Magnetic resonance imaging

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Magnetic resonance imaging

  1. 1. MAGNETIC RESONANCE IMAGING (MRI)
  2. 2. CONTENT
  3. 3. FUNCTIONAL MRI FMRI is a functional neuro- imaging produce using MRI technology that measures brain activity in blood flow. This technique relies on the fact that cerebral blood flow and neuronal activation are coupled. When an area of the is in use, blood flow to that region also increases. The primary form of fMRI uses the Blood-Oxygen- level dependent (BOLD) contrast discovered by seji ogawa
  4. 4. This is a type of specialized brain and body used to map neural activity in the brain or spinal cord of humans or other animals by imaging the change in blood flow (hemodynamic response) related to energy used by brain cells.
  5. 5. BOLD: BOLD is a method used in fMRI to observe different areas of brain, which are found to be active at any given time. NEURAL/NERVE CELL A neuron also known as a neuron or nerve cell is an electrically excitable cells that processes and transmits through electrochemical cells.
  6. 6. HOW MRI WORKS? To perform a study the patient is positioned within an MRI scanner which forms a strong magnetic field around the area to be imaged. Most medical application rely on detecting a radio frequency single emitted by be exited hydrogen atom in the body using energy from an oscillating magnetic field applied at the appropriate resonant frequency. The orientation of the image is controlled by varying the main magnetic field using gradient coils. As these coils are rapidly switched on or off they create the characteristics repetitive noises of an MRI scan. The contrast between different tissues is determined by rate at which excited atoms returns to the equilibrium state. MRI requires a magnetic field that is both strong and uniform. The field strength of the magnet is measured in tesla.
  7. 7. CONTRAST IN MRI Image contrast may be weighted to demonstrate different anatomical strucu- res or pathologies. Each tissues returns to its equilibrium state after excitation by the independent processes of T1 and T2 relaxation. To create a T1-weighted image we wait for different amounts of magnetization to recover before measuring the MR signal by changing the repetition time (TR). This image weighting is useful for assessing the cerebral cortex, identifying fatty tissue, characterizing focal liver lesions and for post-contrast imaging.
  8. 8. To create a T2-weighted image we wait for different amounts of magnetization to decay before measuring the MR signal by changing the echo time (TE). This image weighting is useful for detecting edema, revealing white matter lesions and assessing zonal anatomy in the prostate and uterus. HISTORY In 1952, Herman Carr produced a one-dimensional MRI image as reported in his Harvard PhD thesis.In the Soviet Union, Vladislav Ivanov filed (in 1960) a document with the USSR State Committee for Inventions and Discovery at Leningrad for a Magnetic Resonance Imaging device,although this was not approved until the 1970s.

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