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09/13/12 11:05
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#188318 - I would not use volumetric imaging
Responding to: Richard Erlacher's previous message
Let's take a step back from defining a specific type of imaging technology and look at the problem a little more closely to see which imaging technology might be best suited to fit this problem.

The idea is that you want to know the complex 3D surface of an appendage that is organic so that this can be mapped. Once this is a known surface, a force per unit area is applied so that the appendage deflects. The deflection needs to be a measured so that different areas of the appendage can be assessed for generation of a prosthesis.

This problem can be done through a volumetric examination, but I believe that would be overkill. Volumetric examinations would include ultrasound, CT, or MRI, for example. Ultrasound would be the most practical to get the 3D surface trhough an immersion technique. Surface imaging would be a lot cleaner solution. Surface imaging techniques would involve a 3D laser scanner or machine vision.

Probes could be made with a spring that followed a K constant and the probe could also have a linear potentiometer to measure resistance to know the deflection, but the probe may not have to include the resistance if the surface scanner can also see the deflection in the probes.

Once the data is collected, the biggest problem is what to do with the data. The most complex way of handling the data that will give the most desireable results will involve reversing a Finite Element Analysis. With FEA most people want to see what the deflection is based on material properties and force applied. In this case, you know the deflection and force properties, but lack the material propeties. Pseudo material properties may be able to be solved that allow a perfect fit.

A less complex method would be to take multiple data points involving different pressures and then plotting the deflection in a 3D with a color map.

How a prosthesis is born utilizing this information is ouside my realm.

Just my two cents.

List of 49 messages in thread
TopicAuthorDate
How would you do this?      Richard Erlacher      09/10/12 10:30      
   I have no idea if this would work, but ....      Erik Malund      09/10/12 10:32      
      How would one actuate them?      Richard Erlacher      09/10/12 12:29      
   strain guage      Mahmood Elnasser      09/10/12 11:03      
      Yes, you might be onto something.      Richard Erlacher      09/10/12 12:49      
         Computer-controlled?      Per Westermark      09/10/12 16:37      
            computer controlled      Richard Erlacher      09/10/12 19:52      
               Calibration + redundant force-limitation      Per Westermark      09/11/12 00:03      
               Interesting problem      Jim Granville      09/13/12 15:06      
                  Yes, it seemed coarse, at first.      Richard Erlacher      09/13/12 17:08      
                     Precision is cheap ?      Jim Granville      09/14/12 15:15      
                        I don't follow ...       Richard Erlacher      09/15/12 09:59      
                           Precision      Jim Granville      09/15/12 19:09      
                              other considerations      Richard Erlacher      09/15/12 20:15      
         Tomographic imaging?      Christoph Franck      09/11/12 04:47      
            There's one major problem ... maybe two ...      Richard Erlacher      09/11/12 09:20      
               $100 MRI unit      Erik Malund      09/11/12 09:31      
                  I'm not sure ...       Richard Erlacher      09/12/12 09:57      
         Voice coil and LVDT?      Oliver Sedlacek      09/12/12 02:37      
            Not having a lot of experience with this sort of stuff ...      Richard Erlacher      09/12/12 10:07      
               Danger/problems with hydraulic since no spring effect      Per Westermark      09/12/12 13:55      
                  A few things puzzle me with this approach      Richard Erlacher      09/13/12 02:07      
   Ultra Sound Probing      Michael Karas      09/10/12 16:36      
      Ultra-sound is better for measuring surface or sub-surface      Per Westermark      09/10/12 16:39      
   I would not use volumetric imaging      Justin Fontes      09/13/12 11:05      
      I'm not sure what you mean      Richard Erlacher      09/13/12 16:59      
         another thought      Rick Gebhardt      09/17/12 13:43      
            I consider that one of the more "pregnant" approaches      Richard Erlacher      09/17/12 15:25      
               Lots of options available      Per Westermark      09/17/12 16:14      
                  You've got to consider cost      Richard Erlacher      09/18/12 16:50      
                     Cost/safety      Per Westermark      09/18/12 18:29      
                     Cost target?      Oliver Sedlacek      09/21/12 08:37      
                        The price target comes from a few prosthetists      Richard Erlacher      09/21/12 21:46      
   comercial CMM      Mahmood Elnasser      09/17/12 13:58      
      This only received cursory examination       Richard Erlacher      09/17/12 15:28      
         pneumatic actuator      Rick Gebhardt      09/17/12 20:14      
            Yes ... but what would this cost?      Richard Erlacher      09/17/12 23:30      
               100 rods?      Per Westermark      09/18/12 02:04      
                  Patient size ...      Christoph Franck      09/18/12 06:12      
                     That's what I'm considering      Richard Erlacher      09/18/12 07:50      
                     AAACK! ... another double post ...       Richard Erlacher      09/18/12 07:50      
                  it's not as big as you think!      Richard Erlacher      09/18/12 07:40      
                     90% coverage      Maarten Brock      09/19/12 03:47      
                        So maybe vacuum pump for the too fat people      Per Westermark      09/19/12 06:38      
   I do not know if this is relevant, but      Erik Malund      09/19/12 07:52      
      I'll have to look into this.      Richard Erlacher      09/19/12 09:13      
         Single air pressure sensor sensor for tip force guestimate      Per Westermark      09/19/12 11:27      
   What about infrared?      Marshall Brown      09/21/12 03:03      
      How would you do this so it would retail for under $5k      Richard Erlacher      09/21/12 08:21      

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