By reducing particle loss in proton beams, a new method could improve the effectiveness of high-dose cancer radiation therapy and reduce patient pain.
Proton cancer therapy uses high-concentration beams to deliver extremely high doses of proton radiation directly to tumors.
Cyclotrons, a type of particle accelerator, are used to create these beams. Clinicians must adjust the proton beam energies produced by cyclotrons to therapeutically effective levels to utilize them. The researchers have now established a mechanism for this energy tuning that does not reduce the radiation dosage, which was a problem with previous techniques. According to the researchers who developed the method, practitioners can halve treatment times and thus increase patient comfort.
Maintaining the dosage is crucial when patients need to sit completely still, as in the treatment of eye tumors.
Because the proton beam distributes more of its energy directly to the tumor, proton therapy may be preferable to x-ray radiation therapy for cancer patients undergoing radiation therapy. This accuracy reduces damage to healthy tissue in the intimate area and can reduce both unpleasant short-term side effects such as nausea and fatigue, and undesirable long-term side effects such as memory problems, cardiovascular morbidity and secondary malignancies.
Radiation Dose in Cancer Treatment
The radiation dose has an effect on the effectiveness of proton therapy. Oncologists can treat more patients per hour if their treatment is more effective. As a result, the requirement for shields around the facility can be significantly reduced. However, methods currently used to produce therapeutically effective beams drastically reduce the amount of protons in a beam.
Hospital facilities install special equipment called energy reducers in the path of the proton beam to reduce its energy from 250 MeV produced by a cyclotron to 70 MeV required for various treatments. This graphite-based device scatters individual protons, lowering the average energy of the beam. However, doing so widens the energy distribution of the particle. As a result, some protons still need additional removal processes as they are too energetic to be used in treatments. Vivek Maradia of the Paul Scherrer Institute and his colleagues questioned whether they could circumvent this situation.
A technique used in high energy physics experiments was modified by Maradia and colleagues. The researchers then added a polyethylene wedge-shaped device with a width ranging from 3,8 mm at one end to a sharp point at the other after the energy reducer.
The energy lost by particles as they pass through such a wedge must depend on how much energy they had before passing through it. For example, higher energy protons must lose more energy than lower energy protons. Therefore, the protons must have similar energy when leaving the wedge. Using this apparatus, the researchers demonstrated that they could create protons with therapeutic energies and minimize particle loss without widening the energy spread.
According to Maradia, this loss reduction indicates that more particles can reach the target tumor. A potential for the treatment of eye tumors was evaluated by the team using a clinical proton beam. The researchers discovered a twofold increase in proton transmission for their configuration compared to the previous one using the clinical beam. The team's models predicted that their improved design would increase the amount of protons in a 70 MeV beam by a factor of 100, and this increase was in line with these predictions.
This technique has also been used to improve the performance of Fermilab's Muon g-2 experiment, according to Diktys Stratakis, particle accelerator designer at Fermi National Accelerator Laboratory in Illinois. According to David Neuffer, an accelerator researcher also at Fermilab, the medical proton beamline is a particularly interesting use of the wedge mechanism used for muon beams. Neuffer claims that scientists "seem like they could use this mechanism to achieve major improvements in a medical practice."
Source: physics.aps.org/articles/v16/129
📩 31/07/2023 23:09