The Future of Radiotherapy

The progress radiation therapy has been making over the last century is because now we can better aim and deliver radiation to tumors. This improvement has come from physics discoveries and the vast improvements in technologies available. But as far as it has come, there is plenty scope for left for further improvements, for example the improvements in image guided radiotherapy and four dimensional motion management that will come with fast MRI imaging. There is also more scope for improvements in efficiency and cost effectiveness, as most of the treatment machines are in the range of millions upwards.

The success of radiotherapy has been based on the ever improvement of technology. Fueling the field with new inventions and treatment techniques. So what are the current improvement in technology that will become the future of radiotherapy and undoubtedly improve patient treatment outcomes.

Cyberknife Radiosurgery Robot

The first is actually quite old. It’s a machine called Cyberknife. A fully robotic radiosurgery machine using a 6 MegaVoltage x-ray beam to precisely target tumors. We have all heard the hype about surgical robots, well, the radiosurgery robots however, has been in use since 2001. Even though it has been around for a number of years now, it still deserve a mention. The cyberknife offers many benefits over the traditional Linear accelerator. It offers the ability to target the tumor from 100’s of different directions and has the ability to deal with respiratory motion. Both these abilities allows the surrounding healthy tissue to be spared.

Although these machine are rare (~250 units worldwide), to date, over 100000 patients have been treated. Cyberknife provides a pain free, non surgical option for patients who have tumors which are inoperable or surgically complex. As well as patients wanting an alternative to surgery.

Magnetic Resonance Imaging Linear Accelerator

The second big technological advance in the field of radiotherapy is the merger of Magnetic Resonance Imaging and Linear accelerators to create a hybrid machine- the MRI Linac. The field of radiotherapy has always merged different machines together to build one superior machine. One of the most notable one is the merging of CT techniques into Linear accelerators, opening up the radiotherapy technique of image guided radiotherapy. Allowing radiation therapists and Radiation Oncologists to see the target at the moment of treatment.

The MRI Linac will push the technology of image guided radiotherapy to a completely new level. MRI gives much better soft tissue contrast when compared to CT scans. This allows a better assessment of the target at the moment of treatment over traditional CT scans. One of the other advantages is that MRIs do not use ionizing radiation. RAdiation delivered for therapy is generally very targeted to hit the target, imaging radiation from CT scans is not targeted. RAther it exposes the entire area to be imaged. There is not a huge radiation dose delivered per CT scan, but a patient will normally undergo anywhere up to 38 radiotherapy treatments. There will be no dose associated with MRI linac pre treatment imaging.

There are currently 7 research groups around the world developing the MRI Linac. It’s not a simple bolt two machines together. This is because the magnets in the MRI machine interfere with the method used in the Linac’s electron accelerating process. This has been one of the main issues with merging these machines. Although this is not the only difficulty. The radiation dosimetry is also made more complex with the existence of a permanent magnet. Radiation dosimetry relies on capturing electrons charge, but the magnet will deflect the electrons. Developing a process of precisely measuring the dose output is also needed.

The first to get an MRI linac onto the market is Elekta, with release expected late 2017. Currently Elekta has 6 instalments of these machines, with most still under functional evaluation. The Elekta MRI linac promises to move image guided radiotherapy form only taking an image scan prior to treatment to imaging during treatment. This allows radiation therapists and radiation oncologists to watch the patient’s internal anatomy in real time. Allowing quick response to any changes of internal anatomy during treatment.

Heavy Ion and Proton Accelerators

Proton Therapy Machine

The third technological advancement in radiotherapy is the development of proton and heavy ion treatment machines. Traditionally, all radiotherapy would use either x-rays, gamma rays, and occasionally electrons. The advantage of moving to protons and heavy ion treatment is a physical phenomenon know as the bragg peak. Proton and heavy ions deliver the majority of their dose within a small range inside the tumor, known as the bragg peak, whereas x-rays and gamma rays tend to deliver dose along their entire path through the body.

Proton therapy has been around for a while, with the number of installations sites increasing. The number of proton treatments in 2015 was roughly 16500, this is expected to increase to 300000 by the year 2030. The major bottleneck to date is that these machines are very expensive, and take up a lot of space. The machines themselves are as big as a small three story building.

The widespread uptake of heavy ion therapy using carbon and helium ions is even further in the future than proton therapy, mainly due to their eye watering cost estimate of over 300 million US per machine. Most of these facilities around the world are research facilities. Heavy ions as very similar to protons, however there bragg peak is even more beneficial for cancer treatment than protons. However, the Japanese groups using carbon ions have over 20 years of successful radiotherapy treatments.

Since the 1960s, the Linear accelerator has dominated radiotherapy due to its versatility and relative affordability. This, however, may be changing with the ever increasing array of different treatment machines, and the decrease in price once the technology matures. Cyberknife, along with others devices such as tomotherapy and gamma knife, are delivering larger proportion of radiotherapy treatments with every year. Once the MRI becomes available in the near future it will further decrease the proportion of radiotherapy delivered by traditional Linacs. And in the distance future, proton and heavy ion facilities may render Linacs as obsolete.

Thanks for reading this post, I hope that it was interesting and you learned something new about where radiotherapy may be heading. Please leave any feedback or question that you have in the comments section below! Or send me a message! I can’t wait to read them!

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RRR

Originally published at www.radicalradiationremedy.com on January 23, 2017.