Association between Liver Imaging Changes after Liver SBRT as Estimated by Area under the Dynamic Contrast-Enhanced MRI Curve and Changes in Global Liver Function

Purpose/Objective(s)To quantify imaging changes from pre- to post-treatment dynamic contrast enhanced (DCE) MRI following liver SBRT for hepatocellular carcinoma (HCC) and examine the association with changes in albumin-bilirubin (ALBI) score.Materials/MethodsPatients from a single institution treated with liver SBRT for HCC with available DCE-MRIs using a hepatocyte-specific contrast agent, Gb-EOB-DTPA, were identified. Whole liver volumetric contours were delineated on all dynamic MRI phases for pre- and post-treatment scans. Post-treatment scans were registered to the pre-treatment scans using rigid registration (median DICE coefficient 0.88, range: 0.75 to 0.95). A 3-compartment kinetic model was used to fit the signal intensity data over time from the DCE-MRI scans using the abdominal aorta as vascular input function surrogate. The area under the modeled signal intensity curve from zero to 20 minutes post contrast injection (AUC20) was estimated for each individual liver voxel (∼12,000 voxels when downsampled to ∼4 × 4 × 6 mm3) and was used as an indicator of imaging-based liver function. ALBI scores were calculated from each patient's medical records at pre-treatment and at 6 months post SBRT. The association between change in AUC20 throughout any part of the liver and change in ALBI score was assessed using linear regression and t-test.ResultsThirty-six patients met inclusion criteria. All patients were treated in five fractions with the majority treated to a total dose of 50 Gy (70%). The median time from SBRT to analyzed post-treatment MRI scan was 6 months (range: 4-8 months). Median baseline ALBI score was -2.49 (range: -3.29 to -1.35) and the median change in ALBI score was 0.17. The average pre-treatment AUC20 within all liver voxels was 3.38 (±1.36), compared to 3.09 (±1.39) at post-treatment. For most patients there was not a considerable change in median AUC20, but for the patients with >30% reduction in AUC20 the average worsening in ALBI score was 0.45 points. The change in AUC20 was significantly correlated with the change in ALBI score at 6 months (p=0.012). Linear regression analysis adjusted for baseline ALBI score showed a significant worsening of ALBI score with increasing reduction in median AUC20 (p=0.017). Patients with clinically significant worsening of ALBI score at 6 months (at least 0.5-point increase) had an average 33% reduction in median AUC20 compared to an average 2% increase in AUC20 for patients without clinically significant ALBI score change (p=0.014).ConclusionPost-treatment changes in MR-based liver imaging assessed by reduction in AUC20 were significantly associated with change in ALBI score. This type of voxel-wise estimation of region-specific imaging features could potentially be used to improve future treatment personalization.