Magnetic Resonance Imaging (MRI)


Magnetic resonance imaging (MRI) An important method of looking inside the human body without surgery.

Magnetic resonance imaging (MRI)

  • Development of MRI techniques: Its basic technologies were developed in the early 1970s.
    • In the latter part of the decade, Paul Lauterbur and Peter Mansfield Made significant improvements, allowing it to be widely adopted for medical purposes.
    • for these efforts He was awarded the Nobel Prize in Medicine in the year 2003.
  • Introduction: Use of MRI inside the body To obtain images of soft tissues is done. 'Soft tissue' that tissue Which has not become hard due to calcification.
    • this one Non-invasive diagnostic procedure Which is widely used in the brain, cardiovascular system, spinal cord and joints, various muscles, liver, Used to image arteries etc. is done.
  • Use: It is used to treat cancer including 'prostate' and 'rectal cancer' Observation and treatment of some cancers And it is important for tracking neurological conditions including Alzheimer's, dementia, epilepsy and stroke.
    • The researchers MRI scan to look for changes in blood flow have used, allowing them Estimation of fluctuations in brain neuron activities Permission is granted to install. This application of technology Functional MRI (fMRI) is referred to as.

Working of MRI

  • Hydrogen Atom Imaging: MRI process of the body The image of any part of the body is produced by using hydrogen atoms in some part. Is.
    • A hydrogen atom is just a proton around which an electron It happens. all these The atoms are spinning, whose axes point in random directions. Are towards.
    • Hydrogen atoms are abundant in fat and water. Which are present almost throughout the body.
  • Components of MRI Machine: An MRI machine has four essential components.
    • Bore: the machine itself 'Giant Donut' Looks like. The person whose body is to be scanned is brought inside the 'hole' made in the centre, which is 'Bore' It is said.
      • A powerful inside 'doughnut' 'Superconducting' magnet is, whose function is to create a circular motion around the body Powerful and stable magnetic field To generate. Once the body part to be scanned is in the center of the 'bore', the magnetic field is activated.
    • Magnetic Moment: Each hydrogen atom has a strong magnetic moment, which means that In the presence of a magnetic field, the spin of an atom The axis will correspond to the direction of the field.
      • due to this About half the hydrogen atoms within the target area are aligned in one direction while the other half aligned in the opposite direction Are there.
      • This alignment is almost perfect, with only a few of the millions of atoms remaining misaligned, oriented in one of two directions. A small number of “extra” atoms is constructed.
    • Radiofrequency pulse and nuclear stimulation: a device, which Emits 'radiofrequency pulses' at the bottom of the scanner Is.
      • When the pulse is 'on', only Only a small number of 'extra' atoms absorb the radiation and are excited it occurs.
      • When the pulse 'stops', these atoms absorbed energy emitted do and your ground state, lowest energy state Come back in.
      • The frequency of the pulse needs to be adjusted to absorb 'extra' atoms. 'Larmor frequency It is said. it worths Depend on magnetic field strength and tissue type Does, in which atoms are present.
    • Detector: a detector, Receives emissions and converts them into signals, which a computer is sent to that part of the body To produce two- or three-dimensional images Uses them.

Benefits of MRI

  • Gradual Magnetic Field for Focused Imaging: After activation of the primary strong magnetic field, the MRI machine Three additional magnets are attached, which generate small magnetic fields.
    • these areas compared to the main area About 80 or more are debilitated for some reason. One of these supporting areas There are also gradient zones, which means they are not uniform.
    • They Correlates with key areas in the targeted area of ​​the scan, emphasizing specific areas for detailed imaging Are there.
  • Precise scanning with gradient magnet sequences.: By selectively activating and deactivating gradient magnets in predetermined sequences, the MRI machine can measure up to a few millimeters Can scan narrow sections Is.
    • these sequences It can also be coordinated to scan different areas of the person's body without the need for movement within the bore.
  • Comprehensive Anatomical Imaging Capability: Because of the construction of the machine and the arrangement of magnets within it, an MRI scan can be obtained from several useful angles. body images effectively and if necessary, Can capture extremely fine detail Is.
  • Tissue Differentiation: When the “extra” atoms release the absorbed energy to return to the lower energy state, this process occurs over a period of time, called T1 relaxation time is referred to as.
    • The hydrogen atoms in water are at the base of those tissues.r would display different T1 values in which they live. MRI machines to show different tissues in different shades of gray advantage of this discrepancy Picks up.
    • Additionally, medical individuals 'contrast agent' can inject (usually a gadolinium-based compound), causing certain tissues T1 time decreases and MRI scan Their visibility increases.
  • Safety of MRI scans and magnetic field effects: Extensive research has explored the effects of strong magnetic fields on the human body.
    • MRI scan is considered safe because After the scan is finished the magnetic field ends and the atoms within the scanned area Return to their normal state without any permanent effect.
    • No evidence of long-term harm associated with MRI scans Not there.

harm from MRI

  • Low: Due to the strong magnetic fields used in MRI scans, implanted metal objects such as Individuals with medical implants such as a pacemaker or pacemaker May be ineligible for this process.
    • Moreover, even your Even keeping a credit card in your pocket can cause the magnetic strip of the MRI to be erased. Can.
  • Heavy Cost: MRI machines incur significant expense, ranging from several lakhs to a few crores depending on factors such as magnetic field strength and imaging quality specifications.
    • These costs are passed on to patients by the clinical facilities. Depending on the diagnostic requirements, individual scans can often cost more than Rs 10,000, which in India Especially for uninsured individuals and those requiring multiple MRI scans There is a huge amount.
  • Inconvenience in using the machine: However, conveniently, the person has to scan various parts of the body within the bore Do not need to move, they finish scanning This requires remaining still for an extended period of time, often up to several minutes.
    • done by person Any motion distorts the resulting image This may cause damage to the scan, requiring a repeat scan.
  • Heat dissipation: Generating a magnetic field of 1 Tesla or more, like the main magnet, is a major challenge.
    • Since Energy in the form of heat in non-superconducting materials will destroy this To maintain setup Requires significant amounts of energy, which incurs high costs.
  • Noise generated in MRI operation: switching of heavy currents within the machine, especially when 'Gradient Coil' When operated sequentially, there is loud noise during operation.
    • This extra noise, Inconvenience for the person undergoing the scan can cause.

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