MRI Typical Problems

Measuring Spins | | Data Overview

  • Shadowing
    • Due to inhomogeneities of the magnetic field, the response is skewed towards the outer areas of the volume.
  • Noise
    • MRI is prone to noise, since quality improves only linearily with scan time.
  • Resolution
    • Resolution is limited by the strength of the external magnetic field.
      • Static magnets are available of up to about 0.2 Tesla with limited resolution of 256×256.
      • A typical 1.5 Tesla field yields resolutions of 512×512 pixels in plane.
      • Higher magnetic fields of 3 Tesla require supra-conductors cooled with liquid helium.
      • Research on 8 Tesla magnets is ongoing.

Conclusion: Due to shadowing and various other sensor effects the is no absolute scale in MRI imaging, like the Hounsfield scale in regular X-ray tomography. Therefore an absolute relationship between material and measured value cannot be established.

Measuring Spins | | Data Overview