A thin-walled carotid vessel phantom for Doppler ultrasound flow studies (original) (raw)
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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.
Doppler Ultrasound Compatible Plastic Material for Use in Rigid Flow Models
Ultrasound in Medicine and Biology, 2008
A technique for the rapid but accurate fabrication of multiple flow phantoms with variations in vascular geometry would be desirable in the investigation of carotid atherosclerosis. This study demonstrates the feasibility and efficacy of implementing numerically controlled direct-machining of vascular geometries into Doppler ultrasound (DUS)–compatible plastic for the easy fabrication of DUS flow phantoms. Candidate plastics were tested for longitudinal speed of sound (SoS) and acoustic attenuation at the diagnostic frequency of 5 MHz. Teflon® was found to have the most appropriate SoS (1376 ± 40 m s–1 compared with 1540 m s–1 in soft tissue) and thus was selected to construct a carotid bifurcation flow model with moderate eccentric stenosis. The vessel geometry was machined directly into Teflon® using a numerically controlled milling technique. Geometric accuracy of the phantom lumen was verified using nondestructive micro-computed tomography. Although Teflon® displayed a higher attenuation coefficient than other tested materials, Doppler data acquired in the Teflon® flow model indicated that sufficient signal power was delivered throughout the depth of the vessel and provided comparable velocity profiles to that obtained in the tissue-mimicking phantom. Our results indicate that Teflon® provides the best combination of machinability and DUS compatibility, making it an appropriate choice for the fabrication of rigid DUS flow models using a direct-machining method. (E-mail: david.holdsworth@imaging.robarts.ca)
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
Natural and Engineering Sciences, 2018
A Doppler ultrasound is a noninvasive test that can be used to estimate the blood flow through the vessels. Presently, few flow phantoms are being used to be qualified for long-term utilize and storage with high physiological flow rate Doppler ultrasound. The main drawback of the two hydrogel materials items (Konjac (K) and carrageenan (C) (KC)) that it is not fit for long-term storage and easy to deteriorate. Thus, this research study focuses on the characterization and construction of a robust and elastic wall-less flow phantom with suitable acoustical properties of TMM. The mechanisms for the fabrication of a wall-less flow phantom utilizing a physically strong material such as K, C, and gelatin (bovine skin)-based TMM were explained. In addition, the clinical ultrasound (Hitachi Avius (HI)) system was used as the main instrument for data acquisition. Vessel mimicking material (VMM) with dimensions of 15.0 mm depth equal to those of human common carotid arteries (CCA) were obtained with pulsatile flow. The acoustical properties (speed of sound and attenuation were 1533±2 m/s and 0.2 dB/cm. MHz, respectively) of a new TMM were agreed with the IEC 61685 standards. Furthermore, the velocity percentages error were decreased with increase in the Doppler angle (the lowest % error (3%) it was at 53 •). The gelatin from bovine skin was a proper material to be added to KC to enhance the strength of TMM during for long-term utilize and storage of high-flow of blood mimicking Fluid (BMF). This wall-less flow phantom will be a suitable instrument for examining in-vitro research studies.
Wall-less Flow Phantom for High-Frequency Ultrasound Applications
Ultrasound in Medicine & Biology, 2014
There are currently very few test objects suitable for high-frequency ultrasound scanners that can be rapidly manufactured, have appropriate acoustic characteristics and are suitably robust. Here we describe techniques for the creation of a wall-less flow phantom using a physically robust konjac and carrageenan-based tissuemimicking material. Vessel dimensions equivalent to those of mouse and rat arteries were achieved with steady flow, with the vessel at a depth of 1.0 mm. We then employed the phantom to briefly investigate velocity errors using pulsed wave Doppler with a commercial preclinical ultrasound system. This phantom will provide a useful tool for testing preclinical ultrasound imaging systems. (
A wall-less vessel phantom for Doppler ultrasound studies
Ultrasound in Medicine & Biology, 1995
Doppler ultrasound flow measurement techniques are often validated using phantoms that simulate the vascuhture, surrounding tissue and blood. Many researchers use rubber tubing to mimic blood vessels because of the realistic acoustic impedance, robust physical properties and wide range of available sizes. However, rubber tubing has a very high acoustic attenuation, which may introduce artefacts into the Doppler measurements. We describe the construction of a wall-less vessel phantom that eliminates the highly attenuating wall and reduces impedance mismatches between the vessel lumen and tissue mimic. An agar-based tissue mimic and a blood mimic are described and their acoustic attenuation coefficients and velocities are character&d.
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&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s average elastic modulus (391 kPa), which was within the nominal range for human arteries. The vessel material&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;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.
Journal of Ultrasonography
Aim of the study: At present, there are few scatter particles used in preparing blood-mimicking fluids, such as nylon, sephadex, polystyrene microsphere, and poly(4-methystyrene). In this study, we present cholesterol as a new scatter particle for blood-mimicking fluid preparation. Materials and methods: The procedure for the preparation of the proposed blood-mimicking fluid involved the use of propylene glycol, D(+)-Glucose and distilled water to form a ternary mixture fluid, with cholesterol used as scatter particles. Polyethylene glycol was first used as part of the mixture fluid but the acoustic and physical properties were not suitable, leading to its replacement with D(+)-Glucose, which is soluble in water and has a higher density. A common carotid artery wall-less phantom was also produced to assess the flow properties. Results: The prepared blood-mimicking fluid with new scatter particles has a density of 1.067 g/cm3, viscosity of 4.1 mPa.s, speed of sound 1600 m/s, and atte...