SIR 2024
Imaging
Haneyeh Shahbazian, MD (she/her/hers)
Research Fellow
University of North Carolina
Financial relationships: Full list of relationships is listed on the CME information page.
David Brandon, MD
Associate Professor, Department of Radiology and Imaging Sciences
Emory University School of Medicine
Disclosure information not submitted.
David Schuster, MD
Professor
Emory University School of Medicine
Disclosure information not submitted.
Cheenu Kappadath, PhD
Professor
University of Texas MD Anderson Cancer Center
Disclosure information not submitted.
Ila Sethi, MD
Assistant Professor of Nuclear Medicine and Molecular Imaging
Emory School of Medicine
Disclosure information not submitted.
Nima Kokabi, MD
Associate Professor of Radiology
University of North Carolina - Chapel Hill
Financial relationships: Full list of relationships is listed on the CME information page.
Post-Y90 dosimetry analysis has been used to ensure delivery of tumoricidal dose. However, there are fundamental differences in quantification of Y90 dose using positron emission tomography (PET)/computed tomography (CT) versus single-photon emission computed tomography (SPECT)/CT. The aim of this study was to further investigate these differences and identity potential correlations between these quantitative methods.
Materials and Methods:
In a prospective single-center clinical trial with the primary aim of evaluating the feasibility of scout activity for resin-based Y90 for treatment planning (NCT04172714), patients with treatment naïve HCC were recruited. A secondary aim of the study was to evaluate dosimetry differences between Y90 PET/CT and Y90 SPECT/CT. All patients underwent both PET and SPECT after scout and therapeutic resin Y90. 3D voxel-based dosimetry for the targeted tumors and the perfused liver was performed with MIM Sureplan® (MIM Software, Cleveland, OH, USA) using cumulative scout and therapeutic activities. Paired t-tests were used compare dosimetry variables. Pearson linear correlations between corresponding parameters calculated by PET and SPECT were also performed. All statistical analyses were performed using SPSS v.28 (IBM, Armonk, NY, USA).
Results:
Overall, N=30 patients (33 tumors) were treated. Mean tumor dose (TD) was significantly higher on PET compared to SPECT/CT (493 Gy vs. 366 Gy) p< 0.001). Similarly, minimum TD (197 Gy vs. 179 Gy), maximum TD (966 Gy. 591 Gy), mean tumor dose to top 30% (TD-V30) (594 Gy vs. 408 Gy), and 70% (TD-V70) of tumor volume (405 Gy vs. 326 Gy) were significantly higher on PET/CT versus SPECT/CT (p-values< 0.001). Moreover, there was a strong linear correlation between corresponding tumor dose variables on PET/CT and SPECT/CT (r coefficients >0.9; p-values< 0.001). Conversely, mean non-tumoral liver dose (NTLD) was significantly higher on Y90 SPECT/CT vs. PET/CT (181 Gy vs. 103 Gy; p< 0.001). Similarly, minimum, maximum, V-30 and V-70 NTLD were higher on SPECT versus PET, although only statistically significant for V-70 (p< 0.001). There was a strong linear correlation between mean NTLD on SPECT/CT vs. PET/ CT (r=0.9; p< 0.001).
Conclusion:
PET/CT and SPECT/CT demonstrated significant differences in Y90 dose quantification. Specifically, tumor doses were observed to be higher on Y90 PET/CT than on Y90 SPECT/CT, while non-tumoral liver doses were observed to be lower on Y90 PET/CT than on Y90 SPECT/CT. Further investigation on post-Y90 PET/CT and SPECT/CT thresholds is warranted to ensure optimal treatment response.