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a Model fixed to the SLX F2 lithotriptor using a custom made acrylic support. Note paper clip helps orientation during fluoroscopic target acquisition (up-down or Z axis). b Open-welled gel model containing pre-weighed begostones, just prior to SWL treatment
Source publication
In vitro shock wave lithotripsy (SWL) research is typically performed utilizing wet coupling lithotriptors with a mesh basket model. This model does not take into account shock wave energy attenuation through tissue. Models using dry coupling lithotriptors rely on immersion chambers and face similar limitations. Ordnance gelatin (OG) displays stren...
Context in source publication
Context 1
... thin coupling film, tap water was first applied to the coupling pad and a prepared gel containing stones and urine placed on the pad center. Gels were held in place during shock wave administration initially using kidney-shaped urine pans and masking tape, and later a custom-made (the holder was 19 cm in diameter and 3 cm in depth) acrylic device (Fig. ...
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In the case of renoureteral lithiasis, shockwave lithotripsy (ESWL) proved to be an effective and safe method with a low risk of significant clinical consequences for long term The therapeutic effect is the result of the pulse amplitude, high pressure and shock wave energy content focused on striking stones or urethral calculi. The negative pressur...
Citations
... At the same time, due to the availability of materials, ease of preparation, and ethical significance, gelatin is increasingly replacing natural biological tissues for research applications [4,5] in medical engineering, including forensic and military wound profiling and projectile damage simulation objects [6,7], medical phantom materials in imaging [8,9], tissue regeneration materials [10,11], and tissue substitutes in surgical simulations [12]. However, previous research has focused on the application of gelatin in high-speed projectile damage simulation [13]. ...
As a natural polymer, gelatin is increasingly being used as a substitute for animals or humans for the simulation and testing of surgical procedures. In the current study, the similarity verification was neglected and a 10 wt.% or 20 wt.% gelatin sample was used directly. To compare the mechanical similarities between gelatin and biological tissues, different concentrations of gelatin samples were subjected to tensile, compression, and indentation tests and compared with porcine liver tissue. The loading rate in the three tests fully considered the surgical application conditions; notably, a loading speed up to 12 mm/s was applied in the indentation testing, the tensile test was performed at a speed of 1 mm/s until fracture, and the compression tests were compressed at a rate of 0.16 mm/s and 1 mm/s. A comparison of the results shows that the mechanical behaviors of low-concentration gelatin samples involved in the study are similar to the mechanical behavior of porcine liver tissue. The results of the gelatin material were mathematically expressed by the Mooney-Rivlin model and the Prony series. The results show that the material properties of gelatin can mimic the range of mechanical characteristics of porcine liver, and gelatin can be used as a matrix to further improve the similarity between substitute materials and biological tissues.
... Due to the availability of materials, ease of preparation, and ethical significance, gelatin is increasingly replacing natural biological tissues for research applications [1]- [2] in medical engineering, including forensic and military wound profiling, projectile damage simulation [3]- [4], as medical phantom materials in imaging [5]- [6], tissue regeneration materials [7]- [8], and tissue substitutes in surgical simulations [9]; however, previous research has focused on the damage behaviour of gelatin under high-speed rigid impact. The impact velocity of a high-speed waterjet exceeds that under rigid separation, and the functional characteristics thereof are unclear. ...
Different from the rigid separation of biological tissue by scalpel, medical waterjet technology utilizes the impact kinetic energy of high-speed waterjet to instantly destroy the surface of biological tissue to achieve better clinical separation effect. Since the gelatin samples are transparent biomaterials, they were taken as the only substitute for soft tissue in experimental studies and observation in the current studies of medical waterjet separation technology, but the mechanical behavioural difference between the two has not been reported. To verify the adaptability of gelatin as a substitute of soft tissue under the impact of high-speed waterjet. Firstly, the dynamic process of impact was described through the energy balance equation. Then, based on the principle of altering a single variable, the difference of damage depth between 8 wt. %, 10 wt. %, and 12 wt. % gelatin samples and porcine liver tissue under various impact pressure, impact distance, and waterjet speed of motion (as opposed to flow velocity) was compared. The results show that the gelatin sample replicates the damage behaviour of porcine liver samples under the specific waterjet impact conditions, and the direction of the waterjet hydraulic power optimisation of the two materials is also consistent: however, due to the different sampling sites and anisotropy of porcine liver samples, the mechanical response of soft tissue under high-speed waterjet impact cannot be fully expressed by gelatin samples. The experimental results can provide support for the further study of medical waterjet separation technology.
... composition and shape), and ethical implications. Ballistic gelatin in particular has frequently been employed as a soft tissue substitute (Kwartowitz (2012); Malekzadeh et al. (2011);Mendez-Probst et al. (2010)) as it is biologically-derived and has favourable properties such as biodegradability and ease of manufacture and preparation. Moreover, its mechanical properties and response to a variety of mechanical tests have been found to be similar to those of soft tissues (Breeze et al. (2013); Kalcioglu et al. (2010)), further enhancing its suitability as a substitute. ...
This paper describes a constitutive model for ballistic gelatin at the low strain rates experienced, for example, by soft tissues during surgery. While this material is most commonly associated with high speed projectile penetration and impact investigations, it has also been used extensively as a soft tissue simulant in validation studies for surgical technologies (e.g. surgical simulation and guidance systems), for which loading speeds and the corresponding mechanical response of the material are quite different. We conducted mechanical compression experiments on gelatin specimens at strain rates spanning two orders of magnitude (~0.001-0.1s(-1)) and observed a nonlinear load-displacement history and strong strain rate-dependence. A compact and efficient visco-hyperelastic constitutive model was then formulated and found to fit the experimental data well. An Ogden type strain energy density function was employed for the elastic component. A single Prony exponential term was found to be adequate to capture the observed rate-dependence of the response over multiple strain rates. The model lends itself to immediate use within many commercial finite element packages.
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... Multiple residents can train numerous times on one ballistic gelatin bench model, similar to other low-fidelity simulator10 . Thus, this homemade bench model is low-cost and reproducible to suit any US-guided CVC training program as previously showed in another environment22 . ...
To propose a simulation-based ultrasound-guided central venous cannulation skills' training program, during residency.
This study describes the strategies for learning the ultrasound-guided central venous cannulation on low-fidelity bench models. The preparation of bench models, educational goals, processes of skill acquisition, feedback and evaluation methods were also outlined. The training program was based on key references to the subject.
It was formulated a simulation-based ultrasound-guided central venous cannulation teaching program on low-fidelity bench models.
A simulation-based inexpensive, low-stress, no-risk learning program on low-fidelity bench models was proposed to facilitate acquisition of ultrasound-guided central venous cannulation skills by residents-in-training before exposure to the living patient.
Background:
Minimally invasive techniques for treatment of urinary stones requires expertise, experience and endoscopic skills. Simulators provide a low-stress and low-risk environment while providing a realistic set-up and training opportunities.
Aim:
To report the publication trend of 'simulation in urolithiasis' over the last 26 years.
Methods:
Research of all published papers on "Simulation in Urolithiasis" was performed through PubMed database over the last 26 years, from January 1997 to December 2022. Papers were labelled and divided in three subgroups: (1) Training papers; (2) Clinical simulation application or surgical procedures; and (3) Diagnostic radiology simulation. Each subgroup was then divided into two 13-year time periods to compare and identify the contrast of different decades: period-1 (1997-2009) and period-2 (2010-2022).
Results:
A total of 168 articles published on the application of simulation in urolithiasis over the last 26 years (training: n = 94, surgical procedures: n = 66, and radiology: n = 8). The overall number of papers published in simulation in urolithiasis was 35 in Period-1 and 129 in Period-2, an increase of +269% (P = 0.0002). Each subgroup shows a growing trend of publications from Period-1 to Period-2: training papers +279% (P = 0.001), surgical simulations +264% (P = 0.0180) and radiological simulations +200% (P = 0.2105).
Conclusion:
In the last decades there has been a step up of papers regarding training protocols with the aid of various simulation devices, with simulators now a part of training programs. With the development of 3D-printed and high-fidelity models, simulation for surgical procedure planning and patients counseling is also a growing field and this trend will continue to rise in the next few years.
A comprehensive, direct, and clear evaluation system is fundamental to promoting the clinical development of medical waterjet technology. According to the requirements of medical waterjet safety and work efficiency, combined with the uncertain factors of clinical operation mode, a multi-factor coupling evaluation system with splash range, bleeding volume, water consumption, and operation time as indicators has been proposed, and the indicators quantification method and dynamic optimization variables suitable for clinical application were analyzed. Through the micro-scale waterjet impact tests and optical observation under different impact conditions, and using the data reduction method of the dynamic deformation process of gelatin samples, the direct or indirect feature quantification methods corresponding to each evaluation index were constructed. A multi-objective optimization model of clinical indexes was established, which reveals the coupling mechanism of micro-scale waterjet power and manipulation mode on clinical indicators.
The application of medical waterjet achieves non-rigid separation of soft tissues. The separation effect is the result of the interaction between hydrodynamic and biomechanical nonlinear responses. In this study, a non-rigid cutting model of soft tissue was established based on fracture mechanics and energy conversion processes. It can clearly explain the physical reasons for the advantages of non-rigid separation: The extremely high impact speed, which is difficult to achieve through rigid separation, makes the stress and deformation of the soft tissue smaller. The non-rigid cutting model reveals the impact mechanism of waterjet impact velocity or pressure on the static separation effect. Based on the experimental observation of the physical morphology during the interaction process and the measurement of the dynamic separation rate, imaging evidences for dynamically evaluating the separation effect were proposed. The method of adjusting the separation effect including the splashing behavior of the waterjet was verified. The research results precisely link the application requirements of precision surgery with the physical form of the interactive process, establish a physical basis for expanding the advantages of non-rigid separation of soft tissue and provide guidance for the evaluation of dynamic separation effects.
Introduction
Several anatomical and clinical factors have been implicated in the failure rates of Shock Wave Lithotripsy (SWL), including the attenuating effects of bony structures. We designed an in vitro model which incorporates the lumbar spine including vertebral bodies and transverse processes along the pathway of shockwaves, to mimic the clinical scenario during SWL of upper ureteric stones. We hypothesized that the presence of bone structures in the SWL pathway significantly affects the fragmentation rate.
Materials and Methods
An ordnance gelatine (OG) model was conceptualized and created to allow a pig´s lumbar spine to be embedded within it. Artificial urinary calculi weighing 2 ± 0.1 grams (1.2 cm diameter) were prepared using Begostone plaster. The trial was divided in two arms: group 1 models had OG only and served as the control, and group 2 models had the bone embedded in the gelatine with stone wells placed above the transverse processes. Twenty-four stones per group were subjected to SWL using the Storz Modulith SLX-F2 lithotripter, using the same treatment parameters. Fragments were sieved through 2 mm and 4 mm filters, and the fragmentation coefficients (FC) were calculated. Mann-Whitney test was used to compare FC between the two groups.
Results
The mean fragmentation rate of group 1 was statistically significantly higher compared to group 2 using a 4 mm sieve (43 vs 0.62 %, p<0.001) and the 2 mm filter (18 vs 0.52 %, p<0.001).
Conclusions
The presence of bone structures dramatically reduces the fragmentation rate of phantom stones using an ordnance gelatine in vitro model. The OG model is inexpensive and simple to use to simulate clinical situations during SWL.
This paper reports on a series of indentation tests performed on ballistic gelatin (10%) and Perma-Gel. In these experiments, both gels were submitted to strain rates varying from 0.1 and 2.7 s-1 in quasi-static indentation. Two methods were used to evaluate the Young's modulus from quasi-static indentation test: the Hertz theory and the Oliver-Pharr model. The dependence of strain rate was also analyzed. Finally, dynamic indentation tests were performed on both gels at frequencies of 0.1 and 1.0 Hz to evaluate the gel's viscoelastic properties characterized by the storage modulus, the loss modulus and the phase angle.
Objective:
To assess the potential effect of simple renal cysts (SRC) on stone fragmentation during shock wave lithotripsy (SWL) in an in vitro model.
Materials and methods:
The in vitro model was constructed using 10% Ordnance Gelatin (OG). Models were created to mimic 4 clinical scenarios: model A- with an air-filled cavity (suboptimal for stone fragmentation); model B- without a cavity (normal anatomy); model C- with a 3 cm serum filled cavity (to represent a small SRC); model D- with a 4 cm serum filled cavity (to represent a larger SRC). SWL was applied to 24 standardized phantom stones (weight of 2 ± 0.1 g) in each model using a standardized protocol. Stone fragments were retrieved then dried over-night at room air temperature. Fragmentation Coefficient (FC) was calculated for each stone, for fragments <4mm and <2mm.
Results:
The OG in vitro model was robust enough for the proposed research. There was no fragmentation evident in model A as expected. The mean FC was 29.7 (±20.5) and 39.7 (±23.7) for <4mm fragments (p=0.069) and 7.6 (±4.1) and 10.6(±6.7) for <2mm fragments (p=0.047), for non-cystic and cystic models respectively. The mean FC was 29.7 (±20.5), 38.8 (±26.2) and 40.7 (±21.3) for <4mm fragments (p=0.213) and 7.6 (±4.1), 11.1 (±8) and 10.2 (±5.3) for <2mm fragments (p=0.138), for models B, C and D respectively.
Conclusion:
Our in vitro experiment confirms better stone fragmentation associated with SWL in presence of adjacent SRC.
