Impact of Microbubble Degradation and Flow Velocity on Subharmonic-aided Pressure Estimation (SHAPE): An Experimental Investigation.

OBJECTIVE: This study aimed to investigate the impact of microbubble degradation and flow velocity on Sub-Harmonic Aided Pressure Estimation (SHAPE), and to explore the correlation between subharmonic amplitude and pressure as a single factor. METHODS: We develop an open-loop vascular phantom platform system and utilize a commercial ultrasound machine and microbubbles for subharmonic imaging. Subharmonic amplitude was measured continuously at constant pressure and flow velocity to assess the impact of microbubble degradation. Flow velocity was varied within a range of 4-14 cm/s at constant pressure to investigate its relationship to subharmonic amplitude. Furthermore, pressure was varied within a range of 10-110 mm Hg at constant flow velocity to assess its isolated effect on subharmonic amplitude. RESULTS: Under constant pressure and flow velocity, subharmonic amplitude exhibited a continuous decrease at an average rate of 0.221 dB/min, signifying ongoing microbubble degradation during the experimental procedures. Subharmonic amplitude demonstrated a positive correlation with flow velocity, with a variation ratio of 0.423 dB/(cm/s). Under controlled conditions of microbubble degradation and flow velocity, a strong negative linear correlation was observed between pressure and subharmonic amplitude across different Mechanical Index (MI) settings (all R2 > 0.90). The sensitivity of SHAPE was determined to be 0.025 dB/mmHg at an MI of 0.04. CONCLUSION: The assessment of SHAPE sensitivity is affected by microbubble degradation and flow velocity. Excluding the aforementioned influencing factors, a strong linear negative correlation between pressure and subharmonic amplitude was still evident, albeit with a sensitivity coefficient lower than previously reported values.

Contrast-enhanced ultrasound for evaluating arteritis activity in Takayasu arteritis patients.

INTRODUCTION: Contrast-enhanced ultrasound (CEUS) was recently used to evaluate vascularization within the carotid artery wall, and this process of vascularization was correlated with arteritis activity. We aimed to use CEUS to evaluate disease activity in Takayasu arteritis (TAK) patients. METHOD: We used CEUS to analyze 28 consecutive TAK patients. Disease activity was assessed according to the NIH criteria. We measured CEUS grades and assessed the correlation between contrast features and disease activity. RESULTS: Higher erythrocyte sedimentation rates (ESRs) were found (35 ± 28.7 vs. 13 ± 7.4 mm/h, p < 0.01), and CEUS carotid wall enhancement was more frequently (100% vs. 36.6%, p < 0.01) seen in TAK patients in the active phase than in those in the inactive phase. With increasing CEUS grades, both the artery wall thickness and ESR increased, and patients were more likely to be in the active phase (0 in grade 0, 42.9% in grade 1, and 75% in grade 2). Receiver operating characteristic (ROC) curve analysis showed that CEUS had an area under the ROC curve (AUC) of 0.872 (95% CI 0.785-0.959, p < 0.01), demonstrating good diagnostic accuracy. CONCLUSIONS: Higher CEUS grades reliably identify patients with active TAK.Key Points• No CEUS vascularization is obviously relative with the inactive disease of TAK patients.• Obvious CEUS vascularization is obviously relative with the active disease of TAK patients.