Preliminary results of a clinical validation of the dSPECT method for determination of renal glomerular filtration rate (GFR)

In adults, renal glomerular filteration rate (GFR) can be determined in vivo using a camera method in a planar imaging mode or in vitro using blood sampling. Both this methods´ however, have limitations. Accurate quantitation is difficult to achieve in planar imaging and blood method requires taking several blood samples and provides only an overall GFR value for both kidneys. The dynamic SPECT imaging (dSPECT) method when applied to renal studies allows us to measure, in 3D, temporal changes of activity distribution in each region of the kidney. Because this is being done in 3D and with proper attenuation correction dSPECT can potentially provide a more accurate and faster alternative to present methods of GFR determination. In this paper we report the preliminary results of the kidney function determination for seven normal volunteers obtained using three independent approaches, namely planar dynamic scan, blood sampling and the dSPECT method. The results of dSPECT reconstructions (3D movies) reprojected back (with attenuation) into a single plane were compared with planar images. The time activity curves obtained from these two types of studies were similar and the numerical values of the GFR determined using planar and dSPECT methods agreed with each other. An important conclusion from this comparison is that reprojected dSPECT images can provide the same information as planar studies which can then be analyzed in the conventional manner. However, the really significant advantage of using the full 4D dSPECT data is that dSPECT not only properly addresses attenuation and background subtraction problems, but also, while using only a short standard SPECT scan, creates 3D temporal images which potentially may provide quantitative regional GFR information, as accurate as obtained from the blood method and with spatial resolution much better than that of planar studies.