MAGNETIC RESONANCE IMAGING OF BRAIN

MRI MODALITY

Created by Students in Degree Medical Imaging Semester5/2012

Magnetic Resonance Imaging (MRI) is a medical imaging technique that is used in the radiological study that uses a magnetic field and pulses of radio wave energy to make the pictures of the organs and structures inside the body which also enables to show the pathology that other imaging modalities cannot visualized.
The MRI modality used the magnetic instead of the radioactive material hence, it does not involved the ionizing radiation which enable to protect the patient from the radiation.
As the electric current flow through the wire coil in the MRI units, it produced the radio waves which can be digitally formed the signal detected by computer to generate a series of image.
The series of image shows a thin slice of the body which can be easily studied and interpreted by the radiologist from the different angles and views.
The MRI images enables to distinguish the abnormal tissues more apparent and clear compared to the manifestation of the images from other modalities such as CT Scan and ultrasound.
It is also proven that the MRI is the most sensitive imaging study for the head particularly brain in routine clinical practice.

WHAT IS A MRI BRAIN ??

A MRI Brain is a type of head scans that use to examine tumors, cyts and internal bleeding. The MRI procedure is a painless procedure that takes between 30 and 60 minutes.

Normal Sagittal view of MRI brain

Normal Coronal view of MRI brain

Normal axial/transverse view of MRI brain

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ANATOMY OF THE BRAIN

The anatomy of the brain is divided into 3 component which are forebrain,midbrain and hindbrain. Forebrain is subdivided into 2 components which are cerebrum and diencephalon. The outermost cerebrum is the cortex which is made up of gray matter and the inner cerebrum is the centrum semiovale which is made up of white matter with pockets of gray matter.

The cerembrum is further divided into 2 hemispheres which are left and right and separated by the longitudinal fissure. The 2 hemisphere communicate to each othe through a structure called corpus callosum. Each hemispheres have 5 different lobes known as the frontal lobe, parietal lobe, occipital lobe, temporal lobe and the central lobe. The fissure that separate the frontal lobe from the parietal lobe is called is called central fissure.

The lateral fissure separate the temporal, parietal, and frontal lobes while the transverse fissure divide the cerebrum from the cerebellum.

The diencephalon is composed of the thalamus and the hypothalamus. The hypothalamus acts as an intermediary between the endocrine system and nerves system and is connected to the pituitary gland by the infundibulum the thalamus forms the lateral walls of the third ventricle.

The midbrain is consist of the tectum which is located posteriorly and the peduncles which located anteriorly. The structure that passing trough the midbrain is know as cerebral aqueduct.

The hindbrain is consist of 3 components which are the cerebellum, pons, and medulla oblongata. Cerebellum is the largest of the three which is divided into 2 hemispheres with the 2 hemispheres communicating through the vermis. The most inferior portion of the hind brain, the medulla oblongata continue as the spinal cord below the level of the foramen magnum.

The brain stem is made up of the midbrain, pons, and medulaa oblongata.

PATHOLOGY OF THE BRAIN

Pathology is a study of disease. These are the common pathologies that are related to the MRI brain.

Brain Tumor

it is an abnormal growth of cells within the brain which can be cancerous/non-cancerous or can be known as malignant/benign respectively.
it is also define as any intercranial tumor created but abnormal and uncontrolled cell division.
Primary (true) brain tumors are commonly located in the posterior cranial fossa in children and in the anterior 2/3 of the cerebral hemisphere in adult although they can affect any part of the brain.

more information about brain tumor,Brain Tumor, National Brain Tumor Society

Strokes

A stroke is a condition in which a brain cells suddenly die because of a lack of oxygen. This can be caused by an obstruction in the blood flow or the ruptured of an artery that feeds the brain.
The two main types of strokes are ischemic and hemorrhage.
Ischemic Stroke: Ischemic stroke accounts for about three quarters of all stroke and occurs when a blood clot or thrombus forms that block blood flow to the parts of the brain.
If the blood clot forms somewhere in the body and breaks off to become free floating and it is called an embolus.
This wondering clot may be carried through the blood stream to the brain when it can cause the ischemic stroke.
Hemorrhage Stroke: it occurs when a blood vessel on the brain's surface ruptures and fails fills the space between the brain and skull with blood (subarachnoid hemorrhage) or when a defective artery in the brain burst and fills the surronding tissues with blood (cerebral hemorrhage).

more information about stroke Stroke Information Page, Hemorrhagic Stroke and Ischemic Stroke

Epilepsy

Epilepsy is a brain disorder in which a person has repeated seizures (convulsions) over time.
Seizures are episodes of disturbed brain activity that causes change in attention or behaviour.
It occur when permanent changes in brain tissue caused brain to be too excitable.
Common cause of epilepsy are strokes or translent ischemic attack, dementia, traumatic brain injury, infections (brain abcess, meningitis, encephalitis), brain tumor and abnormal blood vessels in the brain.

more information about epilepsy, Epilepsy, epilepsy

Alzheimer disease

Alzheimer disease is a form of dementia. It begins slowly and first involves the part of the brain that control talk, memory, and language.
People with Alzheimer disease may feel difficult to remember things that happened recently or names of the people that they know.
When the Alzheimer disease is suspected, the diagnosis is usually confirmed with test that will evaluate the behaviour and thinking abilities, often followed by a brain scan if the memory loss.

more information about Alzheimer Alzheimer, alzheimer disease, dementia:alzheimer

Multiple Sclerosis

Multiple Sclerosis is an autoimmune disease that affects the brain and spinal cord.
It affects woman more than a man.
It is caused by the damage to myelin sheath which is function as a protective covering that surrounds the nerve cells.
When this nerve covering is damage, the propogation of the nerve signals will slow down or stop.
As the multiple sclerosis progresses, the tremors, visions impairment, and urinary bladder dysfunction develop, along with a continued weakening of the muscles.

more about multiple sclerosis, multiple sclerois, MS, MULTIPLE SCLEROSIS

Encephalitis

Inflammation of the brain
Usually refers to brain inflammation caused by a virus or resulting from viral infection
It's a rare disease
It is an approximately 0.5 per 100,000 individuals
It is an actual incidence of encephalitis is probably much higher — but because most people have such mild signs or symptoms, many cases go unrecognized.

more about encephalitis, Encephalitis, ENCEPHALITIS and encephalitis

Meningitis

The meningitis is divided into three types which are bacterial meningitis, viral meningitis and fungal meningitis.
Viral Meningitis : Most cases of this type meningitis are caused by a viral meningitis which is usually mild and commonly clear on its own within two weeks.
Fungal Meningitis: It is relatively uncommon to occur in normal person but it is often seen in acquired immunodefiency syndrome (AIDS) patients or individual undergoing immunodepressant drug therapy.
Bacterial Meningitis: It is the most common serious infection of the central nervous system which can cause fatal
The bacterial meningitis is usually starts with the bacteria that cause a cold-like infection.
The bacterial meningitis can cause blockage to the blood vessels in the brain and may lead to stroke and brain damage.
The bacterial meningitis also can also harm to other organs.

more about meningitis, Meningitis, MENINGITIS and meningitis

LIMITATIONS

High quality images are assured only if you are bale to remain affectly still while the images are recorded. If you are anxious, confused, or in severe pain, you may find it difficult to lie still during imaging.
A person who is very large may not fit into the opening of certain types of MRI machines.
The presence of an implant or other metallic objects sometimes make it difficult to obtain good images. patient movement also can have the same effect.
MRI generally is not recommended for patients who have pain accurately injured, however this is a clinical judgement. This is because traction devices and many types of life support equipment must be kept away from the area to be image. Futhermore, the examination takes longer time than the other imaging modalities (typically x-ray and CT) and the result may not be immediately available as is often necessary in trauma situations.
Although there is no reason to believe that MRI harms the fetus, pregnant woman, usually adviced not to have an MRI exam unless medically necessary.
MRI typically caused more compared to other imaging modalities.

ADVANTAGES

MRI is a non invasive imaging technique that does not involve exposure to ionizing radiation.
MRI's patient acceptability is high due to its requirement of little patient preparation and is non-invasive .
MRI images of the brain are clearer and more detailed than with other imaging method.
MRI major technological advantage is that, it can characterized and discriminated among tissues using their physical and biochemical properties (water, iron, fat and extravascular blood and its breakdown products) blood flow, cerebrospinal fluid flow, and contraction and relaxation of organs, both physiologic and pathologic, can be evaluated.
MRI produces sectional images of equivalent resolution in any projection without moving the patient.
MRI able to produce image in any body plane.

DISADVANTAGES