578 - Refining Y90-SIRT Treatment Planning Through More Rational Use of Lung Shunt Fraction

Monday, April 13, 2026

12:10 PM - 1:10 PM ET

Poster Presenter(s)

Allan Thomas, PhD (he/him/his)

Assistant Professor
Mallinckrodt Institute of Radiology, Washington University School of Medicine, United States

Author/Co-author(s)

Ryan C. Lee, BS

Medical Student
Renaissance School of Medicine, Stony Brook University, United States
TA

Tharun T. Alamuri, BS

Medical Student
Renaissance School of Medicine, Stony Brook University, United States
JK

John Karageorgiou, MD

Assistant Professor
Mallinckrodt Institute of Radiology, Washington University School of Medicine, United States
DG

Dan Giardina, MD

Associate Professor
Mallinckrodt Institute of Radiology, Washington University School of Medicine, United States
DB

Daniel Braga, MD

Assistant Professor of Radiology
Mount Sinai Medical Center, United States
Naganathan Mani, MD (he/him/his)

Associate Professor
Washington University in St. Louis, United States
CM

Christopher Malone, MD

Associate Professor
Mallinckrodt Institute of Radiology, Washington University, United States

Purpose: Lung shunt fraction (LSF) and lung dose estimates are primary aspects of treatment planning in ⁹⁰Y-SIRT {1}. The objective in this work was to identify when a patient-specific LSF actively influences treatment planning and decision-making. The impacts of a more rational usage of parameters such as liver volume, lung mass, and LSF on achievable target and non-target dosimetry were analyzed.

Materials and Methods: Both planar (LSF_planar) and MAA-SPECT/CT (LSF_SPECT) clinical data were analyzed retrospectively in 354 glass ⁹⁰Y-SIRT cases. LSF_min was defined as the minimum LSF value where the maximum achievable perfused volume (PV) dose becomes determined by a selected lung dose threshold (LMD_max) instead of a designated whole-liver dose threshold (Liver_max). LSF_min values computed using both clinical and simulated treatment planning parameters were compared to clinical LSF. Probability density functions for LSF were estimated from clinical data using five tumor categories: 1) HCC < 3 cm, 2) HCC 3-8 cm, 3) HCC >8 cm, 4) any case with TIPS or macrovascular invasion (MVI), 5) non-HCC {2}.

Results: LSF_min depends only on liver volume, lung mass, Liver_max, and LMD_max, while PV size plays no role. Using 120 Gy Liver_max and 30 Gy LMD_max, 29 (10%) treated cases had clinical LSF_planar > LSF_min. Even at a lower LMD_max of 20 Gy {3}, only 7 (2%) treated cases had clinical LSF_SPECT > LSF_min. Based on observed clinical LSF distributions, cases with HCC tumors ≤8 cm maintained a median (max) probability of 0% (5%) for LSF_SPECT to exceed LSF_min.

Conclusion: In a great majority of cases it is Liver_max that limits the achievable PV dose, with LSF and LMD_max playing no relevant role. Cases amenable to single-compartment treatment planning, with small to medium HCC or non-HCC tumors (< 8 cm), and without confounding factors like TIPS or MVI are highly unlikely to benefit from a patient-specific LSF using MAA. It may therefore be plausible to extend “no-MAA” ⁹⁰Y-SIRT workflows {4-7} to a larger patient population.