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- Title
Tumour ADC measurements in rectal cancer: effect of ROI methods on ADC values and interobserver variability.
- Authors
Lambregts DM; Beets GL; Maas M; Curvo-Semedo L; Kessels AG; Thywissen T; Beets-Tan RG; Lambregts, Doenja M J; Beets, Geerard L; Maas, Monique; Curvo-Semedo, Luís; Kessels, Alfons G H; Thywissen, Thomas; Beets-Tan, Regina G H
- Abstract
<bold>Objectives: </bold>To assess the influence of region of interest (ROI) size and positioning on tumour ADC measurements and interobserver variability in patients with locally advanced rectal cancer (LARC).<bold>Methods: </bold>Forty-six LARC patients were retrospectively included. Patients underwent MRI including DWI (b0,500,1000) before and 6-8 weeks after chemoradiation (CRT). Two readers measured mean tumour ADCs (pre- and post-CRT) according to three ROI protocols: whole-volume, single-slice or small solid samples. The three protocols were compared for differences in ADC, SD and interobserver variability (measured as the intraclass correlation coefficient; ICC).<bold>Results: </bold>ICC for the whole-volume ROIs was excellent (0.91) pre-CRT versus good (0.66) post-CRT. ICCs were 0.53 and 0.42 for the single-slice ROIs versus 0.60 and 0.65 for the sample ROIs. Pre-CRT ADCs for the sample ROIs were significantly lower than for the whole-volume or single-slice ROIs. Post-CRT there were no significant differences between the whole-volume ROIs and the single-slice or sample ROIs, respectively. The SDs for the whole-volume and single-slice ROIs were significantly larger than for the sample ROIs.<bold>Conclusions: </bold>ROI size and positioning have a considerable influence on tumour ADC values and interobserver variability. Interobserver variability is worse after CRT. ADCs obtained from the whole tumour volume provide the most reproducible results. Key Points • ROI size and positioning influence tumour ADC measurements in rectal cancer • ROI size and positioning influence interobserver variability of tumour ADC measurements • ADC measurements of the whole tumour volume provide the most reproducible results • Tumour ADC measurements are more reproducible before, rather than after, chemoradiation treatment • Variations caused by ROI size and positioning should be taken into account when using ADC as a biomarker for tumour response.
- Publication
European Radiology, 2011, Vol 21, Issue 12, p2567
- ISSN
0938-7994
- Publication type
journal article
- DOI
10.1007/s00330-011-2220-5