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Dellepiane G, Casolaro P, Gottstein A, Mateu I, Scampoli P, Braccini S. 44Sc production from enriched 47TiO 2 targets with a medical cyclotron. Appl Radiat Isot 2024; 206:111220. [PMID: 38301319 DOI: 10.1016/j.apradiso.2024.111220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 01/18/2024] [Accepted: 01/28/2024] [Indexed: 02/03/2024]
Abstract
44Sc is a β+-emitter which has been extensively studied for nuclear medicine applications. Its promising decay characteristics [t1/2 = 3.97 h, E [Formula: see text] = 632 keV (94.3%), Eγ = 1157 keV (99.9%); 1499 keV (0.91%)] make it highly attractive for clinical PET imaging, offering an alternative to the widely used 68Ga [t1/2 = 67.7 min, E [Formula: see text] = 836 keV (87.7%)]. Notably, its nearly fourfold longer half-life opens avenues for applications with biomolecules having extended biological half-lives and enables the centralized distribution of 44Sc radiopharmaceuticals. An additional advantage of employing 44Sc as a diagnostic radioisotope lies in its counterpart, the β--emitter 47Sc, which is currently under investigation for targeted radiotherapy. Together, they form an ideal theranostic pair, providing a comprehensive solution for both diagnostic imaging and therapeutic applications in nuclear medicine. At the Bern medical cyclotron, a study to optimize the production of scandium radioisotopes is currently ongoing. In this context, proton irradiation of titanium targets has been investigated, exploiting the reactions 47Ti(p,α)44Sc and 50Ti(p,α)47Sc. This approach enables the production of Sc radioisotopes within a single PET medical cyclotron facility, employing identical chemical procedures for target preparation and post-irradiation processing. In this paper, we report on cross-section measurements of the 47Ti(p,α)44Sc nuclear reaction using 95.7% enriched 47TiO2 targets. On the basis of the obtained results, the production yield and purity were calculated to assess the optimal irradiation conditions. Production tests were performed to confirm these findings.
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Affiliation(s)
- Gaia Dellepiane
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland.
| | - Pierluigi Casolaro
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
| | - Alexander Gottstein
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
| | - Isidre Mateu
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
| | - Paola Scampoli
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland; Department of Physics "Ettore Pancini", University of Napoli Federico II, Complesso Universitario di Monte S. Angelo, 80126 Napoli, Italy
| | - Saverio Braccini
- Albert Einstein Center for Fundamental Physics (AEC), Laboratory for High Energy Physics (LHEP), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland
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Klouda J, Fassbender ME, Mocko V. A combined inorganic-organic titanium-44/ scandium-44g radiochemical generator. J Chromatogr A 2023; 1711:464438. [PMID: 37857154 DOI: 10.1016/j.chroma.2023.464438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 10/21/2023]
Abstract
Scandium-44g (t1/2 = 4.0 h) is an emerging radioisotope for positron emission tomography. It can be produced with a radiochemical generator using its long-lived parent, titanium-44 (t1/2 = 59.1 years). This work presents a new inorganic substrate for 44Ti/44gSc radiochemical generator design based on porous TiO2 microbeads (80 µm and 110 µm particle size, 60 Å pores). Comprehensive evaluation of conditions optimal for generator construction (44Ti loading) and use (44gSc elution) is provided in three steps. For stable 44Ti loading onto titania, heat-treatment at 180 °C for 90 min is shown to be effective while 0.3 M HCl(aq) is identified as the medium of choice for 44gSc elution. Two titania-based 3.6 MBq generators prepared under optimized conditions are characterized with respect to 44gSc recovery and 44Ti breakthrough. Each of these generators employed a different guard substrate to minimize 44Ti breakthrough, TiO2 microbeads and ZR resin. Both are shown to provide comparable 44gSc recoveries close to 50% but differ in 44Ti breakthrough, which is significantly lower with the organic ZR resin guard substrate at 0.0002%. This concept represents a new inorganic-organic approach to 44Ti/44gSc generator design. Benefits of both substrates are exploited: TiO2 has potential for durability necessary for utilizing the long half-life of the 44Ti parent while ZR resin guard segments minimize 44Ti breakthrough.
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Affiliation(s)
- Jan Klouda
- Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA
| | | | - Veronika Mocko
- Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA.
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Benabdallah N, Zhang H, Unnerstall R, Fears A, Summer L, Fassbender M, Rodgers BE, Abou D, Radchenko V, Thorek DLJ. Engineering a modular 44Ti/ 44Sc generator: eluate evaluation in preclinical models and estimation of human radiation dosimetry. EJNMMI Res 2023; 13:17. [PMID: 36853422 PMCID: PMC9975127 DOI: 10.1186/s13550-023-00968-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 02/19/2023] [Indexed: 03/01/2023] Open
Abstract
BACKGROUND 44Sc/47Sc is an attractive theranostic pair for targeted in vivo positron emission tomographic (PET) imaging and beta-particle treatment of cancer. The 44Ti/44Sc generator allows daily onsite production of this diagnostic isotope, which may provide an attractive alternative for PET facilities that lack in-house irradiation capabilities. Early animal and patient studies have demonstrated the utility of 44Sc. In our current study, we built and evaluated a novel clinical-scale 44Ti/44Sc generator, explored the pharmacokinetic profiles of 44ScCl3, [44Sc]-citrate and [44Sc]-NODAGA (1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid) in naïve mice, and estimated the radiation burden of 44ScCl3 in humans. METHODS 44Ti/44Sc (101.2 MBq) in 6 M HCl solution was utilized to assemble a modular ZR resin containing generator. After assembly, 44Sc was eluted with 0.05 M HCl for further PET imaging and biodistribution studies in female Swiss Webster mice. Based on the biodistribution data, absorbed doses of 44/47ScCl3 in human adults were calculated for 18 organs and tissues using the IDAC-Dose software. RESULTS 44Ti in 6 M HCl was loaded onto the organic resin generator with a yield of 99.97%. After loading and initial stabilization, 44ScCl3 was eluted with 0.05 M HCl in typical yields of 82.9 ± 5.3% (N = 16), which was normalized to the estimated generator capacity. Estimated generator capacity was computed based on elution time interval and the total amount of 44Ti loaded on the generator. Run in forward and reverse directions, the 44Sc/44Ti ratio from a primary column was significantly improved from 1038 ± 440 to 3557 ± 680 (Bq/Bq) when a secondary, replaceable, ZR resin cartridge was employed at the flow outlet. In vivo imaging and ex vivo distribution studies of the reversible modular generator for 44ScCl3, [44Sc]-citrate and [44Sc]-NODAGA show that free 44Sc remained in the circulation significantly longer than the chelated 44Sc. The dose estimation of 44ScCl3 reveals that the radiation burden is 0.146 mSv/MBq for a 70 kg adult male and 0.179 mSv/MBq for a 57 kg adult female. Liver, spleen and heart wall will receive the highest absorbed dose: 0.524, 0.502, and 0.303 mGy/MBq, respectively, for the adult male. CONCLUSIONS A clinical-scale 44Ti/44Sc generator system with a modular design was developed to supply 44ScCl3 in 0.05 M HCl, which is suitable for further radiolabeling and in vivo use. Our data demonstrated that free 44ScCl3 remained in the circulation for extended periods, which resulted in approximately 10 times greater radiation burden than stably chelated 44Sc. Stable 44Sc/47Sc-complexation will be more favorable for in vivo use and for clinical utility.
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Affiliation(s)
- Nadia Benabdallah
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Program in Quantitative Molecular Therapeutics, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Hanwen Zhang
- Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO, 63110, USA. .,Program in Quantitative Molecular Therapeutics, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Washington University School of Medicine, Siteman Cancer Center, St. Louis, MO, 63110, USA.
| | - Ryan Unnerstall
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA
| | - Amanda Fears
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Program in Quantitative Molecular Therapeutics, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Lucy Summer
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA
| | - Michael Fassbender
- grid.148313.c0000 0004 0428 3079Chemistry Division, Los Alamos National Laboratory, PO Box 1663, Los Alamos, NM 87545 USA
| | - Buck E. Rodgers
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA ,grid.516080.a0000 0004 0373 6443Washington University School of Medicine, Siteman Cancer Center, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Department of Radiation Oncology, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Diane Abou
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA ,grid.516080.a0000 0004 0373 6443Washington University School of Medicine, Siteman Cancer Center, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Mallinckrodt Cyclotron Facility, Washington University School of Medicine, St. Louis, MO 63110 USA
| | - Valery Radchenko
- grid.232474.40000 0001 0705 9791Life Sciences Division, TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3 Canada ,grid.17091.3e0000 0001 2288 9830Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1 Canada
| | - Daniel L. J. Thorek
- grid.4367.60000 0001 2355 7002Washington University School of Medicine, Mallinckrodt Institute of Radiology, 510 S. Kingshighway Boulevard, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Program in Quantitative Molecular Therapeutics, Washington University School of Medicine, St. Louis, MO 63110 USA ,grid.516080.a0000 0004 0373 6443Washington University School of Medicine, Siteman Cancer Center, St. Louis, MO 63110 USA ,grid.4367.60000 0001 2355 7002Department of Biomedical Engineering, Washington University, St. Louis, MO 63110 USA
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Abstract
Chelators are necessary in nuclear medicine imaging to direct an inorganic radionuclide, a radiometal, to a desired target; unfortunately, there is no 'one-size-fits-all' chelator. As the toolbox of radiometals is expanding, new chelators are required to prevent off-target side effects. 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) is the current gold standard chelator for several radiometals, but typically, chelation requires harsh conditions, making it unsuitable to label biological vectors. The ideal chelator would allow labelling under mild conditions (near-neutral pH and low temperatures [∼37 °C]) and be both thermodynamically and kinetically stable. Over the past 2-3 years, several exciting chelators have been developed that have superior properties to make them worth investigating for future clinical applications.
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Affiliation(s)
- Deborah Sneddon
- MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, OX3 7LE, United Kingdom.
| | - Bart Cornelissen
- MRC Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, OX3 7LE, United Kingdom
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Lowis C, Ferguson S, Paulßen E, Hoehr C. Improved Sc-44 production in a siphon-style liquid target on a medical cyclotron. Appl Radiat Isot 2021; 172:109675. [PMID: 33756396 DOI: 10.1016/j.apradiso.2021.109675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 02/11/2021] [Accepted: 02/25/2021] [Indexed: 11/22/2022]
Abstract
In order to use new and promising radiometals for molecular imaging, it is important that they can be obtained as inexpensively and easily as possible. This often requires a cyclotron with solid target hardware or a radionuclide generator, which are not widely available for rarely used radionuclides. Here, we investigate the improved production of 44Sc with a siphon-style liquid target system and compare to our previous work with a simple liquid target. A metal salt solution with a high concentration of natural abundance Ca(NO3)2 (0.14 g/cm3) was irradiated with a medical cyclotron (12 MeV protons; 20 μA). 44Sc was produced via the natCa(p,x)44Sc reaction. As the pressure increase during irradiation was reduced in the siphon-style target, it was possible to irradiate with a higher proton beam current (20 μA) than with the simple liquid target system (7.9 μA). In addition, the saturation yield per μA of 44Sc was increased by a factor of 3.18 ± 0.05 (6.2 ± 0.1 MBq/μA with the siphon target versus 1.94 ± 0.08 MBq/μA with the simple target). This results in an overall increase in 44Sc activity by a factor of 11.
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Rosar F, Bohnenberger H, Moon ES, Rösch F, Denig A, Vincenz-Zörner D, Hoffmann MA, Khreish F, Ezziddin S, Schreckenberger M, Buchholz HG, Schaefer-Schuler A. Impact of prompt gamma emission of 44Sc on quantification in preclinical and clinical PET systems. Appl Radiat Isot 2021; 170:109599. [PMID: 33515928 DOI: 10.1016/j.apradiso.2021.109599] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/21/2020] [Accepted: 01/14/2021] [Indexed: 01/08/2023]
Abstract
44Sc is an increasingly investigated positron emitter for use in positron emission tomography (PET) imaging. However, 44Sc is a non-pure positron emitter, since prompt photons are co-emitted during the decay process. This study investigates coincidence energy spectra of 44Sc and its impact on PET quantification on a preclinical and clinical PET system in comparison with 18F. The raw data of the coincidence events revealed characteristic differences comparing the photon energy distribution of 44Sc and 18F. Due to prompt gamma emission of 44Sc, activity recovery is underestimated on PET systems. However, clinical PET imaging of 44Sc with acceptable quantitative accuracy appears feasible by using a single, constant correction factor.
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Affiliation(s)
- Florian Rosar
- Dep. of Nuclear Medicine, Saarland University, Homburg, Germany; Dep. of Nuclear Medicine, University of Mainz, Mainz, Germany.
| | | | - Euy Sung Moon
- Dep. of Chemistry - TRIGA Site, University of Mainz, Mainz, Germany
| | - Frank Rösch
- Dep. of Chemistry - TRIGA Site, University of Mainz, Mainz, Germany
| | - Achim Denig
- Dep. of Nuclear Physics, University of Mainz, Mainz, Germany
| | | | | | - Fadi Khreish
- Dep. of Nuclear Medicine, Saarland University, Homburg, Germany
| | - Samer Ezziddin
- Dep. of Nuclear Medicine, Saarland University, Homburg, Germany
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Ghiani S, Hawala I, Szikra D, Trencsényi G, Baranyai Z, Nagy G, Vágner A, Stefania R, Pandey S, Maiocchi A. Synthesis, radiolabeling, and pre-clinical evaluation of [ 44Sc]Sc-AAZTA conjugate PSMA inhibitor, a new tracer for high-efficiency imaging of prostate cancer. Eur J Nucl Med Mol Imaging 2021; 48:2351-2362. [PMID: 33420915 DOI: 10.1007/s00259-020-05130-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 11/18/2020] [Indexed: 01/04/2023]
Abstract
PURPOSE The aim of this work was to demonstrate the suitability of AAZTA conjugated to PSMA inhibitor (B28110) labeled with scandium-44 as a new PET tracer for diagnostic imaging of prostate cancer. BACKGROUND Nowadays, scandium-44 has received significant attention as a potential radionuclide with favorable characteristics for PET applications. A polyaminopolycarboxylate heptadentate ligand based on a 1,4-diazepine scaffold (AAZTA) has been thoroughly studied as chelator for Gd3+ ions for MRI applications. The excellent results of the equilibrium, kinetic, and labeling studies led to a preliminary assessment of the in vitro and in vivo behavior of [44Sc][Sc-(AAZTA)]- and two derivatives, i.e., [44Sc][Sc (CNAAZTA-BSA)] and [44Sc][Sc (CNAAZTA-cRGDfK)]. RESULTS B28110 was synthesized by hybrid approach, combining solid-phase peptide synthesis (SPPS) and solution chemistry to obtain high purity (97%) product with an overall yield of 9%. Subsequently, the radioactive labeling was performed with scandium-44 produced from natural calcium target in cyclotron, in good radiochemical yields (RCY) under mild condition (pH 4, 298 K). Stability study in human plasma showed good RCP% of [44Sc]Sc-B28110 up to 24 h (94.32%). In vivo PET/MRI imaging on LNCaP tumor-bearing mice showed high tracer accumulation in the tumor regions as early as 20 min post-injection. Ex vivo biodistribution studies confirmed that the accumulation of 44Sc-PSMA-617 was two-fold lower than that of the radiolabeled B28110 probes. CONCLUSIONS This work demonstrated the suitability of B28110 for the complexation with scandium-44 at room temperature and the high performance of the resulting new tracer based on AAZTA chelator for the diagnosis of prostate cancer using PET.
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Affiliation(s)
- S Ghiani
- Bracco Research Centre, Bracco Imaging SpA, Via Ribes 5, 10010, Colleretto Giacosa (TO), Italy.
| | - I Hawala
- Dipartimento di Biotecnologie Molecolari e Scienze per la salute, Centro di Imaging Molecolare, Università degli Studi di Torino, Via Nizza 52, 10126, Torino, Italy
| | - D Szikra
- Scanomed Ltd., Nagyerdei krt. 98, Debrecen, 4032, Hungary
- Division of Nuclear Medicine and Translational Imaging, Department of Medical Imaging, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - G Trencsényi
- Scanomed Ltd., Nagyerdei krt. 98, Debrecen, 4032, Hungary
- Division of Nuclear Medicine and Translational Imaging, Department of Medical Imaging, Faculty of Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - Z Baranyai
- Bracco Research Centre, Bracco Imaging SpA, Via Ribes 5, 10010, Colleretto Giacosa (TO), Italy
| | - G Nagy
- Scanomed Ltd., Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - A Vágner
- Scanomed Ltd., Nagyerdei krt. 98, Debrecen, 4032, Hungary
| | - R Stefania
- Dipartimento di Biotecnologie Molecolari e Scienze per la salute, Centro di Imaging Molecolare, Università degli Studi di Torino, Via Nizza 52, 10126, Torino, Italy
| | - S Pandey
- Bracco Research USA Inc., 259 Prospect Plains Rd., Bldg. H, Monroe Township, NJ, 08831, USA
| | - A Maiocchi
- Bracco SpA, Via Caduti di Marcinelle, 13, 20134, Milan, Italy
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Sinnes JP, Bauder-Wüst U, Schäfer M, Moon ES, Kopka K, Rösch F. 68Ga, 44Sc and 177Lu-labeled AAZTA 5-PSMA-617: synthesis, radiolabeling, stability and cell binding compared to DOTA-PSMA-617 analogues. EJNMMI Radiopharm Chem 2020; 5:28. [PMID: 33242189 PMCID: PMC7691401 DOI: 10.1186/s41181-020-00107-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 10/19/2020] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The AAZTA chelator and in particular its bifunctional derivative AAZTA5 was recently investigated to demonstrate unique capabilities to complex diagnostic and therapeutic trivalent radiometals under mild conditions. This study presents a comparison of 68Ga, 44Sc and 177Lu-labeled AAZTA5-PSMA-617 with DOTA-PSMA-617 analogues. We evaluated the radiolabeling characteristics, in vitro stability of the radiolabeled compounds and evaluated their binding affinity and internalization behavior on LNCaP tumor cells in direct comparison to the radiolabeled DOTA-conjugated PSMA-617 analogs. RESULTS AAZTA5 was synthesized in a five-step synthesis and coupled to the PSMA-617 backbone on solid phase. Radiochemical evaluation of AAZTA5-PSMA-617 with 68Ga, 44Sc and 177Lu achieved quantitative radiolabeling of > 99% after less than 5 min at room temperature. Stabilities against human serum, PBS buffer and EDTA and DTPA solutions were analyzed. While there was a small degradation of the 68Ga complex over 2 h in human serum, PBS and EDTA/DTPA, the 44Sc and 177Lu complexes were stable at 2 h and remained stable over 8 h and 1 day. For all three compounds, i.e. [natGa]Ga-AAZTA5-PSMA-617, [natSc]Sc-AAZTA5-PSMA-617 and [natLu]Lu-AAZTA5-PSMA-617, in vitro studies on PSMA-positive LNCaP cells were performed in direct comparison to radiolabeled DOTA-PSMA-617 yielding the corresponding inhibition constants (Ki). Ki values were in the range of 8-31 nM values which correspond with those of [natGa]Ga-DOTA-PSMA-617, [natSc]Sc-DOTA-PSMA-617 and [natLu]Lu-DOTA-PSMA-617, i.e. 5-7 nM, respectively. Internalization studies demonstrated cellular membrane to internalization ratios for the radiolabeled 68Ga, 44Sc and 177Lu-AAZTA5-PSMA-617 tracers (13-20%IA/106 cells) in the same range as the ones of the three radiolabeled DOTA-PSMA-617 tracers (17-20%IA/106 cells) in the same assay. CONCLUSIONS The AAZTA5-PSMA-617 structure proved fast and quantitative radiolabeling with all three radiometal complexes at room temperature, excellent stability with 44Sc, very high stability with 177Lu and medium stability with 68Ga in human serum, PBS and EDTA/DTPA solutions. All three AAZTA5-PSMA-617 tracers showed binding affinities and internalization ratios in LNCaP cells comparable with that of radiolabeled DOTA-PSMA-617 analogues. Therefore, the exchange of the chelator DOTA with AAZTA5 within the PSMA-617 binding motif has no negative influence on in vitro LNCaP cell binding characteristics. In combination with the faster and milder radiolabeling features, AAZTA5-PSMA-617 thus demonstrates promising potential for in vivo application for theranostics of prostate cancer.
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Affiliation(s)
- Jean-Philippe Sinnes
- Johannes Gutenberg-University Mainz, Department of Chemistry/ TRIGA, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany
| | - Ulrike Bauder-Wüst
- German Cancer Research Center (DKFZ), Division of Radiopharmaceutical Chemistry, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - Martin Schäfer
- German Cancer Research Center (DKFZ), Division of Radiopharmaceutical Chemistry, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany
| | - Euy Sung Moon
- Johannes Gutenberg-University Mainz, Department of Chemistry/ TRIGA, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany
| | - Klaus Kopka
- German Cancer Research Center (DKFZ), Division of Radiopharmaceutical Chemistry, Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.,German Cancer Research Center (DKFZ), Division of Radiopharmaceutical Chemistry and German Cancer Consortium (DKTK), Im Neuenheimer Feld 280, 69120, Heidelberg, Germany.,New address: Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiopharmaceutical Cancer Research, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - Frank Rösch
- Johannes Gutenberg-University Mainz, Department of Chemistry/ TRIGA, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany.
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Rosar F, Buchholz HG, Michels S, Hoffmann MA, Piel M, Waldmann CM, Rösch F, Reuss S, Schreckenberger M. Image quality analysis of 44Sc on two preclinical PET scanners: a comparison to 68Ga. EJNMMI Phys 2020; 7:16. [PMID: 32166581 PMCID: PMC7067939 DOI: 10.1186/s40658-020-0286-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 03/03/2020] [Indexed: 11/10/2022] Open
Abstract
Background 44Sc has been increasingly investigated as a potential alternative to 68Ga in the development of tracers for positron emission tomography (PET). The lower mean positron energy of 44Sc (0.63 MeV) compared to 68Ga (0.83 MeV) can result in better spatial image resolutions. However, high-energy γ-rays (1157 keV) are emitted at high rates (99.9%) during 44Sc decay, which can reduce image quality. Therefore, we investigated the impact of these physical properties and performed an unbiased performance evaluation of 44Sc and 68Ga with different imaging phantoms (image quality phantom, Derenzo phantom, and three-rod phantom) on two preclinical PET scanners (Mediso nanoScan PET/MRI, Siemens microPET Focus 120). Results Despite the presence of high-energy γ-rays in 44Sc decay, a higher image resolution of small structures was observed with 44Sc when compared to 68Ga. Structures as small as 1.3 mm using the Mediso system, and as small as 1.0 mm using the Siemens system, could be visualized and analyzed by calculating full width at half maximum. Full widths at half maxima were similar for both isotopes. For image quality comparison, we calculated recovery coefficients in 1–5 mm rods and spillover ratios in either air, water, or bone-equivalent material (Teflon). Recovery coefficients for 44Sc were significantly higher than those for 68Ga. Despite the lower positron energy, 44Sc-derived spillover ratio (SOR) values were similar or slightly higher to 68Ga-derived SOR values. This may be attributed to the higher background caused by the additional γ-rays. On the Siemens system, an overestimation of scatter correction in the central part of the phantom was observed causing a virtual disappearance of spillover inside the three-rod phantom. Conclusion Based on these findings, 44Sc appears to be a suitable alternative to 68Ga. The superior image resolution makes it an especially strong competitor in preclinical settings. The additional γ-emissions have a small impact on the imaging resolution but cause higher background noises and can effect an overestimation of scatter correction, depending on the PET system and phantom.
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Affiliation(s)
- Florian Rosar
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany. .,Department of Nuclear Medicine, Saarland University Medical Center, Homburg, Germany.
| | - Hans-Georg Buchholz
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Sebastian Michels
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Manuela A Hoffmann
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Markus Piel
- Institute of Nuclear Chemistry, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Christopher M Waldmann
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Frank Rösch
- Institute of Nuclear Chemistry, Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Stefan Reuss
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
| | - Mathias Schreckenberger
- Department of Nuclear Medicine, University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany
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10
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Orteca G, Sinnes JP, Rubagotti S, Iori M, Capponi PC, Piel M, Rösch F, Ferrari E, Asti M. Gallium-68 and scandium-44 labelled radiotracers based on curcumin structure linked to bifunctional chelators: Synthesis and characterization of potential PET radiotracers. J Inorg Biochem 2019; 204:110954. [PMID: 31838188 DOI: 10.1016/j.jinorgbio.2019.110954] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 11/28/2019] [Accepted: 11/30/2019] [Indexed: 01/08/2023]
Abstract
Curcumin metal complexes showed widespread applications in medicine and can be exploited as a lead structure for developing new tracers for nuclear medicine application. Herein, the synthesis, chemical characterization and radiolabelling with gallium-68 and scandium-44 of two new targeting vectors based on curcumin scaffolds and linked to the chelators 1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid (NODAGA) and 1,4-bis(carboxymethyl)-6-[bis(carboxymethyl)]amino-6-methylperhydro-1,4-diazepine (AAZTA) are reported. Synthesis of the precursors could be achieved with a 13% and 11% yield and radiolabelling generally afforded rapid incorporation under mild conditions (>95%). Stability in physiological media (~75% after 2 h in human blood for [68Ga]Ga-/[44Sc]Sc-AAZTA-PC21 and ~60% for [68Ga]Ga-NODAGA-C21, respectively) are generally enhanced if compared to the previously radiolabelled analogues. MSn fragmentation experiments showed high stability of the AAZTA-PC21 structure mainly due to the pyrazole derivatization of the curcumin keto-enol moiety and a more feasible radiolabelling was noticed both with gallium-68 and scandium-44 mainly due to the AAZTA-chelator properties. [68Ga]Ga-NODAGA-C21 showed the most favorable lipophilicity value (logD = 1.3). Due to these findings, both compounds appear to be promising candidates for the imaging of colorectal cancer, but further studies such as in vitro uptake and in vivo biodistribution experiments are needed.
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Affiliation(s)
- Giulia Orteca
- Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via G. Campi 103, 41125 Modena, Italy
| | - Jean-Philippe Sinnes
- Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, D-55126 Mainz, Germany
| | - Sara Rubagotti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, Azienda USL-IRCCS Reggio Emilia, via Amendola 2, 42122 Reggio Emilia, Italy
| | - Michele Iori
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, Azienda USL-IRCCS Reggio Emilia, via Amendola 2, 42122 Reggio Emilia, Italy
| | - Pier Cesare Capponi
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, Azienda USL-IRCCS Reggio Emilia, via Amendola 2, 42122 Reggio Emilia, Italy
| | - Markus Piel
- Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, D-55126 Mainz, Germany
| | - Frank Rösch
- Institute of Nuclear Chemistry, Johannes Gutenberg-University of Mainz, D-55126 Mainz, Germany
| | - Erika Ferrari
- Department of Chemical and Geological Sciences, University of Modena and Reggio Emilia, via G. Campi 103, 41125 Modena, Italy.
| | - Mattia Asti
- Radiopharmaceutical Chemistry Section, Nuclear Medicine Unit, Azienda USL-IRCCS Reggio Emilia, via Amendola 2, 42122 Reggio Emilia, Italy
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11
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Sinnes JP, Nagel J, Rösch F. AAZTA 5/AAZTA 5-TOC: synthesis and radiochemical evaluation with 68Ga, 44Sc and 177Lu. EJNMMI Radiopharm Chem 2019; 4:18. [PMID: 31659525 PMCID: PMC6675801 DOI: 10.1186/s41181-019-0068-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 07/16/2019] [Indexed: 11/10/2022] Open
Abstract
PURPOSE AAZTA (1,4-bis (carboxymethyl)-6-[bis (carboxymethyl)]amino-6-methylperhydro-1,4-diazepine) based chelators were initially developed in the context of magnetic resonance imaging. First radiochemical studies showed the capability of AAZTA to form stable complexes with radiolanthanides and moderately stable complexes with 68Ga. For a systematic comparison of the labelling capabilities with current diagnostic and therapeutic trivalent radiometals, AAZTA5 (1,4-bis (carboxymethyl)-6-[bis (carboxymethyl)]amino-6-[pentanoic-acid]perhydro-1,4-diazepine) was synthesized representing a bifunctional version with a pentanoic acid at the carbon-6 atom. To evaluate the effect of adding a targeting vector (TV) to the bifunctional chelator on the complex formation, AAZTA5-TOC was synthesized, radiolabeled and tested in comparison to the uncoupled AAZTA5. METHODS AAZTA5 was synthesized in a 5-step synthesis. It was coupled to the cyclic peptide TOC (Phe1-Tyr3 octreotide) via amide bound formation. AAZTA and AAZTA5-TOC complex formations with 68Ga, 44Sc and 177Lu were investigated at different pH, temperature and precursor amounts. Stability studies against human serum, PBS buffer, EDTA and DTPA were performed. RESULTS AAZTA5 and AAZTA5-TOC achieved quantitative labelling (> 95%) at room temperature in less than 5 min with all three nuclides at pH ranges from 4 to 5.5 with low precursor amounts of 1 to 10 nmol. [44Sc]Sc-AAZTA5 complexes as well as [44Sc]Sc-AAZTA5-TOC were completely stable. The 177Lu complexes of AAZTA5 and AAZTA5-TOC showed high stability comparable to the 44Sc complexes. In contrast, the [68Ga]Ga-AAZTA5 complex stability was rather low, but interestingly, [68Ga]Ga-AAZTA5-TOC was completely stable. CONCLUSION AAZTA5 appears to be a promising bifunctional chelator for 68Ga, 44Sc and 177Lu with outstanding labelling capabilities at room temperature. Complex stabilities are high in the case of 44Sc and 177Lu. While [68Ga]Ga-AAZTA complexes alone lacking stability, [68Ga]Ga-AAZTA5-TOC demonstrated high stability. The latter indicates an interesting feature of [68Ga]Ga-AAZTA5-labelled radiopharmaceuticals.
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Affiliation(s)
- Jean-Philippe Sinnes
- Johannes Gutenberg-University Mainz, Institute of Nuclear Chemistry, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany
| | - Johannes Nagel
- Johannes Gutenberg-University Mainz, Institute of Nuclear Chemistry, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany
| | - Frank Rösch
- Johannes Gutenberg-University Mainz, Institute of Nuclear Chemistry, Fritz-Strassmann-Weg 2, 55128, Mainz, Germany.
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12
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Eppard E, de la Fuente A, Mohr N, Allmeroth M, Zentel R, Miederer M, Pektor S, Rösch F. Labeling of DOTA-conjugated HPMA-based polymers with trivalent metallic radionuclides for molecular imaging. EJNMMI Res 2018; 8:16. [PMID: 29488030 PMCID: PMC5829281 DOI: 10.1186/s13550-018-0372-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 02/19/2018] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND In this work, the in vitro and in vivo stabilities and the pharmacology of HPMA-made homopolymers were studied by means of radiometal-labeled derivatives. Aiming to identify the fewer amount and the optimal DOTA-linker structure that provides quantitative labeling yields, diverse DOTA-linker systems were conjugated in different amounts to HPMA homopolymers to coordinate trivalent radiometals Me(III)* = gallium-68, scandium-44, and lutetium-177. RESULTS Short linkers and as low as 1.6% DOTA were enough to obtain labeling yields > 90%. Alkoxy linkers generally exhibited lower labeling yields than alkane analogues despite of similar chain length and DOTA incorporation rate. High stability of the radiolabel in all examined solutions was observed for all conjugates. Labeling with scandium-44 allowed for in vivo PET imaging and ex vivo measurements of organ distribution for up to 24 h. CONCLUSIONS This study confirms the principle applicability of DOTA-HPMA conjugates for labeling with different trivalent metallic radionuclides allowing for diagnosis and therapy.
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Affiliation(s)
- Elisabeth Eppard
- Clinic for Nuclear Medicine, University Medical Center Bonn, Bonn, Germany
| | - Ana de la Fuente
- Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Nicole Mohr
- Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Mareli Allmeroth
- Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Rudolf Zentel
- Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
| | - Matthias Miederer
- Clinic for Nuclear Medicine, University Medical Center Mainz, Langenbeckstraße 1, 55131, Mainz, Germany
| | - Stefanie Pektor
- Clinic for Nuclear Medicine, University Medical Center Mainz, Langenbeckstraße 1, 55131, Mainz, Germany.
| | - Frank Rösch
- Institute of Nuclear Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
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13
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Synowiecki MA, Perk LR, Nijsen JFW. Production of novel diagnostic radionuclides in small medical cyclotrons. EJNMMI Radiopharm Chem 2018; 3:3. [PMID: 29503860 PMCID: PMC5824710 DOI: 10.1186/s41181-018-0038-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/24/2018] [Indexed: 02/06/2023] Open
Abstract
The global network of cyclotrons has expanded rapidly over the last decade. The bulk of its industrial potential is composed of small medical cyclotrons with a proton energy below 20 MeV for radionuclides production. This review focuses on the recent developments of novel medical radionuclides produced by cyclotrons in the energy range of 3 MeV to 20 MeV. The production of the following medical radionuclides will be described based on available literature sources: Tc-99 m, I-123, I-124, Zr-89, Cu-64, Ga-67, Ga-68, In-111, Y-86 and Sc-44. Remarkable developments in the production process have been observed in only some cases. More research is needed to make novel radionuclide cyclotron production available for the medical industry.
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Affiliation(s)
- Mateusz Adam Synowiecki
- Radboudumc, Radboud Translational Medicine B.V, Geert Grooteplein 21 (route 142), 6525EZ Nijmegen, The Netherlands
| | - Lars Rutger Perk
- Radboudumc, Radboud Translational Medicine B.V, Geert Grooteplein 21 (route 142), 6525EZ Nijmegen, The Netherlands
| | - J. Frank W. Nijsen
- Radboudumc, Dept. of Radiology and Nuclear Medicine, Geert Grooteplein-Zuid 10, 6525GA Nijmegen, The Netherlands
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14
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Valdovinos HF, Hernandez R, Barnhart TE, Graves S, Cai W, Nickles RJ. Separation of cyclotron-produced 44Sc from a natural calcium target using a dipentyl pentylphosphonate functionalized extraction resin. Appl Radiat Isot 2014; 95:23-29. [PMID: 25464172 DOI: 10.1016/j.apradiso.2014.09.020] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 09/25/2014] [Accepted: 09/29/2014] [Indexed: 11/19/2022]
Abstract
Significant interest in 44Sc as a radioactive synthon to label small molecules for positron emission tomography (PET) imaging has been recently observed. Despite the efforts of several research groups, the ideal 44Sc production and separation method remains elusive. Herein, we propose a novel separation method to obtain 44Sc from the proton irradiation of calcium targets based on extraction chromatography, which promises to greatly simplify current production methodologies. Using the commercially available Uranium and Tetravalent Actinides (UTEVA) extraction resin we were able to rapidly (<20min) recover >80% of the activity generated at end of bombardment (EoB) in small ~1M HCl fractions (400μL). The chemical purity of the 44Sc eluates was evaluated through chelation with DOTA and DTPA, and by trace metal analysis using microwave induced plasma atomic emission spectrometry. The distribution coefficients (Kd) of Sc(III) and Ca(II) in UTEVA were determined in HCl medium in a range of concentrations from zero to 12.1M. The 44Sc obtained with our method proved to be suitable for the direct labeling of small biomolecules for PET imaging, with excellent specific activities and radiochemical purity.
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Affiliation(s)
- H F Valdovinos
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA.
| | - R Hernandez
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA
| | - T E Barnhart
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA
| | - S Graves
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA
| | - W Cai
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA; Department of Radiology, University of Wisconsin-Madison, WI, USA; University of Wisconsin Carbone Cancer Center, Madison, WI, USA
| | - R J Nickles
- Medical Physics Department, University of Wisconsin-Madison, Madison, WI, USA
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