Dear list,
I am writing in response to the recent string on coloured biomodels. I would
also like to remind the group that a medical RP group exists specifically to
discuss these issues at
medicalRP@qmi.asn.au & http://www.qmi.asn.au/anatomics/medicalRPfaq.html
and we welcome any input.
It is quite correct that there is an overabundance of information in medical
imaging that cannot presently be displayed in biomodels. The introduction of
colour promises to increase the number of tissues that can be characterised.
SL can be coloured by 'overcuring' the resin. This has been known for a long
time and I remember Paul Jacobs from 3D telling me that two colours were
possible with little or no modification to SL however the second colour was
only a darker version of the underlying resin. Zeneca have developed
Stereocol and we are looking forward to testing this shortly. The problem
with Stereocol is that the colour is somewhat unstable and can leach out. I
haven't seen any data regarding the accuracy of the colour and it's
permanence etc.
Stratasys have a very nice capability to colour biomodels with strong
contrast but lack a transparent resin that allows tumour within bone for
example to be seen by adding a second colour. I am sure that 3D printing and
Actua will also have colour capability.
I would like to make the following points however:
1. Any colouring process as it stands now in biomodelling is a gross
oversimplification that is essentially based on user interaction to select
'tumour' and 'normal' tissue. As anyone experienced in biomodelling knows
there is no magic line that differentiates the two. One must be very careful
on who is controlling the mouse and that they have suitable qualifications.
Patients and surgeons would not be impressed at removing normal tissue on
account of a shoddy biomodel.
2. Colour is only worth the fuss and extra cost when a structure is
encompassed by a second tissue and both are required for display e.g. the
roots of teeth in the jaw or a tumour encased by bone. These situations are
quite rare and I can only recollect a couple of cases out of the hundreds
that I have been involved in. When these situations do occur it can be very
difficult to segment and accurately edit the image. This scenario is exactly
why SL has a major advantage with transparency.
3. A far easier and cheaper way of colouring biomodels is to simply paint
them! We routinely paint tumour, arterial, venous, and bony structures with
far better accuracy and effect than the colour technology presently
available.
4. The most important surgical question is: How does the surgeon accurately
transfer the biomodel information e.g. tumour resection margin to the
patient? To solve this we developed biomodel stereotaxy.
5. I feel that the most important role of colour is to incorporate the side
and patient data into the biomodel for identification purposes.
Paul D'Urso
MB BS PhD
Anatomics Tel. 61 7 3364 0776
QMI Fax. 61 7 3364 0786
P.O. Box 4012 Em. anatomics@qmi.asn.au
Eight Mile Plains Web http://www.qmi.asn.au/anatomics
Q 4113 Australia
Anatomics : The BioModelling Specialists
For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
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