Functional Avoidance Liver 4π Stereotactic Body Radiation Therapy Informed by Quantitative Gadoxetic Acid...

Area of Science:

• Radiology and Medical Imaging
• Radiation Oncology
• Hepatology

Background:

• T1 reduction rates (k1) from gadoxetic acid-enhanced MR imaging are emerging biomarkers for liver function.
• Accurate assessment of liver function is crucial for optimizing radiation therapy, particularly for liver cancer patients.

Purpose of the Study:

• To validate k1 maps as a functional biomarker for liver function.
• To develop and evaluate 4π noncoplanar treatment plans utilizing k1 maps for liver functional avoidance stereotactic body radiation therapy (FA-SBRT).

Main Methods:

• Correlated mean k1 values (excluding GTV) with Child-Pugh and albumin-bilirubin scores in 106 patients.
• Identified high-function (HF) liver regions using Gaussian decomposition of k1 histograms.
• Retrospectively planned 4π FA-SBRT with and without functional avoidance in 20 patients, comparing dose metrics to coplanar plans.

Main Results:

• k1 values showed an inverse correlation with Child-Pugh and albumin-bilirubin scores.
• 4π FA-SBRT plans significantly reduced mean dose to HF liver by 21.8% (9.2 Gy to 6.5 Gy) (P < .0001).
• HF liver volume receiving >6 Gy was reduced by 39.5% (507.5 cm³ to 302.2 cm³) with 4π FA-SBRT (P < .0001).

Conclusions:

• k1 derived from T1 mapping MR is a validated liver function biomarker in cancer patients.
• Patient-specific HF liver masks can be created using Gaussian decomposition of k1 distribution.
• 4π FA-SBRT planning guided by k1 maps effectively reduces radiation dose to the high-function liver, improving liver sparing.