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Updated: May 8, 2026
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Anatomically CT-guided iterative reconstruction using KEM for sparse projection 99mTc-MDP Bone SPECT/CT: quantitative
Chunxing Wu1, Yueming Zha1, Liangjun Xie1
1Department of Nuclear Medicine, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou, Guangdong Province, People's Republic of China.
Abstract:
Objective. This study systematically compared the anatomically CT-guided Kernel Expectation Maximization (KEM) algorithm with traditional Ordered Subset Expectation Maximization (OSEM) for bone SPECT reconstruction. Full and progressively sparse-projection (1/2, 1/4, 1/16) data were used to explore reducing scan time while maintaining image quality.
Approach:
Sixty-seven prostate cancer (PCa) patients with bone metastases underwent SPECT/CT scans. SPECT images were reconstructed using KEM and OSEM under full-projection and sparse-projection (1/2, 1/4, 1/16) conditions. The dominant metastatic lesion was identified, and tumor-to-background ratios (T/Bmax, T/Bmean) were quantified. Image quality metrics (MAE, MSE, PSNR, SSIM, NRMSE) for sparse-projection reconstructions were evaluated using full-projection reconstructions as the reference. Statistical analyses compared KEM and OSEM performance under all sparse conditions.Main results. KEM-reconstructed images demonstrated significantly higher T/Bmax and T/Bmean than OSEM across both full and sparse projections (P < 0.05). While MAE and MSE showed no significant differences between KEM and OSEM under sparse conditions (P > 0.05), KEM exhibited superior PSNR, SSIM, and NRMSE (all P < 0.05). Specifically, PSNR (KEM versus OSEM): 53.22 ± 7.39 versus 49.68 ± 5.88 (1/2), 49.49 ± 7.10 versus 46.13 ± 5.96 (1/4), 39.19 ± 7.11 versus 39.59 ± 4.89 (1/16). SSIM: 0.80 ± 0.04 versus 0.63 ± 0.05 (1/2), 0.64 ± 0.05 versus 0.54 ± 0.05 (1/4), 0.57 ± 0.08 versus 0.50 ± 0.06 (1/16).
Nrmse:
0.53 ± 0.07 versus 0.56 ± 0.04 (1/2), 0.77 ± 0.04 versus 0.79 ± 0.04 (1/4), 0.96 ± 0.01 versus 0.96 ± 0.01 (1/16). KEM with 1/4 projection achieved comparable PSNR, SSIM, and NRMSE to OSEM with 1/2 projection. KEM with 1/16 projection outperformed OSEM with full projection in T/Bmax and T/Bmean.
Significance:
The KEM algorithm significantly enhanced lesion conspicuity (superior T/Bmax, T/Bmean) while maintaining OSEM-equivalent accuracy under low projections. This suggests potential for optimizing SPECT/CT workflow by reducing acquisition time without compromising diagnostic quality.
