Comparison of planar DMSA scan with an evaluation based on SPECT imaging in the split renal function assessment

Abstract

Background: Validation of the 99mTc-DMSA planar scintigraphy accuracy for split renal function assessment and comparison with evaluation based on SPECT imaging both with and without CT attenuation correction.

Materials and methods: For split renal function assessment two methods were used: A) planar scintigraphy based on anterior and posterior projections using correction for kidney depth calculated by the geometric mean; B) semi-quantitative evaluation based on SPECT (B1) and attenuation-corrected SPECT/CT (B2) images using locally developed software for kidney segmentation and voxel-based analysis. All three methods were performed with a phantom simulating body including pair of kidneys. For patient study methods A and B1 were applied on a group of 140 children and adolescents with various renal diseases. Renal function ratios were compared both mutually and with physically measured activity ratios in the phantom.

Results: Method A provided results which were closest to measured reference values (average absolute difference of 0.9 percentage points [pp]). Method B1 was noticeably worse (2.1pp), whereas attenuation correction (B2) improved tomography results considerably (1.3 pp). The superiority of planar imaging could be caused among others by differences in creation of planar range of interest compared to tomographic volume of interest. However all the differences were under the threshold of any clinical importance. The comparison between method A and B1 based on patient study also showed differences mostly of none clinical importance.

Conclusion: Routine evaluation of split renal function using planar technique with correction of the kidney depth is at least equivalent to tomographic evaluation, and there is no need to update the established clinical practice.

Keywords: 3D SPECT method analysis; childhood; split renal function ratio; static renal 99mTc-DMSA scintigraphy.