Paul Schaffer

Associate Professor

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Graduate Student Supervision

Doctoral Student Supervision (Jan 2008 - May 2021)
Nuclide production and imaging applications of ??uAc for targeted alpha therapy (2021)

Targeted alpha therapies using actinium-225 (²²⁵Ac, t₁/₂ = 9.9 d) can treat advanced metastatic disease, yet insufficient ²²⁵Ac availability limits their development (63 GBq/year is produced globally via ²²⁹Th generators). This thesis describes efforts to produce ²²⁵Ac and apply multi-nuclide SPECT imaging in preclinical evaluation of ²²⁵Ac-radiopharmaceuticals. Initial ²²⁵Ac production used ᴺᵃᵗU-spallation-produced and mass-separated ion beams, producing up to 8.6 MBq of ²²⁵Ra (an ²²⁵Ac parent) and 18 MBq of ²²⁵Ac. This material helped characterize the performance of ²²⁵Ac decay chain imaging on a microSPECT/PET/CT scanner in terms of contrast recovery, spatial resolution, and noise. Larger ²²⁵Ac quantities were produced via thorium target irradiation with a 438 MeV, 72 μA proton beam for 36 hours, producing (521 ±18) MBq of ²²⁵Ac and (91 ± 14) MBq of ²²⁵Ra. These irradiations enabled ²³²Th(p,x) cross sections measurements for ²²⁵Ac, ²²⁵Ra, and ²²⁷Ac: (13.3 ± 1.2) mb, (4.2 ± 0.4) mb, and (17.7 ± 1.7) mb, respectively. Thirty-five other cross sections were measured and compared to FLUKA simulations; measured and calculated values generally agree within a factor of two. Ac separation from irradiated thorium and co-produced radioactive by-products used a thorium peroxide precipitation followed by cation exchange and extraction chromatography. Studies showed this method separates Ac from most elements, providing a directly-produced Ac product (²²⁷˒²²⁵Ac†) with measured ²²⁷Ac content of (0.15 ± 0.04)%, a hazardous long-lived (t₁/₂ = 21.8 y) impurity with prohibitively low waste disposal limits. A second, indirectly-produced ²²⁵Ra/²²⁵Ac-generator-derived Ac product (²²⁵Ac*) with ²²⁷Ac content of
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Radiofluorinated amino acids for oncological positron emission tomography imaging (2020)

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.

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Current Students & Alumni

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Partner appointment
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