Intra- and inter-observer variability in dependence of T1-time correction for common dynamic contrast enhanced MRI parameters in prostate cancer patients.

BACKGROUND

Dynamic contrast enhanced (DCE) MRI parameters are potential biomarkers to characterise tumour vasculature and distinguish it from the non-cancerous blood vessel system within the prostate. However, the inevitable presence of intra- and inter-observer variabilities is challenging in this context. Additionally, pre-contrast T1-time correction is a prerequisite to gain quantitative DCE parameters in the first place. The current study investigated the effect of individualized T1-time correction on intra- and inter-reader variability for quantitative DCE-parameters in prostatic lesions.

METHODS

In this IRB-approved retrospective study, two experienced radiologists assessed DCE parameters using individually measured (A) and fixed (B) T1-times twice with a time difference of three weeks. The dataset consisted of 35 MRI-guided biopsy-proven prostate cancer lesions. Limits of agreement (LoA) and coefficients of variability (CoV) were calculated to assess intra- and inter-reader variabilities of the parameters.

RESULTS

With exception of k, for all DCE parameters both intra- and inter-reader CoV were smaller in B compared to A. Absolute k values were largely insensitive to T1-time correction induced bias. The mean intra-reader CoVs [5%, 95% percentile] (over all four DCE parameters and both readers) were 6.7% [0.5%, 15.1%] in A and 3.9% [0.2%, 11.0%] in B. The inter-reader CoVs were 9.0% [0.6%, 25.8%] (A) and 7.0% [0.3%, 25.4%] (B).

CONCLUSIONS

T1-time correction has a significant influence on the intra- and inter-reader variability. By applying individually measured T1-time correction, both intra- and inter-observer variability were found to increase. Out of all investigated DCE parameters, k is the most robust to this investigated bias.