The Wonders of Magnetic Resonance Imaging 3 Tesla MRI and the Challenges of Going to Higher Field - Report Example

THE WONDERS OF MAGNETIC RESONANCE IMAGING 3 TESLA MRI AND THE CHALLENGES OF GOING TO HIGHER FIELD Introduction A magnetic field is used to take images of the body, from the brain down to the different parts of our body. A magnetic field can take pictures of the inside features of our body because our body is composed of protons which are actually simple magnets and they produce minuscule magnetic fields. There are hydrogen protons of the body because the human body is composed of 95% water. (Lee, 2006, p. 4) Magnetic resonance imaging uses a magnetic field and radio waves to get a picture of what is inside the body. MRI does not utilize radiation in its mission, unlike the X-Ray which uses radiation to produce an image. A new invention and application of MRI is the 3 Tesla (3T) MRI, the field of magnetic resonance has become advanced. The higher the magnetic field, the clearer the image is taken from inside the body. The MRI has gone a long way, from the 1.5Tesla to the 3T which has become popular in the age of high technology. The use of MRI has become a normal process in diagnosing illnesses. This is particularly very useful in angiography or determining defects or clots in the coronary artery. However, in diagnosing of atherosclerotic coronary artery defects, MRI still suffers some limitations. (Lombardi & Milanesi, 2010, p. 113) MRI is applicable to other major diagnosis of diseases of the brain, the musculoskeletal, and the heart. The 3T can take high-quality images of the bone structure, including the finer tendons and ligaments and the small nerves. Even in pediatric care, the 3T is now being used (Harvey, 2011). For the many organs of the body, MRI can detect blood flow of the liver and of the other inside organs of the human body (Taouli, p. 190). So what are the prospects of going to a higher field in order to produce a more refined image quality, such as SNR, higher contrast and resolution? This and more are the topic for discussion in this paper. Background Magnetic resonance imaging uses a strong magnet to capture an image of the inside of a person’s body. A strong magnetic field that is approximately 60,000 times stronger than the earth’s magnetic field is utilized in a 3T MRI scanner to capture the desired image of the body’s anatomy. The strength of a 3 Tesla scanner can capture images of brain functions. It also has the capacity to have a clinical standard in neuroimaging and many parts of the body. (Sandrick, 2001) Electromagnetism works in magnetic resonance. The magnetic field strength is measured in Tesla. Electromagnetism is a term that refers to magnetism produced by electricity through the application of coil or coils induced with electricity. The term Tesla originates from Nicola Tesla, an electric genius who pioneered several inventions on coils and inductance. He is famous for his Tesla coil. (Tesla Memorial Society of New York, 1998) Magnetic resonance imaging became popular in the medical profession in the 1970s. The first MRI scanner had a lower field strength but soon the 1.5 Tesla MRI was introduced. This was challenged by the 3T MRI which provides shorter image acquisition and higher magnetic field strength. 3T is now widely used for neuro, body and cardiovascular applications. (Jerrolds & Keene, 2009) Nuclear Spin Electromagnetism is produced in MRI. When the body is exposed to electromagnetism, the body responds by emitting minuscule RF signal being carried by the body’s electromagnet. This phenomenon is the result of a mechanical property known as nuclear spin. Nuclear spin allows the nucleus of a hydrogen atom to perform a motion such as aligning or misaligning the direction of the magnetic field. (Nitz, 2007, p. 2) The nuclear spin of the protons inside the body take their position when applied with a magnetic field. The positions that the nuclei will perform can either be parallel or counter parallel with the magnetic field. A signal can be achieved by providing an RF pulse. (Nitz, 2007, p. 24) The magnetic strength of MRI determines the clarity and contrast of the image. At the introduction of magnetic imaging, widely in use then was the 1.5T imaging. The US Food and Drug Administration approved the magnetic strength of up to 4T but the 3T has become the popular MR scanner because of its advantages. There are many factors for the popularity of the 3T and this includes safety considerations. There are beliefs of danger when higher magnetic field is induced upon the patient, but this has been controlled with the application of new technology in hardware and software. Advantages of 3T MRI The signal-to-noise ratio of 3T is higher than any other. It provides a clearer image resolution and a short period of time in acquiring/producing the image. In having a shorter time in acquiring the image, the patient has lesser complaints. The 1.5T has fewer scans. The advantage of the 3T is that its scan time is lower than the 1.5T. The higher resolution obtained by 3T is much applicable to taking images in the head and neck portions of the body. Neurological findings are also enhanced in the use of the 3T. The defects caused by the dielectric effects have already been addressed to through some hardware and software modifications. Siemens also can attest to the safety features of 3T. The Siemens technology for 3T has promoted the 3T MR systems which are quite different from the first introduction of the technology way back in 1998. It has new features that include an RF technology and new designs for hardware and software attached to it. In choosing a 3T design model, the company Siemens advised hospitals and those planning to use the 3T technology to take into consideration some factors or so-called “footprints” like coils, magnet properties, construction properties and other support areas. (Siemens Medical Solutions USA, Inc., 2009) An important usage of the 3R MRI is neuroradiology. 3T offers higher spatial resolution in taking images of the brain. It can attain 2D images with lesser measurement time. (Runge & Case, 2007, p. 52) Signal-to-noise ratio (SNR) It is one of the major concerns of doctors and hospitals who rely on MRIs for detecting diseases: signal-to-noise ratio. A higher magnetic field translates to a higher SNR then a fine contrast, resolution and less measurement and acquisition time. The intensity of the signal determines the clarity and contrast of the image being received by the coils. The signal noise refers to the “image noise” being received by the coils. The images created by MR contain noises and maximizing the noises means producing a clearer image. Signal-to-noise ratio (SNR) is determined using the formula: SNR equals to signal over noise. SNR is affected by the time required to create the image. 3T MRI is effective in this sense because it requires lesser time to take the data for the image. (Lee, 2006, p. 27) According to Nitz (2007, p. 12), surface coils are the components of the MR that gain SNR. SNR performs the action by tracing the origin of the signal. SNR can be substantially attained when the coils are made smaller. Nuclear spin can be sufficiently achieved when the MR machine has several small coils. These small coils, which are termed imaging matrices, can achieve quite a feat if they are arranged systematically. In installing the 3T, surface coils are attached to the patient’s body in order for SNR to be closer to the signal. These surface coils compose the imaging matrix whose primary function is to achieve SNR gain. The distance between the signal source and the coil determines the SNR gain. (Nitz, 2007, p. 12) A technique in the application of the coils is called parallel imaging wherein the coils perform the action of measuring the signal to gain SNR. This is used in an MRI to attain a shorter time in acquiring the image inside the body. It is advantageous to patients who are afraid in an MRI (Rombouts, Barkhof, & Scheltens, 2007, p. 26). Parallel imaging, which is termed as PAT, refers to the arrangement of surface coils, performed in such a way as to attain spatial information or signal. It measures the signal that can be attained in order to achieve the desired image. PAT is performed using several positions of the coils or matrices to achieve as much spatial information as possible. Other uses of parallel imaging include the following. To shorten the time of attaining an image with decreased SNR; To attain higher spatial resolution, but in doing this SNR is further reduced; To achieve lesser SAR in order to keep the measurement time at a controlled level. (Nitz, 2007, p. 34) Contrast It is widely accepted that the 3T MRI has more advantages than disadvantages. Because of the higher magnetic field, it has high contrast and resolution, which means the contrast is more enhanced, there is faster scanning details and processes. When it comes to contrast, the 3T already has it. This is more advantageous than the 1.5T. But a higher contrast requires a higher magnetic field. So, this has to be controlled. The government is doing its share in the control of MRI magnetic fields. The MR contrast can be safe with the use of Prohance. According to the website MRIC, Prohance is the safest contrast which is half of the dose. Siemens Medical Solutions USA, Inc. (2009) affirms that 3T contrast is safer. The specific absorption rate (SAR) or the amount of energy required to produce an image has been lowered due safety concerns. Hardware and software are available for this application. SAR is normally a property of the magnetic field, the frequency of the RF, and the patient’s position in the MRI machine. There are guidelines in the application of the coils for SAR functions. Before a user (hospital) will buy an MRI, the SAR is measured using calculations and measurement. The vendor will guide the buyer in the usage and application of the desired SAR. Government guidelines have to be followed in order to provide safety to the patient. (Nitz, 2007, p. 30) Siemens has recommended the hardware TrueForm which reduced this required time and also enhances safety on the part of the patient. (Siemens Medical Solutions USA, Inc., 2009) Conclusions/Recommendations From the data and information gathered in the literature, it can be said and concluded here that there are safety concerns when it comes to SNR, higher contrast and resolution because this means a higher magnetic field. The magnetic field in MR is the one doing the great job of imaging for a clearer diagnosing of diseases. To get a clearer picture, the magnetic field has to be increased or strengthened. This is the major concern. When it comes to increasing the electromagnetic field of the MRI, the government has been controlling it. Therefore, it is not advisable that hospitals translate to higher fields for a more desired contrast. The 3T MRI has the desired high contrast, achievable SNR and other properties for diagnostic imaging. The 3T MRI is very beneficial to detecting diseases because it provides doctors the various images of the body. Many diseases of the past that could not be easily detected are easily diagnosed using the MRI. Even in children, the MRI is now in use and effective because it provides faster acquisition period and fine quality image. Orthopedic doctors also recommend the 3T for its quality images of injuries of the bones and other parts of the body caused by accidents. (Harvey, 2011) Another important concern in the use and application of an MRI is the cost. According to Harvey (2011), an MRI can have a price of a million dollars for every Tesla which translates to $3 million for a 3T MRI. But a 3T MRI system already can provide a higher SNR with reduced measurement and acquisition time and higher scanning properties. If this is already achievable and has done many benefits to doctors and hospitals in their diagnostics and patient care, then why push for a higher field? Other major companies selling MRIs propose and highly recommend that 3T is preferable in this age of technology and globalization. References Harvey, D. (2011). 3T: it’s the way that you use it. Retrieved 22 September 2011 from: http://www.imagingeconomics.com/issues/articles/MI_2004-11_06.asp Jerrolds, J. & Keene, S. (2009). MRI safety at 3T versus 1.5T. The Internet Journal of World Health and Societal Politics. Retrieved 21 September 2011 from: http://www.koppdevelopment.com/articels/MRI%20Safety%20at%203T%20VS%201-5T.pdf Lee, V. S. (2006). Cardiovascular MRI: physical principles to practical protocols. United States of America: Lippincott Williams & Wilkins. Lombardi, M. & Milanesi, M. (2010). Heart and coronary arteries. In E Neri, M. Cosottini, & D. Caramella (Eds.), MR angiograpy of the body: technique and applications. United States of America: Springer. MRIC (n.d.). 3T MRIC is twice as strong as any other MRI unit. Retrieved 21 September 2011 from: http://www.3t-mri.net/2.html Nitz, W. R. (2007). Basic principles of MR. In V. Runge, W. Nitz, S. Schmeets, & S. Schoenberg (Eds.), Clinical 3T magnetic resonance. United States of America: Thieme Medical Publishers, Inc. Rombouts, A., Barkhof, F., & Scheltens, P. (2007). Clinical applications of functional brain MRI. Oxford; New York: Oxford University Press. Runge, V. M. & Case, R. S. (2007). Brain: screening. In V. Runge, W. Nitz, S. Schmeets, & S. Schoenberg (Eds.), Clinical 3T magnetic resonance. United States of America: Thieme Medical Publishers, Inc. Siemens Medical Solutions USA, Inc. (2009). Incorporation of 3T MRI into clinical routine. Retrieved from: http://www.medical.siemens.com/siemens/en_US/gg_mr_FBAs/files/brochures/3TWhitePaper.pdf Taouli, B. ( Hepatocellular Carcinoma: magnetic resonance imaging. In M. A. Hayat (Ed.), Methods of cancer diagnosis, therapy, and prognosis (volume 5 liver cancer). United States of America: Springer. Tesla Memorial Society of New York (1998). Tesla Biography: Nicola Tesla, the genius who lit the world. Retrieved 22 September 2011 from: http://www.teslasociety.com/biography.htm. Read More