Comparison of chemical-shift and relaxation-dependent mechanisms for optimizing detection of paramagnetic contrast enhancement in MR imaging

In anatomic regions of high lipid content on T1-weighted spin-echo images, intensity of normal lipid competes with the enhanced signal intensity of paramagnetic contrast-relaxed pathologic water protons, resulting in many cases in suboptimal contrast and limited detection and staging of lesions. The authors have examined better methods for detecting regions of enhancement using a frequency selective method, paramagnetic enhancement accentuation by chemical shift (PEACH) imaging, and a T1-dependent mechanism (short T1 inversion-recovery [STIR]). STIR can suppress both lipid and paramagnetic-enhanced protons with overlapping relaxation times in the range of lipid; it may also lead to poor contrast between unenhanced high-signal lesions with elevated T2 and regions of paramagnetic contrast enhancement. Proper choice of pulse-sequence parameters and lipid- suppression mechanisms can result in paramagnetic contrast- enhanced studies that are better than the current T1-weighted studies