Michael Bodo, Ryan Sheppard, Aaron Hall, Martin Baruch, Melissa Laird, Shravalya Tirumala and Richard Mahon
Applications of rheoencephalography for monitoring cerebral blood flow autoregulation
The goal of neuromonitoring in both the neurosurgery intensive care unit, during transport of wounded military service members is to prevent brain damage that may occur due to failure of CBF AR. Currently, there is no single measuring modality capable of monitoring for such brain injuries as hypoxia, ischemia, elevated ICP, edema, intracranial hemorrhage, vasospasm.
CBF AR reflects the ability of the brain to keep brain blood flow relatively constant despite
Leslie D. Montgomery, Richard W. Montgomery, Wayne A. Gerth, Marty Loughry, Susie Q. Lew and Manuel T. Velasquez
in the body and may be a valuable aid in clinical diagnosis and research.
Two different types of bioelectric impedance instruments are available. Fixed frequency bioelectrical impedance plethysmographic (IPG) techniques are valuable noninvasive tools that provide information about overall segmental volumes, blood flows, and hemodynamic status with a high degree of temporal resolution [ 9 , 10 , 11 , 12 ]. The second type, electrical bioimpedance spectroscopy (BIS) [ 13 , 14 ] is a multifrequency technique that, when coupled with computeraided equivalent
Michael Bodo, Leslie D. Montgomery, Frederick J. Pearce and Rocco Armonda
Relationship between Hemorrhage and Cerebral Blood Flow
Hemorrhagic shock (hypotension) is the leading cause of death in both civilian and military injuries. A patient with both a severe head injury and hypotension is four times more likely to die than a patient with a head injury alone ( Manley et al, 2001 ). Despite the brain’s well developed autoregulation ( Strandgaard, Paulson, 1984 ), its vital functions are impaired when the CBF autoregulatory reserve is exhausted by prolonged hypovolemic conditions (hemorrhage).
Afferent neural input to the brain seems to be
Leslie D. Montgomery, Richard W. Montgomery, Wayne A. Gerth, Michael Bodo, Julian M. Stewart and Marty Loughry
of vital signs such as heart rate, blood pressure, temperature, and respirations comprise the hemodynamic quantities classically evaluated in hemorrhagic shock, these quantities mostly reflect the integrated effects of fundamental changes in blood flows and blood volumes that are progressively perturbed during the stages of blood loss. Thus in their classic review of the hemodynamic and neuroendocrine consequences of hemorrhagic hypovolemia, Schadt and Ludbrook [ 1 ] refer to the earlier human venesection studies of Barcroft [ 2 ] in which rapid and highly
Michael Bodo, Richard Mahon, Alex Razumovsky, Efim Kouperberg, Michael Crimmins, Rocco Armonda and Martin Baruch
of rheoencephalography for noninvasive continuous brain monitoring, including enhanced computational methods, animal studies and clinical monitoring studies of humans.
Positive characteristics of REG are that it is noninvasive and is easy and inexpensive to administer continuously. However, before the availability of computerized data processing techniques, the usefulness of REG for neuromonitoring was limited since REG does not reflect absolute blood flow or provide direct diagnostic information; in addition, the REG signal may be contaminated by artifacts due
Reda Abdelbaset, Mohamed El Dosoky and Mohamed T. El-Wakad
current and the generated electric field. The laminar flow module is selected to simulate and calculate the characteristics of blood motion based on its fluid dynamic properties. The frequency domain study is favored in order to compute the generated electric field at a specific range of frequencies. The laminar flow is used to simulate the motion of blood. The time-dependent study is preferred to compute the change in the motion of blood over time.
The processing stage
As shown in Fig.1 , the processing stage contains: firstly, the geometry: which contains the
bioimpedance considering a forearm section. This can provide an insight to the arm tissue behavior along with the individual contribution of different layers (along with blood flow) to the impedance variations. Also, the forearm provides a simpler and justifiable site for PWV measurement
The objective of this work is to simulate the electrical response of a section of human forearm and obtain the values of impedance over a wide frequency range. These simulation results will be compared to the Cole type response. The simu-lation would be performed at three instances of
Silviu Dovancescu, Salvatore Saporito, Ingeborg H. F. Herold, Hendrikus H. M. Korsten, Ronald M. Aarts and Massimo Mischi
pulmonary vasculature. The ability to detect the accumulation of these small fluid volumes may allow early medical interventions.
A major challenge of studies that use segmental bioimpedance measurements in the assessment of fluid status is the lack of an adequate reference for changes in fluid volume in the segment of interest, e.g. the lungs. This shortcoming may be addressed by magnetic resonance imaging (MRI), which is a minimally invasive technique that has the ability to quantify the pulmonary fluid volume. To this aim, MRI uses measurements of blood flow based on
own advantages and disadvantages. The electrical impedance method has been suggested as an alternative method with the advantages of being non-invasive and relatively cheap [ 2 ]. This method involves applying alternating current to the region of interest, by direct injection via skin electrodes and extracting information about the inner bioelectrical properties distribution through the measurements of the developing surface electrical potentials due to the current flow [ 3 ].
The region of interest is the forearm, which consists of complex biological tissues such
. High curvature details of process equipment affect the internal flow. Correct information about them allows better models to be developed. True reconstruction of shapes in (b), (c) and (d) is necessary and immensely useful, but EIT reconstruction of these sharp features would smoothen them due to regularization.
We have addressed this issue and suggested a solution to improve the image quality, by proposing a new method to locally relax regularization based on the presence of inclusion. This method is named as DeTER – Detection of Target and Edge Refinement. DeTER