Volume Delineation in Cervical Cancer With T2 and Diffusion-weighted MRI: Agreement on Volumes Between Observers.

Aim: To delineate cervical cancer gross tumor volume (GTV) on T2-magnetic resonance imaging (MRI) and apparent diffusion coefficient (ADC) maps, assessing volumes and inter-observer agreement between two observers. Patients and Methods: A radiologist and a radiation oncologist delineated GTV on T2 (T2GTV) and ADC (ADCGTV) sequences. Dice similarity index (DICE) and Bland-Altman analysis were used to estimated concordance. Results: Mean T2GTV and ADCGTV volumes were 43.84 +/- 71.47 cc and 37.28 +/- 68.92 cc according to the radiologist, and 43.4 +/- 70.44 cc and 36.65 +/- 69.21 cc according to the radiation oncologist. ADC led to statistically significantly smaller volumes compared to T2. The mean DICE index was 0.86 for T2GTV and 0.84 for ADCGTV. The Bland-Altman plots globally showed concordance. Conclusion: GTV delineation was smaller in the ADC maps compared to T2-MRI, reaching an almost perfect agreement between observers. Thanks to this acceptable variability, adding functional imaging might provide more information for tumor delineation, improving reproducibility for image-guided adaptive radiotherapy.