Functional imaging of lung cancer using dual energy CT: How does iodine related attenuation correlate with standardized uptake value of 18FDG-PET-CT?

Objectives To investigate the correlation between maximum standardized uptake value (SUV _max)of ¹⁸FDG PET-CT and iodine-related attenuation (IRA) of dual energy CT (DECT) of primary tumours and ¹⁸FDG PET-CT positive thoracic lymph nodes (LN) in patients with lung cancer. Methods 37 patients with lung cancer (27 NSCLC, 10 SCLC, 86 ¹⁸FDG PET-CT positive thoracic LN) who underwent both ¹⁸FDG PET-CT and DECT were analyzed. The mean study interval between ¹⁸FDG PET-CT and DECT was ≤21 days in 17 patients. The mean and maximum IRA of DECT as well as of virtual unenhanced and virtual 120 kV images of DECT was analyzed and correlated to the SUV _max of ¹⁸FDG PET-CT in all tumours and ¹⁸FDG PET-CT positive thoracic lymph nodes. Further subgroup analysis was performed for histological subtypes in all groups. Results A moderate correlation was found between SUV _maxand maximum IRA in all tumours (n=37;r=0.507;p=0.025) whereas only weak or no correlation were found between SUV _max and all other DECT measurements. A strong correlation was found in patients with study intervals <21 days (n=17; r=0.768;p=0.017). Analysis of histological subtypes of lung cancer showed a strong correlation between SUV _maxand maximum IRA in the analysis of all patients with NSCLC (r=0.785y=0.001) and in patients with NSCLC and study intervals ≤21 days (r=0.876;p=0.024). Thoracic LN showed moderate correlation between SUV _maxand maximum IRA in patients with study intervals ≤21 days (r=0.654; p=0.010) whereas a weak correlation was found between SUV _max and maximum IRA in patients with study intervals >21 days (r=0.299; p=0.035). Conclusions DECT could serve as a valuable functional imaging test for patients with NSCLC as the IRA of DECT correlates with SUVmax of ¹⁸FDG PET-CT.