A Real-time Proportional Feedback Controller for Sustaining Uniform Inertial Cavitation Dynamics of Flowing Bubbles

This study is designed to find out a suitable controller to realize a uniform inertial cavitation activity of microbubbles within a physiological relevant circulation system induced by pulsed ultrasound. As microbubbles are flowing in the circulating catheter or vessel, part of which (i.e. the target region) will undergo ultrasound stimulation and scatter cavitation signals. Due to the acoustic pulses and the flowing environment, number of intact bubbles inside the system would decease with time, and expressed a steady decline trend in real-time measured inertial cavitation dose (ICD(t)). Our controller has two consecutive regulate stages, and the initial stage is designed to raise ICD(t) to the target ICD (TICD) quickly while the second stage is expected to maintain the ICD(t) within a ±10% error band, respectively. We further employed three indicators to evaluate performances of these parameters, namely the rising time (tr), the proximity ratio (ε) and the normalized variability (δ). By the three indicators, we determined two ideal factors: 0.1 ×10
⁶
V
^-1
s
^-1
for P1 and 1.5 × 10
⁶
V
^-1
s
^-1
for P2, with them we had regulated ICD(t) for minutes and more than 82% of ICD(t) were regulated into the error band, any 7% of ICD(t) without control were in that error band. This may help in further research of target delivery or even clinical therapy.