title: (18)F-FDG and (18)F-FLT PET/CT imaging in the characterization of mediastinal lymph nodes.
abstract: OBJECTIVE
  There is currently no single modality for accurate characterization of enlarged mediastinal lymph nodes into benign or malignant. Recently (18)F-fluorothymidine (FLT) has been used as a proliferation marker. In this prospective study, we examined the role of (18)F-fluorodeoxyglucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) and (18)F-FLT PET/CT in categorizing mediastinal lymph nodes as benign or malignant.
  
  
  METHODS
  A total of 70 consecutive patients with mediastinal lymphadenopathy detected on computed tomography (CT) or chest radiograph underwent whole body (18)F-FLT PET/CT and (18)F-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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  Though (18)F-FLT PET/CT and (18)F-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.
authors.affiliation: Department of Nuclear Medicine and PET, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Sampanna Jung
authors.initials: SJ
authors.lastname: Rayamajhi
authors.affiliation: Department of Nuclear Medicine and PET, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India. brmittal.pgi@gmail.com.
authors.forename: Bhagwant Rai
authors.initials: BR
authors.lastname: Mittal
authors.affiliation: Department of Nuclear Medicine and PET, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Venkata Nagarjuna
authors.initials: VN
authors.lastname: Maturu
authors.affiliation: Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Ritesh
authors.initials: R
authors.lastname: Agarwal
authors.affiliation: Department of Histopathology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Amanjit
authors.initials: A
authors.lastname: Bal
authors.affiliation: Department of Cytology and Gynaecological Pathology, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Pranab
authors.initials: P
authors.lastname: Dey
authors.affiliation: Department of Nuclear Medicine and PET, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Jaya
authors.initials: J
authors.lastname: Shukla
authors.affiliation: Department of Pulmonary Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh, 160 012, India.
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Gupta
mesh_terms: D000328:Adult; D015224:Dideoxynucleosides; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D000072281:Lymphadenopathy / Q000000981:diagnostic imaging*; D008297:Male; D008482:Mediastinum / Q000000981:diagnostic imaging*; D008875:Middle Aged; D000072078:Positron Emission Tomography Computed Tomography; D011446:Prospective Studies; D055815:Young Adult
chemical_list: D015224:Dideoxynucleosides; D019788:Fluorodeoxyglucose F18; C002854:alovudine
keywords: 18F-FDG PET/CT; 18F-FLT PET/CT; Mediastinal lymphadenopathy; Sarcoidosis; Tuberculosis