The definition of imaging is the visual representation of an object. Medical imaging began after the discovery of x-rays by Konrad Roentgen 1896. The first fifty years of radiological imaging, pictures have been created by focusing x-rays on the examined body part and direct depiction onto a single piece of film inside a special cassette. The next development involved the use of fluorescent screens and special glasses to see x-ray images in
real time.
A major development was the application of
contrast agents for a better image
contrast and organ visualization. In the 1950s, first nuclear medicine studies showed the up-take of very low-level radioactive chemicals in organs, using special gamma cameras. This medical imaging technology allows information of biologic processes in vivo. Today, PET and SPECT play an important role in both clinical research and diagnosis of biochemical and physiologic processes. In 1955, the first x-ray image intensifier allowed the pick up and display of x-ray movies.
In the 1960s, the principals of sonar were applied to diagnostic imaging.
Ultrasonic waves generated by a quartz crystal are reflected at the interfaces between different tissues, received by the
ultrasound machine, and turned into pictures with the use of computers and
reconstruction software.
Ultrasound imaging is an important diagnostic tool, and there are great opportunities for its further development. Looking into the
future, the grand challenges include
targeted contrast agents, real-time
3D ultrasound imaging, and
molecular imaging.
Digital imaging techniques were implemented in the 1970s into conventional fluoroscopic image intensifier and by Godfrey Hounsfield with the first computed tomography. Digital images are electronic snapshots sampled and mapped as a grid of dots or pixels. The introduction of x-ray CT revolutionised medical imaging with cross sectional images of the human body and high
contrast between different types of soft tissue. These developments were made possible by
analog to digital converters and computers. The multislice
spiral CT technology has expands the clinical applications dramatically.
The first
MRI devices were tested on clinical patients in 1980. The spread of CT machines is the spur to the rapid development of
MRI imaging and the introduction of
tomographic imaging techniques into diagnostic nuclear medicine. With technological improvements including higher
field strength, more
open MRI magnets, faster
gradient systems, and novel data-acquisition techniques,
MRI is a real-time interactive imaging modality that provides both detailed structural and functional information of the body.
Today, imaging in medicine has advanced to a stage that was inconceivable 100 years ago, with growing medical imaging modalities:
•
Single photon emission computed tomography (SPECT)
•
Positron emission tomography (PET)
All this type of scans are an
integral part of modern healthcare.
Because of the rapid development of digital imaging modalities, the increasing need for an efficient management leads to the widening of
radiology information systems (RIS) and archival of images in digital form in
picture archiving and communication systems (PACS).
In telemedicine, healthcare professionals are linked over a
computer network. Using cutting-edge computing and communications technologies, in videoconferences, where audio and visual images are transmitted in
real time, medical images of
MRI scans, x-ray examinations, CT scans and other pictures are shareable.
See also
Hybrid Imaging.
See also the related poll results: '
In 2010 your scanner will probably work with a field strength of', '
MRI will have replaced 50% of x-ray exams by'
•
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Further Reading:
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