Benedikt Michael Schaarschmidt MD, Presenter: Nothing to Disclose

Christian Buchbender, Abstract Co-Author: Nothing to Disclose

Felix Nensa MD, Abstract Co-Author: Nothing to Disclose

Verena Ruhlmann, Abstract Co-Author: Nothing to Disclose

Gerald Antoch MD, Abstract Co-Author: Speaker, Siemens Medical AG Speaker, Bayer AG Speaker, BTG International Ltd

Philipp Heusch MD, Abstract Co-Author: Nothing to Disclose

The mediastinal nodal stage is an important prognostic factor in NSCLC patients. Integrated PET/MRI offers the potential to improve lymph node diagnostics by combining PET-data with functional MRI. Therefore, the aim of this study was to correlate the tracer uptake of lymph node metastases, as reflected by SUVs derived from FDG-PET/MRI with ADC-values derived from simultaneous diffusion weighted imaging (DWI).

19 NSCLC patients (6 female, 13 male, mean age 58.7, SD±11.6) with lymph node metastases identified by histopathology or radiological follow-up were enrolled. All patients underwent PET/CT (Siemens mCT™) 60min after injection of a mean dose of 280MBq FDG and PET/MRI (Siemens Magnetom Biograph mMR™ ) including DWI (b values: 0, 100, 500, 1000, 2000s/mm²). The mean time interval between tracer injection and PET/MRI was 136min. FDG-avid and diffusion-restricted lymph nodes were analyzed on an OsiriX Apple Workstation by defining regions of interests (ROIs) encompassing the lesion on PET-images and the monoexponential ADC-Map. Pearson's correlation coefficients (r) were calculated and Bland Altman analysis was performed for SUVmax and SUVmean on PET/CT and PET/MRI. A p<0.05 was considered as statistically significant.

67 metastases in 19 patients were analyzed (24 histopathologically confirmed, 43 classified as metastases using radiological follow-up 227±134 days after initial diagnostics). A strong correlation between SUV on PET/MRI and PET/CT existed (SUVmax r=0.82, SUVmean r=0.84, p<0.001). Bland-Altman analysis revealed limits of agreement for SUVmax of 4.61 and -4.55 and of 3.72 and -2.35 for SUVmean, respectively. For all metastases, correlation was r=-0.69 between SUVmax and ADCmean and r=-0.71 between SUVmean and ADCmean (p<0.001).  

This simultaneous PET/MRI study corroborates the assumed significant inverse correlation between increased metabolic activity on FDG-PET and restricted diffusion on DWI in lymph node metastases of NSCLC patients.

The inverse correlation between SUV and ADC in therapy-naive lymph node metastases in NSCLC is an important finding and supports further evaluation of DWI in tumor response assessment with PET/MRI.

Schaarschmidt, B, Buchbender, C, Nensa, F, Ruhlmann, V, Antoch, G, Heusch, P, 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 [18]F-FDG PET/MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002097.html