@article {Costajnumed.121.263145, author = {Gustavo Coelho Alves Costa and Benjamin A. Spencer and Negar Omidvari and Cameron Foster and Michael Rusnak and Heather Hunt and Denise T Caudle and Rex Pillai and Catherine Vu and Emilie Roncali}, title = {Radioembolization Dosimetry with Total-Body 90Y PET}, elocation-id = {jnumed.121.263145}, year = {2021}, doi = {10.2967/jnumed.121.263145}, publisher = {Society of Nuclear Medicine}, abstract = {Introduction: Transarterial radioembolization (TARE) is a loco-regional radiopharmaceutical therapy based on the delivery of radioactive yttrium-90 (90Y) microspheres to liver tumors. The importance of personalized dosimetry to make TARE safer and more effective has been demonstrated in recent clinical studies, stressing the need for quantification of the dose-response relationship to ultimately optimize the administered activity pre-treatment and image it post-treatment. 90Y dosimetric studies are challenging due to the lack of accurate and precise methods but best realized with positron emission tomography combined with Monte Carlo simulations and other image modalities to calculate a segmental dose distribution. Methods: Two PET/CT scanners were evaluated in this study: the Biograph mCT and the total-body uEXPLORER. The reconstructions of a NEMA IQ phantom and two patient images were performed using our standard clinical oncology protocol. A late portal phase CECT was used to contour the liver segments and create corresponding volumes of interest. To calculate the absorbed dose, Monte Carlo simulations were carried out using GATE. The absorbed dose and the dose volume histograms were calculated for all six spheres (diameters ranging from 10 mm to 37 mm) of the NEMA phantom, the liver segments, and the entire liver. The difference between the phantom doses and an analytical ground truth were quantified through the root mean squared error. Results: The uEXPLORER showed a higher signal to noise ratio at 10 mm and 13 mm diameter, consistent with its high spatial resolution and system sensitivity. The total liver absorbed dose showed excellent agreement between the uEXPLORER and the mCT for both patients, with differences lower than 0.2\%. Larger differences were observed when comparing the liver segment doses. All DVH were in good agreement, with narrower tails for the uEXPLORER in all segments, indicating a lower image noise. Conclusion: This patient study is compelling for the use of total-body 90Y PET for liver dosimetry. The uEXPLORER scanner showed a better signal-to-noise ratio than mCT especially in lower count regions of interest, which is expected to improve dose quantification and tumor dosimetry.}, issn = {0161-5505}, URL = {https://jnm.snmjournals.org/content/early/2021/11/18/jnumed.121.263145}, eprint = {https://jnm.snmjournals.org/content/early/2021/11/18/jnumed.121.263145.full.pdf}, journal = {Journal of Nuclear Medicine} }