Pediatric 99mTc-DMSA SPECT performed by using iterative reconstruction with isotropic resolution recovery: improved image quality and reduced radiopharmaceutical activity.

Abstract

To compare two methods of reconstructing technetium 99m (99mTc) dimercaptosuccinic acid (DMSA) renal single photon emission computed tomographic (SPECT) data--ordered subset expectation maximization with three-dimensional resolution recovery (OSEM-3D) and filtered back projection (FBP)--in children in terms of improving image quality and reducing the radiopharmaceutical activity and radiation dose. The institutional review board approved this retrospective study and waived the requirement for informed patient consent. Fifty sequential pediatric patient 99mTc-DMSA SPECT studies of 98 kidneys were retrospectively analyzed by using a dual-detector gamma camera. FBP reconstruction with data from both detectors was compared with OSEM-3D reconstruction with half the gamma photon counts (ie, data from only one detector). Two nuclear medicine physicians blinded to the patients' medical histories and reconstruction techniques evaluated the studies. Scores for image quality, renal size, and relative function were compared by using paired t tests. Total scores for renal cortical defects were compared by using the Wilcoxon signed rank test. The kappa coefficient was calculated as an indicator of the concordance between the OSEM-3D and FBP reconstruction methods. Image quality was significantly enhanced with OSEM-3D (P < .001, paired t test). Cortical defects were identified better on OSEM-3D images than on FBP images. Of the 98 kidney SPECT studies analyzed, 19 showed identical cortical defects and 75 showed none at both OSEM-3D and FBP. In four kidneys, OSEM-3D depicted cortical defects that were not seen with FBP. No significant difference in relative renal function between the two methods was observed (P = .973). Compared with FBP, OSEM-3D yielded superior image quality in the evaluation of 99mTc-DMSA renal SPECT data, with the potential for markedly reduced radiation doses and/or shorter scanning times for patients.