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Diffuse Optical Monitoring of Hemodynamic Changes in Piglet Brain with Closed Head Injury

Chao Zhou — 2008-08-18T19:04:56-00:00

in preparation (2008)

Measurement of cranial optical path length as a function of age using phase resolved near infrared spectroscopy.

A Duncan — 2008-08-14T19:11:49-00:00

Pediatric research, Vol. 39, No. 5. (May 1996), pp. 889-894.

Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying the source/ detector separation by a laboratory measured differential path length factor (DPF) which accounts for the increased distance traveled by light due to scattering. DPF has been measured by time of flight techniques on small populations of adults and postmortem infants. The values for adults are greater than those for newborns, and it is not clear how to interpolate the present data for studies on children. Recent developments in instrumentation using phase resolved spectroscopy techniques have produced a bedside unit which can measure optical path length on any subject. We have developed an intensity modulated optical spectrometer which measures path length at four wavelengths. Two hundred and eighty three subjects from 1 d of age to 50 y were studied. Measurements were made at a fixed frequency of 200 MHz and a source detector separation of 4.5 cm. Results suggest a slowly varying age dependence of DPF, following the relation DPF690 = 5.38 + 0.049A0.877, DPF744 = 5.11 + 0.106A0.723, DPF807 = 4.99 + 0.067A0.814, and DPF832 = 4.67 + 0.062A0.819, where DPF690 is the DPF measured at 690 nm and A is age is expressed in years from full term. There was a wide scatter of values, however, implying that ideally DPF should be measured at the time of each study.

Transcranial Optical Monitoring of Cerebral Blood Flow and Hemoglobin Concentration in Acute Stroke Patients during Positional Interventions

Turgut Durduran — 2008-08-12T16:07:53-00:00

Annals of Neurology (2008)

In vivo cerebrovascular measurement combining diffuse near-infrared absorption and correlation spectroscopies

C Cheung — 2008-08-12T00:25:41-00:00

Physics in Medicine and Biology (2001), pp. 2053-2065.

We combine two near-infrared diffuse optical techniques to study variations of blood flow, haemoglobin concentration, and blood oxygen saturation in the functioning rat brain. Diffuse correlation spectroscopy (or flowmetry) monitors changes in the cerebral blood flow, without the use of the principles of tracer clearance, by measuring the optical phase-shifts caused by moving blood cells. Near-infrared absorption spectroscopy concurrently measures tissue absorption at two wavelengths to determine haemoglobin concentration and blood oxygen saturation in this same tissue volume. This optical probe is non-invasive and was employed through the intact skull. The utility of the technique is demonstrated in vivo by measuring the temporal changes in the regional vascular dynamics of rat brain during hypercapnia. Temporal and spatial variations of cerebral blood flow, haemoglobin concentration and blood oxygen saturation during hypercapnia are compared with other measurements in the literature, and a quantitative analysis demonstrating the self-consistency of our combined observations of vascular response is presented.

Diffuse optical measurement of hemoglobin and cerebral blood flow in rat brain during hypercapnia, hypoxia and cardiac arrest.

JP Culver — 2008-08-12T00:21:16-00:00

Vol. 510 (2003), pp. 293-297.

Diffuse Optical Tomography of Cerebral Blood Flow, Oxygenation, and Metabolism in Rat During Focal Ischemia

Joseph Culver — 2008-08-12T00:16:24-00:00

J Cereb Blood Flow Metab, Vol. 23, No. 8. (2003), pp. 911-924.

Non-Invasive Measurements of Tissue Hemodynamics with Hybrid Diffuse Optical Methods.

T Durduran — 2008-08-12T00:11:15-00:00

(2004)

Preoperative measurement of co2 reactivity and cerebral autoregulation in neonates with severe congenital heart defects.

T Durduran — 2008-08-12T00:08:11-00:00

(2007)

Diffuse optical measurement of blood flow, bloodoxygenation, and metabolism in a human brain during sensorimotorcortex activation

Turgut Durduran — 2008-08-11T23:30:52-00:00

Opt. Lett., Vol. 29, No. 15. (2004), pp. 1766-1768.

We combine diffuse optical and correlation spectroscopies to simultaneously measure the oxyhemoglobin and deoxyhemoglobin concentration and blood flow in an adult human brain during sensorimotor stimulation. The observations permit calculation of the relative cerebral metabolic rate of oxygen in the human brain, for the first time to our knowledge, by use of all-optical methods. The feasibility for noninvasive optical measurement of blood flow through the skull of an adult brain is thus demonstrated, and the clinical potential of this hybrid, all-optical noninvasive, methodology can now be explored.

Optical brain imaging in vivo: techniques and applications from animal to man

Elizabeth Hillman — 2008-04-11T21:25:47-00:00

Journal of Biomedical Optics, Vol. 12, No. 5. (2007)

Optical brain imaging has seen 30 years of intense development, and has grown into a rich and diverse field. In-vivo imaging using light provides unprecedented sensitivity to functional changes through intrinsic contrast, and is rapidly exploiting the growing availability of exogenous optical contrast agents. Light can be used to image microscopic structure and function in vivo in exposed animal brain, while also allowing noninvasive imaging of hemodynamics and metabolism in a clinical setting. This work presents an overview of the wide range of approaches currently being applied to in-vivo optical brain imaging, from animal to man. Techniques include multispectral optical imaging, voltage sensitive dye imaging and speckle-flow imaging of exposed cortex, in-vivo two-photon microscopy of the living brain, and the broad range of noninvasive topography and tomography approaches to near-infrared imaging of the human brain. The basic principles of each technique are described, followed by examples of current applications to cutting-edge neuroscience research. In summary, it is shown that optical brain imaging continues to grow and evolve, embracing new technologies and advancing to address ever more complex and important neuroscience questions. ©2007 Society of Photo-Optical Instrumentation Engineers

Non-invasive optical spectroscopy and imaging of human brain function

Arno Villringer — 2008-08-11T22:00:38-00:00

Trends in Neurosciences, Vol. 20, No. 10. (1 October 1997), pp. 435-442.

Brain activity is associated with changes in optical properties of brain tissue. Optical measurements during brain activation can assess haemoglobin oxygenation, cytochrome-c-oxidase redox state, and two types of changes in light scattering reflecting either membrane potential (fast signal) or cell swelling (slow signal), respectively. In previous studies of exposed brain tissue, optical imaging of brain activity has been achieved at high temporal and microscopical spatial resolution. Now, using near-infrared light that can penetrate biological tissue reasonably well, it has become possible to assess brain activity in human subjects through the intact skull non-invasively. After early studies employing single-site near-infrared spectroscopy, first near-infrared imaging devices are being applied successfully for low-resolution functional brain imaging. Advantages of the optical methods include biochemical specificity, a temporal resolution in the millisecond range, the potential of measuring intracellular and intravascular events simultaneously and the portability of the devices enabling bedside examinations.

Real-time optical imaging of experimental brain ischemia and hemorrhage in neonatal piglets.

MR Stankovic — 2008-08-11T21:51:54-00:00

Journal of perinatal medicine, Vol. 27, No. 4. (1999), pp. 279-286.

Our objective was to study the development of experimental brain ischemia and hemorrhage by real-time optical imaging. Optical imaging is based on the ability of near infrared light to non-invasively penetrate through the intact scalp and skull and measure brain concentrations of oxy- and deoxyhemoglobin, dominant brain absorbers. Optical imaging was performed in 7 anesthetized, instrumented, and ventilated newborn piglets subjected to the injection of 0.3 cc of saline followed by 2 cc of blood into the left frontal subcortical brain region via a needle inserted through the skull with stereotactic guidance. The image-acquisition rate of 5.26 images per sec allowed for real-time imaging. The detection threshold of the imager at the estimated depth of 1-1.5 cm was approximately 70 microL for saline and approximately 40 microL for blood. The imager readily detected five subcortical hematomas and two large bilateral subarachnoid hemorrhages. The imager detected a global decrease in brain absorption associated with the volume-injection-related increase in intracranial pressure in the surrounding ipsilateral and contralateral brain. Any decrease in brain absorption is an equivalent to brain ischemia. This study demonstrates the capability of optical imaging in detecting brain ischemia and hemorrhage in real-time with high temporal and spatial resolution.

Noninvasive detection of intracerebral hemorrhage using near-infrared spectroscopy (NIRS)

Hans Hennes — 2008-08-11T21:45:31-00:00

Photon Propagation in Tissues III, Vol. 3194, No. 1. (1998), pp. 42-54.

Changes in cerebral blood volume with changes in position in awake and anesthetized subjects.

AT Lovell — 2008-08-07T21:06:41-00:00

Anesthesia and analgesia, Vol. 90, No. 2. (February 2000), pp. 372-376.

Changes in posture affect cerebral blood volume (CBV), and moderate head-up tilt is used as a therapeutic maneuver to reduce CBV and intracranial pressure. However, CBV is rarely measured in the clinical setting. Near-infrared spectroscopy allows real-time bedside monitoring of cerebral hemodynamics, and we have used this technique to measure changes in CBV with changes in posture in 10 normal subjects and 10 propofol-anesthetized patients. In the awake subjects, changes in CBV were correlated with the degree of table tilt. CBV decreased with 18 degrees head-up tilt and increased with 18 degrees head-down tilt (P < 0.0001, r = -0.924). In anesthetized patients, there were differences between head-up and head-down tilt. In the head-down position, CBV was also correlated with the degree of table tilt (P < 0.001, r = -0.782), whereas there was a clinically insignificant reduction in CBV in the head-up position. Near-infrared spectroscopy allows continuous, real time measurement of changes in CBV at the bedside. IMPLICATIONS: Near-infrared spectroscopy, a bedside technique, has been used to measure changes in cerebral blood volume in normal subjects. We have used the same technique in anesthetized patients and have shown that, when a patient is placed in the head up position, the decrease in cerebral blood volume is attenuated, relative to normal subjects.

A comparison of transcranial Doppler with near infrared spectroscopy and indocyanine green during hemorrhagic shock: a prospective experimental study.

B Bein — 2008-04-23T15:35:39-00:00

Critical care (London, England), Vol. 10, No. 1. (February 2006)

INTRODUCTION: The present study was designed to compare cerebral hemodynamics assessed using the blood flow index (BFI) derived from the kinetics of the tracer dye indocyanine green (ICG) with transcranial Doppler ultrasound (TCD) in an established model of hemorrhagic shock. METHODS: After approval from the Animal Investigational Committee, 20 healthy pigs underwent a simulated penetrating liver trauma. Following hemodynamic decompensation, all animals received a hypertonic-isooncotic hydroxyethyl starch solution and either arginine vasopressin or norepinephrine, and bleeding was subsequently controlled. ICG passage through the brain was monitored by near infrared spectroscopy. BFI was calculated by dividing maximal ICG absorption change by rise time. Mean blood flow velocity (FVmean) of the right middle cerebral artery was recorded by TCD. FVmean and BFI were assessed at baseline (BL), at hemodynamic decompensation, and repeatedly after control of bleeding. RESULTS: At hemodynamic decompensation, cerebral perfusion pressure (CPP), FVmean and BFI dropped compared to BL (mean +/- standard deviation; CPP 16 +/- 5 mmHg versus 70 +/- 16 mmHg; FVmean 4 +/- 5 cm x s(-1) versus 28 +/- 9 cm x s(-1); BFI 0.008 +/- 0.004 versus 0.02 +/- 0.006; p < 0.001). After pharmacological intervention and control of bleeding, FVmean and BFI increased close to baseline values (FVmean 23 +/- 9 cm x s(-1); BFI 0.02 +/- 0.01), respectively. FVmean and BFI were significantly correlated (r = 0.62, p < 0.0001). CONCLUSION: FVmean and BFI both reflected the large variations in cerebral perfusion during hemorrhage and after resuscitation and were significantly correlated. BFI is a promising tool to monitor cerebral hemodynamics at the bedside.

New methods for monitoring cerebral oxygenation and hemodynamics in patients with subarachnoid hemorrhage.

E Keller — 2008-04-23T01:45:02-00:00

Acta neurochirurgica. Supplement, Vol. 82 (2002), pp. 87-92.

Radiographic cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH) do not reflect cerebral hemodynamics and oxygenation and may occur in the absence of clinical deficit and vice-versa. This report is to describe preliminary findings in further development of a non invasive method to estimate regional cerebral oxygenation and perfusion. Measurements were performed with a technique combining near infrared spectroscopy (NIRS) and indocyaningreen (ICG) dye dilution. Successful data analysis has been performed based on the decomposition in pulsatile and non-pulsatile components of NIRS absorption data collected before and during the passage of ICG through the vascular bed under the NIRS-detector. First measurements in patients with CVS suggest that the technique could become a powerful tool in the detection and treatment of CVS. This non invasive technique can be done at the bedside, it seems to be safe, easy to perform and less time-consuming compared to conventional techniques. The influence of extracerebral bone and surface tissue on cerebral NIRS signal has not been clarified yet. Therefore a new subdural NIRS probe has been developed, which gives the opportunity to measure directly the concentration of the chromophores in the brain without the influence of extracerebral contamination. In future comparative measurements with conventional NIRS probes on the scalp will allow to quantify and eliminate extracerebral contamination from the NIRS signal.

Near-infrared spectroscopy use in patients with head injury.

PJ Kirkpatrick — 2008-04-23T01:44:12-00:00

Journal of neurosurgery, Vol. 83, No. 6. (December 1995), pp. 963-970.

A multimodality recording system was used in 14 ventilated patients with closed head injury to assess the potential use of near-infrared spectroscopy (NIRS) in the neurointensive care unit. Signals of intracranial pressure, cerebral perfusion pressure, peripheral oxygen saturation, jugular venous saturation, and NIRS-derived changes in the chromophores of oxy- and deoxyhemoglobin were digitized and recorded. After a review of 886 hours of continuous monitoring, 376 hours were considered free from artifact and were entered for final analysis. In nine of the patients 38 events were recorded that demonstrated clear changes in cerebral perfusion pressure accompanied by hemodynamic changes in middle cerebral artery flow velocity (transcranial Doppler) and cortical perfusion (laser Doppler flowmetry). Near-infrared spectroscopy showed correlated changes in 37 events (97%) whereas jugular venous saturation monitoring registered only 20 (53%). There was associated peripheral oxygen desaturation in eight cases (21%), intracranial hypertension in 10 (26%), and cerebral hyperemia in eight (21%). The remaining 12 events (32%) appeared to be complex changes of uncertain origin. Iatrogenic factors were identified as causative in 14 cases (37%). The potential application of NIRS in adults and the importance of using multiple parameter recording systems in the interpretation of cerebral events are discussed.

The use of near infrared spectroscopy (NIRS) in children after traumatic brain injury: a preliminary report.

PD Adelson — 2008-04-23T00:42:14-00:00

Acta neurochirurgica. Supplement, Vol. 71 (1998), pp. 250-254.

Children commonly develop diffuse cerebral swelling after traumatic brain injury (TBI) which is believed due to a secondary response to the injury. Near infrared spectroscopy (NIRS), a continuous, direct, and noninvasive monitor of cerebral oxygenation and cerebral blood volume (CBV), could be helpful in understanding these secondary responses. The aims of our study were to determine whether NIRS used in children with severe TBI will provide insight into the pathophysiology of injury. Ten children (1 mo to 15 years old) with severe TBI (admission GCS < or = 7) were continuously monitored by NIRS by placing optodes over the frontalparietal region. Relative values of oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and total hemoglobin (THb) were obtained and compared to intracranial pressure (ICP), mean arterial pressure (MAP), electroencephalography (EEG), and arterial PCO2 (PaCO2). Episodes of intracranial hypertension (ICP > 20 Torr [T]), changes in ICP > 10 T, changes in PaCO2 > or = 8 T, and changes in MAP > 20 T frequently resulted in changes in HbO2, Hb, and THb. Hyperventilation with decreased PaCO2 always resulted in cerebral oxygen desaturation irregardless of ICP. Often, high ICP correlated with increased THb and HbO2 indicating increased CBV and cerebrovascular dilatation. In two children, posttraumatic seizures were preceded by an unexplained rapid cerebral hyperoxygenation several hours prior to the onset of the clinical seizures. NIRS reliably detects changes in cerebral hemodynamics in children and may be used to further understand the etiology of the diffuse cerebral swelling seen in children after severe TBI.

Brain oxygenation after experimental closed head injury. A NIRS study.

K van Rossem — 2008-04-23T00:22:04-00:00

Advances in experimental medicine and biology, Vol. 471 (1999), pp. 209-215.

Dynamic changes of cerebral oxygenation measured by brain tissue oxygen pressure and near infrared spectroscopy.

M Holzschuh — 2008-04-22T22:59:30-00:00

Neurological research, Vol. 19, No. 3. (June 1997), pp. 246-248.

The aim of this study was to find out whether a correlation exists between changes in brain tissue oxygen pressure (ti-pO2) and hemoglobin oxygenation (HbO2) measured by near-infrared spectroscopy. We studied 10 patients with severe head injury. A ti-pO2 monitoring device was introduced in the frontal white matter as soon as possible after administration. Additionally a NIRS sensor was placed at the forehead. All data were recorded simultaneously. Changes of the ti-pO2 curve were defined as events with the following criteria: > 10% change from the baseline value, > 3 min duration, clearly not an artifact. 137 events were found with a mean change of ti-pO2 of 8.3 +/- 10.2 mmHg. In 77.4% we observed a corresponding change of the HbO2. In 7 patients we found a good correlation (r > 0.7) between change ti-pO2 and change HbO2. In 3 patients the correlation was poor. The reason for poor correlation might be poor signal quality of the NIRS sensor or inhomogenous distribution of ischemic areas in the whole brain. We conclude that under the condition of a stable NIRS signal and a diffuse brain lesion, changes of ti-pO2 are well reflected by NIRS.

Dynamic correlation between tissue PO2 and near infrared spectroscopy.

RD Rothoerl — 2008-04-22T22:56:18-00:00

Acta neurochirurgica. Supplement, Vol. 81 (2002), pp. 311-313.

Multimodal O2 monitoring including tissue pO2 measurements and near infrared spectroscopy (NIRS) are techniques increasingly employed for monitoring patients on neurosurgical intensive care units. NIRS measures a mixed venous arterial oxygen saturation, whereas tissue pO2 evaluates the oxygen pressure in the white matter. In contrast to the tissue pO2 measurements, the NIRS at the moment has not been completely established in clinical practice. We wanted to evaluate whether both techniques are monitoring different dynamic changes. Thirteen patients were included (SAH n = 3, TBI n = 10), 12 patients were male and 1 was female. Mean age was 34 years with a range from 16-76 years. Tissue pO2 probes (Licox, GMS, Germany) were implanted in the frontal lobe showing most pathological changes on the initial CT scan. A near infrared spectroscopy sensor (Invos, Somanetics, USA) was placed simultaneously at the patient's forehead. Due to the drift of the tissue pO2 probe, only data sets were taken into further account in which a tissue pO2 value above 15 mmHg was measured. 66 data sets were analyzed by calculating the spectral coherence with multi taper methods. The coherence of two independent white noise signals were defined as an observation by chance. The significance level for correlated frequencies was 90%. In the spectral long time regime (frequency > or = 0.02), more than 80% of the data sets showed a higher percentage of correlated frequencies as compared to the observation by chance. The assumption that tissue pO2 and near infrared spectroscopy probes are measuring different dynamic changes in neurosurgical intensive care patients could not be supported by our data.

Near-infrared spectroscopy--not useful to monitor cerebral oxygenation after severe brain injury.

K Büchner — 2008-04-22T22:30:50-00:00

Zentralblatt für Neurochirurgie, Vol. 61, No. 2. (2000), pp. 69-73.

Since its development more than twenty years ago, non-invasive near-infrared-spectroscopy (NIRS) has been widely used to monitor cerebral oxygenation. Despite of its growing number of users, the diagnostic value of near-infrared spectroscopy still remains unclear, especially in case of acute brain injury and long-term neuromonitoring, necessary during intensive care therapy. To evaluate quality and sensitivity of NIRS measurements compared to invasive ICP-, CPP- and regional brain tissue--pO2 (p(ti)O2) monitoring, 31 patients, suffering from severe brain injury due to subarachnoid hemorrhage or severe head injury, were studied. NIRS measurements were only possible in 80% (using the INVOS oximeter) and in 46% (using the CRITIKON monitor), while good data quality was obtained in 100% from ICP, CPP and p(ti)O2. Major reasons for the failure of NIRS measurements were: (1) a wet chamber between sensor and skin, (2) galea hematoma or (3) subdural air after craniotomy. Different tests were performed to compare the sensitivity of regular oxygen saturation (NIRS) with the sensitivity of invasively determined p(ti)O2. Only induced hyperoxia (FiO2 = 1.0) revealed a significant correlation between both parameters (r = 0.67, p < 0.01). Lower or no correlation was found after changing paCO2 and administration of mannitol. The high failure rate and the limited sensitivity does not make the clinical use of near-infrared spectroscopy suitable as a part of neuromonitoring after acute brain injury at the present time.

Near infrared spectroscopy in brain injury: today's perspective.

PG Al-Rawi — 2008-04-22T22:26:01-00:00

Acta neurochirurgica. Supplement, Vol. 95 (2005), pp. 453-457.

The technique of near infrared spectroscopy (NIRS) is based on the principle of light attenuation by the chromophores oxyhaemoglobin (HbO2), deoxyhaemoglobin (Hb) and cytochrome oxidase. Changes in the detected light levels can therefore represent changes in concentrations of these chromophores. Clinical use of NIRS in the brain has been well established in neonates where transillumination is possible. While it has become a useful research tool for monitoring the adult brain, clinical application has been hampered by the fact that it must be applied in reflectance mode. This has resulted in a number of concerns, most significantly the issue of signal contamination by the extracranial tissue layers. Algorithms have been applied to try to overcome this problem, and techniques such as time resolved, phase resolved and spatially resolved spectroscopy have been developed. There has been renewed interest in NIRS as an easy to use, non-invasive technique for measuring tissue oxygenation in the adult brain. Recent technical advances have led to the development of compact, portable instruments that detect changes in optical attenuation of several wavelengths of light. Near infrared spectroscopy is an evolving technology that holds significant potential for technical advancement. In particular, NIRS shows future promise as a clinical tool for bedside cerebral blood flow measurements and as a cerebral imaging modality for mapping structure and function.

Near infrared spectroscopy for evaluation of the trauma patient: a technology review.

KR Ward — 2008-04-22T22:21:54-00:00

Resuscitation, Vol. 68, No. 1. (January 2006), pp. 27-44.

Clinicians now realize the limitations of the physical examination in detecting compensated shock states, the severity of uncompensated states, and in determining the adequacy of resuscitation in order to prevent subsequent post-traumatic multisystem organ failure and death. A renewed interest has developed in interrogating the state of oxygen transport at the end-organ level in the trauma patient. Although used as a research tool and now clinically to monitor cerebral oxygenation during complex cardiovascular and neurosurgery, near infrared absorption spectroscopy (NIRS) is being more aggressively investigated and now marketed clinically as a noninvasive means to assess tissue oxygenation in the trauma patient at the end organ level. This paper will describe the principles of NIRS and the basis for its proposed use in the trauma patient to assess tissue oxygenation. This includes its known limitations, current controversies, and what will be needed in the future to make this technology a part of the initial and ongoing assessment of the trauma patient. The ultimate goal of such techniques is to prevent misassessment of patients and inadequate resuscitation, which are believed to be major initiators in the development of multisystem organ failure and death.