How to Measure Vessels: Straight vs Curved Ruler

OsiriX and Horos Course · Measurements and Tools

In this lesson, I show in detail two essential measurement tools in OsiriX: the straight ruler and the curved ruler (Open Polygon) — widely used in daily practice, especially in vascular assessments in MPR. Where to find the tools In the toolbar, select the straight ruler. Click the small down arrow to see other ruler options. The curved ruler appears as Open Polygon. Straight ruler: linear measurement and reliable diameter Click and drag to make a linear measurement (in cm). For reliable vascular measurements, ideally measure in a plane perpendicular to the vessel (not just the axial plane). In the example (iliac artery aneurysm), the step-by-step is: Adjust the slice in the planes (e.g., the purple plane) so it is transverse to the vessel in the different windows. Confirm the “perfect circle” (a truly perpendicular slice). Use bone windowing to better identify calcium and the lumen. Hide the axes/pointers with the space bar and then measure with the straight ruler. Curved ruler (Open Polygon): length measurement Excellent for measuring length/extent along the course of the vessel. I adjust the MIP to better visualize the iliac artery and the aneurysm, zoom in, and adjust brightness/contrast. To create the curved ruler: Keep clicking and placing points farther apart from each other to accommodate the curvature. Click the last point to finish. Fine-tuning: You can click any point and reposition it to fit the anatomy. Note: if you place points too close together, the software may “ignore” the curve, compromising the measurement. Prefer more widely spaced points, according to the anatomy. How to delete rulers and points Delete a ruler: select the ruler and press Delete. Delete everything on screen: Command + Delete. Remove a point from the curved ruler: If it is the last point, press Delete. To delete a point in the middle: click/hold the desired point and press Delete.