Reliable (accurate and precise) quantification of dose requires reliable absolute quantification of regional activity uptake. This is especially challenging for alpha-particle emitting radiopharmaceutical therapies due to the complex emission spectra, the very low number of detected counts, the impact of stray-radiation-related noise at these low counts, and other image-degrading processes such as attenuation, scatter, and collimator-detector response. To address these challenges, we are developing ultra-low-count quantitative SPECT methods that  directly estimates the regional activity uptake from the projection data, obviating the reconstruction step. This makes the problem more well-posed and avoids reconstruction-related information loss. These methods compensate for radioisotope and SPECT physics, including the isotope spectra, scatter, attenuation, and collimator-detector response, using Monte Carlo-based approaches. Our results based on validations with physical phantoms and virtual imaging trials are showing the accurate performance of these methods, as detailed in the references below.


  • Z. Li, N. Benabdallah, D. Thorek, A. K. Jha, “A multiple-energy-window projection-domain quantitative SPECT method for joint regional uptake quantification of Th-227 and Ra-223”, Proceedings of the International Conference on Fully Three-Dimensional Image Reconstruction in Radiology and Nuclear Medicine, 2021 (Oral Award Nominee)
  • Z. Li, N. Benabdallah, D. Abou, B. Baumann, R. Wahl, D. Thorek, A. K. Jha, “A projection domain low-count quantitative SPECT method for alpha-particle emitting radiopharmaceutical therapy” (pre-print)
  • N Benabdallah, W Scheve, N Dunn, D Silvestros, P Schelker, R Laforest, R F Hobbs, Z Li, N M Maughan, U Jammalamadaka, J Michalski, B C Baumann, B Rogers, H Gay, D Abou, A Iravani, K. Jha, F. Dehdashti, D. L. J. Thorek, “Practical considerations for quantitative clinical SPECT/CT imaging of alpha particle emitting radioisotopes”, Theranostics
  • Z. Li, N. Benabdallah, D. Abou, B. Baumann, R. Wahl, D. Thorek, A. K. Jha, “A projection-domain quantification method for absolute quantification with low-count SPECT for alpha-particle radiopharmaceutical therapy”, Journal of Nuclear Medicine May 2021, 62 (supplement 1) 1539 (Best poster award nominee)
  • D. S. Abou, A. Rittenbach, R. E. Tomlinson, P. A. Finley, B. Tsui, B. W. Simons, A. K. Jha, D. Ulmert, R. C. Riddle, and D. L.J. Thorek, “Preclinical Single Photon Emission Computed Tomography of Alpha Particle-Emitting Radium-223”, Cancer Biotherapy & Radiopharmaceuticals, 35(7), pp. 520-529, 2020