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Laser foot scanner or plaster cast?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by footdoctor, Apr 19, 2005.

  1. footdoctor

    footdoctor Active Member


    Members do not see these Ads. Sign Up.
    Do any of you have experience with the use of the 3-d laser foot scanner from sharpe shapes?

    I feel that a well taken plaster cast is hard to beat in terms of accuracy but it is messy,time-consuming and as i use a production lab in Canada it costs me money to post the casts.

    It is the only option available to me as my orthotic lab uses the AOMS system.

    I have heard that there are limitations with the scanner and problem obtaining

    correct forfoot to rearfoot alignment when dealing with large degrees of forefoot invertus.

    Any clinical papers out there?

    Any help would be greatful

    thanks

    scott shand-podiatrist-Aberdeen-Scotland
     
  2. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    A topic dear to my heart!!!

    I have just submitted a paper for publication based on a cost benefit analysis of the two methods .... but will have to reply later as on holiday in Magnetic Island, then off to a conference....

    Irene Mclay has a paper in JAPMA a few years ago comparing shape from scans and casts.

    BTW - they are 'optical' scanners, not laser.
     
  3. davidh

    davidh Podiatry Arena Veteran

    Hi.
    No experience of these, but a colleague gave me this site to look at
    www.digi-cast.co.uk
    Be interested in comments.
    Cheers,
    david
     
  4. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    I am back in town.....here is my take...

    1. Beware the marketing hype - the way some speak and try to baffle with BS makes them sound like they are trying to scam you. I called these people 'markatroids' (the type of people best to be avoided :)) -- I no like some of the sales pitches I have been given.

    2. There are bascially two types of optical scanners - red light and white light -- the red light is much quicker (slower scans means the foot can move during scan, decreasing accuracy)

    3. There is NO evidence that patients get better outcomes when scans are used (....but you can BS patients with the "computer" technology :p)

    4. We have done a "time in motion" and "cost benefit" study of optical scaning vs plaster cast (just submitted for publication) - the time and cost savings are massive with scanners - mostly due to the time involved in casting and cleanig up mess (except the capital costs for the scanner can be high - 'top of the line' is ~$15 000USD).

    5. Ignore the marketing hype (ie BS) about there accuracy --- yes they can capture and reproduce a shape (ie a foot) down to 1/10000th of an inch --- but what use is that if you are holding the foot in the wrong position? - why would anyone want an accurate reproduction of the wrong position (BTW, we still do not know what the right position is :D)

    6. Scanners can be closed or open source. Closed means you are tied to use the one lab its linked to. Open means you can use any lab that has the compatible hardware.

    7. Different labs will use different models to market scanners: eg
    a) Give free scanner to best customers
    b) Lease or sell scanners to customers
    c) Subsidise scanners, based on volume
    d) Give scanner and charge more for orthoses
    e) etc

    8. There are some technical issues and a number of assumptions that go into the algorithms associated with scanning that I am still somewhat uncomfortable with - though I know they are being worked on.

    9. It is the future.
     
    Last edited by a moderator: Apr 26, 2005
  5. footdoctor

    footdoctor Active Member

    laser foot scanner.....laser cast scanner

    cheers craig,

    Its a great idea the optical scanner and i've no doubt that the shape is spot on but surely getting the forefoot to rearfoot and stj neutral position is going to be less accurate than a good neutral suspension cast and good biomech exam.

    I have decided to chicken out,i am to purchase a laser cast scanner from sharp shape which is linked to an aoms system in Canada.

    I think this is about as stable a platform as i am going to get.........for the time being.

    Thanks for your comment.


    scott
     
  6. jarlett

    jarlett Member

    milling positive casts

    Does anyone have any experience with using a scan to mill a positive cast, then manufacturing via heat moulding etc (as opposed to milling the orthoses direct). References to companies that produce milling machinery would be appreciated. :)

    The main benefit I see in this, is you get the time saving in casting as per Craig's email above, but are not wasting material in milling a 4mm orthotic device from a 100mm block of polypropylene.

    Jayne
     
  7. Craig,
    I agree with the most of your assessment of the situation with regard to 3D scanning, but I wish to clarify a couple of assumptions.

    Quote from Craig:
    "There are some technical issues and a number of assumptions that go into the algorithms associated with scanning that I am still somewhat uncomfortable with - though I know they are being worked on."
    My interpretation of true 3D scanning at the moment is that there should be very little to no assumptions being made at a software/algorithm level. Essentially 3D scanning is the same as you taking a digital photograph (2D of a person's plantar foot surface), but it allows you gain the depth as well. For our application it would be therfore the height of the arch and other associated depth measurements. The only extrapolation (algorithm) for 3D scanning would be in the use of 2d pressure mat which have previously been discussed at great length on this forum...which as I think most would agree would not be classed as true 3D scanners.

    Quote from Craig:
    Ignore the marketing hype (ie BS) about there accuracy --- yes they can capture and reproduce a shape (ie a foot) down to 1/10000th of an inch --- but what use is that if you are holding the foot in the wrong position? - why would anyone want an accurate reproduction of the wrong position (BTW, we still do not know what the right position is )

    This may be true to an extent but you can argue that a plaster cast has potential disadvantages of creases resultant form poor application of plaster deformation in transit to the lab and a number of other issues, aside from the fact that you can use your point of holding the foot in the wrong position as a disadvantage of casting/scanning in general and not specifically scanning.

    Scott worte: "...i've no doubt that the shape is spot on but surely getting the forefoot to rearfoot and stj neutral position is going to be less accurate than a good neutral suspension cast and good biomech exam"
    Scott, good luck with your purchase and I hope you will get back to us and let us know how your purchases has benefited your practice. To my way of thinking though the scanner should in theory take the same contour of the foot as what you would have taken with the plaster - neutral suspension or otherwise. But, the advantage as Craig pointed out is that "the time and cost savings are massive with scanners - mostly due to the time involved in casting and cleaning up mess." Not to mention the time saving in transit to your lab as I presume you will email or upload to the server at the lab???

    Interesting discussion and Craig I look forward to your paper under submission.

    Regards
    Phil
     
  8. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    Variability of casting is bad (ref) ---- what my point really is - "Do not be sucked in my the 'markatroid' approach about the accuracy of scanning" - who cares how accurate it is, if the foot is held in the wrong position.
     
  9. paulm

    paulm Member

    i have been using an optical laser scanner here in the UK since 1998, the Bergmann optical laser scanner, it does somewhat tie me into Bergmannlabs in the USA but what the hell i get a really good device, it takes approx 7 seconds to scan the foot, the software has a really useful menu, ie you can manipulate the scan, rotate etc and get a forefoot to rearfoot reading, whatever the angle, measure the foot size etc, I can also (with additional software)scan patients cast, mind you if its a rubbish cast then its a rubbish scan, but then i suppose that makes it accurate

    regards
    Paul
     
  10. davidh

    davidh Podiatry Arena Veteran

    Hi Paul,
    Didn't realise you used a scanner for your casts (but should have known really!) :eek: .

    Do you want to bring it to the Biomech Workshop in June, or is it too big?
    Cheers,
    davidh
     
  11. paulm

    paulm Member

    milling of a positive....with the Bergmann scanner i send the data via the internet, the data has scan of feet and prescription info, the lab receives this, then Dr Bergmann uses his Dr construct software to make all the alterations accommodations postings etc to the scan on the computer, the image is then sent to the milling machine. The milling is done using wax so this means that the shavings and eventually the positive are then re-heated and used again, no need to keep the positive as all data is kept on computer, the data being the negative and the positive, quite a positive process to see, ooops forgive the pun...
     
  12. ft-biz

    ft-biz Member

    Scanner

    Dear All,

    Langer USA is about a 3-D optical hand scanner for the office. Apparently
    they have been working on it for several years and have finally have all
    the glitches out of it. Once scan is made image sent by modem to lab
    and a positive is created. (Similar to Bergman, but more advanced).
    Orthotics will be milled from the positive.The product is to be released
    this summer and I think , will cost about $3500.00 USD. I will keep you
    informed or perhaps contact Langer yourselves.

    Robert
     
  13. paulm

    paulm Member

    Hi Robert
    was this the one that was displayed recently in New York where they were scanning a modle of a foot, im curious as to how we can hold the patients foot with one hand and hold a scanner with the other and keep scanner steady ?, because the scanner is hand held does this not limit the size of it so it may only be able to measure certain points on the foot like height of arch length of arch 1st to heel and 5th to heel, im certainly no expert here but im just trying to think how i could work.....

    regards
    Paul : :confused:
     
  14. ft-biz

    ft-biz Member

    Scanner by Langer

    Dear Paul,

    I have not actually seen it yet. The langer people were in toronto visiting
    their langer customers, of which I am one. In a few weeks they are coming
    back for a weekend lecture series and are bringing the scanner for their
    Canadian customers to view , try and possibly order. I will know better then
    and will keep you informed.


    Fraternally,

    Robert
     
  15. joejared

    joejared Active Member

    Amen.
    If by red light, you mean coherent light, there are a few color options for laser scanners. The most cost effective light is red, but red is actually counterproductive to accuracy. Blue or green lasers are more accurate and react to the exposure to skin better. Some scanners, however, have a weakness in seeing these colors so just changing out the laser module itself would likely destroy the product.

    As for 'white' or incoherent light scanners, accuracy can suffer slightly but it is quite possible to perform a scan on a patient's foot in a couple seconds projecting a structured light source whereas the patient's foot can move between scanlines in a laser scan. On a scanner I worked with almost a decade ago, an array of dots with an origin X was projected onto a foot, and stereovision was used to obtain 3D results. The reality of that design is that only one camera was necessary to obtain 3D data, since planes could be derived from the projector itself. I would expect faster scans using a structured light source than that of lasers but prefer laser projection for accuracy. This days technology lends itself to faster scans using lasers so the differences in performance are decreasing almost daily.

    I've seen videos online like that. When I was at a customer site recently, he showed me one video and I'm not sure if t was the bs factor or the outright lie to the patient that made me walk away from the video in discust. A scanner is just a tool, which, at best, replaces a bit of plaster and changes the shipping method to a laboratory. A well trained individual still has to deal with the working data, whether it is an actual cast or a patient's foot.


    I've seen units that cost more than $20K. With any scanner, probably the more critical element is isolation or how one handles variances in ambient lighting. That $20K unit didn't fair well. Even the lessor expensive scanners have click charges, and from what I've seen of these charges, it looks more like they want your previous shipping expenses. I can't justify charging a customer for an automated process of routing data that rarely involves any human labor to send cast from point A to point B, not withstanding that I do charge a modest royalty for actual produced orthotics. Those click charges can be quite unbearable and should be considered prior to a purchase. One such vendor charges $3800.00 for their scanner + $5.00/pair if purchased, $12.00/pair if leased.

    [quote[
    5. Ignore the marketing hype (ie BS) about there accuracy --- yes they can capture and reproduce a shape (ie a foot) down to 1/10000th of an inch --- but what use is that if you are holding the foot in the wrong position? - why would anyone want an accurate reproduction of the wrong position (BTW, we still do not know what the right position is :D)
    [/quote]

    Agreed, as it's physically impossible to acheive that level of accuracy. +-0.25mm would be a reasonable expectation with respect to altitude, however, and assumed would be no more than 1MM in accumulative error. One concern I have about some of the scanners is their height, the number of cameras used, and how much disparity exists with respect to measuring the profile of the foot. The world looks completely different at 12" away from the foot than it does at 4" from the foot.

    Open source is something that typically refers to source code. I believe a more correct terminology would be open and closed systems.
    Front end, tail end, or both is how I look at it, but you're spot on with respect to the many models.

    The term algorithm is really overused in this industry. Either there are mathematical equations that can be treated as an axiom or there aren't. Because of the overuse in this industry, I replace the term in discussions with proven mathematical equations for this very reason. The solution of an intersection of a line and a plane would be one such equation and widely accepted and used in this and other industries. While there probably would be algorithms supporting the equation, an equation would imply some level of accuracy and lend credibility to the sale of a product, at least to engineers being consulted prior to a purchase.

    As to scanning casts or feet, I think I would prefer to scan a cast, for reasons others have stated. It is technically easier to capture the calcaneous using a single camera from a plaster mold of a foot due to its concave structure, but it is still possible to capture some of the calcaneous directly in a foot scan. I'm inclined to think that a slightly proximal view angle would be of benefit to improve a scan. If your scanner cannot capture the back of the heel without losing the arch, my first question would be the base equation they are using to scan, and whether or not it is a sound equation. Especially with coherent light systems, the amount of intensity reduction from heel to arch, even at 45 degrees relative to the plantar surface of the foot, should be negligable. Also, and if a scanner is using a black and white camera, it might be a good time to point out to the vendor that this is in fact the 21st century, and that we have color now. ;-) The distinct disadvantage to bw cameras is their weakness in capturing objects that are blue. Biofoam casts are commonly blue, and this presents difficulties that are often compensated for using spray paint or baby powder. The methods used for compensating for this weakness are often comical.
     
  16. Jeremy Long

    Jeremy Long Active Member

    Just a personal bias, I HATE the hand-held scanning devices. Being able to secure the extremity in two hands better allows me to set the intended scanned surface to be precisely where I want it.
     
  17. paulm

    paulm Member

    I still have yet to see one of these hand held scanners :eek:
     
  18. joejared

    joejared Active Member

    Polhemus has one at http://www.polhemus.com but it is very expensive. It's basically a combination of their fasttrak system and a simple 3D LPi based optical scanner. Basically, it uses a cartesian like coordinate system, X,Y,X,Pitch,Yaw,Roll and then a camera and laser bar that relates to this position. It's a nice marriage between the 2 technologies, but the fasttrak still has inherent vulnerablity to ferrous objects throwing off the position. While it is freely mobile and offers little resistance because it is a combination electromagnetic and optical system, it also ranges in price from $20k to $30K, which I doubt will go into a doctors office often. This reminds me. There are about 8 Fasttrak units about to be obsoleted from my customer base. That's about $56K in hardware. It will cost me $3000 to do it in total counting parts and labor, for all 8 labs. :D No more paying $1000.00 to have a single 5 volt regulator or diode replaced, and no more $700.00 stylus every time it wears down. The lesson? If you're going to gouge a customer, NEVER expect them to stay a customer. I don't plan to buy any more products from Polhemus.
     
    Last edited: Dec 13, 2008
  19. Cavus

    Cavus Member

    Just to say I've been using a Sharpe Shape laser scanner for 8 years since they were introduced to the UK. I have always had great results, but I put this down to more an understanding of what is required and a great relationship with my Lab.

    I get frustrated with the walk over the mat physicians who then send off to the lab for them to totally evaluate when they don't understand the principles themselves....but that's another story
     
  20. drgct

    drgct Member

    I have been using a 3D laser scanner from Peditechnology for the past 1.5 years. It is a true 3D scanner, the foot does not touch it during the scan and therefore the foot can be held in its' appropriate position for the scan without any pressure influence from the scanner.

    It's accuracy seems remarkable and I believe the results are better than our traditional methods of casting.

    It is also clean, scan gets transported over high speed internet......I'm addicted!! No way back to the plaster/slipper sock for me....only digital imaging from here on out.

    George Trachtenberg DPM
     
  21. Never used one. But the thing I like about foam casting is that you can get around 75% of the soft tissue deviation which occurs on WB by applying 25% of the patients body weight to the foot (through the knee).

    Accuracy to within 1/100000000000000000000ths of a mm is great... but how useful is that if the lab then has to slap a load of extra on around the heel to simulate WB, on the FF to balance the cast and arch fill to requirement? How much of the original shape makes it onto the actual insole? Holding the foot in the desired position is well and good, but it is well to remember that you are generally trying to alter forces in the musculoskeletal system and before this is manipulated by ORF there is that troublesome layer of fatty soft tissue to consider. I think the configuration of this soft overlying tissue is often neglected when considering foot capturing modalities!

    I'm not saying that scanners don't / can't work, just that we should not be dazzled by the tech!

    But that might just be sour grapes because i have a budget of £8.34p per year so i can't even look at pictures of scanners! You decide.

    Regards
    Robert
     
  22. drgct

    drgct Member

    Robert,

    Can only relay my experience to you. I was not "dazzled" by the technology, but I am by the outcome. I also cannot speak about other scanners out their but only the one I use.

    Regards,

    George
     
  23. Thats fair! There are several ways of capturing the foot and little to choose between them. Its just my opinion! The same critique could be leveled at POP casting and that remains the "gold standard".

    Regards
    Robert
     
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