https://staff.aist.go.jp/k.chinzei/pdf/0011_jbiomech.pdf

Mechanical properties of brain tissue in-vivo: experiment and computer simulation

http://iesys.skku.ac.kr/es/International%20Journal/8.pdf

Optimal cylindrical handle diameter for grip force tasks

Partial table of contents: Modelling Cardiac Excitation and Excitability (M. Boyett, et al.). Modelling Propagation in Excitable Media (A. Holden & A. Panfilov). Rotors, Fibrillation and Dimensionality (A. Winfree). A Mathematical Model of Cardiac Anatomy (P. Hunter, et al.). Finite Element Methods for Modelling Impulse Propagation in the Heart (J. Rogers, et al.). The Effects of Geometry and Fibre Orientation on Propagation and Extracellular Potentials in Myocardium (J. Keener & A. Panfilov). Forward and Inverse Problems in Electrocardiography (A. van Oosterom). Computational Electromechanics of the Heart (P. Hunter, et al.). Index.

Computational biology of the heart , edited by Alexander V. Panfilov and Arun V. Holden. Pp. 416. £70. 1997. ISBN 0 471 96020 9 (John Wiley & Sons).

In order to create a useful computational tool that will aid in the understanding and perhaps prevention of head injury, it is important to know the quantitative influence of the constitutive properties, geometry and model formulations of the intracranial contents upon the mechanics of a head impact event. The University College Dublin Brain Trauma Model (UCDBTM) [1] has been refined and validated against a series of cadaver tests and the influence of different model formulations has been investigated. In total six different model configurations were constructed: (i) the baseline model, (ii) a refined baseline model which explicitly differentiates between grey and white neural tissue, (iii) a model with three elements through the thickness of the cerebrospinal fluid (CSF) layer, (iv) a model simulating a sliding boundary, (v) a projection mesh model (which also distinguishes between neural tissue) and (vi) a morphed model. These models have been compared against cadaver tests of Trosseille [2] an...

/pdf/influence-of-fe-model-variability-in-predicting-brain-motion-3yqf82azmp.pdf

Influence of FE model variability in predicting brain motion and intracranial pressure changes in head impact simulations

Establishment of shape during embryonic development, and the maintenance of shape against injury or tumorigenesis, requires constant coordination of cell behaviors toward the patterning needs of the host organism. Molecular cell biology and genetics have made great strides in understanding the mechanisms that regulate cell function. However, generalized rational control of shape is still largely beyond our current capabilities. Significant instructive signals function at long range to provide positional information and other cues to regulate organism-wide systems properties like anatomical polarity and size control. Is complex morphogenesis best understood as the emergent property of local cell interactions, or as the outcome of a computational process that is guided by a physically encoded map or template of the final goal state? Here I review recent data and molecular mechanisms relevant to morphogenetic fields: large-scale systems of physical properties that have been proposed to store patterning information during embryogenesis, regenerative repair, and cancer suppression that ultimately controls anatomy. Placing special emphasis on the role of endogenous bioelectric signals as an important component of the morphogenetic field, I speculate on novel approaches for the computational modeling and control of these fields with applications to synthetic biology, regenerative medicine, and evolutionary developmental biology.

Morphogenetic fields in embryogenesis, regeneration, and cancer: non-local control of complex patterning.

Alterations in the neurovasculature after traumatic brain injury (TBI) represents a significant sequelae. However, despite theoretical and empirical evidence supporting the near-ubiquity of vascular injury, its pathophysiology remains elusive. Although this has been shown for all grades of TBI, the vascular changes after injuries with the broad mild traumatic brain injuries (mTBI) classification, remain particularly difficult to describe. Our group has previously demonstrated hemodynamic alterations in mTBI by utilizing transcranial Doppler ultrasound and cerebrovascular reactivity in a cross-sectional study. That work identified a phasic progression of deviations over varying days post-injury. These phases were then characterized by a set of inverse models that provided a hypothetical process of hemodynamic dysfunction after mTBI. This model set provides a framework with the potential for guiding clinical treatment over the course of recovery. However, it is still unclear if individual patients will progress through the phases of dysfunction similar to that found at the population level. The work presented here explores six individual patients with high-density data collected during their post-injury recovery. Breath-hold index (BHI) was found to be the most robust feature related to mTBI longitudinally. All six subjects exhibited BHI recovery curves that followed the population model's progression. The changes in pulsatile features lacked the universality of BHI, but were present in subjects with higher self-reported symptom scores and longer periods of recovery. This work suggests neurovascular dysfunction after an mTBI may be a robust phenomenon. Additionally, the capabilities of TCD in capturing these changes highlights its potential for aiding clinicians in monitoring patient's recovery post mTBI.

https://journals.sagepub.com/doi/pdf/10.1177/20597002211065855

Longitudinal assessment of hemodynamic alterations after mild traumatic brain injury in adolescents: Selected case study review

Studies on the effects of external pacing of heart suggest that the organ, like the nervous system, possesses properties of memory and adaptation. Changes induced in cardiac activation patterns persist long after the agent that induced those changes is removed. After the effects of stimulation have disappeared, response to the stimulus applied for a second time is much greater than the earlier response. Drawing analogies between communication via gap junctions in cardiac tissue, and via synapses in nervous tissue, we hypothesize that gap junctions also adapt in an activity-dependent manner similar to synapses. With the help of a mathematical model of cardiac cell, the well-known FitzHugh-Nagumo model, we demonstrate that some of the clinically observed manifestations of cardiac memory property can be simulated if gap-junctional conductances are allowed to adapt according to a Hebb-like learning mechanism, a mechanism that successfully accounts for a range of learning and memory phenomena in nervous system.

Activity-Dependent Plasticity In Gap Junctions as a Mechanism for Cardiac Memory

Background: Transcranial Doppler ultrasound (TCD) is utilized in the assessment of neurological conditions in clinical environments such as the intensive care unit and emergency department. However, obstacles for widespread use of TCD include a lack of trained registered vascular technologists (RVT) and operator variability. We present a study comparing RVT and a fully automated robotic TCD system (NovaGuide rTCD) for insonation of the middle cerebral artery (MCA).Methods: A trained RVT and rTCD sequentially collected bilateral MCA cerebral blood flow velocity (CBFV) from 86 healthy subjects. Mean CBFV (mCBFV) and the signal quality assessment (SQA) acquired manually by RVT and autonomously via rTCD were compared. Comparison metrics evaluated include mean accuracy ratio (MAR), and Bland-Altman mean-difference (MD) between rTCD and RVT with paired t-Test for significance. Bootstrapping was used in the accuracy ratio and mean-time to best signal computations to establish 95% confidence intervals.Results: The mCBFVs and SQAs found by rTCD compared to RVT had MAR of 99.7% (97.7-101.7%) and 102.7% (101.1-104.8%), respectively. The rTCD mean-time to best-quality signal was 0.87 min (0.71-1.05) (RVT was not timed). The mean-difference scores for mCBFV and SQA were MD=-0.43cm/s (p=0.053) and MD=-0.36 (p=0.61), respectively. The rTCD had a 3.5% no-window failure rate compared to RVT no-window rate of 4.1%.Conclusion: Comparison of bilateral TCD signals collected by rTCD and RVT demonstrated equivalence in mCBFV and signal quality, suggesting rTCD’s potential to expand utility of TCD in clinical settings that are resource-limited.

/pdf/fully-automated-transcranial-doppler-ultrasound-for-middle-8zpdgvt1.pdf

Fully Automated Transcranial Doppler Ultrasound for Middle Cerebral Artery Insonation

Near infrared (NIR) light in the wavelength range from 700 to 900 nm can pass through skin, bone and other tissues relatively easily. As a result, NIR techniques allow a noninvasive assessment of hemoglobin saturation for a wide range of applications, such as in the study of muscle metabolism, the diagnosis of vascular disorders, brain imaging, and breast cancer detection. Near infrared Spectroscopy (NIRS) is an effective tool to measure the hemoglobin concentration in the tissues, which can discriminate optically the oxy- and deoxy- hemoglobin species because of their different near-infrared absorption spectra. 
We have developed an NIRS probe consisting of a laser diode of 830 nm wavelength and a PIN photodiode in reflectance mode. We have selected a set of healthy volunteers (mean age 30, range 26-40 years) for the study. The probe is placed on forearm of each subject and the backscattered light intensity is measured by occluding the blood flow at 210, 110 and 85 mmHg pressures. Recovery time, peak time and time after 50% release of the cuff pressure are determined from the optical densities during the post occlusive state of forearm. 
These parameters are useful for determining the transient increase in blood flow after the release of blood occlusion. Clinically, the functional aspects of blood flow in the limbs could be evaluated noninvasively by NIRS.

Noninvasive measurement of postocclusive parameters in human forearm blood by near infrared spectroscopy

Background: Diabetic macular edema (DME) is the major cause of visual impairment among patients with diabetic retinopathy. The various treatment modalities available for DME are laser photocoagulation, intravitreal injection of anti-vascular endothelial growth factor drugs, and ocular corticosteroids. Usage of intravitreal injections of triamcinolone acetonide has shown to improve vision by reducing macular thickness and the benefits persisted for a longer duration. Aim: The aim is to evaluate the efficacy and safety of intravitreal triamcinolone acetonide in the management of recalcitrant DME. Methodology: A prospective interventional study was performed for 2 years among patients with DME at a tertiary care institute in Tamil Nadu. A total of 35 patients satisfying our inclusion and exclusion criteria were included in the study. Intravitreal injection of 0.05 ml (2 mg) of triamcinolone acetonide was given to all our study participants. The two major outcome parameters were best-corrected visual acuity (VA) and the central foveal thickness (CFT). Patients were followed up for 6 months. Results: Best-corrected visual acuity showed a statistically significant improvement till the end of 3 months, whereas the values measured at the end of 6 months showed no statistically significant difference. The reduction of values in CFT was found to be statistically significant both at the end of 3 months as well as at the end of 6 months. Conclusion: Intravitreal triamcinolone injection showed a significant improvement in VA and a reduction in CFT without an increase in intraocular pressure and in the incidence of cataracts.

S. Radhakrishnan

Papers

Longitudinal assessment of hemodynamic alterations after mild traumatic brain injury in adolescents: Selected case study review

Activity-Dependent Plasticity In Gap Junctions as a Mechanism for Cardiac Memory

Fully Automated Transcranial Doppler Ultrasound for Middle Cerebral Artery Insonation

Noninvasive measurement of postocclusive parameters in human forearm blood by near infrared spectroscopy

Efficacy and safety of intravitreal triamcinolone acetonide in the management of recalcitrant diabetic macular edema