Reviews for Korean Brain Camp:

Transcription

1 Reviews for Korean Brain Camp: Introduction to Brain Engineering Prof. Dong-Joo Kim Department of Brain and Cognitive Engineering, Korea University

2 Section 1: NEURO-IMAGING Part 1-1: Imaging Modalities Coles, J. P. & Menon, D. K. Imaging. In: Matta, B. F., Menon, D. K. & Smith, M. (Eds.). Core topics in neuroanaesthesia and neurointensive care. Cambridge University Press (2011)

3 Structural imaging: X-ray, CT, MRI, angiography Structural Imaging FIGURE Neuroscience techniques differ in their spatial resolution, temporal resolution, and invasiveness Huettel SA, Song AW and McCarthy G (2009)

4 Structural Imaging: X-rays and CT X-rays : passing through the patient (or subject), generate a projection image CT (Computed Tomography) : recording a series of coplanar projections by rotating the source and detector around the patient Recorded projections are then used to recover the X-ray attenuation of each point in the plane

5 Computed Tomography CT has replaced the use of plain skull radiographs and is routinely used to assess all patients with acute neurological injury and head trauma Early assessment of the extent of injury Can be obtained quickly using multi-detector high-resolution scanners Imaging data can be visualized using brain or bone contrast windows and reconstructed into 3D CT datasets in order to demonstrate bony injury and intracranial pathology FIGURE 3D CT reconstruction. This patient sustained injury following a road traffic accident. The reconstruction allowed operative planning of the cranial and facial fractures. Thanks to J. P. Coles and D. K. Menon

6 CT scans: guideline for patients with head injury Following head injury, CT scan should be obtained if any of the following is present Glasgow Coma Score (GCS) < 13 at any point since the injury GCS equal to 13 or 14 at 2 hrs after the injury Suspected open or depressed skull fracture Any sign of basal skull fracture Post-traumatic seizure Focal neurological deficit More than one episode of vomiting Amnesia for > 30 min of events before impact (The National Institute for Health and Clinical Excellence (NICE) guideline)

7 Rapidity: the greatest advantage of CT CT offers greater accessibility with short image acquisition time, which can be particularly advantageous in agitated patients and those who present with severe trauma or critical illness Image slices that are degraded by motion artefact can easily be repeated FIGURE Bedside CT Imaging data can also be acquired at the bedside within the critical care and theatre environments Patients with poor mobility or unstable condition can benefit from the advantages of CT FIGURE Portable CT Thanks to J. P. Coles and D. K. Menon Dept. of Critical Care Medicine, The Hospital for Sick Children (University of Toronto, Canada)

8 The limitations of CT Delivers high dose of radiation Beam-hardening artefacts can partially obscure the posterior fossa, temporal and frontal regions, and the vertebral canal FIGURE (a); CT finding in a 49-year-old transient ischemic attack (TIA) patient (b); T2-weighted FLAIR MRI finding of the same patient (c); T2-weighted MRI finding of a 49-year-old man with transient nausea and visual loss Forster et al., Eur Neurol (2012) Limited resolution can result in partial volume errors When a region of abnormal tissue is smaller than the resolution of the acquired data Haemorrhage or other evidence of intracranial or spinal pathology may remain undetected particular concern within the brainstem and spinal cord where a small area of pathology can result in devastating injury Diffuse axonal injury after traumatic brain injury are best visualised using MRI

9 The image density of CT Signal intensity in CT reflects the density of the matter. The signal intensity in CT is expressed as the Hounsfield units (HU), and the reference value of HU is set based on the HU of water (0). Blood clot or haemorrhage has HIGH HU (40 ~ 80), and expressed as hyperdense or white area in CT image Normal brain tissue tends to have HU of 20 ~ 40 Tissue under the influence of oedema or ischaemic regions (i.e. increased water content) exhibit LOWER HU than normal tissue (darker pixels in CT)

10 The image density: interpretation of CT Extradural haematoma Bleeding has occurred within the potential epidural space and is usually associated with a fracture. The expanding lesion has resulted in compression of the ipsilateral ventricle but no midline shift. In addition, there is a countercoup with evidence of haemorrhagic contusion within the left fronto-temporal cortex Subdural haematoma Bleeding occurs between the arachnoid and inner meningeal layer of the dura. There is also subdural blood tracking along the tentorium Intracerebral haemorrhage Large left intracerebral haemorrhage with extension into the lateral ventricle secondary to brain contusion. There is compression of the ipsilateral ventricle and midline shift. Thanks to J. P. Coles and D. K. Menon

11 The image density: interpretation of CT Facial Fracture Fracture involving the frontal sinus. These are associated with frontal haemorrhagic contusions and intracranial air. There is also a left occipital subdural haematoma but no midline shift. Subarachnoid Haemorrhage and ventriculomegaly Extensive intraventricular blood within the lateral and third ventricles. The ventricular system is generally enlarged and the brain parenchymal is compressed, with loss of the normal appearance of the brain sulci and gyri. This patient may benefit from placement of an external ventricular drainage in order to remove cerebrospinal fluid and control intracranial pressure. Thanks to J. P. Coles and D. K. Menon

12 Structural Imaging: MRI Imaging modality based on the nuclear phenomena of magnetic resonance MRI data are produced using powerful static magnetic fields, which are measured in units termed Tesla (T), and intermittent oscillating radiofrequency electromagnetic fields that elicit signals from the nuclei of certain atoms 1 T = 10,000 G (Gauss) The magnetic field strength at the surface of the Earth = 0.5 ~ 1.5 G Field strengths used in clinical MRI = 1 ~ 3 T When subjected to a uniform magnetic field, the magnets conform to the field lines established by the magnetic field, resulting in the spatial alignment of the magnets MR Magnet Hizmetleri, Elips Tibbi Sistemler

13 MRI: Basic Principles Jeffery West, How MRI works

14 Advantages of MRI Provide high spatial resolution (the ability to distinguish two separate structures at a small distance from each other) and contrast resolution (the ability to distinguish the differences between two similar but not identical tissues) MRI is more sensitive at detecting white-matter abnormalities than CT

15 Disadvantages of MRI Relatively long image acquisition time Requiring patients to be lying still during the examination, which can be particularly challenging in paediatric patients Projectile risks from ferromagnetic objects Ferromagnetic objects (e.g. oxygen cylinders, identification badges, paging devices) can become dangerous projectiles Implanted devices Being disastrous if the ferromagnetic implant (e.g. cardiac pacemaker) is large or in a critical location Even non-ferromagnetic implants can result in significant image distortion or cause local burns Monitoring devices Monitoring devices may dysfunction due to magnetic fields Leads from such devices may result in burns ECG distortion: radiofrequency currents produce ECG artifacts FIGURE Projectile (missile) effect of MRI

16 MRI pulse sequences (A) T1-weighted (B) T2-weighted (C) Fluid-attenuated inversion recovery (FLAIR) (D) Gradient echo sequence By employing a variety of different MR sequences, the extent of injury can be demonstrated with high resolution On a T1-weighted images, fat appear bright while waterand fluid-containingtissues appears dark On a T2-weighted scan, water and fluid are bright while fat is dark A fluid attenuation inversion recovery (FLAIR) sequence generate images in which areas of tissue T2 prolongation are bright, while the normal CSF signal is nulled and appears dark This allows the detection of periventricular and superficial cortical lesions Gradient echo MRI is sensitive to changes in magnetic susceptibility, which results in lesions of low intensity following haemorrhage within the tissue Thanks to J. P. Coles and D. K. Menon

17 MRI: Spinal cord The spinal cord is best visualized using MRI as it provides better resolution, particularly within the confined environment of the spinal canal where beam-hardening effects, limited resolution and poor soft tissue contrast can limit the usefulness of CT MRI show better contrast for the tissue within the spinal canal, intravertebral discs, dura and spinal ligaments FIGURE Comparison of CT and MRI of the cervical spine Thanks to J. P. Coles and D. K. Menon

18 Structural Imaging: Angiography Digital subtraction angiography (DSA) is used to delineate the adequacy of blood flow through the cerebral vessels and the subsequent venous drainage Requiring cannulation of a large arterial vessel and the passage of a catheter through the vascular system within the brain Images are acquired following injection of contrast within the intracranial segments of the internal carotid and vertebral arteries on each side of the brain Image processing allows the non-vascular structures to be subtracted from the final images Can be used to diagnose disorders of the brain vasculature such as cerebral aneurysm, arteriovenous malformations, arterial and venous thrombosis, and arterial dissection FIGURE Digital subtraction angiography. The CT image (upper panel) demonstrates a large intracerebral haematoma extending into the lateral ventricle Thanks to J. P. Coles and D. K. Menon

19 Angiography: CTA and MRA CTA / MRA : A group of techniques to image blood vessels derived from CT and MRI, respectively Less invasive, more rapid alternatives to DSA Do not require arterial cannulation but rely on the intravenous administration of contrast agent followed by sequential imaging CTA and MRA generates images of the arteries in order to evaluate them for stenosis, occlusion or aneurysms Trauma to the brain and spine can lead to damage to the cerebral vasculature and result in cerebral ischaemia and infarction early assessment of cerebral ischaemia using angiography is essential, as prompt repair of treatable causes may prevent infarction and poor outcome Thanks to J. P. Coles and D. K. Menon

20 Physiological Imaging Several imaging techniques are available that can measure aspects of brain physiology, including cerebral blood flow (CBF) and metabolism Measurement of cerebral perfusion: CT perfusion, Xenonenhanced CT, SPECT Assessment of both perfusion and metabolism: PET, MRI, MRS Although such techniques provide snap shots of physiology, they can be used to select patients for curative procedure, such as thrombolysis In addition, such data can be repeated and used to assess the impact of therapeutic interventions These imaging modalities are helpful in defining evidence of tissue injury, cerebral ischaemia and the penumbra, and predicting outcome FIGURE Schematic demonstrating the ischaemic penumbra: ischaemic core of infarcted tissue, penumbral region of ischaemic brain tissue at high risk of cerebral infarction and the surrounding region of oligaemia above the threshold for cerebral injury following an acute vascular occlusion Thanks to J. P. Coles and D. K. Menon

21 Physiological Imaging: CT perfusion & Xenon-enhanced CT CT perfusion involves the intravenous administration of iodinated contrast material so that enables to provide parametric images of cerebral blood volume (CBV), mean transit time (MTT), cerebral blood flow (CBF) and CTA alongside structural data Widely accessible, cost-effective, rapid and accurate May not be sufficient to accurately define the volume of brain at risk of ischaemic injury Xenon-enhanced CT uses stable non-radioactive 131 Xe and calculates the degree of increase in the tissue 131 Xe concentration, which is proportional to the blood flow Rapid access to both structural and quantitative CBF data, can be repeated within a short period of time Quantitative CBF studies can be difficult to perform in patients with associated pulmonary pathology FIGURE Assessment of cerebral blood flow (CBF) using CT perfusion Thanks to J. P. Coles and D. K. Menon

22 Physiological Imaging: SPECT Single-photon emission CT (SPECT) uses conventional gamma-emitting nuclear medicine isotopes with multiple detectors to investigate blood flow within the brain Relatively simple, inexpensive, can be used to assess cerebral perfusion Relatively low resolution, and generally non-quantitative Regions of the brain with a reduction of tracer signal compared with the contralateral hemisphere of >70% are suggestive of infarction, while a region of 40-70% suggests ischaemia FIGURE (A) 99 Tc-HMPAO SPECT and (B) T2- weighted MRI slices at ganglia level of patient with ischaemic lesion in left thalamus (yellow arrowheads) Catafau AM. Brain SPECT in Clinical Practice. Part 1: Perfusion* (2001)

23 Physiological Imaging: Positron emission tomography (PET) Positron Emission Tomography measures the accumulation of positron-emitting radioisotopes within the brain successfully investigate in physiology following head injury assess changes in physiology with commonly applied therapeutic manoeuvres, such as hyperventilation and CPP augmentation Although PET is clearly capable of defining many complex aspects of cerebral physiology and pathophysiology, it is a research tool that is relatively expensive and not universally available Thanks to J. P. Coles and D. K. Menon

24 Physiological Imaging: Magnetic resonance techniques Magnetic resonance has become an extremely useful clinical tool in patients with neurological disease Magnetic resonance combines: the ability to image perfusion (Perfusion MRI) the status of tissue (DWI and MRS) vascular patency (MRA) white-matter tracts (DTI) This thorough assessment of the derangements induced by a variety of disease mechanisms can be used to determine diagnosis, the likely response to therapeutic intervention and the degree of eventual functional recovery

25 Magnetic resonance technique: Perfusion MRI, DWI Perfusion MRI uses rapid sequential susceptibility-weighted imaging after injection of a bolus of MRI contrast medium that induces a change in intravascular magnetic susceptibility to produce images of MTT, and relative CBF and CBV Diffusion-weighted MRI (DWI) images the microscopic movement of water Early hyperintensity on DWI images occurs following acute ischaemia and is associated with the movement of water into the intracellular compartment where it is relatively restricted (cytotoxic oedema) In comparison, brain regions with vasogenic oedema and an increase in extracellular water content demonstrate an increased diffusion and reduced signal on DWI images FIGURE MR perfusion in ischaemic stroke Kane et al., Stroke (2007) FIGURE DWI obtained following acute severe head injury. The bright areas of increased diffusion are consistent with vasogenic oedema (arrows). Thanks to J. P. Coles and D. K. Menon

26 Magnetic resonance technique: DTI Due to the structure of white-matter fibre tracts, water diffusion will appear less restricted along fibre tracts compared with perpendicular to the fibre tract The directionality of diffusion (anisotropy) is measured by diffusion tensor imaging (DTI) Useful in delineating the extent of brain injury following both stroke and head injury Evidence suggests that disruption of white-matter tracts has important implications for cognitive recovery FIGURE Diffusion tensor image following traumatic brain injury Traumatic brain injury, University of Southern California

27 Magnetic resonance technique: fmri Functional MRI (fmri) can be used to measure neural activity by the measurement of changes in blood oxygenation using the blood oxygen leveldependent (BOLD) signal Neural activation results in an increase in regional blood flow and influx of oxygenated blood Used in the assessment of patients recovering from brain injury, patient lesions can be mapped to functional deficits, and patients who appear to be in a vegetative state following brain injury However, the BOLD signal is an indirect measurement of neural activity, and disease processes may alter the relationship between local blood flow and neural activity Therefore, fmri data can be difficult to interpret in disease states FIGURE Communication scans obtained from patient (A, C) and a healthy control subject (B, D) during functional MRI. Monti et al. N Engl J Med (2010)

28 Section 2: MULTIMODALITY MONITORING Part 2-1: Neuromonitoring Modalities Stocchetti, N. & Longhi, L. Multimodality monitoring. In: Matta, B. F., Menon, D. K., & Smith, M. (Eds.). Core topics in neuroanaesthesia and neurointensive care. Cambridge University Press (2011)

29 Multimodal monitoring: Definition and Purpose Monitoring for patients with traumatic brain injury (TBI) can be crucial 1/3 of patients with TBI show clinical deterioration which is dangerous, sometimes life-threatening, and associated with worse long-term outcomes In deeply sedated patients, instrumental monitoring can become the predominant source of information Definition of Multimodality monitoring System where several source of information are put together, analysed and processed to achieve a comprehensive picture of the patient s status The concept is not new, and has been used in intensive care units (ICUs) for more than 30 years

30 Multimodal monitoring: Definition and Purpose The purpose of multimodality monitoring To continuously measure relevant biological variable To verify the effects of treatment To identify trends in the clinical evolution of disease To contribute to the assessment of prognosis Dept. of Neurosurgery, Addenbrooke s Hospital (University of Cambridge, UK) and Dept. of Critical Care Medicine, The Hospital for Sick Children (University of Toronto, Canada)

31 Multimodal monitoring: Source of Information Cerebral Global monitors Intracranial pressure (ICP) Cerebral perfusion pressure (CPP) Jugular venous oxygen saturation Electrical monitoring Brain temperature Monitors of Cerebral blood flow Transcranial Doppler Ultrasonography (TCD) Laser Doppler flowmetry and thermal diffusion flowmetry Monitors of the adequacy of cerebral oxygen delivery Brain tissue oxygen tension Cerebral microdialysis

32 Cerebral global monitors: ICP Intracranial pressure is defined as the pressure required in a needle placed in the cerebrospinal space to prevent the escape of Cerebrospinal Fluid(CSF) ICP = CSF pressure ICP higher than 20 mmhg can cause severe neurological damage Normal range = 5 ~ 15 mmhg (in horizontal position) Too low ICP = Intracranial hypotension Too high ICP = Intracranial hypertension If ICP is uncontrollably high, remove part of the skull ( Decompressive craniectomy ) In modern neurointensive care unit, ICP should be monitored in all salvageable comatose patients with an abnormal CT scan ICP Probes: Silverline Ventricular Probe, Spiegelberg

33 Cerebral global monitors: CPP Cerebral Perfusion Pressure (CPP) represents the driving force for Cerebral Blood Flow (CBF) Pressure autoregulation ensures a constant CBF within a CPP range from mmhg Outside this limits, CBF is passively dependent on CPP Following TBI, up to 30% of patients show defective autoregulation CPP=MAP-ICP Normal range of CPP = 50 ~ 70 mmhg (the recent Guidelines for the Management of Severe Traumatic Brain Injury) It is important to identify clinical priorities in individual patients and to balance the physiological requirements of the brain with the potential harm of aggressive therapy FIGURE Cerebral autoregulatory reserve Roytowski and Figaji, Continuing Medical Education (2014)

34 Practical example: Intracranial hypertension ICP MAP CPP PbrO 2 T brain FIGURE Chart showing the changes in ICP, CPP, brain tissue oxygen tension (PbrO 2 ) and brain temperature (measured in the vicinity of a hypodense lesion) during barbiturate induction for the treatment of raised ICP Thanks to N. Stocchetti and L. Longhi

35 Practical example : Refractory Intracranial hypertension FIGURE Refractory intracranial hypertension. The second half of this graph shows ICP increasing above 60 mmhg while CPP falls well below 40 mmhg. The patient died. During the progressive ICP elevation, PRx increases Thanks to C. Zweifel, P. Hutchinson and M. Czosnyka

36 Practical example : Plateau waves FIGURE Stable ICP disturbed by a single plateau wave, which is associated with a decrease in CPP and an increase in cerebrovascular pressure reactivity index (PRx), with the latter continuously monitoried as a variable changing in time Thanks to C. Zweifel, P. Hutchinson and M. Czosnyka

37 Cerebral global monitors: Jugular venous oxygen saturation The global adequacy of cerebral DO 2 can be assessed by measuring jugular bulb oxygen saturation (SjO 2 ) and calculating arterio-jugular oxygen difference (AjDO 2 ). The AjDO 2 represents the balance between cerebral metabolic rate of oxygen (CMRO 2 ), and CBF AjDO 2 = [(SaO 2 SjO 2 ) Hb 1.34] + [(PaO 2 PjO 2 mmhg) 0.003] Monitoring of SjO 2 should be used to guide hyperventilation therapy, which is commonly used to reduce ICP by producing Hypocapnic vasoconstriction Normal range of SjO 2 = 55 ~ 70 % Values of SjO 2 below 50% represent global ischemia Don t cannulate the internal jugular vein on the side of an arteriovenous malformation or decompressive craniectomy Data are unreliable because of shunt effect FIGURE The technique for inserting jugular bulb catheter Thanks to A. Ercole and A. K. Gupta

38 Cerebral global monitors: Electrical monitoring The brain normally produce low voltage electrical activity The electrical activity can be measured by Electroencephalogram (EEG) Ordinarily recorded from the scalp with small surface electrodes Interpretation of EEG information requires special expertise, because several ICU-related artefacts originating from infusions pumps, mechanical ventilators and heating blankets may produce appearances that suggest seizure activity Somatosensory evoked Potential (SSEP) is most frequently used in neurointensive care Swasthya Health Care & Diagnostic Centre, India and Dept. of Neurology, Georgetown University, Washington DC

39 Cerebral global monitors: Brain temperature Hypothermia / Hyperthermia Hypothermia has been shown to be neuroprotective in several models of acute brain injury and has been recommended for post-cardiac arrest care by several guidelines Hypothermia is effective in controlling intracranial hypertension

40 Monitors of cerebral blood flow: TCD TCD (Transcranial Doppler Ultrasonography) Non-invasive tool to evaluate the large intracrainal arteries at the bedside Can provide information on arterial patency, ICP, pressure autoregulation and vasoreactivity Supporting the clinical diagnosis of brain death Major applications monitoring of vasospasm in patients following subarachnoid haemorrhage, particularly in the basal segments of the intracranial arteries, such as middle cerebral artery (MCA) FIGURE Colour images of the middle cerebral artery in red with corresponding velocity waveforms from left (A) and right (B) sides obtained with imaging transcranial Doppler ultrasonography from an 11-year-old boy with sickle cell amenia Krejza, et al., Stroke (2011)

41 Monitors of cerebral blood flow: TCD FIGURE Trace of flow velocity obtained from (a) internal carotid artery bifurcation at cm, (b) the M1 segment of the middle cerebral artery at 3 6 cm, (c) the posterior cerebral artery (P1) at 6 8 cm, (d) the anterior cerebral artery (A1) at 6 8 cm Thanks to A. Prakash and B. F. Matta /new-facility-for-stroke-and-fast-detection

42 Monitors of cerebral blood flow: LDF & TDF Laser Doppler flowmetry (LDF) provides qualitative CBF information on a small volume of tissue and allows rapid detection of regional perfusion changes Limitations: can be influenced by haemodilution and various artefacts (patient movement, displacement), high invasiveness Thermal diffusion flowmetry (TDF) provides real-time, quantitative regional CBF values that have been validated when compared with those obtained using a xenon-enhanced CT scan FIGURE The principle of laser Doppler flowmetry FIGURE The theory behind laser Doppler flowmetry for the measurement of CBF. Doppler frequency and power depend on the speed of red blood cells. Bandwidth broadens as red blood cells speed increases, but amplitude and shape remain constant. Thanks to A. Prakash and B. F. Matta

43 Monitors of the adequacy of cerebral oxygen delivery: Brain tissue oxygen tension Regional cerebral oxygenation can be measured continuously using a probe containing a miniaturized Clark-type electrode placed in the brain parenchyma The brain oxygen tension (PbrO2) represents a balance between cerebral oxygen difference and its consumption, and thus is influenced by PaO2 and CBF Regional brain hypoxia occurs following severe TBI, both in pericontusional tissue and in normal-appearing tissue, even when CPP and SjO2 are normal FIGURE Brain tissue oxygen monitoring system, LICOX, INTEGRA

44 Monitors of cerebral blood flow and oxygen delivery: Practical considerations The location of probes is a key issue for appropriate interpretation of these monitoring tools and for integrating their data with clinical status and other monitoring modalities Probes should be sited in vulnerable and potentially salvageable tissue such as the pericontusional tissue (NEVER the core of the contusion) and tissue underlying a subdural haematoma Eloquent locations should be avoided When structurally normal tissue is monitored, probes should be placed in the subcortical white matter of the more injured hemisphere While the literature reports a very low rate of complications (haemorrhage/infections) with these probes, several caveats need to be considered Invasiveness of probe means that insertion should be avoided in the presence of haemostatic abnormalities Data obtained are from small volumes of tissue, which may sometimes be unrepresentative of the wider brain

45 Integration of multimodality monitoring data: Potential and Pitfalls Multimodality monitoring integrates multiple sources of information in a number of possible combinations Combinations reflect local expertise, equipment availability and the clinical interest of a specific research group Usually, ICP and CPP are incorporated as core data An essential component of multimodality monitoring is the description of events, artefacts and human interventions (e.g., physical and pharmacological treatments) Without comments, notes and remarks, a meaningful interpretation of a stream of thousands of data points per day is both cumbersome and unrewarding ICP MAP CPP The previous figure also shows the event log! Thanks to N. Stocchetti and L. Longhi

46 Concordant versus discordant data: Clinical interpretation When multiple parameters are acquired simultaneously, the meaning of every single measure may change in relation to other data The preliminary requirement is that all data are reliable and artefacts or errors have been excluded Once only meaningful data have been filtered, the interplay among variables becomes challenging Concordant data: consistent changes in multiple monitored variables when different monitoring techniques explore the same anatomical areas/physiological events Discordant data: a single parameter in a multimodality monitoring dataset provides conflicting information Discordant data may imply complex pathophysiology, rather than technical problems The interpretation of concordant versus discordant data underlines a fundamental component of multimodality monitoring, which is clinical interpretation The transformation of a mass of data into useful information, and the use of this information for the benefit of patients, demands a substantial exercise of human effort

47 Computer-aided multimodal monitoring In every ICU, enormous quantities of data (depending on the number of monitoring modalities employed and the rate of data acquisition) can be captured from each patients These consideration suggest an obvious role for computers in managing, integrating, analysing and displaying such data A pre-requisite for the bedside data management system is that the data should be filtered Every time a patient is moved to a CT scan and the lines are disconnected or every time the ventricular catheter is opened for CSF withdrawal, artefactual data can be recorded Computer can be used not only for data recording and analysis but also for discovering new relationships among the data itself CBFv ICP ScO 2 The integrated view of physiology that computers derive from multimodal monitoring can provide important indicators for clinical management and decision making ABP Multimodal monitoring aided by computer program ICM+ Dept. of Neurosurgery, Addenbrooke s Hospital (University of Cambridge, UK)

48 Cost-benefit analysis of multimodal monitoring The total cost of any system is likely to be high because of the initial investment and the human work implied in maintaining and implementing it In fact, technology is advancing, new toys are on the horizon and a conclusive statement about the utility of multimodality monitoring may be premature However, even as things stand, multimodality monitoring has improved our detection and interpretation of pathophysiology at the bed side, and is increasingly seen as a basis for selecting and implementing therapies

49 Section 3: BRAIN ENGINEERING

50 Brain engineering Objectives Fundamental understanding of the brain: its mechanisms, operation, and behaviours Interfacing the brain and other devices, such as computers Engineering of the brain: clinical neuro-modelling, neuromorphic systems, robotics, etc. Areas: artificial intelligence (AI), brain-computer interface (BCI), brain image processing, cognitive robot, computer vision, neuro-modelling, neuromorphics, neuron-on-a-chip, optogenetics, virtual reality, pattern recognition, etc.

51 Hierarchy and reverse hierarchy FIGURE 1. Schematic diagram of classical hierarchy and reverse hierarchy theory showing the visual system. Neurons of low level areas (V1, V2) receive visual input and their output integrated and processed by successive cortical levels (V2, V3, MT). Finally, further levels (IT, PF, etc.) represent abstract forms, objects, and categories. Hasson et al. (2004) Hochstein and Ahissar, Neuron (2002)

52 Neural decoding of visual imagery during sleep: Reading dream A neural decoding approach in which machine-learning models predict the contents of visual imagery during the sleep-onset period Given measured brain activity, discovering links between human fmri patterns and verbal reports with the assistance of lexical and image databases Specific visual experience during sleep can be represented by brain activity patterns Horikawa et al., Science (2013)

53 Neuromorphic system Electronic systems that perform perception, cognitive and control functions by mimicking biological neural networks in the brain Aims: Working like the BRAIN! To find semantic information and make decision from highly complicated input data Building knowledge database by learning Improve performance by practice Low power / high effectiveness Neuronal networks, electronic nose, silicon retina, cochlear implants, intelligent robotics, etc. Neurochip2, Zanos (2009)

54 Neuromorphic system: BigDog Boston Dynamics with Foster-Miller, NASA Jet Propulsion Lab, Havard University Concord Field Station (2005)

55 Neuro-prosthetics Neural prostheses are devices that can substitute a motor, sensory or cognitive modality which might be damaged following an injury or a disease Otto Bock HealthCare Products, Austria Wagner et al. (2012)

56 Brain-Computer Interface (BCI) Neuro-feedback Wheelchair Mobile phone Brain-Computer Interface Game Driving Home-Automation

57 BCI: Thought-controlled wheelchair (Korea University, MinLab)

58 Brain-to-Brain Interface: Neuromodulation BK Min, K-R Muller, Trends in Biotechnology (2014)

59 Brain-to-Brain Interface: Mind Control Mind control machine Human wags rat s tail using brain-to-brain interface (Harvard Medical School, Yoo et al.)

60 Take home messages Engineers solve real world problems: neurological disorders are not exceptions Neuroimaging is a fundamental key to define the cause and extent of neurological injury, manage and predict clinical outcome; and advances in neuroimaging techniques may allow to guide therapies for such neuronal injury and improve functional outcome for patients The parameters derived from multimodal neuro-monitoring and advanced signal analysis enables better assessment on the neuropathological conditions of patients Further brain engineering, on the field of computational neuroscience, clinical neurology, electrical engineering, and signal processing,has rapidly growing benefits and applications