title: Correlation of the apparent diffusion coefficient (ADC) with the standardized uptake value (SUV) in lymph node metastases of non-small cell lung cancer (NSCLC) patients using hybrid 18F-FDG PET/MRI.
abstract: OBJECTIVE
  To compare the apparent diffusion coefficient (ADC) in lymph node metastases of non-small cell lung cancer (NSCLC) patients with standardized uptake values (SUV) derived from combined 18F-fluoro-deoxy-glucose-positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI).
  
  
  METHODS
  38 patients with histopathologically proven NSCLC (mean age 60.1 ± 9.5 y) received whole-body PET/CT (Siemens mCT™) 60 min after injection of a mean dose of 280 ± 50 MBq 18F-FDG and subsequent PET/MRI (mean time after tracer injection: 139 ± 26 min, Siemens Biograph mMR). During PET acquisition, simultaneous diffusion-weighted imaging (DWI, b values: 0, 500, 1000 s/mm²) was performed. A maximum of 10 lymph nodes per patient suspicious for malignancy were analyzed. Regions of interest (ROI) were drawn covering the entire lymph node on the attenuation-corrected PET-image and the monoexponential ADC-map. According to histopathology or radiological follow-up, lymph nodes were classified as benign or malignant. Pearson's correlation coefficients were calculated for all lymph node metastases correlating SUVmax and SUVmean with ADCmean.
  
  
  RESULTS
  A total of 146 suspicious lymph nodes were found in 25 patients. One hundred lymph nodes were eligible for final analysis. Ninety-one lymph nodes were classified as malignant and 9 as benign according to the reference standard. In malignant lesions, mean SUVmax was 9.1 ± 3.8 and mean SUVmean was 6.0 ± 2.5 while mean ADCmean was 877.0 ± 128.6 x10(-5) mm²/s in PET/MRI. For all malignant lymph nodes, a weak, inverse correlation between SUVmax and ADCmean as well as SUVmean and ADCmean (r = -0.30, p<0.05 and r = -0.36, p<0.05) existed.
  
  
  CONCLUSIONS
  The present data show a weak inverse correlation between increased glucose-metabolism and cellularity in lymph node metastases of NSCLC patients. 18F-FDG-PET and DWI thus may offer complementary information for the evaluation of treatment response in lymph node metastases of NSCLC.
authors.affiliation: Univ Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Dusseldorf, Germany; Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany.
authors.forename: Benedikt Michael
authors.initials: BM
authors.lastname: Schaarschmidt
authors.affiliation: Univ Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Dusseldorf, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Buchbender
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Nensa
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Grueneisen
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Grueneien
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Nuclear Medicine, Essen, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Gomez
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Medical Oncology, Essen, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Köhler
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Institute of Pathology, Essen, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Reis
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Nuclear Medicine, Essen, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Ruhlmann
authors.affiliation: Univ Duisburg-Essen, Medical Faculty, Department of Diagnostic and Interventional Radiology and Neuroradiology, Essen, Germany.
authors.forename: Lale
authors.initials: L
authors.lastname: Umutlu
authors.affiliation: Univ Dusseldorf, Medical Faculty, Department of Diagnostic and Interventional Radiology, Dusseldorf, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Heusch
mesh_terms: D000368:Aged; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000737:chemistry; D005947:Glucose / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008198:Lymph Nodes / Q000000981:diagnostic imaging*; D008207:Lymphatic Metastasis; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D019275:Radiopharmaceuticals / Q000737:chemistry; D014057:Tomography, X-Ray Computed; D051598:Whole Body Imaging
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D005947:Glucose