Related Experiment Video
Updated: Jun 7, 2026
08:17
Dynamic Lung Tumor Tracking for Stereotactic Ablative Body Radiation Therapy
Published on: June 7, 2015
15.7K
Multileaf collimator characterization and modeling for a 1.5 T MR-linac using static synchronous and asynchronous
Roel G J Kierkels1, Victor Hernandez2, Jordi Saez3
1Radiotherapiegroep, Arnhem/Deventer, The Netherlands.
Physics in Medicine and Biology
|February 27, 2024
Summary
A new step-and-shoot asynchronous sweeping gap (aSG) test accurately characterizes the Elekta Unity MR-linac's multileaf collimator (MLC). The RayStation treatment planning system (TPS) model showed better agreement with experimental data than the Monaco TPS.
Area of Science:
- Medical Physics
- Radiotherapy Technology
- Radiation Oncology
Background:
- The Elekta Unity MR-linac utilizes an Agility multileaf collimator (MLC) for step-and-shoot intensity-modulated radiotherapy.
- Detailed characterization of the physical Unity MLC and its computational models in treatment planning systems (TPS) like Monaco and RayStation is lacking in published literature.
- Novel dynamic synchronous and asynchronous sweeping gap (aSG) tests offer a method to characterize MLC physical properties.
Purpose of the Study:
- To develop a step-and-shoot version of the dynamic aSG test for characterizing the Elekta Unity MLC.
- To evaluate the accuracy of computational MLC models within the Monaco and RayStation TPSs using the developed step-and-shoot aSG test.
Main Methods:
- Discretized dynamic aSG tests into step-and-shoot aSG tests by optimizing segment number and monitor units (MU) per segment.
- Compared step-and-shoot aSG tests with dynamic aSG tests on a conventional linac, simulating Unity's source-to-detector distance.
- Characterized the Unity MLC and its TPS models through experimental measurements and dose calculations.
Main Results:
- Step-and-shoot aSG tests with 100 segments and 5 MU/segment closely replicated dynamic aSG test results.
- The Unity MLC exhibited an increasing effective tongue-and-groove width up to 1.4 cm from the leaf tip.
- The RayStation MLC model agreed with experimental data within 2.0%, while the Monaco model showed a 10% discrepancy, particularly with significant leaf interdigitation.
Conclusions:
- The developed step-and-shoot aSG tests provide accurate characterization of MLC performance in step-and-shoot delivery mode.
- The RayStation 2023B MLC model effectively captures tongue-and-groove and leaf tip effects.
- The Monaco TPS model tends to overestimate tongue-and-groove shadowing, especially at greater distances from the leaf tip end.
Related Concept Videos
01:07Electron Microscope Tomography and Single-particle Reconstruction
Transmission electron microscopy (TEM) can be used to determine the 3D structure of biological samples with the help of techniques such as electron microscope tomography and single-particle reconstruction. While single-particle reconstruction can examine macromolecules and macromolecular complexes in vitro conditions only, tomography permits the study of cell components or small cells in vivo.
Electron Tomography
Electron tomography can be performed either in TEM or STEM (scanning transmission...
Electron Tomography
Electron tomography can be performed either in TEM or STEM (scanning transmission...
01:17Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.