Recommendations for improved reproducibility of ADC derivation on behalf of the Elekta MRI-linac consortium image analysis working group

• Published in: Radiotherapy and oncology 2023-09, Vol.186, p.109803, Article 109803
• Main Authors: Bisgaard, Anne L.H., Keesman, Rick, van Lier, Astrid L.H.M.W., Coolens, Catherine, van Houdt, Petra J., Tree, Alison, Wetscherek, Andreas, Romesser, Paul B., Tyagi, Neelam, Lo Russo, Monica, Habrich, Jonas, Vesprini, Danny, Lau, Angus Z., Mook, Stella, Chung, Peter, Kerkmeijer, Linda G.W., Gouw, Zeno A.R., Lorenzen, Ebbe L., van der Heide, Uulke A., Schytte, Tine, Brink, Carsten, Mahmood, Faisal
• Format: Article
• Language: English
• Subjects: Adaptive radiotheray; ADC reproducibility; Apparent diffusion coefficient; Diffusion Magnetic Resonance Imaging - methods; Diffusion-weighted magnetic resonance imaging; Humans; Image Processing, Computer-Assisted - methods; Magnetic Resonance Imaging; Male; MRI biomarkers; MRI-Linac; Neoplasms; Reproducibility of Results
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2023.109803

•Different image post-processing introduces ADC variation between centres.•Aligning ADC calculation methods between centres improves reproducibility.•Calculation-related ADC variation is larger than delineation-related ADC variation. The apparent diffusion coefficient (ADC), a potential imaging biomarker for radiotherapy response, needs to be reproducible before translation into clinical use. The aim of this study was to evaluate the multi-centre delineation- and calculation-related ADC variation and give recommendations to minimize it. Nine centres received identical diffusion-weighted and anatomical magnetic resonance images of different cancerous tumours (adrenal gland, pelvic oligo metastasis, pancreas, and prostate). All centres delineated the gross tumour volume (GTV), clinical target volume (CTV), and viable tumour volume (VTV), and calculated ADCs using both their local calculation methods and each of the following calculation conditions: b-values 0–500 vs. 150–500 s/mm2, region-of-interest (ROI)-based vs. voxel-based calculation, and mean vs. median. ADC variation was assessed using the mean coefficient of variation across delineations (CVD) and calculation methods (CVC). Absolute ADC differences between calculation conditions were evaluated using Friedman’s test. Recommendations for ADC calculation were formulated based on observations and discussions within the Elekta MRI-linac consortium image analysis working group. The median (range) CVD and CVC were 0.06 (0.02–0.32) and 0.17 (0.08–0.26), respectively. The ADC estimates differed 18% between b-value sets and 4% between ROI/voxel-based calculation (p-values