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14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Proton induced production and radiochemical isolation of 44 Ti from scandium metal targets for 44 Ti/ 44 Sc generator development

Scandium-44 g (half-life 3.97 h) shows promise for application in positron emission tomography (PET), due to favorable decay parameters. One of the sources of 44g Sc is the 44 Ti/ 44g Sc generator, which can conveniently provide this radioisotope on a daily basis at a diagnostic facility. Titanium-44 (half-life 60.0 a), in turn, can be obtained via proton irradiation of scandium metal targets. A substantial 44 Ti product batch, however, requires high beam currents, long irradiation times and an elaborate chemical procedure for 44 Ti isolation and purification. This study describes the production of a combined 175 MBq (4.7 mCi) batch yield of 44 Ti in week long proton irradiations at the Los Alamos Isotope Production Facility (LANL-IPF) and the Brookhaven Linac Isotope Producer (BNL-BLIP). A two-step ion exchange chromatography based chemical separation method is introduced: first, a coarse separation of 44 Ti via anion exchange sorption in concentrated HCl results in a 44 Tc/Sc separation factor of 10 2 –10 3 . A second, cation exchange based step in HCl media is then applied for 44 Ti fine purification from residual Sc mass. In conclusion, this method yields a 90–97% 44 Ti recovery with an overall Ti/Sc separation factor of ≥10 6 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Separation of 44 Ti from proton irradiated scandium by using solid-phase extraction chromatography and design of 44 Ti/ 44 Sc generator system

Scandium-44 g (half-life 3.97 h) shows promise for positron emission tomography (PET) imaging of longer biological processes than that of the current gold standard, 18 F, due to its favorable decay parameters. One source of 44 gSc is the long-lived parent nuclide 44 Ti (half-life 60.0 a). A 44 Ti/ 44 gSc generator would have the ability to provide radionuclidically pure 44 gSc on a daily basis. The production of 44 Ti via the 45 Sc(p,2n) reaction requires high proton beam currents and long irradiation times. Recovery and purification of no-carrier added (nca) 44 Ti from scandium metal targets involves complex separation chemistry. In this study, separation systems based on solid phase extraction chromatography were investigated, including branched diglycolamide (BDGA) resin and hydroxamate based ZR resin. Lastly, results indicate that ZR resin in HCl media represents an effective 44 Ti/ 44 gSc separation system.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Nuclear Data Sheets for A = 44

The experimental data are evaluated for known nuclides of mass number A=44 (Si,P,S,Cl,Ar,K,Ca,Sc,Ti,V, Cr,Mn). Detailed evaluated level properties and related information are presented, including adopted values of level and {gamma}-ray energies, decay data (energies, intensities and placement of radiations), and other spectroscopic data. This work supersedes earlier full evaluations of A=44 published by 1999Ca45 and 1990En08 (also 1998En04 update). No excited states are known in {sup 44}Si, {sup 44}P, {sup 44}Cr, {sup 44}Mn. Only one excited state is known in 44V and its Isobaric Analog State (IAS) has been observed but with the level energy not known. Information for {sup 44}S, {sup 44}Cl and {sup 44}Ar is limited and their radioactive decay schemes seem incomplete in view of large Q values and known excitations much below than allowed by Q values. The {sup 44}Ca, {sup 44}Sc and {sup 44}Ti nuclides remain as the most extensively studied from many different reactions and decays.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Analysis of isomeric ratios for medium-mass nuclei

Values of the isomeric ratios for product nuclei originating from simple charge-exchange reactions were analyzed. The cross sections for the formation of product nuclei in ground and isomeric states were calculated with the aid of the TALYS 1.4 and EMPIRE 3.2 codes. The calculated values of the isomeric ratios were compared with their experimental counterparts taken from the EXFOR database. For the {sup 86,87}Y, {sup 94,95,96,99}Tc, and {sup 44}Sc nuclei, the experimental values of the isomeric ratios exceed the respective calculated values. The nuclei in question feature weak deformations and have high-spin yrast lines and rotational bands. The possible reason behind the discrepancy between theoretical and experimental isomeric ratios is that the decay of yrast states leads with a high probability to the formation of isomeric states of detected product nuclei.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Improved titanium-44 purification process for establishing a high apparent molar activity titanium-44/scandium-44 generator

44 Sc-radiopharmaceuticals are gaining more interest but still lack availability. The proof of principle of a 44 Ti/ 44 Sc generator, which can produce 44 Sc daily, has been established but with some limitations and drawbacks. Despite recent advances, separation of 44 Ti from massive quantities of scandium target material is still cumbersome. Here, in this work, the improved radiochemical separation of 44 Ti from residual scandium target material was carried out by precipitation of Sc with fluoride ions. Furthermore, two approaches were used to set up a high apparent molar activity small-scale generator. The first method relied on extraction chromatography for fine purification using a DGA resin, followed by loading of the purified 44 Ti onto a ZR resin column. In the second method, 44 Ti was loaded on the ZR resin directly after the precipitation step. This second method was used to set up a generator of 370 kBq and evaluate by radiolabeling. An apparent molar activity of 2 MBq/nmol was obtained for the radiolabeling with DOTA, the most common and suitable chelate for scandium. This result is comparable with previously published data on 44m/44 Sc.

44Sc↗
DOE OSTI2025

Synthesis of DOTA-Based 43 Sc Radiopharmaceuticals Using Cyclotron-Produced 43 Sc as Exemplified by [ 43 Sc]Sc-PSMA-617 for PSMA PET Imaging

The implementation of theranostics in oncologic nuclear medicine has exhibited immense potential in improving patient outcomes in prostate cancer with the implementation of [ 68 Ga]Ga-PSMA-11 PET and [ 177 Lu]Lu-PSMA-617 into clinical practice. However, the correlation between radiopharmaceutical biodistributions seen with [ 68 Ga]Ga-PSMA-11 PET imaging and downstream [ 177 Lu]Lu-PSMA-617 therapy remains imperfect. This suggests that prostate cancer theranostics could potentially be further refined through the implementation of true theranostics, tandem pairs of diagnostic and therapeutic radiopharmaceuticals that utilize the same ligand and element, thus yielding identical pharmacokinetics. The radioscandiums are one such group of true theranostic radiopharmaceuticals. The radioscandiums consist of two β+ emitting scandium isotopes ( 43 Sc/ 44 Sc), as well as a β − emitting therapeutic isotope ( 47 Sc), which can all conjugate with PSMA-targeting PSMA-617. This potential has led to extensive investigations into the production of the radioscandiums as well as pre-clinical assessments with several ligands; however, there is a lack of literature extensively describing the complete synthesis of scandium radiopharmaceuticals. which therefore limits the accessibility of radioscandium research in theranostics. As such, this work aims to present an easily translatable protocol for the synthesis of [ 43 Sc]Sc-PSMA-617 from a [ 42 Ca]CaCO 3 starting material, including target formation, nuclear production via 42 Ca(d,n) 43 Sc reaction, chemical separation, radiolabeling, solvent reformulation, and target recycling.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2014

Matching the decay half-life with the biological half-life: ImmunoPET imaging with 44 Sc-labeled Cetuximab Fab fragment

Scandium-44 (t 1/2 = 3.9 h) is a relatively new radioisotope of potential interest for use in clinical positron emission tomography (PET). Herein, we report, for the first time, the room-temperature radiolabeling of proteins with 44 Sc for in vivo PET imaging. For this purpose, the Fab fragment of Cetuximab, a monoclonal antibody that binds with high affinity to epidermal growth factor receptor (EGFR), was generated and conjugated with N -[(R)-2-amino-3-( para -isothiocyanato-phenyl)propyl]- trans -(S,S)-cyclohexane-1,2-diamine- N,N,N',N'',N'' -pentaacetic acid (CHX-A"-DTPA). The high purity of Cetuximab-Fab was confirmed by SDS-PAGE and mass spectrometry. The potential of the bioconjugate for PET imaging of EGFR expression in human glioblastoma (U87MG) tumor-bearing mice was investigated after 44 Sc labeling. PET imaging revealed rapid tumor uptake (maximum uptake of ~12% ID/g at 4 h postinjection) of 44 Sc–CHX-A"-DTPA–Cetuximab-Fab with excellent tumor-to-background ratio, which might allow for same day PET imaging in future clinical studies. Immunofluorescence staining was conducted to correlate tracer uptake in the tumor and normal tissues with EGFR expression. As a result, this successful strategy for immunoPET imaging of EGFR expression using 44 Sc–CHX-''-DTPA–Cetuximab-Fab can make clinically translatable advances to select the right population of patients for EGFR-targeted therapy and also to monitor the therapeutic efficacy of anti-EGFR treatments.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2022

Radiolabeling and in vitro studies of scandium-44 with HOPO chelator for PET imaging

44 Sc has been attracting interest as a clinically viable PET (positron emission tomography) imaging radionuclide due to its high positron branching ratio, 3.97 hour half-life, ideal positron energy of 632 keV and ability to be produced from a generator as well as from a cyclotron. Scandium is also of interest since the coordination is similar to the lanthanides and Ga 3+ that have demonstrated labeling methods. Further, 47 Sc (a potential therapeutic radionuclide) can serve as a matched isotope pair for theranostic applications. While the labeling studies of 44 Sc with DOTA and DOTA derivatives are quite extensive, there is little data on complexation of scandium with the chelator 3,4,3-(LI-1,2-HOPO). This ligand has been used successfully to radiolabel 89 Zr where it was shown to have high stability in vivo. Additionally, preliminary studies with 86 Y, and non-radioactive scandium show promising complexation constants similar to those found with DOTA derivatives. One major advantage of using HOPO is that radiolabeling can be achieved at room temperature while DOTA requires elevated temperatures, that may be detrimental when radiolabeling biomolecules. Radiolabeling of generator produced 44 Sc versus cyclotron produced 44 Sc is also under investigation as there are currently several different post-elution purification methods of generator 44 Sc, and the potential radiolabeling complications of these eluents has not yet been studied. This work focuses on radiolabeling HOPO with generator produced 44 Sc and the in vitro and radioanalytical evaluation of the resulting complexes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Rare earth elements and critical metal content of extracted landfilled material and potential recovery opportunities

Highlights: • Samples from multiple core drills were obtained from 4× landfill sites in the UK. • Each sample analysed for rare earth elements, critical metals and valuable metals. • Two stage microwave digestion method ensuring high yield. • High quantities of copper and aluminium were observed in the soil layers of landfill. • Across 4× landfills aluminium and copper present has a value of around $400 million. - Abstract: Rare earth elements (REEs), Platinum group metals (PGMs) and other critical metals currently attract significant interest due to the high risks of supply shortage and substantial impact on the economy. Their uses in many applications have made them present in municipal solid waste (MSW) and in commercial and industrial waste (C&I), since several industrial processes produce by-products with high content of these metals. With over 4000 landfills in the UK alone, the aim of this study was to assess the existence of these critical metals within landfills. Samples collected from four closed landfills in UK were subjected to a two-step acid digestion to extract 27 metals of interest. Concentrations across the four landfill sites were 58 ± 6 mg kg{sup −1} for REEs comprising 44 ± 8 mg kg{sup −1} for light REEs, 11 ± 2 mg kg{sup −1} for heavy REEs and 3 ± 1 mg kg{sup −1} for Scandium (Sc) and 3 ± 1.0 mg kg{sup −1} of PGMs. Compared to the typical concentration in ores, these concentrations are too low to achieve a commercially viable extraction. However, content of other highly valuable metals (Al and Cu) was found in concentrations equating to a combined value across the four landfills of around $400 million, which increases the economic viability of landfill mining. Presence of critical metals will mainly depend on the type of waste that was buried but the recovery of these metals through landfill mining is possible and is economically feasible only if additional materials (plastics, paper, metallic items and other) are also recovered for reprocessing.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Methods of producing enriched scandium-47, and related systems and apparatuses

A method of producing enriched 47 Sc comprises irradiating a V structure comprising 51 V with at least one incident photon beam having an endpoint energy within a range of from about 14 MeV to about 44 MeV to convert at least some of the 51 V to 47 Sc and form a 47 Sc-containing structure. The 47 Sc of the 47 Sc-containing structure is separated from additional components of the 47 Sc-containing structure using a chromatography process. Systems and apparatuses for producing enriched 47 Sc are also described.

Snow, Mathew S.↗
DOE OSTI2023

Cyclotron production of 43Sc and 44gSc from enriched 42CaO, 43CaO, and 44CaO targets

Introduction: 43 Sc and 44g Sc are both positron-emitting radioisotopes of scandium with suitable half-lives and favorable positron energies for clinical positron emission tomography (PET) imaging. Irradiation of isotopically enriched calcium targets has higher cross sections compared to titanium targets and higher radionuclidic purity and cross sections than natural calcium targets for reaction routes possible on small cyclotrons capable of accelerating protons and deuterons. Methods: In this work, we investigate the following production routes via proton and deuteron bombardment on CaCO 3 and CaO target materials: 42 Ca(d,n) 43 Sc, 43 Ca(p,n) 43 Sc, 43 Ca(d,n) 44g Sc, 44 Ca(p,n) 44g Sc, and 44 Ca(p,2n) 43 Sc. Radiochemical isolation of the produced radioscandium was performed with extraction chromatography using branched DGA resin and apparent molar activity was measured with the chelator DOTA. The imaging performance of 43 Sc and 44g Sc was compared with 18 F, 68 Ga, and 64 Cu on two clinical PET/CT scanners. Discussion: The results of this work demonstrate that proton and deuteron bombardment of isotopically enriched CaO targets produce high yield and high radionuclidic purity 43 Sc and 44g Sc. Laboratory capabilities, circumstances, and budgets are likely to dictate which reaction route and radioisotope of scandium is chosen.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Engineering a modular 44 Ti/ 44 Sc generator: eluate evaluation in preclinical models and estimation of human radiation dosimetry

Background: 44 Sc/ 47 Sc is an attractive theranostic pair for targeted in vivo positron emission tomographic (PET) imaging and beta-particle treatment of cancer. The 44 Ti/ 44 Sc 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 44 Sc. In our current study, we built and evaluated a novel clinical-scale 44 Ti/ 44 Sc generator, explored the pharmacokinetic profiles of 44 ScCl 3 , [ 44 Sc]-citrate and [ 44 Sc]-NODAGA (1,4,7-triazacyclononane,1-glutaric acid-4,7-acetic acid) in naïve mice, and estimated the radiation burden of 44 ScCl 3 in humans. Methods: 44 Ti/ 44 Sc (101.2 MBq) in 6 M HCl solution was utilized to assemble a modular ZR resin containing generator. After assembly, 44 Sc 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 / 47 ScCl 3 in human adults were calculated for 18 organs and tissues using the IDAC-Dose software. Results: 44 Ti in 6 M HCl was loaded onto the organic resin generator with a yield of 99.97%. After loading and initial stabilization, 44 ScCl 3 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 44 Ti loaded on the generator. Run in forward and reverse directions, the 44 Sc/ 44 Ti 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 44 ScCl 3 , [ 44 Sc]-citrate and [ 44 Sc]-NODAGA show that free 44 Sc remained in the circulation significantly longer than the chelated 44 Sc. The dose estimation of 44 ScCl 3 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 44 Ti/ 44 Sc generator system with a modular design was developed to supply 44 ScCl 3 in 0.05 M HCl, which is suitable for further radiolabeling and in vivo use. Our data demonstrated that free 44 ScCl 3 remained in the circulation for extended periods, which resulted in approximately 10 times greater radiation burden than stably chelated 44 Sc. Stable 44 Sc/ 47 Sc-complexation will be more favorable for in vivo use and for clinical utility.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Current State of 44 Ti/ 44 Sc Radionuclide Generator Systems and Separation Chemistry

We report in recent years, there has been an increased interest in 44Ti/44Sc generators as an onsite source of 44Sc for medical applications without needing a proximal cyclotron. The relatively short half-life (3.97 hours) and high positron branching ratio (94.3%) of 44Sc make it a viable candidate for positron emission tomography (PET) imaging. This review discusses current 44Ti/44Sc generator designs, focusing on their chemistry, drawbacks, post-elution processing, and relevant preclinical studies of the 44Sc for potential PET radiopharmaceuticals.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Cross-sections for 43 Sc, 44 m Sc, and 44 g Sc from two heavy ion reactions

Two different heavy ion reactions were used to produce 43 Sc (t$_{\frac12}$ = 3.891 h), 44g Sc (t$_{\frac12}$ = 4.042 h), and 44m Sc (t$_{\frac12}$ = 58.61 h) among other stable or long-lived chemically separable products. Production cross sections for 19 F + 27 Al and the reverse kinematic reaction 35 Cl + nat B were measured using an MC-SNICS ion source and the Notre Dame FN Tandem Accelerator. 19 F beams from 35 to 60 MeV were produced with beam currents between 40–80 pnA and 35 Cl beams were produced at six entrance energies with comparable beam currents. This work reports nuclear reaction cross sections 27 Al ( 19 F, x) 43 Sc, 27 Al ( 19 F, pn) 44g Sc, and 27 Al ( 19 F, pn) 44m Sc at six energies between 35 and 60 MeV lab energy. Cross sections within the same energy range were measured for 27 Al ( 19 F, 3pn) 42 K and 27 Al ( 19 F, 3p) 43 K. Comparative measurements were performed for the same compound nucleus produced from nat B( 35 Cl, x) 43 Sc, nat B( 35 Cl, pn) 44g Sc, and nat B( 35 Cl, pn) 44m Sc. The measured thin target cross sections show an overestimation by several statistical models for the scandium radioisotopes. This is corroborated by the measured thick target production rates for both entrance channels. This may be due to angular momentum effects of a heavy ion entrance channel compared to light-ion production, but additional work is required to understand this discrepancy. Finally, these measurements demonstrate that the medically useful 43 Sc, 44g Sc, and 44m Sc radioisotopes can be free of the long-lived contaminant 46 Sc without the use of enriched targets, using heavy ion beams and robust target materials.

07 ISOTOPE AND RADIATION SOURCES↗