TY - JOUR T1 - Yttrium-90 imaging with Digital Photon Counting PET/CT: An intra-individual comparison with conventional photomultiplier tube-based PET/CT following radioembolization JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 600 LP - 600 VL - 59 IS - supplement 1 AU - Chadwick Wright AU - Katherine Binzel AU - Jun Zhang AU - Evan Wuthrick AU - Eric Miller AU - Michael Knopp Y1 - 2018/05/01 UR - http://jnm.snmjournals.org/content/59/supplement_1/600.abstract N2 - 600Objectives: There remains an unmet clinical need for improved imaging assessment of intrahepatic Yttrium-90 (90Y) microsphere biodistribution following radioembolization. At present, post-radioembolization imaging assessment is commonly performed using bremsstrahlung SPECT/CT but this approach is limited by poor image quality and lack of quantitative accuracy due to scatter radiation. Conventional photomultiplier tube-based PET (cPET) imaging of 90Y internal pair production enables better image quality but often at the expense of longer image acquisition times. It has been demonstrated that 90Y imaging with next-generation digital photon counting PET/CT (dPET/CT) is clinically feasible in post-radioembolization patients with imaging times comparable to bremsstrahlung SPECT/CT. The objective of this study is to qualitatively and quantitatively assess intrahepatic 90Y microsphere distribution following radioembolization using dPET/CT and compare to cPET/CT. Methods: In a Phase I intra-individual comparison trial, pre-radioembolization 99mTc MAA SPECT/CT and post-therapy bremsstrahlung 90Y SPECT/CT imaging of the liver was performed (Symbia, Siemens) in 25 patients who were routinely treated with 90Y glass microspheres for hepatic malignancies/metastases. Investigational 90Y dPET/CT (Vereos, Philips) and cPET/CT (Gemini, Philips) imaging was performed with Time-of-Flight using shorter total imaging acquisition times (21 min for PET/CT vs 22 min for SPECT/CT) in each patient up to 48 hrs following radioembolization. Image quality of dPET/CT and cPET/CT was evaluated by matched pair comparison by a reader panel. Volumetric isocontouring of intrahepatic 90Y radioactivity was also performed and compared using an IntelliSpace Portal workstation (Philips). Results: All 25 patients had evaluable post-radioembolization dPET/CT and cPET/CT images for qualitative assessment of intrahepatic 90Y radioactivity. Despite the shorter image acquisition time, both dPET and cPET images demonstrate better image quality and improved 90Y-to-background contrast when compared with standard bremsstrahlung SPECT. Qualitatively, dPET/CT enabled more precise localization of the 90Y microsphere distribution within the liver when compared with cPET/CT. Similarly, volumetric isocontouring of the intrahepatic 90Y activity demonstrated consistently and significantly smaller 90Y-treated liver volumes with dPET than with cPET (average 90Y-treated liver volume was 1064 +/- 570 mL for dPET and 1372 +/- 634 mL for cPET, P < 0.05). Conclusion: These results demonstrate that next-generation digital photon counting PET detector technology enables faster 90Y imaging with improved image quality and 90Y-to-background contrast than bremsstrahlung SPECT/CT approaches. In addition, dPET/CT more precisely localizes 90Y microsphere activity within the liver than cPET/CT which is consistently demonstrated with smaller 90Y-treated liver volumes on dPET/CT. In the future, dPET/CT may improve qualitative evaluation of 90Y microsphere biodistribution for the assessment of concordance/discordance with pre-therapy imaging as well as foster new quantitative methodologies for 90Y-dosimetry. Research Support: Ohio Third Frontier (TECH 09-028, TECH 10-012, TECH 13-060) and Philips Healthcare provided the investigational pre-commercial release dPET/CT. ER -