Related Experiment Video
Updated: Oct 25, 2026
Bulk Droplet Vitrification for Primary Hepatocyte Preservation
Published on: October 25, 2019
Streamlining Liver SABR: Validation and Initial Experience of Bulk Density Override Based Single-Session,
Yu Gao1, Eric Hsu1, Daniel Pham1
1Department of Radiation Oncology, Stanford University, Palo Alto, California.
Purpose:
Conventional liver stereotactic ablative radiotherapy (SABR) typically requires a CT simulation visit followed by multiple treatment fractions, which can increase patient burden and limit access. We propose an approach that consolidates imaging, planning, adaptation, and delivery into one session, utilizing an MR-guided adaptive workflow. We report here the workflow and dosimetric validation of a streamlined bulk density override (BDO) strategy and the initial clinical implementation of this simulation-free approach.
Methods And Materials:
A single-institution phase II trial was designed to deliver liver SABR (30-40 Gy in 1 fraction) in a single-session using an MR-guided Linac for patients with liver cancers using BDO strategy. To validate dosimetric accuracy, 17 previously treated single-fraction liver SABR plans were recalculated retrospectively using (1) CT-based electron density and (2) BDO-based density. DVH endpoints and 3D gamma analysis (1%/1mm) were compared. Early clinical experience from the first five trial patients is reported, including dose comparisons between BDO-based calculations and diagnostic CT-based calculations.
Results:
For the retrospective analysis, BDO-based calculation closely matched the CT-based calculation. For the PTV and GTV, the median percent differences were close to zero for all evaluated metrics and the maximum percent differences were all within 2%. For organ-at-risk (OAR) endpoints (chest wall, bowel, liver minus GTV, spinal cord), mean and maximum dose differences were within 0.1 Gy and 0.6 Gy, respectively. The average 3D gamma pass rate was 99.2%. For the first 5 patients treated on trial, BDO- and diagnostic CT-based reference plan metrics agreed within 1.5% for PTV coverage and within 0.5 Gy for key OAR endpoints. The mean gamma pass rate was 98.8%.
Conclusions:
The BDO strategy provides dosimetric agreement comparable to CT-based calculation and supports an efficient and patient-centric single-visit delivery model. Our results support further investigation of simulation-free, single-session MR-guided adaptive liver SABR.
