Examining that mechanism one can clearly see that this technology requires significant hardware to achieve maximum energy for the electrons. Whilst, the technology has proven compatible with electrons (due to their size), the same success has not been achieved with higher energy particles such neutrons, protons and ions (for example carbon ions). Using Linacs for proton or neutron acceleration would be possible, but would require significant hardware investment. This is in spite of the table of characteristics provided showing that heavier particles have greater efficiency.
Over the past few years however, there has been renewed interest in the optimization of the heavier particle processes due to their inherent advantages. One particular technology that has showed potential to make this class of particles useful is radiotherapy is the cyclotron. Although invented in the 1930s, the technology has not seen its full potential utilized in the area of radiotherapy, yet it has proven capable of propelling heavier particles such as protons and lately the even heavier carbon ions.
Cyclotrons use circular acceleration instead of linear acceleration, which is the dominant technology in radiotherapy as of now. The cyclotron was conceived in the third decade of the 20th century by E. O. Lawrence. The idea behind the Cyclotron was to hold particles in a circular orbit by means of a magnetic field then subject them to sequential electrostatic acceleration by means of a magnetic field. A simple cyclotron set up to produce radiation is shown below:
The important components to note from this prototype are the semi-circular shaped ‘Dees’ that act as the electrodes and the hollow shaped evacuated chamber. To start off, a potential difference is applied to the ‘Dees’ in such a manner that the positive ions created at the centre source (as indicated) are accelerated as they cross the gap between the ‘Dees. ’ The action is repeated every time the particles are cross the gaps so that each time there is a circular acceleration exerted on the particles.
An improvement to this kind of cyclotron is the addition of electromagnets and klystrons to speed up the particles (Freudenrich, 2008). In addition, there may be an additional linear accelerator to give the particles an initial acceleration before it enters the circular chamber. Each manufacturer will take different approaches in improving the cyclotron, but the bottom line is that the particles should attain optimal speeds possible. How a cyclotron can be used in cancer treatment The importance of the cyclotron in the fight against cancer has not escaped the eyes of the researchers.
Its use has however, in the past, been limited by the few number of machines available, complexity and cost of the cyclotron and a general lack of expertise (Laughlin, 2010). That appears to be changing as there has been a steady rise in the use of cyclotrons in the treatment of cancer. According to (Jones, 2007), proton therapy centers are now coming up worldwide with countries such as China, Austria, Italy, France and Japan being amongst the countries keen to domesticate the technology. The application principle of the proton therapy is essentially the same (abnormal cell destruction), but comes with added benefits.
One of the distinct benefits of using the proton therapy is that protons have predictable energy. X-rays are have no charge, and for that reason, as they travel across the skin towards the tumor they tend to distribute their energies evenly. That brings about the target problem with the X-rays whereby they tend to end up destroying normal cells as well. This is in contrast with the protons, which emit energy when they reach their peak energy. This peak is known as Bragg peak (Koreaittimes, 2007).
That means, if the Bragg peak for a particular group of protons can be predicted then it is possible to know at what point the streams will release their energy. For that reason, proton therapy allows for energy to be concentrated at the point of the tumor so that little or damage occurs beyond the targeted cells. This mechanism wastes very little energy, meaning that most or all the energy is devoted to destroying the cancer cells. Consequently, protons deliver the most damage to the cancer cells and it has also been found that people treated with cancer cells experience very little reoccurrence of the cancer.
One of the beneficiaries of proton therapy would be those suffering from tumors affecting delicate body parts such as the spine and the brain. Apart from allowing for proton therapy, cyclotrons will allow for use of heavier particles such as carbon-11. Although proton therapy has been hailed as an equally efficient treatment, carbon-11 has shown higher potential. According to (Jones, 2007), a trial in Japan showed that one to four weeks of carbon ion treatments were needed as opposed to the four to six to seven weeks that would be needed for the X-rays to be effective.
Properly developed cyclotron technology will therefore provide the benefit of exploring the benefits associated with the carbon-11 ions and other heavy particles, which cannot be used because of the limitations associated with widespread linear accelerator technology. Simply put, the cyclotron has limitless possibilities. Prominent among these is the ability to allow for much heavier particles to be used and at the same there is the possibilty that the sequential circular motions that produce the acceleration can be altered to excert much higher velocity to the particles.
In fact, protons from the cyclotrons achieve speeds that are close to that of light. Given the direct proportion between energy and velocity, then it is right to conclude that particle energy potential is limitless. Cost considerations Cost estimations for the cyclotron technology in medical physics cannot be divorced from that of heavier particles therapy, and more specifically carbon-11 and proton therapy. First note is that the advantages associated with the cyclotron must come at a price; otherwise X-rays would have been obsolete by now.
The radiotherapy market dynamics are not clear, but according to (Marketplace, 2009), Proton therapy cost 50% more than X-ray therapy. It would however be unfair to look at the difference in isolation; the high cost is accompanied by fewer therapies, more efficiency and reduced side effects. Although it may not be possible to comprehensively quantify the benefits associated with the proton therapy, it nevertheless appears that its benefits can justify or even outstrip the costs. Hence, it is safe to say that the proton therapy will provide a better deal to the cancer patients.
Conclusion As with other technologies, increases in the prevalence of cyclotrons will eventually lead to reduced costs. The indication so far is that the cyclotron technology will allow for new possibilities in the arena of radiotherapy, but will lead to increased costs. Part of the fear for X-rays has always been based on its destructive possibilities on normal cells. Patients always fear that the same destructive power used by the rays to destroy abnormal cells can turn against the normal cells.
This is a problem that is greatly reduced by the cyclotron technology. This kind of precision will even allow for higher energies to be used in the destruction of these cells because of the precision possible with the technology. Costs should therefore not be such an inhibition when it comes to this technology. In any case, with time, economies of scale will start to accrue, something that will lead to reduced costs and better efficiencies. One can also be sure that with time, much heavier particles will find their way in to the cyclotrons.
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