Role of Hounsfield Unit in Predicting Outcomes of Shock Wave Lithotripsy for Renal Calculi: Outcomes of a Systematic Review

Optimal stone density for ablation lithotripsy with vapor tunnel Ho:YAG pulse modality

INTRODUCTION

Vapor-Tunnel™ (VT) consists of a very long pulse that uses the minimum peak power, causing the energy to pass through a previously created vapor channel or tunnel. There are studies that have shown acceptable ablation lithotripsy efficiency. Nevertheless, there are no in-vivo studies that have compared the VT performance according to the stone density.

METHODS

A retrospective study of 152 patients who underwent RIRS using VT Ho:YAG laser was performed. We divided the patients according to the stone density (Group 1: < 1000UH vs. Group 2: > 1000UH). We assessed the lithotripsy efficiency (mm3/JJ) and the laser-energy consumption (JJ/mm3). The stone-free rate (SFR) was defined as the absence of stone fragments in a non-contrast abdominal computed tomography 4 weeks after the procedure.

RESULTS

Ninety three patients were included in Group 1 and 59 in Group 2. Body mass index was higher in Group 1 and the median stone volume was higher in Group 2 (846 vs. 672 mm3, p = 0.03). Total energy used (11.9 vs. 24 kj, p < 0.001), the laser emission time (19 vs. 30 min, p < 0.001), and the total operative time (60 vs. 85 min, p < 0.001) were lower in the Group 1. SFR was higher in Group 1 (96.7% vs. 57.6%, p < 0.001) with a global SFR of 81.6%. The ablation lithotripsy efficiency was higher in Group 1 (0.053 mm3/JJ vs. 0.035 mm3/JJ, p < 0.001).

CONCLUSIONS

VT Ho:YAG was associated with decreased laser time, operative time and laser-energy consumption in Group 1 than Group 2. Similarly, VT Ho:YAG increased lithotripsy efficiency and the SFR compared to hard stones with the same laser settings and pulse modality.

The Association Between Stone Heterogenicity and the Success of Shock Wave Lithotripsy for High Density Upper Urinary Tract Stones: A Muti-Center Prospective Cohort

OBJECTIVE

To prospectively investigate the predictive value of radiological stone heterogenicity for the success of shock-wave lithotripsy (SWL) in patients with high-density upper urinary tract stones.

METHODS

This multi-center prospective study was conducted from June 2020 to December 2023. The radiological stone density index measured by computed tomography (CT) included the mean, standard deviation (SD), and coefficient variation (CV) of the Hounsfield Unit value of stones. The success was defined as no evidence of clinically significant stone fragments (≥4 mm) on a plain X-ray and ultrasound of the upper urinary tract 1 month after SWL. Binary logistic regression models were used to assess the odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Finally, 533 patients with high-density upper urinary tract stones were enrolled in this study. There were 68.5% (379/533) patients experienced success after SWL treatment. After adjusted confounding variables, compared with the patients in the lowest quartile of stone density index, the odds ratios (95% CI) for the extreme quartile was 1.42 (0.71, 2.81, P for trend = .443), .03 (.01, .09, P for trend <.001), and .02 (.01, .07, P for trend <.001) for MSD, SD, and CV, respectively. Furthermore, this linear association was confirmed only for SD and CV regardless of gender, body mass index, stone size, and stone location.

CONCLUSION

This multi-center prospective study demonstrated a positive association between the stone heterogenicity and the success of SWL in patients with high-density upper urinary tract stones regardless of gender, body mass index, stone size, and stone location. However, this association was not observed in mean stone density.

Numerical study of cavitation shock wave emission in the thin liquid layer by power ultrasonic vibratory machining

In the field of power ultrasonic vibration processing, the thin liquid layer nestled between the tool head and the material serves as a hotbed for cavitation shock wave emissions that significantly affect the material's surface. The precise manipulation of these emissions presents a formidable challenge, stemming from a historical deficit in the quantitative analysis of both the ultrasonic enhancement effect and the shock wave intensity within this niche environment. Our study addresses this gap by innovatively modifying the Gilmore-Akulichev equation, laying the groundwork for a sophisticated bubble dynamics model and a pioneering shock wave propagation model tailored to the thin liquid layer domain. Firstly, our study investigated the ultrasound enhancement effect under various parameters of thin liquid layers, revealing an amplification of ultrasound pressure in the thin liquid layer area by up to 7.47 times. The mathematical model was solved using the sixth-order Runge-Kutta method to examine shock wave velocity and pressure under different conditions. our study identified that geometric parameters of the tool head, thin liquid layer thickness, ultrasonic frequency, and initial bubble radius all significantly influenced shock wave emission. At an ultrasonic frequency of 60 kHz, the shock wave pressure at the measurement point exhibited a brief decrease from 182.6 to 179.5 MPa during an increase. Furthermore, rapid attenuation of the shock wave was found within the range of R0-3R0 from the bubble wall. This research model aims to enhance power ultrasonic vibration processing technology, and provide theoretical support for applications in related fields.

Variation coefficient of stone density and renal cortical thickness: the parameters evaluating non-contrast computed tomography imaging for predict extracorporeal shock wave lithotripsy success

The stone density (SD) is not the same in all parts of the stone due to the heterogeneous nature of the stone and the shock wave (SW) passes through tissues of many different densities until it reaches the stone. These factors affect the success of Extracorporeal Shock Wave Lithotripsy (ESWL). We aimed to evaluate the effect of the Variation Coefficient of Stone Density (VCSD) and Renal Cortical Tickness (RCT) on the success of ESWL. Between 2020 and 2023, 510 patients who underwent ESWL were divided into 2 groups treatment success (n:304) and treatment failure (n:206). Non-Contrast Computed Tomography (NCCT) imaging values of hydronephrosis degree of the kidney, stone location, stone volume (SV), stone-skin distance (SSD), SD, Standard deviation of Stone Density (SDSD), VCSD, RCT, Soft-Tissue Thickness (STT), Muscle Thickness (MT) were analyzed. VCSD value was obtained by dividing SDSD by SD. Along the SW, tissues were divided into three components: kidney (renal cortex), muscle and other soft tissues. RCT, MT and SSD were measured at three different angles (0°, 45°, and 90°) and these 3 lengths were averaged. In univariate analysis, Body Mass Index (BMI), SV, SD, VCSD, SSD, RCT and STT were demonstrated to affect ESWL success. In multivariate analysis, low BMI, SV, SD, RCT and large VCSD were significant independent predictors of ESWL success. Among these parameters, VCSD had the highest prediction accuracy, followed by SD, SV, RCT and BMI, respectively. This study demonstrated that VCSD value and RCT are predictive parameters in determining the treatment of patients with urinary calculi and selecting suitable ESWL candidates.

Comparison of ureteral stone measurements for predicting the efficacy of a single session of extracorporeal shockwave lithotripsy: one-, two-, and three-dimensional computed tomography measurements

The objective of this study was to compare the value of one-, two- and three-dimensional computed tomography (CT) measurements for predicting the efficacy of a single session of extracorporeal shock wave lithotripsy (ESWL) in patients with a single ureteral stone. A total of 165 patients were included based on the inclusion and exclusion criteria. Different models were constructed using a combination of patients' clinical data and measurements obtained by manual sketching and automated extraction software. Multivariate logistic regression was used to develop the models. Receiver operating characteristic curves were used to assess the performance of the models. There was good interobserver agreement for all measurements in different dimensions (P < 0.001). We also found that hydronephrosis, the largest diameter, the largest area, volume, and mean CT value were significantly greater in the failure group than in the success group (P < 0.01). Furthermore, all sizes and CT measurement values were found to be independent predictors for predicting efficacy after one session of ESWL (P < 0.05). In addition, the multivariate logistic analysis showed that the area under the curve (AUC) for two-dimensional and three-dimensional measurements was superior to that of one-dimensional measurement (P < 0.01). However, when size alone was included as a measurable predictor, there was no significant difference in the AUC among the one-, two-, and three-dimensional measurements (P > 0.05). In summary, after adjusting for clinical data, two- and three-dimensional measurements combining ureteral stone size and CT values were found to be the best predictors of ESWL efficacy, and software-based three-dimensional measurements should be considered to avoid interobserver variability in clinical practice.

Assessment of pancreatic ductal stone density on non-contrast computed tomography for predicting the outcome of extracorporeal shock wave lithotripsy

Background and study aims The utility of stone density at non-contrast computed tomography (NCCT) for predicting the effectiveness of extracorporeal shock wave lithotripsy (ESWL) in chronic calcific pancreatitis (CCP) is relatively unexplored. Patients and methods This was a prospective observational study of patients with CCP. Hounsfield units (HU) were determined for the largest pancreatic ductal stone during pretreatment NCCT. All patients underwent ESWL until the largest stone was fragmented to <3mm, followed by endoscopic retrograde cholangiopancreatography (ERCP) for stone extraction. The predictive factors following ESWL for successful stone extraction were studied and the receiver operating characteristic (ROC) curve determined the HU optimal cut-point. Results Eighty-two patients with a median (interquartile range) age of 36 years (range, 29-55); majority male 45 (54.9%), were included. Idiopathic CCP was noted in 78 patients (95.1%). The median stone density (SD) was 1095 HU (range, 860.7-1260.7) and the number of ESWL sessions was 2 (range, 2-3). Complete stone removal at index ERCP was achieved in 55 patients (67.1%). Those with partial clearance (n=27) needed a repeat ERCP, which was successful in 26 (96.3%); one patient (3.7%) underwent surgery. There was a significant, positive correlation between number of ESWL sessions and SD (r=0.797; P <0.001). On bivariate analysis, SD and the number of ESWL sessions revealed a significant association with complete ductal clearance. The optimal cut-point for complete stone removal by the ROC curve was 1106.5 HU (Youden index 0.726), with a sensitivity of 93% and a specificity of 80%. Conclusions The SD is a significant predictor of ESWL success followed by ductal clearance at ERCP, and <1106.5 HU is a predictor of good candidates for ESWL therapy.

Advancements in stone classification: unveiling the beauty of urolithiasis

PURPOSE

Urolithiasis has become increasingly prevalent, leading to higher disability-adjusted life years and deaths. Various stone classification systems have been developed to enhance the understanding of lithogenesis, aid urologists in treatment decisions, and predict recurrence risk. The aim of this manuscript is to provide an overview of different stone classification criteria.

METHODS

Two authors conducted a review of literature on studies relating to the classification of urolithiasis. A narrative synthesis for analysis of the studies was used.

RESULTS

Stones can be categorized based on anatomical position, size, medical imaging features, risk of recurrence, etiology, composition, and morphoconstitutional analysis. The first three mentioned offer a straightforward approach to stone classification, directly influencing treatment recommendations. With the routine use of CT imaging before treatment, precise details like anatomical location, stone dimensions, and Hounsfield Units can be easily determined, aiding treatment planning. In contrast, classifying stones based on risk of recurrence and etiology is more complex due to dependencies on multiple variables, including stone composition and morphology. A classification system based on morphoconstitutional analysis, which combines morphological stone appearance and chemical composition, has demonstrated its value. It allows for the rapid identification of crystalline phase principles, the detection of crystalline conversion processes, the determination of etiopathogenesis, the recognition of lithogenic processes, the assessment of crystal formation speed, related recurrence rates, and guidance for selecting appropriate treatment modalities.

CONCLUSIONS

Recognizing that no single classification system can comprehensively cover all aspects, the integration of all classification approaches is essential for tailoring urolithiasis patient-specific management.

Assessment of Hounsfield Units and Factors Associated with Fragmentation of Renal Stones by Extracorporeal Shock Wave Lithotripsy: A Computerized Tomography Study

The success rate of extracorporeal shock wave lithotripsy (ESWL) is influenced by various factors, including stone density, and is determined through computed tomography scans in terms of Hounsfield units (HU).

MATERIALS AND METHODS

This retrospective single-center study was conducted in the King Fahad Hospital. Sixty-seven adult patients with renal and ureteric stones were selected randomly and enrolled in the study. Their ages ranged from 20 to 69 years. The patients were examined with non-contrast enhancement (NCCT) to assess the HU of their stones and were consequently treated with ESWL.

RESULTS

Of the 67 patients, 37.3% had stones that were completely fragmented, while 62.7% had stones that were partially fragmented. The HU, location of the stone, multiplicity of the stone, and patient age were found to be significant factors contributing to stone fragility (p-values < 0.05). The HU data were found to have a positive significant linear correlation with serum calcium (r = 0.28, p-value = 0.036), while serum acid had a negative correlation (r = -0.55, p-value < 0.001). Thus, the probability of calcium-containing stone formation increases with increased HU. In contrast, uric acid stone formation likely develops with decreasing HU with serum uric acid. Renal stones in patients with diabetes mellitus and hypertension were not completely fragmented compared to those without clinical history.

CONCLUSIONS

Mean HU, location of the stone, laterality, stone status, and the number of ESWL sessions are the most significant factors affecting stone fragility. CT attenuation values can predict the composition of stones from serum calcium and uric acid examinations. Hypertension and diabetes mellitus are risk factors for renal stone fragmentation.