Flow Density in Optical Coherence Tomography Angiography is Useful for Retinopathy Diagnosis in Diabetic Patients.

Our study evaluated the diagnostic capability of flow density (FD) in OCT angiography (OCTA) for diabetic retinopathy (DR) detection in diabetic patients. We studied 93 eyes of 68 diabetic patients who underwent OCTA (36 and 57 eyes without and with DR, respectively). Retinal capillary FD of a 2.6 × 2.6 mm2 area and four divided areas at the superficial (SCP) and deep capillary plexus (DCP) were measured. Predictions were evaluated using the area under the receiver operating characteristic curve (AUC). The diagnostic capabilities of the FDs in discriminating between eyes without DR and eyes with total or early DR were compared. Furthermore, predictions with foveal avascular zone (FAZ) area, hemoglobin A1c (HbA1c), and DM duration were also compared with FD. Prediction using FD AUC in the temporal side in the DCP (0.83) was the highest and significantly better than all other AUCs examined (P < 0.05), including discriminating between eyes without DR and with early DR (P < 0.01). Prediction using this particular AUC was also significantly better than that by FAZ area and HbA1c (P < 0.001 and <0.001, respectively). Area-divided FD in OCTA may be valuable for diagnosing retinopathy in diabetic patients.

Optical Coherence Tomography Angiography Reveals Spatial Bias of Macular Capillary Dropout in Diabetic Retinopathy.

Purpose: Our purpose is to evaluate the spatial bias of macular capillary dropout accompanying diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA). Methods: This study included 47 patients with diabetes and 29 healthy individuals who underwent OCTA. Retinal capillary flow density (FD) of 2.6 × 2.6 or 5.2 × 5.2 mm foveal area as well as the four divided areas (superior, inferior, temporal, nasal) without a foveal avascular zone (FAZ) at the superficial capillary plexus and deep capillary plexus (DCP) were measured respectively using ImageJ and NI Vision. Spatial biases of FD (orientation bias ratio and hierarchical bias ratio) and the correlation between FAZ and FD were examined. Results: OCTA showed focal capillary dropout in DR patients. The orientation bias of FD was significantly higher in NPDR compared to NDR in the DCP (P = 0.03). The hierarchical bias of FD was significantly shifted to a DCP dominance with progression of DR (P < 0.01). In addition, the FD and FAZ area were significantly inversely correlated in both plexus in DR patients but not in healthy subjects (P < 0.01). Conclusions: Area-divided OCTA quantification shows the appearance of spatial biases of macular capillary dropout with the onset of DR, suggesting that DR-related macular capillary dropout occurs locally and randomly. Future studies are necessary to determine the clinical relevance of the spatial pattern of capillary dropout in DR.

Imaging of Retinal Vascular Layers: Adaptive Optics Scanning Laser Ophthalmoscopy Versus Optical Coherence Tomography Angiography.

PURPOSE: Retinal vascular networks are observed as a layered structure residing in a nerve fiber layer and an inner nuclear layer of the retina. This study aimed to evaluate reflectance confocal adaptive optics scanning laser ophthalmoscopy (AO-SLO) for imaging of the layered retinal vascular networks. METHODS: This study included 16 eyes of 16 healthy cases. On the fovea, 2.8- and 3.0 mm2-areas were imaged using a prototype AO-SLO and optical coherence tomography angiography (OCTA), respectively. AO-SLO images focused on the nerve fiber and photoreceptor layers were recorded in the area. Two different vessel images (capillary networks in the superficial layer and in all layers) were generated to examine if the deep capillary network could be distinguished. We compared AO-SLO with OCTA in imaging of the layered retinal vascular networks. RESULTS: Sufficient images of capillary networks for analysis could be generated when the motion contrast was enhanced with AO-SLO movies in seven cases (43.8%). The deep capillary network could be distinguished in the merged image. Vascular depiction performance in AO-SLO was significantly better than in OCTA at both 0.5- and 1.0-mm areas from the fovea (P < 0.05). CONCLUSIONS: Retinal vascular imaging using AO-SLO might be a useful adjunct to OCTA as a supportive method to evaluate the retina in healthy patients and patients with disease. TRANSLATIONAL RELEVANCE: In cases requiring accurate and detailed retinal vasculature observation, AO-SLO might be useful for evaluating retinal vascular lesions as a supportive imaging method of OCTA.

Short circuit in deep brain stimulation.

OBJECT: The authors undertook this study to investigate the incidence, cause, and clinical influence of short circuits in patients treated with deep brain stimulation (DBS). METHODS: After the incidental identification of a short circuit during routine follow-up, the authors initiated a policy at their institution of routinely evaluating both therapeutic impedance and system impendence at every outpatient DBS follow-up visit, irrespective of the presence of symptoms suggesting possible system malfunction. This study represents a report of their findings after 1 year of this policy. RESULTS: Implanted DBS leads exhibiting short circuits were identified in 7 patients (8.9% of the patients seen for outpatient follow-up examinations during the 12-month study period). The mean duration from DBS lead implantation to the discovery of the short circuit was 64.7 months. The symptoms revealing short circuits included the wearing off of therapeutic effect, apraxia of eyelid opening, or dysarthria in 6 patients with Parkinson disease (PD), and dystonia deterioration in 1 patient with generalized dystonia. All DBS leads with short circuits had been anchored to the cranium using titanium miniplates. Altering electrode settings resulted in clinical improvement in the 2 PD cases in which patients had specific symptoms of short circuits (2.5%) but not in the other 4 cases. The patient with dystonia underwent repositioning and replacement of a lead because the previous lead was located too anteriorly, but did not experience symptom improvement. CONCLUSIONS: In contrast to the sudden loss of clinical efficacy of DBS caused by an open circuit, short circuits may arise due to a gradual decrease in impedance, causing the insidious development of neurological symptoms via limited or extended potential fields as well as shortened battery longevity. The incidence of short circuits in DBS may be higher than previously thought, especially in cases in which DBS leads are anchored with miniplates. The circuit impedance of DBS should be routinely checked, even after a long history of DBS therapy, especially in cases of miniplate anchoring.

The effect of CyberDome, a novel 3-dimensional dome-shaped display system, on laparoscopic procedures.

BACKGROUND: Laparoscopic surgeons require extended experience of cases to overcome the lack of depth perception on a two-dimensional (2D) display. Although a three-dimensional (3D) display was reported to be useful over two decades ago, 3D systems have not been widely used. Recently, we developed a novel 3D dome-shaped display (3DD) system, CyberDome. STUDY DESIGN: In the present study, a total of 23 students volunteered. We evaluated the effects of the 3DD system on depth perception and laparoscopic procedures in comparison with the 2D, a conventional 3D (3DP) or the 2D high definition (HD) systems using seven tasks. RESULTS: The 3DD system significantly improved depth perception and laparoscopic performance compared with the 2D system in six new tasks. We further found that the 3DD system shortened the execution time and reduced the number of errors during suturing and knot tying. The 3DD system also provided more depth perception than the 3DP and 2D HD systems. CONCLUSIONS: The novel 3DD system is a promising tool for providing depth perception with high resolution to laparoscopic surgeons.

The frontal cortex is activated during learning of endoscopic procedures.

BACKGROUND: To date, several training and evaluation systems for endoscopic surgery have been developed, such as virtual-reality simulators and box trainers. However, despite current advances in these objective assessments, no functional brain studies during learning of endoscopic surgical skills have been carried out. In the present study, we investigated cortical activation using near-infrared spectroscopy (NIRS) during endoscopic surgical tasks. STUDY DESIGN: A total of 21 right-handed subjects, comprising 4 surgical experts, 4 trainees, and 13 novices, participated in the study. Suturing and knot-tying tasks were performed in a box trainer. Cortical activation was assessed in all subjects by task-related changes in hemoglobin (Hb) oxygenation using NIRS. RESULTS: In surgical experts and novices with no experience of endoscopic surgical training, we found no changes in oxy-Hb, deoxy-Hb or total-Hb levels in any of the frontal channels. In surgical trainees and one novice with experience of endoscopic surgical training, we found significant increases in oxy-Hb and total-Hb levels in most of the frontal channels. There were significant differences in oxy-Hb and total-Hb levels in CH-19 between surgical experts and trainees (p = 0.02 for both), and between surgical trainees and novices with no experience of endoscopic surgical training (p = 0.008 for both). Furthermore, additional training increased oxy-Hb levels in the frontal cortex of novices with no experience of endoscopic surgical training but had no such effect on surgical experts. CONCLUSIONS: The present data suggest that NIRS is a feasible tool for assessing brain activation during endoscopic surgical tasks, and may have a large impact on the future development of teaching, training, and assessment methods for endoscopic surgical skills.

The numeric calculation of eddy current distributions in transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a method to stimulate neurons in the brain. It is necessary to obtain eddy current distributions and determine parameters such as position, radius and bend-angle of the coil to stimulate target area exactly. In this study, we performed FEM-based numerical simulations of eddy current induced by TMS using three-dimentional human head model with inhomogeneous conductivity. We used double-cone coil and changed the coil radius and bend-angle of coil. The result of computer simulation showed that as coil radius increases, the eddy current became stronger everywhere. And coil with bend-angle of 22.5 degrees induced stronger eddy current than the coil with bendangle of 0 degrees. Meanwhile, when the bend-angle was 45 degrees, eddy current became weaker than these two cases. This simulation allowed us to determine appropriate parameter easier.

Measurement of evoked potential in recognition of faces and buildings.

In the functional neuro-imaging, it is known that the activation to the second stimulus is suppressed when two stimuli are given successively with a short interval as sensory inputs. This kind of suppressive phenomenon has been observed in event-related potential (ERP) signals as well as functional MRI signals of primary auditory, somatosensory and visual cortices. However, we rarely find reports to ERP suppression in higher-order areas of the brain. In this study we used a paired stimulus paradigm. The paired stimulus paradigm consisted of successively presented two stimuli in one trial. We recorded ERP related to recognition of faces and buildings to investigate the suppressive phenomenon in higher-order areas of the brain. We used the paired stimulus paradigm which was comprised of face, building and gray-colored-plain (gray) pictures. The inter-stimulus interval of two stimuli was 200 ms. On the points of O2 and T6, we observed that the ERP for the latter stimulus (face picture) was suppressed severely when a face-gray stimulus pair was presented. On the other hand, when a gray-building stimulus pair was presented, the ERP for the latter stimulus (building picture) was not suppressed on the points of O2 and T6. The similar suppression was observed with a face-face stimulus pair.

Measurements of the micro/beta ERD and gamma ERS during the imagination of body parts movement.

In recent years, many studies shows that the ERS (event-related synchronization) in the gamma band is associated with cortical activation during the imagination of body parts movement. It is also known that the ERD (event-related desynchronization) in the micro and beta band are caused by the imagination of body parts movement. In this study, we investigated the relationship between the gamma ERS and micro/beta ERDs. We recorded 64-channel EEG in order to obtain the power map of the gamma component. Furthermore, we compared the characteristics of the gamma waveform and micro/beta waveforms at the locations where the gamma ERS appeared clearly. As a result, we obtained three conclusions. Firstly, gamma ERS caused by the imagination of body parts movement appears at near somatosensory area and motor area. Gamma ERS caused by the imagination of right arm movement appears at the left side of the somatosensory area, that of left arm movement appears at the right side of the somatosensory area, and that of the foot movement appears at the center of the motor area. Secondly, micro/beta ERDs appear simultaneously with the preparation of the imagination, and they continue during the imagination. However, gamma ERS appeared simultaneously with the imagination of body parts movement. Finally, the power of the micro/beta component decrease gradually, but that of the gamma component increases significantly.

Simulation study on the effect of fiber loss to the compound action potential of a sural nerve.

This paper reports the result of computer simulation about compound action potential of a sural nerve with and without fiber loss. A compound action potential is a wave of electric potential detectable on the skin after electric stimulation of a peripheral nerve. The loss of nerve fibers, which is observed in some neuropathies, is considered as the cause of low amplitude and slow conduction of the wave. To quantify the relationship between fiber loss and compound action potential, computer simulation of the stimulation of a human sural nerve was executed. As a result, the conduction velocity of the first negative peak of the compound action potential was substantially reduced in case of thick fiber loss, and was slightly enlarged in case of thin fiber loss. However the amplitude of the peak was not always reduced. The effect of thin fiber loss was observed in the amplitude of the second positive peak and the second negative peak.

NIRS measurement of hemodynamic evoked responses in the primary sensorimotor cortex.

To investigate the relationship between neuronal activity and hemodynamics, we carried out a near-infrared spectroscopy (NIRS) study to measure the regional changes of hemoglobin concentration associated with cortical activation in the human sensorimotor cortex (SMI) to both voluntary and nonvoluntary tasks. We measured the hemodynamic evoked responses to voluntary finger movement and nonvoluntary electrical stimulation applied on the fingers (thumb and ring finger, respectively). Measurements were performed on 6 healthy right-handed volunteers using block paradigms and we analyzed both the spatial/temporal features and the magnitude of the optical signal induced by cerebral activation during these protocols. We constantly observed an increase in the cerebral concentration of oxygenated hemoglobin at the cortical side contralateral to the stimulated side. Our findings are in agreement with results in positron emission tomography (PET), functional magnetic resonance imaging (fMRI) and EEG (Electroencephalogram).

EEG source estimation method considering the shape of the cortical surface.

The precision of current source estimation of electroencephalography by referring the shape of the brain acquired as MRI was considered. The location of the candidate current dipoles was limited to on the surface of the cortex, and the orientation was constrained to the vertical to the surface. Electric stimulation of median nerve was executed to confirm whether it works appropriately by checking the estimated active area on the cortex.

An ellipsoidal trajectory model for measuring the line of sight.

The relationship between the amount of rotation of the eyeball and the amount of rotation of the line of sight was investigated. The planar model and ellipsoidal model were compared as the trajectory of the center of the pupil. An evaluation of precision was carried out by measuring the discrepancy between the direction of the target and the estimated direction of the line of sight. The experimental results showed that the planar model was more precise than the ellipsoidal model. The center of rotation of the eyeball seems to translate along the oblique rotation of the eyeball.