Related Experiment Video
Updated: Feb 23, 2026
08:17
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
16.3K
Performance of a multi leaf collimator system for MR-guided radiation therapy
Bin Cai1, Harold Li1, Deshan Yang1
1Department of Radiation Oncology, Washington University, St. Louis, MO, 63110, USA.
Medical Physics
|September 10, 2017
Summary
This study evaluated the Multi Leaf Collimator (MLC) for MR-guided radiation therapy, finding it has good RF shielding, low leakage, and accurate positioning. Its performance is reliable for advanced cancer treatments.
Area of Science:
- Medical Physics
- Radiation Oncology
- Magnetic Resonance Imaging
Background:
- MR-guided radiation therapy integrates MRI with linear accelerators for real-time tumor tracking.
- Multi Leaf Collimators (MLCs) are crucial for shaping radiation beams, but their performance in strong magnetic fields requires careful evaluation.
Purpose of the Study:
- To characterize the performance of a Multi Leaf Collimator (MLC) designed for a Cobalt-60 based MR-guided radiation therapy system operating in a 0.35 T magnetic field.
Main Methods:
- Evaluated RF cage shielding using ACR phantoms and SNR.
- Assessed dosimetric characteristics (leaf transmission, penumbra, tongue-and-groove effect) using radiosensitive films.
- Measured output factors for symmetric and asymmetric fields, positional accuracy (picket fence, rectangular patterns), leaf speed, and plan delivery reproducibility.
Main Results:
- Demonstrated comparable signal-to-noise ratios (SNRs) within 4% for MLCs in magnetic fields.
- Reported maximum leaf transmission <0.35% and leaf positioning accuracy of 0.2 cm.
- Achieved gamma passing rates >96% for positional accuracy and >98% for IMRT plans, indicating high delivery accuracy.
Conclusions:
- The MRIdian MLC exhibits effective RF noise shielding and low radiation leakage.
- The system demonstrates good positioning accuracy and comparable tongue-and-groove effects.
- The MLC performance can be reliably modeled using independent Monte Carlo calculations.
