How do health care and industry utilize radiation?
Radiation is widely used in health care, veterinary medicine and industry. In healthcare, radiation is used to examine and treat people. Some applications of radiation in health care are imaging, radiotherapy and radionuclide therapy. Industry and research use radiation for studies and measurements that use sealed sources, unsealed sources and X-ray equipment.
X-ray examinations are the most common imaging examinations. X-ray examinations are based on the fact that while X-radiation passes through tissues, it is attenuated in different ways depending on the tissue type. An X-ray examination is particularly suitable for imaging lungs, bones and teeth, since these tissues attenuate X-radiation well. As a result, they can be easily distinguished in the images. In contrast, soft organs or tissues do not attenuate X-radiation much, so X-radiation is not very well suited for examining them. The visibility of blood vessels or intestines in the images can be improved by using an intravenous or intestinal contrast agent.
The most common X-ray examination is an intraoral X-ray scan of the teeth, which images a single tooth or a few adjacent teeth. The entire set of teeth and the jawbones can be scanned by what is called panoramic X-ray imaging. In recent years, Cone Beam Computed Tomography (CBCT) imaging of teeth has become more common. It creates an accurate three-dimensional view of the entire set of teeth or a smaller area.
X-rays are often used to examine the lungs and bones. These examinations are usually performed with a conventional X-ray device, which can be a fixed device installed in the scan room or a mobile device. For more accurate three-dimensional X-ray images, a computed tomography (CT) scan or a CBCT scan can be performed.
Interventional image guided procedures can be performed as a real-time X-ray fluoroscopy, for example when there is a need to monitor the flow of a contrast medium in the body. Interventional image guided procedures are also performed in operating theatres with mobile fluoroscopic equipment. Imaging of blood vessels is called angiography. Imaging of the heart or coronary arteries is called X-ray cardiography or coronary angiography.
Nuclear medicine examinations
Nuclear medicine examinations use radioactive drugs, also called radiopharmaceuticals. A radiopharmaceutical agent consists of a pharmaceutical preparation that contains a radiation-emitting radionuclide. The most common nuclear medicine examinations are tumour imaging, examinations of skeletal and soft tissues and examinations of the cardiovascular system.
Radiopharmaceuticals are usually administered as an injection into the bloodstream. In certain cases, they can be administered orally as a capsule or inhaled as an aerosol. Metabolism carries the radiopharmaceutical to the tissue or organ being examined. This allows the physicians to detect any changes in organ function and metabolism. Many disorders of organ functions can be detected by nuclear medicine examinations at a very early stage.
The accumulation of radioactivity in the organ or tissue being examined can be monitored with cameras that detect the gamma radiation emitted by radiopharmaceuticals. Traditional isotope imaging uses gamma cameras to obtain two-dimensional images, while single photon emission computed tomography (SPECT) can be used to obtain three-dimensional images.
Positron emission tomography (PET) can be used with radiopharmaceuticals that emit positrons. It produces a three-dimensional image that can be combined with a CT examination if necessary. This also increases the diagnostic precision of the examination as the distribution of the radiopharmaceutical in the body can be seen in more detail.
Radiotherapy and radionuclide therapy
Radiotherapy is a common cancer treatment that is often combined with surgery and chemotherapy. Radiotherapy uses high-energy radiation that destroys cancer cells and shrinks tumours by damaging the structures of the dividing cells. Because cancer cells divide faster than healthy cells, they are particularly sensitive to the effects of radiation.
Radiotherapy is usually given from outside the body with a radiotherapy device called a linear accelerator. The radiation is precisely targeted to hit the tumour. This is called external radiotherapy. In internal radiotherapy with the high dose rate (HDR) source, the radiation source is placed inside the body close to the cancer tumour for a few minutes. A patient who has received external or internal HDR radiotherapy can be discharged immediately because he or she does not emit radiation after the therapy session.
In radionuclide therapy, the patient is typically given radiopharmaceuticals that migrate into the cancerous tumour. Radionuclide therapy can be used, for example, to curb hyperthyroidism or treat thyroid cancer. Compared to nuclear medicine examinations, the radiopharmaceuticals used in radionuclide therapies have a significantly higher activity and a longer half-life. Therefore, the recipient of the radiopharmaceutical and his or her excretions might radiate for some time after the therapy has been administered. After radionuclide therapy, it is important for the patient and his/her family to follow the instructions given by the hospital.
Veterinary examinations and therapies
The use of radiation has increased also in veterinary practices. For example, X-ray devices and dental X-ray installations, are now basic tools of a veterinarian. CT scans have also become more common in veterinary clinics in recent years. X-ray examinations are most commonly performed on dogs, cats or other small pets. However, X-ray examinations can also be performed on larger animals, such as horses and farm animals. Some X-ray examinations are performed at veterinary clinics in a separate X-ray room, while some are performed with mobile equipment, for example in horse stables.
Successful X-ray imaging requires the animal to stay still during the scan. This is why the animal is often sedated or anaesthetized during the examination. If this is not possible, the owner, veterinarian or caretaker can hold the animal during the scan. It is important ensure the radiation safety of the person holding the animal, the clinic staff and other people during the scan.
Radiation can also be used to treat hyperthyroidism in cats. Hyperthyroidic cats are given radioiodine therapy. After the therapy, the cat should be kept in isolation in the veterinary clinic until the level of radioactivity in the cat’s body has fallen sufficiently. Even after this, it is important to avoid close contact with the cat for a period of time stated by the veterinarian. In addition, the cat’s droppings should be handled with special care after treatment. This avoids unnecessary radiation exposure.
Industry and research
Use of sealed sources
Sealed sources are most commonly used in the process industry as radiometric measuring devices, i.e. as level switches, level sensors or weighing systems on conveyors. Level switches and level sensors are used for determining how full a tank or silo is or for preventing a tank or silo from being drained empty of its contents, such as fuel. In these applications, the level switch or level sensor also contains a detector mounted on the other side of the tank or silo.
Sealed sources can also be used for measuring moisture content and density, for example in soil.
Another application for sealed sources is quality control, for example, in the film manufacturing and paper industry. In these cases, sealed sources are used to measure the surface weight of the product, such as pulp or paper.
Sealed sources are also used as calibration sources for radiation meters and for verifying their operation.
Use of x-ray equipment
X-ray equipment are used extensively in the quality control of the food industry, for example. The most commonly used X-ray equipment for quality control is an X-ray fluoroscopy device used to ensure that no foreign objects are present in the food. Another common application of X-ray equipment is the security screening of baggage at airports or ship terminals. These kinds of X-ray equipment are often shielded to prevent the operator of the device or other people near the device from being exposed to radiation.
X-ray equipment are also used to determine the composition of various materials. For example, scrap yards can use X-ray equipment to determine the elemental composition of recycled metals. X-ray equipment can also be used for soil research, either in field measurements or in laboratory conditions. The X-ray equipment used in these applications are typically mobile devices.
X-ray equipment are also used for non-destructive testing (NDT imaging). Examples of the items being inspected are welded seams or castings. In these kinds of scans, the X-ray equipment is on one side of the object to be scanned and the film or sensor is on the other side. NDT inspections are carried out in specially constructed imaging rooms or in the field, for example in industrial facilities.
Use of unsealed sources
Unsealed sources are radioactive sources in which the radionuclides are not packaged in metal capsules or other sealed sources. Unsealed sources can be solids, liquids or sometimes gases.
An example of unsealed sources are radiopharmaceuticals used in nuclear medicine. They can be used for diagnostics, i.e. disease investigations, or for therapy. Unsealed sources are used in universities and other research institutes as tracers. Unsealed sources are used in preclinical drug research or biochemical research, for example, in various metabolism studies.
Radiopharmaceuticals and radioactive tracers used in nuclear medicine and research consist of a radioactive nuclide that is incorporated into another compound, such as a drug or a nutrient molecule.
Unsealed sources are used as tracers to study the migration of substances, for example, in pipelines or industrial processes. The radioactive tracer is fed into the process and its flow is monitored with a radiation meter.