Measurements of Hepatic Metastasis on MR Imaging:: Assessment of Interobserver and Intersequence Variability.

Rationale And Objectives: The purpose of the study was to investigate interobserver and intersequence variability in the measurement of hepatic metastasis on magnetic resonance imaging (MRI).

Materials And Methods: This retrospective study was conducted with an institutional review board-approved waiver of informed consent and was in compliance with the Health Insurance Portability and Accountability Act. We searched medical records at our institution for patients with histologically proven metastases to the liver who had undergone MRI from January 2008 to June 2010. We identified 20 patients with 30 measurable liver lesions. The liver lesions were measured on five different MRI sequences. A presenter radiologist selected and localized all metastatic lesions considered to be measurable according to the Response Evaluation Criteria in Solid Tumors, and these lesions were measured (Eisenhauer et al., 2009) by three radiologists independently. We calculated lesion-wise intraclass correlation coefficients (ICCs) to estimate interobserver and intersequence agreement in lesion diameter measurement. A Bland-Altman plot was used to estimate the limits of agreement between radiologists and MRI sequences.

Results: There were 30 metastases, and almost all of which had regular and well-defined margins. Interobserver ICCs were greater than 0.95 for different MRI sequences except for the measurements in apparent diffusion coefficient images. Intersequence ICCs were greater than 0.92. Bland-Altman plots between physicians confirmed that reader measurements were closely tied together, with small differences in means.

Conclusions: MRI can reproducibly measure hepatic metastatic lesions without significant variability among interpreting radiologists or among MRI sequences, and is thus a reliable method for assessing the size of hepatic metastasis.