High quality imaging and dosimetry for yttrium-90 (90Y) liver radioembolization using a SiPM-based PET/CT scanner

Purpose Transarterial radioembolization (TARE) with yttrium-90 (Y-90) microspheres is a liver-directed treatment for primary and secondary hepatic malignancies. Personalized dosimetry aims for maximum treatment effect and reduced toxicity. We aimed to compare pre-treatment voxel-based dosimetry from Tc-99m macroaggregated albumin (MAA) SPECT/CT with post-treatment Y-90 PET/CT for absorbed dose values, and to evaluate image quality of Y-90 SiPM-based PET/CT. Methods Forty-two patients (28 men, 14 women, mean age: 67 +/- 11 years) with advanced hepatic malignancies were prospectively enrolled. Twenty patients were treated with glass and 22 with resin microspheres. Radiation absorbed doses from planning Tc-99m-MAA SPECT/CT and post-therapy Y-90 PET/CT were assessed. Y-90 PET/CT images were acquired for 20 min and reconstructed to produce 5-, 10-, 15-, and 20-min datasets, then evaluated using the 5-point Likert scale. Results The mean administered activity was 3.44 +/- 1.5 GBq for glass and 1.62 +/- 0.7 GBq for resin microspheres. The mean tumor absorbed doses calculated from Tc-99m-MAA SPECT/CT and Y-90 PET/CT were 175.69 +/- 113.76 Gy and 193.58 +/- 111.09 Gy (P = 0.61), respectively for glass microspheres; they were 60.18 +/- 42.20 Gy and 70.98 +/- 49.65 Gy (P = 0.37), respectively for resin microspheres. The mean normal liver absorbed doses from Tc-99m-MAA SPECT/CT and Y-90 PET/CT were 32.70 +/- 22.25 Gy and 30.62 +/- 20.09 Gy (P = 0.77), respectively for glass microspheres; they were 18.33 +/- 11.08 Gy and 24.32 +/- 15.58 Gy (P = 0.17), respectively for resin microspheres. Image quality of Y-90 PET/CT at 5-, 10-, 15-, and 20-min scan time showed a Likert score of 3.6 +/- 0.54, 4.57 +/- 0.58, 4.84 +/- 0.37, and 4.9 +/- 0.3, respectively. Conclusions Tc-99m-MAA SPECT/CT demonstrated great accuracy for treatment planning dosimetry. SiPM-based PET/CT scanner showed good image quality at 10-min scan time, acquired in one bed position. A PET/CT scan time of 5 min showed acceptable image quality and suffices for dosimetry and treatment verification. This allows for inclusion of Y-90 PET/CT in busy routine clinical workflows. Studies with larger patient cohorts are needed to confirm these findings.

Automated summary

Tc-99m-MAA SPECT/CT showed great accuracy for treatment planning dosimetry. The SiPM-based PET/CT scanner demonstrated good image quality at a 10-min scan time in one bed position. A 5-min PET/CT scan time revealed acceptable image quality, which is sufficient for dosimetry and treatment verification.