Fabrication Of Phantoms Research Articles

Polyacrylamide-based phantoms of human skin for hyperspectral fluorescence imaging and spectroscopy

Based on the combined use of polymerisable polyacrylamide, collagen and an aqueous solution of Flavin adenine dinucleotide (FAD), we have developed a new technique for fabrication of composite phantoms mimicking fluorescence properties of human skin. A comparative analysis of the absorption and scattering coefficients, refractive indices, as well as fluorescence spectra of phantoms with different concentrations of FAD measured with the combined use of a CCD spectrometer and a hyperspectral camera is presented. To obtain values of scattering coefficients close to those for human skin, zinc oxide (ZnO) nanoparticles are added to the polyacrylamide polymer structure. Variations both in the shape of the spectrum and in the intensity of the fluorescence signal in the phantoms are provided by the changes in the volume fraction of FAD and collagen. It is shown that the model fluorescence spectra are in good agreement with the results of direct human skin measurements in vivo.

Structural, Mechanical, and Dielectric Properties of Polydimethylsiloxane and Silicone Elastomer for the Fabrication of Clinical-Grade Kidney Phantom

This study aimed to introduce an alternative, inexpensive, and straightforward polymer with specific mechanical and dielectric properties suitable for the fabrication of a clinical-grade kidney phantom. Two polymer-based phantom materials, polydimethylsiloxane (PDMS) and silicone elastomer (SE), were investigated for their capability to meet the requirements. The concentration ratios of base to curing agent (B/C) were 9.5/1.5, 19/3, 10/1, 20/2, 10.5/0.5, and 21/1 for PDMS and 4.5/5.5, 10/12, 5/5, 11/11, 5.5/4.5, and 12/10 for SE. All samples were mixed, degassed, and poured into Petri dishes and small beakers. The polymer was cured under room temperature for 2 h and then demolded from the hard mold. The air bubbles produced were removed using a vacuum desiccator for 30 min. All samples underwent mechanical testing (tensile strength and elastic modulus), and their dielectric properties were measured using a dielectric probe kit equipped with 85071E materials measurement software. The radiation attenuation properties were also measured using PhyX-Zetra for PDMS phantoms with the chemical formula C2H6OSi. Small changes in base and cross-linker play an essential role in modifying the elastic modulus and tensile strength. The effective atomic number of PDMS showed a similar pattern with human kidney tissue at the intermediate energy level of 1.50 × 10−1 to 1 MeV. Therefore, PDMS can potentially be used to mimic the human kidney in terms of tensile strength, flexibility, the acceptable real part of the complex dielectric constant ε′r, and conductivity, which allows it to be used as a stable kidney phantom for medical imaging purposes.

Design and fabrication of a thoracic phantom for radiation dose verification in mega-voltage X-ray beam

To assess the radiological properties of racemosa wooden dust (RWD) and Poly (methyl methacrylate) (PMMA) for design and fabrication of a thoracic phantom for radiation dose verification in mega-voltage X-ray beam. The computed tomography images of RWD and PMMA were used to determine the radiological properties viz., Hounsfield units (HUs), relative electron density (RED) and mass density (MD). The estimated HUs, RED and MD were −828.2 ± 11.9, 0.172 ± 0.012, 0.150 ± 0.012 g/cc and 108.5 ± 7.3, 1.104 ± 0.004, 1.088 ± 0.005 g/cc for RWD and PMMA, respectively. The radiological properties of RWD and PMMA were in congruence with the value detailed in literature for lung tissue and muscle tissue of human body. Therefore, a phantom was design and fabricated using the combination of RWD and PMMA for radiation dose verification prior to radiation delivery to the cancer patients. The average deviation between dose computation engine and Ion-chamber estimations were within the stipulated tolerance (±3%). Thus, it was culminated that RWD and PMMA can be utilized for design and fabrication of phantom, which vindicates precise information about the quality assurance program for thoracic cancer patient treated using mega-voltage X-ray beam.

Bimodal microwave and ultrasound phantoms for non-invasive clinical imaging

A precise and thorough methodology is presented for the design and fabrication of bimodal phantoms to be used in medical microwave and ultrasound applications. Dielectric and acoustic properties of human soft tissues were simultaneously mimicked. The phantoms were fabricated using polyvinyl alcohol cryogel (PVA-C) as gelling agent at a 10% concentration. Sucrose was employed to control the dielectric properties in the microwave spectrum, whereas cellulose was used as acoustic scatterer for ultrasound. For the dielectric properties at microwaves, a mathematical model was extracted to calculate the complex permittivity of the desired mimicked tissues in the frequency range from 500 MHz to 20 GHz. This model, dependent on frequency and sucrose concentration, was in good agreement with the reference Cole–Cole model. Regarding the acoustic properties, the speed of sound and attenuation coefficient were employed for validation. In both cases, the experimental data were consistent with the corresponding theoretical values for soft tissues. The characterization of these PVA-C phantoms demonstrated a significant performance for simultaneous microwave and ultrasound operation. In conclusion, PVA-C has been validated as gelling agent for the fabrication of complex multimodal phantoms that mimic soft tissues providing a unique tool to be used in a range of clinical applications.

Fabrication of Human Body Phantom for Body Centric Communication Systems at 2.4 GHz

This research is intending to investigate the human skin phantom’s dielectric constant. The phantom will be used to test the electromagnetic compatibility later on since it can be harmful if it is directly tested on real human body. The human body phantom is made to have similar property as a skin tissue, at the operating frequency of 2.4 GHz. A methodology of the process is discussed. The phantom is fabricated, tested and measured. A fabricated phantom with the desired permittivity of er and conductivity of σ values; are controlled by the amount of polyethylene powder and sodium chloride. The information on dielectric constant of the phantom based on measured values of er and σ will be determined. The factors in making a good phantom is discussed. A good level of agreement is observed between simulation and measurement results.

Novel Polydimethylsiloxane (PDMS) Pulsatile Vascular Tissue Phantoms for the In-Vitro Investigation of Light Tissue Interaction in Photoplethysmography.

Currently there exists little knowledge or work in phantoms for the in-vitro evaluation of photoplethysmography (PPG), and its’ relationship with vascular mechanics. Such phantoms are needed to provide robust, basic scientific knowledge, which will underpin the current efforts in developing new PPG technologies for measuring or estimating blood pressure, blood flow and arterial stiffness, to name but a few. This work describes the design, fabrication and evaluation of finger tissue-simulating pulsatile phantoms with integrated custom vessels. A novel technique has been developed to produce custom polydimethylsiloxane (PDMS) vessels by a continuous dip-coating process. This process can accommodate the production of different sized vessel diameters (1400–2500 µm) and wall thicknesses (56–80 µm). These vessels were embedded into a mould with a solution of PDMS and India ink surrounding them. A pulsatile pump experimental rig was set up to test the phantoms, where flow rate (1–12 L·min−1), heart rate (40–120 bpm), and total resistance (0–100% resistance clamps) could be controlled on demand. The resulting flow profiles approximates human blood flow, and the detected contact PPG signal (red and infrared) from the phantom closely resembles the morphology of in-vivo PPG waveforms with signal-to-noise ratios of 38.16 and 40.59 dB, for the red and infrared wavelengths, respectively. The progress made by this phantom development will help in obtaining new knowledge in the behaviour of PPG’s under differing flow conditions, optical tissue properties and differing vessel stiffness.

Low-cost 3D print–based phantom fabrication to facilitate interstitial prostate brachytherapy training program

PurposeThe purpose of this study was to manufacture a realistic and inexpensive prostate phantom to support training programs for ultrasound-based interstitial prostate brachytherapy. Methods and MaterialsFive phantom material combinations were tested and evaluated for material characteristics; Ecoflex 00–30 silicone, emulsion silicone with 20% or 50% mineral oil, and regular or supersoft polyvinyl chloride (PVC). A prostate phantom which includes an anatomic simulated prostate, urethra, seminal vesicles, rectum, and normal surrounding tissue was created with 3D-printed molds using 20% emulsion silicone and regular and supersoft PVC materials based on speed of sound testing. Needle artifact retention was evaluated at weekly intervals. ResultsSpeed of sound testing demonstrated PVC to have the closest ultrasound characteristics of the materials tested to that of soft tissue. Several molds were created with 3D-printed PLA directly or cast on 3D-printed PLA with high heat resistant silicone. The prostate phantom fabrication workflow was developed, including a method to produce dummy seeds for low-dose-rate brachytherapy practice. A complete phantom may be fabricated in 1.5–2 h, and the material cost for each phantom was approximated at $23.98. ConclusionsA low-cost and reusable phantom was developed based on 3D-printed molds for casting. The proposed educational prostate phantom is an ideal cost-effective platform to develop and build confidence in fundamental brachytherapy procedural skills in addition to actual patient caseloads.

Patient-Specific Polyvinyl Alcohol Phantom Fabrication with Ultrasound and X-Ray Contrast for Brain Tumor Surgery Planning.

Phantoms are essential tools for clinical training, surgical planning and the development of novel medical devices. However, it is challenging to create anatomically accurate head phantoms with realistic brain imaging properties because standard fabrication methods are not optimized to replicate any patient-specific anatomical detail and 3D printing materials are not optimized for imaging properties. In order to test and validate a novel navigation system for use during brain tumor surgery, an anatomically accurate phantom with realistic imaging and mechanical properties was required. Therefore, a phantom was developed using real patient data as input and 3D printing of molds to fabricate a patient-specific head phantom comprising the skull, brain and tumor with both ultrasound and X-ray contrast. The phantom also had mechanical properties that allowed the phantom tissue to be manipulated in a similar manner to how human brain tissue is handled during surgery. The phantom was successfully tested during a surgical simulation in a virtual operating room.The phantom fabrication method uses commercially available materials and is easy to reproduce. The 3D printing files can be readily shared, and the technique can be adapted to encompass many different types of tumor.

Physical and mechanical properties of soy-lignin bonded Rhizophora spp. particleboard as a tissue-equivalent phantom material

Experimental binderless and adhesive-bonded particleboards were made from three different sample sizes, 0 to 103 µm, 104 to 210 µm, and 211 to 500 µm from Rhizophora spp. wood trunk at 1.0 g cm-3. The objective was to evaluate the physical and mechanical properties of the particleboards. The binderless and soy-lignin bonded particleboards were fabricated and studied based on the density, internal bonding, modulus of rupture, water absorption, and thickness swelling. Microstructure study using scanning electron microscopy (SEM) and elemental analysis by carbon hydrogen nitrogen (CHN) analyser were also performed. Particleboards with adhesives improved the internal bond strength. Smaller particle sizes also were shown to be able to improve the thickness swelling outcomes, with lower hygroscopic properties. The SEM images showed that smaller particle size allowed better bonding with adhesives and provided superior strength in the fabrication of tissue equivalent phantom material. The CHN ratio demonstrated by soy flour and lignin revealed no major difference when compared with the Rhizophora spp. samples, showing basic chemical composition of natural adhesives, which was crucial in the fabrication of tissue-mimicking phantom. The study revealed the potential of soy flour and lignin as adhesives for the fabrication of Rhizophora spp. particleboard as a tissue equivalent phantom material.

Development of Physical Breast Phantoms for X-ray Imaging Employing 3D Printing Techniques

Objective: This study aims to investigate the use of 3D printing techniques for the fabrication of physical breast phantoms, suitable for conventional and phase contrast breast imaging. Such phantoms could provide essential information for the design, development and optimization of emerging X-ray imaging modalities. Materials and Methods: Physical phantoms were constructed using two 3D printing techniques: Fused Deposition Modeling and Stereolithography. Eight materials suitable for 3D printing, including thermoplastic filaments and photopolymer resins, were investigated for the optimal representation of breast tissues, based on their attenuation and refractive characteristics. The phantoms consisted of a 3D-printed mold, which was then manually filled with paraffin wax. Additionally, a 3D complex-patterned layer and details representing abnormalities were embedded in different depths. Images of the phantoms were obtained in attenuation and phase contrast mode. Experiments were conducted using an X-ray microfocus tube with Tungsten anode set to 55kVp, combined with a photon-counting detector. The distance between source and detector was 56.5cm. The images were acquired at different object-to-detector distances starting from 5cm up to 40cm in a free space propagation set-up. Results and Conclusion: Results show that among all combinations with paraffin used as an adipose substitute, phantoms created with the Stereolithography technique and resins (especially Flex) as glandular equivalent, were found to be more appropriate for both attenuation and phase contrast imaging. The edge enhancement effect was well observed in the experimental images acquired at 35cm object-to-detector distance, indicating the potential for improved feature visualization using this set-up in phase contrast compared to attenuation mode.

Technical Note: Accurate replication of soft and bone tissues with 3D printing.

The fabrication of a realistic patient-specific skull phantom employing for the first time a new filament extrusion rate method, for the accurate replication of soft and bone tissues both in Hounsfield Units (HU) range and in texture. An in-house developed software was used for the fabrication of the phantom taking into account all the HU of a patient's Computed Tomography (CT) images, replicating the organs voxel-by-voxel without the need of a uniform three-dimensional printing pattern. Two commercially available materials were used; the polylactic acid (PLA) filament for the soft tissues, and a mixture of 50% of PLA and 50% of gravimetric powdered stone for the bone tissues. Additionally, a layer of small amounts of PLA were also extruded on the fabricated bones. The replicated anatomy of the phantom was very close to the patient's one, achieving a similar range of HU without creating any air gaps and variations on the replicated HU, which are the main artifacts observed when a standard infill density and pattern is employed. The maximum measured HU values of the replicated bone tissues were at about 900. The results indicated an accurate replication of the soft tissues HU, and a significant improvement of the bone tissue HU replication. Further investigation on materials of high density in conjunction with the filament extrusion rate method may provide custom-made realistic phantoms for diagnostic and lower energy radiation such as in superficial, orthovoltage, and electron beam radiotherapy.

Low-cost fabrication of optical tissue phantoms for use in biomedical imaging

The rapid development of new optical imaging techniques is dependent on the availability of low-cost and easily reproducible standards for technique validation. This work describes a low-cost fabrication process of an agar gel-based phantom that may accurately simulate the optical properties of different human tissues at 532 and 630nm wavelengths. It was designed to match the optical properties of the brain, bladder wall, and lung tissues. These low-cost phantoms use agar powders dissolved in water as the bulk matrix. The latter is loaded with varying amounts of India ink, and aluminium oxide Al2O3 particles for optical absorption and scattering targets. The optical properties (absorption and scattering coefficients), the primary design factor and critical parameters of these phantoms were deduced from measurements of the total attenuation coefficients (μt).It is anticipated that the constructed tissue phantoms have the potential to be used as a reference standard since it's possible to preserve the optical properties in a period exceeding two years, under ideal storage conditions.

Effect of Computed Tomography Slice Thickness on Calculated Coronary Artery Calcium Score in the Assessment of Possible Radiation Induced Cardiac Toxicity

Studies have suggested that the occurrence of radiation induced cardiac toxicity in breast cancer patients is significantly higher in women with pre-existing cardiac risk factors. Therefore, it is important to quantify the relationship between radiation induced cardiac toxicity and a measurable level of pre-existing cardiac risk such as the patient’s coronary artery calcium Agatston score. To assess the extent of coronary artery calcium present in the walls of patients’ coronary arteries before they received treatment, Agatston scores may be calculated using thoracic CT scans acquired for external beam radiotherapy planning. However, these planning CT scans can vary in slice thickness and resolution, thus complicating the calculation of calcium scores using scans with slice thicknesses other than the 3mm routinely employed for traditional Agatston scoring. The objective of this project is to quantify the effect of varying CT scan slice thickness in the calculation of coronary artery calcium scores so that a method of standardization might be developed. This is accomplished through the design, fabrication, and scanning of an anthropomorphic phantom featuring calcium inserts of varying sizes. Analysis of how the scores change with increasing slice thickness is used to construct a simple linear scaling method of standardization which corrects for varying slice thickness and the resulting partial volume distortions. A linear scaling method was successfully validated for the calculation of coronary artery calcium Agatston scores across a range of slice thicknesses increasing from 0.625 mm to 5 mm. Scaling is applied by multiplying the score by the slice thickness and dividing by 3 mm. This method is potentially applicable in any clinical or research endeavour which calls for retroactive cardiac calcium quantification. With a simple linear scaling method, external beam radiation therapy planning CT scans with slice thicknesses ranging from 0.625 mm to 5 mm can be used to calculate coronary artery calcium Agatston scores and thereby measure a patient’s level of cardiac risk before treatment.

Three-dimensional (3D) scanning using Microsoft® Kinect® Xbox 360® scanner for fabrication of 3D printed radiotherapy head phantom

Radiotherapy phantoms are essential equipment for treatment verification and quality assurance. Recently, development in 3D printing technology provides an opportunity for fabricating patient-specific radiotherapy phantom that has many potential applications in clinical and research. This study investigates the application of Microsoft Kinect® Xbox 360 scanner to model human topography for 3D printed radiotherapy phantom fabrication. The feasibility and performance of the Kinect® scanner were tested on a standard commercial head phantom. The scanned head image was then edited and adapted for 3D printing. The finding suggests that the radiotherapy phantom can potentially be developed using the Kinect® sensor, which is easier and cheaper to operate in comparison to other techniques of fabricating 3D printed radiotherapy phantom.

Multimodal 3D Printing of Phantoms to Simulate Biological Tissue

Biomedical optical imaging is playing an important role in diagnosis and treatment of various diseases. However, the accuracy and the reproducibility of an optical imaging device are greatly affected by the performance characteristics of its components, the test environment, and the operations. Therefore, it is necessary to calibrate these devices by traceable phantom standards. However, most of the currently available phantoms are homogeneous phantoms that cannot simulate multimodal and dynamic characteristics of biological tissue. Here, we show the fabrication of heterogeneous tissue-simulating phantoms using a production line integrating a spin coating module, a polyjet module, a fused deposition modeling (FDM) module, and an automatic control framework. The structural information and the optical parameters of a "digital optical phantom" are defined in a prototype file, imported to the production line, and fabricated layer-by-layer with sequential switch between different printing modalities. Technical capability of such a production line is exemplified by the automatic printing of skin-simulating phantoms that comprise the epidermis, dermis, subcutaneous tissue, and an embedded tumor.

Fabrication and Optical Characterization of Gelatin-Based Phantoms for Tissue Oximetry.

The realistic tissue mimicking gelatin-based phantoms with intralipid (4% v/v) and/or hemoglobins (oxy-, deoxyhemoglobins, and MetHb) were molded between two coverslips separated by 2-mm wires. The hemoglobin solutions were prepared by dissolving the lyophilized human hemoglobin powder (H7379, Sigma-Aldrich) in the deionized water. Sodium dithionite (85% purity, 157,953, Sigma-Aldrich) was used to reduce MetHb solution. The phantoms were imaged using a multispectral imaging device (Oxilight, Canada).To demonstrate the utility, the developed approach is applied to emulate elevated systemic MetHb content. Initial results show that elevated systemic MetHb (2.0-6.7% of total blood) does not impact the accuracy of tissue oximetry imaging. A robust method for fabrication and optical validation of biocompatible tissue-mimicking phantoms has been developed.The proposed phantom design allows combining different phantoms into multilayer (sandwich) structures, which can be used to emulate a wide range of topical and systemic conditions.

The characterization of PVA/PHY hydrogels for 3D printing fabrication of organ phantoms

Phantoms are widely used substitutes for various types of soft tissues with mechanically and anatomically matching properties. They can be used as advanced tools for training before the surgical manipulation on human organs such as the brain or liver as part of complex operation planning and preparation. We report 3D printing fabrication and characterization of hydrogel composites based on the combination of two biocompatible materials, namely, polyvinyl alcohol (PVA) and phytagel (PHY). The hydrogels were used for the fabrication of brain phantoms in a multistage procedure based around 3D printing. The main goal of this study is to demonstrate the simple, low cost and relatively fast procedure for the creation of hydrogel organ phantoms of high anatomical and mechanical fidelity made from commonly available materials. To this end, three different types of samples were produced to illustrate the flexibility of hydrogel-based 3D printing approach in mimicking the mechanical properties of human organs: brain, lung, and liver soft tissues. The mechanical response was studied using Deben MicroTest 1 kN mechanical testing device and Q800 Dynamic Mechanical Analyser in compression mode. The results reveal close matching of the dynamic non-linear mechanical response of the phantoms to those of the corresponding natural soft tissues.

Design, Fabrication, and Validation of a Polymethyl Methacrylate Head Phantom for Dosimetric Verification of Cranial Radiotherapy Treatment Plans.

Purpose:The present study aims to design and fabricate a novel, versatile, and cost-effective Polymethyl Methacrylate (PMMA) head phantom for the dosimetric pretreatment verification of radiotherapy (RT) treatment plans.Materials and Methods:The head phantom designing involves slice-wise modeling of an adult head using PMMA. The phantom has provisions to hold detectors such as ionization chambers of different sizes, Gafchromic films, gel dosimeter, and optically stimulated luminescence dosimeter. For the point dose verification purpose, 15 volumetric modulated arc therapy patient plans were selected, and doses were measured using a CC13 ionization chamber. The percentage gamma passing rate was calculated for acceptance criteria 3%/3 mm and 2%/2 mm using OmniPro I’mRT film QA software, and Gafchromic EBT3 films were used for 2D planar dose verification.Results:Treatment planning system calculated, and the measured point doses showed a percentage deviation ranged from 0.26 to 1.92. The planar dose fluence measurements, for set acceptance criteria of 3%/3 mm and 2%/2 mm, percentages of points having gamma value <1 were in the range of 99.17 ± 0.25 to 99.88 ± 0.15 and 93.16 ± 0.38 to 98.89 ± 0.23, respectively. Measured dose verification indices were within the acceptable limit.Conclusions:The dosimetric study reveals that head phantom can be used for routine pretreatment verification for the cranial RT, especially for stereotactic radiosurgery/RT as a part of patient-specific quality assurance. The presently fabricated and validated phantom is novel, versatile, and cost-effective, and many institutes can afford it.

Chemical Characteristics, Motivation and Strategies in choice of Materials used as Liver Phantom: A Literature Review.

Liver phantoms have been developed as an alternative to human tissue and have been used for different purposes. In this article, the items used for liver phantoms fabrication are mentioned same as in the previous literature reviews. Summary and characteristics of these materials are presented. The main factors that need to be available in the materials used for fabrication in computed tomography, ultrasound, magnetic resonance imaging, and nuclear medicine were analyzed. Finally, the discussion focuses on some purposes and aims of the liver phantom fabrication for use in several areas such as training, diagnoses of different diseases, and treatment planning for therapeutic strategies – for example, in selective internal radiation therapy, stereotactic body radiation therapy, laser-induced thermotherapy, radiofrequency ablation, and microwave coagulation therapy. It was found that different liver substitutes can be developed to fulfill the different requirements.

Filament material evaluation for breast phantom fabrication using three-dimensional printing

In this study, a method of directly evaluating the dose received by the highly radiation-sensitive mammary gland during mammography was investigated, and a corresponding breast phantom was produced that expresses a mammary gland, as an alternative to the existing mixed-form phantom. After designing this breast phantom by performing Monte Carlo simulations, the glandular dose was evaluated and compared with that of a mixed-form phantom. Then, dose evaluation was conducted for current commercial filament materials that could be used to fabricate the phantom by 3-D printing. The results showed that the dose received by the mammary gland was in the range of 1.089-1.237 mGy, and the average difference from that determined using the mixed-form phantom was approximately 1.2 %. Among the filament materials, polylactic acid showed the dose that was the most similar to that of the mammary gland tissue, differing by approximately 2.4 %. Overall, the research results suggest that it is meaningful to evaluate the glandular dose using the developed phantom instead of a mixed-form phantom. Besides, polylactic acid is the most appropriate material for fabricating the mammary gland tissue using a 3-D printer.