Magnetic resonance imaging
Task 1 A): Describe the principle of magnetic resonances imagining:
Magnetic resonance imaging (MRI) is a non-invasive medical technique that diagnoses a patient as well as to monitor the treatment for a variety of conditions within the chest, abdomen and pelvis, also MRI can be used to safely monitor a baby in the whom. The Magnetic resonance imaging scanner uses strong magnetic fields to produce images of organs, bones, soft tissues and other internal body structures. MRI is used very frequently as there is none ionizing radiation and x-rays used in the process of MRI.
Nuclear spin: Nuclei are positively charged and spin on an axis, this creates a tiny magnetic field. Nuclei with an odd number of protons and/or neutrons have Spin. This dictates to us the theses Nuclei behave like small bar magnets. When nuclei with spin are placed in an external magnetic field (B0), the nuclear magnetic field can either be aligned with the external magnetic field or oppose the external magnetic field. This means that they have 2 orientations.
Precession: precession is often related to child’s spinning top. A spinning top does not stand vrtical for a long time, but wobbles, or precess. Regarding this the precession is cause by the involvment between the earths gravittional field and the spinning momnetum of the top. Nuclei aligned is an external magnetic field precess around the direction of the magnetic filed. The frequency of the precess is called the larmor frequency, the larmor freguency depends on the strenght of the magneic field.
Nuclear energy levels: with no external field, the nuclie have the same energy level. Where as, when there is an external field magnetic fied, the energy of the magnetic field are orientaited against the magnetic fields so there a 2 different energy levels.
Resonances, and how it is produced: Resonance is natural and charactrized by an oscilliating response over a narrow range of frequencies to the external input from energy. All resonant systems can transfer energy two or more storage modes. Eventually the resonance dies out due to slight energy loses that occur from cycle to cycle. Magnetic resonance happens when external energy is put in a nucear spin system near the larmor frequency. In MRI, the primary sources of energy input is from a rotting magnetic field created by a passing alternating current through a radiofrequency coil. The nuclear system absorbs the radio frequency energy by increasing the relative fraction of spin in higher energy state. Some of the energy is transferred coherently to other spins in sample, so sustaining the oscilliaion. The absorbed energy is dispersed by incoherent electromagnetic interaction with other spns or through molecula vibrations and collisons.
Relaxtion of hydrogen nuclie in different environments: the relaxtion rate for each proton nucleus depends of the environment around it. Relaxation rates for protons in water are fast. Relaxtion rates for protons in fat (brain tissue) are slow. Relaxation rates for protons in timours are intermediate, faster then for water and slower than for fat. The different signals form protons in different environments are analysed by a compture to generate the Magnetic resonance imaging.
Reference: Soilull moodle powerpoint
B) Outline the instrumentation needed to produce an MRI image:
Magnetic resonance imaging (MRI) is a type of scan that uses magnetic field and radio waves to produce images of the insides of the patients body. An MRI Is a large tube that contains powerful magnets. The use of the Electromagnet is to establish the B0 field to align the spin. In the electromagnets the graident cols are present, these gradient coils produce variations in the B0 in the X, Y, AND Z directions to make a locilazation of the recived data possible. Whithin the gradient coil is the is the radio frequency coil, the radio frequency coil is used to establish the B1 magnetic field needed to exite the spinning nuclie. It also detects the signal emitted from the spins within the object beinged imaged. There is a radio frequency amplifier that increases the power of the pulses. The anolog to digital convertr converts the recived anolog raw data into digital values. The MRI scan room is surrounded by a Radio frequency shield. A computer console, a display, and a film printer belonging to the MRI equipment.
Reference: https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mriTask 2): How do each of the following factors affect the signal intensity of MRI imaging:
Concentration of nucleus being monitored: The concentrations or density of protons can be imaged as it is the most direct tissue characterisitic that can be monitored and imaged. The proton content of the tissue determines, The density image the tissue magneitization , radio frequency intensity , and image bringhtness. The strong signals and bright apperance is due to the fact that the tissues have many protons in them. However if there is a tissue that does not have the right concentration of protons/molecules with hydrogen protons, there will not be a visible MRI image.
The environment of the nuclei: The MRI image becomes highly visible when the atoms such as protons have a strong connection to intensity of the MRI, the signal intensity in MRI of the environment of the environment of the nuclei relates o the atom such as prtons have a strong connection. This suggest to us that images of the brain will be very detailedand this suggest to us the doctors are able to identify any problems in appear In the MRI image.
Use of paramagnetic reagets to distinugish between different tissues: this is used as it produce a variation of pulse sequences which give very detailed images. The field strenght depends on the greater number of protons the greater radio signa emmited. A paramagnetic reagtent is added to a nmr sample that complexes with the molecules that are being tested and which means that a karge shift in the absoption frequencies ny Nmr are caused. This can help identify molecules.
Reference: https://mrimaster.com/technique%20SNR.htmlTask 3): Which scanning technique shoud be used?:
The cyclist has broke his arm: If the cyclist has broke his arm the scanning technique that should be used is the x-ray technique. An x-ray scanning technique will be used as it is mostly used in a hospital to produce an image of the bone to determine if the bone in the arm is broken. X-rays can penatrate through the body and they are used to depitc an image of a tissue or of the body structures. The x-rays leave an image of photographic paper. More dense areas in the body, like bone allow feweer x-rays to pass through and so they appear on x-ray images. With this you can tell which bones are broken or fractured.
right14097000Reference: http://www.dresan.com/images/break-banner.jpgThe cyclist has suffered brain damage: As the cycllist has obtained a brain injury the scanning technique that should be used is the Magnetic resonance imaging. This is used instead of xrays as the MRI scan show full detail of the brains functions aswell as the structure of the brain. It is very powerful as it produces a detailed and high quality image of the body and also take 360-degree images of the internal organs.
Reference: https://www.ncm-c.org/wp-content/uploads/2013/05/diagnostic-imaging-mri-scans.jpgIf there is a problem with the brain an image will show a contrast in colour and therefore showing where the propblem is , this is more sutiable than the x-ray scan.