Digital Subtraction Angiography (DSA)

OsiriX and Horos Course · Image and Export

In this lesson I show how to perform digital subtraction angiography (DSA) in OsiriX when the angiogram was saved to DICOM as a “raw” (unsubtracted) image, even if it already appeared subtracted on the machine. 1) Converting the raw angiogram into digital subtraction Open the study in the 2D Viewer Select Subtract Done: OsiriX generates the digitally subtracted image. In the video I demonstrate this with two examples: an angiographic study saved without subtraction a fibroid embolization, where subtraction greatly improves visualization 2) Creating a static image with the sum of the images Another useful technique is to add up all the images to obtain a single “consolidated” image of the contrast. The key point is choosing the correct projection: MinIP (Minimum Intensity Projection): ideal when the contrast appears darker/inverted — this way the contrast-filled structures accumulate in the sum. MIP (Maximum Intensity Projection): in this case it can “erase”/degrade the contrast, because it favors the highest values. Result: you end up with a static image with the sum of the digital subtraction frames.