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Phantoms are important tools for image quality control and medical training. Many phantom materials have been proposed for ultrasound; most of them use water as the solvent, but these materials have disadvantages such as dehydration and low temporal stability if not properly stored. To overcome these difficulties, copolymer-in-oil gel was proposed as an inert and stable material; however, speed of sound for these materials is still lower than what is described for most biological tissues. Here, we propose the glycerol dispersion in oil-based gels to modify the acoustic and elastic properties of copolymer-in-oil phantoms. We manufactured copolymer-in-oil gels using styrene-ethylene/butylene-styrene (SEBS) in concentrations 8%-15%. We used 2 types of mineral oils with different viscosities. Glycerol was added in a volume fraction 0%-30% of the total amount of liquid. The acoustic (i.e., speed of sound, attenuation and backscattering) and the mechanical (i.e., density and Young's modulus) properties of the samples were within the range of values observed for soft tissues. The acoustic parameters of the samples were dependent on oil viscosity and glycerol concentration. The speed of sound ranged 1423 m/s - 1502 m/s, while the acoustic attenuation and the ultrasonic backscattering increased by adding glycerol. The density and the Young's moduli were less affected by the presence of glycerol. We conclude that glycerol can be used to control the acoustic parameters of copolymer-in-oil gels. Additionally, it opens the possibility of incorporating other oil-insoluble substances to control further properties of the phantom. [ABSTRACT FROM AUTHOR]

Objective To externally validate head and neck cancer (HNC) photon-derived normal tissue complication probability (NTCP) models in patients treated with proton beam therapy (PBT). Methods This prospective cohort consisted of HNC patients treated with PBT at a single institution. NTCP models were selected based on the availability of data for validation and evaluated by using the leave-one-out cross-validated area under the curve (AUC) for the receiver operating characteristics curve. Results 192 patients were included. The most prevalent tumor site was oropharynx ( n = 86, 45%), followed by sinonasal ( n = 28), nasopharyngeal ( n = 27) or parotid ( n = 27) tumors. Apart from the prediction of acute mucositis (reduction of AUC of 0.17), the models overall performed well. The validation (PBT) AUC and the published AUC were respectively 0.90 versus 0.88 for feeding tube 6 months PBT; 0.70 versus 0.80 for physician-rated dysphagia 6 months after PBT; 0.70 versus 0.68 for dry mouth 6 months after PBT; and 0.73 versus 0.85 for hypothyroidism 12 months after PBT. Conclusion Although a drop in NTCP model performance was expected for PBT patients, the models showed robustness and remained valid. Further work is warranted, but these results support the validity of the model-based approach for selecting treatment for patients with HNC. [ABSTRACT FROM AUTHOR]

In this article, a non-linear dual-phase-lag (DPL) bio-heat transfer model based on temperature dependent metabolic heat generation rate is derived to analyze the heat transfer phenomena in living tissues during thermal ablation treatment. The numerical solution of the present non-linear problem has been done by finite element Runge-Kutta (4,5) method which combines the essence of Runge-Kutta (4,5) method together with finite difference scheme. Our study demonstrates that at the thermal ablation position temperature predicted by non-linear and linear DPL models show significant differences. A comparison has been made among non-linear DPL, thermal wave and Pennes model and it has been found that non-linear DPL and thermal wave bio-heat model show almost same nature whereas non-linear Pennes model shows significantly different temperature profile at the initial stage of thermal ablation treatment. The effect of Fourier number and Vernotte number (relaxation Fourier number) on temperature profile in presence and absence of externally applied heat source has been studied in detail and it has been observed that the presence of externally applied heat source term highly affects the efficiency of thermal treatment method. [ABSTRACT FROM AUTHOR]

Mechanical characterization of brain tissue at high loading velocities is crucial for modeling Traumatic Brain Injury (TBI). During severe impact conditions, brain tissue experiences compression, tension and shear. Limited experimental data is available for brain tissue in extension at dynamic strain rates. In this research, a High Rate Tension Device (HRTD) was developed to obtain dynamic properties of brain tissue in extension at strain rates of ≤90/s. In vitro tensile tests were performed to obtain properties of brain tissue at strain rates of 30, 60 and 90/s up to 30% strain. The brain tissue showed a stiffer response with increasing strain rates, showing that hyperelastic models are not adequate. Specifically, the tensile engineering stress at 30% strain was 3.1±0.49kPa, 4.3±0.86kPa, 6.5±0.76kPa (mean±SD) at strain rates of 30, 60 and 90/s, respectively. Force relaxation tests in tension were also conducted at different strain magnitudes (10–60% strain) with the average rise time of 24ms, which were used to derive time dependent parameters. One-term Ogden, Fung and Gent models were used to obtain material parameters from the experimental data. Numerical simulations were performed using a one-term Ogden model to analyze hyperelastic behavior of brain tissue up to 30% strain. The material parameters obtained in this study will help to develop biofidelic human brain finite element models, which can subsequently be used to predict brain injuries under impact conditions and as a reconstruction and simulation tool for forensic investigations. [ABSTRACT FROM AUTHOR]

Here we investigate the basic characteristics of the tissue-equivalent phantom thermoluminescence slab dosimeter with synthetic resin type 1 (TEP-TLSD/SR1), a two-dimensional TLD based on TL phosphor Li3B7012:Cu developed by the Urushiyama Research Group. Li3B7O12:Cu has a single glow peak at 120 °C at a heating rate of 0.317 °C s−1. The dose response is linear between 0.1 and 10 Gy. The phosphor, when combined with a synthetic resin, can be molded into 200 mm × 200 mm × 2.5 mm slabs. The system has a Charge Coupled Device (CCD) dependent spatial resolution (pixel pitch) of 640 μm and a pixel response standard deviation of 1.33%. Using simple pixel-based noise compensation, we were able to improve the signal-to-noise ratio (SNR) in the final image. In tests as a TEP, this system gives off axis ratio and percentage dose depth results highly correlated with those of an ion chamber suspended in a water phantom. The TEP-TLSD/SR1 produces similar images to Gafchromic film for X-ray imaging. This TEP-TLSD/SR1 is not only larger than the prototype, but also has a better SNR and improved usability. With further improvements in tissue equivalence, we foresee a system where a TEP and dosimeter are combined into a three-dimensional dosimeter. [ABSTRACT FROM AUTHOR]

Abstract: Selection of reconstruction parameters has an effect on the image quantification in PET, with an additional contribution from a scanner-specific attenuation correction method. For achieving comparable results in inter- and intra-center comparisons, any existing quantitative differences should be identified and compensated for. In this study, a comparison between PET, PET/CT and PET/MR is performed by using an anatomical brain phantom, to identify and measure the amount of bias caused due to differences in reconstruction and attenuation correction methods especially in PET/MR. Differences were estimated by using visual, qualitative and quantitative analysis. The qualitative analysis consisted of a line profile analysis for measuring the reproduction of anatomical structures and the contribution of the amount of iterations to image contrast. The quantitative analysis consisted of measurement and comparison of 10 anatomical VOIs, where the HRRT was considered as the reference. All scanners reproduced the main anatomical structures of the phantom adequately, although the image contrast on the PET/MR was inferior when using a default clinical brain protocol. Image contrast was improved by increasing the amount of iterations from 2 to 5 while using 33 subsets. Furthermore, a PET/MR-specific bias was detected, which resulted in underestimation of the activity values in anatomical structures closest to the skull, due to the MR-derived attenuation map that ignores the bone. Thus, further improvements for the PET/MR reconstruction and attenuation correction could be achieved by optimization of RAMLA-specific reconstruction parameters and implementation of bone to the attenuation template. [Copyright &y& Elsevier]

Abstract: The aim of this study is to characterize and model the damage process in the anterior rectus abdominal aponeurosis (anterior rectus sheath) undergoing finite deformations. The resistance of the anterolateral abdominal aponeuroses is important when planning the surgical repair of incisional hernias, among other medical procedures. Previous experiments in prolapsed vaginal tissue revealed that a softening process occurs before tissue rupture. This nonlinear damage behaviour requires a continuum damage theory commonly used to describe the softening behaviour of soft tissues under large deformations. The structural model presented here was built within the framework of non-linear continuum mechanics. Tissue damage was simulated considering different damage behaviours for the matrix and the collagen fibres. The model parameters were fit to the experimental data obtained from anterior rectus sheath samples undergoing finite deformations in uniaxial tension tests. The tests were carried out with samples cut along the direction of the collagen fibres, and transversal to the fibres. Longitudinal and transverse mechanical properties of human anterior rectus sheath are significantly different. The damage model was able to predict the stress–strain behaviour and the damage process accurately. The error estimations pointed to an excellent agreement between experimental results and model fittings. For all the fitted data, the normalized RMS error presented very low values and the coefficient of determination was close to 1. The present work constitutes the first attempt (as far as the authors know) to present a damage model for the human rectus sheath. [Copyright &y& Elsevier]

Abstract: Edwardsiella tarda is a severe aquaculture pathogen that can infect many fish species and cause a systematic disease called edwardsiellosis, which can lead to high mortality under certain conditions. Currently, most vaccine candidates against edwardsiellosis are based on pathogenic E. tarda strains, which can be a concern in some cases. In this study, the vaccine potential of a natural E. tarda isolate, ATCC 15947, was examined in a Japanese flounder model. ATCC 15947 was found to be relatively avirulent to flounder but able to disseminate into and survive transiently in fish tissues following intraperitoneal (i.p.) injection. Fish vaccinated with ATCC 15947 via i.p. injection exhibited a high level of survival rate, which was increased to 100% by a booster injection. Fish vaccinated with ATCC 15947 orally in the form of alginate microspheres showed a moderate survival rate, while fish vaccinated with ATCC 15947 via the immersion route exhibited a low rate of survival. Following oral vaccination, ATCC 15947 could colonize transiently in the gut, liver, and spleen of the vaccinated fish. Both injection and oral vaccination with ATCC 15947 induced production of specific serum antibodies, the levels of which at different time points following vaccination were generally higher in fish vaccinated with ATCC 15947 via injection than in fish vaccinated with ATCC 15947 orally. Compared to control fish, fish vaccinated with ATCC 15947 showed enhanced serum bactericidal activity and significantly increased expression in genes encoding a number of immune-related factors. These results indicated that ATCC 15947 possesses good immunoprotective potential, which may be exploited in the development of E. tarda vaccines. [Copyright &y& Elsevier]

Abstract: Motivation: Image-guided percutaneous (through the skin) needle-based surgery has become part of routine clinical practice in performing procedures such as biopsies, injections and therapeutic implants. A novice physician typically performs needle interventions under the supervision of a senior physician; a slow and inherently subjective training process that lacks objective, quantitative assessment of the surgical skill and performance. Shortening the learning curve and increasing procedural consistency are important factors in assuring high-quality medical care. Methods: This paper describes a laboratory validation system, called Perk Station, for standardized training and performance measurement under different assistance techniques for needle-based surgical guidance systems. The initial goal of the Perk Station is to assess and compare different techniques: 2D image overlay, biplane laser guide, laser protractor and conventional freehand. The main focus of this manuscript is the planning and guidance software system developed on the 3D Slicer platform, a free, open source software package designed for visualization and analysis of medical image data. Results: The prototype Perk Station has been successfully developed, the associated needle insertion phantoms were built, and the graphical user interface was fully implemented. The system was inaugurated in undergraduate teaching and a wide array of outreach activities. Initial results, experiences, ongoing activities and future plans are reported. [Copyright &y& Elsevier]

Abstract: Contrast-enhanced ultrasound (CEUS) is a promising clinical tool capable of noninvasively quantifying flow and relative vascular volume within the microcirculation. Quantification can be performed by recording the replenishment intensity time course of the imaging plane after the local disruption of agent during a constant infusion. Traditional analyses of the time-intensity curves have relied on mathematical functions (e.g., mono-exponential) that fail to consider the underlying physical principles of the flow system and the influence of the measurement device. In reality, the time-intensity curve reflects the hemodynamics and morphology of the vascular system being measured, the ultrasound field distribution and microbubble properties. We introduce a general analytic disruption replenishment model that attempts to account for these parameters and compare its performance to the established model in a flow phantom. Specifically, the proposed model incorporates the hemodynamic properties of the flow system (velocity distribution and vascular cross section); includes the elevation and axial plane pressure distributions; and accounts for the distinct high and low mechanical index (MI) disruption and detection boundaries. In addition, we demonstrated the importance of the ultrasound beam profile for accurate velocity quantification. It was shown that velocity estimates vary by up to 56% if the depth-dependent elevation thickness is not properly accounted for. Compared with the currently accepted mono-exponential model, the presented formalism was shown to be more robust in the presence of simulated motion artifacts and demonstrated better agreement in both the quality of the fit and estimation of velocity (∼3 to 10% vs. 90% error) for the same flow and acoustic conditions. (E-mail: hudsonjm@gmail.com) [Copyright &y& Elsevier]

Abstract: Thermal imaging measurements using ultrasound phase contrast have been performed in tissue phantoms heated with a focused ultrasound source. Back projection and reflex transmission imaging principles were used to detect sound speed–induced changes in the phase caused by an increase in the temperature. The temperature was determined from an empirical relationship for the temperature dependence on sound speed. The phase contrast was determined from changes in the sound field measured with a hydrophone scan conducted before and during applied heating. The lengthy scanning routine used to mimic a large two-dimensional array required a steady-state temperature distribution within the phantom. The temperature distribution in the phantom was validated with magnetic resonance (MR) thermal imaging measurements. The peak temperature was found to agree within 1°C with MR, and good agreement was found between the temperature profiles. The spatial resolution was 0.3×0.3×0.3mm, comparing favorably with the 0.625×0.625×1.5-mm MR spatial resolution. (E-mail: cfarny@bwh.harvard.edu) [Copyright &y& Elsevier]

Abstract: This paper deals with the derivation of macroscopic equations from the underlying kinetic model delivered by the kinetic theory of active particles with discrete microscopic states. Hyperbolic models for local density and mean velocity are obtained with the aim at adding further knowledge to mathematical methods for modelling living matter. [Copyright &y& Elsevier]

Abstract: The propagation of electric activity inside a realistically-shaped, thick-walled model of the atria was studied. The membrane kinetics was based on the formulations of Courtemanche, Ramirez and Nattel. In spite of the assumed uniformity of all kinetics parameters, diffusion parameters, the activation recovery intervals revealed values in a range of about 20 ms, having a clearly distinct spatial distribution, with higher values close to the site of activation and lower ones at sites where activation ends. This paper presents an analysis of this phenomenon based on similar observations made on propagation along the classic models of cable and disk, as well as along the surface of a spherical shell and a diabolo-shaped shell. Propagation in the latter three geometries is treated under axial-symmetric conditions, for which dedicated analytical expressions of the diffusion term are described. The results indicate that the major effects can be directly attributed to a step discontinuity in the conductivity of the medium surrounding the locations of initial and final depolarization. Overall geometry of the myocardial wall determines the smooth distribution of activation recovery intervals in the medium, showing local maxima around the points of initiation and local minima at locations where depolarization ends. The points are determined by the location of the stimulation sites involved and overall tissue geometry. [Copyright &y& Elsevier]

Abstract: It is well-known that biological systems have the capacity to change their inner structure and shape for an optimized load transfer. This paper deals with the development of a multiphase model to describe the growth and remodeling phenomenon in biological systems in order to learn more about the biological optimization mechanisms. A continuum triphasic model (i.e., a solid having interstitial space filled with water containing nutrients) based on the multiphase Theory of Porous Media (TPM) is proposed to provide a thermodynamically consistent description of the growth and remodeling phenomenon. The constitutive modeling of stress–strain- or nutrient-driven growth and remodeling phenomena is discussed. Finally, the influence of different driving mechanisms for growth is demonstrated by three illustrative exemplary problems. [Copyright &y& Elsevier]

Abstract: Monte Carlo (MC) based simulations of photon transport in living tissues have become the “gold standard” technique in biomedical optics. Three-dimensional (3D) voxel-based images are the natural way to represent human (and animal) tissues. It is generally believed that the combination of 3D images and MC based algorithms allows one to produce the most realistic models of photon propagation. In the present work, it is shown that this approach may lead to large errors in the MC data due to the “roughness” of the geometrical boundaries generated by the presence of the voxels. In particular, the computed intensity of the light detected on the tissue surface of a simple cubic tissue phantom may display errors from −80% to 120%. It is also shown that these errors depend in a complex manner on optical and geometrical parameters such as the interoptode distance, scattering coefficient, refractive index, etc. and on the degree of voxelization (“roughness”) of the boundaries. It is concluded that if one wants to perform reliable 3D Monte Carlo simulations on complex geometries, such as human brain, skin or trabecular bone, it is necessary to introduce boundary meshing techniques or other equivalent procedures in the MC code to eliminate the deleterious effect of voxelization. [Copyright &y& Elsevier]

Abstract: The point collocation-based method of finite spheres (PCMFS) was introduced as a meshfree technique for real time simulation of surgical processes. While real time graphical rendering requires an update rate of about 30Hz, a much higher update rate of 1kHz is necessary for smooth haptic (touch) feedback. The requirement of real time performance is crucial to these simulations and is highly demanding in terms of computational efficiency. In this paper we extend the PCMFS technique to tissue deformations that are geometrically nonlinear. The technique is based on a novel combination of multiresolution approach coupled with a fast reanalysis scheme in which the response predicted by an underlying linear PCMFS model is enhanced in the local neighborhood of the surgical tool-tip by a nonlinear model. We present performance comparisons of PCMFS with traditional finite element models. [Copyright &y& Elsevier]

Abstract: Tissue engineering utilizes porous biomaterial scaffolds to deliver biological factors that accelerate tissue healing. These two functions require scaffolds be designed for mechanical loading and mass transport. The purpose of this paper was to apply both ad hoc and topology optimization homogenization based design approaches to create scaffold architectures, and to determine how these architectures compare to theoretical bounds on effective stiffness. Open cell scaffold architectures demonstrated a wide range of permeability, but were all below isotropic effective stiffness bounds. Wavy fiber architectures provide a means to approach the lower bounds. Using image-based techniques, designed architectures may be incorporated in anatomic shapes. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to develop a cone-shape phantom for multi-voxel magnetic resonance spectroscopy (MRS) and to evaluate MR spectra using the cone-shape phantom we developed in this study. A cone-shape MRS phantom was developed with a combination of cone-shape vials. The cylindrical main body was made of acrylic resin and the cone-shape vials were fabricated from poly-ethylene cones. Each cone of the phantom was filled with various metabolite materials. 1.5T GE and 3T Philips systems were used for the single voxel spectroscopy (SVS) as well as for the multi-voxel spectroscopy (MVS). Identification and quantification of the metabolite materials in the cone-shape phantom were done by the SAGE post-program. The MR images and spectra of the cone-shape phantom were obtained from the assigned slice position. The high order shimming control provided enhanced resolution in the SVS and MVS. The area and amplitude were proportional to the metabolite volume in the voxel. The present study demonstrated that the cone-shape phantom was useful for the metabolite quantification. Thus, we propose that the cone-shape phantom can be used for the evaluation of quality control of the MR spectra obtained from SVS and MVS. [Copyright &y& Elsevier]

Abstract—: We introduce a method for measuring the speed of sound dispersion. It combines a short pulse transmission followed by a long burst comprised of two frequencies, one being double that of the other. The method allows the determination of the speed of sound dispersion using a single transmission. To validate the method, the dispersion was first measured in plastic samples and then in in vitro soft tissues samples. The results obtained for Perspex samples are in excellent agreement with values reported in the literature. The dispersion index in soft tissues ranged for a bovine heart from 0.63 ± 0.24 (m/s·MHz) at 1.5 MHz to 0.27 ± 0.05 (m/s·MHz) at 4.5 MHz and for a turkey breast from 1.3 ± 0.28 (m/s·MHz) at 1.75 MHz to 0.73 ± 0.1 (m/s·MHz) at 3.8 MHz. The significant difference in the speed of sound dispersion index between the studied materials indicates that dispersion may be used as a new index for soft tissue characterization by ultrasound. (E-mail: haim@bm.technion.ac.il) [Copyright &y& Elsevier]

Abstract: A set of five tissue-mimicking phantoms with cylindrical inclusions were produced for assessing long-term stability of geometry and elastic properties and assessing accuracy of determination of elastic properties. The base aqueous materials were either gelatin or a mixture of agar and gelatin. Stiffness was controlled by selection of the volume percent consisting of microscopic safflower oil droplets. Cylinder diameters remained unchanged within 1% or 2% over many months. Strain ratios from elastograms of the phantoms were stable over many months, implying that elastic contrasts were also stable. Test samples, called production samples, for measurement of Young’s moduli were made at the time of manufacture of each phantom and were stored separately from one another. Each production sample was homogeneous and consisted of either inclusion material or background material. For all five phantoms, it was found that the elastic contrast computed using Young’s modulus values determined using the production samples accurately represented the true elastic contrasts in the corresponding phantom. This finding was established by the fact that the (true) elastic contrasts determined using samples excised from the phantoms themselves agreed with the elastic contrasts obtained using the homogeneous production samples. (E-mail: elmadsen@wisc.edu) [Copyright &y& Elsevier]

Abstract: In this paper, we present the correction of the geometric distortion measured in the clinical magnetic resonance imaging (MRI) systems reported in the preceding paper (Part I) using a 3D method based on the phantom-mapped geometric distortion data. This method allows the correction to be made on phantom images acquired without or with the vendor correction applied. With the vendor''s 2D correction applied, the method corrects for both the “residual” geometric distortion still present in the plane in which the correction method was applied (the axial plane) and the uncorrected geometric distortion along the axis normal to the plane. The evaluation of the effectiveness of the correction using this new method was carried out through analyzing the residual geometric distortion in the corrected phantom images. The results show that the new method can restore the distorted images in 3D nearly to perfection. For all the MRI systems investigated, the mean absolute deviations in the positions of the control points (along x-, y- and z-axes) measured on the corrected phantom images were all less than 0.2 mm. The maximum absolute deviations were all below ∼0.8 mm. As expected, the correction of the phantom images acquired with the vendor''s correction applied in the axial plane performed equally well. Both the geometric distortion still present in the axial plane after applying the vendor''s correction and the uncorrected distortion along the z-axis have all been “restored.” [Copyright &y& Elsevier]

Described is the Liulin-5 experiment and instrumentation, developed for investigation of the space radiation doses depth distribution in a human phantom on the Russian Segment of the International Space Station (ISS). Liulin-5 experiment is a part of the international project MATROSHKA-R on ISS. The experiment MATROSHKA-R is aimed to study the depth dose distribution at the sites of critical organs of the human body, using models of human body-anthropomorphic and spherical tissue-equivalent phantoms. The aim of Liulin-5 experiment is long term (4–5 years) investigation of the radiation environment dynamics inside the spherical tissue-equivalent phantom, mounted in different places of the Russian Segment of ISS. Energy deposition spectra, linear energy transfer spectra, flux and dose rates for protons and the biologically-relevant heavy ion components of the galactic cosmic radiation will be measured simultaneously with near real time resolution at different depths of the phantom by a telescope of silicon detectors. Data obtained together with data from other active and passive dosimeters will be used to estimate the radiation risk to the crewmembers, verify the models of radiation environment in low Earth orbit, validate body transport model and correlate organ level dose to skin dose. Presented are the test results of the prototype unit. The spherical phantom will be flown on the ISS in 2004 year and Liulin-5 experiment is planned for 2005 year. [Copyright &y& Elsevier]

Abstract: To evaluate the accuracy of small volume estimation, both in vivo and in vitro, measurements with a three-dimensional (3D) ultrasound (US) system were carried out. A position sensor was used and the transmitting frequency was 10 MHz. Balloons with known volumes were scanned while rat kidneys were scanned in vivo and in vitro. The Archimedes’ principle was used to estimate the true volume. For balloons, the 3D US system gave very good agreement with true volumes in the volume range 0.1 to 10.0 mL (r = 0.999, n = 45, mean difference ± 2SD = 0.245 ± 0.370 mL). For rat kidneys in vivo (volume range 0.6 to 2.7 mL) the method was less accurate (r = 0.800, n = 10, mean difference ± 2SD = −0.288 ± 0.676 mL). For rat kidneys in vitro (volume range 0.3 to 2.7 mL) the results showed good agreement (r = 0.981, n = 23, mean difference ± 2SD = 0.039 ± 0.254 mL). For balloons, kidneys in vivo and in vitro, the mean percentage error was 9.3 ± 4.8%, −17.1 ± 17.4%, and 4.6 ± 11.5%, respectively. This method can estimate the volume of small phantoms and rat kidneys and opens new possibilities for volume measurements of small objects and the study of organ function in small animals. (E-mail Knut.Matre@med.uib.no) [Copyright &y& Elsevier]

An acoustic diode (AD) was constructed of two acoustic transparent membranes with good initial contact to allow the transmission of the positive pressure of lithotripter shock wave at an almost unaltered level, yet attenuate significantly its negative pressure, was fabricated. It was evaluated systematically on a Dornier HM-3 lithotripter to assess its application potential to reduce vascular injury without compromising stone fragmentation efficiency during shock-wave lithotripsy. By inserting the AD, the maximum compressive pressure, maximum tensile pressure and tensile duration of the lithotripter shock wave were formed to drop from 49.7 to 47.8 MPa, -7.5 to -7.0 MPa and 6.0 to 5.1 μs, respectively. Damage of a 0.2-mm inner diameter vessel phantom (cellulose hollow fiber) was reduced from rupture after 31 ± 11 shocks to no rupture after 100 shocks. Maximum bubble size in free-field, maximum dilation of the vessel phantom wall and bubble collapse time became smaller with the use of the AD. However, stone fragmentation showed similar results without a statistically significant difference between the case with and without the AD. All these evidences suggest that the use of an acoustic diode may be a feasible approach to reduce tissue injury without compromising stone comminution in shock-wave lithotripsy. (E-mail: ) [Copyright &y& Elsevier]