Assessment of intra- and inter-observer variability in T1 relaxation time measurement for rectal cancer

BackgroundIn search of more accurate methods for rectal cancer diagnostics, T1 relaxation time measurement might have potential to become highly clinically relevant. The reproducibility of the methods has only been tested in few studies.PurposeTo investigate the reproducibility of measuring T1 relaxation time in rectal cancer by assessing the intra- and inter-observer variability.Material and MethodsIn this inter- and intra-observer study, magnetic resonance imaging (MRI) T1 maps were prospectively collected and analyzed by two observers. All images were obtained on 1.5-T MRI-units. T1 relaxation time was measured by contouring around the tumor border using free hand technique on a single slice. Intra- and inter-observer agreement were evaluated by the intraclass correlation coefficient (ICC) and Bland-Altman plots.ResultsA total of 41 MRI scans were included between 1 January and 31 October 2024. The cohort comprised 26 men and 15 women, with a mean age of 70 years (range = 28-92 years). The inter-observer agreement of T1 relaxation time was excellent across two reads with an ICC of 0.93 (95% confidence interval [CI]=0.85-0.97) and 0.91 (95% CI=0.83-0.95). The intra-observer agreement was excellent for both readers with an ICC of 0.94 (95% CI=0.88-0.97) for the less experienced reader and 0.90 (95% CI=0.81-0.95) for the experienced reader.ConclusionIn conclusion, analysis of MRI T1 maps and measuring of T1 relaxation time for evaluation of rectal cancer is has a high ICC. A reliable method is essential in the evaluation of complete response after neoadjuvant treatment.