From the Guidelines
Ultrasound exams with high mechanical index (MI) settings, typically above 0.3, can increase the possibility of inertial cavitation, as evidenced by studies assessing MIs above 0.3 which reported an increase in deleterious structural effects as the MI increased 1.
Key Factors Influencing Inertial Cavitation
- Mechanical index (MI) values: Higher MI values increase the likelihood of inertial cavitation, with studies showing adverse effects at MIs above 0.3 1
- Ultrasound frequency and pulse duration: Lower frequencies and longer pulse durations may contribute to increased cavitation risk, although specific thresholds are not well-defined in the provided evidence
- Focused beams and local intensities: Higher local intensities, such as those created by focused beams, can increase the risk of inertial cavitation
Clinical Implications
- Diagnostic applications with high MI settings, such as contrast-enhanced ultrasound (CEUS) examinations, may increase the risk of inertial cavitation
- Therapeutic ultrasound procedures, like high-intensity focused ultrasound (HIFU), also carry increased risk of inertial cavitation
- Clinicians should use the lowest mechanical index settings necessary for adequate diagnostic information to minimize the risk of inertial cavitation, especially when contrast agents are used 1
Balancing Risks and Benefits
- While higher MI values may improve drug delivery, they also increase the risk of cell injury and adverse effects, highlighting the need for a balanced approach in clinical practice 1
From the Research
Ultrasound Exams and Inertial Cavitation
- High-intensity focused ultrasound (HIFU) has been shown to increase the possibility of inertial cavitation 2, 3, 4.
- The use of a two-frequency wave, consisting of a high-frequency ultrasound pulse and a low-frequency trailing pulse, can control the collapse of cloud cavitation and increase inertial cavitation 2, 3, 4.
- Inertial cavitation can be detected using passive cavitation detection (PCD) and can vary with the progress of HIFU treatment 5.
- The optimal stone-to-source distance for maximizing cavitation-induced surface damage area has been determined to be the region where the acoustic beam and acoustic cavitation activity near the stone surface is the widest 6.
Factors Affecting Inertial Cavitation
- Pulse duration and pulse repetition frequency (PRF) can affect the level of inertial cavitation, with longer pulse durations and higher PRF initially increasing inertial cavitation but then decreasing it 5.
- The presence of a model stone in the acoustic path length can affect the formation and trajectory of cavitation bubbles 6.
- The location of the cavitation cloud relative to the stone surface can affect the level of surface damage, with clouds located in preferential nucleation sites causing more damage 6.