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SPECT-OPT multimodal imaging enables accurate evaluation of radiotracers for ?-cell mass assessments.

ABSTRACT: Single Photon Emission Computed Tomography (SPECT) has become a promising experimental approach to monitor changes in ?-cell mass (BCM) during diabetes progression. SPECT imaging of pancreatic islets is most commonly cross-validated by stereological analysis of histological pancreatic sections after insulin staining. Typically, stereological methods do not accurately determine the total ?-cell volume, which is inconvenient when correlating total pancreatic tracer uptake with BCM. Alternative methods are therefore warranted to cross-validate ?-cell imaging using radiotracers. In this study, we introduce multimodal SPECT - optical projection tomography (OPT) imaging as an accurate approach to cross-validate radionuclide-based imaging of ?-cells. Uptake of a promising radiotracer for ?-cell imaging by SPECT, (111)In-exendin-3, was measured by ex vivo-SPECT and cross evaluated by 3D quantitative OPT imaging as well as with histology within healthy and alloxan-treated Brown Norway rat pancreata. SPECT signal was in excellent linear correlation with OPT data as compared to histology. While histological determination of islet spatial distribution was challenging, SPECT and OPT revealed similar distribution patterns of (111)In-exendin-3 and insulin positive ?-cell volumes between different pancreatic lobes, both visually and quantitatively. We propose ex vivo SPECT-OPT multimodal imaging as a highly accurate strategy for validating the performance of ?-cell radiotracers.

SUBMITTER: Eter WA

PROVIDER: S-EPMC4832194 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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SPECT-OPT multimodal imaging enables accurate evaluation of radiotracers for β-cell mass assessments.

Eter Wael A WA Parween Saba S Joosten Lieke L Frielink Cathelijne C Eriksson Maria M Brom Maarten M Ahlgren Ulf U Gotthardt Martin M

Scientific reports 20160415

Single Photon Emission Computed Tomography (SPECT) has become a promising experimental approach to monitor changes in β-cell mass (BCM) during diabetes progression. SPECT imaging of pancreatic islets is most commonly cross-validated by stereological analysis of histological pancreatic sections after insulin staining. Typically, stereological methods do not accurately determine the total β-cell volume, which is inconvenient when correlating total pancreatic tracer uptake with BCM. Alternative met ...[more]

PMID: 27080529

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Project description:UNLABELLED:Spatial and temporal coregistration of nuclear and optical images can enable the fusion of the information from these complementary molecular imaging modalities. A critical challenge is in integrating the optical and nuclear imaging hardware. Flexible fiber-based fluorescence-mediated tomography (FMT) systems provide a viable solution. The various bore sizes of small-animal nuclear imaging systems can potentially accommodate the FMT fiber imaging arrays. In addition, FMT imaging facilitates coregistration of the nuclear and optical contrasts in time. Herein, we combine a fiber-based FMT system with a preclinical SPECT/CT platform. Feasibility of in vivo imaging is demonstrated by tracking a monomolecular multimodal imaging agent (MOMIA) during transport from the forepaw to the axillary lymph node region of a rat. METHODS:The fiber-based, video-rate FMT imaging system is composed of 12 sources (785- and 830-nm laser diodes) and 13 detectors. To maintain high temporal sampling, the system simultaneously acquires ratio-metric data at each detector. A 3-dimensional finite element model derived from CT projections provides anatomically based light propagation modeling. Injection of a MOMIA intradermally into the forepaw of rats provided spatially and temporally coregistered nuclear and optical contrasts. FMT data were acquired concurrently with SPECT and CT data. The incorporation of SPECT data as a priori information in the reconstruction of FMT data integrated both optical and nuclear contrasts. RESULTS:Accurate depth localization of phantoms with different thicknesses was accomplished with an average center-of-mass error of 4.1 ± 2.1 mm between FMT and SPECT measurements. During in vivo tests, fluorescence and radioactivity from the MOMIA were colocalized in spatially coincident regions with an average center-of-mass error of 2.68 ± 1.0 mm between FMT and SPECT for axillary lymph node localization. Intravital imaging with surgical exposure of the lymph node validated the localization of the optical contrast. CONCLUSION:The feasibility of integrating a fiber-based, video-rate FMT system with a commercial preclinical SPECT/CT platform was established. These coregistered FMT and SPECT/CT results with MOMIAs may facilitate the development of the next generation of preclinical and clinical multimodal optical-nuclear platforms for a broad array of imaging applications and help elucidate the underlying biologic processes relevant to cancer diagnosis and therapy monitoring.

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SPECT-OPT multimodal imaging enables accurate evaluation of radiotracers for ?-cell mass assessments.

Publications

SPECT-OPT multimodal imaging enables accurate evaluation of radiotracers for β-cell mass assessments.

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