T1 maps in upper abdomen: comparison of Look-Locker and B1-corrected variable-flip-angle (VFA) methods

Purpose T1 mapping has been recognized as a promising tool for quantitative measurements of various tissues that may assist in accurate and tissue specific diagnosis. The purpose of this study was to compare the T1 values of two whole-liver T1 mapping methods, free-breathing Look-Locker and breath-hold B1-corrected variable-flip-angle (VFA) in diagnosing liver cirrhosis, and compare the T1 relaxation time of various upper abdominal organs using two methods. Methods Non-enhanced T1 mapping with whole-liver coverage was performed on 85 prospectively enrolled suspicious liver tumor patients. Multiple abdominal MRI sequences were obtained. Image quality was assessed by scoring image artifacts on 5-point scale. T1 relaxation time for each organ was recorded. Statistical significance analyzed using Paired t test. Results T1 maps of Look-Locker method showed fewer artifacts, with score 5 in all cases compared to 36% in VFA method. There was no significant difference between cirrhotic and non-cirrhotic livers of either left or right lobe in both methods. T1 relaxation time was significantly lower ( p < 0.0001) in Look-Locker than VFA method in both lobes of liver, spleen, pancreas, left kidney, right kidney, kidney cortex and medulla, erector spinae and rectus abdominis. No significant difference was found between left and right lobe of liver in both methods. T1 relaxation time of both methods was significantly lower in kidney cortex ( p < 0.0001) than medulla on both left and right kidneys. Conclusions The choice of Look-Locker or B1-corrected VFA-based T1 mapping may affect T1 values of organs in upper abdomen. Look-Locker showed better image quality and less motion artifacts than B1-corrected VFA method.