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High frame rate color flow echocardiography: A comparison of different imaging approaches

Quantitative measurements by color flow imaging (CFI) are hindered by both low temporal resolution and a limited field of view. These limitations can be overcome by recent high frame rate (HFR) imaging techniques. However, as these HFR techniques reduce image quality and penetration depth to a different degree, the aim of this study was to compare the impact of HFR techniques on CFI. Hereto, phantom and in-vivo images were recorded using a cardiac phased array (P4-2v) connected to a Vantage 256 system (Verasonics) in order to scan a 90 deg wide, 12 cm deep sector. Different HFR scan sequences were tested, including multi-line transmission with 4 simultaneously transmitted beams (4MLT), diverging waves with 2 different opening angles, 2φ = 20 deg (DW20) and 90 deg (DW90), as well as single-line transmission (SLT) as a benchmark. For a fair comparison and to evaluate a clinical applicability, the acoustic output was equalized for all sequences, for which the heating of the probe was the main restriction. Results show that HFR techniques spread artifacts on larger areas compared to SLT (>+50%), but the velocity estimates are still comparable (relative error < 6%). 4MLT and DW20 achieved similar performance and enable wide-angle CFI at HFRs (78 Hz in continuous acquisition over 90 deg). On the other hand, DW90 boosts the frame rate up to 625 Hz but with a reduction of the penetration depth (up to −5/6 cm).