TY - JOUR T1 - 3D Post Procedural Masking Technique to Improve Visibility of Small Lymph Node in Nuclear Medicine SPECT/CT Exams JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 2022 LP - 2022 VL - 60 IS - supplement 1 AU - Duy Tran AU - Eric Gingold AU - Maansi Parekh AU - Cheryl Rickley AU - Charles Intenzo AU - Sung Kim Y1 - 2019/05/01 UR - http://jnm.snmjournals.org/content/60/supplement_1/2022.abstract N2 - 2022Objectives: Lymphoscintigraphy of head and neck can pose some challenges for interpreting physicians. The hot injection site and associated “star artifact” can cause the LUT to be scaled in such a way that lower activity lesions are not visible, because of the extremely high counts emitted from the injection site. The sentential lymph node (SNL) on the other hand, usually contains less activity and emits lower counts, leading to them becoming “hidden”. Following removal of the injection site through digital masking, the renormalized image data permit these lesions to be seen quite easily, even though the underlying counts have not changed. To determine whether 3D digital masking improves detection of sentinel lymph node on head/neck SPECT/CT exams in the cancer patients. Materials and Methods: SPECT/CT is performed on Siemens’s Symbia Intevo camera. The software is processed on Siemen’s Syngo application. SPECT/CT:  30 sec/ view  48 views  Collimator: LEHR  Matrix: 128x128  Orbit: Non Circular  Mode: Step and shoot  1.0 Zoom  Care Dose4D-For CT  Slice 5mm Masking: ROIs were drawn manually in all 3 planes (axial, coronal, and sagittal) over the hottest site (usually injection site for lymphoscintigraphy) and removed from the image data. Following this digital masking, the image LUT (lookup table) scale (gray or color) was re-normalized by the application software. Three board certified nuclear medicine physicians reviewed the pairs of SPECT/CT exams and compared them to determine if the masking operation affected their interpretation. Results: Forty consecutive patients who underwent SPECT/CT of head and neck lymphoscintigraphy from 09/01/2017 - 12/31/2018 were included. In all 40 patients, the images in which an injection site hot spot was digitally removed improved the conspicuity of nearby nodes containing lower activity. Measured counts generally stayed the same with and without masking (<2 cts difference) but the renormalized LUT significantly changed the visibility of small lesions after the injection site was digitally removed by using the masking technique. Conclusions: Digital masking has improved contrast resolution and sentinel lymph node detection significantly in H/N lymphoscintigraphy. Future studies will compare SPECT/CT with digital masking to PET/CT. ER -