Nếu không có sự hấp thu chất hoạt động hoặc bài tiết từ các ống thận. MỘT SỐ phương pháp có Been phát triển cho Ước tính GFR từ dữ liệu y học hạt nhân năng động, là tất cả ý định cản trở bởi tính thống kê nghèo của nghiên cứu này năng động và vấn đề kế toán cho các thành phần extrarenal của tín hiệu. | Magnetic Resonance Nephrourography 15 as a filtered agent without active excretion or uptake from the renal tubules. Several methods have been developed for estimating the GFR from dynamic nuclear medicine data but all are hampered by the poor counting statistics of such dynamic studies and the problem of accounting for the extrarenal component of the signal. Recently several groups have applied the methods developed for nuclear medicine to dynamic MR imaging data acquired in conjunction with an injection of the contrast agent gadoli-nium-diethylenetriamine pentaacetic acid. In applying these techniques to MR imaging data several issues must be addressed. First although nuclear medicine measures the activity and hence the concentration of the contrast agent directly in MR imaging the contrast agents change signal by altering the relaxation times of the tissue producing a linear relationship with the concentration over only a limited range of concentrations. Second the exact relationship between the signal and concentration depends on the flip angle used and because the flip angle varies across the slice in 2D studies time-consuming corrections are required for 2D data making these unsuitable for routine clinical applications. Third to obtain an adequate signal-to-noise ratio it generally is necessary to use surface array coils for the reception of the signal which in turn can lead to local variations in signal intensity that complicate the analysis of the data. One approach that the present authors have advocated 10 addresses these problems by using a slow injection of contrast over 10 seconds to limit the arterial concentration by using a 3D technique and discarding the outer slices to ensure a uniform flip angle and by using the precontrast signal to correct for spatial variations in the signal intensity. Calculation of the individual RBF and GFR from gadolinium-enhanced MRNU can be coupled with measurement of the individual kidney volumes cortex plus medulla . .
