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Dynamic Contrast Enhanced Magnetic Resonance Imaging of an Orthotopic Pancreatic Cancer Mouse Model
Published on: April 18, 2015
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Modeling pancreatic tumor motion using 4-dimensional computed tomography and surrogate markers
Florence Huguet1, Ellen D Yorke2, Margaret Davidson2
1Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York; Department of Radiation Oncology, Hôpitaux Universitaires Paris Est, Hôpital Tenon, University Paris VI, Paris, France.
International Journal of Radiation Oncology, Biology, Physics
|February 15, 2015
Summary
Respiratory gating significantly reduces radiation therapy margins for pancreatic tumors. Biliary stents and fiducial seeds accurately track tumor motion, improving treatment accuracy and patient outcomes.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Oncology
Background:
- Pancreatic tumors exhibit significant respiratory-induced motion, complicating accurate radiation therapy delivery.
- Accurate assessment of tumor motion is crucial for optimizing treatment margins and ensuring effective dose coverage.
- Respiratory gating techniques aim to minimize motion artifacts and improve treatment precision.
Purpose of the Study:
- To evaluate intrafractional positional variations of pancreatic tumors using 4D-CT.
- To assess the impact of tumor motion on gross tumor volume (GTV) coverage during radiation therapy.
- To determine the reliability of biliary stents, fiducial seeds, and real-time position management (RPM) markers as surrogates for GTV motion during respiratory gated treatment.
Main Methods:
- Analysis of respiration-correlated 4D-CT images from 36 patients with locally advanced pancreatic cancer.
- Measurement of respiratory displacement for GTV, biliary stent, fiducial seeds, and RPM markers relative to end-exhalation.
- Comparison of motion between the full respiratory cycle and the gating interval using linear mixed models to correlate GTV motion with surrogate markers.
Main Results:
- Average GTV excursions measured: 0.3 cm (left-right), 0.6 cm (anterior-posterior), and 1.3 cm (superior-inferior).
- Respiratory gating reduced GTV motion by 46%–60%.
- GTV displacement showed good correlation with RPM markers, biliary stents, and fiducial seeds, with better correlation observed for fiducial seeds and biliary stents.
Conclusions:
- Respiratory gating effectively reduces the required margins for pancreatic tumor radiation therapy.
- Biliary stents and fiducial seeds are reliable surrogates for assessing GTV position during treatment, validating their use in daily setup.
- Patient-specific internal target volumes derived from 4D-CT are recommended; alternatively, a predictive model for GTV motion can be utilized.
