Measuring 4-Point CTR
Introduction
Synapse measures the Cardiothoracic Ratio (CTR) on a displayed image, typically a PA chest X-ray. CTR measurements are performed on a horizontal axis between points that you mark.
The unit of measure defaults to millimeters. You can optionally reset an existing annotation to centimeters or inches.
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Note: |
To ensure valid results, your monitor should be calibrated before you measure anything in or on the images that it displays. |
Steps
- Right-click the image to display a context menu.
- Select Annotations > CTR (4-point).
- Click the image to establish an initial line of measurement.
- Add three lines of measurement, one click for each line. After Synapse displays the four lines, additional clicks do not create additional measurement lines.
- Click any measurement line and drag to reposition it, if necessary.
Results
Synapse displays a ratio of the line length measurements, showing both the distance between the lines closest to each other and the distance between the lines furthest from each other.
Additional Options
Click CTR (4-point) 
on the icon menu.