Physics in Medicine and Biology· 2017Q2
First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment
- 535citations
- Q2SCImago
- 2017year
Short summary
The first clinical prototype of a 1.5 T MRI-guided radiotherapy machine (MRI-Linac) has successfully treated four patients with lumbar spine bone metastases, demonstrating high precision.
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Key points
- First clinical treatment of patients using a 1.5 T MRI-Linac prototype.
- High precision achieved: geometric targeting better than 0.5 mm.
- High dosimetric accuracy: absolute dose deviations between 0.0% and 1.7%.
- Patients treated had lumbar spine bone metastases.
- Treatment planning was performed online based on real-time MRI images.
AI-generated from the title and abstract; the full text is not read.
Abstract
The integration of 1.5 T MRI functionality with a radiotherapy linear accelerator (linac) has been pursued since 1999 by the UMC Utrecht in close collaboration with Elekta and Philips. The idea behind this integrated device is to offer unrivalled, online and real-time, soft-tissue visualization of the tumour and the surroundings for more precise radiation delivery. The proof of concept of this device was given in 2009 by demonstrating simultaneous irradiation and MR imaging on phantoms, since then the device has been further developed and commercialized by Elekta. The aim of this work is to demonstrate the clinical feasibility of online, high-precision, high-field MRI guidance of radiotherapy using the first clinical prototype MRI-Linac. Four patients with lumbar spine bone metastases were treated with a 3 or 5 beam step-and-shoot IMRT plan. The IMRT plan was created while the patient was on the treatment table and based on the online 1.5 T MR images; pre-treatment CT was deformably registered to the online MRI to obtain Hounsfield values. Bone metastases were chosen as the first site as these tumors can be clearly visualized on MRI and the surrounding spine bone can be detected on the integrated portal imager. This way the portal images served as an independent verification of the MRI based guidance to quantify the geometric precision of radiation delivery. Dosimetric accuracy was assessed post-treatment from phantom measurements with an ionization chamber and film. Absolute doses were found to be highly accurate, with deviations ranging from 0.0% to 1.7% in the isocenter. The geometrical, MRI based targeting as confirmed using portal images was better than 0.5 mm, ranging from 0.2 mm to 0.4 mm. In conclusion, high precision, high-field, 1.5 T MRI guided radiotherapy is clinically feasible.
The authors' abstract, as published at the source. Physics in Medicine and Biology, 2017 · DOI ↗
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Field: Radiation
RadiationPhysics and Astronomy