RT Journal Article SR Electronic T1 18F-FDG PET/CT in intracranial leptomeningeal carcinomatosis JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 1680 OP 1680 VO 59 IS supplement 1 A1 Susanna Nuvoli A1 Silvia Contu A1 Bi Llie Joy Pung A1 Patrizia Solinas A1 Giuseppe Madeddu A1 Angela Spanu YR 2018 UL http://jnm.snmjournals.org/content/59/supplement_1/1680.abstract AB 1680Objectives: Leptomeningeal carcinomatosis is a secondary infiltration by neoplastic cells in meningeal space mainly from solid tumors. MRI is usually used for its identification, but definitive diagnosis can be only achieved by repeated cerebrospinal fluid (CSF) analyses. We used 18F-FDG PET/CT as complementary diagnostic tool in patients with suspect leptomeningeal carcinomatosis. Methods: We retrospectively evaluated four consecutive patients with clinical symptoms of suspect leptomeningeal carcinomatosis: two patients (A-B) had been treated for breast carcinoma, one had lung adenocarcinoma (C) and the remaining one had been treated for rib chondrosarcoma (D). Patients A-B-C had uncertain MRI, while in case D it was not practicable because of pacemaker. Initial CSF cytology was not conclusive in patients A-C-D and negative in case B. All patients underwent both whole body (WB) and brain 18F-FDG PET/CT (Discovery 710, GE Healthcare) after 370 MBq tracer i.v. injection. RESULTS: Brain PET/CT evidenced numerous foci of high tracer activity in cerebral structures suggestive for leptomeningeal carcinomatosis: scattered in different sinuses, sagittal bilaterally and trasverse/sphenoparietal at left (A); parieto-occipital and calcarine sulcus with partial cerebral fissure involvement (C); Brodmann Areas 2, 4 in angular gyrus and precuneus of both hemispheres and left limbic areas (D). MRI remained unclear in repeated exams for intracranial lesions, while CSF only after repeated lumbar punctures ascertained cells with atypical mitosis suggestive for neoplastic cell dissemination (A-C-D). WB PET/CT detected an elevated metabolic activity focus in medullary channel (A) also evidenced by MRI and a lung focus corresponding to adenocarcinoma already identified at diagnostic CT. However, both brain and WB PET/CT were negative in patient B excluding leptomeningeal carcinomatosis as confirmed by repeated CSF, despite unclear MRI. CONCLUSION: Positive brain 18F-FDG PET/CT identified leptomeningeal carcinomatosis in 3/4 patients while negative PET/TC excluded LC in 1/4 cases according to repeated CSF, but MRI remaining uncertain. WB PET/CT could ascertain extra-cerebral neoplastic lesions. Both brain and WB PET/CT could be useful as leptomeningeal carcinomatosis complementary diagnostic tools, in particular when MRI is uncertain or not practicable and CSF is initially inconclusive.