TY - JOUR T1 - Ultra-high defintion PET/CT imaging of the orbit enabled by next generation digital PET technology JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1324 LP - 1324 VL - 58 IS - supplement 1 AU - Chadwick Wright AU - Katherine Binzel AU - Carl Odom AU - Jun Zhang AU - Piotr Maniawski AU - Michael Knopp Y1 - 2017/05/01 UR - http://jnm.snmjournals.org/content/58/supplement_1/1324.abstract N2 - 1324Objectives: The recent introduction of next-generation digital photon counting PET detector (dPET) technology will enable new precision nuclear medicine practices for oncologic and non-oncologic patients. In particular, dPET allows for higher definition PET imaging with smaller voxel volumes when compared with conventional photomultiplier tube-based clinical PET/CT systems. The objective of this study is to assess the feasibility and evaluate the clinical capability of higher definition dPET/CT imaging for the assessment of the orbit and its structures.Methods: Ten oncology patients with no known orbital malignant/metastatic involvement agreed to participate in an ongoing methodology development clinical trial using a pre-commercial release dPET/CT scanner (Vereos, Philips Healthcare). Standard whole-body dPET/CT was performed using a target 481 MBq FDG dose. Digital PET images were reconstructed using Time-of-Flight with different voxel volumes 4x4x4 mm3 (standard definition), 2x2x2 mm3 (high definition), and 1x1x1 mm3 (ultra-high definition). Low-dose CT images were also reconstructed with different voxel volumes of 4x4x4 mm3, 2x2x2 mm3, and 1x1x1 mm3. Standard definition dPET/CT data sets consisted of 4mm voxel lengths for both dPET and CT images. Likewise, high definition and ultra-high definition dPET/CT data sets consisted of 2mm and 1mm voxel lengths for dPET and CT, respectively. Intra-individual comparison of dPET/CT image characteristics of the orbits as well as overall image quality and background quality was performed by a blinded reader panel using an Intellispace Portal workstation.Results: All 30 dPET data sets were evaluable. Ultra-high definition dPET/CT images of the orbits were rated best by the reader panel. There was a substantial improvement in image quality for the qualitative and quantitative assessment of the orbit and its structures with no appreciable impact on the background FDG activity. No pathologic lesions were identified. Overall, higher definition dPET/CT data sets allowed for better delineation, more confident identification and PET characterization of the orbital soft tissue structures including the globe, retina region, optic nerve, superior/lateral/inferior/medial rectus muscles, superior/inferior oblique muscles, lacrimal glands and nasolacrimal ducts. Physiologic FDG uptake within the individual intraocular muscles demonstrated slightly increasing SUVmax values with higher definition reconstructions which is likely due to reduction in the partial volume effects.Conclusion: These findings demonstrate that next-generation dPET/CT technology enabling high and ultra-high definition PET/CT imaging of the orbits is feasible even when using routine whole-body PET acquisitions. At present, there is an unmet clinical need for improved detection of FDG-avid intraocular malignancies and metastases. Such lesions can be visually less conspicuous on standard definition PET/CT imaging and similarly challenging to quantify due to the presence of intense physiologic FDG uptake within the adjacent intraocular muscles. Future studies using higher definition dPET/CT in patients with known benign and malignant ocular pathologies will helpful in establishing new precision nuclear medicine practices and better utilizing existing PET imaging biomarkers like FDG. Research Support: ODSA TECH 13-060, TECH 10-012, and TECH 09-028 ER -