A history full of revolutions

The first computed tomography system from Siemens was installed in 1975. It marked a small revolution - many others followed

In the early 1970s, a new imaging method revolutionized the world of medicine, touching off a wave of euphoria: computed tomography (CT). Nearly 80 years after Wilhelm Conrad Röntgen’s 1895 discovery of X-rays, this new technology was fascinating to the medical community.

The very first X-ray images thrilled people all over the world. But to medical professionals, it soon became clear that conventional X-ray images were insufficient for a number of issues. It didn’t take long before they started wanting better methods. But there was still a long way to go. The first devices to produce “slice” images without superimposition were invented back in the 1930s. These conventional tomographs included the Siemens Introskop.

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A Siemens Introskop conventional tomograph (1934)

But developing highly accurate, fast tomography methods calls for a lot more; extremely powerful computers and special algorithms to calculate images are needed. Computer technology did not reach that point until the 1960s. Research by scientists such as Allan M. Cormack, an American physicist, and British engineer Godfrey Hounsfield was also fundamental to the development of tomography technology. Hounsfield is viewed today as the father of computed tomography. He went to work in the labs of EMI, a record company, in London in 1949 and began his research on the development of CT technology in 1967. Together with his team, he built the first functioning CT system. The images it produced were so impressive that they brought an outbreak of “CT fever.” More than 15 other companies joined EMI in developing CT scanners. One of them was Siemens, which already had a wealth of know-how due to its decades of experience in X-ray technology.

A development department dedicated specifically to CT was established at Siemens in 1972. The head of the team was Friedrich Gudden, a physicist. “We worked until late at night that day,” reports Gudden in his memoirs, writing about the early years at Siemens. “I often drove many of our employees who relied on public transit home to Kleinseebach or Neunkirchen after midnight.” The goal for the group of experienced engineers was to develop a high-performance prototype. They threw themselves into their work, devoting their efforts to the development of many important subfields in CT technology: a method of reconstructing images, a completely new detector, and a system to convert images into digital ones. The engineers modified an X-ray tube for use in CT scanners, designed a new high-voltage generator, and much more.

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Prototype of the Siretom CT head scanner (1974)

Finally, in mid-1974, all of the preliminary work had been concluded, and the first CT system from Siemens, a head scanner named Siretom, was tried out in a clinical setting as a prototype following initial laboratory tests. This was the start of a close working relationship with Professor Hans Hacker and his team at the neuroradiology department at the Johann-Wolfgang-Goethe-Universität medical center in Frankfurt. They system was used to scan nearly 2,000 patients there between June 1974 and February 1975. Further improvements were made, and Hacker finally received the first series-produced unit on December 1, 1975. CT soon became the preferred method for scanning the tissue of the brain.

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The Siretom CT head scanner, the first from Siemens, in clinical use (1975)

The first whole-body CT scanners appeared on the market not long afterward. Siemens was a major force driving advances in the new technology. The first successful cardiac scans were performed soon after, in the late 1970s. Computed tomography units became faster, and image quality improved tremendously. However, the fundamental technology underwent little change in the first ten years following the introduction of the Somatom whole-body CT scanner, the first of its kind from Siemens. The areas of application broadened, and many components were optimized, but that pushed the existing technical framework to its limit. In the mid-1980s, engineers and physicians wondered what else would be possible for CT.

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Somatom, the first whole-body scanner from Siemens (1977)

Siemens found the answer in spiral CT. Previous systems had moved the patient, who was lying on the table, a little farther after capturing each slice image – a slow process. In spiral CT, the patient is continuously moved through the measuring field and through the CT scanner while the X-rays scan the body in a spiral shape and produce an image. This makes the scanning process much faster. Experts feared that this technique would produce blurred images due to movement, however. The Siemens developers ultimately solved this problem with complicated new algorithms. They made a breakthrough in 1990, launching the world’s first spiral CT scanner that was ready for the market. In the years that followed, the developers increasingly turned their focus to other challenges in this still-growing technology.

In 1995, the Somatom Plus4 was launched on the market. At the time, it was the world’s fastest scanner. It could be used for a variety of clinical purposes and did not require a lot of space. Another new development came in 1997: a special solid-state detector featuring a newly developed ceramic mixture called UFC (Ultra Fast Ceramics), which made it possible to reduce the radiation dose during CT scans by as much as 30 percent in comparison to earlier materials. By the mid-1990s, there was no longer any comparison to the early years of CT technology in terms of diagnostic quality or user and patient friendliness.

The performance of CT scanners of the time had reached its limit with regard to image quality and visualization of the volume of individual organs. But Siemens engineers found a way to put the existing performance to better use. Multislice CT made it possible to generate and capture multiple image slices at once. Because the slices were much thinner, the volume data sets available were now significantly larger.This marked an important step toward a breakthrough in cardiac CT. The first multislice scanner from Siemens was the Somatom Volume Zoom. It made it possible to produce the first CT image of the coronary vessels, which was done at the Klinikum Grosshadern facility, in Munich, in 1999. The scan took 40 seconds.

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Image of the coronary vessels generated with the Somatom Volume Zoom, courtesy of Klinikum Grosshadern, Munich (1999) 

Siemens recognized the potential of this technology early on and ramped up its efforts to push development forward, in cooperation with clinical partners, in the years that followed. Examples of these activities include the SOMATOM Sensation (2001), which offered insight into the coronary arteries with previously unknown clarity. The year 2005 brought the launch of a CT scanner that combined all of the previous innovations, but took them even farther: the SOMATOM Definition. It was the first such system in the world to use two X-ray tubes and two detectors. The system revolutionized cardiac imaging in particular. Before then, patients with a high heart rate had to take beta blockers to achieve the necessary resting heart rate to undergo a scan. Dual-source technology meant that this was no longer necessary.

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The world's first dual-source CT scanner, the SOMATOM Definition (2006)

In nuclear medicine, too, CT scanners became increasingly important starting in the early 2000s. The imaging systems used in nuclear medicine, such as SPECT (single-photon emission computed tomography) and PET (positron emission tomography), were combined with a CT scanner to produce a hybrid system that united visualization of metabolic processes with the precision anatomical images of structures yielded by CT. In radiation therapy as well, CT came to be used increasingly as an imaging method in combination with radiation units.

Today’s CT systems from Siemens are the product of years of working in concert with scientists, researchers, and medical professionals all over the world. This cooperation is making state-of-the-art CT technology accessible to more and more people. Nowadays, CT scans not only work with a significantly lower X-ray dose than previously, but also help physicians decide how to treat their patients.