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.

Purpose: To 1) assess the potential of magnetization transfer (MT)-weighted Key words: Kidneys, MR imaging; MR imaging to improve the often poor visibility of native kidneys in patients technology; ultrasonography. with a renal transplant; and 2) compare low-field MR imaging and ultrasonography (US) for imaging these fibrotic kidney remnants.Correspondence: Sami Kajander, Material and Methods: Seventy-two native kidneys of 36 patients were pros-Department of Diagnostic pectively evaluated with US and MR. In low-field (0.1 T) MR imaging, T1-, Radiology, University Hospital of T2-and MT-weighted sequences were used. MT-weighted images were compared Turku, Kiinamyllynkatu 4-8, with T2-weighted images in their ability to delineate the kidneys from their FIN-20520 Turku, Finland. surroundings whereas US and MR were compared for detection of renal cysts FAX π358 2 26 12 950. and possible solid tumors.Results: MT-weighted images proved superior to conventional T2-weighted Accepted for publication 7 February images in producing contrast between the kidney remnants and their fatty sur-2000. roundings. Although US revealed a few small renal cysts that were not seen at MR images, no statistical difference was found between the two modalities in this respect.Conclusion: MT imaging, due to its unique protein-specific signal depression, offers significantly improved visualization and delineation of end-stage kidneys. US, because its better availability and cost-benefit ratio, remains the methodof-choice compared to low-field MR imaging in detecting cysts in multicystic kidneys. MR investigation is helpful in selected patients and may be used as an alternative.