Xu L. et al., 2025: Measurement and spectral analysis of medical shock wave parameters based on flexible PVDF sensors.
Liansheng Xu 1, Fei Shen 1, Fan Fan 1, Qiong Wu 1, Li Wang 1, Fengji Li 1, Yubo Fan 1, Haijun Niu 2
1School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing, 100191, China.
2School of Biological Science and Medical Engineering, Beihang University, 37 Xueyuan Road, Haidian District, Beijing, 100191, China.
Abstract
Extracorporeal shock wave therapy (ESWT) achieves its therapeutic purpose mainly through the biological effects produced by the interaction of shock waves with tissues, and the accurate measurement and calculation of the mechanical parameters of shock waves in tissues are of great significance in formulating the therapeutic strategy and evaluating the therapeutic effect. This study utilizes the approach of implanting flexible polyvinylidene fluoride (PVDF) vibration sensors inside the tissue-mimicking phantom of various thicknesses to capture waveforms at different depths during the impact process in real time. Parameters including positive and negative pressure changes (P+, P-), pulse wave rise time ([Formula: see text]), and energy flux density (EFD) are calculated, and frequency spectrum analysis of the waveforms is conducted. The dynamic response, propagation process, and attenuation law of the shock wave in the phantom under different impact intensities were analyzed. Results showed that flexible PVDF sensors could precisely acquire the characteristics of pulse waveform propagating within the phantom. At the same depth, as the driving pressure increases, P+ and P- increase linearly, and [Formula: see text] remains constant. At the same driving pressure, P+, P-, and EFD decay exponentially with increasing propagation depth. At the same depth, the spectra of pulse waveforms are similar, and the increasing driving pressure does not cause significant changes in carrier frequency and modulation frequency. The research findings could provide a reference for developing ESWT devices, improving treatment strategies, and enhancing the safety of clinical applications.
Phys Eng Sci Med. 2025 Jan 28. doi: 10.1007/s13246-025-01519-z. Online ahead of print.
PMID: 39873955
Comments 1
Introduction: Extracorporeal Shock Wave Therapy (ESWT) has evolved from traditional extracorporeal shock wave lithotripsy (ESWL) and is used in various fields, including orthopedics and cosmetic surgery. It relies on the mechanical effects of shock waves in tissues to promote healing (e.g., cell growth, angiogenesis). Despite its efficacy, the parameters of shock waves (like pressure and energy) are not easily measurable, often relying on clinical experience rather than precise data.
Objectives: The study aims to obtain more accurate shock wave parameters and propagation characteristics within tissue, addressing the gap in knowledge about how shock waves behave in biological tissues compared to simplified models used in previous studies.
Methods
Experimental Setup: The study uses a laboratory shockwave generation controller (D15, Hunan Astiland Medical Instrument Co., China), and PVDF membrane sensors to capture shock wave dynamics in tissue-mimicking phantoms.
Phantom Design: Soft tissue phantoms were created using silicone, allowing for controlled measurements at varying depths (1mm to 20mm).The experiments involved applying different driving pressures (ranging from 1.5 to 7 bar) and measuring the shock waves generated.
Results
Shock Pulse Characteristics: Data showed that shock waves produced varying amplitudes and durations based on driving pressure and depth.
Exponential Decay: Pressure and energy flux density of shock waves decreased exponentially with increased depth in the phantoms. The results indicated that energy dissipates rapidly, limiting the effective therapeutic range.
Frequency Analysis: Two distinct peak frequencies were identified in the shock wave spectra, which are linked to the mechanical properties of the source and the phantom material.
Discussion
The findings suggest that PVDF sensors are effective for capturing shock wave dynamics. Increasing the driving pressure enhances the shock wave amplitude but also raises the risk of superficial tissue damage. The study emphasizes the complexity of shock wave propagation in tissues and the necessity for precise measurement techniques to optimize ESWT.
What could this include, even if ESWT is a very safe procedure?
Understanding Tissue Interactions: While ESWT is indeed considered a safe procedure overall, understanding how shock waves interact with different types of tissues at various depths can help clinicians avoid potential adverse effects. Precise measurements can help elucidate the thresholds of pressure and energy that may cause unintended tissue damage.
Optimizing Treatment Parameters: By gaining a better understanding of the parameters that affect shock wave intensity and propagation, practitioners can fine-tune treatment protocols for individual patients. This could involve adjusting parameters like driving pressure to maximize therapeutic effects while minimizing any risks, particularly in sensitive areas.
Identifying Safe Boundaries: The data obtained from detailed measurements can help define safe operational boundaries for shock wave application. For instance, knowing the exact energy flux density and pressure peaks at varying depths can guide clinicians in selecting the appropriate settings for specific conditions or patient anatomies.
Reducing Trial-and-Error Approaches: Currently, many practitioners rely on personal experience and generalized treatment protocols, which can vary widely. Improved measurements would allow for a more evidence-based approach, potentially reducing instances of treatment failure or adverse reactions.
Clarifying Patient-Specific Responses: Different patients may respond differently to ESWT based on their individual tissue properties (like density and elasticity). Precise measurements could help tailor the therapy to optimize responses while ensuring that safety is maintained across varying patient profiles.
Monitoring Post-Treatment Effects: Enhanced measurement techniques could allow for monitoring not only during treatment but also in post-treatment recovery, helping to identify if reactions (positive or negative) occur after the administration of shock waves.
Conclusion
The research establishes a methodology for measuring the dynamic parameters of shock waves using flexible sensors, providing a foundation for improving clinical applications and devices in ESWT. Future studies are needed to examine interactions in more complex media and shock scenarios.This study contributes to a better understanding of shock wave therapy's efficacy and safety, potentially leading to improved treatment protocols in clinical settings
The argument regarding the improvement of safety in Extracorporeal Shock Wave Therapy (ESWT) through precise measurements and analysis is rooted in the complexity of shock wave propagation in biological tissues and the current limitations of measurement techniques. Here are several points that might clarify the authors' rationale:
In summary, while ESWT is generally safe, the authors likely argue that thorough measurement and analysis can lead to enhanced safety by giving practitioners better tools to customize and optimize treatments. This proactive approach can mitigate risks, improve outcomes, and instill greater confidence in the use of ESWT.
Jens Rassweiler