Fabrication and Characterization of Tissue-Mimicking Phantoms for Ultrasound-Guided Cannulation Training

Tissue-Mimicking Materials for Breast Ultrasound Elastography Phantoms: A Systematic Review

Breast ultrasound elastography phantoms are valued for their ability to mimic human tissue, enabling calibration for quality assurance and testing of imaging systems. Phantoms may facilitate the development and evaluation of ultrasound techniques by accurately simulating the properties of breasts. However, selecting appropriate tissue-mimicking materials for realistic and accurate ultrasound exams is crucial to ensure the ultrasound system responds similarly to real breast tissue. We conducted a systematic review of the PubMed, Scopes, Embase, and Web of Sciences databases, identifying 928 articles in the initial search, of which 19 were selected for further evaluation based on our inclusion criteria. The chosen article focused on tissue-mimicking materials in breast ultrasound elastography phantom fabrication, providing detailed information on the fabrication process, the materials used, and ultrasound and elastography validation of phantoms. The phantoms fabricated from Polyvinyl Chloride Plastisol, silicon, and paraffin were best suited for mimicking breast, fatty, glandular, and parenchyma tissues. Adding scatterers to these materials facilitates accurate fatty and glandular breast tissue simulations, making them ideal for ultrasound quality assurance and elastography training. Future research should focus on developing more realistic phantoms for advanced medical training, improving the practice of difficult procedures, enhancing breast cancer detection research, and providing tailored tissue characteristics.

Fabrication and evaluation of breast tissue equivalent phantoms for image quality assessment in ultrasound imaging

INTRODUCTION

Phantom materials with tissue-equivalent physical properties that require regular evaluation using patented phantoms are essential for medical device quality assurance programs. This study evaluated phantom materials for tissue equivalence and their use in image quality assessment for breast ultrasound scanner performance testing using two custom-made phantoms.

METHODS

Two types of phantoms were developed: phantoms A and B. Phantom A was made from a base material consisting of polyvinyl chloride-plastisol with the addition of glycerol, whereas phantom B consisted of polyvinyl chloride-plastisol with the addition of graphite. Each phantom had a stiff and soft lesion shaped like a sphere, with a diameter of 1.4 cm. The phantoms were cuboids with dimensions of 10 × 10 cm2 and a thickness of 5 cm. A series of phantom evaluations was performed, consisting of density, elasticity, acoustic properties, B-mode ultrasound images, and strain ratio.

RESULTS

The characterisation results show that background A closely resembles fibroglandular tissue in terms of density and acoustic properties (<5% variation); background B only resembles fibroglandular tissue in terms of density (-1.8% variation). In terms of elasticity, both backgrounds were close to the minimum value of fibroglandular tissue elasticity. The soft lesion on the phantom had a slightly lower density and elasticity than the carcinoma, whereas its acoustic properties (speed of sound and attenuation coefficient) were slightly higher than those of the reference carcinoma. Both phantoms were consistent with the literature in terms of strain ratio, geometric accuracy, lesion detection, and mean pixel value and showed good potential stability over one year.

CONCLUSION

This study successfully described the fabrication and evaluation sequence of a phantom equivalent to breast fibroglandular tissue and its evaluation via ultrasound imaging.

IMPLICATIONS FOR PRACTICE

This study offers proprietary information essential for the fabrication of phantoms that can be used for quality assurance and control in ultrasound imaging.

Using torsional wave elastography to evaluate spring pot parameters in skin tumor mimicking phantoms

Estimating the tissue parameters of skin tumors is crucial for diagnosis and effective therapy in dermatology and related fields. However, identifying the most sensitive biomarkers require an optimal rheological model for simulating skin behavior this remains an ongoing research endeavor. Additionally, the multi-layered structure of the skin introduces further complexity to this task. In order to surmount these challenges, an inverse problem methodology, in conjunction with signal analysis techniques, is being employed. In this study, a fractional rheological model is presented to enhance the precision of skin tissue parameter estimation from the acquired signal from torsional wave elastography technique (TWE) on skin tumor-mimicking phantoms for lab validation and the estimation of the thickness of the cancerous layer. An exhaustive analysis of the spring-pot model (SP) solved by the finite difference time domain (FDTD) is conducted. The results of experiments performed using a TWE probe designed and prototyped in the laboratory were validated against ultrafast imaging carried out by the Verasonics Research System. Twelve tissue-mimicking phantoms, which precisely simulated the characteristics of skin tissue, were prepared for our experimental setting. The experimental data from these bi-layer phantoms were measured using a TWE probe, and the parameters of the skin tissue were estimated using inverse problem-solving. The agreement between the two datasets was evaluated by comparing the experimental data obtained from the TWE technique with simulated data from the SP- FDTD model using Pearson correlation, dynamic time warping (DTW), and time-frequency representation. Our findings show that the SP-FDTD model and TWE are capable of determining the mechanical properties of both layers in a bilayer phantom, using a single signal and an inverse problem approach. The ultrafast imaging and the validation of TWE results further demonstrate the robustness and reliability of our technology for a realistic range of phantoms. This fusion of the SP-FDTD model and TWE, as well as inverse problem-solving methods has the potential to have a considerable impact on diagnoses and treatments in dermatology and related fields.

Tissue-Mimicking Material Fabrication and Properties for Multiparametric Ultrasound Phantoms: A Systematic Review

Medical imaging has allowed for significant advancements in the field of ultrasound procedures over the years. However, each imaging modality exhibits distinct limitations that differently affect their accuracy. It is imperative to ensure the quality of each modality to identify and eliminate these limitations. To achieve this, a tissue-mimicking material (TMM) phantom is utilised for validation. This study aims to perform a systematic analysis of tissue-mimicking materials used for creating ultrasound phantoms. We reviewed 234 studies on the use of TMM phantoms in ultrasound that were published from 2013 to 2023 from two research databases. Our focus was on studies that discussed TMMs' properties and fabrication for ultrasound, elastography, and flow phantoms. The screening process led to the selection of 16 out of 234 studies to include in the analysis. The TMM ultrasound phantoms were categorised into three groups based on the solvent used; each group offers a broad range of physical properties. The water-based material most closely aligns with the properties of ultrasound. This study provides important information about the materials used for ultrasound phantoms. We also compared these materials to real human tissues and found that PVA matches most of the human tissues the best.

Development, evaluation, and overview of standardized training phantoms for abdominal ultrasound-guided interventions

PURPOSE

Ultrasound (US) represents the primary approach for abdominal diagnosis and is regularly used to guide diagnostic and therapeutic interventions (INVUS). Due to possible serious INVUS complications, structured training concepts are required. Phantoms can facilitate teaching, but their use is currently restricted by complex manufacturing and short durability of the materials. Hence, the aim of this study was the development and evaluation of an optimized abdominal INVUS phantom.

MATERIALS AND METHODS

Phantom requirements were defined in a structured research process: Skin-like surface texture, homogeneous matrix with realistic tissue properties, implementation of lesions and abscess cavities in different sizes and depths as well as a modular production process allowing for customized layouts. The phantom prototypes were evaluated in certified ultrasound courses.

RESULTS

In accordance with the defined specifications, a new type of matrix was developed and cast in multiple layers including different target materials. The phantom structure is based on features of liver anatomy and includes solid focal lesions, vessels, and abscess formations. For a realistic biopsy procedure, ultrasound-proof material was additionally included to imitate bone. The evaluation was performed by US novices (n=40) and experienced participants (n=41). The majority (73/81) confirmed realistic visualization of the lesions. The 3D impression was rated as "very good" in 64% of cases (52/81) and good in 31% (25/81). Overall, 86% (70/81) of the participants certified high clinical relevance of the phantom.

CONCLUSION

The presented INVUS phantom concept allows standardized and realistic training for interventions.

Customisable Silicone Vessels and Tissue Phantoms for In Vitro Photoplethysmography Investigations into Cardiovascular Disease

Age-related vessel deterioration leads to changes in the structure and function of the heart and blood vessels, notably stiffening of vessel walls, increasing the risk of developing cardiovascular disease (CVD), which accounts for 17.9 million global deaths annually. This study describes the fabrication of custom-made silicon vessels with varying mechanical properties (arterial stiffness). The primary objective of this study was to explore how changes in silicone formulations influenced vessel properties and their correlation with features extracted from signals obtained from photoplethysmography (PPG) reflectance sensors in an in vitro setting. Through alterations in the silicone formulations, it was found that it is possible to create elastomers exhibiting an elasticity range of 0.2 MPa to 1.22 MPa. It was observed that altering vessel elasticity significantly impacted PPG signal morphology, particularly reducing amplitude with increasing vessel stiffness (p < 0.001). A p-value of 5.176 × 10-15 and 1.831 × 10-14 was reported in the red and infrared signals, respectively. It has been concluded in this study that a femoral artery can be recreated using the silicone material, with the addition of a softener to achieve the required mechanical properties. This research lays the foundation for future studies to replicate healthy and unhealthy vascular systems. Additional pathologies can be introduced by carefully adjusting the elastomer materials or incorporating geometrical features consistent with various CVDs.

Tissue-Mimicking Materials for Ultrasound-Guided Needle Intervention Phantoms: A Comprehensive Review

Ultrasound-guided needle interventions are common procedures in medicine, and tissue-mimicking phantoms are widely used for simulation training to bridge the gap between theory and clinical practice in a controlled environment. This review assesses tissue-mimicking materials from 24 studies as candidates for a high-fidelity ultrasound phantom, including methods for evaluating relevant acoustic and mechanical properties and to what extent the reported materials mimic the superficial layers of biological tissue. Speed of sound, acoustic attenuation, Young's modulus, hardness, needle interaction forces, training efficiency and material limitations were systematically evaluated. Although gelatin and agar have the closest acoustic values to tissue, mechanical properties are limited, and strict storage protocols must be employed to counteract dehydration and microbial growth. Polyvinyl chloride (PVC) has superior mechanical properties and is a suitable alternative if durability is desired and some ultrasound realism to human tissue may be sacrificed. Polyvinyl alcohol (PVA), while also requiring hydration, performs well across all categories. Furthermore, we propose a framework for the evaluation of future ultrasound-guided needle intervention tissue phantoms to increase the fidelity of training programs and thereby improve clinical performance.