How to Scan a Mammoth. Recording, analyzing and presenting CT scanned 3D data of a lateglacial Proboscidean from Rotkreuz, Switzerland

Abstract

In 2015, a tusk and several postcranial bones of a woolly mammoth (Mammuthus primigenius) were found during construction work in Risch-Rotkreuz (Canton Zug, Switzerland). Radiocarbon dated to around 17,000 calBP, the capital bull is one of the latest known mammoth finds from the Swiss plateau shortly before the species went extinct regionally. Though fragmented and incomplete, the impressive size of the tusk and the nearly perfect condition of the bone substance demanded a scientific and museum presentation from early on.

In order to make the bone data available to both researchers and the wider public, all finds were subjected to computer tomography scans. The bones could be fitted into a clinical CT scanner (Siemens Somatom Definition AS) at the local hospital with good results. Subsequently, image segmentation was performed on the standardized DICOM image stacks using the open source software '3DSlicer' (https://www.slicer.org/) to export 3D models. The sheer size of the tusk made clinical CT impossible - it was scanned using an industrial CT scanner (YXLON CT Modular) by Qualitech AG, Mägenwil. Even here, four scans were necessary to record the whole specimen. The resulting data is of significantly higher resolution compared to the clinical scans, but lower and changing contrast as well as scanning artefacts resulted in difficulties for image segmentation and the analysis of the tusk's inner structure. Despite this, the CT data enables an assessment of the ivory to be made, revealing banding of varying density. This is commonly interpreted as incremental (annual?) growth of the tusk. Through the online hosting platform 'Sketchfab' all 3D data is, in slightly reduced complexity, made publicly available to view, interact with and download for everyone. QR codes interlink the web presentation with conventional publication and museum exhibition. In addition, the 3D models and printed copies of the mammoth finds are used as educational material at the local Museum für Urgeschichte(n) in Zug.

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How to Scan a Mammoth
Recording, analyzing and presenting CT scanned 3D data
of a lateglacial Proboscidean from Rotkreuz, Switzerland
Jochen Reinhard and Renata Huber, Amt für Denkmalpege und Archäologie, Direktion des Innern, Kanton Zug
In 2015, a tusk and several postcranial bones of a woolly mammoth (Mammuthus primigenius) were found during construction work in Risch-Rotkreuz
(Canton Zug, Switzerland). Radiocarbon dated to around 17,000 calBP, the capital bull is one of the latest known mammoth nds from the Swiss plateau shortly
before the species went extinct regionally. Though fragmented and incomplete, the impressive size of the tusk and the nearly perfect condition of the bone
substance demanded a scientic and museum presentation from early on.
Left: Aerial photograph of the construction pit at
Rotkreuz in which the mammoth remains were
found, with a view of Mount Rigi in the background.
Centre: Find situation at Rotkreuz of a mammoth
bone in gravelly sand, a uvial deposit consisting
of relocated moraine material.
Right: exhibition of the preserved skeletal remains.
They include a distally fragmented left tusk, part
of the right pelvic bone, the proximal section of
the right ulna, two rib fragments and the spinous
proccess of a thoracic vertebra.
Top: Sketchfab screenshot showing the Risch-Rotkreuz „collection“
of the 3D models of the mammoth skeletal remains and the 3D
model in which the preserved parts are marked in red. The QR code
links to the collection.
Bottom: 3D prints of the existing skeletal elements at a scale of 1:10.
References:
R. Huber/J. Reinhard (2016) Das letzte Zuger Mammut? Eine Baugrube als Fenster in die
späte Eiszeit. Tugium 32, 103–110.
D. Drucker/A. Furtwängler/V. Schünemann/R. Huber/J. Reinhard (2018) Durchleuchtet
und analysiert. Ein Update zur Genetik, Isotopie und Radiograe des „letzten Zuger Mammuts“.
Tugium 34, 123–131.
Contact information: jochen.reinhard@zg.ch
Photo credits: J. Reinhard, ADA ZG; R. Eichenberger KMUZ
In order to make the bone data available to both researchers and the
wider public, all nds were subjected to computer tomography
scans. The bones could be tted into a clinical CT scanner (Siemens
Somatom Denition AS) at the local hospital with good results.
Subsequently, image segmentation was performed on the
standardized DICOM image stacks using the open source software
'3DSlicer' (https://www.slicer.org/) to export 3D models.
The sheer size of the tusk made clinical CT impossible – it was scanned
using an industrial CT scanner (YXLON CT Modular) by Qualitech AG,
Mägenwil. Even here, four scans were necessary to record the whole
specimen.
The resulting data is of signicantly higher resolution compared to the clinical scans,
but lower and changing contrast as well as scanning artefacts resulted in diculties
for image segmentation and the analysis of the tusk's inner structure. Despite this,
the CT data enables an assessment of the ivory to be made, revealing banding of varying
density. This is commonly interpreted as incremental (annual?) growth of the tusk.
Through the online hosting platform 'Sketchfab' all 3D data is, in slightly reduced
complexity, made publicly available to view, interact with and download for
everyone. QR codes interlink the web presentation with conventional publication
and museum exhibition. In addition, the 3D models and printed copies of the
mammoth nds are used as educational material at the local Museum für
Urgeschichte(n) in Zug.
Top: CT scan of the mammoth bones at the radiology
department of Zuger Kantonsspital.
Bottom: Industrial CT scan of the mammoth tusk at
the Qualitech AG facility at Mägenwil. The tusk is
hidden inside the white polystyrene packaging,
required for upright positioning in the scanner.
Top: Processing the DICOM data of the pelvic bone
with '3DSlicer'.
Bottom: Marking the growth zones of the tusk in the
longitudinal section (left) and in the cross section
(right). The longitudinal section shows the cone-
shaped structure of the growth zones progressing
from the distal to the proximal end.