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Physics Today September 2002
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| Physics Today September 2002 Radiation in the Treatment of Cancer by: Arthur L. Boyer, Michael Goitein, Antony J. Lomax and Eros S. Pedrone This article outlines the improvement and physics perspective of radiation. It states that high energy x-rays are the most effective type of radiation. The radiation enters the patient and leaves parts of the doses in the tissues as it passes through the body to the tumour. It explains that the units of measurement of strength of radiation are grays 1Gy=1J/Kg. It shows that cell death is caused by the interaction of secondary electrons set loose by the primary interaction of the rays. Protons, another type of radiation, is only successful up to an energy dependent depth contrary to x-rays. The higher the dose of any radiation increases the chance of causing cell death. These cells that are killed are the cancerous ones as well as the healthy ones. To limit the death of healthy cells the radiation is given in small daily doses called fractions. Typically this is a 30 to 40 daily fractions of 2 Gys. Single rays of x-rays distribute more radiation in front of the tumour than the actual tumour so to limit morbidity of healthy cells the tumourous area is hit from all sides with x-rays. There are many points which radiologists agree on the topics of tumours. One is that the larger the tumour the more radiation needed to control it and the more morbidity of healthy cells. Two, tumours should be eradicated uniformly because it is more beneficial to the control of the tumour. Third, each area does not need to get a uniform amount of radiation as it may benefit to have a different dose. Research continues to increase effectiveness of radiation while diminishing healthy cell morbitity. This article was a nice summary of x-rays and their use in radiation therapy today. It was informative and was easy to follow. Research in this field is still needed to help all the poor folks today that are dealing with tumours. Physics Today, September 2002 Treating Cancer With Protons by: Michael Goitein, Antony J. Lomax, and Eros S. Pedroni Ideal radiation would have a near-uniform dose that only hits the target areas of the tumour. This however is impossible. But, this method that was suggested by Robert Wilson in 1946 proposes that protons would be as close to the ideal as possible. Several countries today are building proton therapy centres for cancer treatment. Protons lose energy as they pass through tissue and gradually deposit the dose. As the protons slow down the energy which they distribute because greater. Protons also interact with the nuclei of the molecules which makes it so more dose is deposited locally. The technique of multiple Coulumb scattering is also useful because it gains great width without great width in rays. The proton accelerator is usually attached to several treatment rooms and the vast size of treatment centres make them a thing of the present and future. The three types of systems used to supply the source of protons are cyclotrons, synchrotrons and linear accelerators have been suggested also. The first two are the systems that are prevalent today. Because the cost of these treatment centres, there is a common search for ways to minimise the costs. One of the most costly parts of the treatment centre is the rotating beam for around the patient. Tumours frequently are near important organs thus they system must be accurate to 0.5mm which means the equipment must be very accurate. The beam size that is most commonly used for treatments is 5-8mm. In certain placed tumours a scanning system is used to make sure the tumour is hit even if there is movement caused by respiration. New systems are to be made where the beam can follow the tumour in real time. Multiple fields of proton rays are used to increase success. Proton therapy has been used since 1950s to treat 30 000+ patients. Most widely treated ailment with this system is cancer of the retina. At Massachusetts General Hospital 5000+ people have been treated with a 98% TCP (Tumour Control Probability). With surgery the percentage was only 90% TCP. Helium Ions are also being used for similar therapy. This article summarises how proton therapy works, the problems with it and the success rates. It is very informative and was relatively easy to follow for a grade twelve physics student. Proton therapy is a really interesting field of physics which combines laboratory work with real life medical research. After reading both of these articles I have come to the conclusion that depending on the location of the tumour and its size it will depend on which type of therapy will be used. However, in Saskatoon, the capacity for proton therapy has yet to be established making the options slimmer. |