Radiation is a double-edged sword for healthcare. The high-energy waves can be used to examine bones in X-rays and destroy tumors, but the same high-energy rays can be destructive, burning skin and damaging internal organs without any outward sign.
X-rays are a form of electromagnetic radiation, similar to but more intense than infrared, ultraviolet or microwaves. Radiation therapy uses X-rays and gamma rays delivered in a beam of high-energy light by an external source. Today, around 50 per cent of cancer patients benefit from radiation therapy in the treatment and management of their disease.
The rays actively divide cells in DNA and also oxidize water to make free radicals, which diffuse to the DNA. Splitting a double strand in the DNA in a tumor cell will kill it.
There are different modes of radiotherapy, from low-energy KV, to high-energy (MV) X-rays for deeper penetration, to electron beam and cobalt therapy, using gamma rays. There is also brachytherapy, which uses radioactive sources in localized tumor tissues and at varying energy levels. The nature of radiation therapy means that it can also affect healthy tissue around the tumor. Making it more precise enables the radiation dose to be increased and to reduce the treatment time.
A process called stereotactic body radiation therapy (SBRT) uses image guidance and 4D CT scanning to establish the precise location of tumors in organs such as the lungs or liver. Traditional radiation therapy uses a larger target area with wider margins around the tumor to accommodate movement.
In SBRT, the patient wears a belt to monitor respiration during the CT scan, and the beams can be turned on and off as the tumor moves within the field of interest. Mapping the location of the tumor allows the maximum doses of radiation to be applied from multiple angles and aimed at the most active part of the tumor.
Research at UCLA (University of California, Los Angeles) has found that SBRT has a control rate of 90 per cent compared with 30 per cent with traditional radiation therapy in lung cancer patients. It is also used to treat liver cancer. Some patients are cured and do not need surgery, but for those who do need a transplant, UCLA reports primary evidence suggesting that patients treated before a transplant have a low rate of recurrence.
Radiation can also be administered internally via brachytherapy. This is when sealed radioactive ‘seeds’ are implanted to deliver radiation at a short distance. They can be placed between tissue and an organ (interstitial), inside a body cavity, for example the windpipe or rectum, or applied on the surface, to treat skin cancer.
Since the 1980s, synthetic radionuclides or radioactive isotopes have been used in these seeds. There is caesium-137, iridium-192, gold-198, which has a half-life of less than three days, and iodine-125, which has a half-life of 60 days. The radioactive seeds are encased in titanium and range from the size of a large sesame seed to a grain of rice (4.5 x0.8 mm is common).
There is also research into using automatic devices that are remote controlled to deliver radiation. Brachytherapy can be combined with radiation delivered by an external beam or as a standalone treatment, depending on the cancer.
Proton beam therapy represents a real advance in how high-energy rays are administered. Locating the precise position of a tumor for conventional radiation therapy allows high-energy rays to be fired directly into it. Although effective on the tumor, healthy tissue between the skin and the tumor is at risk of radiation damage. Rays fired in proton beam therapy peak before suddenly fading away – an effect called the Bragg peak. This minimizes damage to surrounding tissue.
To deliver the proton beams, an accelerator increases the speed of protons in a cyclotron to 160,000 km per second before directing the beam via electromagnets to a treatment gantry and then through a nozzle positioned against the patient, who is lying still on a robotically controlled table. The nozzle fires at hundreds of tiny spots within the tumor in just 26 seconds. The nozzle can be repositioned to repeat the process to attack the tumor from a different angle.
The therapy is being used for tumors in sensitive areas, such as the brain and spine, allowing high doses on specific areas. To ensure pinpoint accuracy of this intense beam, calibration marks are tattooed on the patient to line up the tumor with the lasers in the proton beam therapy pod. It can take more than 15 minutes to position the patient for less than one minute of treatment. The treatment is administered daily over a period of weeks.
Researchers at Johns Hopkins University School of Medicine in Maryland, USA, have found that treating spinal tumors with a series of doses, rather than a single large one, helps prevent vertebral compression fractures. Radiation and tumors can weaken the bones in the spine, explained Timothy With am MD, director of the Johns Hopkins Medicine Spinal Fusion Laboratory, pointing out that fractures can complicate or delay recovery.
The researchers administered a single dose of 24 gray GY, to one test group of rabbits and delivered three doses of 8Gy each to another group. A control group received no radiation. It was found that the bones in the second group were less impacted and that bone samples receiving a single dose broke more easily than those given the same amount of radiation over separate sessions.“Based on this study, we can immediately recommend that oncologists use fractional radiation dosage in their practices and, hopefully, prevent further suffering,” concludes With am.
Treatment has reached the limit of radiation, so rather than increasing the dose, other research is investigating how to optimize the effects of the radiation. In 2010, a study published in Radiation Research found that gold nanoparticles introduced intravenously around the site of the tumor accumulated in the tumor and interacted with X-ray photons still present from the radiation treatment. Together, these interact with water molecules to produce free radicals which damage the tumor cells. By boosting the effects of radiation, the tumor’s ability to recover and repair was limited without the radiation dose being increased.
When it decays, radium emits radon gas. In the 1930s, mine workers reported that some chronic conditions, such as arthritis, were eased as a result of exposure to radon. It has been claimed that the gas acts on the body’s endocrine system to encourage production of hormones and steroids that help the body heal, though radon is also a known cause of lung cancer.
In the US today, former gold, silver and copper mines in Montana operate as health mines. Visitors sit in or walk the mines for an hour at a time, accumulating a total of 30 hours exposure to radon during their stay. Spas in Austria, Germany and Poland offer radon bathing, water for drinking and therapy tunnels (in caves or former mine areas).
The health benefits of radon exposure are a contentious issue. Visitor testimonials report relief from chronic ailments including asthma, arthritis, carpal tunnel syndrome, fibromyalgia, eczema, and psoriasis. The US Environmental Protection agency, however, says that there is no safe level of radon and that any exposure poses some risk of cancer.
Radiation’s ability to kill bacteria means that fruit can be exposed to beams of radiation. This is called irradiation and is different from contamination by radioactive material. Fruit is typically irradiated using cobalt-60 gamma rays. The radiation destroys any bacteria, but will not change the fruit.
Doses of gamma or neutron radiation can also be used to create plant mutations. Crops can be modified to resist disease, tolerate drought or harsh environments, increase yield, or have shorter growing times to increase harvests.
Low doses can make fresh fruit and vegetables, cereals, and root crops resistant to infestation by insects and parasites. Medium doses (1-10kGy) can extend the shelf life of fish, poultry and meat and fleshy produce like strawberries and mushrooms. High doses (10-50kGy) are used for industrial sterilization and decontamination of meat, poultry, seafood, prepared food and spices.
In addition to being able to grow crops in inhospitable areas, genetically modified crops may require fewer chemicals, such as pesticide and insecticide, during cultivation.
Radiation is also used to control insect populations. The insects are sterilized through irradiation with X-rays or gamma rays and introduced to their natural habitat. One benefit of this sterile insect technique (SIT) is that it does not introduce non-native species into an ecosystem. SIT has been used to eradicate the Mediterranean fruit fly in Mexico, Argentina and Chile and the parasitic screw worm in southern US, Mexico, Central America, and Panama.
Ionizing radiation is also used in manufacturing to sterilize materials, components, and packaging. There are two processes typically used. Gamma irradiation can be used for batches of product in a fixed location, or a conveyor belt can transport products into a radiation cell for exposure as they pass through. The other process is high - energy electron irradiation, or beta radiation, from an accelerator. Products are conveyed past a beam of high-energy electrons, which is transmitted back and forth across the conveyor belt.
In the art world, radiation is used to learn more about the creation of artworks and also to unmask forgeries.
X-ray fluorescence (XFR) is a technique to determine the chemical composition of works of art. Subjecting the work to high - energy gamma or X-rays destabilizes the electrons, which emit radiation. This radiation is different depending on the chemical compound. Analyzing the radiation can identify what chemical elements were used in paint. For example, XRF was used to determine where a painting attributed to Leonardo da Vinci had been retouched long after it was originally painted. Da Vinci used lapin lazily for his blue pigments, and while this was present, there was also cobalt blue, but this artificial pigment was not available during da Vinci’s lifetime.
In London used X-rays to show the progression of works for a 1986 exhibition, ‘The Hidden Face of Manet’. In his celebrated painting, ‘A Bar at the Folios Bergère’, X-ray pictures highlight the original position of the central character’s arms. Originally, Manet depicted the barmaid with her arms crossed instead of resting on the bar as they appear in the final painting.
White paint contains lead and is used for flesh tones, so the original positioning of faces as well as arms and legs can be exposed under X-rays. Other metallic pigments are cadmium and cobalt (blue) and mercury (vibrant red, vermilion).
Other X-rays show the addition of a cat at the end of a bed in Olympia, and the changing landscape.
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