Magnetic Resonance Imaging brain dr waleed aboulsoud .pptx

education about how to read normal MRI Brain

1. B rain Magnetic Resonance Imaging (Brain MRI ) Dr. Waleed Aboul-Elsoud Pediatric Consultant

2. Introduction What is MRI ? Magnetic resonance imaging (MRI) is Medical imaging technique used to examine the structure and function of the nervous tissue and soft tissues . MRI is based on Emission of radio-waves and magnetic fields to produce images based on the tissue’s proton (hydrogen) levels. In 1977 the first MRI exam was performed on a human being. It took 5 hours to produce one image

3. MR Scanner

4. Introduction How Does it Work ? It works by exciting the tissue hydrogen protons, which in turn emit electromagnetic signals back to the MRI machine. The MRI machine detects their intensity and translates it into a gray -scale MRI image . Thus, for describing the MRI appearance of the parts of the brain we use the terms  hyperintense  and  hypointense , with the gray matter being the reference point. This means that everything that is brighter than the grey matter is hyperintense , while everything that is darker is hypointense . 

5. Introduction Why MRI ? Utilizes non ionizing radiation. (unlike x-rays). Ability to image in any plane. (unlike CT scans). Very low incidents of side effects. Ability to diagnose, visualize, and evaluate various illnesses. MRI is used to analyze the anatomy of the brain and to identify some pathological conditions such as cerebrovascular incidents, demyelinating and neurodegenerative diseases . the MRI can be used for examining the activity of the brain under specific activities (functional MRI - fMRI).  However, it takes longer to be produced than CT for example, which is why it’s not a primary imaging choice for urgent conditions.

6. Risks Metal items in or on the body Because the MRI machine uses a large, powerful magnet, people with metal on or in their bodies may need extra care. Items that may have metal include: Pacemakers & Implantable heart defibrillators . Stents . Pins or screws. Surgical staples. Stimulation devices, such as deep brain stimulators. Hearing aids or implants in the ear. Clips or coils to treat an aneurysm. Continuous glucose monitoring systems. Devices implanted in the body to deliver medicines, such as insulin. Devices used to expand tissues. Body piercings, permanent eyeliner or other permanent cosmetics. Prosthetic joints.

7. Danger : Flying Objects

8. CT v MRI ( brain) CT is a map of tissue density (white areas represent higher density tissues than blacker areas). MRI is a map of proton energy in tissues of the body ( white areas represent high ‘signal ’) Cerebrospinal fluid (CSF) is low density on CT ( hypodense ) On this MRI image the CSF is white (indicating high signal) CT scans performed with a 15- to 20-degree angulation at 8-mm increments. MRI scans are parallel to the line in the axial plane, with 6-mm slice thickness. 

9. The Components A magnet which produces a very powerful uniform magnetic field . ( The most important component), MRI magnetic field strength is measured in  teslas (T) , with  common clinical strengths being 1.5T and 3T, and higher-field research scanners reaching 7T or more . A higher tesla rating indicates a stronger magnet, which generates more detailed images, particularly for soft tissues and subtle abnormalities Gradient Magnets which are much lower in strength ( Earth magnetic field) . Equipment to transmit radio frequency (RF). A very powerful computer system, which translates the signals transmitted by the coils.

10. Brain MRI Sequences A brain MRI is one of the most commonly performed techniques of medical imaging. Common brain MRI sequencing types include : T1-weighted  (for anatomical detail) T2-weighted  (for showing pathology like edema ) FLAIR  (T2-weighted that suppresses fluid) Diffusion-Weighted Imaging (DWI)  (to detect acute stroke) Susceptibility-weighted imaging (SWI)  (to see blood products) Perfusion-weighted imaging (PWI)  (to assess blood flow),   T1-weighted with contrast  (using  gadolinium  to highlight blood-brain barrier integrity ).

11. The T1w  sequence : best shows the structures with a high amount of fat . Excellent for showing normal brain anatomy and structure because fat is bright and water is dark, gray matter as gray , white matter as white, the bones as black, and the adipose tissue as white. The  T2w sequence : best shows the structures with a high amount of water. the CSF is white, gray matter is white , white matter is darker gray , the bones are black and the adipose tissue is white.

12. The FLAIR (Fluid-Attenuated Inversion Recovery) is a specialized magnetic resonance imaging sequence that  suppresses signals from normal cerebrospinal fluid (CSF)  to improve the visibility of brain abnormalities. FLAIR Helps identify pathologies. shows areas next to CSF (periventricular) very well. Also good for juxtacortical areas . This technique makes it easier to detect lesions such as those caused by  stroke, tumors , or  multiple sclerosis , as these conditions often appear as bright spots or hyperintensities against the dark fluid background

13. Diffusion weighted imaging Diffusion-weighted imaging (DWI) is an MRI technique that detects brain abnormalities by tracking the random movement of water molecules, providing high sensitivity for acute ischemic stroke and other neurological conditions like tumors , infections, and traumatic brain injury. By measuring the magnitude and direction of water diffusion, DWI creates detailed images that differentiate pathologies such as abscesses from tumors , and help guide treatment for various central nervous system disorders.  Apparent diffusion coefficient, ADC: A quantitative map called an ADC map displays the spatial distribution of water diffusion rates, providing even more information about tissue changes.   Restricted diffusion= high signal on DWI & low signal on ADC

14. Benefits of DWI High Sensitivity:  DWI is extremely sensitive to subtle microstructural changes in brain tissue . Rapid Diagnosis:  It provides crucial information quickly, making it an essential tool in diagnosing acute neurological events . Therapeutic Guidance:  DWI findings can help differentiate between true tumor progression and treatment-related changes, aiding in treatment planning and response evaluation . No Contrast Needed:  DWI is a non-contrast technique, reducing the need for contrast agents in many acute situations.

15. Images of DWI and ADC

16. SWI sequence: Sensitive to substances like  degraded blood products (hemosiderin) , so Detects hemorrhage well . Low intensity (called susceptibility artifact). SWI

17. T1-weighted with contrast   with   gadolinium :  Uses an intravenous contrast agent (gadolinium) to highlight areas where the blood brain barrier  is compromised, often revealing tumors , infections, or inflammation. 

18. Enhancement Enhancement on a brain MRI means areas of tissue in the brain appear brighter on the scan because they have absorbed a contrast agent, usually  gadolinium , which highlights abnormalities like tumors , inflammation, or infections. Under normal conditions the blood brain barrier stop the contrast from entering the brain but if it damaged in certain conditions , The contrast agent travels through the blood stream and collects in specific tissues, increasing signal intensity and making it easier to see and diagnose conditions that would otherwise be missed on a non-contrast MRI.  Enhancement may be seen in : Tumors Infections Inflammatory conditions such as active demyelinating lesions Subacute areas of ischemia

19. Short tau inversion recovery (STIR) STIR is based on a T2 image, but the image is manipulated in a way that results in fat (and any other materials with similar signals) being nullified. Unlike fat-suppressed images. fat can make the interpretation of oedematous areas and bone marrow difficult. 

20. How to read brain MRI Basic Principles Check Image & Patient Details:  Always start by verifying patient and image details, and compare the new MRI to previous ones if available . Understand Image Sequences:   Different sequences (e.g., T1, T2, FLAIR) highlight different tissues and pathologies. T1 sequences show normal anatomy well, while T2 and FLAIR are excellent for detecting pathological changes like inflammation or ischemia Compare Image Types:  Specifically, compare fat-sensitive images (like T1) with water-sensitive images (like T2 or FLAIR) to differentiate various pathologies .

21. 4. Look for Signal Intensity: Gray Matter:  The outer layer of the brain, appearing as a specific reference point for brightness. White Matter:  Appears lighter on T1 and darker on T2 sequences. Hyperintense / Hypointense :  " Hyperintense " means brighter than the reference ( gray matter), and " hypointense " means darker. 5. Examine Key Brain Structures: Cerebral Cortex:  The brain's outer layer where thinking occurs. Ventricles:  Fluid-filled spaces that cushion the brain and remove waste; they should appear symmetrical and appropriately sized. Bone:  Is the dimmest structure on the scan and appears hypointense .

22. 6. Note Abnormal Findings: Lesions :  Irregular light or dark areas that might indicate abnormalities like inflammation, ischemia, or tumors . Enhancement: After contrast, abnormal areas may appear brighter, indicating pathological or vascular tissue . 7. Systematic Approach:  A common method is to start from one area of the brain, move through the anatomy to make sure nothing is missed, and compare findings with the other side of the brain. 8. Clinical Correlation:  Relate your findings back to the clinical question or symptoms the patient presented with.

23. Axial images

24. sagittal T1 Weighted Section at the level of Foramen Magnum Below the fourth ventricle : In this section, most of the structures in the anterior and middle fossa & components of the base of the skull and the orbits. In the middle fossa the foramen ovale and foramen spinosum can be visualized 

25. Fourth ventricular level : The lower pons is seen in front of the fourth ventricle, connecting to the cerebellar hemispheres by the middle cerebellar peduncles. The pons is outlined by CSF, with the anterior and lateral pontine cisterns. Anterior to the pons appears the basilar artery   sagittal T1 Section at the level of medulla

26. sagittal T1Section at the level of Pons Above the fourth ventricle At the center , the midbrain appears outlined by the suprasellar cistern, ambient cistern, and quadrigeminal cistern. The suprasellar cistern contains the internal carotid artery, the anterior and middle cerebral arteries, the optic chiasm, the infundibulum, the mammillary bodies,  Lateral to the midbrain are the temporal lobes.

27. sagittal T1 Section at the level of horns of lateral Ventricle Third ventricular level The frontal lobes can be seen separated by the interhemispheric fissure medial to them. Superficially the sylvian fissures extend medially to separate the frontal lobe from the temporal lobe. Medial to the medial surface of the sylvian fissure, the insular cortex, external capsule, putamen, and globus pallidus can be demonstrated.

28. sagittal T1 Section at the level basal ganglia Horns of Lateral ventricular level The most superior aspects of the frontal lobes are visualized. The superior portion of the frontal horns appears outlined by the head of the caudate nuclei laterally. Anteriorly the frontal horns are shaped by indentation of the genu of the corpus callosum. 

29. sagittal T1 Section at the level of corpus callosum Body of lateral ventricular level The superior extension of the sylvian fissure and the superior temporal gyrus are seen. The central sulcus separates the temporal lobe from the parietal lobe. The most superior aspect of the frontal horns is indented laterally by the most superior aspect of the caudate nuclei. 

30. sagittal T1 Section at the level of Body of Corpus Callosum Above the lateral ventricular level This section mainly includes the frontal lobe, parietal lobe, and a small portion of the occipital lobe. The superior frontal sulcus, separating the superior frontal gyrus from the middle frontal gyrus, 

31. Above the ventricular level This section mainly includes the frontal lobe, parietal lobe, and a small portion of the occipital lobe sagittal T1 Section above the Corpus Callosum

32. Sagittal images A sagittal MRI of the brain  provides a side-view of the brain, allowing for a clear assessment of midline structures like the corpus callosum and brainstem, pituitary gland . It is a useful view for diagnosing a variety of conditions, including congenital malformations, tumors , and vascular issues .

33. Coronal Images A coronal MRI of the brain  slices the head vertically from front to back, providing a head-on view of the brain's internal and external structures. This plane is ideal for assessing the symmetry of the brain's hemispheres, examining the limbic system, and evaluating the ventricles & especially useful for inspecting the hippocampus and amygdala(temporal lobe)

34. A bnormal brain MRI  Structural and vascular abnormalities:  These can include tumors , abnormal blood vessels (like arteriovenous malformations), or bleeding in or around the brain . Infection:  MRI can show signs of infection, such as restricted diffusion or T2 hyperintensity in specific areas of the brain . Developmental and genetic conditions:  Abnormalities can be associated with developmental delays and specific genetic syndromes. Inflammatory conditions:  Some autoimmune or inflammatory disorders that affect the brain may show up on an MRI, such as the subtle changes seen in pediatric acute-onset neuropsychiatric syndrome (PANS ). Other incidental findings:  Some abnormal findings are not necessarily a cause for immediate alarm but may require monitoring. Examples include certain types of cysts (e.g., pineal cysts ).