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Table 1 Issues limiting optimal flow quantification

From: High-frame-rate contrast-enhanced ultrasound particle image velocimetry in patients with a stented superficial femoral artery: a feasibility study

Limiting issue

Description

Loss of correlation

Complete saturation of contrast image, high velocities/high spatial velocity gradients, or complex out-of-plane flow during systole causing a decreased cross-correlation in the PIV analysis due to loss of speckle coherency between frames. When a region of multiple vectors with cross-correlations < 0.2 existed, the “loss of correlation” category was selected.

Short vessel segment

Anatomical characteristics causing only a part of the vessel to be captured inside the imaged plane. When the length of the imaged vessel appeared smaller than 4 times its diameter, the “short vessel segment” category was selected.

Partial shadowing

Partial shadow regions with lower or no contrast signal, probably due to calcified lesions inside the image plane, compromising PIV analysis. When such a location with low contrast and subsequent spurious vectors appeared during the entire cardiac cycle, the “partial shadowing” category was selected.

Loss of contrast agent

Decrease in contrast signal during diastole due to severe destruction of the microbubbles because of the prolonged insonification period at lower velocities. When no vectors were obtained during multiple frames at the end of diastole, the “loss of contrast” category was selected.

  1. PIV Particle image velocimetry, UCA Ultrasound contrast agent