To obtain a graft flow volume, which three steps should be completed?

• A. Select a clean site mid graft; Expand the sample gate to the diameter of the vessel
• B. Obtain the lumen diameter measurement; Expand the sample gate to the diameter of the vessel
• C. Select a clean site mid graft; Obtain the lumen diameter measurement; Expand the sample gate to the diameter of the vessel
• D. Expand the sample gate to the diameter of the vessel; Select a clean site mid graft; Obtain the lumen diameter measurement

Answer: (C)

Flow volume in a graft relies on cross-sectional area and velocity through that area. To get a valid measurement, start by choosing a clean site mid graft so you sample a representative, undisturbed segment. Then obtain the lumen diameter at that site so you can calculate the cross-sectional area. Finally, expand the Doppler sample gate to match the vessel diameter so the velocity-time integral reflects flow across the full lumen. This sequence ensures the gate width corresponds to the actual lumen size and the velocity measurement encompasses the entire cross-section, giving an accurate flow volume. Omitting any step or ordering them incorrectly can lead to an incorrect area estimate or an incomplete velocity measurement; hence the combination of a mid-graft site, diameter measurement, and a properly sized gate is essential.