Quantitative SPECT/CT imaging of actinium-225 for targeted alpha therapy of glioblastomas

Monika Tulik; Radosław Kuliński; Zbisław Tabor; Beata Brzozowska; Piotr Łaba; Frank Bruchertseifer; Alfred Morgenstern; Leszek Królicki; Jolanta Kunikowska

doi:10.1186/s40658-024-00635-1

Quantitative SPECT/CT imaging of actinium-225 for targeted alpha therapy of glioblastomas

EJNMMI Phys. 2024 May 9;11(1):41. doi: 10.1186/s40658-024-00635-1.

Authors

Monika Tulik¹, Radosław Kuliński², Zbisław Tabor³, Beata Brzozowska⁴, Piotr Łaba⁴, Frank Bruchertseifer⁵, Alfred Morgenstern⁵, Leszek Królicki², Jolanta Kunikowska²

Affiliations

¹ Department of Nuclear Medicine, Medical University of Warsaw, Warsaw, Poland. monika.tulik@wum.edu.pl.
² Department of Nuclear Medicine, Medical University of Warsaw, Warsaw, Poland.
³ Faculty of Electrical Engineering, Computer Science, and Biomedical Engineering, AGH University of Science and Technology, Krakow, Poland.
⁴ Biomedical Physics Division, Faculty of Physics, University of Warsaw, Warsaw, Poland.
⁵ Joint Research Centre, European Commission, Karlsruhe, Germany.

Abstract

Background: A new, alternative option for patients with recurrent glioblastoma is targeted alpha therapy (TAT), in the form of a local administration of substance P (neurokinin type 1 receptor ligand, NK-1) labelled with ²²⁵Ac. The purpose of the study was to confirm the feasibility of quantitative SPECT imaging of ²²⁵Ac, in a model reproducing specific conditions of TAT. In particular, to present the SPECT calibration methodology used, as well as the results of validation measurements and their accuracy. Additionally, to discuss the specific problems related to high noise in the presented case.

Materials and methods: All SPECT/CT scans were conducted using the Symbia T6 equipped with HE collimators, and acquired with multiple energy windows (three main windows: 440 keV, 218 keV, and 78 keV, with three lower scatter energy windows). A Jaszczak phantom with fillable cylindrical sources of various sizes was used to investigate quantitative SPECT/CT imaging characteristics. The planar sensitivity of the camera, an imaging calibration factor, and recovery coefficients were determined. Additionally, the 3D printed model of the glioblastoma tumour was developed and imaged to evaluate the accuracy of the proposed protocol.

Results: Using the imaging calibration factor and recovery coefficients obtained with the Jaszczak phantom, we were able to quantify the activity in a 3D-printed model of a glioblastoma tumour with uncertainty of no more than 10% and satisfying accuracy.

Conclusions: It is feasible to perform quantitative ²²⁵Ac SPECT/CT imaging. However, there are still many more challenges that should be considered for further research on this topic (among others: accurate determination of ICF in the case of high background noise, better method of background estimation for recovery coefficient calculations, other methods for scatter correction than the dual-energy window scatter-compensation method used in this study).

Keywords: Actinium-225; Dosimetry; Glioblastoma; Quantitative imaging; SPECT/CT.