Count-based quantitation of functional renal volume by SPECT imaging

The quantitation of absolute renal functional volume is of interest because many pathological processes are known to affect the growth and parenchymal volume of kidneys. Unlike thresholding and edge-detection methods, the count-based method of volume quantitation is not highly sensitive to boundary definition. In this investigation, count-based kidney volume quantitation was compared to that of fixed threshold-based estimation with and without the inclusion of attenuation and scatter compensation in reconstruction. The Alderson Organ Scanning Phantom kidneys were filled with a Tc-99m containing solution and placed in the Organ Scanning Phantom. Inserts shaped like the pelvis region of the kidneys were used to vary kidney volume. Emission imaging of the Tc-99m, and transmission imaging of a Gd-153 line source were performed by a triple-headed SPECT system. Without the compensation for attenuation and scatter, the count-based method significantly under-estimated kidney volume. With the inclusion of attenuation and scatter compensation, count-based volume quantitation was more accurate than volume estimation with a fixed threshold adapted to the image acquisition and reconstruction strategies employed.