MRI Scanning Equipment (Term Paper Sample)

MRI Scanner
Student’s Name
Medicine and Health
Date
MRI Scanning Equipment
Introduction
MRI (magnetic resonance imaging) or MRT (magnetic resonance tomography) and NMRI (nuclear magnetic resonance imaging) alternatively in other settings, is radiological medical imaging technique. Through the utilization of radio waves and magnetic fields, MRI scanners form images of the anatomy of the body in depiction of illnesses or health CITATION DPr08 \p 139 \l 1033 (D. Price, 2008, p. 139). Due to its protection of the body to ionizing radiation, MRI technique is popular in many hospitals for medical diagnosis. In addition, the MRI scanner is used for medical follow up practices, medical prognosis, and staging of disease. A part of the revolutionary medical and technological innovations and invention of the 1980s, MRI scanners innovated the world of medical imaging all over the globe. Paul C. Lauterbur is accredited with the invention of the MRI CITATION DPr08 \p 139 \l 1033 (D. Price, 2008, p. 139) although the idea initially originated from Felix Bloch in the 1940s. In March of 1973, Lauterbur published his theory behind the MRI. Throughout the years since the invention and use of the MRI, numerous medical complications have been diagnosed and rectified CITATION Hol00 \l 1033 (Hollingworth W, CJ Todd, MI Bell, AK Dixon, 2000). In addition the MRI scanner has abundant applications with an approximated 25,000 MRI scanners used in hospitals around the globe. During the initial development of the MRI it was referred to as Nuclear Magnetic Resonance, however in light of appeasing the public inventors changed the name to MRI (Magnetic resonance imaging). MRI scanners have taken enormous strides since the first MRI scanner was built in the early 1980s with increased applications like functional imaging, MR Angiography, and diffusion scanning CITATION Lar09 \p 45 \l 1033 (Hanson, 2009, p. 45). In addition, MRI scanning hardware and software has become faster and more efficient. The use of MRI is highly popular due to its excellent contrast resolution, which forms its principle advantage of x-rays, which were the popular methods of imaging prior to the development of MRI. CT scans and x-rays bear several disadvantages to the MRI scans. One particular disadvantage is the inability of CT scans and x-rays to make images in diverse planes. On the other hand, every imaginable plane can be used to reflect MRI images making MRI scans applicable in every particular situation and location CITATION Hol00 \p 30 \l 1033 (Hollingworth W, CJ Todd, MI Bell, AK Dixon, 2000, p. 30). In addition, with the MRI exceptional contrast resolution detection of minute differences in soft tissues is possible unlike when using x-rays or CT images CITATION Bli04 \l 1033 (Blink, 2004). Consequently, many chronic afflictions like brain cancer, cerebrovascular disease, radio surgery, dementia, and other neurological cancers are detected through MRI scanners. As such, the efficiency of the MRI cannot be understated. However, despite the evident success and efficacy of the MRI scanners, they are expensive and susceptible to over diagnosis CITATION Hol00 \p 32 \l 1033 (Hollingworth W, CJ Todd, MI Bell, AK Dixon, 2000, p. 32). In addition, although MRI is considered generally safe there have been cases of harmful consequence of using the scanner. For example, any individual with metal implants is susceptible to wrong diagnosis. This paper will seek to explore the dynamics of MRI scan equipment particularly the competent and modern Signa HDXT of GE 1.5 Tesia MRI scanner.
Component Parts of MRI Scanner
An MRI scanner is a complex machine with various components that contribute to the ultimate efficiency of the machine. This section will evaluate parts of the previously mentioned Signa HDXT of GE 1.5 Tesia MRI scanner. Most of MRI scanners including the GE tesia design are composed of mainly five sections. The superconducting magnet system, the computer system, the gradient system, and the RF (radio frequency) coil system. As such, this section will evaluate each section characteristic functional features and their influence on the efficiency of the machine as a whole CITATION AAm06 \l 1033 (A. Amaro and C. Barker, 2006).
An MRI Scanner
Magnet System
Generally, MRI scanners have utilized magnet systems, although modern models use superconducting magnet systems, previous designs utilized simply a magnet system. A material magnetized to ensure retention of magnetic field under all circumstance, in such scanners the magnetic field strength is fairly low between 0.064T to 0.3 T (T= unit for magnetic field strength). Example of scanners exhibiting such low magnetic fields is the first open MRI scanner, Access 0.064 Tesia scanner from Toshiba. Scanners developed using such magnetic systems are inexpensive, have no cryogen and save power. However, they are bulky, have hampered field strength, and lack satiate possibility CITATION Bli04 \l 1033 (Blink, 2004). Other scanners use resistive magnets. Such magnets are huge and magnetization is through electric current that runs through loops of wire. Scanners that utilize such magnets are susceptible to heat and require constant cooling. In addition, they require high power range to function and have a field strength that does not have a large capacity CITATION Lar09 \p 45 \l 1033 (Hanson, 2009, p. 45). However, they have a few advantages in that they require low capital, are not heavy, and switching off is easy.
Superconducting magnet systems
Our model of interest and other modern scanners utilize the ultra new superconducting magnets. Like the resistive scanners, magnetization is through electric current running through a disk of wires. As such, this magnetic system is susceptible to heat like the previous system, consequently liquid helium surrounds the wires to create a cooling effect and thus reduce the wire’s electric resistance CITATION Bli04 \p 8 \l 1033 (Blink, 2004, p. 8). The previous magnetic systems used water to instill a cooling effect; this model however requires a much more efficient coolant because the wire’s resistance subsides at temperatures as low as -269˚C equivalent to 4 Kelvin. The suitability of superconducting magnetic systems allow for MRI scanners with up to 12 Tesia magnetic field strength. Normal clinically approved MRI scanners like the Signa HDXT we are evaluating use magnets with 1.5 magnetic field strengths CITATION Bli04 \p 8 \l 1033 (Blink, 2004, p. 8).
The diagram below illustrates a scanner with superconducting magnetic systems, the helium cooling system, the thermal radiation shields and subsequent vacuum vessels.
RF Coil System
This is the second component of the MRI scanner. RF coils are an absolute necessity for the productive of quality images. The RF coils are mediums that transmit and receive RF (radiofrequency) signals in MRI (magnetic resonance imaging). As such, they are necessary for the above-mentioned functions of receiving and transmission CITATION Hue09 \p 31 \l 1033 (Huettel, 2009, p. 31). Signa HDXT scanner like all modern scanners is able to capture holistic images of the body using a suitable and effective range of radiofrequency coils. Surface coils and volume coils are the two particular coils that in use in current scanners today. Volume coil like the one illustrated below are mainly used for receiving signals only. They have a saddle shaped design that has either the knee (receive only) and head (receive/transmit) coil CITATION Hue09 \p 31 \l 1033 (Huettel, 2009, p. 31).
The surface coils have a particularly different feature to the volume coils. As implied by the name the surface coils are utilized in specific locations. The area under examination determines where the surface coils are placed. The surface coils are very efficient; they have the capacity to illustrate essentially high-resolution images CITATION Hue09 \p 31 \l 1033 (Huettel, 2009, p. 31). However, depth penetration and image retention after moving from the area under scanning is low.
Gradient System
Another necessity for an impeccable MRI scanner is the gradient system that consists of the gradient coils. Gradients are located inside the bore of an MRI scanner; they are formed through loops of wires in a cylindrical shell CITATION Cal94 \p 45 \l 1033 (Callaghan, 1994, p. 45). A minor magnetic field is devised whenever a current goes through. As the variations in magnetic field created by the gradients alter the main magnetic fields resulting in magnetic field control depending on the position. Use of the coils is diversified but they mainly used in the main magnetic field (Bo) to effect variations deliberately CITATION Hil10 \p 226 \l 1033 (Hildalgo-Tobon, 2010, p. 226). Phase encoding, frequency encoding, and localization of images are enabled by the variations made possible by gradient coils. In addition, they are useful in the reduction of heat and increasing efficiency of the machine by inducing low resistance. Maxwell coins are types of gradient coils included in the gradient system. The Maxwell coils produce linear gradient as they placed 1.73 time of their radius and consequently the gradient is produced by current flowing in the opposite sense of both of the coils. Hugely significant modern applications of the MRI scanner mentioned previously like MR angiography and Perfusion imaging are possible to the gradient field created by gradient coils in the gradient system CITATION Hil10 \p 230 \l 1033 (Hildalgo-Tobon, 2010, p. 230)
Gradient coil
Computer System
Any particular scanner requires a viable computer system, a system that will form a complete unit when complemented with the RF coils, gradient system, and magnetic system. A digital computer performs several vital functions to ensure production and display of an image. The computer controls all the sequen...