Magnetic Resonance Imaging-Guided Radiation Therapy Systems

Magnetic resonance imaging-guided radiation therapy systems integrate high-resolution soft-tissue imaging with precision radiotherapy delivery to enhance tumour targeting and minimise exposure to healthy tissues. By combining a magnetic resonance imaging (MRI) scanner with a linear accelerator (linac), these systems provide continuous real-time visualisation of the treatment site, allowing adaptive modification of the radiation beam in response to anatomical changes or organ motion. The superior soft-tissue contrast of MRI obviates the need for implanted fiducial markers and reduces uncertainties inherent in conventional image-guided approaches. Online adaptive workflows exploit on-table MRI scans to re-optimise treatment plans on a fraction-by-fraction basis, while intrafraction monitoring detects and compensates for physiological motion such as respiration. Emerging applications include functional MRI biomarkers for early treatment response, magnetic resonance spectroscopic guidance and integration with particle therapy. Collectively, these advances support personalised radiotherapy with the potential to improve local control, reduce toxicity and expand the therapeutic window across a broad range of tumour sites.

Research from Nature Portfolio

Recent studies have demonstrated the potential of ionising radiation acoustic imaging for real-time volumetric mapping of dose delivery during treatment. By employing a matrix array ultrasound transducer and preamplification electronics, three-dimensional dose accumulation can be visualised as it occurs, validated firstly in tissue-equivalent phantoms and subsequently in vivo in animal models. This approach was translated to clinical use with a linear accelerator, achieving dynamic, three-dimensional dose monitoring in a patient with liver metastases. The ability to directly image dose deposition promises enhanced adaptive control of radiotherapy, offering a novel feedback mechanism to ensure conformity and to adjust treatment parameters in real time.

Magnetic Resonance Imaging-Guided Radiation Therapy Systems publication trend

The graph below shows the total number of articles in magnetic resonance imaging-guided radiation therapy systems across all publications each year (not limited to Nature Index journals).

Technical terms

Magnetic resonance imaging-linac (MRI-Linac): A hybrid system combining MRI and a radiotherapy linear accelerator for simultaneous imaging and treatment delivery.

Online adaptive radiotherapy: Real-time modification of the treatment plan based on daily imaging to account for anatomical or positional changes.

Synthetic CT (sCT): A computationally generated CT-equivalent image derived from MRI data, used for dose calculation in MRI-only treatment workflows.

Organs-at-risk (OARs): Healthy tissues or organs whose radiation exposure must be minimised to prevent undue toxicity.

Planning target volume (PTV): A geometrical concept that encompasses the tumour with an added margin to account for setup uncertainties and motion.

References

1. Real-time, volumetric imaging of radiation dose delivery deep into the liver during cancer treatment. Nature Biotechnology (2023).
2. First patients treated with a 1.5 T MRI-Linac: clinical proof of concept of a high-precision, high-field MRI guided radiotherapy treatment. Physics in Medicine and Biology (2017).
3. Phase I trial of stereotactic MR-guided online adaptive radiation therapy (SMART) for the treatment of oligometastatic or unresectable primary malignancies of the abdomen. Radiotherapy and Oncology (2017).
4. Generating synthetic computed tomography for radiotherapy: SynthRAD2023 challenge report. Medical Image Analysis (2024).