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

Abstract

Cyclotron production of 99m Tc is a promising route to supply 99m Tc radiopharmaceuticals. Higher 99m Tc 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 99m Tc produced at medium energy (20)(21)(22)(23)(24) and its impact on image quality and dosimetry was required. Methods: Thick 100 Mo (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 99m Tc was assayed for chemical, radiochemical, and radionuclidic purity. Radioisotopic content in final formulation was quantified using g-ray spectrometry. The internal radiation dose for 99m Tc-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 99m Tc 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 99m Tc produced with 99.03% enriched 100 Mo was greater than 99.0% decay corrected to the end of bombardment (EOB). The radioisotopic purity of 99m Tc produced with 99.815% enriched 100 Mo was 99.98% or greater (decay corrected to the EOB). The estimated dose increase relative to 99m Tc without any radionuclidic impurities was below 10% for sodium pertechnetate 99m Tc produced from 99.03% 100 Mo if injected up to 6 h after the EOB. For 99.815% 100 Mo, 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 99m Tc were equivalent to those obtained with 99m Tc eluted from a conventional generator. Conclusion: Clinical-grade sodium pertechnetate 99m Tc 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 99m Tc in routine clinical practice. The radioisotope 99m Tc remains indispensable in nuclear imaging. 99m Tc is usually obtained from generators containing the mother isotope, 99 Mo, which in turn is made from highly enriched 235 U ($20%, typically 93%) in nuclear reactors. 99m Tc is eluted in the form of sodium pertechnetate and can be used as is or as the starting material for other 99m Tc radiopharmaceuticals used in a variety of diagnostic applications. Cyclotron production of 99m Tc could be a viable alternativ...

OPTIMASI pH ALUMINA dan 99Mo DALAM PEMBUATAN GENERATOR 99Mo/99mTc BERBASIS MoO3 ALAM

“…Bahan alumina sebagai bahan penyerap radioisotop 99 Mo saat ini penggunaanya sudah mulai digantikan dengan material lain yang berbasis polimer seperti material berbasis zirkonium(MBZ) dan material berbasis nano partikel [4,5,6,7,8].…”

Internal radiation dose assessment of radiopharmaceuticals prepared with cyclotron‐produced 99mTc

“…Using a proton beam of 15.7 MeV and an enriched Isoflex Mo target (99.05%), just 0.0267% of the total activity was related to 96 Tc (see Table ) . Selivanova et al . reported a 96 Tc concentration in the Tc‐final product of 0.0695%, 0.1478%, and 0.1614% using the same type of Mo target and proton beams of 20, 22, and 24 MeV, respectively.…”

“…However, we believe that these limits apply to large‐scale 99m Tc production after few hours of irradiation and using 20–24 MeV proton beams. Under these conditions, very high‐enriched targets (99.815% at least) must be used to maintain the dose under the above‐mentioned limit, as demonstrated by Selivanova et al . In this work, 99m Tc in‐house production was achieved using a less expensive 100 Mo metallic target with lower enrichment level (99.05%), shorter irradiation times (1 h), and already available conventional low‐energy medical cyclotron (16 MeV).…”

Synthesis and preliminary biological evaluation of a99mTc-chlorambucil derivative as a potential tumor imaging agent

“…Furthermore, it is acknowledged that the development of technetium‐labeled complexes as radiopharmaceuticals has been facilitated by the use of rhenium, the group VIIB congener of technetium. Rhenium chemistry is similar to technetium‐99m chemistry, and therefore, nonradioactive metal complexes are often used as mimics of 99m Tc‐analogs, with the practical advantage that larger scale syntheses can yield quantities of product for structural characterization . In this study, the rhenium‐complex 4 was synthesized in sufficient quantity from DPA‐CLB ( 2 ) in 75% yield via Scheme , it was characterized by elemental analysis and a mix of different spectroscopic methods.…”