A Journey through the History of Computed Tomography – Part Two: From Top to Toe with SOMATOM

Bianca Braun |  2015-09-09

CT technology makes it onto the market in 1975. Physicians are excited. The technology is still in its early stages, however, and engineers are frantically working on improvements. In 1977, the first whole-body CT scanner SOMATOM is unveiled. CT takes to the road, and 1987 sees the market launch of the next generation of CT scanner: SOMATOM Plus. Learn more in the second part of our series.


With the first CT scanners in hospitals and medical practices, computed tomography soon becomes the examination method of choice for brain tissue. The contrast-rich images prompt clinicians to call for a related advance: CT images of the whole body free of superimpositions to examine the liver, intestines, joints, and the heart. The engineers face a number of obstacles, however: A larger gantry is needed, together with a shorter scanning time. The recording time of five minutes is to be reduced to 20 seconds. The technology that brings a smile to the lips of engineers and physicians today is the result of intensive development work in the mid-1970’s.

In 1977, they achieve their goal: The first whole-body computed tomograph from Siemens, the SOMATOM, is unveiled to the public for the first time at the Grosshadern campus of the University of Munich Medical Center. The system takes just four seconds to record an eight- or four-millimeter slice in normal mode; in fast scan mode, it takes only two-and-a-half seconds. In one rotation, a computer records more than 92,000 measured values and converts these into an image. The data is then saved on video tape or on a hard disk. The gantry opening now has a diameter of 54 centimeters, allowing the first whole-body examinations to be performed. Various technical modifications mean that the system can now capture kidneys, abdominal arteries, and details of the muscle tissue – without any contrast medium.

Computed tomography develops at an astonishing pace. Following SOMATOM, Siemens introduces an improved version of its head scanner, the SIRETOM 2000. A resolution four times higher than its predecessor, better image quality, as well as faster and more comfortable examinations are just some of the benefits of the new scanner. The larger gantry opening of 29 centimeters offers a clue to what the future will hold for CT: Patient comfort becomes more and more important as new devices are developed.

Over the next few years, Siemens brings other kinds of devices onto the market with continual improvements: SOMATOM 2 was launched in 1979, for example, which had an even better spatial resolution and image quality thanks to the 512 detector elements. Cardio CT scans are now possible for the first time as ECG triggering makes an entry into CT technology. In order to provide physicians with an instant image during the examination, the SOMATOM is equipped with the fastest serially produced data processor in the world. It can handle around 25 million computations per second.

In 1984, Siemens produces a further innovation: An entire CT system is installed in a trailer truck so that it can be transported to hospitals and practices that cannot afford their own CT. The truck weighs 25 tons and is around 15 meters in length. Over 15 of these mobile SOMATOM systems are on the road by spring 1984; this number increases to 30 by the end of the year.

The scope of Siemens’ CT portfolio grows with customer demand. Lower procurement and operating costs, as well as low space requirements without compromising on quality or comfort – these are the demands that Siemens successfully meets with the new SOMATOM DR family. In 1984, the SOMATOM DR 1 is released as an entry-level model for smaller hospitals and radiology departments, and requires less than 40 square meters of space. At the 1984 RSNA, Siemens presents the SOMATOM DRH: The high-end model with 704 detector elements has such a high geometric resolution and such low image artifacts [1] that it outperforms every other comparable device on the market.

By 1987, the performance of CT scanners cannot be improved any further – or at least, not using the technology that was used up to this point. There are none of the now-familiar rotating X-ray tubes or detector systems in these computed tomographs – they can perform a single 360-degree turn. The gantry is halted and then accelerated again in the opposite direction. The first Siemens CT to enable scanning with continual rotation is the SOMATOM Plus. It achieves this in one second, making it the fastest CT in the world. Siemens gains the technological edge over its competitors while laying the groundwork for the next generation of high-performance systems: Spiral CT. Find out more about this new development in the next article in the series.


About the Author

Bianca Braun, M.A., Siemens Healthcare, Communication Manager of Healthcare History, Erlangen, Germany


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[1] Study of the American physicist J. Thomas Payne at the Institute “Midwest Radiation Consultants, Inc.” in St. Paul, Minnesota (1985)