Doppler Ultrasound Compatible Plastic Material for Use in Rigid Flow Models (original) (raw)
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A thin-walled carotid vessel phantom for Doppler ultrasound flow studies
Ultrasound in medicine & biology, 2004
A technique is discussed for producing a robust ultrasound (US)-compatible flow phantom that consists of a thin-walled silicone-elastomer vessel with a lumen of arbitrary geometry, embedded in an agar-based tissue-mimicking material (TMM). The TMM has an acoustic attenuation of 0.56 dB cm ؊1 MHz ؊1 at 5 MHz, with nearly linear frequency-dependence and acoustic velocity of 1539 ؎ 4 m s ؊1 . The vessel-mimicking material (VMM) has an acoustic attenuation of 3.5 dB cm ؊1 MHz ؊1 with linear frequency-dependence and an acoustic velocity of 1020 ؎ 20 m s ؊1 . Scattering particles, which are added to the VMM to increase echogenicity and add speckle texture, lead to higher attenuation, depending on particle concentration and frequency. The VMM is stable over time, with a Young's elastic modulus of 1.3 to 1.7 MPa for strains of up to 10%, which mimics human arteries under typical physiological conditions. The phantom is sealed to prevent TMM exposure to air or water, to avoid changes to the acoustic velocity.
Flow phantoms with anatomically realistic geometry and high acoustic compatibility with real vessels are reliable tools in vascular ultrasound studies. We present a multi-lumen diameter common carotid artery (CCA) wall-less phantom for ultrasound studies of relationship between lumen diameter and flow velocity. The phantom was constructed with 8 lumen diameters from 4.5 mm to 8.0 mm with an acoustic depth of 7.5 mm all within normal human carotid geometry. The tissue mimicking material (TMM) consists of konjac, carrageenan and gelatin as basic components mixed with other suitable components. The blood-mimicking fluid (BMF) was prepared by mixing propylene glycol, Glucose and poly 4-methystyrene scatterers in distilled water. The constructed phantom was scanned using ultrasound machine to measure flow velocities through the lumens and to test the quality of the phantom. The phantom was found to be robust and strong with a speed of sound and attenuation of 1548 0.07 m/s while the attenuation was 0.5 0.02 dB/cm at 5 MHz frequency. An inverse relationship was established between the CCA diameter with the peak systolic velocity (PSV), end diastolic velocity (EDV) and average velocity of the BMF. The relationship between carotid diameter and flow velocities can be used to estimate the degree of stenosis in the CCA for much narrowed vessels.
Flow phantoms with anatomically realistic geometry and high acoustic compatibility with real vessels are reliable tools in vascular ultrasound studies. We present a multi-lumen diameter common carotid artery (CCA) wall-less phantom for ultrasound studies of relationship between lumen diameter and flow velocity. The phantom was constructed with 8 lumen diameters from 4.5 mm to 8.0 mm with an acoustic depth of 7.5 mm all within normal human carotid geometry. The tissue mimicking material (TMM) consists of konjac, carrageenan and gelatin as basic components mixed with other suitable components. The blood-mimicking fluid (BMF) was prepared by mixing propylene glycol, Glucose and poly 4-methystyrene scatterers in distilled water. The constructed phantom was scanned using ultrasound machine to measure flow velocities through the lumens and to test the quality of the phantom. The phantom was found to be robust and strong with a speed of sound and attenuation of 1548 0.07 m/s while the attenuation was 0.5 0.02 dB/cm at 5 MHz frequency. An inverse relationship was established between the CCA diameter with the peak systolic velocity (PSV), end diastolic velocity (EDV) and average velocity of the BMF. The relationship between carotid diameter and flow velocities can be used to estimate the degree of stenosis in the CCA for much narrowed vessels.
Development of a vessel-mimicking material for use in anatomically realistic Doppler flow phantoms
Ultrasound in medicine …, 2011
Polyvinyl alcohol cryogel, (PVA-C) is presented as a vessel mimicking material for use in anatomically realistic Doppler flow phantoms. Three different batches of 10 % wt PVA-C containing (i) PVA-C alone, (ii) PVA-C with anti-bacterial agent and (iii) PVA-C with silicon carbide particles were produced, each with 1 to 6 freeze-thaw cycles. The resulting PVA-C samples were characterized acoustically (over a range 2.65 -10.5 MHz) and mechanically in order to determine the optimum mixture and preparation for mimicking the properties of healthy and diseased arteries found in vivo. This optimum mix was reached with the PVA-C with anti-bacterial agent sample, prepared after 2 freeze/thaw cycles, which achieved a speed of sound of 1538 ± 5 m s -1 and a Young's elastic modulus of 79 ± 11kPa. This material was used to make a range of anatomically-realistic flow phantoms with varying degrees of stenoses, and subsequent flow experiments revealed that higher degrees of stenoses and higher velocities could be achieved without phantom rupturing compared to a phantom containing conventional wall-less vessels.
Design of anthropomorphic flow phantoms based on rapid prototyping of compliant vessel geometries
2013
Anatomically realistic flow phantoms are essential experimental tools for vascular ultrasound. Here we describe how these flow phantoms can be efficiently developed via a rapid prototyping (RP) framework that involves direct fabrication of compliant vessel geometries. In this framework, anthropomorphic vessel models were drafted in computer-aided design software, and they were fabricated using stereolithography (one type of RP). To produce elastic vessels, a compliant photopolymer was used for stereolithography. We fabricated a series of compliant, diseased carotid bifurcation models with eccentric stenosis (50%) and plaque ulceration (types I and III), and they were used to form thin-walled flow phantoms by coupling the vessels to an agar-based tissue-mimicking material. These phantoms were found to yield Doppler spectrograms with significant spectral broadening and color flow images with mosaic patterns, as typical of disturbed flow under stenosed and ulcerated disease conditions. Also, their wall distension behavior was found to be similar to that observed in vivo, and this corresponded with the vessel wall's average elastic modulus (391 kPa), which was within the nominal range for human arteries. The vessel material's acoustic properties were found to be sub-optimal: the estimated average acoustic speed was 1801 m/s, and the attenuation coefficient was 1.58 dB/(mm·MHz(n)) with a power-law coefficient of 0.97. Such an acoustic mismatch nevertheless did not notably affect our Doppler spectrograms and color flow image results. These findings suggest that phantoms produced from our design framework have the potential to serve as ultrasound-compatible test beds that can simulate complex flow dynamics similar to those observed in real vasculature.
Ultrasound in Medicine & Biology, 2007
Doppler ultrasound is widely used in the diagnosis and monitoring of arterial disease. Current clinical measurement systems make use of continuous and pulsed ultrasound to measure blood flow velocity; however, the uncertainty associated with these measurements is great, which has serious implications for the screening of patients for treatment. Because local blood flow dynamics depend to a great extent on the geometry of the affected vessels, there is a need to develop anatomically accurate arterial flow phantoms with which to assess the accuracy of Doppler blood flow measurements made in diseased vessels. In this paper, we describe the computer-aided design and manufacturing (CAD-CAM) techniques that we used to fabricate anatomical flow phantoms based on images acquired by time-of-flight magnetic resonance imaging (TOF-MRI). Three-dimensional CAD models of the carotid bifurcation were generated from data acquired from sequential MRI slice scans, from which solid master patterns were made by means of stereolithography. Thereafter, an investment casting procedure was used to fabricate identical flow phantoms for use in parallel experiments involving both laser and Doppler ultrasound measurement techniques. (E-mail: rablack@liv.ac.uk) © 2007 World Federation for Ultrasound in Medicine & Biology.
Journal for Vascular Ultrasound, 2013
Background and Purpose.-Ultrasound (US) plaque characterization has great potential with regard to maximizing the information traditionally gathered with spectral Doppler examination. It can directly visualize plaque and quantify better features such as surface morphology, geometry, volume, and echotexture via B-mode and the three-dimensional (3D) imaging mechanism. One of the major pitfalls of carotid imaging is the use of freehand manual manipulation. The application of angling, steering, as well as variability in the technical parameters, can increase the interobservation inconsistency. A limited number of commercial phantoms are available to teach this advanced technique but come at a high cost. We developed a home-produced phantom model to practice and teach carotid atherosclerotic disease imaging. We also investigated interobservation variability using two-dimensional (2D) characterization and 3D mechanical planimetry. This study presents a recipe to create an ultrasonic phantom that simulates a diseased carotid artery segment and how it can be used in identifying the 2D and 3D US interobservation variability. Methods.-We created fi ve tissue-like phantoms to simulate various types of diseased plaque segments. To simulate the plaque, a piece of frankfurter was cut and detailed to represent various forms of diseased plaque. Each mould contained dissimilar types of mimicked-plaque, including a softplaque, fi ssured, ulcerated, irregular surfaced, and calcifi ed segment. We used a mixture of gelatin and Metamucil to mimic a previously published soft-tissue mixture. To create a vessel, we used a powder-free, nitrile examination glove. The frankfurter was held in place inside the middle fi nger of the glove using adhesive gel and fi lled with mineral oil. Preparation included interval refrigeration of the concoction of the mould. Trained sonographers imaged the plaque using a linear small parts probe for 2D and a mechanical 3D probe for 3D US. Two neuroradiologists assessed the corresponding images and reported their fi ndings including the internal plaque contents, volume, and geometry. Analysis was performed on the inter-observation and inter-reading variability. Results.-Interobserver and interreader reliabilities were high, and plaque volume measurement variability decreased with increasing plaque volume. There was increased sensitivity and specifi city for each plaque phantom with the use of 3D versus 2D alone. Neuroradiologists reports were 96% sensitive and 97% specifi c, respectively, when they used combined 2D and 3D US. Conclusion.-We created a 2D and 3D vascular US carotid phantom. This phantom is an excellent educational tool to simulate various degrees of diseased carotid segments; moreover, it can be made easily and inexpensively and is reusable. This phantom represents the vessel anatomy and pathology extremely well. We implemented a standardized scanning protocol and created a plaque morphological worksheet to cover all plaque characterization criteria and achieve optimal imaging. Results indicated minimal interobservation and interreader variability. Additional studies are required to address the phantom's longevity and whether or not it can improve the sonographer's skills.
3D dynamic model of healthy and pathologic arteries for ultrasound technique evaluation
Medical Physics, 2008
A 3D model reproducing the biomechanical behavior of human blood vessels is presented. The model, based on a multilayer geometry composed of right generalized cylinders, enables the representation of different vessel morphologies, including bifurcations, either healthy or affected by stenoses. Using a finite element approach, blood flow is simulated by considering a dynamic displacement of the scatterers ͑erythrocytes͒, while arterial pulsation due to the hydraulic pressure is taken into account through a fluid-structure interaction based on a wall model. Each region is acoustically characterized using FIELD II software, which produces the radio frequency echo signals corresponding to echographic scans. Three acoustic physiological phantoms of carotid arteries surrounded by elastic tissue are presented to illustrate the model's capability. The first corresponds to a healthy blood vessel, the second includes a 50% stenosis, and the third represents a carotid bifurcation. Examples of M mode, B mode and color Doppler images derived from these phantoms are shown. Two examples of M-mode image segmentation and the identification of the atherosclerotic plaque boundaries on Doppler color images are reported. The model could be used as a tool for the preliminary evaluation of ultrasound signal processing and visualization techniques.
Journal of Medical Ultrasound, 2018
Since the 1960s, tissue-mimicking material (TMM) has been utilized for the preparation and characterization of ultrasound imaging. Wall-less flow phantoms are as well utilized to examine the performance of ultrasound device for practicing of sonographers. The achievement of equivalent TMM is a necessary to process for a quality monitor of Doppler ultrasound diagnostic instrument. It is essential that chemical items utilized in the TMM are prepared in a planned method to be nearly equal to the acoustical properties of real tissue with attenuation and speed of sound of 1540 ± 30 m/s, <0.5 dB/cm at MHz, respectively. [1-3] Flow phantom is a model of TMM with a vessel-mimicking material (VMM) surrounding it during pumping of blood-mimicking fluid (BMF). [4-7] The acoustical features of the different ingredients of the flow phantom correspond to the acoustical features of human blood, tissue, and vessel. [8] As required and identified by the International Electrotechnical Commission (IEC 61685 standard 1999), [10] it can be applied for a proper BMF and TMM. [10-12] However, when the tubing materials are lacking acoustic properties, the deformation of the Doppler spectrum will lead to the refraction at the vessel wall [13,14] and attenuation. [15,16] Regarding acoustical and physical properties, the most proper tubing materials are known as C-flex™. The acoustic speed in the tube should be identical (the same ranges to the TMM) to prevent refraction artifacts. [17] The speed of sound in TMM is usually 1540 m/s. [17-20] The refraction artifacts can be noticed when using tubes with a high velocity of sound. [21] Several researchers [17,19,22-30] have measured and examined both the acoustic speed and attenuation of the tube (TMM) by pulse echo signal technique. Through comprehensive literature review, the studies measured and calculated the speed of sound and attenuation through the solid (TMM) samples via measuring the time of flight (ToF) or time shift, t, of the signal
Design of anthropomorphic atherosclerotic carotid artery flow phantoms for ultrasound images
2015 Computing in Cardiology Conference (CinC), 2015
Carotid artery phantoms (CaPs) can be used as test objects to explore novel ways of enhancing the ultrasound based carotid atherosclerosis diagnosis. To achieve this goal CaPs should be anatomically realistic both in terms of geometry, acoustic and physical properties, and should allow to reproduce different pathological conditions. We propose a framework for designing CaPs of healthy and diseased arteries. To verify the framework effectiveness we constructed three CaPs: healthy, with a hard/soft plaque causing a 30%/65% vessel narrowing. Then we acquired CaPs B-mode images and performed their geometric characterization and echogenicity analysis demonstrating the framework effectiveness at realizing anthropomorphic CaPs at low cost, easily reproducing different atherosclerotic conditions.