Theranostics 2021; 11(20):9721-9737. doi:10.7150/thno.63860 This issue
Practical considerations for quantitative clinical SPECT/CT imaging of alpha particle emitting radioisotopes
1. Department of Radiology, Washington University School of Medicine, St. Louis, Missouri.
2. Program in Quantitative Molecular Therapeutics, Washington University School of Medicine, St. Louis, Missouri.
3. Barnes-Jewish Hospital, St. Louis, Missouri.
4. Department of Biomedical Engineering, Washington University, St. Louis, Missouri.
5. Department of Radiation Oncology, Washington University School of Medicine, St. Louis, Missouri.
6. Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland.
7. Oncologic Imaging Program, Alvin J. Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri.
Benabdallah N, Scheve W, Dunn N, Silvestros D, Schelker P, Abou D, Jammalamadaka U, Laforest R, Li Z, Liu J, Ballard DH, Maughan NM, Gay H, Baumann BC, Hobbs RF, Rogers B, Iravani A, Jha AK, Dehdashti F, Thorek DLJ. Practical considerations for quantitative clinical SPECT/CT imaging of alpha particle emitting radioisotopes. Theranostics 2021; 11(20):9721-9737. doi:10.7150/thno.63860. Available from https://www.thno.org/v11p9721.htm
Rationale: Alpha particle emitting radiopharmaceuticals are generating considerable interest for the treatment of disseminated metastatic disease. Molecular imaging of the distribution of these agents is critical to safely and effectively maximize the clinical potential of this emerging drug class. The present studies aim to investigate the feasibility and limitations of quantitative SPECT for 223Ra, 225Ac and 227Th.
Methods: Three state-of-the-art SPECT/CT systems were investigated: the GE Discovery NM/CT 670, the GE Optima NM/CT 640, and the Siemens Symbia T6. A series of phantoms, including the NEMA IEC Body phantom, were used to compare and calibrate each camera. Additionally, anthropomorphic physical tumor and vertebrae phantoms were developed and imaged to evaluate the quantitative imaging protocol.
Results: This work describes and validates a methodology to calibrate each clinical system. The efficiency of each gamma camera was analyzed and compared. Using the calibration factors obtained with the NEMA phantom, we were able to quantify the activity in 3D-printed tissue phantoms with an error of 2.1%, 3.5% and 11.8% for 223Ra, 225Ac, and 227Th, respectively.
Conclusion: The present study validates that quantitative SPECT/CT imaging of 223Ra, 225Ac, and 227Th is achievable but that careful considerations for camera configuration are required. These results will aid in future implementation of SPECT-based patient studies and will help to identify the limiting factors for accurate image-based quantification with alpha particle emitting radionuclides.
Keywords: radiopharmaceutical therapies, quantitative SPECT/CT, Radium-223, Actinium-225, Thorium-227