Calibrating the Ruler

When a measurement is not available, the ruler displays the value expressed as "--" followed by mm (millimeter), in (inches), or cm (centimeters). Use an object of known length as a reference to calibrate the ruler.

If you know the scale factor that takes the acquired image magnification factor into consideration, enter this value to calibrate your ruler.

Note:

  • Manual calibration does not apply to volumetric annotations such as 3D sphere.
  • You can only perform manual calibration on a ruler but the calibration applies to the whole image and all of its annotations.

Steps

  1. Measure an object of known length with a ruler.
  2. Right-click the Ruler annotation and select Calibrate. Synapse displays the Calibrate dialog box.
  3. Do one of the following:

    If you want to ...

    Do this ...

    Change the Known Length Scale Factor.

    • Enter a different value for Scale Factor.

    Enter the Known Length.

    • Enter the length of the ruler in Known Length.
    • Option: Select Propagate to apply the Known Length value to all images in a series.
    • Note: Calibration propagation is not available for some series and therefore, you could see differences between 2D/3D and the other images in a series. In this case, the Propagate option is grayed out.

    Remove the applied calibration and reset the Scale Factor back to the default value.

    • Delete the Scale Factor value.
  4. Click OK.

Results

Synapse displays an asterisk * next to an annotation value to indicate the DICOM-specified default base pixel spacing for the image the annotation is drawn on was adjusted.

Note:

Synapse displays an asterisk when it applies an adjustment to the pixel spacing of the image for improved accuracy. The following scenarios cause Synapse to append an asterisk to a measurement:

  • Manual calibration as discussed above (even for images that originally had no valid pixel spacing defined).
  • Synapse applied Estimated Radiographic Magnification Factoring (ERMF).
  • Synapse applied Distance Source to Detector (SID) or Distance Source to Patient (SOD).
  • For non-Fujifilm images in which both DICOM pixel spacing and DICOM imager spacing exist and are different from each other, and SID, SOD, and ERMF are not available. In this case, the DICOM pixel spacing is considered as the adjustment from the DICOM imager pixel spacing.

Related Topics

Using the Ruler