Impact of number of observers on reproducibility of gynaecological cancer MRI radiomics to interobserver contour variation.

BACKGROUND

Current studies assessing the reproducibility of radiomic features from gynaecological magnetic resonance images (MRIs) with interobserver contour variation (IOV) have been limited to ≤3 observers. This number of observers is insufficient to demonstrate the full range of IOV.

PURPOSE: To assess the impact of observer numbers when investigating the reproducibility of gynaecological T2W-MRI radiomic features with IOV.

METHODS

20 gynaecological cancer T2W-MRIs had the gross tumor volume (GTV), bladder, rectum, uterus, parametrium, and vagina delineated by 6 observers to create a 2-, 3-, 4-, 5-, and 6-observer dataset for each patient. IOV was assessed for each observer dataset and structure using the dice similarity coefficient, mean surface distance, and mean volume overlap variance. 107 radiomic features were extracted from each observer contour using PyRadiomics. The reproducibility of each radiomic feature was assessed for each observer dataset and structure using an intraclass correlation coefficient (ICC). An ICC estimate greater than 0.75 or 0.90 was classified as having good or excellent reproducibility, respectively.

RESULTS

The GTV had a decrease in the number of features with good/excellent reproducibility when the number of observers in the dataset increased. Volumes with less IOV, such as the bladder and uterus, did not show this same trend, with consistent numbers of features with good/excellent reproducibility across all observer datasets.

CONCLUSION

Determining the reproducibility of gynaecological T2W-MRI radiomic features to IOV with three or fewer observers is not adequate to display the full impact of IOV for GTVs.