The Spatial Relationship between Apparent Diffusion Coefficient and Standardized Uptake Value of 18F-Fluorodeoxyglucose Has a Crucial Influence on the Numeric Correlation of Both Parameters in PETMRI of Lung Tumors

Abstract EN

The minimum apparent diffusion coefficient (ADCmin) derived from diffusion-weighted MRI (DW-MRI) and the maximum standardized uptake value (SUVmax) of FDG-PET are markers of aggressiveness in lung cancer.

The numeric correlation of the two parameters has been extensively studied, but their spatial interplay is not well understood.

After FDG-PET and DW-MRI coregistration, values and location of ADCmin- and SUVmax-voxels were analyzed.

The upper limit of the 95% confidence interval for registration accuracy of sequential PET/MRI was 12 mm, and the mean distance (D) between ADCmin- and SUVmax-voxels was 14.0 mm (average of two readers).

Spatial mismatch (D > 12 mm) between ADCmin and SUVmax was found in 9/25 patients.

A considerable number of mismatch cases (65%) was also seen in a control group that underwent simultaneous PET/MRI.

In the entire patient cohort, no statistically significant correlation between SUVmax and ADCmin was seen, while a moderate negative linear relationship (r=-0.5) between SUVmax and ADCmin was observed in tumors with a spatial match (D ≤ 12 mm).

In conclusion, spatial mismatch between ADCmin and SUVmax is found in a considerable percentage of patients.

The spatial connection of the two parameters SUVmax and ADCmin has a crucial influence on their numeric correlation.