Effect of gadolinium concentration on renal signal intensity: An in vitro study with a saline bag model

PURPOSE: To compare the effects of gadolinium concentration on intermediate-weighted fast inversion-recovery and T2-weighted fast spin-echo magnetic resonance (MR) images by using a saline bag model of the kidney. MATERIALS AND METHODS: Normal-saline bags containing gadopentetate dimeglumine in concentrations of 0-20 mmol/L were imaged by using a variety of pulse sequences. Signal intensity was measured. RESULTS: Signal intensity loss at high gadolinium concentrations (negative enhancement) was demonstrated with all MR sequences. Increasing T2 weighting increased the negative enhancement effect and reduced the minimum gadolinium concentration at which negative enhancement was seen. The results of this study match theoretic predictions. CONCLUSION: The negative enhancement of normal renal tissue seen in intermediate-weighted fast inversion-recovery MR imaging is caused by T2 shortening at high gadolinium concentrations. Thus, gadolinium-enhanced T2-weighted fast spin-echo imaging also is expected to show negative enhancement and may prove to be a superior sequence for MR imaging of pyelonephritis. Further clinical investigation is warranted.