Auto-delineation framework for the focal liver reaction observed in post Stereotactic Body Radiation Therapy (SBRT) Primovist MRI scans

Abstract

Development of a novel auto-delineation methodology for observed hypointensity from focal liver reaction in hepatobiliary-specific contrast (Primovist) enhanced MRI acquired post Stereotactic Body Radiation Therapy (SBRT). Additionally, the methodology for the quantification of the threshold dose associated with the observed focal liver reaction was also established. An auto-delineation algorithm was created based on the correlation between intensity and radiation dose information. The error associated with the auto-delineation was quantified using virtual FLRs, as well as clinical patient scans. Patients underwent liver SBRT with a total dose prescription of 50 Gy in 5 fractions. An inherent correlation was established between the contrast-to-noise ratio (CNR) on MRI scans and expected performance of the algorithm using centre-of-mass (COM). Threshold dose associated with focal liver reaction was quantified for all ten patients and verified with associated most conformal isodose line. Based on the CNR vs COM error relationship, the expected median (range) auto-delineation COM error for ten patients was 0.5 (0 to 3.2) mm. The median threshold dose for ten clinical cases was 21.3 Gy based on the auto-delineation framework. This threshold dose was compared to the most conformal isodose line with the hypointensity; there was no significant difference observed (p = 0.6). We developed a framework for post-SBRT Primovist observed focal liver reaction localization. Furthermore, this study established an automated approach for the determination of the threshold dose associated with the hypointense region.

Keywords: Liver; MRI; Primovist; Stereotactic Body Radiation Therapy (SBRT).