Measuring Elliptical Areas

You can create an elliptical measurement to define and measure a region of interest on an image. The area, mean, standard deviation, median, and maximum values appear in the bottom left corner of the viewport:

• Area: represents the calculated area value in square centimeters.
• Mean: represents the calculated values of Hounsfield units for the area.
• SD (Standard Deviation): represents the variation from the average mean.
• Median: represents the middle value of all the pixel values (sorted from lowest to highest) for the area, or an average of the middle pair of numbers if there is an even number of pixel values, in Hounsfield units.
• Max: represents the maximum pixel intensity value in the area, in Hounsfield units.

Once you have created the measurement, you can rotate, move, and resize it as required.

To measure an elliptical area:

1. Click the Elliptical/Circular ROI measurement tool .

2. To measure an elliptical area, click at the starting point of your measurement and drag to adjust the size and shape of the ellipse.

   To measure a circular area, press the SHIFT key after starting your measurement and release it after completing your measurement.

To modify an elliptical area:

1. Click an ellipse to select it.

2. Do one of the following:

   To:	Do this:
   Resize an elliptical area	Move the mouse cursor to one of the four end points, and then click and hold the left-mouse button while moving the end point. To resize a circular area, click and hold down the SHIFT key while moving the end point.
   Move an active measurement	Move the mouse cursor over the ellipse contour or the crosshair, and then click and drag the ellipse to the new location.
   Rotate an active measurement	Move the mouse cursor over the rotation points at the top, bottom, left, or right sides of the ellipse, and then click and drag the left-mouse button and rotate the ellipse.

   The area, mean, standard deviation, median, and maximum values of the elliptical area are adjusted accordingly.