Centerline (3D Curved MPR)

OsiriX and Horos Course · MPR and Centerline

In this lesson I give an introduction to the Centerline in OsiriX, using 3D Curved MPR to measure the length/extent of the iliac artery in a case of iliac aneurysm. The goal is to show the basics: how to draw a manual centerline (more precise than the automatic one), how to check that it is really in the center of the vessel, and how to use the Stretched and Straightened modes to measure distance. 1) Opening 3D Curved MPR I select the arterial dataset (more images and denser contrast) I open it via: gear icon → 3D Curved MPR 3D Curved MPR uses: 3 windows from 3D MPR (axial, coronal, sagittal) and a 4th window (Curved) where the path appears I adjust the windowing for vascular using Bone Tip from the video: it is better to understand 3D MPR well before 3D Curved, so you don't get confused with the planes. 2) Creating the manual Centerline (points in the center of the vessel) I zoom in to work with a larger image I press the space bar to get the axes out of the way I select the centerline path tool I click and place points in the center of the vessel along its course After 3 points, the 4th window already starts reconstructing the Curved view I keep going down and marking: aorta → common iliac → external iliac (main path) 3) Identifying branches and checking position (green dot + MIP) When hovering the mouse over the Curved window, a green dot in the other windows shows where you are in the vessel I use MIP (Maximum Intensity Projection) to increase the slice thickness and see the anatomy better This makes it clear where the internal iliac origin is and where the vessel continues into the external iliac I also rotate the image to confirm by the anatomy 4) Stretched vs Straightened (and centerline correction) Stretched: shows the curved vessel with the centerline, useful for correcting small imperfections I rotate to check that the green line is always in the center of the vessel Straightened: “straightens out” the vessel, making it easier to read and to measure in a straight line 5) Perpendicular slices (A, B, C) and what they mean The A, B and C markers correspond to the three side windows In Stretched mode, the slices can “cross” because of the curvature In Straightened, everything is aligned and easier to position These slices are always perpendicular to the green line (centerline) 6) Measuring the iliac length (extent) In Straightened, I use the straight ruler I measure from the chosen point (e.g., bifurcation) to the point in the internal/external iliac, depending on the goal In the example: the measurement along a “straighter” line was 5.18 cm when the curvature is taken into account, the measurement can change (e.g., 5.7 cm) Final message of the video: Centerline is especially useful for measuring distance/length (extent) The perpendicular slices can be used for diameter measurements