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This paper presents the preparation and measurement of tissue-mimicking head phantom and its validation with the iteratively corrected coherence factor delay-multiply-and-sum (IC-CF-DMAS) algorithm for brain stroke detection. The phantom elements are fabricated by using different chemical mixtures that imitate the electrical properties of real head tissues (CSF, dura, gray matter, white matter, and blood/stroke) over the frequency band of 1–4 GHz. The electrical properties are measured using the open-ended dielectric coaxial probe connected to a vector network analyzer. Individual phantom elements are placed step by step in a three-dimensional skull. The IC-CF-DMAS image reconstruction algorithm is later applied to the phantom to evaluate the effectiveness of detecting stroke. The phantom elements are preserved and measured multiple times in a week to validate the overall performance over time. The electrical properties of the developed phantom emulate the similar properties of real head tissue. Moreover, the system can also effectively detect the stroke from the developed phantom. The experimental results demonstrate that the developed tissue-mimicking head phantom is time-stable, and it shows a good agreement with the theoretical results in detecting and reconstructing the stroke images that could be used in investigating as a supplement to the real head tissue.

Purpose The purpose of this study is to use the Freeform Reversible Embedding of Suspended Hydrogels (FRESH) additive manufacturing (AM) technique for manufacturing a liver phantom which can mimic the corresponding soft living tissue. One of the possible applications is surgical planning. Design/methodology/approach A thermo-reversible Pluronic® F-127-based support bath is used for the FRESH technique. To verify how three-dimensional (3D)-printed new materials can mimic liver tissue, dynamic mechanical analysis and oscillation shear rheometry tests are carried out to identify mechanical characteristics of different 3D printed silicone samples. Additionally, the differential scanning calorimetry was done on the silicone samples. Then, a validation of a 3D printed silicone liver phantom is performed with a 3D scanner. Finally, the surface topography of the 3D printed liver phantom was fulfiled and microscopy analysis of its surface. Findings Silicone samples were able to mimic the liver, therefore obtaining the first soft phantom of the liver using the FRESH technique. Practical implications Because of the use of soft silicones, surgeons could practice over these improved phantoms which have an unprecedented degree of living tissue mimicking, enhancing their rehearsal experience before surgery. Social implications An improvement in surgeons surgery skills would lead to a bettering in the patient outcome. Originality/value The first research study was carried out to mimic soft tissue and apply it to the 3D printing of organ phantoms using AM FRESH technique.

Optical imaging has attracted recent attention as a non-invasive medical imaging method in biomedical and clinical applications. In optical imaging, a light beam is transmitted through an under-test tissue by using an optical source. The beams which are gone through the tissue and/or reflected from the tissue surfaces are received by an array sensor. Based on the light intensity of these received beams on the sensor, sub-tissue maps are generated to scan large tissue areas so that any further biopsy is not required. Although the large tissue areas in pathological images can be scanned by using various methods, nonlinear deformations occur. To overcome this problem, the reconstruction process is frequently used. In this study, we propose an application of biomedical imaging based on performing the reconstruction of a phantom image via an in-line digital holography technique. Hence, many different sub-tissues can be imaged at the same time without the storage problem of the reconstructed image. To neglect the biopsy process required in medical imaging, the phantom image is obtained by using a linear array transducer for this study. We present the performance evaluation of the simulation results for the proposed technique by calculating the error metrics such as mean squared error (MSE), mean absolute error (MAE), and peak signal-to-noise ratio (PSNR). The obtained results reveal that the reconstructed images are well-matched to the original images, which are desired to be displayed by the holography technique.

Objective To develop a thermochromic tissue-mimicking phantom (TTMP) with an embedded 3D-printed bone mimic of the lumbar spine to evaluate MRgFUS ablation of the facet joint and medial branch nerve. Materials and methods Multiple 3D-printed materials were selected and characterized by measurements of speed of sound and linear acoustic attenuation coefficient using a through-transmission technique. A 3D model of the lumbar spine was segmented from a de-identified CT scan, and 3D printed. The 3D-printed spine was embedded within a TTMP with thermochromic ink color change setpoint at 60 °C. Multiple high energy sonications were targeted to the facet joints and medial branch nerve anatomical location using an ExAblate MRgFUS system connected to a 3T MR scanner. The phantom was dissected to assess sonication targets and the surrounding structures for color change as compared to the expected region of ablation on MR-thermometry. Results The measured sound attenuation coefficient and speed of sound of gypsum was 240 Np/m-MHz and 2471 m/s, which is the closest to published values for cortical bone. Following sonication, dissection of the TTMP revealed good concordance between the regions of color change within the phantom and expected areas of ablation on MR-thermometry. No heat deposition was observed in critical areas, including the spinal canal and nerve roots from either color change or MRI. Conclusion Ablated regions in the TTMP correlated well with expected ablations based on MR-thermometry. These findings demonstrate the utility of an anatomic spine phantom in evaluating MRgFUS sonication for facet joint and medial branch nerve ablations.

Present study deals with improvement in conventional technique of spraying liquid nitrogen on cancerous lesions to improve its efficacy. It is an attempt to demarcate the variation in outcome when cryogen is sprayed through customised multi-hole nozzle (MHN). Influence of mass flow rate on cryoablation while varying the number of holes in MHNs is analysed experimentally. Another section of study focuses on the impact of the rate of evaporation of cryogen when margin among the holes is changed. Total 6 MHNs are fabricated while changing their geometrical parameters. Single freeze-thaw cycle is carried out to spray liquid nitrogen on tissue mimicking gel with a spraying distance of 18 mm. Temperature profile captured through infrared images advocates that lethal area formed through the application of MHNs with 5 holes is larger than MHNs with 4 holes on the surface of gel. It reflects the influence of central hole on necrosis. In order to necrotize lesion through freezing, the most desired cooling rate (CR) varies from 50∘C/min to 200∘C/min. It is achieved up to a depth of 2 mm below the gel surface and in a radius of 10 mm from the centre of spray (CS) for all MHNs, except 4C. Most optimised margin in terms of cryoablation is also estimated in the study. MHN with 1.5 mm margin provides the most optimised results in terms of cryoablation when MHNs with the central hole are considered while MHN with 1 mm margin provides most optimised result when MHNs without central hole are considered. On the basis of observations made through thermal images it can be said that multiple freezing fronts are not observed on the gel surface which aids in the formation of lone giant ice ball. This provides an extra edge to the treatment methodology because alteration in the dimensions of necrotic zone can be made by changing the duration of spray. Larger lateral spread of necrotic zone will also reduce the number of sittings required for the treatment of larger lesions.

Three-dimensional printed medical prototypes, which use synthetic metamaterials to mimic biological tissue, are becoming increasingly important in urgent surgical applications. However, the mimicki...

In this study, we determine the effect of temperature and frequency on the acoustic properties of konjac glucomannan (KGM)-agar gels to confirm their compatibilities as tissue mimicking materials (TMMs). The acoustic properties of four samples; A (KGM-0.10 g agar), B (KGM-0.20 g agar), C (KGM-0.30 g agar) and D (KGM-0.40 g agar) were measured using pulse echo immersion technique. Findings indicated that the longitudinal velocities of all samples were increased while their attenuation coefficients were decreased as the temperature increased from 27.0 to 37.0°C. It also showed that the phase velocities of all samples were independent to frequency but their attenuation coefficients were increased as the frequency increased from 4.0 to 6.0 MHz. KGM-agar gels are compatible as soft TMMs since their acoustic properties are comparable with the acoustic properties of soft tissue.

PURPOSE The assessment of the size and shape of breast tumors is of utter importance to the correct diagnosis and staging of breast cancer. In this paper, we classify breast tumor models of varying sizes and shapes using signals collected with a monostatic ultra-wideband radar microwave imaging prototype system with machine learning algorithms specifically tailored to the collected data. METHODS A database comprising 13 benign and 13 malignant tumor models with sizes between 13 and 40 mm was created using dielectrically representative tissue mimicking materials. These tumor models were placed inside two breast phantoms: a homogeneous breast phantom and a breast phantom with clusters of fibroglandular mimicking tissue, accounting for breast heterogeneity. The breast phantoms with tumors were imaged with a monostatic microwave imaging prototype system, over a 1-6 GHz frequency range. The classification of benign and malignant tumors embedded in the two breast phantoms was completed, and tumor classification was evaluated with Principal Component Analysis as a feature extraction method, and tuned Naive Bayes (NB), decision trees (DT), and k-nearest neighbours (kNN) as classifiers. We further study which antenna positions are better placed to classify tumors, discuss the feature extraction method and optimize classification algorithms, by tuning their hyperparameters, to improve sensitivity, specificity and the receiver operating characteristic curve, while ensuring maximum generalization and avoiding overfitting and data contamination. We also added a realistic synthetic skin response to the collected signals and examined its global effect on classification of benign vs malignant tumors. RESULTS In terms of global classification performance, kNN outperformed DT and NB machine learning classifiers, achieving a classification accuracy of 96.2% when classifying between benign and malignant tumor phantoms in a homogeneous breast phantom (both when the skin artifact is and is not considered). CONCLUSIONS We experimentally classified tumor models as benign or malignant with a microwave imaging system, and we showed a methodology that can potentially assess the shape of breast tumors, which will give further insight into the correct diagnosis and staging of breast cancer.

Purpose The stiffness of Polyvinyl-alcohol cryogel can be adjusted through application of consecutive freeze-thaw cycles. This material has potential applications in the production of tissue mimicking phantoms in diagnostic ultrasound. The aim of this study was to use PVA-c to produce a range of geometrically and acoustically identical vessel phantoms modelling stages of atherosclerosis which could be verified through mechanical testing, thus allowing for more precision in quantitative in-vitro flow analysis of atherosclerosis. Methods A series of anatomically realistic walled renal artery flow phantoms were constructed using PVA-c. In order to ensure precise modelling of atherosclerosis, a modified procedure of ISO27:2017 was used to compare the mechanical properties of PVA-c. Results were compared for the standard “dumbbell” test object and a modified vessel test object. The geometric accuracy and reproducibility of the vessel models were tested before and after implantation in flow phantoms. Results No significant difference was found between the mechanical properties of the dumbbell test samples and the vessels for any number of freeze thaw cycles, with a correlation coefficient of R2 = 0.9767 across the dataset, indicating that a direct comparison between the mechanical properties of the dumbbell test samples and the phantom vessels was established. The geometric reproducibility showed that before and after implantation there was no significant difference between individual vessel geometries (p = 0.337 & p = 0.176 respectively). Conclusions Polyvinyl-alcohol cryogel is a useful material for the production of arterial flow phantoms. Care should be taken when using this material to ensure its mechanical properties have been correctly characterised. The guidelines of ISO37:2017 potentially provide the best procedure to ensure this.

PURPOSE: To develop and characterize a tissue-mimicking phantom that enables the direct comparison of magnetic resonance (MR) and ultrasound (US) imaging techniques useful for monitoring high-intensity focused ultrasound (HIFU) treatments. With no additions, gelatin phantoms produce little if any scattering required for US imaging. This study characterizes the MR and US image characteristics as a function of psyllium husk concentration, which was added to increase US scattering. METHODS: Gelatin phantoms were constructed with varying concentrations of psyllium husk. The effects of psyllium husk concentration on US B-mode and MR imaging were evaluated at nine different concentrations. T1, T2, and T2* MR maps were acquired. Acoustic properties (attenuation and speed of sound) were measured at frequencies of 0.6, 1.0, 1.8, and 3.0 MHz using a through-transmission technique. Phantom elastic properties were evaluated for both time and temperature dependence. RESULTS: Ultrasound image echogenicity increased with increasing psyllium husk concentration while quality of gradient-recalled echo MR images decreased with increasing concentration. For all phantoms, the measured speed of sound ranged between 1567–1569 m/s and the attenuation ranged between 0.42–0.44 dB/(cm∙MHz). Measured T1 ranged from 974–1038 ms. The T2 and T2* values ranged from 97–108 ms and 49–89 ms, respectively, with both showing a decreasing trend with increased psyllium husk concentration. Phantom stiffness, measured using US shear-wave speed measurements, increased with age and decreased with increasing temperature. CONCLUSIONS: The presented dual-use tissue-mimicking phantom is easy to manufacture and can be used to compare and evaluate US-guided and MR-guided HIFU imaging protocols.

The Tissue Mimicking Materials (TMM), are widely used in medical research, training, clinical simulators etc., to simulate the properties which are much more similar to that of the real biological tissues. In medical research TMM plays a vital role as the idealized tissue models to design and to test the methods, systems and clinical tools etc. In general TMM are made from bio polymers (agar, agarose, gelatin and gellan gum) and chemically synthesized polymers (polyvinyl alcohol, polymerized siloxanes, poly vinyl chlorides). The bio polymers have the properties of high mass fraction of water (>80%), due to this these biopolymers are not stable for long term use and also have a bacterial growth in a material. On the other hand, the chemically synthesized polymers have a lack of less similar properties to that of the skin. Ratio of softener and polymer, mass fraction of mineral oil and micronized glass beads are factors playing the major role in deciding the properties of TMM. Moreover, by using these TMM the mechanics of needle insertion such as applied force, friction between the needle and tissue and velocity of insertion etc. are studied to use it effectively in clinical applications. Even though, quite number of TMM are developed and tested, the TMM having properties which are very closer to real biological tissue at different aging periods are not available. Therefore, the researchers are working continuously to develop such kind of materials and it needs a depth understanding of available materials and its properties. This paper focuses on presenting a detailed literature study on development and characterization of various TMM, which will be useful for the researchers to develop new TMM for clinical training and clinical tool testing applications

Glioblastomas are malignant tumors of the central nervous system hallmarked by subclonal diversity and dynamic adaptation amid developmental hierarchies. The source of the dynamic reorganization within the spatial context of these tumors remains elusive. Here, we characterized glioblastomas in-depth by spatially resolved transcriptomics, metabolomics and proteomics. By deciphering regional shared transcriptional programs across patients, we infer that glioblastomas are organized by spatial segregation of lineage states and adapt to inflammatory or metabolic stimuli reminiscent of reactive transformation in mature astrocytes. Integration of metabolic imaging and image mass cytometry uncovered locoregional tumor-host interdependence resulting in spatially exclusive adaptive transcriptional programs. Inferring copy-number alterations emphasizes a spatially cohesive organization of subclones associated with reactive transcriptional programs, confirming that environmental stress gives rise to selection pressure. A model of glioblastoma stem cells implanted into human and rodent neocortical tissue mimicking various environments confirmed that transcriptional states originate from dynamic adaptation to various environments. Funding: DHH is funded by the Else Kroner-Fresenius Foundation. The work is part of the MEPHISTO project (PI: DHH and DD), funded by BMBF (iGerman Ministry of Education and Research) (project number: 031L0260B). The Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) supports the work of AW (project number: SFB 824 C04). VR, KJ and UGH funded by BMBF (Bundes Ministerium fur Bildung und Forschung) (project number: FMT 13GW0230A), US was supported by the Fordergemeinschaft Kinderkrebszentrum Hamburg. We thank Dietmar Pfeifer for here helpful advice. We thank Biorender.com. We thank Stella Maria Carro for her support and the provision of her laboratory facilities and equipment. Declaration of Interest: No potential conflicts of interest were disclosed by the authors. Ethical Approval: The local ethics committee of the University of Freiburg approved the data evaluation, imaging procedures and experimental design (protocol 100020/09 and 472/15_160880).

The aim of this study is to analyse the mechanical properties of agarose, which can be used as a mechanical phantom for breast tissues. In general, tissue mimicking materials may be used to achieve a better understanding of the structure and properties of tissues and organs; this work shares these objectives. The phantom can be used as a tissue surrogate with realistic mechanical behaviour for biomechanical applications. To validate agarose as a suitable mechanical phantom for breast tissues, indentation tests were performed in homogeneous, rectangular agarose blocks. Blocks with different agarose concentrations were moulded and tested. An estimation of the material stiffness was then compared with experimental data on different breast tissues’ types found in literature. The phantom stiffness increased consistently with agarose concentration and stress. The results show that agarose-based mechanical phantoms of stiffer tissues require higher agarose concentrations (0.5% and 0.6%). In contrast, normal tissues can be mimicked with 0.3% and 0.4% of agarose. In addition, it was observed that preconditioning affects the mechanical properties of the gel, as it had already been shown in literature for breast tissues.

Microwave diagnostic and treatment technologies for breast cancer have been a popular research interest among researchers. To test the proposed systems many different tissue mimicking phantom materials have been proposed in the literature for testing of microwave breast cancer imaging and hyperthermia devices. One popular tissue mimicking phantom, named oil-in-gelatin dispersion phantoms, are used widely to replicate the dielectric properties different tissue types. These phantoms are used for testing of implantable antennas, microwave imaging devices, and hyperthermia devices. However, the temperature dependent dielectric properties of the phantoms have not been investigated in the literature. This work investigates the dielectric properties of the phantoms with respect to temperature to validate the phantoms can replicate the temperature-dependent dielectric properties of the tissues.

In this paper, the mechanical properties of tissue-mimicking phantoms, produced and dielectrically tested to mimic breast tissues, are presented. Testing on phantoms represents one of the key steps in the process of realization of several devices and, for this reason, the interest towards the realization of more and more realistic phantoms, not only from the dielectric point of view but also from the mechanical one, is growing. In this work, tissue-mimicking mixtures, based on the use of low-cost, safe and easy-to-handle materials (water, oil, gelatin and dishwashing liquid), produced for the realization of breast phantoms have been tested under different measurement conditions. Stress-strain curves are reported and a first comparison with Young's moduli in the literature of gelatin-based phantoms produced for the same anatomical district is presented. This work represents a first step in the realization of increasingly realistic tissue-mimicking mixtures, which, among other things, may pave the way for new combined imaging modalities.

Shell-based breast phantoms use shells to contain liquids that act as breast tissue surrogates by mimicking the dielectric properties of breast tissues. These phantoms are advantageous for their ease of use, robustness, and experimental utility. The use of liquids as the tissue mimicking material allows the user to create and readily modify liquid solutions to model the desired dielectric properties, the free positioning of tumour surrogates inside healthy tissues, and experimental reproducibility and transparency when 3D-printed plastic shells are used. The primary disadvantage of shell-based phantoms is their use of (typically low permittivity) shell materials to hold the tissue-mimicking liquids. This work investigates the impact of a 0.66 mm thick glass shell, used to contain a tumour-mimicking solution, on the measured S 11 response in a pre-clinical breast microwave sensing system. A statistical analysis of the results obtained in this work indicate that the presence of the glass shell produces a response that cannot be detected by the imaging system, and therefore is suitable for use in shell-based phantoms.

We describe a case of an extremely rare intrathoracic supradiaphragmatic accessory liver tissue that was excised via transdiaphragmatic uniportal video-assisted thoracoscopic surgery. The intrathoracic mass that was radiologically detected was found to be mimicking a pleural tumour because of its supradiaphragmatic location as well as the presence of a clear cleavage plane separating the mass and the liver completely. This, to our knowledge, is the first described case that was resected via transdiaphragmatic uniportal approach in the literature.

Introduction: Microwaves (MWs) quickly deliver relatively high temperatures into tumors and cover a large ablation zone. We present a research protocol for using water-cooled double-needle MW ablat...

In vitro derived simplified 3D representations of human organs or organ functionalities are predicted to play a major role in disease modeling, drug development, and personalized medicine, as they complement traditional cell line approaches and animal models. The cells for 3D organ representations may be derived from primary tissues, embryonic stem cells or induced pluripotent stem cells and come in a variety of formats from aggregates of individual or mixed cell types, self‐organizing in vitro developed “organoids” and tissue mimicking chips. Microfluidic devices that allow long‐term maintenance and combination with other tissues, cells or organoids are commonly referred to as “microphysiological” or “organ‐on‐a‐chip” systems. Organ‐on‐a‐chip technology allows a broad range of “on‐chip” and “off‐chip” analytical techniques, whereby “on‐chip” techniques offer the possibility of real time tracking and analysis. In the rapidly expanding tool kit for real time analytical assays, mass spectrometry, combined with “on‐chip” electrophoresis, and other separation approaches offer attractive emerging tools. In this review, we provide an overview of current 3D cell culture models, a compendium of current analytical strategies, and we make a case for new approaches for integrating separation science and mass spectrometry in this rapidly expanding research field.

Curing of cancerous tumour using cryosurgery is accepted in the present time. But still its adoption is challenged because of its lower efficacy and a threat to the healthy cells. It is difficult to stop the lethal front from entering into healthy tissue zone. Therefore, complete destruction of defected tissue along with protection of neighboring healthy tissue is of main concern. To vanquish these constraints, many approaches have been used so far. In this numerical analysis, an approach is proposed in which a localised specific solution with lower thermal conductivity is injected to cover the axial portion of tumour. For this purpose, perfluorohexane is used which has a low thermal conductivity. With this novel approach, freezing becomes very fast and significant along with the minimal damage to the surrounding health tissue. It also helps in achieving lethal temperature in shorter time span. The propagation of the lethal front is calculated numerically. These real time lethal volume data helps the clinical practitioners in estimation of extent of freezing necrosis and time duration for cryosurgery. A parametric study was performed on tissue mimicking gel with various insertion depths of cryoprobe and different concentrations of gel. Both the parameters have a remarkable effect on the amount of freezing. The problem is analyzed using multi block structured grid and numerical results obtained showed good compliance to the experimental data.

Although the ultrasonic C-scan technique has been extensively applied in nondestructive testing (NDT) in recent years, 3D reconstruction from ultrasonic C-scan images has not been well addressed. This paper develops a novel and efficient 3D reconstruction technique based on an improved K-nearest neighbor filtering for ultrasonic C-scan data of the tissue-mimicking phantoms. An edge-points-predicting approach based on K-nearest neighbor filtering is first proposed to predict the undetected edge points and to reduce the noise points for 2D ultrasonic images. Then, the 3D model is reconstructed from the clean edges by utilizing the surface rendering algorithm. The proposed approach is validated using the ultrasonic C-scan data of a liver model embedded in a tissue-mimicking phantom. The comparisons with other methods are presented in the experiments. The results demonstrate the effectiveness and the significantly improved reconstruction results of the proposed approach.

This paper presents a methodology for the preparation of a phantom arm model to be used for evaluating the performance of intra-body communications specifically and body area networks (BANs) in general. This paper describes the basic procedures for preparing tissue mimicking materials for each of the five basic tissue layers: skin, fat, muscle, cortical bone, and bone marrow. Matching materials for mimicking the dielectric properties of each tissue, with a mimic accuracy of at least 90%, were finally selected, after carrying out experimental testing on more than 50 different test samples that were prepared using different techniques and mixture concentrations. The final arm phantom is then fabricated and tested. The experimental results, mainly the gain/attenuation profile, are then displayed and compared with those obtained from the real subjects with similar experimental setup conditions showing very close to perfect match, proving the high accuracy of the fabricated arm phantom model in mimicking the dielectric behavior of real body parts, over the frequency range of interests for intra-body communications (100 kHz to 100 MHz). To date, this is the first accurate physical five-layer phantom arm model fabricated for intra-body communication applications covering this frequency range and with such high accuracy.

Tissue polarimetry could be identified as a complementary optical and non-invasive technique to assist the gold standard histopathology analysis of tissue. In general, polarimetric diagnostics is based on tracing different polarimetric responses (including light depolarization) in tissue zones with structure altered by the benign and pre/cancerous formations. In this manuscript, both healthy and malignant tissue zones of a thick formalin-fixed colon specimen were used for Mueller matrix measurements. Additionally, two more Mueller matrices from Monte Carlo simulation and tissue mimicking phantom were also evaluated, in order to assess polarimetric char- acterization and modeling of turbid media. Symmetric decomposition algorithm of Mueller matrices developed in house was adopted to extract both polarization and depolarization properties, encoded in the Mueller matrix elements. The decomposition products allowed to reveal important information about the internal tissue struc- ture and morphology. The depolarization and polarization parameters were found to follow the particular trends that depend on a choice of parametric space.

Photoacoustic imaging (PAI) and photoacoustic microscopy (PAM) continue to undergo advancement, but standardized performance test methods are needed to facilitate development and translation. Most tissue-mimicking materials (TMMs) have not been adequately characterized at high acoustic frequencies relevant to PAM systems (>20 MHz). We characterized acoustic properties of various polyacrylamide TMM formulations over 10-60 MHz using a pulse-echo method, while optical properties were characterized over 400-1000 nm. We evaluated performance of a custom PAM system using phantoms containing gold nanoparticles. Polyacrylamide had highly tunable acoustic properties similar to human skin, and performance tests provided key insights into PAM system performance.

Venepuncture is one of the most often performed invasive clinical procedure. Nevertheless, complications still occur. One possibility to counteract these complications is to indicate the insertion by electrical impedance measurement, based on the various electrical properties of different tissues. This paper presents the evaluation and reproducible fabrication of simple tissue-mimicking phantoms for investigation of impedance sensing techniques. Three different tissue-mimicking phantoms, representing blood, fat, and skin, were made on water-based recipes, including agar and gelatin as gelling agents. For evaluation of the electrical properties an electrode probe, made of hypodermic needles, was fabricated and characterized using six sodium chloride (NaCl) solutions of defined concentrations. For characterization of the phantoms, conductances were measured over a frequency range from 20 Hz up to 1 MHz using the self-fabricated electrodes. The calculated conductivities of the tissue-mimicking phantoms show sufficient agreement with corresponding electrical literature data of native tissue. However, the method was not suitable for investigation of relative permittivity, which would be required for full electrical characterization.

Within the brachytherapy community, many phantoms are constructed in-house, and less commercial development is observed as compared to the field of external beam. Computational or virtual phantom design has seen considerable growth; however, physical phantoms are beneficial for brachytherapy, in which quality is dependent on physical processes, such as accuracy of source placement. Focusing on the design of physical phantoms, this review paper presents a summary of brachytherapy specific phantoms in published journal articles over the last twenty years (January 1, 2000 - December 31, 2019). The papers were analyzed and tabulated by their primary clinical purpose, which was deduced from their associated publications. A substantial body of work has been published on phantom designs from the brachytherapy community, but a standardized method of reporting technical aspects of the phantoms is lacking. In-house phantom development demonstrates an increasing interest in magnetic resonance (MR) tissue mimicking materials, which is not yet reflected in commercial phantoms available for brachytherapy. The evaluation of phantom design provides insight into the way, in which brachytherapy practice has changed over time, and demonstrates the customised and broad nature of treatments offered.

Breast cancer is one of the leading causes of cancer death among women, to decrease the death rate for this disease, early detection plays a key role. Recently, microwave imaging systems have been proposed as an alternative to the current techniques, but they suffer from poor resolution due to the low frequencies involved. In this paper, for the first time, an innovative millimeter-wave imaging system for early-stage breast cancer detection is proposed and experimentally verified on different breast phantoms. This has the potential to achieve superior resolution for breasts with a high volumetric percentage of adipose tissue, and the merit to overcome the common misconception that millimeter-waves cannot achieve useful penetration depths for biological applications. Three phantoms were prepared according to the dielectric properties of human breast ex vivo tissues in the frequency range [0.5&ndash, 50] GHz. Two cylindrical inclusions made by water and gelatin or agar, mimicking dielectric properties of neoplastic tissues, were embedded in the phantom at different depths up to 3 cm. Two double ridge waveguides, with mono-modal frequency band equal to [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40] GHz, were used to synthetize a linear array of 24 elements in 28 positions, acquiring signals with a Vector Network Analyzer. The images were reconstructed by applying the Delay and Sum algorithm to calibrated data. The feasibility of a new imaging system with a central working frequency of about 30 GHz is experimentally demonstrated for the first time, and a target detection capability up to 3 cm within the phantom is shown. The presented results pave the way for a possible use of millimeter-waves to image non-superficial neoplasms in the breast.

In this work, the dielectric characterization of human tissue-mimicking phantoms is analyzed and tested for breast imaging applications. Phantom samples are obtained by using common and easily available ingredients. They are characterized within the 0.5–5 GHz frequency range, by adopting an open ended-coaxial probe measurement setup. The permittivity behavior of the simulated tissues are compared with some existing reference models for breast tissues. Furthermore, the measured tissues phantoms values are exploited to simulate a series of realistic breast models with different densities. Starting from this revised modeling, a phaseless microwave imaging technique proposed by the same authors is tested.

Current anatomical 3D printing has been primarily used for education, training, and surgical planning purposes. This is largely due to the models being printed in materials which excel at replicating macro-level organic geometries; however, these materials have the drawback of unrealistic mechanical behavior and system properties compared to biological tissue. The new Digital Anatomy (DA) family of materials from Stratasys utilizes composite printed materials to more closely mimic mechanical behavior of biological tissue, potentially allowing more realistic models for design evaluation. Various experimental DA Solid Organ (SO) configurations were quantitatively evaluated under axial loading for comparison with porcine liver in terms of stiffness. Additionally, Structural Heart - Myocardium (Myo) configurations were quantitatively evaluated under different lubricant conditions for comparison with porcine epicardium and aorta in terms of lubricity. Finally, experimental DA Subcutaneous Tissue configurations were qualitatively evaluated by experts with significant pre-clinical implant experience for cutting, tunneling, and puncture procedures.In general, the experimental SO configurations showed promising compliance results when compared to porcine liver. The stiffness of DA configurations was either within the same range or on the lower bound of porcine tissue stiffness values. The lubricity of DA configurations with surface treatments was comparable with porcine epicardium and aorta. In terms of qualitative cutting, DA did not perform well for any of the configurations; however, tunneling and puncture were rated favorably for some of the experimental configurations. Despite some limitations, DA feels closer to real tissue than other commercially available 3D printed materials. Furthermore, the lower sample-to-sample variability of DA allows for repeatability not provided by biological tissue. The promising results and repeatability indicate that DA materials can be used to configure structures with similar characteristic mechanical properties to porcine liver, epicardium, and subcutaneous tissue, adding new value as not only an educational, training, and surgical tool, but also as a research tool.

Purpose Flow phantoms are used in experimental settings to aid in the simulation of blood flow. Custom geometries are available, but current phantom materials present issues with degradability and/or mimicking the mechanical properties of human tissue. In this study, a method of fabricating custom wall-less flow phantoms from a tissue-mimicking gel using 3D printed inserts is developed. Methods A 3D blood vessel geometry example of a bifurcated artery model was 3D printed in polyvinyl alcohol, embedded in tissue-mimicking gel, and subsequently dissolved to create a phantom. Uniaxial compression testing was performed to determine the Young’s moduli of the five gel types. Angle-independent, ultrasound-based imaging modalities, Vector Flow Imaging (VFI) and Blood Speckle Imaging (BSI), were utilized for flow visualization of a straight channel phantom. Results A wall-less phantom of the bifurcated artery was fabricated with minimal bubbles and continuous flow demonstrated. Additionally, flow was visualized through a straight channel phantom by VFI and BSI. The available gel types are suitable for mimicking a variety of tissue types, including cardiac tissue and blood vessels. Conclusion Custom, tissue-mimicking flow phantoms can be fabricated using the developed methodology and have potential for use in a variety of applications, including ultrasound-based imaging methods. This is the first reported use of BSI with an in vitro flow phantom.

This comparative study analyzes the dielectric properties of different skin mimicking tissue phantoms for the development of microwave radar prototypes for early breast cancer detection. Therefore, the properties of a fat mimicking carbon-polyurethane-based phantom were verified, and the dielectric properties of three different skin phantoms in four scenarios measured. Furthermore, the dielectric properties were compared to those of the excised human tissue reported in the literature.