Role of Magnetic Resonance Imaging in Various Syndromes - Essay Example

Running Header: Magnetic Resonance Imaging Student’s Name: Instructor’s Name: Course Code & Name: Date of Submission: Magnetic Resonance Imaging Magnetic resonance Imaging gives a good contrast between the body and the soft tissues of the body (Hackensack 2011, p 619). This makes it a very powerful component in the in providing detailed images of the heart, muscles and the brain compared to other methods of imaging in medicine like X –rays and computed tomography. This is because, unlike the traditional X-rays and CT scans, the MRI does not use Ionization radiation. Though CT gives a good spatial resolution, MRI does provide comparable resolution that has better contrast resolution. MRI scanner includes those for which can produce an optimized image contrast which are based on the chemical sensitivity (Arijitt etal 2008). In medicine, typical MRI examination consists of sequences which are chosen to provide a certain type of information on the subject tissue. It is this information that is synthesized and interpreted by the physician. This essay is shall discuss how the MR and MRI is used with respect to hippocampus, epileptic seizures, Alzheimer’s disease , brachial plexus and the thoracic outlet syndrome. 1. Review of the anatomy and normal MR appearance of the hippocampus. Suggest an MRI protocol for the patient presenting with generalized epileptic seizures The hippocampus is one of the major and important components of the human brain that is involved with many diseases. MR imaging is useful in visualizing the hippocampus to enable detection of pathologic entities such as atrophy or hippocampal sclerosis in patients who have Alzhimer’s disease or temporal lobe epilepsy. Although the majority of estimates of signal abnormality and hippocampal size have clinical value, precise imaging helps to further delineate to the smallest atomic detail of the hippocampus. As a result it is possible to get the very sensitive and localized lesion in the structure. Two major parts constitutes the hippocampus, the dentate gyrus and the hippocampus proper. Below the hippocmpal fussure is the subiculum where superior curvature occupies. Hippocampus which represents allocortex or primitive is separated from temporal neocortex by a transitional zone of subiculum. Hippocampus proper constitutes of six layers; alveus, stratum oriens, stratum pyramidale, stratum radiatum, stratum lacumosum and stratum moleculare. The alveus covers that portion of hippocampus which protrudes in the temporal horn of lateral ventricle. Its main path of efferent is followed by subcular axons and the hippocampal. Anatomic details of the hippocampus correlates closely with the findings of anatomic in cadaveric section. Imaging could be improved through use of pulse sequence of MR. This method would also allow the acquisition of acquisition of large matrix examinations that can be accepted over a period of time that can be accepted clinically. This technique therefore helps to improve the anatomic details. More so, it helps to detect the abnormality of signals that arise as a result of hippocampus. Hackensack observes that with very fine refinement in MR technology the fine anatomic details of hippocampus are identified (2011, p 635). Though the cellular structures of the hippocampus proper are above the resolution of the current technique, some of the atomic structures can be identified with consistency. Hippocampus, as in caudate nucleus do form and arc which runs roughly runs roughly rostral to the caudal with the head, body and tail in the medial temporal lobe. The hippocampal head is marked by hippocampal digitations that are sagittally oriented which enfolds the various layers of the hippocampus proper of which each is surrounded by a digital extension of the dentate gyrus. Figure 1: MR Appearance of Hippocampus Hippocampus belongs to limbic system therefore playing a very important role in spatial navigation and long-term memory. It is paired structure, having halves of mirror-image; right and left sides of the brain Jung, (Jung , Robert & Richard, 1997 18). In human beings and other closely related primates, hippocampus is located within the medial temporal lobe underneath the cortical surface. Most studies show a high percentage of elderly people suffer from is shrinkage of hippocampus. Jung, Robert & Richard (1997p. 28) further observe that there is also a reliable relationship between hippocampus size and the memory performance. Epileptic seizure, often referred as fit is often defined as transitional symptom involving synchronous neuronal and abnormal excessive activities in brain. The outward effect may be as mild like a brief awareness loss or dramatic like a very fast thrashing movement. Arijitt etal observes that clinicians may organize different types of seizure depending on whether the seizure is within the brain, localized or distributed (2008). The distributed one is known as generalized seizures. Partial seizures are further subdivided according to the extents to which the seizure gets affected. Hippocampus is closely related to epileptic seizure since hippocampal sclerosis is the most significant type of tissue damage in temporal lobe epilepsy. Epilepsy and seizure disorder are paroxysmal events that arise due to excessive, abnormal hyper synchronous discharges from a one of the constituent of the central nervous system ( Stacy & Jonathan, 2009, p.340). This results to imbalance of inhabitation and excitation within the CNS. This abnormal activity may have various manifestations which depend on the discharge distribution or the abnormality of the structure. MRI is widely used to help in the diagnosis of multiple sclerosis (MS) and more so in follow up. There are guidelines for standardizing spinal cord and brain MRI protocol already developed. For a patient who has Clinically Isolated Syndrome and is suspected to have MS the following are recommended baseline evaluations. A brain MRI accompanied by gadolinium. MRI of Spinal Cord if there have been persistence in uncertainty of diagnosis involving brain MRI or these findings are equivocal. MRI of Spinal Cord if the signs or the symptoms presented are at the level of the spinal cord. The recommended follow up for evaluation is MRI of the brain that would enable demonstration of new disease activity. For patients who have already been diagnosed and established to have MS, the following guidelines recommended are of brain MRI with gadolinium. For the follow up of MS patients, a brain MRI with gadolinium, the following would be recommended Evaluation of any unexpected clinical worsening that concerns the secondary diagnosis. Reassessment of the original diagnosis Reassessment before modify or modifying therapy To assess subclinical disease the activity should be considered in duration of between one and two years. The exact frequency may vary mostly depending on clinical course and other clinical features. A patient with epileptic seizure has brain disorder that is characterized by enduring predisposition of the general epileptic seizure. Diagnosis is of 2 unprovoked seizures that are 24 hours apart. Epilepsy seizure has a repetition time of approximately 25 to 3600 ms and echo time of 40ms. 2. Discuss the role of MRI in the assessment of Alzheimer’s Disease A spinal cord MRI involving gadolinium is what is recommended for the follow up of the MS patients who have the clinical evidence of the disease activity that is referable to the spinal cord or those who do not have MRI evidence in the brain. Figure 2: MR appearance of Alzheimer Stacy & Jonathan (2009) observes that the Alzheimer’s disease is one of the common forms of dementia in the elderly. The classic symptoms of the disease includes confusion, memory loss and biological features like the formation of the neurofigrillary tangles, senile plagues of amyloid and the gray matter atrophy in the brain. Early diagnosis of Alzheimer’s disease would produce a positive outcome which would result to development of specific drug therapies. The development of quantitative non-invasive imaging methods of diagnosing AD would result in MRI based methods that do rely on the contrast generated by the two variations. According to Hackensack, exquisite soft-tissue contrast of MRI is provided by the relaxation mechanism in the different tissues of the brain (2011, p 619). For example, tissues with highly mobile water appears brighter in MR images which are T2 weighted whereas the brain parenchyma is seen highlighted in the images which are weighted as T1. However, hippocampal T2 has significant difference with the Alzheimer’s disease for the normal patient. Another alternative contrast used is the mechanism of spin lattice relaxation time contrast in the rotating frame. This used to determine the decay of the transverse magnetization which is in the presence of radio-frequency field. For a long time MRI has been used to measure the relaxation time of the normal brains. This relaxation time is to a very great extent influenced by the molecular process that occurs in a very short range, usually milliseconds. In the biological tissue, the spin relaxation time is dependent on the free water and the macromolecular process. Short echo time is used for detecting Alzheimer disease. The echo time is 22 to 25 ms while repetition time ranges between 415 and 800ms. The variation is mostly due to age of the disease. 3. Review the anatomy and MR appearance of the brachial plexus. Suggest an MRI protocol for a patient presenting with thoracic outlet syndrome. The modality choice for the detection of the abnormality of the cerebral structure is MRI. Today, MRI, EEG and clinical data are collected and analyzed. The present study shows the etiologies of epilepsy in the selected groups of patients that have been sent out for MRI study. Higher magnetic field strength and the techniques of the MRI gives a higher signal-to-noise ratio, which reduce the acquisition time and the improvement of the spatial resolution and the accuracy of the diagnosis. The MR spectroscopy and the functional MRI can be used to assess the metabolites of the localization of cognitive and the epileptogenic foci which gives a better clue on the kind of surgical treatment that is required. Stacy & Jonathan (2009) observe that the MRI of the brachial plexus has become the imaging modality of choice which is after the introduction of the MRI in the practices of the clinic. With just a conventional radiography, it had been impossible to visualize the brachial plexus at all. However, with the introduction of the CT, it has been easy to visualize to the details most of the important landmarks that have constant relationship with the brachial plexus. This includes subclavian artery and the scalene muscles among other components of the brachial plexus. Spiral CT that has sagittal and coronal reconstructions can also be used; however the quality of the imaging would be less than the optimal due to the presence of the shoulders in the regions of interest. The region that involves the brachial plexus is also difficult to evaluate using the ultrasound because of the underlying bones since only landmarks are visible. The excellent anatomic study shows the possibilities of MRI in the delineating of the anatomy of the brachial plexus. Because of the inherent differences and the contrast between the MR signals from the brachial plexus, the related vessels and fat, components of the brachial plexus as well as in MRI which can be visualized in the desired plane. The indications for the MRI of the brachial plexus are seen in two ways: Symptoms like the pain, muscular atrophy and neural deficit that are due to the pathology of the brachial plexus. The analysis which includes pre-operative evaluation involving pathology which is usually a tumour that is in the region of the brachial plexus. It includes the neck, the axilla and supra and infra-clavicular region. The brachial plexus originates from roots C5, C6, C7, C8 and T1 that are occasionally contributed by C4 and T2 ending in five peripheral nerves. Before the formation of the brachial plexus, there are complex intermingling involving ventral rami of the root through three trucks, six divisions and three cords. Figure 3: MR Appearance of brachial plexus Brachial plexus could be involved with many different pathological processes. This involvement is basically well demonstrated using MRI. Among the most commonly demonstrated processes that affect the brachial plexus leads to the effect of the trauma to the brachial plexus. Through primary neoplasms involving brachial plexus are uncommon; they include both malignant neurogenic and benign tumors. The four main tumors; neuroma, neurofibroma, schwannoma and neurofibrosarcoma. According to Stacy & Jonathan ( 2009, p.323), thoracic outlet syndrome refers to the symptom which arises when the nerves that involve the blood vessels are compressed to the thoracic outlet. The thoracic outlet constitutes the upper aperture of the chest which lies between the first rib and the collar bone. This narrow passageway is usually crowded with blood vessels which run to the arm from the chest. These nerves join forming 3 large brachial plexus which runs through the thoracic outlet and again splits up again forming separate nerves lower down. Thoracic outlet syndrome causes nerve compression. Its repetition tome is approximately 44 ms on MRI and the echo time is approximately 10 ms In conclusion, hippocampus, epileptic seizure, Alzheimer’s disease and brachial plexus have appearances that could be investigated using both anatomy and normal MR appearance. Magnetic resonance imaging is a medical imaging technique that is used in radiology to enable the visualization of the internal structure of the body. It makes use of the property of magnetic resonance of nuclear to enable nuclei imaging of the inside of the body. MRI machines make use of very powerful magnetic fields to align the magnetization of some atoms References Arijitt B, Mathew S, Christos D, John Q & Christopher , M, 2008, ‘MRI of Alxheimer’s disease’International Journal on NeuroImage Vol. 1, no.1, pp. 68-73. Hackensack, P 2011, ‘Consortium of MS Centers MRI Protocol for the Diagnosis and Follow-up of MS’, Journal on Consortium of Multiple Sclerosis Center, Vol. 3, no.7, pp. 618-650. Jung, H, Robert, K, & Richard, A, 1997, ‘Embrology of the human fetal hippocampus : MR imaging, Anatomy and Histology’, Journal on American Society of Neuroradiology, Vol. 2, no.3, pp. 18-25. Stacy, T, & Jonathan, B, 2009, ‘Guideline for the management of the first seizure’, International Journal on Emergency Medicine, Vol. 23, no.1, pp. 323-350. Read More