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Medical imaging could be described as the different techniques and processes that allow to see the interior of a body, for clinical analysis and/or medical intervention. It is a visual representation of the aspect and function of organs and tissues.
Although we take that kind of technology for granted in this day and age, it was not always the case. In fact, until the very end of the XIXth century, it was nothing short of a miracle.
The whole concept famously started in 1895, with the discovery of X-rays by Wilhelm Röntgen. In fact, it was more of a happy accident. He was making cathode rays travel through vacuum tubes that were under high voltage. It was not a new experiment by any means. However, he, unlike his peers, was experimenting in total darkness and he noticed afterwards that a nearby photosensitive screen had reacted. He deduced that the experiment device was emitting some sort of radiation. We know them today as X-rays, X standing for “unknown”.
Its usefulness was undeniable in medical imaging. Where simple X-rays had little contrast and nuance, CT scans allowed better resolution, more detail, and above all, imaging and reconstruction of soft tissues.
Improvements were developed, such as increased scan speed, decreased radiation doses, smaller slice thickness for better resolution, and even 3D reconstructions in three different planes. All these innovations allow us today to obtain contrasted 3D reconstructions of soft tissues with anatomic details that are highly useful for diagnosis.
Its applications were also expanded with CT angiography to observe blood vessels, cardiac CT to examine the heart, or CT perfusion to differentiate healthy from damaged tissues in the brain.
One of the latest developments in the field is spectral CT, also known as dual-energy CT. It uses two separate X-ray energy spectra, allowing the observation and analysis of materials that have different attenuation properties at different energies. X-rays react differently with matter according to their energy spectra, which improves the contrast and resolution of the images.
Illustration of material differentiation without dual-energy CT (a), or with dual-energy CT (b). Adapted from Hsieng et al., 2021.
Moreover, AI and dep-learning technologies could further expand the possibilities of CT, and already started doing so, with automatic anatomy-aligned reconstruction for example.
Today, in the United States alone, around 80 million CT scans are performed in a year, and this number is expected to grow despite the health risks that radiation still poses.
CT is now a technique with a large range of applications, as well as highly standardized acquisition guidelines, and operator independence, which makes CT an excellent tool for anatomic imaging endpoints in clinical trials.
- Vardeu MF, Larentis O, Vecchio I, Gorini I, Martini M, Bragazzi N, D'Ambra A, Ruggieri M, Tornali C. History of use and abuse of X-ray: the early 20th century Italian pediatrics school. Acta Biomed. 2020 Mar 19;91(1):113-117. doi: 10.23750/abm.v91i1.8646.
- Scatliff JH, Morris PJ. From Roentgen to magnetic resonance imaging: the history of medical imaging. N C Med J. 2014 Mar-Apr;75(2):111-3. doi: 10.18043/ncm.75.2.111.
- Hsieh J, Flohr T. Computed tomography recent history and future perspectives. J Med Imaging (Bellingham). 2021 Sep;8(5):052109. doi: 10.1117/1.JMI.8.5.052109. Epub 2021 Aug 11.
- Bradley, William. (2008). History of Medical Imaging. Proceedings of the American Philosophical Society. 152. 349-61.
