Susceptibility-Weighted Imaging to Detect Neurologic Disorders

Susceptibility-weighted imaging is a high- spatial resolution 3D gradient- echo MR imaging technique that is used in the detection of intravascular venous deoxygenated blood as well as extra vascular blood products. This imaging technique brings out the pragmatic properties of blood products such as intracellular methemoglobin, deoxyhemoglobin and hemosiderin.  This technique has been used in the past to study pediatric neurologic disorders.

SWI utilizes the loss of signal intensity created by disturbance of a homogeneous magnetic field. Various paramagnetic, ferromagnetic substances such as air-tissue or air-bone interfaces can cause such disturbances. As spins encounter heterogeneity in the local magnetic field, they result in overall signal intensity loss in gradient – echo images.

Depending upon the applied magnetic field and the magnetic susceptibility of molecules within the brain, an induced field in generated. Signal intensity changes are also dependant on various factors such as red blood cell integrity, molecular diffusion, deoxyhemoglobin concentration, voxel size, blood flow and vessel orientation.

Clinical applications of Susceptibility-weighted imaging are as given below:
  • Detection of hemorrhagic lesions, shearing in trauma patients is difficult as the injuries tend to be small in size and have higher chance of getting missed by low resolution scans. SWI runs at high resolution and is extremely sensitive to bleeding making it possible to see small lesions to detect subtle injuries.  
  • Depiction of calcium or iron deposition in neurodegenerative disorders
  • Detection of acute stroke
  • Delineation of neoplasms with hemorrhage, calcification, or increased vascularity
  • Detection of vascular malformations
Susceptibility-weighted imaging uses a three dimensional, RF spoiled, high-resolution, 3D gradient echo scan to provide diagnostic and prognostic information for treatment of neurologic disorders.

 


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