Medical imaging
In 1972, engineer Godfrey Hounsfield from the British company EMI invented the X-ray computed tomography device for head diagnosis. This machine projected X-rays through a section of the human head and processed them by computer to reconstruct a cross-sectional image known as image reconstruction. The CT nucleus method allowed doctors to see inside the body without cutting it open. Before this invention, physicians relied on plain X-rays that showed overlapping structures in two dimensions. The new technology enabled clear acquisition of tomographic images of various parts of the human body. In 1975, EMI successfully developed a CT device for the entire body. This revolutionary diagnostic technique earned Hounsfield and physicist Allan Cormack the Nobel Prize in Physiology or Medicine in 1979. Digital image processing technology for medical applications was inducted into the Space Foundation's Space Technology Hall of Fame in 1994.
A magnetic resonance imaging instrument uses powerful magnets to polarize and excite hydrogen nuclei of water molecules in human tissue. The MRI machine emits a radio frequency pulse at the resonant frequency of the hydrogen atoms on water molecules. Radio frequency antennas send the pulse to the area of the body to be examined. When the RF pulse is turned off, the protons relax back to alignment with the primary magnet and emit radio waves in the process. This radio-frequency emission from the hydrogen atoms on water is what is detected and reconstructed into an image. Unlike CT, MRI does not involve the use of ionizing radiation and is therefore not associated with the same health hazards. For example, because MRI has only been in use since the early 1980s, there are no known long-term effects of exposure to strong static fields. However, there are well-identified health risks associated with tissue heating from exposure to the RF field and the presence of implanted devices in the body. Medical ultrasound uses high frequency broadband sound waves in the megahertz range that are reflected by tissue to varying degrees to produce images up to three dimensions. This is commonly associated with imaging the fetus in pregnant women but also includes abdominal organs, heart, breast, muscles, tendons, arteries and veins.
Elastography emerged in the last two decades as a relatively new imaging modality that maps the elastic properties of soft tissue. Cancerous tumours will often be harder than the surrounding tissue, and diseased livers are stiffer than healthy ones. There are several elastographic techniques based on the use of ultrasound, magnetic resonance imaging and tactile imaging. Photoacoustic imaging is a recently developed hybrid biomedical imaging modality based on the photoacoustic effect. It combines the advantages of optical absorption contrast with an ultrasonic spatial resolution for deep imaging. Recent studies have shown that photoacoustic imaging can be used in vivo for tumor angiogenesis monitoring, blood oxygenation mapping, functional brain imaging, and skin melanoma detection. Magnetic particle imaging is a developing diagnostic imaging technique used for tracking superparamagnetic iron oxide nanoparticles using superparamagnetic iron oxide nanoparticles. The primary advantage is the high sensitivity and specificity, along with the lack of signal decrease with tissue depth. MPI has been used in medical research to image cardiovascular performance, neuroperfusion, and cell tracking.
The global market for manufactured devices was estimated at 5 billion dollars in 2018. Notable manufacturers included Fujifilm, GE HealthCare, Siemens Healthineers, Philips, Shimadzu, Canon, Carestream Health, Hologic, United Imaging, and Esaote. In 2016, the manufacturing industry was characterized as oligopolistic and mature; new entrants included Samsung and Neusoft Medical. In 2024, Fischer MVL in India began manufacturing MRI machines. Other companies in India include Allengers, Skanray, and BPL Medical Technologies. In 2016, Toshiba exited the industry by selling its medical imaging division to Canon, which was ultimately renamed to Canon. In 2019, Hitachi exited the industry by selling its business to Fujifilm for about 1.6 billion dollars. The simpler x-ray machines were being commoditized by 1998, when Kodak had about 30% market share globally. Kodak later sold its medical imaging business in 2007 and the business was ultimately renamed to Carestream Health. In the 1970s, CT scanners were introduced, followed by MRI machines in the 1980s, with GE leading in both.
Medical imaging has become a major tool in clinical trials since it enables rapid diagnosis with visualization and quantitative assessment. A typical clinical trial goes through multiple phases and can take up to eight years. Clinical endpoints or outcomes are used to determine whether the therapy is safe and effective. Once a patient reaches the endpoint, he or she is generally excluded from further experimental interaction. Imaging biomarkers have shown to facilitate the use of small group sizes, obtaining quick results with good statistical power. For example, measurement of tumour shrinkage is a commonly used surrogate endpoint in solid tumour response evaluation. This allows for faster and more objective assessment of the effects of anticancer drugs. In Alzheimer's disease, MRI scans of the entire brain can accurately assess the rate of hippocampal atrophy, while PET scans can measure the brain's metabolic activity by measuring regional glucose metabolism. An imaging-based trial will usually be made up of three components: a realistic imaging protocol, an imaging centre that is responsible for collecting the images, perform quality control and provide tools for data storage, distribution and analysis, and clinical sites that recruit patients to generate the images to send back to the imaging centre.
Radiation exposure from medical imaging in 2006 accounted for about 50% of total ionizing radiation exposure in the United States. Medical imaging can lead to patient and healthcare provider harm through exposure to ionizing radiation, iodinated contrast, magnetic fields, and other hazards. Lead is the main material used for radiographic shielding against scattered X-rays. At higher dosages, effects can include miscarriage, birth defects and intellectual disability. In pregnancy, Magnetic resonance imaging without MRI contrast agents as well as obstetric ultrasonography are not associated with any risk for the mother or the fetus. February 2016 Projectional radiography, CT scan and nuclear medicine imaging result some degree of ionizing radiation exposure, but have with a few exceptions much lower absorbed doses than what are associated with fetal harm. There are well-identified health risks associated with tissue heating from exposure to the RF field and the presence of implanted devices in the body. These risks are strictly controlled as part of the design of the instrument and the scanning protocols used.
In the United States the Health Insurance Portability and Accountability Act sets restrictions for health care providers on utilizing protected health information. While there has not been any definitive legal decision in the matter, many studies have indicated that medical imaging contain biometric information that can uniquely identify a person. The UK General Medical Council's ethical guidelines indicate that the Council does not require consent prior to making recordings of X-ray images. As per chapter 300 of the Compendium of U.S. Copyright Office Practices, the Office will not register works produced by a machine or mere mechanical process that operates randomly or automatically without any creative input or intervention from a human author. In Germany, X-ray images as well as MRI, medical ultrasound, PET and scintigraphy images are protected by related rights or neighbouring rights. This protection does not require creativity and lasts only for 50 years after image creation if not published within 50 years. The Cyber Law in Sweden states that pictures can be protected as photographic works or as photographic pictures depending on the level of originality required.
Common questions
Who invented the X-ray computed tomography device for head diagnosis in 1972?
Engineer Godfrey Hounsfield from the British company EMI invented the X-ray computed tomography device for head diagnosis in 1972. This machine projected X-rays through a section of the human head and processed them by computer to reconstruct a cross-sectional image known as image reconstruction.
When did Magnetic resonance imaging instruments begin use and what are their safety characteristics compared to CT scans?
Magnetic resonance imaging has been in use since the early 1980s and does not involve ionizing radiation unlike CT scans. There are no known long-term effects of exposure to strong static fields but well-identified health risks exist regarding tissue heating from RF field exposure and implanted devices.
What is the global market value for medical imaging manufactured devices estimated at in 2018?
The global market for manufactured medical imaging devices was estimated at 5 billion dollars in 2018. Notable manufacturers included Fujifilm, GE HealthCare, Siemens Healthineers, Philips, Shimadzu, Canon, Carestream Health, Hologic, United Imaging, and Esaote.
How much radiation exposure from medical imaging occurred in the United States during 2006?
Radiation exposure from medical imaging in 2006 accounted for about 50% of total ionizing radiation exposure in the United States. Medical imaging can lead to patient and healthcare provider harm through exposure to ionizing radiation, iodinated contrast, magnetic fields, and other hazards.
Which countries have regulations protecting medical images as copyright or related rights?
Germany protects X-ray images as well as MRI, medical ultrasound, PET and scintigraphy images under related rights or neighbouring rights that last 50 years after image creation if not published within 50 years. The Cyber Law in Sweden states that pictures can be protected as photographic works depending on originality levels while the UK General Medical Council does not require consent prior to making recordings of X-ray images.