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11.12.2015 | Original Article | Ausgabe 3/2016

Annals of Nuclear Medicine 3/2016

18F-FDG and 18F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes

Annals of Nuclear Medicine > Ausgabe 3/2016
Sampanna Jung Rayamajhi, Bhagwant Rai Mittal, Venkata Nagarjuna Maturu, Ritesh Agarwal, Amanjit Bal, Pranab Dey, Jaya Shukla, Dheeraj Gupta



There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently 18F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) and 18F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant.

Materials and methods

A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body 18F-FLT PET/CT and 18F-FDG PET/CT (within 1 week of each other). Lymph nodal tracer uptake was determined by calculation of standardized uptake value (SUV) with both the tracers. Results of PET/CT were compared with histopathology of the lymph nodes.


Histopathology results showed thirty-seven patients with sarcoidosis, seven patients with tuberculosis, nine patients with non-small cell lung cancer, five patients with Hodgkin’s lymphoma and twelve patients with non-Hodgkin’s lymphoma. The mean FDG SUVmax of sarcoidosis, tuberculosis, Hodgkin’s and non-Hodgkin’s lymphoma was 12.7, 13.4, 8.2, and 8.8, respectively, and the mean FLT SUVmax was 6.0, 5.4, 4.4, and 3.8, respectively. It was not possible to characterize mediastinal lymphadenopathy as benign or malignant solely based on FDG SUVmax values (p > 0.05) or FLT SUVmax values (p > 0.05). There was no significant difference in FDG uptake (p > 0.9) or FLT uptake (p > 0.9) between sarcoidosis and tuberculosis. In lung cancer patients, the FDG SUVmax and FLT SUVmax of those lymph nodes with tumor infiltration on biopsy was 6.7 and 3.9, respectively, and those without nodal infiltration was 6.4 and 3.7, respectively, and both the tracers were not able to characterize the nodal status as malignant or benign (p > 0.05).


Though 18F-FLT PET/CT and 18F-FDG PET/CT reflect different aspects of biology, i.e., proliferation and metabolism, respectively, neither tracer could provide satisfactory categorization of benign and malignant lymph nodes. The results of this study clearly suggest that differentiation of mediastinal nodes into benign and malignant solely based on SUVmax values cannot be relied upon, especially in settings where tuberculosis and sarcoidosis are common.

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