Adaptive motion mapping in pancreatic SBRT patients using Fourier transforms. Issue 2 (May 2015)

• Record Type: Journal Article
• Authors: Jones, Bernard L.; Schefter, Tracey; Miften, Moyed
• Is Part Of: Radiotherapy and oncology. Volume 115:Issue 2(2015:May)
• Page Start: 217
• Page End: 222
• Publication Date: 2015-05
• Subjects: Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2015.03.029
• Languages: English
• ISSNs: 0167-8140

Abstract

<abstract xml:lang="en" abstract-type="author" id="ab005"> <title id="st125">Abstract</title> <sec> <title id="st090">Background and purpose</title> <p id="sp0005">Recent studies suggest that 4DCT is unable to accurately measure respiratory-induced pancreatic tumor motion. In this work, we assessed the daily motion of pancreatic tumors treated with SBRT, and developed adaptive strategies to predict and account for this motion.</p> </sec> <sec> <title id="st095">Materials and methods</title> <p id="sp0010">The daily motion trajectory of pancreatic tumors during CBCT acquisition was calculated using a model which reconstructs the instantaneous 3D position in each 2D CBCT projection image. We developed a metric (termed "Spectral Coherence, " SC) based on the Fourier frequency spectrum of motion in the SI direction, and analyzed the ability of SC to predict motion-based errors and classify patients according to motion characteristics.</p> </sec> <sec> <title id="st100">Results</title> <p id="sp0015">The amplitude of daily motion exceeded the predictions of pre-treatment 4DCT imaging by an average of 3.0 mm, 2.3 mm, and 3.5 mm in the AP/LR/SI directions. SC was correlated with daily motion differences and tumor dose coverage. In a simulated adaptive protocol, target margins were adjusted based on SC, resulting in significant increases in mean target D95, D99, and minimum dose.</p> </sec> <sec> <title id="st105">Conclusion</title> <p id="sp0020">Our Fourier-based approach differentiates between consistent and inconsistent motion characteristics of respiration and correlates with daily motion deviations from pre-treatment 4DCT. The feasibility of an SC-based adaptive protocol was demonstrated, and this patient-specific respiratory information was used to improve target dosimetry by expanding coverage in inconsistent breathers while shrinking treatment volumes in consistent breathers.</p> </sec> </abstract>