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Published on: June 5, 2019
Evaluation of the reproducibility of lung motion probability distribution function (PDF) using dynamic MRI
Jing Cai1, Paul W Read, Talissa A Altes
1Department of Radiation Oncology, The University of Virginia, Charlottesville, VA, and Department of Radiology, Children's Hospital of Philadelphia, PA, USA.
Physics in Medicine and Biology
|January 5, 2007
Summary
This study found that longer scan times improve the reproducibility of probability distribution functions (PDFs) for lung structures. Higher frame rates also enhance PDF accuracy, crucial for radiation therapy planning.
Area of Science:
- Medical Imaging
- Radiation Oncology
- Computational Biology
Background:
- Probability distribution functions (PDFs) of patient geometries are vital for offline treatment planning to account for organ motion.
- The clinical utility of PDF-based approaches hinges on the reproducibility of these functions.
Purpose of the Study:
- To investigate how magnetic resonance (MR) imaging acquisition parameters, specifically scan time and frame rate, influence the reproducibility of lung structure displacement PDFs.
- To provide guidance for acquiring reliable MR-based PDFs for lung structures in radiation therapy planning.
Main Methods:
- Three healthy subjects underwent 5-minute sagittal MR scans at a frame rate of ~10 frames/sec, repeated over several weeks.
- Nine pulmonary vessels across different lung regions were tracked to evaluate PDF displacement reproducibility.
- The impact of varying scan times and frame rates on PDF reproducibility and accuracy was analyzed.
Main Results:
- PDF reproducibility error decreased with increased scan duration, approaching equilibrium within 5 minutes for some subjects.
- PDF accuracy showed a power-law increase with higher frame rates.
- PDF reproducibility exhibited less sensitivity to frame rate changes, likely due to the dominant effect of breathing randomness.
Conclusions:
- Prolonged scan times enhance the reproducibility of lung PDFs, a critical factor for dosimetric accuracy in PDF-based treatment planning.
- While higher frame rates improve PDF accuracy, scan time appears more critical for reproducibility in the context of respiratory motion.
- This research offers essential insights for optimizing MR imaging protocols for generating robust lung PDFs for radiotherapy.
