Quantitative planar imaging method for measurement of renal activity by using a conjugate-emission image and transmission data

We are proposing a method to accurately measure renal activity in renograph y using Tc-99m labeled tracers. This method uses a conjugate-view image and transmission data for attenuation correction, the triple energy window (TE W) method for scatter correction, and background correction techniques that consider the source volume for accurate background activity correction. To examine this method in planar imaging, we performed two renal phantom stud ies with various uniform background activity concentrations. One study used two ideal box-shaped kidney phantoms with a thickness of 2 or 4 cm in a wa ter tank and the other study employed two real kidney-shaped phantoms in a fillable abdominal cavity. For these studies the kidney phantom-to-backgrou nd activity concentration ratio (S) was changed from 5 to infinity, The tra nsmission data were obtained with an external Tc-99m line array source. The anterior- and posterior-view emission images were acquired with a dual-hea ded gamma camera simultaneously and the TEW method was used to correct scat ter for the emission and transmission images. The results showed that this method with both the accurate background correction and scatter correction could give depth-independent count rates and could estimate the true count rate with errors of less than 5% for all S values. However, if either accur ate background correction or scatter correction was performed alone, the ab solute error increased to about 50% for the smaller S values. Our proposed method allows one to accurately and simply measure the renal radioactivity by planar imaging using the conjugate-emission image and transmission data. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)00 703-3].