What is Magnetic Resonance Imaging?
Magnetic Resonance Imaging (MRI) is a scanning method used to develop intricate images of the human body. Generally while an MRI is being conducted the human subject lies supine in a hollow tube located in the center of the MRI machine. The machine produces a strong magnetic field which resonates throughout the subject’s body. Because humans are mostly composed of water, analyzing the behavior of water molecules when subjected to this magnetic field can be used to develop images of the human body. When the protons of the water molecules are exposed to this initial magnetic field, their spins become aligned. After this occurs, the scanner of the MRI produces a radio frequency which causes the water protons to flip their spins. When the spins of the protons have been altered the radio signal stops and the protons return to their natural spin state in a process known as precession. The precession process produces a radio signal that can be measured by MRI scanners and used to develop detailed images of the human body. These detailed images help doctors to see intricate aspects of human anatomy such as the interior of joints, cartilage, ligaments, and muscles. MRIs are frequently used to diagnose musculoskeletal injuries such as fractures, tears, and dislocations. Brain MRIs can show things that are missed on a head CT scan, hence, it is more sensitive. The MRI can show parenchymal injury that the CT scan can miss. Things such as diffuse axonal injury, contusions, and posterior fossa bleeds.
What is diffusion tensor imaging?
Diffusion Tensor imaging (DTI) is a variation on the conventional MRI that can be utilized to uncover distinct information about microstructures within the central nervous system. DTI utilizes existing MRI equipment and normally does not require any unique contrasts or chemical tracers to carry out. DTI is performed by analyzing the specific diffusion rates and patterns that water molecules exhibit when in different tissues of the human body. There are two main components of water molecule diffusion that are measured in DTI, mean diffusivity and fractional anisotropy. The mean diffusivity represents the overall average square distance that a water molecule travels through tissue. Fractional anisotropy is the amount of diffusivity that can be attributed to the anisotropic movement patterns of water molecules. In brain tissue that is compromised fractional anisotropy tends to decrease and mean diffusivity tends to increase.
Diffusion of water can be affected by tissue microstructure and as a result DTI may be used to detect abnormalities in brain tissue caused by disease or trauma. DTI has been used clinically to detect several different neurological conditions such as stroke, brain injuries, and brain tumors; neurodegenerative conditions such as Alzheimer’s and epilepsy; neuropsychiatric conditions such as schizophrenia; as well as a wide range of other conditions. DTI has a continually expanding range of afflictions that it has successfully at detected, DTI is expected to become a frequently used diagnostic tool and one that will become an essential component of routine brain imaging.