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Thread: Cobb Angle Measurement

  1. #31
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    My 4cents. I added 2 for inflation....

    When having problems in measurements, adding another dimension from somewhere else aids in inspection. It is used and is in relation to the other measurements. I say use both systems. Dr Cobb devised a simple method as some measurement criteria needed to be devised years ago.

    Focal points in optics can present problems in accurate measurement. Problems arise viewing across flat surfaces and 3 dimensional shapes. Objects can appear larger or smaller dependent on focal distance.

    Measurement under a few degrees is and will continue to be difficult unless there can be a physical method of measurement that's accurate and then averaging over a period of time to account for daily movement.

    ALDT does not show the severity of the cobb angle, however it is an easy way to gain another dimension which is useful.

    This will help explain.
    Attached Images Attached Images
    49 yr old male, now 55, the new 45...
    Pre surgery curves C12,T70,L70
    A/P T2-Pelvis 01/29/08, 01/31/08 7" pelvic anchors BMP
    Dr Brett Menmuir St Marys Hospital Reno,Nevada

    Bending and twisting pics after full fusion
    http://www.scoliosis.org/forum/showt...on.&highlight=

    My x-rays
    http://www.scoliosis.org/forum/attac...2&d=1228779214

    http://www.scoliosis.org/forum/attac...3&d=1228779258

  2. #32
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    Accuracy versus repeatability

    In re Cobb angles, the issue is trying to detect a change. It really doesn't matter if the angle measurement is accurate in some absolute sense but it has to be as precise as possible so that when a change is measured, there can be some confidence it changed that amount.

    It's like certain uncalibrated analytical instruments... it may not be accurate (the real concentration is x when the instrument says y) but x and y are always the same difference.

    Cobb angles are always going to have a huge error term in them from just how the person stands for a particular radiograph. Unless you have amazing body control, two readings 5 minutes apart are likely to differ measurably. Recall that the Spinecor folks produced a change of 11* just by posing the patient.

    Here's what I mean by body control...

    body control

    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

  3. #33
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    Quote Originally Posted by concerned dad View Post
    The distance between the film and the subject doesnt matter if you are measuring an angle. It does matter (I think) if you are measuring a distance.
    Yes you are right. There is a move afoot by some horse lameness specialists to standardize the radiographic protocol when imaging hooves in terms of all kinds of parameters. It's very important.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

  4. #34
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    Ed, That is an interesting point you bring up with your sketch. I know you emphasized the difference to get your point across, but don’t you think if both spines were straight they would have different heights. I mean, wouldn’t the effect be less for a curve change on a given spine?

    The Chinese authors note that they obtained a positive correlation between the measurement method and the Cobb method. Particularly for single curves and balanced curves (not exactly sure what they mean by “balanced” but perhaps that goes to the point that SpiderPug identified.

    Regarding the relationship between Cobb and ALDT they say:

    Finally, the ADLT (sic) measurement has positive significant correlation with the Cobb measurement (r = 0.73, P = 0.05), indicating that the ALDT is valuable. At the same time, the change in spine balance and curve types will affect the correlation coefficient which we should pay attention to. In this study, the correlation coefficient for imbalance group is smaller than that of balance group, as well as that of the 2 curves group smaller than the single curve group.

    FixScoliosis does a good job at presenting the information from this paper on his blog. A read some of the other posts there and I am guessing FS often needs to bite his tongue reading posts here - subscribing more to the SOSORT philosophy than the SRS way of thinking.

    Finally, I know Sharon pounds away at the peer review quality of scoliosis papers. It is interesting that the apparent typo in the quote above escaped the review process (ADLT vs ALDT). This paper is in the Journal Spine.

  5. #35
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    thoughts on measurment, and vertical pachydermata

    Sharon is correct. Detecting change is what you are looking for.

    Inspection instruments should be traceable to NIST.
    http://www.nist.gov/index.html

    If they are not traceable, then they Are to be labeled "for reference only" This is the easy way out. If in doubt as to accuracy of a measuring instrument, like measuring spines with an x-ray, then it should be considered as a supplement.

    When the astronomers were viewing the solar eclipse back in 1919 to try to prove Einstein's theory that space is curved, the hundreds that took these measurements were hesitant to release their findings due to the compound inaccuracies of measurement with optics. They had multiple findings that were all different, and debated their methods. Sound familiar? Well its the same thing with measuring spines. Too many parameters.......

    Sharon, love that elephant! Boredom can produce bizarre thought sometimes.LOL Someone must have been bored to think of producing something like that. Teaching children to think when they are bored, is a good thing. I wonder if that elephant had scoliosis, would he be able to balance as well as he is?...

    CD, height is another easy measurement to use. In fact, its the easiest. Anyone at anytime can record height change very easily. In fact its a great way to teach about measurement, and height changes to children with scoliosis. One measurement at 8AM,3PM, and 10PM to explain and prove that the spine settles due to various effects.

    That 150 degree example was no exaggeration. There was an example I saw on The research channel of a young male who had a about a 180 degree u-turn, in about 7 or 8 vert in the thoracic that the Docs corrected. I will look for it for you. This will prove that "positive correlation" ratio cannot always work in every case.

    Measurement of spines doesn't really need to be all that accurate. Like Dave Wolpert says, within 5-10 degrees is sufficient. 40-50 degrees and age are determining factors for surgery. Its the movement that is worrisome, due to the fact that it can happen so fast. If there was a guarantee that every scoliotic would only progress 1/2 degree per year for an 80 degree lifetime, the result would be a total curve of 40 degrees and no-one would have to worry about anything except maybe a little pain. People adapt to pain.

    Scoliosis is serious and then its not. You can look at it both ways. I try not to think of it as being so serious, there are times where I try not to think about it so much as it does have a tendency to wear one down with worry. This is where the "knowledge is power" thing should be used in a kind of a balance, to keep ones sanity. "Knowledge is power" is a good thing for most, but maybe not to a child with a terminal disease.

    Ed
    49 yr old male, now 55, the new 45...
    Pre surgery curves C12,T70,L70
    A/P T2-Pelvis 01/29/08, 01/31/08 7" pelvic anchors BMP
    Dr Brett Menmuir St Marys Hospital Reno,Nevada

    Bending and twisting pics after full fusion
    http://www.scoliosis.org/forum/showt...on.&highlight=

    My x-rays
    http://www.scoliosis.org/forum/attac...2&d=1228779214

    http://www.scoliosis.org/forum/attac...3&d=1228779258

  6. #36
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    I agree, especially about the issue of detecting a change rather than an absolute number.

    But I have run into an issue with the inaccuracies of the Cobb measurement. I disagree with one of my daughters (former) doctors about the measurements of her inbrace Cobb. His response is both; 1. it is not uncommon to have different measurements from different people and 2. he picked different vertebrae than myself. (well, there is 3 too: he has a lot more experience than myself)

    Using this new ALDT method may reduce the error in (1) above and negate the error in (2) above.

    What I don’t understand about the xray process is the effect of the distance between the source of the xrays, the subject, and the film.

    Is it like a flashlight, where the beam broadens as the distance increases, ie, one single point source of xrays?
    Or,
    Is it a uniform source of xrays such that distance measurements are valid?

  7. #37
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    Quote Originally Posted by titaniumed View Post
    Sharon, love that elephant! Boredom can produce bizarre thought sometimes.LOL Someone must have been bored to think of producing something like that. Teaching children to think when they are bored, is a good thing. I wonder if that elephant had scoliosis, would he be able to balance as well as he is?...
    Maybe he could learn to compensate.

    Here's the picture I was looking for when I found the elephant...

    headstand #1

    That guy do learn dressage quickly in my opinion.

    So could this guy...

    headstand #2
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

  8. #38
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    flouroscopy concepts

    CD

    No matter who does the measuring, or how they do it, there is nothing like comparing multiple x-rays to check for movement.That's why I have always said that everyone should get their own dated copies of their x-rays in their possession. There is no reason why they shouldn't give burned copies on disk to each patient. That way the patient can view these next to each other on their home computers.

    Physics class! ... fun fun fun.
    here are a few articles to read
    http://en.wikipedia.org/wiki/Focal_length
    http://en.wikipedia.org/wiki/Focal_p...nts_and_planes
    http://en.wikipedia.org/wiki/Fluoroscopy

    Now, it is possible to do this. Maybe not practical,maybe dangerous, but

    I'm not a radiologist, and I am not aware of current technologies which are changing every MINUTE of the day, but I think that if a person were to stand in front of a fluoroscope, a machine that could "automatically focus" along the spine, have that person bend to the left,shoot the length of the spine,stand straight,shoot,and to the right, and shoot, then have a computer analyze the data, then we might have something worthwhile. To have actual video of the movement of the whole spine through left to right bending would produce fantastic results which could be stopped frame by frame for analysis. This is just 2 dimensional. 3D would be even better.

    The auto focus would be needed for lordosis and kyphotic curves or corkscrew shapes. The focal areas that are shot for this video would have to be loaded into a 3 dimensional x-ray and or cad program.

    I say dangerous to to the amount of REM exposure. ??? I don't know. Surgeons use fluoroscopy to place screws,
    http://journals.lww.com/spinejournal...cement.19.aspx
    Oh boy, I think I will thank my surgeon, one more time.

    Just like shooting a video of a car spring with a 6 inch diameter, if the focal point is 6 inches, and the camera followed the helix up that spring, it would have to stay 6 inches away at all times to stay in focus.

    Of course all x-rays or spinal video should be shot immediately after 8 hours of sleep with a maximum timeframe.

    I'm sure the various companies that make this equipment have thought about this.
    Ed
    49 yr old male, now 55, the new 45...
    Pre surgery curves C12,T70,L70
    A/P T2-Pelvis 01/29/08, 01/31/08 7" pelvic anchors BMP
    Dr Brett Menmuir St Marys Hospital Reno,Nevada

    Bending and twisting pics after full fusion
    http://www.scoliosis.org/forum/showt...on.&highlight=

    My x-rays
    http://www.scoliosis.org/forum/attac...2&d=1228779214

    http://www.scoliosis.org/forum/attac...3&d=1228779258

  9. #39
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    is nothing like comparing multiple x-rays to check for movement
    I agree 100%. The troubling part of my disagreement with the doctor about my daughters xrays was not so much the different reading we obtained, but the similarity between her pre-brace and braced xrays. (our measurements agreed on the pre-brace xrays).
    Except for the brace rivets, they looked identical (even when overlayed using a graphics program - I am thinking about creating a blink animation)

    The Links you posted didnt answer my question about xrays or at least I wasnt able to figure it out.

    The film is recording the "shadow" from the interaction of the xray source and the bones.

    If the source of the xrays comes from a point source, then the shadow SIZE will change as the distance between both the source and bones and film varies.

    If the xrays are coming from a planar source, the rays will be perpendicular to the bones and the film and the shadow SIZE will not change based on positioning.

    This link you provided shows the focusing of rays by a lens. (the top image is how I imagine we would want the xrays to behave - ray paths perpendicular to the subject)

    But I didnt read anything about a lens in the xray link.

    I'm not sure if I'm explaining my question right. It is sort of analogous to casting a shadow on a wall using a single light bulb vs a 8 ft fluorescent tube bulb.

  10. #40
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    So I used the software my x-ray CD had and I drew lines where the curve started/stopped, then I used another tool and made an angle so each side touched the outer part of the spine. I'm not sure if I did it right but I got measurments close to what the report said so I think I may have done it right.
    Here is a photo of my bottom curve 22 degrees, did I do it right? Do any of you think it's worth a Spinecor? I also have a top curve of 11 degrees, and my skeleton is tilted.
    Attached Images Attached Images

  11. #41
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    Sarah, I applaud you for taking an interest in the xrays and trying to figure things out yourself. You really need to be cautious taking anyone’s advice. You need to listen to your doctors and your parents.
    Having said that, I have a comment and a question.
    The quality of the xray seemed pretty poor. I had a tough time seeing the lines of the vertebrae. Where your xrays taken on two films or did they do a full spine xray?
    Contrast the quality of your xray with the attached which seems (at least to me) easier to read. I think I would have a hard time convincing myself I measured things correctly on an xray like the one you posted.
    Also, I saw you say on another post that you are in 10th grade and have a 22 and 11 degree curve. I presume those measurements are out of brace. Can you share your prebrace curve history?

    Note: the attached xray was extracted from a full spine xray.
    Attached Images Attached Images

  12. #42
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    What the heck, I might as well throw this one up there too.
    Anyone see a way that this could be measured as 26 degrees?

    Attached Images Attached Images

  13. #43
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    Quote Originally Posted by concerned dad View Post
    What the heck, I might as well throw this one up there too.
    Anyone see a way that this could be measured as 26 degrees?

    No. I am looking at my daughter's 27* radiograph and it is noticeably different. If that is 26* then my daughter's is not 27*... one or the other.

    That's outrageous in my opinion. You were paying for expertise that you clearly weren't getting.
    Sharon, mother of identical twin girls with scoliosis

    No island of sanity.

    Question: What do you call alternative medicine that works?
    Answer: Medicine


    "We are all African."

  14. #44
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    I know, I wanted to know if I did it right. I used the software that came on the CD Apicas or something like that. The original x-ray was full, the quality was not so good then I took a pic of my computer screen since I could not save the image to my laptop using the software
    I was never in a brace but was given the option when I was 12 and my parents and I said no. I progressed after that quite a bit.
    My last doctor was not what I would call a fantastic doctor. I have asked my parents about Spinecor, my Dad likes the idea of chiropractics, but my Mom doesn't. I sent my Mom a Email about Spinecor and told her about it and she was just sort of like "Mhhhhh Hmmmmmmm" IDK what to do (Sigh)

    The picture you attached looked a lot bigger than 26 degrees.

  15. #45
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    Hi...

    I have a book published by Medtronic, that is the official guide to measuring curves, for the Spinal Deformity Study Group (a large, multicenter study database). There are all sorts of modifiers, many of which require measuring the lateral films as well, so I'm not sure that any of us can accurately measure Cobb angles without first being trained to do so.

    Regards,
    Linda

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