Maria Tomas

22. FDG Uptake in Infectious Mononucleosis.

Background: As the role of PET-FDG imaging is being established in the staging and monitoring of response to therapy in children with lymphoma, we encountered a case of an infection common in adolescence that may present with lymphoma-like signs and symptoms.Methods: A 13-year-old previously healthy male presented with a left neck mass associated with weakness, fatigue, intermittent fevers and weight loss. He was then referred to the hematology/oncology department with a working diagnosis of lymphoma. The total wbc count was 5920/cu mm with 75% lymphocytosis without atypical lymphocytes. ESR was 20 mm. Serologic analysis for EBV, CMV, toxoplasmosis and hepatitis was also performed. The chest x-ray was normal. CT scan demonstrated multiple enlarged lymph nodes in both right and left jugulodigastric and spinal accessory chains; the largest mass within the left spinal accessory chain had focal necrosis within it. There were no enlarged mediastinal or axillary nodes. The spleen was massively enlarged and the splenic index was 924 (normal for age = 744).Results: FDG imaging showed intense uptake in both cervical regions, the mediastinum and in the enlarged spleen. The results of the Monospot test and the EBV panel which were both positive, were available 3 & 5 days later. Based on these serologic results, the history, physical findings and the negative chest x-ray, the final diagnosis was infectious mononucleosis.Conclusion: Despite availability, ease of performance and sensitivity of FDG imaging, this case illustrates the importance of clinical, hematologic and serologic assessment of disease prior to FDG imaging.

5. Utility of F-18 FDG Imaging for Diagnosing the Infected Joint Replacement

Purpose: F-18 FDG (FDG) is reportedly useful for detecting infection. Because the procedure is simple, with results being readily available, this prospective study was undertaken to evaluate the utility of FDG imaging for diagnosing infected joint replacements.Methods: 26 pts, 18 females and 4 males between 37 and 87 years old, with 31 joint replacements were studied. 21 pts had single joint replacement (10 hip, 11 knee); 5 pts had bilateral replacements (1 hip, 4 knee). Imaging was performed on a Hybrid PET system, with measured attenuation correction, one hour after administration of 150 MBq FDG. Increased peri-prosthetic uptake compared to adjacent, presumably normal, activity was interpreted as positive for infection.Results: 11 of 31 prostheses were infected. Sensitivity, specificity, and accuracy of FDG were 100%, 55%, and 71% respectively. The PPV was 55% and the NPV was 100%. Excluding the 5 asymptomatic prostheses in pts with bilateral joint replacements, the sensitivity, specificity, and accuracy were 100%, 47%, and 69% respectively. The PPV was 58% and the NPV was 100%. 4 pts with infected prostheses underwent a total of 6 follow-up studies after treatment. In 1 pt with persistent infection, all 3 follow-up studies were true positive. In the other 3 pts in whom infection had been eradicated, follow-up FDG studies were false positive.Conclusion: FDG imaging is sensitive but not specific; consequently, its role in pts with suspected prosthetic infection is limited to that of a screening test. These data also suggest that this technique is not useful for monitoring response to treatment.

Correlación de los parámetros hematológicos con la captación de FDG en médula ósea y bazo en la PET

Resumen Objetivo Valorar la correlacion existente entre los parametros hematologicos y la captacion de FDG en medula osea (MO) y bazo en la PET. Material y metodos 29 pacientes (pts) con linfoma de Hodgkin remitidos para un estudio inicial con FDG PET antes de comenzar el tratamiento y sin evidencia de afectacion en MO, fueron incluidos en el estudio. En 18 pts sin afectacion esplenica tambien se valoro la captacion de FDG en el bazo. La captacion en MO y bazo se clasifico de acuerdo a una escala visual de tres puntos, y se determino si era homogenea o difusa. Tambien se realizo un analisis semi-cuantitativo por medio de unos indices de captacion obtenidos a traves de unas regiones de interes, en medula osea y bazo, en relacion con otras en pulmon derecho e higado. Se calcularon unos coeficientes de correlacion entre la escala visual y los indices semi-cuantitativos en medula osea y bazo, con las cifras de hemoglobina (Hb), leucocitos y plaquetas en sangre. Resultados En 27/29 pts la captacion de FDG en MO y en 18/18 pts la captacion en bazo fue homogenea. Se objetivo una correlacion directa entre las cifras de leucocitos y la captacion de FDG en MO y bazo. La correlacion era menor y ademas inversa con las cifras de Hb (esto es, cuanto mas baja la Hb mas alta la captacion en MO). Las correlaciones mas bajas se obtuvieron con la cifras de plaquetas. Conclusion Los diferentes parametros hematologicos pueden llegar a afectar la captacion de FDG en MO y bazo. El conocimiento de esta correlacion puede ayudar a la mejor interpretacion de los estudios FDG PET.OBJECTIVE To assess the relationship between various hematologic parameters and bone marrow (BM) and splenic uptake of FDG in PET imaging. MATERIAL AND METHODS 29 patients with Hodgkins disease (HD) referred for baseline FDG PET imaging before treatment and without evidence of bone marrow (BM) involvement were included in the study. Splenic uptake also was analyzed in 18 patients without splenic involvement. BM and splenic activity were visually graded on a 3 point scale. Activity pattern was classified as homogeneous or heterogeneous. Semi-quantitative analysis was also performed by drawing regions of interest (ROI) over the spine and spleen. ROIs also were drawn over right lung and liver. FDG uptake ratios for the spine and spleen in comparison with the lung and liver were generated. Visual scoring of marrow and splenic uptake, and the various ratios were correlated with hemoglobin (Hb), white blood cell (WBC), and platelet counts, and correlation coefficients were calculated. RESULTS In 27/29 patients (93 %) BM and in 18/18 patients (100 %) spleen uptake was diffuse. There was a direct correlation between BM and spleen uptake of FDG with increasing WBC, which was stronger than the inverse correlation seen with Hb (the lower the Hb the greater the uptake). Correlation with platelet counts was weaker. CONCLUSION There is a correlation between hematologic parameters such as Hb, WBC and platelet counts and the uptake of FDG in BM and spleen in PET imaging. Knowledge of this correlation should help to better interpret and understand PET imaging.

18F-FDG Uptake in the Anterior Mediastinum. Physiologic Thymic Uptake or Disease?

Purpose: We reviewed 18F-fluorodeoxyglucose (18F-FDG) studies to determine the frequency of thymic visualization, to characterize this uptake to facilitate differentiation from disease, and to ascertain effects of therapy on visualization.Methods: Hybrid positron emission tomography images performed on 14 patients with known or suspected malignancy before therapy, and on six of the patients after treatment, were reviewed. Mediastinal uptake was characterized by location, contour and intensity.Results: Thymic uptake seen in five patients, 13-16-years-old, was characterized by an anterior midline location, regular contours, and a mean uptake ration of 2.5, and involved large glands. In five patients with mediastinal disease, 16-23-years-old, uptake was more posterior and eccentric in location with irregular borders and a mean uptake ratio of 4.3. One patient had anterior (thymic) and posterior (disease) mediastinal uptake. Three patients, 15-22-years-old, without disease and small thymus glands had no uptake. Five patients, including two with baseline uptake, showed no thymic uptake subsequently. One patient, negative initially, had thymic uptake five months after therapy.Conclusions: Thymic 18F-FDG uptake occurs in younger patients, before or after treatment, and is associated with larger glands. Its midline anterior mediastinal location and mild intensity should facilitate discrimination from disease.