Abstract
Purpose: Because measurement errors are caused by the Doppler incident angle in ultrasound velocity estimation, it is said that the incident angle should be within 60 degrees. However, previous reports showed that if the incident angle was within 60 degrees or less, the measurements were greater than the actual velocity. We reevaluated overestimation of velocity with the Doppler incident angle. Methods: A string phantom was installed in a water tank and set at a constant speed of 100 cm/s. The ultrasound linear-array transducer was adjusted so that the incident angles were 45 degrees, 50 degrees, and 60 degrees. The transducer was fixed in a state where a measurement error did not appear. The velocities of the string phantom were measured at the Doppler incident angle of 45 degrees, 50 degrees, and 60 degrees three times, respectively. Results: The means of peak velocity at the incident angle of 45 degrees, 50 degrees, and 60 degrees were 120.1 cm/s, 124.2 cm/s, and 135.2 cm/s, respectively. Even with an incident angle of 45 degrees, the overestimation of velocity was approximately 20%. As the incident angle became larger, the overestimation of velocity increased. Conclusion: Even if the incident angle is 60 degrees or less, flow velocity may be overestimated.
