Electron-phonon coupling in copper intercalated Bi[Formula: see text]Se[Formula: see text].

We report charge and heat transport studies in copper-intercalated topological insulator Bi[Formula: see text]Se[Formula: see text] hybrid devices. Measured conductivity shows impact of quantum corrections, electron-electron and electron-phonon interactions. Our shot noise measurements reveal that heat flux displays a crossover between [Formula: see text] and [Formula: see text] with the increase of temperature. The results might be explained by a model of inelastic electron scattering on disorder, increasing the role of transverse acoustic phonons in the electron-phonon coupling process.

Production of Zr-89 using sputtered yttrium coin targets 89Zr using sputtered yttrium coin targets.

An increasing interest in zirconium-89 (89Zr) can be attributed to the isotope's half-life which is compatible with antibody imaging using positron emission tomography (PET). The goal of this work was to develop an efficient means of production for 89Zr that provides this isotope with high radionuclidic purity and specific activity. We investigated the irradiation of yttrium sputtered niobium coins and compared the yields and separation efficiency to solid yttrium coins. The sputtered coins were irradiated with an incident beam energy of 17.5MeV or 17.8MeV providing a degraded transmitted energy through an aluminum degrader of 12.5MeV or 12.8MeV, respectively, with various currents to determine optimal cyclotron conditions for 89Zr production. Dissolution of the solid yttrium coin took 2h with 50mL of 2M HCl and dissolution of the sputtered coin took 15-30min with 4mL of 2M HCl. During the separation of 89Zr from the solid yttrium coins, 77.9 ± 11.2% of the activity was eluted off in an average of 7.3mL of 1M oxalic acid whereas for the sputtered coins, 91 ± 6% was eluted off in an average of 1.2mL of 1M oxalic acid with 100% radionuclidic purity. The effective specific activity determined via DFO-SCN titration from the sputtered coins was 108±7mCi/µmol as compared to 20.3mCi/µmol for the solid yttrium coin production. ICP-MS analysis of the yttrium coin and the sputtered coins showed 99.99% yttrium removed with 178µg of yttrium in the final solution and 99.93-100% of yttrium removed with remaining range of 0-42µg of yttrium in the final solution, respectively. The specific activity calculated for the solid coin and 3 different sputtered coins using the concentration of Zr found via ICP-MS was 140±2mCi/µmol, 300±30mCi/µmol, 410±60mCi/µmol and 1719±5mCi/µmol, respectively. Labeling yields of the 89Zr produced via sputtered targets for 89Zr- DFO-trastuzumab were >98%. Overall, these results show the irradiation of yttrium sputtered niobium coins is a highly effective means for the production of 89Zr.

Radioisotopic Purity of Sodium Pertechnetate 99mTc Produced with a Medium-Energy Cyclotron: Implications for Internal Radiation Dose, Image Quality, and Release Specifications.

UNLABELLED: Cyclotron production of 99mTc is a promising route to supply 99mTc radiopharmaceuticals. Higher 99mTc yields can be obtained with medium-energy cyclotrons in comparison to those dedicated to PET isotope production. To take advantage of this capability, evaluation of the radioisotopic purity of 99mTc produced at medium energy (20-24 MeV) and its impact on image quality and dosimetry was required. METHODS: Thick 100Mo (99.03% and 99.815%) targets were irradiated with incident energies of 20, 22, and 24 MeV for 2 or 6 h. The targets were processed to recover an effective thickness corresponding to approximately 5-MeV energy loss, and the resulting sodium pertechnetate 99mTc was assayed for chemical, radiochemical, and radionuclidic purity. Radioisotopic content in final formulation was quantified using γ-ray spectrometry. The internal radiation dose for 99mTc-pertechnetate was calculated on the basis of experimentally measured values and biokinetic data in humans. Planar and SPECT imaging were performed using thin capillary and water-filled Jaszczak phantoms. RESULTS: Extracted sodium pertechnetate 99mTc met all provisional quality standards. The formulated solution for injection had a pH of 5.0-5.5, contained greater than 98% of radioactivity in the form of pertechnetate ion, and was stable for at least 24 h after formulation. Radioisotopic purity of 99mTc produced with 99.03% enriched 100Mo was greater than 99.0% decay corrected to the end of bombardment (EOB). The radioisotopic purity of 99mTc produced with 99.815% enriched 100Mo was 99.98% or greater (decay corrected to the EOB). The estimated dose increase relative to 99mTc without any radionuclidic impurities was below 10% for sodium pertechnetate 99mTc produced from 99.03% 100Mo if injected up to 6 h after the EOB. For 99.815% 100Mo, the increase in effective dose was less than 2% at 6 h after the EOB and less than 4% at 15 h after the EOB when the target was irradiated at an incident energy of 24 MeV. Image spatial resolution and contrast with cyclotron-produced 99mTc were equivalent to those obtained with 99mTc eluted from a conventional generator. CONCLUSION: Clinical-grade sodium pertechnetate 99mTc was produced with a cyclotron at medium energies. Quality control procedures and release specifications were drafted as part of a clinical trial application that received approval from Health Canada. The results of this work are intended to contribute to establishing a regulatory framework for using cyclotron-produced 99mTc in routine clinical practice.

Assessment of radionuclidic impurities in cyclotron produced (99m)Tc.

INTRODUCTION: The commercial viability of cyclotron-produced (99m)Tc as an alternative to generator-produced (99m)Tc depends on several factors. These include: production yield, ease of target processing and recycling of (100)Mo, radiochemical purity, specific activity as well as the presence of other radionuclides, particularly various Tc radioisotopes that cannot be separated chemically and will remain in the final clinical preparation. These Tc radionuclidic impurities are derived from nuclear interactions of the accelerated protons with other stable Mo isotopes present in the enriched (100)Mo target. The aim of our study was to determine experimentally the yields of Tc radioisotopes produced from these stable Mo isotopes as a function of incident beam energy in order to predict radionuclidic purity of (99m)Tc produced in highly enriched (100)Mo targets of known isotopic composition. METHODS: Enriched molybdenum targets of (95)Mo, (96)Mo, (97)Mo, (98)Mo and (100)Mo were prepared by pressing powdered metal into an aluminum target support. The thick targets were bombarded with 10 to 24MeV protons using the external beam line of the U-120M cyclotron of the Nuclear Physics Institute, Rez. The thick target yields of (94)Tc, (94m)Tc, (95)Tc, (95m)Tc, (96m+g)Tc and (97m)Tc were derived from their activities measured by γ spectrometry using a high purity Ge detector. These data were then used to assess the effect of isotopic composition of highly enriched (100)Mo targets on the radionuclidic purity of (99m)Tc as a function of proton beam energy. Estimates were validated by comparison to measured activities of Tc radioisotopes in proton irradiated, highly enriched (100)Mo targets of known isotopic composition. RESULTS: The measured thick target yields of (94)Tc, (94m)Tc, (95)Tc, (95m)Tc, (96m+g)Tc and (97m)Tc correspond well with recently published values calculated via the EMPIRE-3 code. However, the measured yields are more favourable with regard to achievable radionuclidic purity of (99m)Tc. Reliability of the measured thick target yields was demonstrated by comparison of the estimated and measured activities of (94)Tc, (95)Tc, (95m)Tc, and (96m+g)Tc in highly enriched (100)Mo (99%) targets that showed good agreement, with maximum differences within estimated uncertainties. Radioisotopes (94m)Tc and (97m)Tc were not detected in the irradiated (100)Mo targets due to their low activities and measurement conditions; on the other hand we detected small amounts of the short-lived positron emitter (93)Tc (T(½)=2.75h). In addition to (99m)Tc and trace amounts of the various Tc isotopes, significant activities of (96)Nb, (97)Nb and (99)Mo were detected in the irradiated (100)Mo targets. CONCLUSIONS: Radioisotope formation during the proton irradiation of Mo targets prepared from different, enriched stable Mo isotopes provides a useful data base to predict the presence of Tc radionuclidic impurities in (99m)Tc derived from proton irradiated (100)Mo targets of known isotopic composition. The longer-lived Tc isotopes including (94)Tc (T(½)=4.883h), (95)Tc (T(½)=20.0h), (95m)Tc (T(½)=61 d), (96m+g)Tc (T(½)=4.24 d) and (97m)Tc (T(½)=90 d) are of particular concern since they may affect the dosimetry in clinical applications. Our data demonstrate that cyclotron production of (99m)Tc, using highly enriched (100)Mo targets and 19-24MeV incident proton energy, will result in a product of acceptable radionuclidic purity for applications in nuclear medicine.