Magnetic Resonance Imaging (MRI) Board Practice Exam

Fat suppression with inversion recovery works by using a 180-degree inversion pulse and selecting a specific inversion time (TI) so that fat’s longitudinal magnetization is nulled at the moment of signal readout. Because fat has a relatively short T1, there is a TI at which its magnetization passes through zero, so it appears dark in the image. Short Tau Inversion Recovery is designed to pick that TI, yielding fat-suppressed images while other tissues retain their signal based on the sequence’s weighting. This makes STIR particularly effective for highlighting pathology like edema or inflammation against a dark fat background. Standard T1-, T2-, or proton-density-weighted images do not inherently suppress fat; they show fat signal unless another fat-saturation technique is applied. STIR achieves suppression through the inversion-recovery approach, not through the standard weighting alone.