Research ArticleAI/Advanced Image Analysis

Deep-Learning Generation of Synthetic Intermediate Projections Improves 177Lu SPECT Images Reconstructed with Sparsely Acquired Projections

Tobias Rydén, Martijn Van Essen, Ida Marin, Johanna Svensson and Peter Bernhardt
Journal of Nuclear Medicine April 2021, 62 (4) 528-535; DOI: https://doi.org/10.2967/jnumed.120.245548

Article Figures & Data

Figures

  • Figure1
  • FIGURE 1.
    FIGURE 1.

    Schematic illustration of CUSIP. Numbers indicate image size and number of features at each layer. Concat. = concatenate; Conv. = convolution; ReLU = rectified linear unit.

  • FIGURE 2.
    FIGURE 2.

    Comparison of acquired projections with corresponding SIPs in patients 1–4 from test group. Difference images display pixel value dissimilarities between acquired projections and SIPs. Blue indicates positive pixel values, white indicates no differences, and red indicates negative values. Unit of color bar is counts.

  • FIGURE 3.
    FIGURE 3.

    SPECT/CT reconstructions of Jaszczak phantom with 6 hot spheres having 25 times higher 177Lu activity concentration than background. AC-OSEM and ASCC-OSEM used 30 projections, 30–120SIPs, and 120 projections. Unit of color bar is arbitrary voxel values.

  • FIGURE 4.
    FIGURE 4.

    Recovery and SNR for 177Lu determined in various hot spheres in Jaszczak phantom for SPECT/CT AC-OSEM (A and C) and ASCC-OSEM (B and D) with 30 projections, 60 projections, 120 projections, 60–120SIPs, and 30–120SIPs.

  • FIGURE 5.
    FIGURE 5.

    Comparison of ASCC-OSEM with 30 projections, 30–120SIPs, and 120 projections in patients 1–4 of the 15 patients in test set. Difference images display pixel value dissimilarities between ASCC-OSEM 30 projections vs. ASCC-OSEM 120 projections and ASCC-OSEM 30–120SIPs vs. ASCC-OSEM 120 projections. Blue indicates positive pixel values, white indicates no differences, and red indicates negative values. Unit of color bar is arbitrary voxel values.

  • FIGURE 6.
    FIGURE 6.

    Evaluation scores for SPECT/CT AC-OSEM and ASCC-OSEM. Mean scores and SDs are shown at top of bars. Asterisks indicate statistical significance of scores between projection sets within AC-OSEM and ASCC-OSEM. *0.01 ≤ P < 0.05. **0.001 ≤ P < 0.01. ***P < 0.001.

  • FIGURE 7.
    FIGURE 7.

    Relative kidney activity concentration for AC-OSEM and ASCC-OSEM with 30 and 30–120SIPs vs. 120 projections. Relative activity concentration was determined in left (A) and right (B) kidneys.

Tables

  • TABLE 1

    Clinical SPECT Acquisition Protocols for 177Lu Dosimetry

    StudyTreatmentAcquisition time (min)Projections (n)Frame time (s)BPs (n)Measurement time after injection (h)
    Marin et al. (17)177Lu-DOTATATE21.3–42.76440–8014, 24, 144–192
    Sandström et al. (13)177Lu-DOTATATE30606011, 24, 96, 168
    Sandström et al. (14)177Lu-DOTATATE301203011, 24, 96, 168
    Hagmarker et al. (5)177Lu-DOTATATE3012030124
    Santoro et al. (15)177Lu-DOTATATE22.5604514, 24, 72, 192
    Garkavij et al. (16)177Lu-DOTATATE22.56045124/96
    Delker at al. (18)177Lu-PSMA-61721.312820124, 48, 72
    Kabasakal et al. (24)177Lu-PSMA20/BP9625224
    Hou et al. (19)177Lu-DOTATATE12–169615–2014, 24, 72
    Chicheportiche et al. (20)177Lu-DOTATATE156030120, 25, 168
    Beauregard et al. (23)177Lu-DOTATATE8–129610–1514, 24, 96
    Violet et al. (21)177Lu-PSMA-617(8–12)/BP9610–152–34, 24, 96
    Hippeläinen et al. (22)177Lu-DOTATATE10.76420124, 48, 168

    • BP = bed position; PSMA = prostate-specific membrane antigen.

  • TABLE 2

    RMSE, PSNR, and SSIM for SIPs and SPECT Images in Test Group

    Image typeRMSEPSNRSSIM
    SIPs2.95 (0.77)39.2 (3.8)0.926 (0.061)
    AC-OSEM 30 projections0.147 (0.060)47.2 (3.5)0.989 (0.008)
    AC-OSEM 30–120SIPs0.109 (0.044)*49.5 (3.3)*0.993 (0.005)*
    ASCC-OSEM 30 projections0.259 (0.101)49.0 (3.5)0.993 (0.005)
    ASCC-OSEM 30GF projections0.273 (0.162)48.3 (2.5)0.995 (0.004)†
    ASCC-OSEM 30–120SIPs0.195 (0.091)*50.8 (3.2)*0.996 (0.003)*

    • ↵* P < 0.001.

    • ↵† P < 0.01.

    • GF = gaussian postfilter, SD of 4 mm.

    • Data in parentheses are SDs.

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