International Standards and Conformity Assessment for all electrical, electronic and related technologies

April 2014

 

Taking a clear and safe look inside…

Medical imagery has made a major contribution to medicine for over a century

Morand Fachot

Medical imaging, used to visualize the interior of patients' bodies, is an indispensable tool that allows doctors to diagnose and treat internal illnesses and traumatic injuries, such as fractures. International Standards for many of the systems and technologies used in medical imaging and for the performance and safe operation of imaging equipment and systems are prepared by several IEC TCs (Technical Committees) and their SCs (Subcommittees).

Technological expansion into multiple segments

Ever since the application of X-rays for medical imaging was discovered in the late 19th century, the diagnostic imaging domain has made dramatic advances with the introduction of new technologies, which have allowed it to expand well beyond its initial limitations. Medical imaging is currently divided into five main groups of systems, on the basis of their modality:

  • X-ray imaging
  • CT (computed tomography)
  • Ultrasound
  • MRI (magnetic resonance imaging)
  • Nuclear imaging

These categories are themselves segmented into sub-categories:

  • X-ray and ultrasound imaging systems are based on the type of technology and on the systems' portability
  • CT systems are segmented by type (high-, mid-, low-end) of slice
  • MRI systems are divided on the basis of type of architecture (open or closed) and field strength
  • Nuclear imaging systems are split into SPECT (single photon emission computed tomography) and PET (positron emission tomography) systems

The right technology for the right diagnosis

The first imaging technology used a form of electromagnetic radiation, named X-rays by German physicist Wilhelm Röntgen, who is credited with discovering their properties in 1895. X-rays are still widely used in medical imaging (including in CT), and for therapy, in particular for cancer treatment.

 

They can have adverse effects, notably an increase in cancer risk for patients who are exposed to them repeatedly. However, significant advances have been made, especially for CT scans, in terms of lowering the radiation levels to which patients are required to be exposed.

 

Ultrasound imaging uses high frequency sound waves to produce images, viewed on a screen, of internal organs, vessels and tissues. It is widely used to monitor and diagnose the condition of certain organs, such as liver, kidneys, gallbladder and even the heart. It is well known for its use in prenatal ultrasound scans, which show images of a fœtus in the mother's womb. It is considered a safe form of medical imaging technology.

 

IEC TC 87: Ultrasonics, prepares International Standards for equipment and systems in the domain of ultrasonics, primarily in the medical domain.

 

CT imaging systems use X-ray images that are then processed by a computer to produce tomographic images or "slices" to obtain three dimensional views of internal organs. As CT uses X-rays, there are adverse effects to its use, in common with X-ray imaging, but, as outlined above, modern equipment produces ever clearer images from consistently falling levels of radiation.

 

Nuclear imaging technologies are also used for tomography.

 

MRI systems use magnetic fields and radio waves to produce images of the body. The magnetic field in MRI systems is produced using magnets. The field strength of the magnet is measured in tesla units, named after Serbian-American inventor and physicist Nikola Tesla who discovered the rotating magnetic field in 1882.

 

Low-field MRI scanners use permanent magnets, making them the least expensive of these medical imaging technologies.

 

Mid- and high-field MRI scanners use superconducting magnets which need cooling at extremely low temperatures during operation. IEC TC 90: Superconductivity, prepares International Standards related to superconducting materials such as alloys, and to devices.

 

The benefits of MRI scans are lower risks to health and lower energy consumption than other technologies. However, superconducting magnets require complex cooling installations.

Performance and safety top the list

The safety and performance of the equipment used in medical imaging, as in all other medical domains, is essential to the wellbeing of the patients and medical personnel operating it.

 

The remit of IEC TC 62: Electrical equipment in medical practice, and of its SCs, is to "prepare International Standards and other publications concerning electrical equipment, electrical systems and software used in healthcare and their effects on patients, operators, other persons and the environment".

 

The activities of two of its SCs focus on imaging equipment.

 

The task of IEC SC 62B: Diagnostic imaging equipment, is "to prepare international publications for safety and performance for all kind of medical diagnostic imaging equipment (e.g. X-ray imaging equipment, computed tomography and magnetic resonance imaging equipment) including related associated equipment and accessories as well as quality procedures (e.g. acceptance tests and constancy tests) to be applied during the life-time of imaging equipment. Included is also the development of related terminology, concepts, terms and definitions".

 

Although TC 87 prepares International Standards for equipment and systems used in medical imaging, International Standards that cover the safety aspects of these are the responsibility of SC 62B and also encompass "protective devices against diagnostic medical X-radiation".

 

MRI devices pose specific problems and require particular protective measures to be taken for patients with an active implantable medical device that may contain magnetic, electrically conductive or radio frequency-reactive components.

 

SC 62B, which incorporates over 200 experts, has issued 55 publications so far.

 

The work of SC 62C: Equipment for radiotherapy, nuclear medicine and radiation dosimetry, includes the preparation of "Standards for the safety and performance of (…) nuclear medicine equipment used for imaging". SC 62C, which has 107 experts as of April 2014, has published 35 Standards so far. Half a dozen of these cover "Characteristics and test conditions of radionuclide imaging devices".

Growing market at the centre of medical advances

The overall importance of medical imaging in the healthcare environment cannot be underestimated and is illustrated by the fact that, in the past, researchers have been awarded the Nobel Prize in Physiology or Medicine for their work on two modern imaging technologies. The 2003 Prize was awarded jointly to Paul C. Lauterbur and Sir Peter Mansfield "for their discoveries concerning magnetic resonance imaging", and in 1979 it was awarded jointly to Allan M. Cormack and Godfrey N. Hounsfield "for the development of computer assisted tomography".

 

As healthcare technologies improve and find new markets in different countries, the global market for medical imaging equipment continues to expand steadily with the introduction of new systems and the phasing out of older or obsolete equipment.

 

It is expected to reach USD 32,3 billion in 2014 and to exceed USD 49 billion by 2020. IEC standardization work that covers both the design and manufacture of this equipment and ensures its safe operation will continue to contribute to the expansion of this huge and dynamic industrial sector.

 

  • Minimally invasive image-guided heart valve replacement (Photo: Philips)
  • This 57-tonne magnet will give a MRI scanner a field strength of 9,4 tesla (Siemens press photo)
  • Low-dose CT cardiac scan carried out on a six-month-old girl (© St Louis Children's Hospital Barnes-Jewish Hospital, US)

 

 

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