Multicenter validation of [18F]-FDG PET and support-vector machine discriminant analysis in automatically classifying patients with amyotrophic lateral sclerosis versus controls.

OBJECTIVE: 18F-Fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) single-center studies using support vector machine (SVM) approach to differentiate amyotrophic lateral sclerosis (ALS) from controls have shown high overall accuracy on an individual patient basis using local a priori defined classifiers. The aim of the study was to validate the SVM accuracy on a multicentric level. METHODS: A previously defined Belgian (BE) group of 175 ALS patients (61.9 ± 12.2 years, 120M/55F) and 20 screened healthy controls (62.4 ± 6.4 years, 12M/8F) was used to classify another large dataset from Italy (IT), consisting of 195 patients (63.2 ± 11.6 years, 117M/78F) and 40 controls (62 ± 14.4 years; 29M/11F) free of any neurological and psychiatric disorder who underwent whole-body 18F-FDG PET-CT for lung cancer without any evidence of paraneoplastic symptoms. 18F-FDG within-center group comparisons based on statistical parametric mapping (SPM) were performed and SVM classifiers based on the local training sets were applied to differentiate ALS from controls from the other centers. RESULTS: SPM group analysis showed only minor differences between both ALS groups, indicating pattern consistency. SVM using BE data set as training, classified 183/193 ALS-IT correctly (accuracy of 94.8%). However, 35/40 CON-IT were misclassified as ALS (accuracy 12.5%). Furthermore, using IT data as training, ALS-BE could not be distinguished from CON-BE. Within-center SPM group analysis confirmed prefrontal hypometabolism in CON-IT versus CON-BE, indicating subclinical brain changes in patients undergoing oncological scanning. CONCLUSION: This multicenter study confirms that the 18F-FDG ALS pattern is stable across centers. Furthermore, it highlights the importance of carefully selected controls, as subclinical frontal changes might be present in patients in an oncological setting.

18F-FDG PET/CT and MRI of a Mediastinal Malignant Granular Cell Tumor With Associated Recurrent Pericarditis.

We report a rare case of a mediastinal malignant granular cell tumor in a 41-year-old man presenting with dyspnea, retrosternal chest pain, and recurrent pericardial effusion under treatment with corticosteroids. Because of recurrent episodes, further investigations with chest MRI and F-FDG PET/CT revealed a large infiltrating and strongly hypermetabolic mass in the mediastinum with pericarditis. Histopathology and immunohistochemical analysis showed large cells with greater pleomorphism and eosinophilic granular cytoplasm with positive staining for S100 protein and CD68 as well as high Ki67 proliferative index (15%) confirming the diagnosis of a malignant granular cell tumor.

Metabolic and morphological measurements of subcutaneous and visceral fat and their relationship with disease stage and overall survival in newly diagnosed pancreatic adenocarcinoma : Metabolic and morphological fat measurements in pancreatic adenocarcinoma.

PURPOSE: The relationship between tumor metabolism and stage, subcutaneous and visceral fat thickness, and their glucose metabolism and overall survival in patients recently diagnosed with pancreatic carcinoma was assessed. METHODS: Thirty-eight consecutive patients were studied. Subcutaneous fat thickness (SFT), visceral fat thickness (VFT), and their corresponding FDG SUVmean, as well as SUVmean and SUVmax values of the primary tumor (PT) were derived from FDG-PET CT imaging. Results obtained as well as clinical variables obtained, including gender and BMI, were related to patient outcome. Median follow-up was 382 days (range: 36-917 days). RESULTS: Median age was 66 years (13 women). Mean BMI was 24.6 (SD: 4.5). Lymph node (LN) involvement was diagnosed in 17 patients and 14 patients presented with distant metastases. Mean SUV max and SUVmean values of the PT were 9.0 (SD 5.9) and 4.2 (SD 2.1). Mean values of SFT and VFT were, respectively, 11.9 mm (range 1-31.7 mm) and 11.5 mm (range 0-49.8 mm). The corresponding SUVmean values were 0.4 (range 0-1.0) and 0.6 (range 0.0-1.6). SUVmean values of SFT proved significantly lower in LNpositive versus LNnegative patients (p = 0.021), in patients with and without metastatic disease (p = 0.017) and in stage III+IV patients versus stage I+II patients (p = 0.03). An inverse logarithmic relationship was found between SUVmean values of subcutaneous fat and SUVmean values of the PT (p = 0.02). Only disease stage dichotomized according to stage I+IIA versus stage IIB+III+IV was predictive of overall survival (p = 0.05). CONCLUSION: Glucose metabolism of subcutaneous fat in de novo diagnosed pancreas carcinoma patients presenting with lymph node involvement and metastatic disease is significantly reduced and inversely correlated to the primary tumor metabolism. Of the various fat-related variables studied, none proved significantly related to outcome.

False-Positive Axillary Lymph Nodes Due to Silicone Adenitis on (18)F-FDG PET/CT in an Oncological Setting.

The case of a 49-year-old transgender individual with a history of bilateral silicone breast implants and a right lung mass proven by biopsy to be a non-small cell lung cancer is presented. In addition to the primary malignancy, a positron emission tomography/computed tomography scan showed contralateral hypermetabolic adenopathy in the left axilla that was suggestive of nodal metastatic disease. Additional imaging and histological examination of the lymph nodes indicated silicone breast implant leakage and silicone adenitis as the underlying cause of the hypermetabolic axillary lymph node.