(3) An Experimental Study on MR Imaging Artifacts by Air and Fat : Comparison of 2.0 T and 0.5 T Images(2. Tomographic Imaging)

Abstract

Very low magnetic susceptibility of the air causes local distortion of magnetic gradient and results in spatial mismapping and signal change, chemical shift artifacts are produced in the frequency-encoding axis by lipid molecules because of difference of resonance frequencies of contained protons with those of protons in water. A test tube phantom study was performed in 2.0 T and 0.5 T superconducting magnetic resonance imaging systems for the investigation of natures of susceptibility and chemical shift artifacts encountered in high and medium field strength and in various imaging sequences. Both artifacts were prominent in high field MR and showed characteristic appearances. Several signal voids were noted around the air-colums in gradients echo images and MRI at 0.5 T showed more severe artifacts in T2-weighted image than those in the other sequences. Familiarity with causes, appearances and mechanisms of various artifacts helps Radiotechnologist for interpretation of MRI.