Noninvasive assessment of pressure distribution and fractional flow in middle cerebral artery using microbubbles and plane wave in vitro

• Published in: Ultrasonics 2024-03, Vol.138, p.107244-107244, Article 107244
• Main Authors: Qiao, Xiaoyang, Zhang, Ruiyan, Yu, Jianjun, Yan, Yadi, Bouakaz, Ayache, Su, Xiao, Liu, Jiacheng, Zong, Yujin, Wan, Mingxi
• Format: Article
• Language: English
• Subjects: Fractional flow; Middle cerebral artery pressure; Plane wave; Subharmonic aided pressure estimation; Transcranial ultrasound; Ultrasound contrast agent
• ISSN: 0041-624X; 1874-9968
• DOI: 10.1016/j.ultras.2024.107244

•Subharmonic aided pressure estimation combined with plane wave transmission.•Estimate pressure distribution, fractional flow of middle cerebral artery in vitro.•The median error of pressure distribution estimation is 5.5 mmHg.•The fractional flow value is in high agreement with the value measured by sensor.•The mean ± standard deviations of the fractional flow difference is 0.01 ± 0.05. Fractional flow has been proposed for quantifying the degree of functional stenosis in cerebral arteries. Herein, subharmonic aided pressure estimation (SHAPE) combined with plane wave (PW) transmission was employed to noninvasively estimate the pressure distribution and fractional flow in the middle cerebral artery (MCA) in vitro. Consequently, the effects of incident sound pressure (peak negative pressures of 86–653 kPa), pulse repetition frequency (PRF), number of pulses, and blood flow rate on the subharmonic pressure relationship were investigated. The radio frequency data were stored and beamformed offline, and the subharmonic amplitude over a 0.4 MHz bandwidth was extracted using a 12-cycle PW at 4 MHz. The optimal incident sound pressure was 217 kPa without skull (sensitivity = 0.09 dB/mmHg; r2 = 0.997) and 410 kPa with skull (median sensitivity = 0.06 dB/mmHg; median r2 = 0.981). The optimal PRF was 500 Hz, as this value affords the highest sensitivity (0.09 dB/mmHg; r2 = 0.976) and temporal resolution. In addition, the blood flow rate exhibited a lesser effect on the subharmonic pressure relationship in our experimental setup. Using the optimized parameters, the blood pressure distribution and fractional flow (FFs) were measured. As such, the FFs value was in high agreement with the value measured using the pressure sensor (FFm). The mean ± standard deviations of the FF difference (FFm − FFs) were 0.03 ± 0.06 without skull and 0.01 ± 0.05 with skull.