Non-enhanced Renal MR Angiography Using Time Spatial Labeling Inversion Pulse (T-SLIP): Repeatability And Comparison Of Different Tagging Location

Purpose:To prospectively determine the repeatability of non-contrast enhanced renal arterialangiography with time-spatial labeling inversion pulse (T-SLIP), and to compare thevisibility of renal artery and its branches when different locations of tagging pulse wereplaced.Materials and Methods:Thirty six young healthy volunteers were enrolled in this study and were twiceexamined by non-contrast enhanced renal arterial angiography with T-SLIP in1.5T MRscanner.We examined each subject twice after a median of one week. There were16menand20women;mean age21.9years; Measurement error and repeatability was assessed foreach of the five major parameters (vessel-to-kidney ratio VKR, grade of renal arterialbranching, grading of image quality, diameter and area of the main renal artery) using theBland-Altman plot. Two independent observers recorded the values of the parameters;Inter-and intra-observer agreement was assessed using the intraclass correlationcoefficients. The same parameters, acquired at the tagging pulse placed just above thesuperior poles of both kidneys or closer to the main renal arteries, were compared by usingthe Wilcoxon signed-rank test.Results:All volunteers tolerated the examination well, and all MR data sets were eligible forevaluation. There were4volunteers out of total36recruited in this study having unilateraltwo main renal arteries. In this case, the larger one was used for analysis.3volunteersamong the36had unilateral accessory artery that was excluded in the analysis.Therepeatability of VKR was poor between the two examinations. Grading of arterialbranching by the T-SLIP was satisfactorily reproducible with the mean score of greater3.83 indicating the visibility of branches within the renal parenchyma. The image quality wasexcellent for Segment I (the main trunk of renal artery) and good for Segment II (segmentalbranches pre renal parenchyma) and III (vessels within the renal parenchyma) with asatisfying repeatability between two examinations and a good inter-and intra-observeragreement，which more than0.768. The intraclass correlation coefficients for the inter-andintra-observer measurements of both diameter and area of the main arteries ranged from0.781to0.934, indicating very good agreement. There were significant differences ingrading renal arterial branching and image quality of Segment III renal artery by eitherobserver between the two different tagging pulse locations(p<0.05). No significantdifferences in VKR and image quality of the Segment I and II were observed between thetwo locations.Conclusion:Non-contrast enhanced renal artery angiography with T-SLIP yields reliable andreproducible visualization of normal renal arteries. Localization of the tagging pulse closerto the main renal arteries provides better visibility of renal artery and its branches than thetag placement just above the superior poles of both kidneys.