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Medical use of radiation

Medical use of ionising radiation for diagnosis and therapy is now an important underpinning of a modern health service. The NRPA has the administrative control by the use of such radioactive sources.

The use of radiation sources in Norway is governed by the Act of 12 May 2000 on Radiation Protection and Use of Radiation and Regulations of 21 november 2003 on Radiation Protection and Use of Radiation, which is administered by the Norwegian Radiation Protection Authority.

Norway has about 32 health care enterprises including about 85 somatic hospitals with 1,500 X-ray apparatuses for radiology diagnosis. These devices have widely varying applications and functionality. Most of the equipment is pure photography devices used to take X-rays of the skeleton, the urinary system, the lungs and heart.

Some of these devices have image enhancers or other type of detectors, making it possible to obtain moving images and thereby document dynamic processes (e.g. the gastrointestinal and circulatory systems) or monitoring surgical treatment. In dynamic examinations it is usual to feed or inject the patient with contrast agents that emphasise anatomy and pathological processes. In gastrointestinal examinations, barium is a commonly-used contrast agent, sometimes used together with air. In examination of blood vessels, or the urinary system, contrast agents including iodine are common.

An X-ray apparatus that has become increasingly significant is the CT Scanner. In contrast to conventional devices, a modern CT scanner is excellent in soft tissue imaging and it has also significant post-processing capabilities. The CT scanners will also take over much of the traditional barium imaging in the near future. There are now about 125 CT installations in Norway.

Mammography experienced rapid growth in the number of examinations from the end of the 1980s. This trend continued with the gradual phasing in of the national breast screening programme, which began as a trial project in 1995 and by early 2004 reached full national coverage. Mammography equipment is tailor made to this particular imaging task, including the film and screens used in analogue mammography. Since digital mammography equipment was introduced on the market around the turn of the century, this has become the technology of choice for most sites investing in new equipment. Typical of mammography is that it makes great demands on the technology and performance of the apparatus and the expertise of the personnel. Around 100 mammography systems are currently in use in Norway. Approximately half of these are used in the Norwegian Breast Cancer Screening Program, the remainder is mainly used for clinical mammography in public hospitals and private X-ray clinics.

There are about 500 smaller radiology facilities at medical centres, chiropractors and veterinarians, and many thousands used by dentists.

The last decade has seen a trend towards digital detectors, which will form the basis for the film-less hospital. Radiology images are “captured” electronically and subsequently transmitted over an IT network (PACS), processed, displayed on monitors and stored digitally. X-ray film imaging is seldom seen in hospitals today.

More than three million X-ray examinations are made in Norway every year, excluding those done by dentists.

In nuclear medicine examinations, the patient is fed or injected with radio-isotopes (for example Tc-99m or I-131) that are linked to various pharmaceuticals which are absorbed by the organ it is wished to investigate. The radionuclide that emits radiation can then be registered from outside the patient with the aid of a gamma-ray camera. In scintigraphy or isotope examinations as they are also called, the primary object is to study the functioning of an organ, but an image of the anatomical and structural features of the organ may also be obtained. There are about 25 nuclear medicine departments in Norway, possessing 60-70 devices, of which two are now based on positron emission tomography (PET).

The commonest form of external radiation therapy is radiation treatment with the aid of linear accelerators that generate very high-energy radiation. Before the patient is treated a dose planning session is held. The trend is now towards the combination of different kinds of image-generation equipment, for example devices that show physiological processes transparently over the top of anatomic pictures taken with different equipment, thus enabling the special features of each modality to be exploited. The actual treatment itself may be causal, that is, be oriented to the cause of the sickness, but is also effective in palliative treatment with a view to ameliorating symptoms (pain relief etc.) caused by the condition. Linear accelerators are state of the art and expensive, and there are about 27 at Norwegian oncological centres.

Nuclear medicine is also used in therapy such as internal irradiation of patients. Examples here are Sr-90 treatment of skeletal metastases and I-131 treatment of cancer thyroidea. Other methods of internal treatment are by means of brachytherapy devices, of which there are four in Norway. Here various radio-isotopes such as Ir-192 are used; they are dosed and applied to the patient via the device in bodily cavities, organs or blood vessels.

The border between diagnosis and therapy is in some contexts rather diffuse. In intervention radiology, X-ray diagnostics are used for guidance and monitoring in connection with the treatment of patients. This has led to a number of conditions that used to be treated by surgery now being subject to intervention radiology. In many cases this means fewer complications for the patient and enhanced cost-effectiveness for the health service.

In diagnostic radiology, too, there is also an extensive use of apparatus based on non-ionising radiation. There are about 100 tomographs based on magnetic resonance (MR) and 1,800 ultrasound devices. Most ultrasound is intended for diagnosis, but there are also some forms of therapy. In addition come about 100 surgical and 25 therapeutic lasers.