Simultaneous 99mTc-MDP/123I-MIBG tumor imaging using SPECT-CT: Phantom and constructed patient studies

Authors

  • Rakvongthai Yothin,

    1. Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
    Search for more papers by this author
  • Fakhri Georges El,

    1. Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
    Search for more papers by this author
  • Lim Ruth,

    1. Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
    Search for more papers by this author
  • Bonab Ali A.,

    1. Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
    Search for more papers by this author
  • Ouyang Jinsong

    Corresponding author
    1. Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
    Search for more papers by this author

Abstract

Purpose:

Authors’ goal is to evaluate the performance of simultaneous99mTc-MDP/123I-MIBG tumor imaging with fast Monte-Carlo (MC) based joint iterative reconstruction as compared to sequential 99mTc-MDP and 123I-MIBG tumor imaging.

Methods:

Noise-free99mTc and 123I SPECT projections were acquired separately using an anthropomorphic torso phantom modified to include a fillable tube around the lungs to mimic ribs. Additionally, 99mTc and 123I projections were acquired separately using a 1-cm spherical “tumor” placed at various distances from one detector. Tumor-present data were generated by adding tumor projections to the torso phantom data, which were scaled to the total counts in typical clinical studies. Twenty-five noise realizations were generated by adding Poisson noise to the projection data for each radionuclide. Dual-radionuclide data were synthesized by summing the 99mTc and 123I projections. Image reconstruction was performed using: (1) SR-OSEM, ordered subset expectation maximization (OSEM) without scatter correction (SC) using single-radionuclide (SR) data; (2) SR-MC-OSEM, OSEM with a fast MC-based SC using SR data; (3) DR-OSEM, OSEM without SC using dual-radionuclide (DR) data; and (4) DR-MC-JOSEM, joint OSEM with a fast MC-based SC using DR data. Ten 99mTc-MDP and ten 123I-MIBG data sets, which had tumors mathematically inserted, were also used to evaluate the performance of authors’ approach. For the phantom study, relative bias and relative standard deviation of tumor uptake were computed for each tumor using the tumor uptake in the noise-free single-radionuclide images, which were reconstructed by SR-MC-OSEM, as the gold standard. For both the phantom and constructed patient studies, mean contrast and standard deviation of contrast were computed for each tumor for both the single- and dual-radionuclide images. Additionally, contrast recovery was computed as the ratio between mean contrast and the mean contrast for SR-MC-OSEM.

Results:

For the phantom study, DR-MC-JOSEM yielded 2.7% on average relative bias of tumor uptake using the images, which were reconstructed from the noise-free SR data with SR-MC-OSEM, as the gold-standard. For both the phantom and constructed patient studies, DR-MC-JOSEM yielded 94.7% and 95.2% tumor contrast recovery on average using SR-MC-OSEM as the reference, in the phantom and constructed patient studies, respectively. DR-MC-JOSEM yielded comparable relative standard deviation of bias and standard deviation of contrast to SR-MC-OSEM.

Conclusions:

Simultaneous99mTc-MDP/123I-MIBG tumor imaging using authors’ dual-radionuclide reconstruction approach yielded comparable image quality to sequential 99mTc-MDP and 123I-MIBG imaging. For patients who need to undergo both scans, authors’ approach offers perfectly registered dual-tracer images under identical conditions without compromising image quality, and reduces the imaging cost while increasing patient throughput.

Ancillary