Optimization of timing of hepatocellular phase imaging after gadoxetate disodium injection for evaluation of patients with neuroendocrine tumor

Purpose Metastatic gastroenteropancreatic neuroendocrine neoplasms (mGEP-NEN) are indolent malignancies which undergo frequent imaging follow-up. Hepatocellular phase (HCP) MR with hepatocellular-specific contrast agent is widely used to evaluate mGEP-NEN liver metastases but is commonly performed after a 20-min delay which prolongs scan time. The purpose of this study was to evaluate if HCP MR at 15 min offers comparable performance to 20-min delay for patients with mGEP-NEN undergoing routine imaging surveillance. Materials and methods In this IRB-approved retrospective study, we evaluated 52 patients with mGEP-NEN who were imaged for routine surveillance with gadoxetate disodium (Eovist(R))-enhanced MR including 15- and 20-min delayed HCP. Two readers (R1, R2), blinded to HCP timing, independently reviewed each set of images in random order at least 1 month apart. Readers assessed presence and conspicuity of metastases, and subjective image quality using 5-point scales. Readers quantified the number of metastases and diameter of the largest lesion. Statistical analysis was performed to determine individual-reader and inter-reader differences for qualitative and quantitative data. Results No differences were observed for subjective image quality (R1 p = 0.86, R2 p = 0.17) or lesion conspicuity (R1 p = 0.56, R2 p = 0.74) at 15 min and 20 min for either reader. Individual-reader concordance correlation coefficient between 15 and 20 min was high for number of metastases detected (R1 = 0.9842, R2 = 0.9579) and diameter of largest metastasis (R1 = 0.9629, R2 = 0.8859). Conclusion HCP imaging at 15 min provides similar diagnostic yield to standard 20-min delay, which may help reduce the scan time and costs, and improve throughput and patient satisfaction.