Measure of 90Y-glass microspheres residue post-TARE using PET/CT and potential impact on tumor absorbed dose in comparison 99mTc-MAA SPECT/CT dosimetry

Background Transarterial radio-embolization (TARE) became a routine procedure for non-resectable liver tumor mainly hepatocellular carcinoma (HCC). Personalized dosimetry to the index lesion increased tumor response rate. However, there is no requirement to measure the precise activity injected during TARE. We measured 90 Y-glass microspheres residue ( 90 Y-Res) in the application system after TARE and assessed its potential impact on the tumor absorbed dose (AD) previously planned with 99m Tc MAA SPECT/CT. Methods We measured 90 Y-Res using PET/CT in all patients that underwent TARE using 90 Y-glass-microspheres for non-resectable liver tumors over one year. Results 90 Y-Res was measured in 34 patients (HCC n = 22) with 61 injections, 93.1 ± 94.6 MBq [2–437] that was 4.8 ± 3.5% [0.2–13.7] in comparison to the activity measured in the sealed TheraSphere™ vial (ρ = 0.697; p < 0.001). Conclusion We reported an average of 5% 90 Y-Res using PET/CT after TARE with the strongest association to the activity in the TheraSphere™ vial. Therefore, when a high 90 Y-Res is suspected on the survey meter, a 90 Y-PET/CT scan of 90 Y-Res might be useful as a first step to estimate if the target lesion received the recommended AD, especially in HCC patients with borderline tumor dosimetry on the pre-treatment 99m Tc-MAA SPECT/CT.