Neuroimaging in Mental Health: An Introduction PDF

Neuroimaging in mental health: an introduction James Bisby, Kate Merritt & Elvira Bramon UCL Division of Psychiatry  LEARNING OBJECTIVES Basic understanding of IMAGING METHODS commonly used in mental health. Understand their strengths and limitations. Exam...

Neuroimaging in mental health: an introduction James Bisby, Kate Merritt & Elvira Bramon UCL Division of Psychiatry  LEARNING OBJECTIVES Basic understanding of IMAGING METHODS commonly used in mental health. Understand their strengths and limitations. Examples of imaging findings in mental health RESEARCH Examples of CLINICAL APPLICATIONS of imaging in mental health Why is neuroimaging important in mental health? Why is imaging important in mental health? Brain pathology cannot easily be studied directly during life. Brain biopsy not routinely performed. Imaging can be used as a surrogate/biomarker of brain function/pathology “in vivo”.  NEUROIMAGING METHODS STRUCTURAL – Computed tomography (CT) – Magnetic Resonance Imaging (MRI) FUNCTIONAL – Positron emission tomography (PET) – Single photon emission computed tomography (SPECT) – Diffusion tensor imaging (DTI) – Functional MRI (fMRI) – Magnetic Resonance Spectroscopy (MRS) – Magnetoencephalography (MEG) – Electroencephalography (EEG) Magnetic Resonance Imaging Structural (sMRI) & Functional (fMRI) Structural MRI scan (sMRI) application in Alzheimer’s Disease What is different between participants A, B and C? A B C Example: sMRI applied to Alzheimer’s disease generalised (grey matter) atrophy on MRI A B C Amnestic mild Alzheimer’s Health control cognitive Disease impairment  Structural MRI APPLICATIONS Meningioma Screen for reversible Subdural haematoma causes of altered mental Normal pressure hydrocephalus state Screen for severe/ Deep tumours irreversible pathology Infarcts White matter hyper intensity Atrophy: present / absent, global / localised. Supporting diagnosis Rule out organic pathology in new cases of psychosis. Extensively used as a research tool in RESEARCH mental health Diffusion tensor imaging (DTI) scans MRI imaging method DTI looks at white- matter connectivity within the brain.  The BOLD Blood Oxygen Level Dependent effect in fMRI fMRI relies on the BOLD effect as a proxy measure of brain activity (developed by Ogawa in the 1990’). Blood releases oxygen to active neurons at a greater rate than to inactive neurons (this is known at the “hemodynamic response”). This causes a difference in the magnetic properties of oxygenated and deoxygenated blood, which can be detected by a MRI scanner.  Neurophysiology (Electroencephalograms) EEG smri  Hans Berger Berger’s early EEG recording by 1928 German physiologist and psychiatrist Hans Berger (1873–1941) began his studies of the human EEG in Jena. He gave the device its name and is credited with inventing the EEG, though others had performed similar experiments. In 1929 Berger announced to the world that it was possible to record the feeble electric currents generated on the brain, without opening the skull, and to depict them graphically onto a strip of paper and that this activity changed according to the functional status of the brain, such as in sleep, anaesthesia, hypoxia and in certain nervous diseases, such as in epilepsy.  Applications of EEG Main clinical applications in neurology/neurosurgery: Epilepsy where EEG is essential for its diagnosis/classification Diagnosis of coma, encephalopathy and brain death Neurophysiology guiding surgery (to identify language areas prior to surgery) In mental health it can support diagnosis To rule out epilepsy in unusual presentations (e.g. in post-ictal psychosis). Extensively used as a clinical research tool in mental health PET & SPECT imaging  PET Positron Emission Tomography PET measures emissions from radioactively labelled metabolically active chemicals that have been injected into the bloodstream  Applications of PET imaging PET is routinely used clinically in oncology: Tumour detection, studies of extension, monitoring response to treatment. PET has clinical use in mental health: Licensed for amyloid imaging in dementia. Not frequently used due to high cost and limited access to PET scanners. PET is used for mental health research: Research in neurodegeneration Extensive research on neurotransmission in mental illness (schizophrenia, OCD, mood disorders, addiction…)  SPECT APPLICATIONS Clinically used in neurology for epilepsy, stroke, brain tumours, traumatic brain injury… In mental health for evaluating patients with suspected dementia including early detection, differential diagnosis, and in the pre-dementia phase (Amen et al, 2011). SPECT is widely used in research in mental health, especially to investigate receptor binding and neurotransmitter function. Summary: How do different techniques compare? EEG sMRI & fMRI SPECT PET Safest Not-invasive Invasive Invasive Is it Recording naturally- invasive? Magnet, noisy, Radioactive tracer + Radioactive tracer + occurring electrical enclosed space IV injection IV injection signal Poor Temporal Superb Good Good resolution BOLD signal slow, milliseconds couple of seconds couple of seconds 5-10 seconds Spatial Poor High millimetres Good High resolution Cost Low Medium Medium High Applications Research +++ fMRI Research +++ Research ++ and Research ++ in mental clinical use ++ Occasional clinical sMRI routine clinical Rare use in health use use +++ dementia