Innovations in Ultrasound Technology in the Management of Kidney Stones

Biomimetic Ultrasonic Vibrator with Broadband Characteristics Inspired by Leaf-Cutting Ants

Power ultrasound is widely used in industrial production, medical equipment, aerospace, and other fields. Currently, there are two main types of commonly used power generation devices: piezoelectric ultrasonic transducers and magnetostrictive ultrasonic transducers. However, in certain situations with limited external dimensions, the applications of existing power ultrasound devices are limited. In nature, leaf-cutting ants excite vibrations through their tiny organs. Inspired by the vibratory organs of leaf-cutting ants, a new type of biomimetic ultrasonic vibrator (BUV) comprising a scraper, dentate disc, and fixture system was proposed, fabricated, and tested in this study. The experimental results showed that the BUV could operate in the frequency range of 16.8-19 kHz. Within the working frequency range, the vibration of the BUV was stable and the amplitude of the vibration displacement was greater than 22 µm. The operating frequency band of the BUV was broader than those of the piezoelectric and magnetostrictive ultrasonic transducers. In addition, the BUV can cut soft rubber and pig tissues with sufficient output power and load-carrying capacity. The BUV, as a new type of power ultrasonic excitation device, is expected to be applied in high-power micro operating scenarios, such as minimally invasive surgical instruments.

Technological innovations in shock wave lithotripsy

INTRODUCTION

Since 1980, extracorporeal shock wave lithotripsy (SWL) has been employed in the treatment of urolithiasis, offering noninvasive alternatives to surgical techniques. In addition to being limited by the size and location of the stones, its efficacy is influenced by several factors. Despite the advancement of other surgical techniques, SWL could maintain its position with new improvements. Our objective is to review the existing literature on the latest advances in the extracorporeal treatment of lithiasis.

MATERIAL AND METHODS

A non-systematic literature review was carried out from 2017 to 2023 to obtain 26 articles on three different emerging technologies in extracorporeal lithotripsy: Burst Wave Lithotripsy (BWL), Histotripsy, and Microbubble Lithotripsy (ML).

RESULTS

The BWL uses sinusoidal bursts of US waves delivered at lower and higher frequencies than conventional SWL. Its mechanism of action generates a higher quality fragmentation (fine fragments) instead of generating tensile stresses for stone fracture resulting in larger fragments, as in traditional SWL. Studies in pigs and humans have shown effective fragmentation with a good safety profile. Based on High Intensity Focused Ultrasound (HIFU) technology, histotripsy fragments tissue through cavitation. Good in vitro results have been shown, but the formation of microbubbles between the stone and ultrasound waves hinders the progress of this technique. Microbubble Lithotripsy (ML) combines microbubbles and ultrasound for safe and effective stone fragmentation. In vitro and pig results are promising. This technique can help optimize treatments and reduce energy levels.

CONCLUSIONS

Technological innovation is not only being applied to endourological techniques, but also to ESWL. New techniques such as BWL, histotripsy and ML are promising, with good results in the research phase.

Role of Posterior Acoustic Shadow Width in Ultrasound in Determining Stone Size in Urolithiasis

Introduction Ultrasound (US) is frequently the initial diagnostic tool for urolithiasis, though computed tomography (CT) remains the imaging modality of choice. However, due to potential overestimations, the accuracy of US in gauging stone size has been a point of contention. This study aims to compare the accuracy of stone size measurements in US, specifically evaluating the utility of the posterior acoustic shadow (PAS) width, against the CT measurements. Methods We conducted a cross-sectional study where 120 adult patients (aged >18 years) with confirmed urolithiasis through CT participated. Stone sizes were assessed via both CT and US, with the PAS width also being measured in the latter. Statistical analysis compared stone size discrepancies between both CT and US measurement techniques. Results The study enrolled 73 males and 47 females with various stone locations. The average stone sizes were 15.93 ± 4.59 mm (CT), 18.60 ± 4.80 mm (US), and 16.69 ± 4.61 mm (PAS width). There was a mean difference of 2.67 mm (p < 0.0001) between CT and US sizes, whereas the difference between the PAS width and CT sizes was only 0.75 mm (p = 0.203). Stone size miscalculation by US was 16.77%, whereas it was only 4.77% for PAS width. Conclusion US tends to significantly overestimate stone size when compared to CT. Conversely, the measurement of the PAS width in US presents a more aligned estimation to CT outputs. Integrating PAS width into routine US reporting can enhance the accuracy of stone size estimation, optimizing urolithiasis management and patient counseling.

Ultrasound-guided extracorporeal shock wave lithotripsy with minimal x-ray exposure prevented genitourinary tract injury patients with urolithiasis in Taiwan

BACKGROUND

This study investigated the use of ultrasound-guided extracorporeal shock wave lithotripsy (ESWL) to break stones in the genitourinary tract and prevent genitourinary injury. Our goals were to achieve accurate focusing and minimal X-ray exposure for the benefit of the patients.

METHODS

The LiteMed LM-9200 lithotripter with ultrasonography and fluoroscopy was used for two different procedures: autoaimed and autoperiodical. These procedures enabled dual focusing on stone localization and tracking.

RESULTS

Out of 108 patients who underwent autoperiodical procedures, 29 had no gross hematuria. Among the 335 patients who received autoaimed procedures, 194 had no gross hematuria. The average duration of X-ray exposure during autoperiodical and autoaimed procedures was 120 and 50 s, respectively.

CONCLUSION

The ultrasound-guided ESWL with minimal X-ray exposure was found to be useful in treating genitourinary upper-tract urolithiasis in the autoaimed procedure. Patients who underwent the autoaimed procedure experienced less gross hematuria compared to those who underwent the autoperiodical procedure.

Ultrasonic Imaging Based on Pulsed Airy Beams

In ultrasonic imaging, high impedance obstacles in tissues may lead to artifacts behind them, making the examination of the target area difficult. Acoustical Airy beams possess the characteristics of self-bending and self-healing within a specific range. They are limited-diffracting when generated from finite aperture sources and are expected to have great potential in medical imaging and therapy. In this article, pulsed Airy (pAiry) beams are employed for ultrasonic imaging at megahertz frequency, and the protocol is demonstrated via both simulations and experiments. First, the generation of pAiry beams using a linear array is simulated, and the pulsed beams inherit some characteristics of continuous wave Airy beams, such as propagating along curved paths and self-healing. In experiments where obstacles are present at the beam paths, the image quality in pAiry-based imaging is superior to that in classical iso-depth imaging. The results demonstrate the feasibility and benefits of ultrasonic imaging based on pAiry beams and provide an important basis for developing imaging techniques employing nondiffracting acoustic beams.

Needle Aligned Ultrasound Image-Guided Access Through Dual-Segment Array

Ultrasound (US) guided access for percutaneous nephrolithotomy (PCNL) is gaining popularity in the urology community as it reduces radiation risk. The most popular technique involves manual image-needle alignment. A misaligned needle however needs to be retracted and reinserted, resulting in a lengthened operation time and complications such as bleeding. These limitations can be mitigated through the co-registration between the US array and needle. The through-hole array concept provides the primary solution, including a hole at the center of the array. Because of the central opening, the image-needle alignment is achieved inherently. Previous literature has described applications that are limited to superficial and intravascular procedures, suggesting that developing a through-hole array for deeper target applications would be a new breakthrough.

OBJECTIVE

Here, we present a dual-segment array with a central opening. As the prototype development, two segments of 32-element arrays are combined with an open space of 10 mm in length in between them.

METHOD

We conducted phantom and ex-vivo studies considering the target depth of the 80-100 mm range. The image quality and needle visibility are evaluated by comparing the signal-to-noise ratio (SNR), full width at half maximum (FWHM), and contrast-to-noise ratio (CNR) results measured with a no-hole linear array under equivalent conditions. An ex-vivo study is performed using porcine kidneys with ceramic balls embedded to evaluate the needle access accuracy.

RESULTS AND CONCLUSION

The mean needle access error of 20 trials is found to be 2.94 ±1.09 mm, suggesting its potential impact on realizing a simple and intuitive deep US image-guided access.

Application of ultrasound imaging in the treatment of urinary tract stones

Urinary tract stones are a common clinical condition that affect millions of individuals worldwide. The management of these stones has evolved significantly over the past 70 years, and ultrasound imaging has emerged as a valuable tool for diagnosis, treatment planning, and follow-up. This review aims to provide an overview of the application of ultrasound imaging in the treatment of urinary tract stones, highlighting its advantages, limitations, and current advancements in the field.

Modified FMCW Scheme for Improved Ultrasonic Positioning and Ranging of Unmanned Ground Vehicles at Distances < 50 mm

Unmanned ground vehicles (UGVs) find extensive use in various applications, including that within industrial environments. Efforts have been made to develop cheap, portable, and light-ranging/positioning systems to accurately locate their absolute/relative position and to automatically avoid potential obstacles and/or collisions with other drones. To this aim, a promising solution is the use of ultrasonic systems, which can be set up on UGVs and can potentially output a precise reconstruction of the drone's surroundings. In this framework, a so-called frequency-modulated continuous wave (FMCW) scheme is widely employed as a distance estimator. However, this technique suffers from low repeatability and accuracy at ranges of less than 50 mm when used in combination with low-resource hardware and commercial narrowband transducers, which is a distance range of the utmost importance to avoid potential collisions and/or imaging UGV surroundings. We hereby propose a modified FMCW-based scheme using an ad hoc time-shift of the reference signal. This was shown to improve performance at ranges below 50 mm while leaving the signal unaltered at greater distances. The capabilities of the modified FMCW were evaluated numerically and experimentally. A dramatic enhancement in performance was found for the proposed FMCW with respect to its standard counterpart, which is very close to that of the correlation approach. This work paves the way for the future use of FMCWs in applications requiring high precision.

Multiphysics Analysis of Ultrasonic Shock Wave Lithotripsy and Side Effects on Surrounding Tissues

Background:

Today, the most common method for kidney stone therapy is extracorporeal shock wave lithotripsy. Current research is a numerical simulation of kidney stone fragmentation via ultrasonic shock waves. Most numerical studies in lithotripsy have been carried out using the elasticity or energy method and neglected the dissipation phenomenon. In the current study, it is solved by not only the linear acoustics equation, but also the Westervelt acoustics equation which nonlinearity and dissipation are involved.

Objective:

This study is to compare two methods for simulation of shock wave lithotripsy, clarifying the effect of shock wave profiles and stones’ material, and investigating side effects on surrounding tissues

Material and Methods:

Computational study is done using COMSOL Multiphysics, commercial software based on the finite element method. Nonlinear governing equations of acoustics, elasticity and bioheat-transfer are coupled and solved.

Results:

A decrease in the rise time of shock wave leads to increase the produced acoustic pressure and enlarge focus region. The shock wave damages kidney tissues in both linear and nonlinear simulation but the damage due to high temperature is very negligible compared to the High Intensity Focused Ultrasound (HIFU).

Conclusion:

Disaffiliation of wave nonlinearity causes a high incompatibility with reality. Stone’s material is an important factor, affecting the fragmentation

The Trends of Urolithiasis Therapeutic Interventions over the Last 20 Years: A Bibliographic Study

Introduction: The clinical and economic burden of kidney stones is a challenge for the healthcare system. There is a limited bibliometric project exploring the literature trends on 'urolithiasis' and its related management. Methods: A systematic review was conducted to discover the related abstracts regarding each specific issue, investigated year by year from May 2000 to May 2020 (20 years). To make an effective comparison, the statistics resulting from every single study were allocated to two 10-year periods: period 1 (2000 to 2010) and period 2 (2010 to 2020). In this study, we included all English language articles, all non-English articles with English abstracts, and studies in which interventions were used for stone removal, including laser technology. Also, we excluded the studies without a published abstract, an intervention or a laser, animal and in vitro studies, and case reports. Results: These articles are about ureteroscopy (URS) (n=10360, 33.45%), percutaneous nephrolithotomy (PCN) (n =10790, 34.84%) and extra-corporeal shockwave lithotripsy (ESWL) (n=9846, 31.76%). When evaluating the two time periods, there were 9912 studies available in period one, which increased by ×2.12 times (112.71% rise) to 21084 studies in period two (P = 0.001). The increase was 133%, 103.51%, and 70.4% for URS, PCN, and SWL respectively. A total of 855 studies on Laser application via URS were published on PubMed over a 20-year period. There was an increasing trend toward using laser application via URS over the study period. Also, there were 230 articles published in period one, which increased by nearly 2.71 times (rise of 171.73%) to 625 papers in period two (P < 0.001). There was an increasing trend toward using laser application via PCN; 126 papers were published in period one, which increased by nearly 3.05 times (rise of 205.5%) to 385 papers in period two (P = 0.002). Conclusion: The minimal invasive interventions for stone removal, including URS and PCN, increased dramatically in the last decade, and the use of lasers in stone treatment increased significantly in the last decade.

Point-of-care ultrasound in nephrology

PURPOSE OF REVIEW

The use of POCUS has grown tremendously with the introduction of innovative, easy-to-carry and maneuver hand-held devices. This review focuses on nephrology-centric applications of POCUS that can be incorporated on a daily basis to make impactful and prompt clinical decisions.

RECENT FINDINGS

We review articles covering use of POCUS in the dialysis unit, the Emergency Department, office, and ICU for assessment of volume status, access issues, stones, obstruction, and to help manage patients with AKI, shock, and heart failure.

SUMMARY

POCUS is a welcome addition to our bedside diagnostic armamentarium and has great utility in nephrology. Trials are ongoing in evaluating outcomes with POCUS and physicians' clinical experience using it has been extremely positive.

Evaluation of a child with suspected nephrolithiasis

PURPOSE OF REVIEW

As the incidence of nephrolithiasis in children doubles every 10 years it is becoming a common disease associated with significant morbidity along with considerable economic burden worldwide. The aim of this review is to summarize current data on the epidemiology and causes of renal stones in children and to provide a frame for the first clinical evaluation of a child with suspected nephrolithiasis.

RECENT FINDINGS

Dietary and environmental factors are the driving force of changing epidemiology. Diagnosis should be based on medical history, presenting signs, examination, first laboratory and radiological workup. Ultrasound should be the initial diagnostic imaging performed in pediatric patients while low-dose computed tomography is rarely necessary for management. Metabolic factors including hypercalciuria, hypocitraturia, low fluid intake as well as specific genetic diseases should be explored after the resolution of initial signs and symptoms.

SUMMARY

Appropriate initial evaluation, imaging technique, identification of risk factors and other abnormalities are essential for early diagnosis and prevention of stone-related morbidity in children with suspected nephrolithiasis.