Preliminary evaluation of a quantitative regional dynamic SPECT renogram

Objectives Dynamic SPECT (dSPECT)[1] Tc99m-DTPA acquisitions using modern SPECT/CT cameras were optimized in healthy adult volunteer studies and compared with conventional planar renal scintigraphy and GFR blood sampling. dSPECT creates attenuation corrected, three dimensional (3D), overlap-free dynamic images of the whole kidney, and thus is able to provide us with total as well as regional renal function.

Methods Consenting volunteers (age: 42-63, n=4) were imaged using conventional planar Tc99m-DTPA scintigraphy (185MBq) with GFR blood sampling (at t = 1, 2, 3hrs). The results were compared with DTPA dSPECT single rotation acquisitions (185 or 370MBq, 180 or 360 degrees; 10-20secs per stop with 64 views per head) performed 2 days later on a Siemens Symbia T2 SPECT/CT system, with attenuation correction data provided by the 2 slice CT scanner.

Results Optimal dSPECT image acquisition protocols (370MBq, 360 degrees, 20 sec per 64 stops) yielded renal functional information provided by time activity curves (TACs) with an overall mean difference within 7-10% of planar TACs. Quantitative dSPECT analysis of 1mL renal volumes demonstrated consistent time to peak and clearance characteristics of the TACs, with peak amplitudes varying for different kidney regions. Clusters with varying concentration of renal functional tissue were observed.

Conclusions The dSPECT algorithm can be used with current SPECT/CT equipment to create 3D, time-varying renograms, which allow us to obtain regional functional information within the kidneys. With further patient studies we may be able to correlate TACs obtained from dSPECT to glomerular filtration rate, in order to obtain quantitative, regional measures of renal function. [1]Farncombe, T. et al., Dynamic SPECT Imaging Using a Single Camera Rotation, IEEE Trans. Nucl. Sci., Vo. 46, No. 4, August 199