Which sequence correctly describes a DSA run-off procedure?

Which sequence correctly describes a DSA run-off procedure?

• A. Scout run without contrast, bolus chase with contrast, computer subtracts boney landmarks and motion
• B. Scout run with contrast, bolus chase without contrast, no subtraction
• C. Continuous fluoroscopy with contrast without subtraction
• D. Only scout run without any contrast

Answer: (A)

The main idea is that a DSA run-off uses a three-part workflow to clearly image vessels: first obtain a pre-contrast scout image to map anatomy, then perform a contrast bolus chase to visualize the vessels as the contrast passes through, and finally apply computer subtraction to remove bones and background tissue so the vessels stand out. Starting with a scout image taken without any contrast gives a reference “mask” of the bones and tissues. Next, you inject contrast and run a bolus chase, capturing the moment the contrast travels through the aorta and into the peripheral vessels. Finally, you subtract the pre-contrast mask from the contrast frames, removing bony landmarks and stationary tissue (and compensating for motion when possible), so the vessels become clearly visible against a dark background. This sequence is essential because, without the initial mask, subtraction can’t effectively remove bones; without the contrast chase, there’s nothing to visualize; and without subtraction, the bones and soft tissue obscure the vessels.

The main idea is that a DSA run-off uses a three-part workflow to clearly image vessels: first obtain a pre-contrast scout image to map anatomy, then perform a contrast bolus chase to visualize the vessels as the contrast passes through, and finally apply computer subtraction to remove bones and background tissue so the vessels stand out.

Starting with a scout image taken without any contrast gives a reference “mask” of the bones and tissues. Next, you inject contrast and run a bolus chase, capturing the moment the contrast travels through the aorta and into the peripheral vessels. Finally, you subtract the pre-contrast mask from the contrast frames, removing bony landmarks and stationary tissue (and compensating for motion when possible), so the vessels become clearly visible against a dark background.

This sequence is essential because, without the initial mask, subtraction can’t effectively remove bones; without the contrast chase, there’s nothing to visualize; and without subtraction, the bones and soft tissue obscure the vessels.