[Triumf-seminars] TRIUMF Colloquium today at 14:00

[TRIUMF Seminars]

Date/Time: Thu 2015-04-23 at 14:00

Location:  Auditorium          

Speaker:   Valery Radchenko (Los Alamos)

Title:     Production of medical radionuclides at the Los Alamos National Laboratory

Abstract: 1. Selective isolation of Pa and Ac isotopes from irradiated thorium targets. Actinium-225 (t1/2 = 9.92 d) is an alpha-emitting radionuclide with nuclear properties well-suited for use in targeted alpha therapy (TAT) [1], a potent treatment method for malignant tumors. The isotope can be used directly or as a generator source of 213Bi (t1/2 = 45.6 min), which, in turn, is a promising therapeutic radionuclide[2].  Uranium-230 (t1/2 = 20.8 d) is another attractive radionuclide for possible TAT use. It can be obtained via the decay of 230Pa (t1/2 = 17.4 d) and then used either directly in combination with selective delivery agents or as a generator source of much shorter-lived 226Th (t1/2 = 31.0 min), which has recently been receiving attention as a potential therapy nuclide [3]. One viable way of producing both actinium-225 and protactinium-230 is the proton irradiation of thorium [4], however, the radiochemical isolation of these valuable radionuclides poses some challenge due to the co-formation of radiolanthanides and other 232Th (p,f) fission products. The efficient separation of excess thorium mass from the desired isotope products must also be considered. A selective and elegant methodology for the recovery of Pa and Ac isotopes has been developed at LANL, which is based on a combination of ion exchange and solid phase extraction chromatography [5].

2. 44Ti/44Sc production at lower proton energies
The 44Ti/44Sc radionuclide generator system offers an accelerator-independent source of 44Sc (t1/2 = 3.97 h), a radionuclide useful for positron emission tomography (PET) imaging of slower metabolic processes [6, 7]. The principle limiting factor in the availability of 44Ti/44Sc is the slow rate at which the parent radionuclide 44Ti (t1/2 = 60 y) can be produced. Formation of 44Ti via the 45Sc(p,2n)44Ti nuclear reaction affords the highest production rate among those available., Scandium metal was chosen as a target for the eventual development of high proton intensity (230 muA) irradiation schemes. Two targets were fabricated and one of them was placed into low proton energy beam slot at the Los Alamos Isotope Production Facility (LANL-IPF) during the past IPF run cycle (2014-2015). A 10 day irradiation with protons of < 35 MeV incidental energy resulted in the production of approximately 5 mCi of 44Ti. Some details associated with target design and target processing will be discussed.

References:
1. A. Morgenstern, et al., Curr Radiopharm. 5(3) (2012) 221.
2. M. Miederer et al., Adv Drug Deliv Rev. 60(12), (2008), 1371.
3. J. W. Engle et al., Phys. Rev. 88 (2013) 014604.
4. V. Radchenko et al, J. Crom. A 1380, (2015), 55.
5. C. Duchemin, et al. J. Nucl Med Biol. 41 Suppl (2014)e19-22.
6. F. Roesch et al. Curr Radiopharm. 5(