Brain Lesion techniques
Brain lesions refer to regions of the brain that have been impaired as a result of infections and malformations associated with inheritance or trauma (Garg & Sinha, 2010). Although this condition is quite scaring to many people, the degree of brain lesions differs significantly from one case to another.
Hence, proper diagnosis is vital in order to ascertain the severity of the damage. Nonetheless, evidence based research reveals that in spite of the high success rate on brain lesion techniques, there is still no perfect technique. There is need to understand the merits and weaknesses of each technique before applying it. The underlying assumptions should be established beforehand.
The idea behind radiosurgery in the removal of brain lesions came as a result of the need to control and treat functional brain disorders (Garg & Sinha, 2010). For a long period of time, the use of radiosurgical methods in the treatment of lesions was restricted in other parts of the body and not the brain owing to sensitive nature of the latter and inability to conclusively detect damaged parts of the brain in advance. Nonetheless, lesion removal methods have advanced with the incorporation of computer tomographcal images in the process.
Moreover, the distribution of radiation on the affected spot in the brain can now be calculated to ascertain that the right amount of radiation is directed in the impaired zone. This is indeed a very successful advancement in technology as far as the diagnosis and treatment of brain lesions is concerned. However, the identification and eventual treatment of damaged spots in the brain still require thorough research in order to conclusively deal with this medical challenge.
Non invasive techniques are used in contemporary applications of radiosurgery whereby suspected lesions are destroyed with high level of precision without due interference with the unaffected parts of the brain. In order to achieve the right dosage of radiation, two main classes of radiant energy have been employed; the particulate that makes use of the beam from positively charged particles or a beam of radiation from helium while the second form of radiant energy has been electromagnetic.
In the case of electromagnetic energy, cobalt 60 radioisotope decays naturally and leads to the emission of gamma rays with high penetrating power. This energy is then used for radiosurgical operations. It is popularly known as the gamma knife. On the other hand, linear accelerators are used to emit a beam containing a photon or packet of energy (Goulet, et al., 2009). To achieve the highest level of precision and avoid missing the target, a technique called stereotactic is used.
Although radiosurgery has been used in the treatment of myriad types of impairment on other body parts, it is more effective when dealing with arteriovenous malformations. Nonetheless, the effectiveness of this technique does not lack its own side effects. For instance, radiation necrosis has been established as the main cause of concern. Transient neurologic deficiencies may be caused by the edema close to the lesions that have been treated.
The complication can however be minimized by being meticulous on the amount of radiation dosage directed at the lesion. It is imperative to note that radiosurgery has not been fully fledged as a primary method of removing brain lesions since the effectiveness of the technique is still under investigation. Moreover, the technique is commonly applied to outpatients due to its effective and affordable nature. This will indeed make the method be largely used in the treatment of lesions.
Survival can also be enhanced through the surgical removal of brain lesions especially those that are separately located or grouped together. There are several reports indicating successful surgery technique in the removal of brain lesions. One of the lately promoted surgical methods is that involving multiple craniotomies in the event there are several lesions.
In spite of the high success rate of the method when removing isolated lesions, the wound left after operation may undergo infection in addition to hemorrhaging. Besides, there is evidence of complications related to pulmonary embolisms as well as thrombosis of the vein after undergoing operation not forgetting the fact that such postoperative cases are very common.
When an extremely high level of precision is desired, radiosurgery is often a better option. The technique permits the releasing of radiation with optimally high dose. By use of the gamma knife, multiple beams can be converged at one single point to generate high radiation. Besides, there is a significant improvement in the neurological impairment with over 50 percent of the affected patients successful.
Firstly, aspiration is a common primary modality that seeks to detach the cortical tissue from the damaged part. The aspiration process should however be guided using stereotactic CT so that side effects such as high pressure hemorrhage from the brain can be minimized.
Moreover, radio-frequency has also been endorsed as a primary lesion removal technique from the brain. It is carried out as a sub cortical lesion removal method. The high heat of the current flow is then used to remove the lesion. For severing tracts, it is convenient to make use of small knife cuts.
When cryogenic blockade is used in the removal of brain lesions, the affected tissue is taken through a process of temporal cooling. This is done until all the activities in the surrounding of the target come to an end. This process is similar to reverse lesion removal. In addition, an electrical method can also be used to eliminate the brain lesion.
The effect generated by stimulation of electric current is considered to be the converse of those produced by the lesion within the same site of the affected brain. To achieve the best results, a research on electrical simulation is carried out before any lesionig is done.
There are four main electrical recording methods that are employed when applying the brain lesion techniques discussed above. To begin with, we have the intracellular unit recording. This recording technique relates the potential of the neutron membrane with respect to time.
The measure is recorded in form of changes. As a requirement, the neutron should carry the microelectrode. In the case of animals that are freely moving, it is not easy to take this measure since it is cumbersome to place the microelectrode in the neutron. Since the method cannot be used in moving animals, it makes it quite cumbersome to carry out tests and procedures on the latter, thereby limiting the use of this technique.
The second type used is referred extracellular unit recording. Unlike in the intracellular unit recording, the neutron and microelectrode are positioned near each other. The sequence of spikes generates the signal whereby the potential action from the proxy neutron is indicated by each spike. When a series of spikes generate the same amplitude, the assumption is that they have a common origin of the neutron.
The third type of measurement, multiple unit recording, gives information on the rate at which firing is taking place within the surrounding of the tip of the electrode. For instance, if a microelectrode is smaller than the electrode itself, it will tend to gather the action potentials from the myriad of neutrons that are within the vicinity.
The last method of measure is referred to as invasive EEG recording. In order to record the EEG for animals used in laboratory tests, this method is quite convenient. the implanted electrodes are used alongside this recording technique. The rationale behind deploying this recording method is that there is lack of clear recording when scalp electrodes are used.
Brain Imaging Techniques
There are quite a number of both conventional and modern methods of visualizing the human brain. Firstly, contrast X-rays have been used for a lengthy period of time. Using a photographic plate, an X-ray is transmitted through the desired part of the brain. The target will then absorb the rays in a different manner and eventually differentiate it from the surrounding matter.
Since the human brain has several overlapping and complex layers, using the standard x-rays for taking images is not beneficial since the varying layers have almost the same levels of absorbing standard x-rays. As a result, contrast x-rays are preferred. When using this type of x-rays, the structure of the brain is mapped out using a radio opaque material.
Computerized Tomography (CT) is a more recent development whereby the structure of the brain is mapped out in all the three dimensions. When a Computerized Tomography scan of the brain is taken, about nine sections of the brain structure that are also horizontal in nature are visualized (Goulet, et al., 2009).
The CT scan makes use of both the X-ray gun and its detector. The two apparatus are moved around the brain. As rotation continues from different positions, the image of the brain is taken in series and this is done again in 8-9 distinct levels. Only large brain tumors can be visualized by images taken using CT scan since they are not sharp enough.
The working of the CT is based on the fact that the shadowgraph of the targeted medium is generated by the imaging system. The three dimensional structure is then compacted further into a two dimensional plane. One of the horizontal planes that contain the density data is not compressed and as a result, it stretches itself forth occupying some space.
Although this information per se may not be of significant use, the rotation of the test component, the image of the brain is developed in a cross sectional manner.
Magnetic Resonance Imaging (MRI) is another alternative method of brain imaging. Contrary to the CT scan, this brain imaging technique produces visuals with higher resolution than the former since there is no usage of X-rays (LaConte, Peltier & Hu, 2007).
The hydrogen atoms emit waves which thereafter create the images through a magnetic field (Archibald, et al., 2009). The concreteness of the hydrogen atoms is responsible for the clarity of the image obtained.
Furthermore, the Positron Emission Tomography (PET) is yet another brain imaging technique. Instead of showing the overall structure of the brain, this method works by highlighting the active zones of the brain.
In the process of imaging the brain, 2-deoxyglucose that is radioactive in nature is injected into the desired patient. The 2-DG shares several similarities with the normal glucose and hence its uptake by neutrons is similar to the latter (Kipps et al., 2009). On the other hand, the metabolism of 2-deoxyglucose is not possible by neutrons.
Once the patient has been injected with the radio-active 2-DG, the PET scan is carried out while the target patient is engaged in some form of activity that involves the brain (Schreckenberger et al., 2006). During the PET scan, regions where there is a high accumulation of radio-activity display the brain images and as a result, areas that were exceptionally active as the scan was being carried out will be displayed.
Apart from MRI technique of imaging the brain, functional MRI (fMRI) is also used. This method makes use of the rate of flow in blood through the brain. It is imperative to note that the active areas of the brain are given due consideration during the scan (Chris & Hans-Otto, 2004).This method has quite a number of merits over the PET scan.
Firstly, the patient does not require to be injected with anything in order to study the active sites of the brain as the imaging process continues. In addition, only a single image is required to produce two types of ions namely structural and functional. Besides, fMRI has a higher spatial resolution compared to PET scan and therefore can be used to obtain finer details. Finally, functional MRI is quite convenient since there is a real time measurement of changes which markedly reduces waiting time.
Since it was introduced way back in 1992, fMRI has received unanimous support as one if the potential methods through which the brain can be studied owing to its noninvasive nature. The technique is currently widely used to study both the structure and function of the human brain. At the point where the neutrons are being activated, a response on how both the metabolic and hemodynamic are changing are received as the brain is being stimulated both from inside and outside (Celine et al., 2005).
The entire activation map of the brain can be constructed when this technique is used. As mentioned earlier, the method produces brain images with high resolution. Further, the mental and the sensory functions are both mapped during the brain imaging process. Since the brain is made up of segments and compartments, it necessitates the use of fMRI as the most suitable method. Moreover, psychological signals can also be recorded using a variety of methods as discussed in the literature review below.
The Electroencephalogram (EEG) is used to monitor how waves move through the brain. This measurement technique assesses the overall function of the brain within a given period of time (Mao & Berns, 2002).
For example, EEG has been used for long to evaluate disorders of the brain. In particular, EEG shows the activity level of the brain in terms of the type of action taking place as well as the exact region where the specific action is located. Moreover, this measure is used to assess individuals who experience brain related problems such as tumors, memory difficulties and confusion.
Besides, EEG can also be used to assess other parts of the human body affected by brain problems. This function goes a long way in determining the brain death since it can be employed to evaluate whether a patient on life support equipment will recover or not. Although EEG is a highly sensitive technique, there are very minimal risks in using the method. Before a patient is taken through EEG test, the person may be advised to refrain from taking some seizures or medications used to treat depression.
Although EEG has limited risks, its limitations are numerous. In fact one of the common setbacks of the method is the low spatial resolution. The technique is mainly suitable in cases where images are produced on the upper zones of the cortex.
Moreover, the currents that are produced by the EEG signals cannot be relied upon in the construction of intracranial source of the current since there is an auto cancellation of the generated currents. This inverse problem has however been worked on and it si now possible to obtain estimates that are fairly reliable.
When EEG is compared with other methods for determining activity of the brain such as PET scan and fMRI, it is found that it has a the highest degree of precision and takes the least time to record measurements in terms of milliseconds.
Both fMRI and EEG can be used at the same time if images with high spatial resolution are required within a short time (Mao & Berns, 2002). Nonetheless, the data obtained when the two techniques may not in any case give a representation of the actual activity of the brain since each of the methods provides data at different times.
As a result, technical difficulties arise when the two techniques are used simultaneously in the sense that is imperative to eliminate the MRI substance from EEG so that uniformity is realized when recording data. Nevertheless, these difficulties may not overweigh the merits of the technique. Hence, using both techniques should just be seen as a current challenge that can still be resolved with advanced research.
Latest Advances
Recent developments have also witnessed notable advances in the application of Magnetic Resonance Imaging (MRI). Neurologists can now take quantitative osmotic measure of the brain tissues using Diffusion Tensor Imaging (DTI). The desire to scan white tissues in the brain has occasioned myriad of research studies. For this reason, the osmotic measure or diffusion of water through the axon bundles in the brain is of great importance when studying the brain (Faria & Hoon, 2010).
Hence, these bundles facilitate movement of water within the main channel. This technology is still under neurological research to determine its effectiveness in locating white matter lesions.
In recap, it is imperative to note the study of the brain is complex hence the need to address both brain lesions methods and imaging techniques used to visualize the very brain.
While lesions in the brain are regions that have been damaged or impaired due to injury, tumor or infections, the brain lesions cannot be identified unless the recommended modalities are employed. For instance, radiosurgery method in brain lesion a non invasive techniques is to identify suspected lesions which are thereafter destroyed with high level of precision without due interference with the unaffected parts of the brain.
Finally brain imaging techniques range from the use of contrast X-rays, Computerize Tomography (CT) scan, Magnetic Resonance Imaging (MRI), functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET) scan to Electroencephalography (EEG).
References
Archibald, T. et al. (2009). “Improving tissue segmentation of human brain MRI through preprocessing by the Gegenbauer reconstruction method” NeuroImage, 20: 489
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Celine R. et al. (2005). “Functional magnetic resonance imaging reveals similar brain activity changes in two different animal models of schizophrenia”, Psychopharmacology, 180(4), 724-34.
Chris R. & Hans-Otto K. (2004). “Using human brain lesions to infer function: a relic from a past era in the fMRI age? Nature Reviews”. Neuroscience, 5(10): 813- 819.
Faria, A., & Hoon, A. (2010). “Caveats in diffusion tensor imaging interpretation”. Developmental Medicine and Child Neurology, 52(10), 887.
Garg, R., & Sinha, M. (2010). “Multiple ring-enhancing lesions of the brain”. Journal of Postgraduate Medicine, 56(4), 307-16.
Goulet, K. et al. (2009). “Use of Brain Imaging (Computed Tomography and Magnetic Resonance Imaging) in First-Episode Psychosis: Review and Retrospective Study”. Canadian Journal of Psychiatry, 54(7), 493-501.
Kipps, C.M. et al. (2009). “Combined magnetic resonance imaging and positron emission tomography brain imaging in behavioral variant front temporal degeneration: refining the clinical phenotype”, Brain, 132(9): 2566-2578. LaConte, M.P., Peltier, J.S. and Hu, P.X. (2007). Real-Time fMRI Using Brain-State Classification, Human Brain Mapping, 28:1033–1044.
Mao, S. and Berns, S.G. (2002). “MRI in the study of brain functions: clinical perspectives”, MedicaMundi, 46(1): 28-37.
Rao, S.. (2005). “Functional MRI: Finally, a Textbook for All of Us”. Journal of the International Neuropsychological Society: JINS, 11(4), 498-499.
Schreckenberger, M. F. et al. (2006). “Positron Emission Tomography Reveals Correlations between Brain Metabolism and Mood Changes in Hyperthyroidism”, Journal of Clinical Endocrinology & Metabolism, 91(12): 4786-4791.