Significance: Internal organ motion is one of the greatest technical challenges for pancreatic cancer radiation therapy. Extensive research has been conducted on intrafractional tumor motion. This research has provided quantification and enabled novel treatment methods to mitigate motion induced adverse dosimetry effects. Compared to widely studied lung tumor motion, improving pancreas treatment accuracy has equal or greater clinical importance where the tumor is surrounded by radiosensitive serial organs, sparing of which will significantly improve our ability to deliver more effective doses to the tumor. However, organ motion management in the pancreatic cancer treatment is severely underdeveloped due to technical challenges related to poor soft tissue X-ray and CT contrast of pancreas. Fiducial markers are not commonly placed and when placed, inadequately describe complicated multiple-organ motion. Innovation: MRI guided radiotherapy has the potential to overcome these challenges utilizing gated radiotherapy based on organ distances instead of a pre-selected breathing phase. However, to enable it for such pancreatic motion management, MRI acquisition speed needs to be increased so dynamic volumetric images can be acquired with sufficient quality for organ delineation. Furthermore, methods to rapidly digest both pre- and during-treatment MRI images for clinical motion management have not been developed. Both individualized motion margin and gated radiotherapy require explicit organ segmentation but manual delineation of the large number of imaging frames is impractical. Automated segmentation tools for pancreas have not been developed but urgently needed. We will acquire accelerated 3D MRI with sufficient quality for motion quantification by exploiting the spatial and temporal coherence of patient anatomy. We will develop a novel manifold clustering constrained dictionary learning (MCDL) method to efficiently segment the MRI images and provide accurate motion assessment for pancreas anatomy. We hypothesize that the improved motion monitoring will result in significantly improved tumor dose and surrounding normal organ sparing.
Aims : 1. Develop methods to acquire 3D dynamic images from under-sampled k-space data. 2. Develop a process to auto-segment prospectively acquired accelerated MRI images by optimizing and validating a MCDL method. 3. Quantify dosimetric gains using accurately described pancreatic tumor motion. Test and robustness and deliverability of the proposed gated plans on a MRI-guided radiotherapy machine (ViewRay). Impact: Patients with locally advanced pancreatic adenocarcinoma have a dismal prognosis but the median survival can be significantly improved for patients who have complete local response. Success of the project will define more accurate patient specific motion margins and facilitate gated radiotherapy that significantly reduce critica organ doses, increase tumor doses for greater complete local response rates. Methods developed by this project will also be applicable to other tumors such as the cervical and liver cancer.

Public Health Relevance

Surgery can significantly prolong pancreatic cancer patient survival but only a small fraction of patients have resectable cancer at the time of diagnosis. High dose of radiotherapy can convert some of the nonresectable patients with locally advanced tumor to be resectable but delivery of such dose is often hampered by the lack of targeting accuracy and internal organ motion. We propose to develop MRI guided radiotherapy to overcome these challenges and deliver more effective treatment to pancreatic cancer.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA188300-02
Application #
9023515
Study Section
Radiation Therapeutics and Biology Study Section (RTB)
Program Officer
Farahani, Keyvan
Project Start
2015-03-01
Project End
2020-02-29
Budget Start
2016-03-01
Budget End
2017-02-28
Support Year
2
Fiscal Year
2016
Total Cost
$337,327
Indirect Cost
$108,577
Name
University of California Los Angeles
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
092530369
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
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