Computed tomography (CT) for scientific research and the digital preservation of values The researchers of the Eötvös Loránd University and the Hungarian Natural History Museum work with ZEISS Hungary together to preserve the values of the past and the present using digital technologies.

Birch mice in the CT system

Mr. Csaba Kiss, a PhD student of the Eötvös Loránd University, and Dr. Tamás Cserkész, a researcher of the Hungarian Natural History Museum and the project supervisor, said: “The birch mice we are studying are small, mouse-like rodents. Their earliest ancestors lived probably in the Himalayan Plateau some 17 million years ago, then they spread to the steppes of North America and Eurasia. During the long millions of years, however, their morphology, like the shape of their skull, remained unchanged, meaning we can regard them as a living fossil.” Their shape seems not to have changed. The researchers, however, found quite significant differences in their genetic material, i.e. DNA sequence. The reconstructed skull, created with the CT ZEISS METROTOM, is of great assistance in the understanding of this apparent morphological fixedness. The researchers received considerable technical support not only from their own institute, the Hungarian Natural History Museum, but also from the National Museum of Natural History at the National Academy of Sciences of Ukraine, and the Smithsonian Institute of Washington, which made their collections available to them.
Moreover, they sent the carefully packed samples to the researchers in Budapest. The collection in Washington has real rarities, i.e. species the specimen of which no other museum has. Such is the Kashmir Burch Mouse, which was described (and a few specimens of which were also collected) 100 years ago. However, nobody has met them ever since.

ZEISS has always strongly supported novel solutions and the manufacturer was therefore glad to be part in an unusual research project." 

But why are these small birch mice important for the Hungarian researchers?
There is a birch mouse species in Hungary, the Hungarian birch mouse (Sicista trizona), which is one of the most significant, precious gems of the Hungarian fauna and nature protection activities. The Hungarian researchers studied this species first, then they collected comparative materials from the Ukraine, Russia, Kazakhstan for studies on the relevant taxonomy and evolution biology; eventually, they got to the farthest point of the continent, Vladivostok, and even farther, Sakhalin Island.
In addition to clarifying the situation in terms of taxonomy and evolution biology, the data generated with computed tomography can also be used for other purposes, as the CT can generate very precise images not only of the external surfaces of the skulls, but also of their inside. “The form and shape of the brain skull allows us to determine the degree of development of each area of the brain, the total brain size and volume, which, in the case of humans, tripled in 3.5 million years. On the outer surface, the insertions of muscles and their size reveal us information about the different diets of the mice. The teeth are, however, similarly informative. The CT images, therefore, provide an almost inexhaustible source of data, and we are sure that the studying of birch mice was only the first step, and with the ZEISS METROTOM we will also analyse other animal groups in the future.”

After the consultation between the researchers and the ZEISS professionals last autumn, the measurements were started under the leadership of Mr. Levente Huszár, a senior application engineer, in January 2019. Within the context of the measurements, the researchers generated high-precision skull reconstruction images from the samples by X-ray scanning them with the ZEISS METROTOM CT system. The procedure was intended to digitalise the biological sample with a CT and to generate an extremely precise 3D virtual model of it. The measurement ranges and imaging methods of the CT are, in terms of speed and accuracy, beyond all comparison with conventional measurement techniques. “Given that our samples are very tiny and incredibly vulnerable, these CT analyses ensured us the opportunity to study even the tiniest parts of the skulls in an accurate and safe way. Moreover, we could also investigate the internal, hidden structure of the samples in a non-destructive and non-damaging way.

Outlook: Digital samples and museum collections
Most collections of the natural history museums all over the world are available to researchers only. The rare specimens they keep can often be studied in person and with a permit or borrowed in special cases only. But what is to be done if onsite studying is not possible or the sample cannot be sent by post? Digital borrowing, available today in some institutes, is a good solution to such issues. The participating museums will be able to use the data of the now-prepared digital samples in the future. Though the Hungarian “digital database” is still an experimental concept among professionals only. If it became reality, Hungary could also join this international initiative. Original, precious samples would not need to be exposed to the risks of transport, and the potential impairment caused by moving would also be avoided. Digital data would not only simplify the job of researchers but could also be used in education and popular science. Moreover, today’s technologies also allow us to recreate these samples, in multiple magnification of the original size, with a 3D laser printer. The latest technological achievements have, therefore, a role to play in the museums that keep and exhibit the values of the past and the present.

We are sure that the studying of birch mice was only the first step, and with the ZEISS METROTOM we will also analyse other animal groups in the future.”

Gravera and his team measure the core components of the gearbox during production: at the end of this process, 100% of the gearbox is measured at the test bench. Supplier components are likewise submitted for an acceptance check in the measuring room first. Because when the 48 round teeth slide through the tooth carrier, the highest precision, in the range of a thousandth millimeter, is required. And not only there: to ensure that everything interlocks perfectly, all gearbox components must be manufactured with high precision. To meet these precision requirements, Gravera's team uses ZEISS PRISMO ultra and a SURFCOM NEX for measurements. The coordinate measuring device has a length measurement error of only 0.5 + L/500 micrometers. However, to deliver such precise measured values, the measuring device places high demands on the environmental conditions. Fluctuating temperatures cause materials to expand or contract. The more precise a measuring instrument is, the more temperature fluctuations need to be taken into account. The measurement reference temperature for a ZEISS PRISMO ultra must be kept within a range of 20 - 22 °C, while errors per hour or meter are only permissible within the range of 0.5 K

Gravera therefore knew from the very outset that the new measuring room would have to be equipped with a temperature monitoring system. With TEMPAR from ZEISS, Gravera found a system that could do much more than just measuring the temperature. "It was very important for me to have a system that measures the temperature 24/7, monitors it and, above all, records it in a traceable manner." Nine sensors are evenly distributed around the coordinate measuring machine and record even the smallest temperature fluctuations. Gravera can always visualize all the values on one console, including the measuring room class according to German standards VDI/VDE 2627. "Our goal is to ensure that the measuring room always meets the requirements for quality class 2", explains Gravera. "Even on my first metrology seminar, the lecturer already told us that temperature has the greatest influence on the measurement result. That's why it's very important for me at a personal level that we absolutely master this parameter."