Comparison of Physiological Triggering Schemes for Diffusion-Weighted Magnetic Resonance Imaging in Kidneys

Purpose: To determine the potential benefit of combined respiratory-cardiac triggering for diffusion-weighted imaging (DWI) of kidneys compared to respiratory triggering alone (RT). Materials and Methods: Renal DWI was performed in 17 volunteers comparing RT, combined respiratory-cardiac triggering (RCT), and combined respiratory-cardiac triggering with slice position correction (RCTF). Data were analyzed in three ways: A1) Model-free analysis of the signal stability over repeated measurements; A2) Analysis of the deviation from diffusion-model fitting comparing the root mean squared error (RMSE), assessing within-subject variabilities; and A3) Analysis of diffusion indices comparing between-subject variabilities. Results: Combined respiratory-cardiac triggering yielded lower signal fluctuations and more reliable diffusion parameter estimation than respiratory triggering alone in all three analysis methods: A1) The mean coefficient of variation (CV) for all subjects was 4.2 +/- 1.1% and 4.3 +/- 0.9% for RCT and RCTF, respectively, which was significantly lower compared to RT (5.3 +/- 0.9%, P < 0.005); A2) RT yielded significantly higher RMSEs than RCT and RCTF: A3) The between-subject variations of diffusion indices tended toward higher values for RT. The results were independent of perfusion contributions to the DWI data. No difference was determined between RCT and RCTF. Total acquisition time was only slightly prolonged for respiratory-cardiac double-triggering. Conclusion: Respiratory-cardiac double-triggering seems advantageous for renal DWI.