Magnetic Resonance Imaging
History and Science Behind MRI: Open or Closed Case? Magnetic Resonance Imaging (MRI) has been called one of the most comprehensive and efficacious diagnostic imaging modalities in medical history. It became a viable clinical technique in 1982 and during its relatively short lifetime has become the primary imaging modality for investigations of the brain, spinal cord, spine, cancellous bone, and joints. It is widely used for the identification and staging of tumors, investigations of large blood vessels, and in pediatric studies. Cardiac MR, with its unique ability to provide simultaneous information about anatomy, function, and tissue character, has become a primary or complimentary modality in a wide range of pathologies, such as aortic
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disease, masses, congenital heart disease, ventricular function, and cardiomyopathies. Unique technical abilities are the driving force behind the rapid clinical acceptance of MRI. It is a completely noninvasive technique capable of producing images with soft tissue contrast seventy to eighty times greater than Computed Tomography (CT) without hospitalization or the use of ionizing radiation. In addition, MR systems can directly image in the coronal, sagittal, axial, or any oblique imaging plane without repositioning (Compunet). Felix Bloch was a theoretical physicist who, in 1946, proposed some very interesting properties for the particles, which make up the nucleus of an atom. Bloch, working at Stanford University, proposed that the protons inside the nucleus of any atom behave like tiny magnets. He mathematically described this magnetism by what are now called Bloch equations (Femano 4). Bloch's equations explain that tiny charged particles in the nucleus of an atom behave as though they spin on an imaginary axis like a top. This causes them to make a very small magnetic field. The connection between atomic particles and magnetic fields was very important to the future development of MRI (Femano 5). At about the same time, Edward Purcell measured an important physical phenomenon for which he coined the term "nuclear Magnetic absorption of energy in bulk materials". To put it simply, he showed that by passing the right type of energy through a material, the material would then respond by giving off energy of its own that he could measure. This is the principle of resonance, which is essential for MRI to work. Resonance is a physical principle that allows the efficient transfer of energy from one object to another, causing the receiving object to vibrate at the same frequency as the sender. Bloch and Purcell shared the Nobel Prize in Physics in 1952 for their significant contributions to the betterment of mankind (Femano 5). Dr. Raymond Damadian, is credited as being the inventor of the first MRI machine, who received the National Medal of Technology and was inducted into the National Inventors Hall of Fame for his pioneering work. In 1972, Dr. Damadian filed for and obtained a patent for scanning the human body with magnetic resonance imaging and formed his own company, FONAR. The first-ever MRI machine, dubbed "Indomitable," is now in the Smithsonian, and has taken its place alongside other notable "firsts" (Kelley 1). Today, the MRI is considered an indispensable tool but acceptance of the technology did not come easily. Even after Dr. Damadian performed the first human body scan in 1977, his accomplishments was greeted with skepticism and dismissed by his peers. Once the potential to detect cancerous tumors was accepted, however, Dr. Damidian had to fight off giant companies such as Hitachi and General Electric to protect his patented technology. Hitachi settled out of court, but the case against GE went to trail in 1995. In a "David vs. Goliath" lawsuit, FONAR won one of the largest patent settlements on record, $128.7 million (Kelley 2). Basically, radio frequency energy is sent through the body of a patient, which is placed inside a strong magnet. The result is the patient's body will emit detectable signals containing information about the body's composition in response to the radio frequency energy source. Many of these signals must be collected in order to form a single MR image. Many cross-sectional images may be generated and they may be generated in any plane. The digital images may first be viewed on the operator's system console and then they can be printed on film (Femano 20). MRI Technology has become a vital diagnostic tool, and Dr. Damadian believes that it will become an equally important tool for treatment. The initial technology has evolved, with the advent of "open" machines, the standing or weight bearing models, to an MRI operating room so the entire surgical team operates within it. (Kelley 2). Medicine consists of essentially two parts: diagnosis and treatment. The diagnostic part of medicine has gone through a revolution in the last few decades, primarily because of the improvements in computer technology, which have culminated in magnetic resonance imaging. MRI has replaced very invasive and less diagnostic methods such as pneumoencephalography, myelography, and nuclear medicine brain scans. Due to its highly accurate diagnostic ability combined with its minimal risks and noninvasive nature, the use of MRI has skyrocketed. The term MRI has come into common usage even within the non-medical population. For example, over the course of a year, the sports section of most newspapers has numerous articles describing the MRI findings of local or national sports figures. MRI is able to diagnose neurological and musculoskeletal pathology earlier and more accurately than any other modality. MRI is beginning to approach the "tricorder" of Dr. McCoy in the popular television series Star Trek (Rothschild 3). As use of MRI has proliferated, significant limitations have appeared: Claustrophobia and anxiety related reactions, restrictions on patient size and weight, and lack of access to the patient undergoing the examination have surfaced as problems facing traditional "tube-like" closed MRI scanners. However, most radiologists believed that only traditional closed MRI scanners held promise for the future. The simple descriptive term "open" caught on quickly with patients and referring doctors. Presently though, many of the same radiologists who previously shunned "open" technology have become converted, a fact reflected in the soaring popularity of open magnets. MRI technology has advanced at a whirlwind pace, allowing the once unthinkable to become reality. Improved computer hardware, software, gradients, and magnets have dramatically advanced the performance and functionality of all MRI systems. Today, lower field strength open magnets can readily out perform the higher field "closed" magnets of just a few years ago (Rothschild 3). Open MRI has also enabled the examination of other types of patients unable to undergo conventional closed MRI. Large patients and patients with wide shoulders who either exceed table weight limits or simply do not fit into the tube-type gantry can usually fit into an open MRI with ease. The open architecture and quieter operation allow direct visual and auditory patient monitoring. Electronic and life support equipment can be brought much closer to the patient, because magnetic fields are generally much lower in open magnets (Rothschild 4). Higher field strength scanners with a 1 - 1.5 Tesla (measurement of magnetic force) provide high resolutions, that is, clearer, easier to read scans. Open scanners usually have about a .23 Tesla. The higher the field strength, the more powerful and faster the scanner. As the field strength increases, the signal or ability to receive body images from the patient increases and results in a better quality image. MRI scanners scan the body in slices. On a high field or closed MRI system, the slice can be thinner, improving the image the physician uses to diagnose the problem. High field MRI systems also take less time due to the higher magnetic field strength. High field scans can be one and a half to two times faster than an "open" scan. As the scan time lengthens, the patient is more prone to movement, which reduces image quality. High field scanners also provide the most advanced imaging techniques, some of which cannot be performed on an "open" scanner. There has been an increase in open MRI use due to the misunderstanding that closed scanners can be more claustrophobic for the patient. This misconception is, perhaps, caused by the design of each type of scanner. Traditional high field scanners are currently designed to increase patient comfort as well as reduce the anxiety that may occur with MRI patients. The newer scanners are designed with a substantially shorter bore or tube than the older scanners. This allows for the patient's head to be outside the bore of the magnet for a number of scans. The bore of the magnet is flared at the ends, so if a patient needs to be inside the scanner, the "closed in" feeling is reduced because the patient's head is towards a flared end. In addition, the bore has a larger width than that of the older scanners, which provides more room around the patient while inside the scanner. Most MRI scanners have been designed with superior ventilation and lighting systems, allowing more air and light to circulate while scanning. Sometimes a patient can request changes in the ventilation and lighting if needed. Many MRI facilities provide music for patients to listen to during their scan for relaxation purposes. In addition to the physical structure of the scanner reducing the anxiety of the patient, MRI technologists and support staff are experienced in dealing with patients who may be nervous. Most staff can comfort and relax patients, talk them through the scan and, if needed, sit with the patient and hold their hand. "Open," low field scanners may be more appropriate for some patients, such as true claustrophobics, those with a larger body or who have conditions that may result in painful positioning and those involved in movement studies. The patient should be made aware of the differences in quality and time and the potential that an additional scan might be required. High field scans are indicated for central nervous system and vascular studies - particularly contrast enhanced MRA (Magnetic Resonance Angiography) studies, abdominal work that requires the patient to hold their breath, fat saturation techniques, certain cancer studies and any study that requires high resolution. If these studies are performed on a low field scanner, it is possible that the scan would have to be repeated on a high field scanner, resulting in patient inconvenience as well as billing for a repeated scan (Clark). MRI, like no other medical test, has become closely linked with the psychological response it elicits. In many patients, the MRI procedure-despite its technological sophistication and efficacy-elicits fears and anxieties that are primitive in origin, such as the fight-or-flight response. Although usually associated with claustrophobia, MRI can trigger or exacerbate many psychological conditions. Claustrophobia, "the dread of closed places", is the popular psychological term associated with MRI, but what actually occurs is much more complex and differs from patient to patient. What has been called claustrophobia when describing the patient response to MRI may instead be a class of anxiety responses cause by the MRI procedure rather than a specific phobia of its own. Psychological issues that have become commonplace with the use of traditional closed MRI units must also be considered with the use of short-bore and open MRI scanners. Short-bore units, in which the cavity is shallower, allow the patient to be somewhat less enclosed but still maintain the closed cavity design and potentially all or most of the psychological limitations of the standard tube MRI. The open units, which by their very design and name seek to avoid claustrophobia, may still precipitate psychological issues similar to those elicited during closed MRI but often for different reasons. Quieter, less restrictive, and more patient friendly, these units offer obvious psychological benefits. Unfortunately, open scans generally take more time to complete, and the patient is thus asked to lie motionless for a longer period than is generally required with traditional scanner (Rothschild 5). The incidence of persistent claustrophobia resulting from MRI procedures was reported as early as 1988. As recently as 1996, this incidence was echoed by the findings that 92% of patients who could not complete MRI experienced panic attacks and that most (83%) also reported having panic attacks one month after the MRI. The importance of these statistics lies in the fact that, in essence, the testing for a medical condition has become the cause of a psychological condition that can be persistent and require treatment in its own right (Rothschild 10). All individuals, including patients, volunteer subjects, visitors, MR health care providers, and custodial workers, must be thoroughly screened by qualified personnel before being exposed to the MRI environment. Conducting a careful screening procedure is crucial to ensure the safety of anyone that enters the area of the MR system (MRIsafety.com). A patient about to be placed in an unconventional habitat relies on the technologist to provide accurate information regarding the safety and trustworthiness of the MRI scanner.
No other imaging modality has ever required such an astute ability to factor out those circumstances which would, when exposed to strong magnetic fields, have the potential to cause harm to the patient (Woodard 1). Ferromagnetic objects will experience a rotational force or torque, upon entering the magnetic field. Therefore, they will attempt to align with the magnetic field. Once in the bore of the magnet, no additional force is experienced. When the same ferromagnetic object is being removed from the magnetic field, it will try to regain its original orientation, therefore experiencing torque once again. It is this force that may cause internal damage to tissues. Although no known biological hazards exist with MRI, there is a substantial risk associated with large magnetic fields and their ability to forcibly attract ferromagnetic and some paramagnetic materials. This causes loose metal objects to become flying projectiles, which may impact with the patient and cause serious, life-threatening …show more content…
injuries. Neurological aneurysm clips have been found to be magnetic and since they are attached to critical tissues, MR exams of patients who have these implants are contraindicated. Care must also be taken to ensure that non-magnetic IV poles, step stools, and transportation vehicles are used. Access to the magnet room must be controlled at all times. An additional risk associated with strong external magnetic fields is the effect it may have on magnetically, electronically or mechanically activated devices, such as cardiac pacemakers and neurostimulators.
Cardiac pacers have a reed switch that can be activated by an external magnet. Movement of the pacer closer to the magnetic field can cause malfunction and render the pacer inoperable. Patients with implanted pacers should be excluded from the magnet room (Woodard 2). Most instances associated with MR-related injuries have been a direct result of deficiencies in screening methods. Unfortunately, not all MR users perform a rigorous screening procedure and there tends to be a lack of agreement on what constitutes an appropriate or necessary protocol that will ensure the safety of individuals and patients in the MR setting
(MRIsafety.com). Open or Closed, Magnetic Resonance Imaging (MRI) is a safe, simple and painless way to look inside your body without using X-Rays. Instead, it uses a large magnet, radio waves and a computer to scan your body and produce detailed pictures of the inside of the body that cannot be seen on conventional X-rays. MRI is useful for imaging most body parts, including the brain, spine, joints, and extremities, and can provide very early detection of many conditions. Although much advancement has been made in the area of magnetic resonance, MRI technology is still relatively new. Research concerning magnetic resonance imaging is abundant and covers a range of both clinical and non-clinical applications. As the quality of MR imaging improves, the technology is becoming the most widely used form of medical imaging available.
disease, masses, congenital heart disease, ventricular function, and cardiomyopathies. Unique technical abilities are the driving force behind the rapid clinical acceptance of MRI. It is a completely noninvasive technique capable of producing images with soft tissue contrast seventy to eighty times greater than Computed Tomography (CT) without hospitalization or the use of ionizing radiation. In addition, MR systems can directly image in the coronal, sagittal, axial, or any oblique imaging plane without repositioning (Compunet). Felix Bloch was a theoretical physicist who, in 1946, proposed some very interesting properties for the particles, which make up the nucleus of an atom. Bloch, working at Stanford University, proposed that the protons inside the nucleus of any atom behave like tiny magnets. He mathematically described this magnetism by what are now called Bloch equations (Femano 4). Bloch's equations explain that tiny charged particles in the nucleus of an atom behave as though they spin on an imaginary axis like a top. This causes them to make a very small magnetic field. The connection between atomic particles and magnetic fields was very important to the future development of MRI (Femano 5). At about the same time, Edward Purcell measured an important physical phenomenon for which he coined the term "nuclear Magnetic absorption of energy in bulk materials". To put it simply, he showed that by passing the right type of energy through a material, the material would then respond by giving off energy of its own that he could measure. This is the principle of resonance, which is essential for MRI to work. Resonance is a physical principle that allows the efficient transfer of energy from one object to another, causing the receiving object to vibrate at the same frequency as the sender. Bloch and Purcell shared the Nobel Prize in Physics in 1952 for their significant contributions to the betterment of mankind (Femano 5). Dr. Raymond Damadian, is credited as being the inventor of the first MRI machine, who received the National Medal of Technology and was inducted into the National Inventors Hall of Fame for his pioneering work. In 1972, Dr. Damadian filed for and obtained a patent for scanning the human body with magnetic resonance imaging and formed his own company, FONAR. The first-ever MRI machine, dubbed "Indomitable," is now in the Smithsonian, and has taken its place alongside other notable "firsts" (Kelley 1). Today, the MRI is considered an indispensable tool but acceptance of the technology did not come easily. Even after Dr. Damadian performed the first human body scan in 1977, his accomplishments was greeted with skepticism and dismissed by his peers. Once the potential to detect cancerous tumors was accepted, however, Dr. Damidian had to fight off giant companies such as Hitachi and General Electric to protect his patented technology. Hitachi settled out of court, but the case against GE went to trail in 1995. In a "David vs. Goliath" lawsuit, FONAR won one of the largest patent settlements on record, $128.7 million (Kelley 2). Basically, radio frequency energy is sent through the body of a patient, which is placed inside a strong magnet. The result is the patient's body will emit detectable signals containing information about the body's composition in response to the radio frequency energy source. Many of these signals must be collected in order to form a single MR image. Many cross-sectional images may be generated and they may be generated in any plane. The digital images may first be viewed on the operator's system console and then they can be printed on film (Femano 20). MRI Technology has become a vital diagnostic tool, and Dr. Damadian believes that it will become an equally important tool for treatment. The initial technology has evolved, with the advent of "open" machines, the standing or weight bearing models, to an MRI operating room so the entire surgical team operates within it. (Kelley 2). Medicine consists of essentially two parts: diagnosis and treatment. The diagnostic part of medicine has gone through a revolution in the last few decades, primarily because of the improvements in computer technology, which have culminated in magnetic resonance imaging. MRI has replaced very invasive and less diagnostic methods such as pneumoencephalography, myelography, and nuclear medicine brain scans. Due to its highly accurate diagnostic ability combined with its minimal risks and noninvasive nature, the use of MRI has skyrocketed. The term MRI has come into common usage even within the non-medical population. For example, over the course of a year, the sports section of most newspapers has numerous articles describing the MRI findings of local or national sports figures. MRI is able to diagnose neurological and musculoskeletal pathology earlier and more accurately than any other modality. MRI is beginning to approach the "tricorder" of Dr. McCoy in the popular television series Star Trek (Rothschild 3). As use of MRI has proliferated, significant limitations have appeared: Claustrophobia and anxiety related reactions, restrictions on patient size and weight, and lack of access to the patient undergoing the examination have surfaced as problems facing traditional "tube-like" closed MRI scanners. However, most radiologists believed that only traditional closed MRI scanners held promise for the future. The simple descriptive term "open" caught on quickly with patients and referring doctors. Presently though, many of the same radiologists who previously shunned "open" technology have become converted, a fact reflected in the soaring popularity of open magnets. MRI technology has advanced at a whirlwind pace, allowing the once unthinkable to become reality. Improved computer hardware, software, gradients, and magnets have dramatically advanced the performance and functionality of all MRI systems. Today, lower field strength open magnets can readily out perform the higher field "closed" magnets of just a few years ago (Rothschild 3). Open MRI has also enabled the examination of other types of patients unable to undergo conventional closed MRI. Large patients and patients with wide shoulders who either exceed table weight limits or simply do not fit into the tube-type gantry can usually fit into an open MRI with ease. The open architecture and quieter operation allow direct visual and auditory patient monitoring. Electronic and life support equipment can be brought much closer to the patient, because magnetic fields are generally much lower in open magnets (Rothschild 4). Higher field strength scanners with a 1 - 1.5 Tesla (measurement of magnetic force) provide high resolutions, that is, clearer, easier to read scans. Open scanners usually have about a .23 Tesla. The higher the field strength, the more powerful and faster the scanner. As the field strength increases, the signal or ability to receive body images from the patient increases and results in a better quality image. MRI scanners scan the body in slices. On a high field or closed MRI system, the slice can be thinner, improving the image the physician uses to diagnose the problem. High field MRI systems also take less time due to the higher magnetic field strength. High field scans can be one and a half to two times faster than an "open" scan. As the scan time lengthens, the patient is more prone to movement, which reduces image quality. High field scanners also provide the most advanced imaging techniques, some of which cannot be performed on an "open" scanner. There has been an increase in open MRI use due to the misunderstanding that closed scanners can be more claustrophobic for the patient. This misconception is, perhaps, caused by the design of each type of scanner. Traditional high field scanners are currently designed to increase patient comfort as well as reduce the anxiety that may occur with MRI patients. The newer scanners are designed with a substantially shorter bore or tube than the older scanners. This allows for the patient's head to be outside the bore of the magnet for a number of scans. The bore of the magnet is flared at the ends, so if a patient needs to be inside the scanner, the "closed in" feeling is reduced because the patient's head is towards a flared end. In addition, the bore has a larger width than that of the older scanners, which provides more room around the patient while inside the scanner. Most MRI scanners have been designed with superior ventilation and lighting systems, allowing more air and light to circulate while scanning. Sometimes a patient can request changes in the ventilation and lighting if needed. Many MRI facilities provide music for patients to listen to during their scan for relaxation purposes. In addition to the physical structure of the scanner reducing the anxiety of the patient, MRI technologists and support staff are experienced in dealing with patients who may be nervous. Most staff can comfort and relax patients, talk them through the scan and, if needed, sit with the patient and hold their hand. "Open," low field scanners may be more appropriate for some patients, such as true claustrophobics, those with a larger body or who have conditions that may result in painful positioning and those involved in movement studies. The patient should be made aware of the differences in quality and time and the potential that an additional scan might be required. High field scans are indicated for central nervous system and vascular studies - particularly contrast enhanced MRA (Magnetic Resonance Angiography) studies, abdominal work that requires the patient to hold their breath, fat saturation techniques, certain cancer studies and any study that requires high resolution. If these studies are performed on a low field scanner, it is possible that the scan would have to be repeated on a high field scanner, resulting in patient inconvenience as well as billing for a repeated scan (Clark). MRI, like no other medical test, has become closely linked with the psychological response it elicits. In many patients, the MRI procedure-despite its technological sophistication and efficacy-elicits fears and anxieties that are primitive in origin, such as the fight-or-flight response. Although usually associated with claustrophobia, MRI can trigger or exacerbate many psychological conditions. Claustrophobia, "the dread of closed places", is the popular psychological term associated with MRI, but what actually occurs is much more complex and differs from patient to patient. What has been called claustrophobia when describing the patient response to MRI may instead be a class of anxiety responses cause by the MRI procedure rather than a specific phobia of its own. Psychological issues that have become commonplace with the use of traditional closed MRI units must also be considered with the use of short-bore and open MRI scanners. Short-bore units, in which the cavity is shallower, allow the patient to be somewhat less enclosed but still maintain the closed cavity design and potentially all or most of the psychological limitations of the standard tube MRI. The open units, which by their very design and name seek to avoid claustrophobia, may still precipitate psychological issues similar to those elicited during closed MRI but often for different reasons. Quieter, less restrictive, and more patient friendly, these units offer obvious psychological benefits. Unfortunately, open scans generally take more time to complete, and the patient is thus asked to lie motionless for a longer period than is generally required with traditional scanner (Rothschild 5). The incidence of persistent claustrophobia resulting from MRI procedures was reported as early as 1988. As recently as 1996, this incidence was echoed by the findings that 92% of patients who could not complete MRI experienced panic attacks and that most (83%) also reported having panic attacks one month after the MRI. The importance of these statistics lies in the fact that, in essence, the testing for a medical condition has become the cause of a psychological condition that can be persistent and require treatment in its own right (Rothschild 10). All individuals, including patients, volunteer subjects, visitors, MR health care providers, and custodial workers, must be thoroughly screened by qualified personnel before being exposed to the MRI environment. Conducting a careful screening procedure is crucial to ensure the safety of anyone that enters the area of the MR system (MRIsafety.com). A patient about to be placed in an unconventional habitat relies on the technologist to provide accurate information regarding the safety and trustworthiness of the MRI scanner.
No other imaging modality has ever required such an astute ability to factor out those circumstances which would, when exposed to strong magnetic fields, have the potential to cause harm to the patient (Woodard 1). Ferromagnetic objects will experience a rotational force or torque, upon entering the magnetic field. Therefore, they will attempt to align with the magnetic field. Once in the bore of the magnet, no additional force is experienced. When the same ferromagnetic object is being removed from the magnetic field, it will try to regain its original orientation, therefore experiencing torque once again. It is this force that may cause internal damage to tissues. Although no known biological hazards exist with MRI, there is a substantial risk associated with large magnetic fields and their ability to forcibly attract ferromagnetic and some paramagnetic materials. This causes loose metal objects to become flying projectiles, which may impact with the patient and cause serious, life-threatening …show more content…
injuries. Neurological aneurysm clips have been found to be magnetic and since they are attached to critical tissues, MR exams of patients who have these implants are contraindicated. Care must also be taken to ensure that non-magnetic IV poles, step stools, and transportation vehicles are used. Access to the magnet room must be controlled at all times. An additional risk associated with strong external magnetic fields is the effect it may have on magnetically, electronically or mechanically activated devices, such as cardiac pacemakers and neurostimulators.
Cardiac pacers have a reed switch that can be activated by an external magnet. Movement of the pacer closer to the magnetic field can cause malfunction and render the pacer inoperable. Patients with implanted pacers should be excluded from the magnet room (Woodard 2). Most instances associated with MR-related injuries have been a direct result of deficiencies in screening methods. Unfortunately, not all MR users perform a rigorous screening procedure and there tends to be a lack of agreement on what constitutes an appropriate or necessary protocol that will ensure the safety of individuals and patients in the MR setting
(MRIsafety.com). Open or Closed, Magnetic Resonance Imaging (MRI) is a safe, simple and painless way to look inside your body without using X-Rays. Instead, it uses a large magnet, radio waves and a computer to scan your body and produce detailed pictures of the inside of the body that cannot be seen on conventional X-rays. MRI is useful for imaging most body parts, including the brain, spine, joints, and extremities, and can provide very early detection of many conditions. Although much advancement has been made in the area of magnetic resonance, MRI technology is still relatively new. Research concerning magnetic resonance imaging is abundant and covers a range of both clinical and non-clinical applications. As the quality of MR imaging improves, the technology is becoming the most widely used form of medical imaging available.