MRI Radiation – Dangers & Benefits

magnetic resonance resource ( attractionised resonance imaging) is a new engineering science for making go outs of the brain and other parts of the body. The technique depends on sleuthing of a phenomenon called nuclear drawic resonance, and also sometimes called NMR s toleratening. The find and development of magnetic resonance imaging imaging is one of the most spectacular and happy events in the history of medical checkup imaging.The nuclei of some atoms in the body are composed of numbers of nuclear particles. such nuclei apprise be find by sending weak energy signals through very rugged magnetic fields. The magnetic resonance imaging machine consists of a set of powerful magnets and a source of energy in the same general range employ for broadcasting piano tunercommunication. The radio signal is affected in predic shelve shipway by the number of odd-numbered nuclei in its path (Oldendorf Boller, Grafman and Robertson).The magnetic resonance imaging ProcedureT he MRI contains the massive main magnet, which is always on. The unit structure is approximately half-dozen or seven feet high and equally wide. As a diligent, you leave behind lie on your back on a special table that slides into the magnet through a two-foot-wide tunnel in the middle of the machine. Whether you go in head or feet first depends on the weave creation imaged.Be prepares for a loud knocking noise this is not a silent machine. The loud knocking noise is cause by the gradients (small magnets) expanding against the supporting brackets. The MRI scanner impart able to pick out voxels ( cubic cubes) maybe exactly one millimeter on each side. It will make a two-dimensional or three-dimensional map of tissue type. The computer will integrate this information and create two dimensional images (the usual) or three-dimensional models. The whole procedure takes from 30-60 minutes (Moe).Advantages and DisadvantagesDue to the nature of the magnetic investigation used in MRI, this technique possesses several fundamental advantages 1) tissue can be characterized in a number of ways, 2) any plane can be imaged 3) bone is invisible, so all anatomic regions can be examined, and harper images are produced 4) no contrast medium is required and 5) thither is no ionizing radiation, which makes it safe for youngsterren and for repeated scanning of the same person 6) the direct of detailed exceeds the detail of other imaging techniques.At the present time, in that respect are also several disadvantages 1) he complexity and high monetary value 2) the long scan time, 3) the noise isolation experienced by forbearing during scan and 4) the exclusion of substantial fraction of patients dues to pacemakers, metallic artifacts, and in king to cooperate. Further more(prenominal), magnetic strength can be a dangerous thing. Stories abound the magnets power to pull metal objects (such as paper clips, keys, scissors, stethoscopes, IV poles, and even oxygen tanks) towar d the patient and into the machine.Even worse, accidents present occurred with metal wrong a patient. After an MRI, a metal worker went blind because the magnet moved microscopic metal particles in his eyes, damaging their border structures. A survivor of and aneurysm died during an MRI because the magnet tore off the metal clips holding together a blood vessel in her brain, make her to bleed to death.The patient must sting absolutely doubtless during the procedure. (Minor motion does not have as much impact on a CT scan.) Therefore, a sedative is often necessary for a child having an MRI scan. The first three of these are under active development, and value can be expected. However, gradient coil noise, pacemakers and metallic artifacts are more fundamental problems for which solutions are not yet apparent (Stergiopoulos).MRI in association with CTMagnetic resonance imaging is another regularity for displaying anatomy in the axial, sagittal, and coronal planes. The slice th ickness of the images vary betwixt 1 and 10 mm. MRI is especially good for coronal and sagittal imaging, whereas axial imaging is the forte of CT. One of the main strengths of MRI is its ability to detect small changes (contrast) within soft tissues, and MRI soft tissue contrast is better than that found in CT images and radiographs.CT and MR imaging modalities are digital-cased technologies that require computers to convert digital information to shades of foul, purity and gray. The major difference in the two technologies is that in MRI the patient is exposed o out-of-door magnetic fields and radio oftenness booms, whereas the patient is exposed to x-rays during a CT study. The magnetic fields used in MRI are believed to be harmless. MR scanning can be a problem for people who are prone to develop claustrophobia because they are surrounded by a tunnel-like structure for approximately 30-45 minutes.The external expression of an MRI scanner or machine is similar to a CT scann er with the exception that the rudeing is the MR gantry is more tunnel-like. As in CT, the patient is comfortably positioned supine, prone, or decubitus on a couch. The couch moves and when examining the extremities. The patient hears and feels a jackhammer-like thumping while the study is in progress.The underlie physics of MRI is complicated and strange-sounding terms proliferate. Lets cargo deck it simple MRI is essentially the imaging of protons. The most commonly imaged proton is hydrogen, as it is abundant in the human body and is easily manipulated by a magnetic field. However other nuclei can be imaged. Because the hydrogen proton has a positive charge and is constantly spiralning at a decided absolute frequency, called the spin frequency, a small magnetic field with a compass north and south pole surrounds the proton. Remember that moving charged particles creates a surrounding magnetic field. Thus, these hydrogen protons act like magnets and align themselves within an external magnetic field or the needle of a compass.In the MR scanner, or magnet, short bursts of radio frequency waves are broadcast into the patient from radio transmitters. The broadcast radio wave frequency is the same as the spin frequency of the proton being imaged (hydrogen in this case). The hydrogen protons absorb the broadcast radio wave energy and become energized, or resonate. Hence, the term magnetic resonance.in one case the radio-frequency wave broadcast is dis go alongd, the protons revert or decay back to their universal or steady state that existed prior to the radio wave broadcast. As the hydrogen protons decay back to their normal state or relax, they continue to resonate and broadcast radio waves that can be detected by a radio wave receiver set to the same frequency as the broadcast waves and the hydrogen proton spin frequency. The color of the radio wave signal detected by the receiver coil indicates the numbers and locations of the vibrate hydrogen prot ons.Although human anatomy is always the same no social function what the imaging climate, the lookances of anatomic structures are very different on MR and CT images. Sometimes it is difficult for the beginner to differentiate between a CT and an MR image. The secret is to look to the naughty. If the subcutaneous flump is black, it is a CT image as fat appears black on studies that use x-rays. If the subcutaneous fat is white (high-intensity signal), then it has to be an MR. next, look to the bones.Bones should have a gray medullary canal and a white cerebral cortex on radiographs and CT images. The medullary canal contains bone marrow, and the gray is due to the lifesize amount of fat in bone marrow. On a MR image, nigh all of the bone appears homogenously white as the bone marrow is fat that emits a high-intensity signal and appears white.Also, on MR the cortex of the bone will appear black (dark or secondary intensity signal), whereas on CT images the cortex is white. S oft tissues and organs appear as shades of gray on CT and MR. Air appears black on CT and MR. air appears black on CT and has a low-intensity signal (black or dark) on MR (Moe).Intraoperative MRIAt present, MRI is, by far, the most useful imaging modality for visualizing intracerebral tumors. It provides the most clear, detailed, and comprehensive diagnostic information regarding the tumor ad surrounding normal structures. The introduction of MRI and image-guided technology into the operating means thus allows the surgeon to use high-quality, current image data that contemplate the surgical reality of brain tissue deformations and shifts that occur after the bone flap has been turned, the dura opened, and the resection begun.Todays intraoperative MRI systems can be classified into two main groups 1) the high field strength systems and 2) the low compact systems. Both types of systems have advantages and disadvantages. The high-field strength systems (0.5-1.5 T) are typically mount on a stationary gantry and have gradient capabilities suitable to produce full head images of quality comparable to that of diagnostic MRI.Magnetic resonance imaging can satisfy these requirements for therapy. It has excellent anatomic effect for targeting, high sensitivity for localizing tumors, and temperature sensitivity for online treatment monitoring. Several MRI parameters are temperature sensitive the one based on the proton resonance frequency allows comparatively small temperature elevations to be detected prior to any irreversible tissue damage.Thus, the location of the focus can be detected at relatively low powers, and the accuracy of targeting can be verified. In addition, using set temperature-sensitive MRI sequences, focal temperature elevations and effective thermic doses may be estimated. Such thermal quantification allows for online feedback to ensure that the treatment is safe, by assuring that the focal heating is confined to the target volume and below the level for boiling. Thermal assessment predicts effectiveness by assuring that the temperature history is sufficient to ensure thermal coagulation (Moore and Zouridakis).ConclusionSince the first availability of commercial instruments at the offset printing of the 1980s, clinical MR has expanded rapidly in terms of both medical finishs and the number of units installed. First considered to be expensive method to create images of low quality, it has since established itself as a clinical tool for diagnosis in previously inconceivable applications, and the potential of the method is still not exhausted. MRI has led to the first-scale industrial application of superconductivity and has brought about a grater public sense of a physical effect previously known only to a handful of scientists.Up to now, the growth and spectrum of applications of MR have exceeded all predictions. The most juvenile development is that of rendering brain functions visible. Cardiac MR can display corona ries and die perfusion of the myocardium and hemodynamics of the heart. Thus, MRI is entering the domain of nuclear medicine.An interesting new application of MRI is its use as an imaging modality during minimal invasive procedures such as ablation, interstitial laser therapy, or high intensity focused ultrasound. With temperature-sensitive sequences, the development of temperature and tissue damage can be suss out during heating and destroying of diseased tissue. The sensitivity of MRI to flow helps the physician to stay away from vessels during an intervention. MRI is also used for image-guided surgery, e.g., resection of tumors in the brain. Special open systems have been designed for such purposes, and dedicated non magnetic surgery tools have already been developed (Erkonen and Smith). Works CitedBoller, Franois, Jordan Grafman, and Ian H. Robertson. Handbook of Neuropsychology. Vol. 9. reinvigorated York Elsevier Health Sciences, 2003.Erkonen, William E., and Wilbur L. Smi th. radiology 101 The Basics and Fundamentals of Imaging. 2nd ed. New York Lippincott Williams & Wilkins, 2004.Moe, Barbara A. The Revolution in Medical Imaging. New York The Rosen Publishing Group, 2003.Moore, James E., and George Zouridakis. Biomedical Technology and Devices Handbook. New York CRC Press, 2004.Oldendorf, William. Basics of Magnetic Resonance Imaging. Boston Springer, 1988.Stergiopoulos, Stergios. Advanced Signal touch on Handbook Theory and Implementation for Radar New York CRC Press, 2001.