Background Dosimetry after radiopharmaceutical therapy with 177Lu (177Lu-RPT) relies on quantitat... more Background Dosimetry after radiopharmaceutical therapy with 177Lu (177Lu-RPT) relies on quantitative SPECT/CT imaging, for which suitable reconstruction protocols are required. In this study, we characterized for the first time the quantitative performance of a ring-shaped CZT-based camera using two different reconstruction algorithms: an ordered subset expectation maximization (OSEM) and a block sequential regularized expectation maximization (BSREM) combined with noise reduction regularization. This study lays the foundations for the definition of a reconstruction protocol enabling accurate dosimetry for patients treated with 177Lu-RPT. Methods A series of 177Lu-filled phantoms were acquired on a StarGuide™ (GE HealthCare), with energy and scatter windows centred at 208 (± 6%) keV and 185 (± 5%) keV, respectively. Images were reconstructed with the manufacturer implementations of OSEM (GE-OSEM) and BSREM (Q.Clear) algorithms, and various combinations of iterations and subsets. Add...
Since its first suggestion as possible option for liver radioembolization treatment, the therapeu... more Since its first suggestion as possible option for liver radioembolization treatment, the therapeutic isotope holmium-166 (166Ho) caught the experts’ attention due to its imaging possibilities. Being not only a beta, but also a gamma emitter and a lanthanide, 166Ho can be imaged using single-photon emission computed tomography and magnetic resonance imaging, respectively. Another advantage of 166Ho is the possibility to perform the scout and treatment procedure with the same particle. This prospect paves the way to an individualized treatment procedure, gaining more control over dosimetry-based patient selection and treatment planning. In this review, an overview on 166Ho liver radioembolization will be presented. The current clinical workflow, together with the most relevant clinical findings and the future prospective will be provided.
Background Partition modeling allows personalized activity calculation for holmium-166 (166Ho) ra... more Background Partition modeling allows personalized activity calculation for holmium-166 (166Ho) radioembolization. However, it requires the definition of tumor and non-tumorous liver, by segmentation and registration of a separately acquired CT, which is time-consuming and prone to error. A protocol including 166Ho-scout, for treatment simulation, and technetium-99m (99mTc) stannous phytate for healthy-liver delineation was proposed. This study assessed the accuracy of automatic healthy-liver segmentation using 99mTc images derived from a phantom experiment. In addition, together with data from a patient study, the effect of different 99mTc activities on the 166Ho-scout images was investigated. To reproduce a typical scout procedure, the liver compartment, including two tumors, of an anthropomorphic phantom was filled with 250 MBq of 166Ho-chloride, with a tumor to non-tumorous liver activity concentration ratio of 10. Eight SPECT/CT scans were acquired, with varying levels of 99mTc ...
Background High activities of holmium-166 ( 166 Ho)–labeled microspheres are used for therapeutic... more Background High activities of holmium-166 ( 166 Ho)–labeled microspheres are used for therapeutic radioembolization, ideally directly followed by SPECT imaging for dosimetry purposes. The resulting high-count rate potentially impacts dead time, affecting the image quality and dosimetric accuracy. This study assesses gamma camera performance and SPECT image quality at high 166 Ho activities of several GBq. To this purpose, the liver compartment, including two tumors, of an anthropomorphic phantom was filled with 166 Ho-chloride, with a tumor to non-tumorous liver activity concentration ratio of 10:1. Multiple SPECT/CT scans were acquired over a range of activities up to 2.7 GBq. Images were reconstructed using a commercially available protocol incorporating attenuation and scatter correction. Dead time effects were assessed from the observed count rate in the photopeak (81 keV, 15% width) and upper scatter (118 keV, 12% width) window. Post reconstruction, each image was scaled with a...
Liver Intra-arterial PRRT with 111In-Octreotide, 2021
Over the past decade, the application of the radionuclide holmium-166 (166Ho) as a medical isotop... more Over the past decade, the application of the radionuclide holmium-166 (166Ho) as a medical isotope has been well established. Its high-energy β radiation, which can be used for a therapeutic effect, together with its γ radiation, which can be used for nuclear imaging purposes, makes it the second type of radionuclide suitable for radioembolization of unresectable liver malignancies. Furthermore, holmium-165 can be visualized by MRI because of its paramagnetic properties and by CT because of its high density. In this chapter, 166Ho radioembolization for the treatment of neuroendrocrine tumor patients will be presented. It has been demonstrated to be a feasible clinical practice and even though more evidence has to be gained, the promising results show the potentialities of 166Ho radioembolization in the treatment of metastases in the liver, commonly related to neuroendocrine tumors.
Background Myocardial perfusion imaging is a commonly performed SPECT protocol and hence it would... more Background Myocardial perfusion imaging is a commonly performed SPECT protocol and hence it would be beneficial if its scan duration could be shortened. For traditional gamma cameras, two developments have separately shown to allow for a shortened scan duration: (i) reconstructing with Monte Carlo-based scatter correction instead of dual-energy window scatter correction and (ii) acquiring projections with the SMARTZOOM collimator instead of a parallel-hole collimator. This study investigates which reduction in scan duration can be achieved when both methods are combined in a single system. Results The SMARTZOOM collimator was implemented in a Monte Carlo-based reconstruction package and the implementation was validated through image quality phantom experiments. The potential for scan duration reduction was evaluated with a phantom configuration that is realistic for myocardial perfusion imaging. The original reconstruction quality was achieved in 76 ± 8% of the original scan duratio...
Background Accurate dosimetry is essential in radioembolization. To this purpose, an automatic pr... more Background Accurate dosimetry is essential in radioembolization. To this purpose, an automatic protocol for healthy liver dosimetry based on dual isotope (DI) SPECT imaging, combining holmium-166 ( 166 Ho)-microspheres and technetium-99m ( 99m Tc)-colloid, was developed: 166 Ho-microspheres used as scout and therapeutic particles and 99m Tc-colloid to identify the healthy liver. DI SPECT allows for an automatic and accurate estimation of absorbed doses, introducing true personalized dosimetry. However, photon crosstalk between isotopes can compromise image quality. This study investigates the effect of 99m Tc downscatter on 166 Ho dosimetry, by comparing 166 Ho-SPECT reconstructions of patient scans acquired before ( 166 Ho-only) and after additional administration of 99m Tc-colloid ( 166 Ho-DI). Results The 166 Ho-only and 166 Ho-DI scans were performed in short succession by injecting 99m Tc-colloid on the scanner table. To compensate for 99m Tc downscatter, its influence was acco...
Background Dosimetry after radiopharmaceutical therapy with 177Lu (177Lu-RPT) relies on quantitat... more Background Dosimetry after radiopharmaceutical therapy with 177Lu (177Lu-RPT) relies on quantitative SPECT/CT imaging, for which suitable reconstruction protocols are required. In this study, we characterized for the first time the quantitative performance of a ring-shaped CZT-based camera using two different reconstruction algorithms: an ordered subset expectation maximization (OSEM) and a block sequential regularized expectation maximization (BSREM) combined with noise reduction regularization. This study lays the foundations for the definition of a reconstruction protocol enabling accurate dosimetry for patients treated with 177Lu-RPT. Methods A series of 177Lu-filled phantoms were acquired on a StarGuide™ (GE HealthCare), with energy and scatter windows centred at 208 (± 6%) keV and 185 (± 5%) keV, respectively. Images were reconstructed with the manufacturer implementations of OSEM (GE-OSEM) and BSREM (Q.Clear) algorithms, and various combinations of iterations and subsets. Add...
Since its first suggestion as possible option for liver radioembolization treatment, the therapeu... more Since its first suggestion as possible option for liver radioembolization treatment, the therapeutic isotope holmium-166 (166Ho) caught the experts’ attention due to its imaging possibilities. Being not only a beta, but also a gamma emitter and a lanthanide, 166Ho can be imaged using single-photon emission computed tomography and magnetic resonance imaging, respectively. Another advantage of 166Ho is the possibility to perform the scout and treatment procedure with the same particle. This prospect paves the way to an individualized treatment procedure, gaining more control over dosimetry-based patient selection and treatment planning. In this review, an overview on 166Ho liver radioembolization will be presented. The current clinical workflow, together with the most relevant clinical findings and the future prospective will be provided.
Background Partition modeling allows personalized activity calculation for holmium-166 (166Ho) ra... more Background Partition modeling allows personalized activity calculation for holmium-166 (166Ho) radioembolization. However, it requires the definition of tumor and non-tumorous liver, by segmentation and registration of a separately acquired CT, which is time-consuming and prone to error. A protocol including 166Ho-scout, for treatment simulation, and technetium-99m (99mTc) stannous phytate for healthy-liver delineation was proposed. This study assessed the accuracy of automatic healthy-liver segmentation using 99mTc images derived from a phantom experiment. In addition, together with data from a patient study, the effect of different 99mTc activities on the 166Ho-scout images was investigated. To reproduce a typical scout procedure, the liver compartment, including two tumors, of an anthropomorphic phantom was filled with 250 MBq of 166Ho-chloride, with a tumor to non-tumorous liver activity concentration ratio of 10. Eight SPECT/CT scans were acquired, with varying levels of 99mTc ...
Background High activities of holmium-166 ( 166 Ho)–labeled microspheres are used for therapeutic... more Background High activities of holmium-166 ( 166 Ho)–labeled microspheres are used for therapeutic radioembolization, ideally directly followed by SPECT imaging for dosimetry purposes. The resulting high-count rate potentially impacts dead time, affecting the image quality and dosimetric accuracy. This study assesses gamma camera performance and SPECT image quality at high 166 Ho activities of several GBq. To this purpose, the liver compartment, including two tumors, of an anthropomorphic phantom was filled with 166 Ho-chloride, with a tumor to non-tumorous liver activity concentration ratio of 10:1. Multiple SPECT/CT scans were acquired over a range of activities up to 2.7 GBq. Images were reconstructed using a commercially available protocol incorporating attenuation and scatter correction. Dead time effects were assessed from the observed count rate in the photopeak (81 keV, 15% width) and upper scatter (118 keV, 12% width) window. Post reconstruction, each image was scaled with a...
Liver Intra-arterial PRRT with 111In-Octreotide, 2021
Over the past decade, the application of the radionuclide holmium-166 (166Ho) as a medical isotop... more Over the past decade, the application of the radionuclide holmium-166 (166Ho) as a medical isotope has been well established. Its high-energy β radiation, which can be used for a therapeutic effect, together with its γ radiation, which can be used for nuclear imaging purposes, makes it the second type of radionuclide suitable for radioembolization of unresectable liver malignancies. Furthermore, holmium-165 can be visualized by MRI because of its paramagnetic properties and by CT because of its high density. In this chapter, 166Ho radioembolization for the treatment of neuroendrocrine tumor patients will be presented. It has been demonstrated to be a feasible clinical practice and even though more evidence has to be gained, the promising results show the potentialities of 166Ho radioembolization in the treatment of metastases in the liver, commonly related to neuroendocrine tumors.
Background Myocardial perfusion imaging is a commonly performed SPECT protocol and hence it would... more Background Myocardial perfusion imaging is a commonly performed SPECT protocol and hence it would be beneficial if its scan duration could be shortened. For traditional gamma cameras, two developments have separately shown to allow for a shortened scan duration: (i) reconstructing with Monte Carlo-based scatter correction instead of dual-energy window scatter correction and (ii) acquiring projections with the SMARTZOOM collimator instead of a parallel-hole collimator. This study investigates which reduction in scan duration can be achieved when both methods are combined in a single system. Results The SMARTZOOM collimator was implemented in a Monte Carlo-based reconstruction package and the implementation was validated through image quality phantom experiments. The potential for scan duration reduction was evaluated with a phantom configuration that is realistic for myocardial perfusion imaging. The original reconstruction quality was achieved in 76 ± 8% of the original scan duratio...
Background Accurate dosimetry is essential in radioembolization. To this purpose, an automatic pr... more Background Accurate dosimetry is essential in radioembolization. To this purpose, an automatic protocol for healthy liver dosimetry based on dual isotope (DI) SPECT imaging, combining holmium-166 ( 166 Ho)-microspheres and technetium-99m ( 99m Tc)-colloid, was developed: 166 Ho-microspheres used as scout and therapeutic particles and 99m Tc-colloid to identify the healthy liver. DI SPECT allows for an automatic and accurate estimation of absorbed doses, introducing true personalized dosimetry. However, photon crosstalk between isotopes can compromise image quality. This study investigates the effect of 99m Tc downscatter on 166 Ho dosimetry, by comparing 166 Ho-SPECT reconstructions of patient scans acquired before ( 166 Ho-only) and after additional administration of 99m Tc-colloid ( 166 Ho-DI). Results The 166 Ho-only and 166 Ho-DI scans were performed in short succession by injecting 99m Tc-colloid on the scanner table. To compensate for 99m Tc downscatter, its influence was acco...
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