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Innovations in Oncology & Imaging Q1 2024

How image-guided radiotherapy targets tumours with pinpoint accuracy

iStock / Getty Images Plus / Mark Kostich

The Revd Canon Dr. Mike Kirby

Senior Lecturer, Liverpool University

Written together with Sarah-Jane Ketterer (Liverpool University) and Rob Julian (OSL) on behalf of the BIR Radiotherapy and Oncology Special Interest Group

Learn about the evolution of radiotherapy precision with image-guided technology and how it enhances treatment accuracy and minimises side effects.

Radiotherapy uses cutting-edge technology to precisely deliver radiation exactly where it’s needed: inside the tumour. In addition to advanced diagnostic imaging before treatment, image-guided radiotherapy (IGRT) is now also performed during treatment delivery — our answer to ‘seeing’ inside the patient during treatment.

Before image-guided radiotherapy

Not long ago, imaging wasn’t used during treatment. Instead, we relied on skin marks for guidance. Then, we started using the treatment beam itself, acquiring 2D images inside the body, making placement more accurate.

However, the physics is against us when using these beams, giving poor image quality and clarity. Now, we use separate lower energy X-ray beam equipment attached to the treatment machine to produce the staple of modern IGRT — a cone-beam computed tomography image; visualising inside the body in 3D and enabling positioning with submillimetre precision.

IGRT enhances treatment effectiveness

The more accurately we can direct the treatment beams, the more effective the treatment becomes. By treating a much smaller volume of tissue (focusing on just the tumour) we can reduce the dose to the normal tissues nearby, sustaining quality of life and reducing short- and long-term side effects.

The more accurately we can direct the treatment
beams, the more effective the treatment becomes.

Precision without extra radiation

Sounds easy; but it’s taken decades to perfect, and the story continues. We can now combine the treatment machine with magnetic resonance imaging — giving even better clarity, without any extra radiation. With such advances, alongside improving computing power, we can now do more than just ensure the planned beam is well-aligned. We can adapt the treatment on a daily basis with each, new image, optimising treatment by accommodating individual changes including weight loss or bladder filling.

Surface-guided radiotherapy efficiencies

Are old methods obsolete? Not quite; the patient’s skin surface may still help. Surface-guided radiotherapy integrates advanced 3D surface monitoring techniques for on-treatment verification; hastening the patient setup process and monitoring motion throughout treatment.

Techniques boosting radiotherapy precision

These techniques form the present and future of IGRT for our patients. As these developments progress, more patients will benefit from enhanced treatment efficacy. Meanwhile, artificial intelligence is enhancing image quality, aiding adaptive processes and even tracking/compensating for internal motion. Coupled with particle beam therapy, rather than X-ray-based therapy, we’re entering a new era in radiotherapy efficacy — bolstering our fight against cancer.

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