Use of radiation to treat cancer
Image-guided Radiation Therapy (IGRT)
The image shows the tumour in different positions at different times, demonstrating the need for the radiation beam to be turned on and off depending on the exact location of the tumour.
4D-RT
- 4D-RT uses 4D imaging (taking time dimensionality into account) and tracks the tumour as it moves, capturing real-time images of the motion.
- Using advanced computer programs, the beam is trained to turn off as the tumour moves out of the treatment field and turn back on again when it is suitably positioned[40].
- An example of a current alternative way to deal with moving tumours is to restrict the patients breathing with a heavy metal cage placed on the chest. This prevents the tumour from moving more than around 1cm from the base position and allows the majority of the radiation to reach the target.
- Thanks to the time sensitive imaging, 4D-RT offers a kinder alternative to this, and although is not widely accessible currently, it almost certainly holds a very important place in the future of IGRT.
MRI-LINAC
- MRI-LINAC is a system which combines a linear accelerator with radiation delivery equipment which allows real-time imaging of the tumour site and surrounding area as treatment is happening[41].
- This allows specialists to adapt and monitor the treatment, minimising unnecessary exposure to healthy tissue. This has also allowed higher doses to be used as the precision is improved and constantly monitored during treatment.
- As MRI uses non-ionising radiation, it is a good, safe method of imaging, reducing radiation exposure and is a recent development of IGRT. It is likely to have a pivotal role in the future of radiotherapy.
What are the benefits of IGRT?
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Increased precision
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Improved tumour monitoring and control
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Minimal exposure to healthy organs and tissues surrounding a targeted tumour
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Shorter treatment schedules
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Good for tumours close to vital organs and in areas of high movement such as the heart, kidneys and abdominal areas.
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Safe administration of higher radiation doses
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Images are analysed and compared to previous ones so that each dose of radiotherapy can be modified and specifically targeted.
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Makes it possible to account for the tumour shrinking over time or moving during a patient’s natural breathing cycle.