Evaluation of diffuse lymphadenopathy via various quantitative PET/CT parameters

Discovery of diffuse lymphadenopathy (DLAP) in fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) imaging alerts for the existence of many pathologic conditions with severity ranging from benign to malignancy. This study examines the role of various metabolic parameters reflecting ¹⁸F-FDG characteristics of organs/tissues to reach an accurate differential diagnosis for further clinical assessment.

Positron emission tomography/CT images of 78 patients with DLAP were reviewed retrospectively. The diameter of the largest lymph node (DLlyn), maximum standardized uptake value (SUVmax) of the liver (L), the largest lymph node (Llyn), spleen (S), and bone marrow (BM) were measured. Ratios to liver SUVmax were calculated for all, resulting LLRmax, SLRmax, and BMLRmax respectively.

The diameter of the largest lymph node, Llyn.SUVmax, LLRmax, and SLRmax produced cut-off values as 25.5, 8.86, 2.80, and 0.82 with corresponding sensitivity:specificity values as 65%:83%, 74%:77%, 74%:71%, and 79%:63% respectively for risk stratification of malignant causes. To differentiate lymphoma from sarcoidosis, DLlyn, SLRmax, and BMLRmax were found valuable with cut-off values obtained as 28.5, 0.84, and 1.19 with corresponding sensitivity:specificity values as 79%:91%, 79%:82%, and 54%:91%, respectively.Interdependency between parameters was also evaluated.

High values of Llyn.Maximum SUV and LLRmax are the main characteristics of lymphoma, metastasis, and sarcoidosis. The diameter of the largest lymph node, SLRmax, and BMLRmax are determined as distinct parameters for distinguishing lymphoma from sarcoidosis. Besides, observed correlation structures amongst some PET/CT parameters were identified as nodal, extranodal, and diffuse patterns for three disease groups except sarcoidosis. These findings extend the knowledge about diagnostic factors based on ¹⁸F-FDG PET/CT patterns for DLAP.