Polyvinyl Chloride Plastisol Research Articles

A Vibrometer Based on Magnetorheological Optical Resonators

This paper addresses the feasibility of an optical vibrometer that is based on the shift of the optical modes, also known as whispering gallery modes (WGMs), of a magnetorheological optical resonator. The optical resonator that is used in this study is fabricated by mixing polyvinyl chloride plastisol with magnetically polarizable particles. When a permanent magnet that is located nearby the optical resonator is moved, it induces a perturbation of the morphology of the resonator, due to the magnetostrictive effect. This change in the morphology induces a shift in the optical modes of the resonator. The shift of the optical modes can be related to the displacement of the permanent magnet. The proposed sensor concept is based on monitoring the displacement of a tiny magnet that is attached to a moving surface. The optical quality factor of the resonator used in these studies was of the order of 106. The experimental results show a sensitivity of 0.32 pm/μm and a resolution that is less than 300 nm.

PVCP-based anthropomorphic breast phantoms containing structures similar to lactiferous ducts for ultrasound imaging: A comparison with human breasts

The purpose of this work was to obtain an anthropomorphic phantom with acoustic properties similar to those of breast tissue, possessing lactiferous duct-like structures, which would be a first for this type of phantom. Breast lesions usually grow in glandular tissues or lactiferous ducts. Shape variations in these structures are detectable by using ultrasound imaging. To increase early diagnosis, it is important to develop computer-aided diagnosis (CAD) systems and improve medical training. Using tissue-like materials that mimic known internal structures can help achieve both of these goals. However, most breast ultrasound phantoms described in the literature emulate only fat tissues and lesion-like masses. In addition, commercially available phantoms claim to be realistic, but do not contain lactiferous duct structures. In this work, we collected reference images from both breasts of ten healthy female volunteers aged between 20 and 30 years using a 10 MHz linear transducer of a B-mode medical ultrasound system. Histograms of the grey scale distribution of each tissue component of interest, the grey level means, and standard deviations of the regions of interest were obtained. Phantoms were produced using polyvinyl chloride plastisol (PVCP) suspensions. The lactiferous duct-like structures were prepared using pure PVCP. Solid scatterers, such as alumina (mesh #100) and graphite powders (mesh #140) were added to the phantom matrix to mimic glandular and fat tissue, respectively. The phantom duct-like structure diameters observed on B-mode images (1.92 mm ± 0.44) were similar to real measures obtained with a micrometer (2.08 mm ± 0.23). The phantom ducts are easy to produce and are largely stable for at least one year. This phantom allows the researchers to elaborate the structure at their will and may be used in training and as a reference for development of CAD systems.

Fabrication and characterization of PVCP human breast tissue-mimicking phantom for photoacoustic imaging

Human tissue-mimicking phantoms are important for characterizing and optimizing ultrasound and photoacoustic imaging systems. We demonstrated the applicability of a polyvinyl chloride plastisol (PVCP) phantom to photoacoustic imaging studies. The acoustic properties of the fabricated PVCP phantom were measured to have a sound speed of 1370 m/s, attenuation coefficient of 0.71 dB/cm/MHz, and acoustic impedance of 1.39 Mrayl. Reduced scattering coefficients, absorption coefficient, and refractive index were obtained, as 1.31 mm-1, 0.001 mm-1, and 1.636 at 780 nm by optical measurements, respectively. Therefore, the PVCP phantom was found to be similar enough to human breast tissue in photoacoustic properties.

Time-dependent thermodynamics applied to flow of suspensions and polymer melts

Rheological behavior has been treated in terms of the energy flow by coupling it with deformation and flow of material. The method follows time-dependent thermodynamics, which is different from Prigogine’s irreversible thermodynamics. We have examined the rate of energy production with particular attention to the physical meaning of the sign of the rate. Just as the sign of energy indicates in thermodynamics, whether or not the reaction is spontaneous, the sign of the rate indicates in time-dependent thermodynamics, whether or not the reaction is stable. In the stable region, the reaction is reversible. For a change from stable region to an unstable region, there is a discontinuity. Then, there is a pseudo-stable region, where a partial reversibility may be observed. This behavior involves yielding, which leads to fracture, like that seen in a longtime creep failure of a solid material. We have examined non-Newtonian flow of polyvinyl chloride plastisol, steady-state flow of high-density polyethylene melts, and its stress growth toward steady state.

Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging

Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP’s acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be = 1.01 ± 0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated.

P.012 Spinal durotomy repair simulator for deliberate microsurgical practice: integration into a residency training module

Background: Deliberate practice is one aspect of gaining competency in surgical skills. We have previously integrated a vascular microsurgery module into our residency training curriculum, and have recently described our experience with constructing patient-specific spine models for simulating lumbar spinal durotomy repair. The goal of this project is to develop the necessary infrastructure to facilitate practice on the spine model during residency. Methods: A 3D-printed plastic lumbar spine model was created from a patient computed tomography scan. L2 was manually laminectomized, and paraspinal tissues were simulated using Polyvinyl Chloride (PVC) Plastisol. Harvested bovine pericardium was sewn into tubular form as a dural substitute. The pericardial tubes were tied at either end and attached to intravenous tubing to create a closed loop water system. Results: We are developing a video tutorial describing how to setup and use the model. Residents will be recorded while performing a 1.5 cm durotomy and repair using a surgical microscope available in our training laboratory (Drake-Hunterian Neurovascular Laboratory, London, Ontario, Canada). Residents are asked to grade the realism of the model using a questionnaire. Metrics of quality are to be determined. Conclusions: Our proposed model is a cost-effective, easy-to-prepare lumbar spinal simulator that facilitates microsurgical practice during neurosurgical residency.

Polyvinyl chloride plastisol breast phantoms for ultrasound imaging

Ultrasonic phantoms are objects that mimic some features of biological tissues, allowing the study of their interactions with ultrasound (US). In the diagnostic-imaging field, breast phantoms are an important tool for testing performance and optimizing US systems, as well as for training medical professionals. This paper describes the design and manufacture of breast lesions by using polyvinyl chloride plastisol (PVCP) as the base material. Among the materials available for this study, PVCP was shown to be stable, durable, and easy to handle. Furthermore, it is a nontoxic, nonpolluting, and low-cost material. The breast’s glandular tissue (image background) was simulated by adding graphite powder with a concentration of 1% to the base material. Mixing PVCP and graphite powder in differing concentrations allows one to simulate lesions with different echogenicity patterns (anechoic, hypoechoic, and hyperechoic). From this mixture, phantom materials were obtained with speed of sound varying from 1379.3 to 1397.9ms−1 and an attenuation coefficient having values between 0.29 and 0.94dBcm−1 for a frequency of 1MHz at 24°C. A single layer of carnauba wax was added to the lesion surface in order to evaluate its applicability for imaging. The images of the phantoms were acquired using commercial ultrasound equipment; a specialist rated the images, elaborating diagnoses representative of both benign and malignant lesions. The results indicated that it was possible to easily create a phantom by using low-cost materials, readily available in the market and stable at room temperature, as the basis of ultrasonic phantoms that reproduce the image characteristics of fatty breast tissue and typical lesions of the breast.

Biologically relevant photoacoustic imaging phantoms with tunable optical and acoustic properties.

Established medical imaging technologies such as magnetic resonance imaging and computed tomography rely on well-validated tissue-simulating phantoms for standardized testing of device image quality. The availability of high-quality phantoms for optical-acoustic diagnostics such as photoacoustic tomography (PAT) will facilitate standardization and clinical translation of these emerging approaches. Materials used in prior PAT phantoms do not provide a suitable combination of long-term stability and realistic acoustic and optical properties. Therefore, we have investigated the use of custom polyvinyl chloride plastisol (PVCP) formulations for imaging phantoms and identified a dual-plasticizer approach that provides biologically relevant ranges of relevant properties. Speed of sound and acoustic attenuation were determined over a frequency range of 4 to 9 MHz and optical absorption and scattering over a wavelength range of 400 to 1100 nm. We present characterization of several PVCP formulations, including one designed to mimic breast tissue. This material is used to construct a phantom comprised of an array of cylindrical, hemoglobin-filled inclusions for evaluation of penetration depth. Measurements with a custom near-infrared PAT imager provide quantitative and qualitative comparisons of phantom and tissue images. Results indicate that our PVCP material is uniquely suitable for PAT system image quality evaluation and may provide a practical tool for device validation and intercomparison.

Multi-layered tissue head phantoms for noninvasive optical diagnostics

Extensive research in the area of optical sensing for medical diagnostics requires development of tissue phantoms with optical properties similar to those of living human tissues. Development and improvement of in vivo optical measurement systems requires the use of stable tissue phantoms with known characteristics, which are mainly used for calibration of such systems and testing their performance over time. Optical and mechanical properties of phantoms depend on their purpose. Nevertheless, they must accurately simulate specific tissues they are supposed to mimic. Many tissues and organs including head possess a multi-layered structure, with specific optical properties of each layer. However, such a structure is not always addressed in the present-day phantoms. In this paper, we focus on the development of a plain-parallel multi-layered phantom with optical properties (reduced scattering coefficient [Formula: see text] and absorption coefficient μa) corresponding to the human head layers, such as skin, skull, and gray and white matter of the brain tissue. The phantom is intended for use in noninvasive diffuse near-infrared spectroscopy (NIRS) of human brain. Optical parameters of the fabricated phantoms are reconstructed using spectrophotometry and inverse adding-doubling calculation method. The results show that polyvinyl chloride-plastisol (PVCP) and zinc oxide ( ZnO ) nanoparticles are suitable materials for fabrication of tissue mimicking phantoms with controlled scattering properties. Good matching was found between optical properties of phantoms and the corresponding values found in the literature.

Characterization of Acoustical Properties of a Phantom for Soft Tissues (PVCP and Graphite Powder) in the Range 20-45̊C

Stability and duration of ultrasonic (US) Phantoms are still a subject of research. We present a study of acoustic and mechanical properties for polyvinyl chloride plastisol (PVCP) with graphite powder (at 2% in weight) used to construct tissue-like phantoms in the temperature range of 20-45C. PVCP is a new material in the field of US phantoms and has longer duration and stability than the conventional organic mimicking materials. Longitudinal US velocity and attenuation were measured at 1MHz by the standard transmission method. Shear velocity was obtained by 1-D transient elastography. The extreme values for each of the parameters were obtained at 20C and 45C. They are: 1501.5±0.7 m/s and 1331.8±0.3 m/s for longitudinal US velocity; 0.46±0.03dB/cm and 0.94±0.09dB/cm for attenuation; and 8.4±1.2 m/s and 1.7±0.8 m/s for Shear velocity. Specific heat measured with a calorimeter and thermal conductivity measured by the method of hot plates were, respectively, 2.65±0.51J/(kgC) and 0.091±0.013J/(s°Cm), both at 22°C. For 2% of graphite powder, the parameter ranges were compatible to biological tissue ones and therefore, the same phantom can simulate different conditions only by changing its temperature. Other graphite percentages are to be tested to simulate parameter values of pathological conditions like nodules, calcification, fibrosis, etc. The phantom did not suffer from dehydration and is easy to be built in several different geometries.

Influence of the Solution Ionic Mobility on the Impedance Response of Organic Coatings

PVC (polyvinylchloride) Plastisol films immersed in electrolyte were studied by Electrochemical Impedance Spectroscopy (EIS) and the data were fitted using one-time constant and two time constant equivalent circuits. Very often the electrical behavior of these films is better represented by the second circuit. The first time constant can be associated with the film capacitance and is independent of the immersion solution ionic mobility, whereas the second one could be related with charge separation inside the film pores and depends on cation mobility. Since the physical meaning of the two time constants is acknowledged their presence in EIS measurements should be taken into account when the results are analyzed. Electrochemical Impedance Spectroscopy (EIS) can be used to evaluate coatings. The results obtained can be interpreted with an equivalent circuit composed by a resistor (solution resistance) followed by a capacitor (coating capacitance) in parallel with a resistor (poreresistance).FrequentlytheEISresultsforanintactcoating show a second time constant in the high frequency region. Several interpretations of these results are possible, namely, water-polymer composite response, coating pore structure, charge separation occurring at the film, coating relaxation given by the water entrance, high heterogeneity of the coating and transient instability (early water uptake), interaction between adsorbed electrolyte and the polymer (dipole relaxation) and difference between the coating outer and inner parts

Combined Photoacoustic Ultrasound and Beam Deflection Signal Monitoring of Gold Nanoparticle Agglomerate Concentrations in Tissue Phantoms Using a Pulsed Nd:YAG Laser

The purpose of this paper is to show and discuss the effects of the gold nanoparticle (Au-NPs) concentration inside a tissue phantom using a combined system of photoacoustics (PA) and optical beam deflection and their applications particularly to photoacoustic imaging. It was found that the PA signal from aggregated Au nanoparticles is significantly enhanced. The stock concentration of 100 nm Au-NPs was $$3.8\times 10^{9}$$ particles/mL from which three samples with 30 %, 70 %, and 90 % concentration were prepared using polyvinyl chloride-plastisol. Each sample was then irradiated across a line scan using a 10 ns pulsed Q-switched Nd:YAG laser at a 1 Hz repetition rate and $$5~\hbox {W}\cdot \hbox {cm}^{-2}$$ so that no physical ablation was observed. The corresponding photoacoustic pressure was found to approximately cover a range between 10 kPa and 51 kPa. This corresponds to approximately 130 pJ to 315 pJ of acoustic energy radiated by Au-NPs into the tissue. The maximal efficacy of the transformation of optical energy into thermal energy was $${\sim }29~\%$$ . Time-resolved photoacoustic deflection was also used to monitor the laser-interaction process. The results clearly indicated that (i) the photoacoustic signal amplitude varies in a given sample as a result of the non-uniform concentration distribution of embedded Au-NPs; (ii) an increase of the concentration increased the signal amplitude linearly; and (iii) at higher nanoparticle concentrations, the probe deflection was found to increase due to a steeper thermoelastic gradient as a result of a higher absorption by particle agglomerates and particle size-dependent dispersions.

NEAR INFRARED LIGHT HEATING OF SOFT TISSUE PHANTOMS CONTAINING NANOPARTICLES

The objective of this paper is to investigate the effect of the addition of nanoparticles to soft tissue phantoms, aiming at the enhancement of photothermal therapy for cancer. The phantoms were made of Polyvinyl chloride-plastisol (PVC-P), with two different nanoparticles, namely, titanium dioxide nanoparticles (TiO2) and silica nanoparticles (SiO2). A phantom without nanoparticles and a phantom containing a thermal paste were also manufactured for comparison purposes. The PVC-P phantom is transparent to the near infrared laser light, whereas the addition of titanium dioxide nanoparticles modified the optical properties enhancing the local heating, as demonstrated through experiments with a laser-diode and an infrared camera.

Development and application of stable phantoms for the evaluation of photoacoustic imaging instruments.

Photoacoustic imaging combines the high contrast of optical imaging with the spatial resolution and penetration depth of ultrasound. This technique holds tremendous potential for imaging in small animals and importantly, is clinically translatable. At present, there is no accepted standard physical phantom that can be used to provide routine quality control and performance evaluation of photoacoustic imaging instruments. With the growing popularity of the technique and the advent of several commercial small animal imaging systems, it is important to develop a strategy for assessment of such instruments. Here, we developed a protocol for fabrication of physical phantoms for photoacoustic imaging from polyvinyl chloride plastisol (PVCP). Using this material, we designed and constructed a range of phantoms by tuning the optical properties of the background matrix and embedding spherical absorbing targets of the same material at different depths. We created specific designs to enable: routine quality control; the testing of robustness of photoacoustic signals as a function of background; and the evaluation of the maximum imaging depth available. Furthermore, we demonstrated that we could, for the first time, evaluate two small animal photoacoustic imaging systems with distinctly different light delivery, ultrasound imaging geometries and center frequencies, using stable physical phantoms and directly compare the results from both systems.

Ultrasonic attenuation and speed in phantoms made of polyvinyl chloride-plastisol and graphite powder

Biological phantoms are very useful for controlled experiments on biomedical ultrasound. Nevertheless they are normally made of organic materials with short time-duration. We have studied the ultrasonic properties of test-blocks made of polyvinyl chloride-plastisol (PVCP) that are very stable in time. In this work, we analyzed ultrasonic (US) attenuation and speed at 1 MHz, as a function of temperature (15–45°C) of five phantoms made with PVCP and different concentrations of graphite powder (0, 0.5, 1, 2, and 5%) using the classical transmission method. US speed diminishes almost linearly (from 1408 to 1333 m.s−1) as temperature increases. In general attenuation lied between 0.73 and 0.09 dB.cm−1, but presenting a more complex behavior. For graphite concentrations of 0.5 and 1%, attenuation was lower than for 0% and for the other two phantoms (2 and 5% concentrations) attenuation was higher. This behavior can be perhaps due to the fact that the fabrication temperature for 0.5 and 1% was 140°C and for the other was 170°C. Although the standard recipe is 170°C, we observed that smaller temperatures may add in adjusting the attenuation values and it is a very useful property to mimic different biological tissues. We are now working on multilayer phantoms of PVCP.

Fabrication Methods of Phantoms Simulating Optical and Thermal Properties

The objective of this paper is to present fabrication methods of phantoms that simulate optical and thermal properties for different human tissues. This kind of phantom is very helpful for many biomedical research applications. For instance, it may be utilized in photothermal therapy of cancer. Therefore, it is intended to simulate optical properties in NIR (near infrared) range since this kind of therapy operates at this section of the spectrum. The existence of such phantoms is quite practical and useful once they replace real tissues. It has been utilized two materials to fabricate the phantoms: polyvinyl chloride-plastisol (PVC-P) and agar gel. In order to yield the different properties of each type of tissue, it is purposed to make layers of phantoms to reach this goal.

Environmental and economical acceptance of polyvinyl chloride (PVC) coating agents

Eco-efficiency analysis was used to compare eco-effectiveness of PVC plastisol with two commercially accepted coating agents; polyacrylate (PAA) and polyurethane (PUR) both in dispersed form in water. Eco-efficiency portfolio was graphically illustrated for different scenarios of coating textile fabrics using high and low quality PVC plastisols. PVC plastisol was found as the most eco-efficient coating agent followed by polyacrylate and polyurethane resin dispersions in water. It was concluded that PVC plastisol containing non-toxic plasticizer and less than 5 ppm free vinyl chloride monomer is an eco-efficient material which, when responsibly managed from cradle to grave, provides sustainable benefits to the society.

Frequency domain photothermoacoustic signal amplitude dependence on the optical properties of water: turbid polyvinyl chloride-plastisol system

Photoacoustic (more precisely, photothermoacoustic) signals generated by the absorption of photons can be related to the incident laser fluence rate. The dependence of frequency domain photoacoustic (FD-PA) signals on the optical absorption coefficient (micro(a)) and the effective attenuation coefficient (micro(eff)) of a turbid medium [polyvinyl chloride-plastisol (PVCP)] with tissuelike optical properties was measured, and empirical relationships between these optical properties and the photoacoustic (PA) signal amplitude and the laser fluence rate were derived for the water (PVCP system with and without optical scatterers). The measured relationships between these sample optical properties and the PA signal amplitude were found to be linear, consistent with FD-PA theory: micro(a)=a(A/Phi)-b and micro(eff)=c(A/Phi)+d, where Phi is the laser fluence, A is the FD-PA amplitude, and a, ...,d are empirical coefficients determined from the experiment using linear frequency-swept modulation and a lock-in heterodyne detection technique. This quantitative technique can easily be used to measure the optical properties of general turbid media using FD-PAs.

Preparation and characterization of magnetic PVC nanocomposites

A new method was developed in order to achieve an excellent dispersion of magnetite onto a polymer matrix. For that a ferrofluid was prepared containing nanometric size (15nm) magnetite and di-octyl phthalate (PVC plasticizer), this ferrofluid was dispersed in a polyvinyl chloride (PVC) plastisol and magnetic PVC films were made by static casting from plastisols and ferrofluids based on magnetite. Flexible films were characterized by vibration sample magnetometry, and stress-strain testing; rheometry was used to characterize the ferrofluid and the (PVC) plastisols containing ferrofluid (inverse ferrofluid). The effect of magnetite content on the magnetic and mechanical properties of the films was studied and showed an increase on magnetization values with magnetic loading and a variation in the stress-strain with magnetic loading as function of magnetic load content. It was found that the inverse ferrofluid showed a Bingham fluid behavior.

Normal stresses in flow of polyvinyl chloride plastisols

AbstractIn the steady state flow of many liquids, such as polymer solutions and melts, the first normal stress difference, N1 = σ11 − σ22, is positive. However, with liquid crystal systems and some colloidal suspensions, negative values of N1 were reported in literature. In our past work with a commercial polyvinyl chloride plastisol, negative values were observed. During the steady state flow, the plastisol undergoes stress‐induced phase separation into an immobilized layer and a mobile phase. The concentration difference between the two phases gives a rise to an osmotic pressure difference, Δπ, which is countered by a normal stress, N, generated by the flow. Because N is balanced with Δπ, N cannot be observed directly. In this work, N is identified as an isotropic and N1, directional. The disturbance among rotating particles in the mobile phase produces two effects; one is an increase of pressure, which is N; the other, N1 is associated with a small volume increase, which is directed towards the opening of the rheometer. The directional expansion is caused by the shear‐stress gradient in the liquid between the rotating particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2769–2775, 2007