Volumetric histograms-based analysis of apparent diffusion coefficients and standard uptake values for the assessment of pediatric sarcoma at staging: preliminary results of a PET/MRI study.

PURPOSE: To assess the relationship between apparent diffusion coefficients (ADC) and standard uptake values (SUV) of pediatric sarcomas at staging by using volumetric histograms analyses. METHODS: Children with histologically proven sarcoma, referring to our tertiary center for a whole-body 18F-FDG PET/MRI for staging and including diffusion weighted imaging in the MRI protocol were investigated. Firstly, turbo inversion recovery magnitude (TIRM) and PET images were resliced and resampled according to the ADC maps. Regions of interests were drawn along tumor margins on TIRM images and then copied on PET and ADC datasets. Pixel-based SUVs and ADCs were collected from the entire volume of each lesion. Mean, median, skewness, and kurtosis of SUVs and ADCs values were computed, and the Pearson correlation coefficient was then applied (for the entire population and for histological subgroups with more than five patients). RESULTS: Thirteen patients met the inclusion criteria (six females; mean age 8.31 ± 6.03 years). Histology revealed nine rhabdomyosarcomas, three Ewing sarcomas, and one chondroblastic osteosarcoma. A significant negative correlation between ADCs' and SUVs' mean (rmean = - 0.501, P < 0.001), median (rmedian = - 0.519, P < 0,001), and skewness (rskewness = - 0.550, P < 0.001) emerged for the entire population and for rhabdomyosarcomas (rmean = - 0.541, P = 0.001, rmedian = - 0.597, P < 0.001, rskewness = - 0.568, P < 0.001), whereas a significant positive correlation was found for kurtosis (rkurtosis = 0.346, P < 0.001, and rkurtosis = 0.348, P < 0.001 for the entire population and for rhabdomyosarcomas, respectively). CONCLUSION: Our preliminary results demonstrate that, using volumetric histograms, simultaneously collected SUVs and ADCs are dependent biomarkers in pediatric FDG-avid sarcomas. Further studies, on a larger population, are necessary to confirm this evidence and assess its clinical implications.