Innovative Target for Production of Technetium-99m by Biomedical Cyclotron

Abstract

Technetium-99m (99mTc) is the most used radionuclide worldwide in nuclear medicine for diagnostic imaging procedures. 99mTc is typically extracted from portable generators containing 99Mo, which is produced normally in nuclear reactors as a fission product of highly enriched Uranium material. Due to unexpected outages or planned and unplanned reactor shutdown, significant 99mTc shortages appeared as a problem since 2008 The alternative cyclotron-based approach through the 100Mo(p,2n)99mTc reaction is considered one of the most promising routes for direct 99mTc production in order to mitigate potential 99Mo shortages. The design and manufacturing of appropriate cyclotron targets for the production of significant amounts of a radiopharmaceutical for medical use is a technological challenge. In this work, a novel solid target preparation method was developed, including sputter deposition of a dense, adherent, and non-oxidized Mo target material onto a complex backing plate. The latter included either chemically resistant sapphire or synthetic diamond brazed in vacuum conditions to copper. The target thermo-mechanical stability tests were performed under 15.6 MeV proton energy and different beam intensities, up to the maximum provided by the available GE Healthcare (Chicago, IL, USA) PET trace medical cyclotron. The targets resisted proton beam currents up to 60 µA (corresponding to a heat power density of about 1 kW/cm2) without damage or Mo deposited layer delamination. The chemical stability of the proposed backing materials was proven by gamma-spectroscopy analysis of the solution obtained after the standard dissolution procedure of irradiated targets in H2O2.

Medical Cyclotron Solid Target Preparation by Ultrathick Film Magnetron Sputtering Deposition

“…Here, we have associated with the group of physical methods different Physical Vapor Deposition (PVD) methods, such as Focused Ion Beam (FIB) or magnetron sputtering, thermal spray deposition, and plasma spray deposition. Table 1 presents a summary of the most commonly used methods for cyclotron solid target preparation and some examples of their [3,[19][20][21][22][23][24] In order to maximize the nuclear reaction yield, production should be performed at maximum proton currents. This means that the target system should provide high efficiency of heat dissipation.…”

“…The LNL-INFN group, in the framework of the LARAMED (LAboratories for RAdioisotopes of MEDical interest) project [25], has proposed to use magnetron sputtering to deposit the target material onto the appropriate backing plate in order to provide high density, high thickness uniformity, and high adherence to the backing. An innovative study of the Mo cyclotron solid target concept for 99m Tc production was recently presented in [3]. This included sputter deposition of Mo target material onto a composite high thermal conductivity and chemical resistance backing plate.…”

“…This included sputter deposition of Mo target material onto a composite high thermal conductivity and chemical resistance backing plate. The previous article [3] was devoted to Mo deposition and the technological aspects of vacuum brazing to realize a composite backing plate. The scope of the present work is instead focused on the deposition method development.…”

Recovery of Molybdenum Precursor Material in the Cyclotron-Based Technetium-99m Production Cycle

“…Mo-sputtered layer onto a complex backing plate (patent PCT/IB2018/056826) [13,14]. • HIVIPP (HIgh energy VIbrational Powders Plating) electrostatic deposition [15] of Mo onto metallic backing with a high yield deposition efficiency (>95%) and uniformity, but limited thickness (2-3 µm).…”

Molybdenum Sinter-Cladding of Solid Radioisotope Targets

“…In the case of molybdenum, a number of cladding techniques were used, including rolling the molybdenum into thin foils and soldering or pressure/diffusion-bonding those to the substrate, laser cladding, electrophoretic deposition, plasma spraying, powder pressing, hot isostatic pressing, among others. Some of these studies are referenced as background material [1][2][3][4][5][6][7][8][9][10].…”