascular reactivity in patients with chronic cerebral ischemia using whole-brain 7T MRA.

BACKGROUND: Cerebrovascular reactivity (CVR) to acetazolamide (ACZ) on single-photon emission computed tomography (SPECT) can be used to assess the severity of chronic cerebral ischemia; however, this is an invasive method. We examined whether whole-brain magnetic resonance angiography (MRA) at 7T could non-invasively detect impaired CVR in patients with chronic cerebral ischemia by demonstrating the leptomeningeal collaterals (LMCs). METHODS: Fifty-seven patients with symptomatic unilateral cervical stenosis underwent whole-brain time-of-flight MRA at 7T and cerebral perfusion SPECT before/after the ACZ challenge. MRA images were visually assessed based on 6-point grading systems to evaluate the development of LMCs toward the middle cerebral artery (MCA) and antegrade flow of MCA. CVR of the affected side was calculated from the SPECT data. Subsequently, we compared the LMC grades on MRA with CVR on SPECT. RESULTS: CVR was significantly lower in grades ≥ 2 of LMCs than in grades 0-1 (P < 0.05) when applying LMCs from the anterior cerebral artery (ACA) and/or posterior cerebral artery (PCA). These differences were more evident than those in the grading of the antegrade MCA flow. The LMC grades from ACA/PCA readily detected reduced CVR (< 18.4%) with a sensitivity/specificity of 0.79/0.82. CONCLUSION: The development of LMCs on whole-brain MRA at 7T can non-invasively detect reduced CVR with a high sensitivity/specificity in patients with unilateral cervical stenosis.

Locomotor kinematics and EMG activity during quadrupedal versus bipedal gait in the Japanese macaque.

Several qualitative features distinguish bipedal from quadrupedal locomotion in mammals. In this study we show quantitative differences between quadrupedal and bipedal gait in the Japanese monkey in terms of gait patterns, trunk/hindlimb kinematics, and electromyographic (EMG) activity, obtained from 3 macaques during treadmill walking. We predicted that as a consequence of an almost upright body axis, bipedal gait would show properties consistent with temporal and spatial optimization countering higher trunk/hindlimb loads and a less stable center of mass (CoM). A comparatively larger step width, an ~9% longer duty cycle, and ~20% increased relative duration of the double-support phase were all in line with such a strategy. Bipedal joint kinematics showed the strongest differences in proximal, and least in distal, hindlimb joint excursions compared with quadrupedal gait. Hindlimb joint coordination (cyclograms) revealed more periods of single-joint rotations during bipedal gait and predominance of proximal joints during single support. The CoM described a symmetrical, quasi-sinusoidal left/right path during bipedal gait, with an alternating shift toward the weight-supporting limb during stance. Trunk/hindlimb EMG activity was nonuniformally increased during bipedal gait, most prominently in proximal antigravity muscles during stance (up to 10-fold). Non-antigravity hindlimb EMG showed altered temporal profiles during liftoff or touchdown. Muscle coactivation was more, but muscle synergies less, frequent during bipedal gait. Together, these results show that behavioral and EMG properties of bipedal vs. quadrupedal gait are quantitatively distinct and suggest that the neural control of bipedal primate locomotion underwent specific adaptations to generate these particular behavioral features to counteract increased load and instability. NEW & NOTEWORTHY Bipedal locomotion imposes particular biomechanical constraints on motor control. In a within-species comparative study, we investigated joint kinematics and electromyographic characteristics of bipedal vs. quadrupedal treadmill locomotion in Japanese macaques. Because these features represent (to a large extent) emergent properties of the underlying neural control, they provide a comparative, behavioral, and neurophysiological framework for understanding the neural system dedicated to bipedal locomotion in this nonhuman primate, which constitutes a critical animal model for human bipedalism.

Computational Fluid Dynamics Analysis of Lateral Striate Arteries in Acute Ischemic Stroke Using 7T High-resolution Magnetic Resonance Angiography.

BACKGROUND: Infarcts in the lateral striate artery (LSA) territory can be caused by several pathological changes, including lipohyalinosis and microatheroma. However, fluid dynamic effects on these changes remain unknown. Thus, we investigated whether the fluid dynamic metrics of the LSAs were altered in patients with acute ischemic stroke using computational fluid dynamics (CFD) analysis. METHODS: Fifty-one patients with acute ischemic stroke confined in the basal ganglia and/or corona radiata underwent high-resolution magnetic resonance angiography (HR-MRA) at 7T. We performed CFD analyses to obtain indices including the wall shear stress (WSS), WSS gradient (WSSG), and flow velocity (FV) and compared these values between the ipsilesional and contralesional sides in the patients with infarcts in the LSA or non-LSA territories. RESULTS: In patients with LSA-territory infarcts, the WSS, WSSG, and FV values were significantly lower in the ipsilesional LSAs than in the contralesional LSAs (P = .01-.03), while these values in the proximal middle cerebral arteries showed no significant lateralities. In contrast, in patients with non-LSA-territory infarcts, there were no significant lateralities in the metrics between the ipsilesional and contralesional sides. CONCLUSIONS: The CFD analyses using HR-MRA revealed significantly low WSS and WSSG values of the ipsilesional LSAs compared with that of the contralesional side in patients with LSA-territory infarcts, suggesting that fluid dynamic factors of LSAs can be one of the risk factors for LSA-territory infarctions.

Wall Shear Stress and T1 Contrast Ratio Are Associated With Embolic Signals During Carotid Exposure in Endarterectomy.

Background and Purpose- The frictional force because of blood flow may dislodge masses present on the surface of a plaque. Such frictional force is calculated as wall shear stress (WSS) using computational fluid dynamics. The aims of the present study were to determine whether, in addition to carotid plaque intensity on T1-weighted magnetic resonance (MR) imaging, WSS calculated using computational fluid dynamics analysis for carotid arteries is associated with development of an embolism during exposure of carotid arteries during carotid endarterectomy. Methods- One hundred patients with internal carotid artery stenosis (≥70%) underwent carotid plaque imaging with MR, and 54 patients with a vulnerable plaque (intraplaque hemorrhage or lipid/necrotic core) displayed as a high-intensity lesion underwent additional cervical 3-dimensional MR angiography. The maximum value of WSS within the most severe stenotic segment of the internal carotid artery was calculated using MR angiography. Transcranial Doppler monitoring of microembolic signals (MES) in the ipsilateral middle cerebral artery was performed during carotid endarterectomy. Results- Although none of the 46 patients with a nonvulnerable carotid plaque had MES during exposure of carotid arteries, 24 of the 54 patients with a vulnerable carotid plaque (44%) had MES. Logistic regression analysis showed that higher plaque intensity ( P=0.0107) and higher WSS ( P=0.0029) were significantly associated with the development of MES. When both cutoff points of plaque intensity and WSS in the receiver operating characteristic curves for predicting development of MES were combined, specificity (from 63% to 93%) and positive predictive value (from 66% to 90%) became greater than those for plaque intensity alone. Conclusions- In addition to carotid plaque intensity on T1-weighted MR imaging, WSS calculated using computational fluid dynamics analysis for carotid arteries is associated with development of an embolism during exposure of carotid arteries during carotid endarterectomy.

Noninvasive Assessment of Oxygen Extraction Fraction in Chronic Ischemia Using Quantitative Susceptibility Mapping at 7 Tesla.

BACKGROUND AND PURPOSE: The oxygen extraction fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET. METHODS: Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template. RESULTS: The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps (r=0.69; P<0.001), especially in patients with a substantial increase in the PET-OEF ratio of 1.09 (r=0.79; P=0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF. CONCLUSIONS: OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.

Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo.

We are flat-faced hominins with an external nose that protrudes from the face. This feature was derived in the genus Homo, along with facial flattening and reorientation to form a high nasal cavity. The nasal passage conditions the inhaled air in terms of temperature and humidity to match the conditions required in the lung, and its anatomical variation is believed to be evolutionarily sensitive to the ambient atmospheric conditions of a given habitat. In this study, we used computational fluid dynamics (CFD) with three-dimensional topology models of the nasal passage under the same simulation conditions, to investigate air-conditioning performance in humans, chimpanzees, and macaques. The CFD simulation showed a horizontal straight flow of inhaled air in chimpanzees and macaques, contrasting with the upward and curved flow in humans. The inhaled air is conditioned poorly in humans compared with nonhuman primates. Virtual modifications to the human external nose topology, in which the nasal vestibule and valve are modified to resemble those of chimpanzees, change the airflow to be horizontal, but have little influence on the air-conditioning performance in humans. These findings suggest that morphological variation of the nasal passage topology was only weakly sensitive to the ambient atmosphere conditions; rather, the high nasal cavity in humans was formed simply by evolutionary facial reorganization in the divergence of Homo from the other hominin lineages, impairing the air-conditioning performance. Even though the inhaled air is not adjusted well within the nasal cavity in humans, it can be fully conditioned subsequently in the pharyngeal cavity, which is lengthened in the flat-faced Homo. Thus, the air-conditioning faculty in the nasal passages was probably impaired in early Homo members, although they have survived successfully under the fluctuating climate of the Plio-Pleistocene, and then they moved "Out of Africa" to explore the more severe climates of Eurasia.

Minor contributions of the maxillary sinus to the air-conditioning performance in macaque monkeys.

The nasal passages mainly adjust the temperature and humidity of inhaled air to reach the alveolar condition required in the lungs. By contrast to most other non-human primates, macaque monkeys are distributed widely among tropical, temperate and subarctic regions, and thus some species need to condition the inhaled air in cool and dry ambient atmospheric areas. The internal nasal anatomy is believed to have undergone adaptive modifications to improve the air-conditioning performance. Furthermore, the maxillary sinus (MS), an accessory hollow communicating with the nasal cavity, is found in macaques, whereas it is absent in most other extant Old World monkeys, including savanna monkeys. In this study, we used computational fluid dynamics simulations to simulate the airflow and heat and water exchange over the mucosal surface in the nasal passage. Using the topology models of the nasal cavity with and without the MS, we demonstrated that the MS makes little contribution to the airflow pattern and the air-conditioning performance within the nasal cavity in macaques. Instead, the inhaled air is conditioned well in the anterior portion of the nasal cavity before reaching the MS in both macaques and savanna monkeys. These findings suggest that the evolutionary modifications and coetaneous variations in the nasal anatomy are rather independent of transitions and variations in the climate and atmospheric environment found in the habitats of macaques.

Flow Diversion Effect in a Saphenous Vein Graft Aneurysm Using a Double-Layer Micromesh Stent: A Case Report.

BACKGROUND AND IMPORTANCE: A double-layer micromesh stent is designed for the treatment of carotid artery stenosis that has been reported to potentially provide a flow diversion effect. However, the actual flow diversion effect of stents remains unclear. Here, we present a case of a growing saphenous vein graft (SVG) aneurysm treated with the placement of the double-layer micromesh stent using its flow diversion effect. CLINICAL PRESENTATION: A 66-year-old woman, who underwent high-flow bypass using a SVG for a blister-like internal carotid artery aneurysm 13 years earlier at our institute, was referred to our hospital with a pulsatile cervical mass. Magnetic resonance angiography showed a 9-mm aneurysm on the left SVG, although the aneurysm was a small pouch 4 years earlier. Digital subtracted angiography demonstrated a 9.4 × 8.3-mm aneurysm from the SVG at the auricular level. Because the diameter of the graft was larger than that of the available flow diverter stents in Japan, we decided to place the double-layer micromesh stent (CASPER RX, 7 × 25 mm MicroVention) using its flow diversion effect. Computational fluid dynamics analysis before and after stent deployment showed a significant reduction in the average flow velocity and wall shear stress in the aneurysm, indicating actual flow diversion. An angiogram 2 months postoperatively showed complete obliteration of the aneurysm. CONCLUSION: Obliteration of the saphenous vein aneurysm was achieved because of the flow diversion effect of the double-layer micromesh stent. The stents might be a feasible alternative for treating cervical carotid aneurysms.

Diagnostic accuracy of preoperative quantitative susceptibility mapping for detecting histologic intraplaque hemorrhage in cervical ICA stenosis in patients undergoing carotid endarterectomy.

BACKGROUND AND PURPOSE: Quantitative susceptibility mapping (QSM) has been proposed to assess intraplaque hemorrhage (IPH) in the carotid artery. The purpose of this study was to compare the diagnostic accuracy of preoperative QSM with that of the conventional T1-weighed (T1W) three-dimensional (3D)-FSE sequence for detecting IPH in cervical ICA stenosis in patients undergoing carotid endarterectomy (CEA) using histology as the reference standard. MATERIALS AND METHODS: Carotid T1W 3D-FSE and QSM images were obtained from 16 patients with cervical ICA stenosis before CEA. Relative signal intensity (RSI) and susceptibility of the ICA were measured on three axial images including the location of most severe stenosis on T1W 3D-FSE and QSM images, respectively. Three transverse sections of carotid plaques excised by CEA, which corresponded with images on MRI, were stained with H&E, antibody against glycophorin A and Prussian blue, and the relative area (RA) of histologic IPH was calculated. RESULTS: The correlation coefficient was significantly greater between susceptibility and RA-histologic IPH (ρ = 0.691) than between RSI and RA-histologic IPH (ρ = 0.413; P = .0259). The areas under the receiver operating characteristic curves for detecting histologic sections consisting primarily of IPH (RA-histologic IPH > 40.7%) tended to be greater for susceptibility (0.964) than for T1WI FSE-RSI (0.811). Marginal homogeneity was observed between susceptibility and histologic sections consisting primarily of IPH (P = .0412) but not between T1W FSE-RSI and histologic sections consisting primarily of IPH (P = .1824). CONCLUSIONS: Pre-CEA QSM detects histologic IPH in cervical ICA stenosis more accurately than preoperative T1W 3D-FSE imaging. ABBREVIATIONS: QSM = quantitative susceptibility mapping; IPH = intraplaque hemorrhage; T1W = T1-weighed; 3D = three-dimensional; CEA = carotid endarterectomy; RSI = relative signal intensity; RA = relative area.

Transcranial direct current stimulation to dorsolateral prefrontal cortex improves performance of obstacle avoidance gait task.

We aimed to investigate the effect of dual-task interference between cognitive and obstacle avoidance walking tasks, and the effect of transcranial direct current stimulation (tDCS) on the performance of this cognitive-motor dual task. The healthy young subjects participated in a single task consisting of a three-digit subtraction task (e.g. 783 - 7) or a 15-m track with six 7.5-cm high obstacles. Then, the subjects performed two single tasks simultaneously as dual tasks, before and after sham and anodal tDCS (2 mA, 20 min) to left dorsolateral prefrontal cortex (DLPFC, the F3 region of the 10/20 electroencephalogram electrode placement system). The effect of tDCS on each outcome (number of correct answers, the clearance height above the obstacle, and foot placement position) was analyzed using repeated-measures analysis of variance. Model effects included tDCS (real, sham), time (pre-, post-tDCS), and task (single task, dual task) conditions. A significant difference in the tDCS, time, and task conditions was observed; the correct number of subtraction tasks increased, and the clearance height and the distance between the obstacle and foot decreased in front of the obstacle. Our findings suggest that dual task performance is causally related to left DLPFC activation under complicated walking tasks and tDCS over this cortical area increases overloaded its information processing capacity.

Evaluation of High Intracranial Plaque Prevalence in Type 2 Diabetes Using Vessel Wall Imaging on 7 T Magnetic Resonance Imaging.

BACKGROUND: While type 2 diabetes (T2D) is a major risk for ischemic stroke, the associated vessel wall characteristics remain essentially unknown. This study aimed to clarify intracranial vascular changes on three-dimensional vessel wall imaging (3D-VWI) using fast spin echo by employing 7Tesla (7T) magnetic resonance imaging (MRI) in T2D patients without advanced atherosclerosis as compared to healthy controls. METHODS: In 48 T2D patients and 35 healthy controls, the prevalence of cerebral small vessel diseases and intracranial plaques were evaluated by 3D-VWI with 7T MRI. RESULTS: The prevalence rate of lacunar infarction was significantly higher in T2D than in controls (n = 8 in T2D vs. n = 0 in control, p = 0.011). The mean number of intracranial plaques in both anterior and posterior circulation of each subject was significantly larger in T2D than in controls (2.23 in T2D vs. 0.94 in control, p < 0.01). In T2D patients, gender was associated with the presence of intracranial plaques. CONCLUSION: This is the first study to demonstrate the high prevalence of intracranial plaque in T2D patients with neither confirmed atherosclerotic disease nor symptoms by performing intracranial 3D-VWI employing 7TMRI. Investigation of intracranial VWI with 7T MRI is expected to provide novel insights allowing early intensive risk management for prevention of ischemic stroke in T2D patients.

Using Phase Difference Information to Detect Errors in the Flip Angle Measured with Actual Flip Angle Imaging at 7T.

Flip angle (FA) measurements using the actual flip angle imaging (AFI) method may induce significant errors in ultrahigh fields. We aimed to develop a method for detecting errors in FA measurements using phase information at 7 tesla. We performed computer simulations to elucidate the relationship between the FA calculation errors and the phase difference between the two AFI source images. We then examined whether a method based on the phase difference could detect FA calculation errors and determine the prescribed nominal FA of the scanner for accurate measurements in phantoms and healthy volunteers. The simulations confirmed that the calculated FA values erroneously decreased when the longitudinal magnetization and phase in one of the source images were inverted. Tests on phantoms and human subjects demonstrated that the phase difference information between the source images with a cut-off of 90° could readily detect FA calculation errors in the AFI method.

Distribution of dendrites from longissimus lumborum motoneurons stained intracellularly with biocytin in adult cats.

The three-dimensional distribution of dendrites from motoneurons innervating longissimus lumborum (Long Motoneurons) in the L4 spinal segment was examined in the adult cat using intracellular staining techniques. Long Motoneurons were electrophysiologically identified, stained with injection of biocytin and reconstructed from serial histological sections. Somas of Long Motoneurons were mainly located in the lateral-ventral area of the ventral horn. The dendritic distribution followed an orderly pattern in all motoneurons examined. Long Motoneurons showed a multi-directional distribution of dendrites, and the dendritic distribution pattern varied depending on the motoneuron. All studied motoneurons distributed dendrites from the spine into the white matter. The most significant morphological characteristic of the Long Motoneurons was the variation in their dendritic distribution. No relationship was observed between the effects of peripheral afferent inputs from the hindlimb and morphological characteristics of motoneurons.