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

Abstract

Purpose: Authors' goal is to evaluate the performance of simultaneous 99m Tc-MDP/ 123 I-MIBG tumor imaging with fast Monte-Carlo (MC) based joint iterative reconstruction as compared to sequential 99m Tc-MDP and 123 I-MIBG tumor imaging. Methods: Noise-free 99m Tc and 123 I SPECT projections were acquired separately using an anthropomorphic torso phantom modified to include a fillable tube around the lungs to mimic ribs. Additionally,99m Tc and 123 I 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 99m Tc and 123 I 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 dualradionuclide (DR) data; and (4) DR-MC-JOSEM, joint OSEM with a fast MC-based SC using DR data. Ten 99m Tc-MDP and ten 123 I-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: Simultaneous 99m Tc-MDP/ 123 I-MIBG tumor imaging using authors' dual-radionuclide reconstruction approach yielded comparable image quality to sequential 99m Tc-MDP and 123 I-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.

Joint reconstruction of Ictal/inter-ictal SPECT data for improved epileptic foci localization

“…For an imaging system with limited counts like SPECT, one of the most effective approaches to improve image quality is to correctly model the noise in SPECT projections. Inspired by our previous work on dual‐radionuclide SPECT, we propose a novel reconstruction method in which both ictal and inter‐ictal projections are jointly reconstructed while preserving Poisson noise on both scans in a single reconstruction framework. Moreover, the registration transformation between the ictal and the inter‐ictal scans is incorporated within the joint reconstruction to mitigate the effect of the patient's head position mismatch between the two separately acquired scans.…”

Multiplexed imaging for diagnosis and therapy

“…However, because of crosstalk between energy spectra and scatter, non-trivial correction methods must be applied, and the energy resolution of scanners is continuously sought to improve this outcome 166,167 . Despite this limitation, dual-tracer SPECT imaging is feasible using 201 Tl or 111 In in healthy volunteers and in diverse disease settings, and including brain imaging, cardiac imaging and cancer imaging 166,[168][169][170][171] . Improved scanner technology 172 and kinetic analysis also promulgate simultaneous dual-isotope imaging in PET, as demonstrated for single-scan dual-tracer (staggered injection of FDG and FLT; 120 min of scan time) studies in patients with primary brain tumours 173 .…”

Simultaneous dual-tracer 99mTc-tetrofosmin and 123I-BMIPP acquisition with CZT for ischemic memory: The future approaches to image the past

“…Besides cardiac imaging, simultaneous dual isotope acquisition possibilities have been explored for different applications as for brain, 10 and oncological imaging. 11 However, its realization has been extremely demanding, due to conventional gamma camera limitations, such as the consistent cross-contamination between different isotope energy windows. The cross-contamination issue has a much higher impact as the energy windows are closer.…”