Abstract
PurposeMagnetic Resonance (MR)‐guided online adaptive radiation therapy (MRgOART), enabled with MR‐Linac, has potential to revolutionize radiation therapy. MRgOART is a complex process. This work is to introduce a comprehensive end‐to‐end quality assurance (QA) workflow in routine clinic for MRgOART with a high‐magnetic‐field MR‐Linac.Materials and MethodThe major components in MRgOART with a high‐magnetic field MR‐Linac (Unity, Elekta) include: (1) a patient record and verification (R&V) system (e.g., Mosaiq, Elekta), (2) a treatment session manager, (3) an offline treatment planning system (TPS), (4) an online adaptive TPS, (5) a 1.5T MRI scanner, (6) an 7MV Linac, (7) an MV imaging controller (MVIC), and (8) ArtQA: software for plan data consistency checking and secondary dose calculation. Our end‐to‐end QA workflow was designed to test the performance and connectivity of all these components by transferring, adapting and delivering a specifically designed five‐beam plan on a phantom. Beams 1–4 were designed to check Multi‐Leaves Collimator (MLC) position shift based on rigid image registration in TPS, while beam 5 was used to check daily radiation output based on image pixel factor of MV image of the field. The workflow is initiated in the R&V system and followed by acquiring and registering daily MRI of the phantom, checking isocenter shift, performing online adaptive replanning, checking plan integrity and secondary 3D dose calculation, delivering the plan while acquiring MV imaging using MVIC, acquiring real‐time images of the phantom, and checking the delivering parameters with ArtQA. ResultsIt takes 10 min to finish the entire end‐to‐end QA workflow. The workflow has detected communication problems, permitted resolution prior to setting up patients for MRgOART. Up to 0.9 mm discrepancies in isocenter shift based on the image registration were detected. ArtQA performed the secondary 3D dose calculation, verified the plan integrity as well as the MR‐MV isocenter alignment values in TPS. The MLC shapes of beam 1–4 in all adaptive plans were conformal to the target and agreed with MV images. The variation of daily output was within ±2.0%.ConclusionsThe comprehensive end‐to‐end QA workflow can efficiently check the performance and communication between different components in MRgOART and has been successfully implemented for daily clinical practice.
Highlights
Magnetic Resonance (MR)‐guided online adaptive radiation therapy (MRgOART) with MR‐Linac 1–3 is clinically available
The major components in the MRgOART daily quality assurance (QA) workflow with the Unity system include: (1) a daily QA patient, (2) a patient record and verification (R&V) system, (3) a treatment session manager (TSM), (4) an offline treatment planning system (TPS), (5) an online adaptive TPS, (6) a 1.5T MRI scanner, (7) a 7MV Linac, (8) an MV imaging controller (MVIC), and (9) ArtQA software.[6]
A 3D reference plan with five static‐field beams was generated with offline Monaco TPS as follows: a) The reference image was shifted by 1.0 cm, 1.2 cm and −1.5 cm in x, y and z directions, respectively; b) beams 1‐4: the Multi‐Leaves Collimator (MLC) shapes were conformed to four ZrO2 spheres at different orthogonal gantry angles 00, 900, 1800 and 2700; c) beam 5: a 5 × 5 cm[2] field with 100 MU at gantry 00 was used for daily output check based on the fact that the image pixel factor (IPF) of the MV image is correlated to the accumulated radiation during MV imaging
Summary
Magnetic Resonance (MR)‐guided online adaptive radiation therapy (MRgOART) with MR‐Linac 1–3 is clinically available. This technology has potential to significantly improve radiation therapy (RT) outcomes by providing excellent soft‐tissue contrast images, biological and functional information, and high‐quality real‐time image guidance during RT delivery. Compared to conventional RT, MRgOART with MR‐Linac is a more complex process involving the treatment delivery system and the patient R&V system, and online MR imaging system, online treatment planning system (TPS) and online quality assurance (QA) system. It is critical to check all the functionalities and communications of each major component of the MR‐Linac system in advance to ensure accurate and efficient MRgOART in the clinic
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