Dynamic Gd-DTPA-Enhanced MR Imaging of the Kidney: Comparison between T1 – and T2*-Weighted Sequences

Abstract

Objective: To determine whether T1- or T2*-weighted sequences are more informative and practical in dynamic Gd-DTPA-enhanced MR imaging for the evaluation of renal blood flow and function. Materials and Methods: Dynamic Gd-DTPA-enhanced MR imaging of the kidney was performed in 7 patients by either Tl-weighted TurboFLASH (TR/TE/TI/FA = 9/4/27/8) or T2*-weighted FLASH (TR/TE/FA = 32/22/10) sequences for comparison of the enhancement pattern. None of the subjects had a suspicion of renal dysfunction from laboratory data, and the absence of renal artery stenosis was confirmed by conventional angiography. Results: During the early phase, the marked signal increase in T1-weighted imaging in the renal cortex corresponded to a similar marked decrease in signal intensity in T2*-weighted imaging. During the middle and late phases, the medulla was dramatically decreased in intensity on the T2*-weighted imaging resulting in a good contrast between the cortex and medulla. Conclusion: Both sequences may provide almost similar information about the renal cortical blood flow. However, T2*-weighted dynamic MR imaging may be more informative than T1-weighted dynamic MR imaging about the concentrating ability in the renal medulla. A high concentration of Gd-DTPA in the tubular structure was suspected to cause a dramatic decrease in intensity in the medulla in T2*-weighted imaging.

Evaluation of Complete and Partially Obstructed Kidneys Using Gd-DTPA Enhanced Dynamic MRI in Adolescent Swine

“…CUUO pigs demonstrated that the mean RSI patterns were almost similar to those of controls, and that mean RSI of the pelvis increased more compared with that of PUUO pigs, indicating that Gd-DTPA enhanced MRI is unable to detect changes in renal function at 24 hours after a complete ureteric obstruction. Similar results have been obtained in rats with different degrees of ureteric obstruction, where the mean RSI patterns differed significantly between CUUO and PUUO kidneys [11,18]. The in-depth interpretation of the RSI pattern observed after administration of Gd-DTPA is not straightforward.…”

“…Nevertheless, from a theoretical point of view, T1-weighted images have an advantage over T2weighted images with regard to image quality and signal-tonoise ratio, due to the use of a shorter echo time in T1-weighted images. A reproducible pattern of RSI has been demonstrated with a relatively large dosage of Gd-DTPA [18]. In that study, the significant differences in the RSI pattern between control kidneys and partially and severely obstructed kidneys indicated that this technique can provide useful information to discriminate functional changes in kidneys with and without ureteric obstruction.…”

“…Previously, dynamic Gd-DTPA enhanced MRI studies have been performed using different dosages of Gd-DTPA, from 0.025 to 0.5 mmol/kg [18,20], resulting in substantial differences in the dynamic relative signal intensity (RSI) pattern. Administration of a low dosage of Gd-DTPA decreases the longitudinal relaxation time (T1) but does not markedly affect the transversal relaxation time (T2), resulting in an increased RSI.…”