3-D X-Ray is Big News for Archaeological Research

By Brigid Gallagher 13/09/2012

ArtInfo has released an article today which has me very excited, and thinking of ways it could be used in New Zealand archaeology.  

Instead of having to consolidate (or glue together) a fragile pot, urn, vessel, or block of loose soil,  with low concentrate adhesives, co-polymers, acrylics and the like,

And then slowly micro-excavate the contents inside by hand (with really small tools, a delicate hand and meticulous recording) with a 2-D x-ray image or CT-Scan at your side to guide the operation.

This extremely cool piece of kit designed by Nikon to check the condition of turbine blades for Rolls Royce airplane engines is now being used by archaeologists at the University of Southampton to blast not one, but multiple rays  at an object, subject or material from different angles….before it has been excavated. 

Image above: Courtesy of University of Southampton

The reason this is so great? 

A 3-D image is produced giving multitude amounts of new information on one photographic image.  It gives the person about to excavate or  conserve the vessel and its contents maximum information before going in. Information like;

  1. What is in the soil block, urn, pot, basket, gourd, or skin?
  2. How have the contents been arranged?  Have they been dumped randomly, perhaps quickly?  Or have they been methodically placed, with time available for their arrangement?
  3. Is there more than one type of object, subject or material preserved?  Were they put in at the same time, or different times?  Are they in layers that show the order they were placed in the vessel? 
  4. Is the excavation and conservation or restoration strategy being proposed the right one?  Will the contents fit through the mouth of the vessel, or will the side need to come down forst, and then be rebuilt?
  5. Is this a genuine archaeological artefact, or a fake or a hoax?

The archaeologist or conservator can immediately see the true form of the contents,  its survival and condition…and in the case of this story the writing is on the wall…sorry, coins. The words and faces found on the Roman coins tell the date of the object…which gives the terminus post quem, or the date after which the object could have buried, hidden, or lost.


Above: Image of Coins 3-D X-rayed by the Nikon technology. Image courtesy of Southampton.

The use of these kinds of technologies are a great time and money saver, as well as allowing the experts to work out whether a vessel is worth opening…and this decision can take into account;

  • the value or rareity of the contents,
  • the cost for its conservation,
  • the long term use, display or storage of the contents,
  • the research potential the contents have (will they push forward our knowledge of past people and practises) and
  • often most importantly consider the respect and dignity that should be given to the vessel and its contents.  

And super importantly;

Because the multiple rays create an image that non-specialists can actually see and often immediately recognise, the value of the artefact can also sky rocket.  Managers, funders or the public for instance can visualise and understand what they are looking at without heavy explanations and a series of photos that require piecing back together in their head.  Its the same reason I also love 3-D laser scanning. 

It makes the past way more accessible.

The Problem with CT Scans and Conventional X-ray?

Nothing at all….but

CT scans produce a highly informative 2-dimensional visual cross section through archaeological material or objects at high resolution.   

The problem can be that to build up the true and accurate picture of the object or subject, a single slice is not enough.  You need numerous slices to see the story in front of you in its entirety. Much like when we get put through the scan for medical reasons.   This also makes it expensive and sometimes more difficult to manipulate the data during the analysis phase of an archaeological investigation.

X-radiography (my favourite trade tool) also produces a 2- dimensional image which can be very informative, but you need to rely on the experience of the operator to set the right parameters to get the information required. 

Depending on the strength and exposure time of the x-ray information is seen, or not.  This is partially determined by the density or molecular structure of the material being x-rayed.  Too many kv’s, for too long often mean the rays go right through an object missing it altogether showing a very black image.  

It has the same effect of setting the depth of field on a photographic camera. An x-ray image is really a compression of 3-dimensional information into a 2-dimensional format, not a single slice of true data coming from a CT Scan.  The good thing is that with the advent of digital x-ray units, it is alot easier to try out different exposures in one session. Better than going off to the dark room to develop your film, and then find out there is no picture! And probably most importantly it is quite economical.

Why am I so excited about this?

I can’t remember the amount of times I have come away from an x-ray session and wished for just one more image from a slightly different angle, or a slightly different exposure,

And then looked at CT Scans and thought agh, too many cross sections!  My head hurts putting this altogether again. 

Technologies that make an object and their contents visible at high resolution mean maximum information to make more informed decisions and greater appreciation value…and that means there is lowered risk of damage, and heightened appreciation of archaeology in the future.