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W.E. Blevins, DVM, MS

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W.E. Blevins, DVM, MS

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    1. Copyright W.E.Blevins 2008 W.E. Blevins, DVM, MS Measurement Issues

    2. Copyright W.E.Blevins 2008 Calibrate Calibrate Calibrate All units must be calibrated no matter who the vendor is. One cannot assume that a measurement is accurate without checking the calibration by using a known standard.All units must be calibrated no matter who the vendor is. One cannot assume that a measurement is accurate without checking the calibration by using a known standard.

    3. Copyright W.E.Blevins 2008 DrisTech Fovea

    4. Copyright W.E.Blevins 2008 Calibration Test Test device dimension 8.89 cm Second test device 215.65 mm Third test device 211.6 mm Actual measurement 6.1 cm 31% variation Actual measurement 125 mm 42% variation Actual measurement 122 mm 42% variation These are data obtained from a Dristech Fovea. The unit had not been calibrated. This does not imply that all Fovea are this inaccurate. Generally, the installer has the responsibility of doing the calibration.These are data obtained from a Dristech Fovea. The unit had not been calibrated. This does not imply that all Fovea are this inaccurate. Generally, the installer has the responsibility of doing the calibration.

    5. Copyright W.E.Blevins 2008 I don’t remember them ever calibrating this unit. I always thought measurements were off. Calibrate Calibrate Calibrate Vet commented:

    6. Copyright W.E.Blevins 2008 Vetel Diagnostics The image on the left is a calibration device produced by Vetel Diagnostics. This item acts as a calibration test object. The image on the left is a calibration device produced by Vetel Diagnostics. This item acts as a calibration test object.

    7. Copyright W.E.Blevins 2008 Calibration Test Actual dimension 8.89 cm Measurement using e-Film through PACS 6.1 cm Variation 31% Measurement using Metron software with auto calibration Did not use magnification compensation 8.91 cm Variation 0.2% The Metron software looks for the test device and automatically calibrates the measurement. Measurements of the same item were done using non-calibrated e-Film software. Measurement of the device using the Metron software with autocalibration applied. The Metron software looks for the test device and automatically calibrates the measurement. Measurements of the same item were done using non-calibrated e-Film software. Measurement of the device using the Metron software with autocalibration applied.

    8. Copyright W.E.Blevins 2008 Hudson Digital Systems

    9. Copyright W.E.Blevins 2008 Calibration Test Actual dimension 8.89 cm Measurement using e-Film at HDS workstation 8.6 cm Variation 3.3 % Measurement using e-Film through PACS 8.6 cm Variation 3.3 % Using Hudson Digital Systems equipment at the workstation supplied by Hudson, the measurements are much closer. This system had been calibrated, but as you can see it is not totally accurate. Three mm would make a difference to a surgeon making a decision about what screw to use. Using Hudson Digital Systems equipment at the workstation supplied by Hudson, the measurements are much closer. This system had been calibrated, but as you can see it is not totally accurate. Three mm would make a difference to a surgeon making a decision about what screw to use.

    10. Copyright W.E.Blevins 2008 Eklin

    11. Copyright W.E.Blevins 2008 Calibration Test Actual dimension 8.89 cm Measurement using e-Film at Eklin workstation 9.3 cm Variation 4.6 % Measurement using e-Film through PACS 9.3 cm Variation 4.6 % These measurements were taken with the supplied Eklin large animal system. Measurements are overestimated. These measurements were taken with the supplied Eklin large animal system. Measurements are overestimated.

    12. Copyright W.E.Blevins 2008 Zooming the image did not affect the measurement

    13. Copyright W.E.Blevins 2008 Measurement at various positions on the plate were consistent

    14. Copyright W.E.Blevins 2008 Other Measurement Issues Surgeons Measuring a lesion using the same software can tolerate a small degree of inaccuracy. The differences are what is important. However, surgeons make decisions about applying hardware. The exact measurement is important. Measuring a lesion using the same software can tolerate a small degree of inaccuracy. The differences are what is important. However, surgeons make decisions about applying hardware. The exact measurement is important.

    15. Copyright W.E.Blevins 2008 How to measure TPLO angle The TPLO surgery is a common procedure where measurements are done. This can be easily done in e-Film.The TPLO surgery is a common procedure where measurements are done. This can be easily done in e-Film.

    16. Copyright W.E.Blevins 2008 First draw a line from the intercondylar eminence to the center of the tarsocrural joint

    17. Copyright W.E.Blevins 2008 Draw a line perpendicular to the first line near the joint. This is an estimate At this point you just estimate what would be 90 degrees.At this point you just estimate what would be 90 degrees.

    18. Copyright W.E.Blevins 2008 Drag this line until the angle reading is 90 degrees. Grab the end of the line with the cursor. Click the left mouse button and drag the line until the angles read 90 degrees.Grab the end of the line with the cursor. Click the left mouse button and drag the line until the angles read 90 degrees.

    19. Copyright W.E.Blevins 2008 Locate the leading edge of the tibial condyle. Drag a line until it crosses the perpendicular line. Adjust the line so that it crosses the caudal margin of the tibial condyle (black arrow). Read the angle (red arrow).

    20. Copyright W.E.Blevins 2008 Kerf Estimates Surgeons need to decide which saw to use to cut the curved kerf.Surgeons need to decide which saw to use to cut the curved kerf.

    21. Copyright W.E.Blevins 2008 Start by building a circle of known diameter that equals saw diameter. Use line tool to draw a straight vertical line. It should equal saw diameter being considered.

    22. Copyright W.E.Blevins 2008 Draw an equidistant line perpendicular to the first line. A perpendicular set of lines can be made if there are no pixel jumps in the line. That is, the lines should end up being perfectly straight. There should be no stair steps in the line that jump over one pixel.A perpendicular set of lines can be made if there are no pixel jumps in the line. That is, the lines should end up being perfectly straight. There should be no stair steps in the line that jump over one pixel.

    23. Copyright W.E.Blevins 2008 Using the circle tool, click the top right line and drag to the bottom left line. This will create a circle the diameter of choice.

    24. Copyright W.E.Blevins 2008 Click on the edge of the circle an move to the proximal tibia. If the curve is not appropriate, draw another circle to match the saw sizes available.

    25. Copyright W.E.Blevins 2008 Other Surgeon’s Needs Hardware templates Plates Screws We need to push vendors to produce electronic templates of screws, plates and prostheses to that them may be imported into our imaging software for surgical decisions to be made. Vendors do not share this software, so each vendor will need to produce these data.We need to push vendors to produce electronic templates of screws, plates and prostheses to that them may be imported into our imaging software for surgical decisions to be made. Vendors do not share this software, so each vendor will need to produce these data.

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