Phantom Body Research Articles

MRI-compatible abdomen phantom to mimic respiratory-triggered organ movement while performing needle-based interventions.

In vivo studies are often required to prove the functionality and safety of medical devices. Clinical trials are costly and complex, adding to ethical scrutiny of animal testing. Anthropomorphic phantoms with versatile functionalities can overcome these issues with regard to medical education or an effective development of assistance systems during image-guided interventions (e.g., robotics, navigation/registration algorithms). In this work, an MRI-compatible and customizable motion phantom is presented to mimic respiratory-triggered organ movement as well as human anatomy. For this purpose, polyvinyl alcohol cryogel (PVA-C) was the foundation for muscles, liver, kidneys, tumors, and remaining abdominal tissue in different sizes of the abdominal phantom body (APB) with the ability to mimic human tissue in various properties. In addition, a semi-flexible rib cage was 3D-printed. The motion unit (MU) with an electromagnetically shielded stepper motor and mechanical extensions simulated a respiration pattern to move the APB. Each compartment of the APB complied the relaxation times, dielectricity, and elasticity of human tissue. It showed resistance against mold and provided a resealable behavior after needle punctures. During long-term storage, the APB had a weight loss of 2.3%, followed by changes to relaxation times of 9.3% and elasticity up to 79%. The MU was able to physiologically appropriately mimic the organ displacement without reducing the MRI quality. This work presents a novel modularizable and low-cost PVA-C based APB to mimic fundamental organ motion. Beside a further organ motion analysis, an optimization of APB's chemical composition is needed to ensure a realistic motion simulation and reproducible long-term use. This phantom enhances diverse and varied training environments for prospective physicians as well as effective R&D of medical devices with the possibility to reduce in vivo experiments.

Radiation Exposure and Safety Considerations in Interventional Radiology: Comparison of a Twin Robotic X-ray System to a Conventional Angiography System.

Background/Objectives: To evaluate radiation exposure in standard interventional radiology procedures using a twin robotic X-ray system compared to a state-of-the-art conventional angiography system. Methods: Standard interventional radiology procedures (port implantation, SIRT, and pelvic angiography) were simulated using an anthropomorphic Alderson RANDO phantom (Alderson Research Laboratories Inc. Stamford, CT, USA) on an above-the-table twin robotic X-ray scanner (Multitom Rax, Siemens Healthineers, Forchheim, Germany) and a conventional below-the-table angiography system (Artis Zeego, Siemens Healthineers, Forchheim, Germany). The phantom's radiation exposure (representing the potential patient on the procedure table) was measured with thermoluminescent dosimeters. Height-dependent dose curves were generated for examiners and radiation technologists in representative positions using a RaySafe X2 system (RaySafe, Billdal, Sweden). Results: For all scenarios, the device-specific dose distribution differs depending on the imaging chain, with specific advantages and disadvantages. Radiation exposure for the patient is significantly increased when using the Multitom Rax for pelvic angiography compared to the Artis Zeego, which is evident in the dose progression through the phantom's body as well as in the organ-related radiation exposure. In line with these findings, there is an increased radiation exposure for the performing proceduralist, especially at eye level, which can be significantly minimized by using protective equipment (p < 0.001). Conclusions: In this study, the state-of-the-art conventional below-the-table angiography system is associated with lower radiation dose exposures for both the patient and the interventional radiology physician compared to an above-the-table twin robotic X-ray system for pelvic angiographies. However, in other clinical scenarios (port implantation or SIRT), both devices are suitable options with acceptable radiation exposure.

An anthropomorphic body phantom for the determination of calibration factor in radionuclide treatment dosimetry.

The aim of this study is to create an inhomogeneous human-like phantom, whose attenuation and scattering effects are similar to the human body, as an alternative to the homogeneous phantoms traditionally used in calibration factor (CF) determination. The phantom was designed to include the thorax, abdomen and upper pelvis regions sized to represent a 75-kg male with a body mass index of 25. Measurements using Lu-177 with 50- and 100-mL lesion volumes were performed using inhomogeneous anthropomorphic body phantom (ABP) and homogeneous NEMA PET body phantom. There was a difference of 5.7% of Calibration Factor including attenuation and scatter effect between ABP and NEMA PET body phantom. Because it better reflects the attenuation and scatter effect, it is recommended to use a human-like inhomogeneous phantom for determination of CF instead of a homogeneous phantom.

On using steerable needles for the 3D printing of biomaterials

Steerable needles are often used in surgical operations (such as percutaneous intervention) as a relatively non-invasive approach in the treatment of certain diseases (e.g., cancer, etc.). The key advantage of this being that the needle tip can work its way through a body, avoiding all sensitive areas and / or obstacles, and ultimately reach an otherwise unreachable area (causing minimal damage). This work describes an approach to 3D printing utilizing steerable needles and defines a methodology through which biomaterial can be deposited and polymerized in place within a penetrable body to create a fibre of certain characteristics and / or behaviour. Using gelatine as the phantom body in which we 3D print with steerable needles, it is possible using a novel steerable needle experimental machine to deposit sodium alginate of a certain length in a particular orientation at certain points within the phantom and subsequently add calcium chloride to initiate polymerization into a calcium alginate fibre of certain properties. This article presents the engineering and software requirements to control a steerable needle with specific definition for 3D printing, the phantom within which we 3D print is defined, and finally calcium alginate fibers are offered, that are polymerized within the gelatine phantom. This work attempts to take a step towards the development of electro-mechanical devices which could in future allow for the 3D printing of fibers or other specific structures within the human body as part of the biomedical field.

Trade-off between breast dose and image quality using composite bismuth shields in computed tomography: A phantom study

IntroductionMany researchers have suggested that bismuth composite shields (BCS) reduce breast dose remarkably; however, the level of this reduction and its impact on image quality has not been assessed. This study aimed to evaluate the efficiency of nano- and micro- BCS in reducing the dose and image quality during chest computed tomography (CT) scans. Materials and methodsBismuth shields composed of 15 weighting percentage (wt%) and 20 wt% bismuth oxide (Bi2O3) nano- and micro-particles mixed in silicon rubber polymer were constructed in 1 and 1.5 mm thicknesses. The physical properties of nanoparticles were assessed using a scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX). Breast radiation doses were measured experimentally during chest CT using PMMA standard dosimetry phantom (body phantom, 76-419-4150, Fluke Biomedical) in the presence of the shields. The image quality was assessed by calculating signal and noise values in different regions. ResultsThe SEM images showed that the average size of Bi2O3 nano- and micro-particles was about 70 nm and 150 μm, respectively. The breast doses were reduced by increasing the shield thickness/bismuth weight percentage. The maximum dose reduction was related to the 20% weight of Bi2O3 nano-particles and a thickness of 1.5 mm. The minimum dose reduction was related to the 15% weight of Bi2O3 micro-particles with a thickness of 1 mm. The mean noise was higher in nano-particle bismuth shields than in micro-particles. ConclusionComposite shields containing bismuth nano- and micro-particles can reduce the breast dose during chest CT examinations while negatively impacting diagnostic image quality. Several critical factors, such as bismuth concentration, particle size, and shield thickness, directly affect the efficiency.

Low-profile high gain circularly polarized CRLH transmission line inspired antenna with artificial magnetic conductor for wearable applications

AbstractIn this work, a compact, wideband, circularly polarized wearable antenna is proposed using asymmetric coplanar strip feeding for wireless health monitor applications in the ISM frequency band. The proposed antenna consists of a composite right/left transmission line (CRLH TL) inspired structure to achieve compactness and a rectangular ring slot is created in the metallic ground to enhance the CP radiation of the antenna. A 5 × 5 artificial magnetic conductor unit cell-based metasurface is designed which is operating at 2.4 GHz as a ground plane for the CRLH-based CP antenna. Implementation of AMC-based metasurface as a ground plane results in enhancement of radiation characteristics of CRLH TL antenna. The proposed antenna has a small footprint of 50 × 50 mm2 with measured impedance bandwidth of 2.3–3.2 GHz. The 3 dB axial ratio bandwidth of the proposed antenna is 2.36–2.78 GHz with peak gain of 5.89 dBi. Simulation and experimental results show that proposed AMC-based antenna is robust in terms of structural deformation. Further, to validate the performance of the antenna for biomedical applications, we have simulated the proposed antenna with human phantom model. The proposed antenna exhibits stable scattering and radiation characteristics with the phantom body environment and due to the inclusion of AMC structure, the proposed design satisfies maximum specific absorption rate value given as per the IEEE standard safety guidelines.

Modeling the Effect of Hyperoxia on the Spin-Lattice Relaxation Rate R1 of Tissues.

PurposeInducing hyperoxia in tissues is common practice in several areas of research, including oxygen‐enhanced MRI (OE‐MRI), which attempts to use the resulting signal changes to detect regions of tumor hypoxia or pulmonary disease. The linear relationship between PO2 and R1 has been reproduced in phantom solutions and body fluids such as vitreous fluid; however, in tissue and blood experiments, factors such as changes in deoxyhemoglobin levels can also affect the ΔR1.Theory and MethodsThis manuscript proposes a three‐compartment model for estimating the hyperoxia‐induced changes in R1 of tissues depending on B0, SO2, blood volume, hematocrit, oxygen extraction fraction, and changes in blood and tissue PO2. The model contains two blood compartments (arterial and venous) and a tissue compartment. This model has been designed to be easy for researchers to tailor to their tissue of interest by substituting their preferred model for tissue oxygen diffusion and consumption. A specific application of the model is demonstrated by calculating the resulting ΔR1 expected in healthy, hypoxic and necrotic tumor tissues. In addition, the effect of sex‐based hematocrit differences on ΔR1 is assessed.ResultsThe ΔR1 values predicted by the model are consistent with reported literature OE‐MRI results: with larger positive changes in the vascular periphery than hypoxic and necrotic regions. The observed sex‐based differences in ΔR1 agree with findings by Kindvall et al. suggesting that differences in hematocrit levels may sometimes be a confounding factor in ΔR1.ConclusionThis model can be used to estimate the expected tissue ΔR1 in oxygen‐enhanced MRI experiments.

Impact of patient body habitus on image quality and quantitative value in bone SPECT/CT.

The first edition of guidelines for standardization of bone single photon emission computed tomography (SPECT) imaging was published in 2017, and the optimization and standardization are widely promoted. To the purpose, clarification of the factors related to image quality and quantitative values and their influence are required. The present study aimed to clarify and optimize the influence of patient body habitus on image quality and quantitative values in bone SPECT/CT. National Electrical Manufacturers Association body phantom (S-size) and custom-made large body phantoms (M-size and L-size) that simulate the abdomens of Japanese patients weighing 60, 80, and 100kg, were used. Each phantom was filled with 99mTc-solutions of 108 and 18kBq/mL for the hot spheres and background, respectively. Dynamic SPECT acquisition was performed for 6000s (150s /rotation × 40 rotation). The data were divided into six projection data and reconstructed each acquisition time (150, 300, 450, 600, 750, 900s, and single projection 6000s). Image quality was evaluated for contrast (QH, 17mm), background noise (NB, 17mm), contrast-to-noise ratio (CNR), maximum standardized uptake value (SUVmax, 17mm), and visual assessment for a 17mm hot sphere. Image quality in the 300s acquisition showed that values of QH, 17mm, CNR, and SUVmax, 17mm decreased (-16.7%, -11.8%, and -11.3%) for M-size and (-28.2%, -30.1%, and -21.7%) for L-size compared with S-size, respectively. No significant difference was observed in NB, 17mm values. M-size and L-size required 1.2 and 2.3 times longer acquisition, to achieve same CNR as S-size. In visual assessment, 17mm hot sphere could not be detected only in the L-size. When the Japanese bone SPECT guidelines criteria were applied in 600s, the sphere could be detected between all phantoms. Patient body habitus significantly affects image quality and decreases the quantitative value in bone SPECT/CT. For the optimization, extend acquisition time according to the patient body habitus is effective for image quality. And for the standardization, it is important to achieve imaging conditions that meet the Japanese bone SPECT guidelines criteria to ensure adequate detectability.

Wearable Electrical Impedance Tomography Belt With Dry Electrodes.

Electrical impedance tomography (EIT) is a noninvasive imaging technology used to reconstruct the conductivity distribution in objects and the human body. In recent years, numerous EIT systems and image reconstruction algorithms have been developed. However, most of these EIT systems require conventional electrodes with conductive gels (wet electrodes) and cannot be adapted to different body types, resulting in limited applicability. In this study, a wearable wireless EIT belt with dry electrodes was designed to enable EIT imaging of the human body without using wet electrodes. The specific design of the belt mechanism and dry electrodes provide the advantages of easy wear and adaptation to different body sizes. Additionally, the Gauss-Newton method was used to optimize the EIT image. Finally, experiments were performed on the phantom and human body to validate the performance of the proposed EIT belt. The results demonstrate that the proposed system can provide accurate location information of the objects in the EIT image and the system can be successfully applied for noninvasive measurement of the human body.

From the use of exposure index in quality control testing to the use of exposure index for quality control of clinical images

AimThe exposure index (EI) is used in routine quality control (QC) tests performed in the radiographic equipment installed in our hospitals. This study aimed at investigating the factors affecting the calculation of EI in QC and clinical images, and the implementation of target EI (EIT) and deviation index (DI) in clinical practice. MethodsThe EI is 100 times the incident air kerma (IAK) in μGy on the image receptor, using the RQA-5 X-ray beam quality. Conformance to this relationship was investigated in QC images and clinical images acquired using anthropomorphic phantom body parts and different examination protocols, tube potential settings and radiation field sizes. Furthermore, a survey on EIT and DI data from clinical images was performed. ResultsThough automatic exposure control (AEC) systems have been adjusted for an IAK of 2.5 μGy, for most anthropomorphic phantom images the EIs were far from 250, depending on the manufacturer, the anatomy imaged, and the examination protocol. Regarding the survey results, DI calculation was feasible in only 38 % of the systems, since for the rest EIT values have not been set. However, the rationale based on which EIT have been selected is unclear. Some systems use only one while others many different EIT values. ConclusionBefore using EI for quality control of clinical images image all receptors and AEC systems should be properly calibrated. Then, the methodology of selecting appropriate EIT should be refined, since the EI calculation may vary, depending on the manufacturer, the anatomy imaged, and the examination protocol.

Wearable Pattern-Diversity Dual-Polarized Button Antenna for Versatile On-/Off-Body Communications

A wearable dual-port button antenna that excites pattern-diversity dual-polarized waves is proposed for on-/off-body applications. Its simple structure comprises of two radiators and a common ground plane designed into two substrates. The crossed-dipole radiator is made by two symmetric bowtie dipoles printed on a circular-shaped semi-rigid substrate, which covers an ultra-wideband (UWB) application with circular polarization and directional radiation patterns, high gain, and high efficiency suitable for off-body communication. The annular-ring radiator and common ground plane are made by a conductive textile on the square-shaped flexible-felt substrate. The annular-ring radiator is shorted to the ground plane using four vias, which generates triple TM modes covering the 2.45/5.85 GHz wireless body area networks (WBAN) with omni-directional radiation patterns and a 3.8 GHz C-band with a directional radiation pattern suitable for on-/off-body communications. The fabricated antenna is verified by measurement in both free space and phantom body environment. Measurements agreed well with simulations. Simulated specific absorption rates (SARs) under US and EU standards are below the safe level, making the proposed antenna suitable for on-/off-body communications.

Novel Compact UWB Band Notch Antenna Design for Body-Centric Communications

In this paper, a novel and compact ultra-wideband (UWB) antenna with band-notched characteristics for body-centric communication is examined and implemented. The shape of the designed antenna looks like a ‘swan’ with a slotted patch. The performance parameters of this antenna for both the free space and on-body scenario for body-centric communication are analyzed and investigated through the simulation process using Computer Simulation Technology (CST). This antenna can avoid the interference caused by Wireless Local Area Network (WLAN) (5.15–5.825 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (5.25–5.85 GHz) systems with a band notch because of newly designed UWB antenna is revised small form factor sized. At first, the performance parameters like return loss response, gain, radiation patterns, and radiation efficiency on the free space of this UWB antenna are evaluated. After that, the on-body performance parameters of the antenna are also examined to place the antenna at various distances like 2 mm, 4 mm, 6 mm, 8 mm, and 10 mm away from 3-layers of phantom body model at frequencies of 3.5 GHz, 5.2 GHz, 5.8 GHz, 8 GHz, and 10 GHz. All the on-body performance parameter results are compared and analyzed with free space performance parameter results. Lastly, by changing patch slot length and ground plane length, parametric studies were done for performance comparison. Due to its compact size, novel shape and significant on-body performance, the proposed antenna is very suitable for multi-purpose healthcare applications and sports performance monitoring.

3D-printed patient-specific pelvis phantom for dosimetry measurements for prostate stereotactic radiotherapy with dominant intraprostatic lesion boost.

Developing and assessing the feasibility of using a three-dimensional (3D) printed patient-specific anthropomorphic pelvis phantom for dose calculation and verification for stereotactic ablative radiation therapy (SABR) with dose escalation to the dominant intraprostatic lesions. A 3D-printed pelvis phantom, including bone-mimicking material, was fabricated based on the computed tomography (CT) images of a prostate cancer patient. To compare the extent to which patient and phantom body and bones overlapped, the similarity Dice coefficient was calculated. Modular cylindrical inserts were created to encapsulate radiochromic films and ionization chamber for absolute dosimetry measurements at the location of prostate and at the boost region. Gamma analysis evaluation with 2%/2mm criteria was performed to compare treatment planning system calculations and measured dose when delivering a 10 flattening filter free (FFF) SABR plan and a 10FFF boost SABR plan. Dice coefficients of 0.98 and 0.91 were measured for body and bones, respectively, demonstrating agreement between patient and phantom outlines. For the boost plans the gamma analysis yielded 97.0% of pixels passing 2%/2mm criteria and these results were supported by the chamber average dose difference of 0.47±0.03%. These results were further improved when overriding the bone relative electron density: 97.3% for the 2%/2mm gamma analysis, and 0.05±0.03% for the ionization chamber average dose difference. The modular patient-specific 3D-printed pelvis phantom has proven to be a highly attractive and versatile tool to validate prostate SABR boost plans using multiple detectors.

Modelo Phantom e índices de proporcionalidad en categorías de edad de gimnasia acrobática: un estudio transversal y descriptivo

Introducción: El objetivo de este estudio fue analizar la proporcionalidad corporal a través de la estrategia Phantom y de los índices corporales, en las diferentes categorías de edad que conforman la competición reglada en este deporte, en sus dos roles fundamentales de ágil y portor. Material y métodos: Estudio transversal y descriptivo. La población de estudio la formaron los gimnastas de nivel nacional. El criterio de selección fue la participación en campeonatos de España. Se excluyeron aquellos de nivel inferior y no ser de sexo femenino. Se evaluó la proporcionalidad corporal mediante la estrategia Phantom e índices corporales, como el índice ponderal, la longitud relativa de las extremidades superiores, índice esquelético, índice córmico, índice acromio ilíaco y la envergadura relativa. Se realizó un análisis comparativo general y múltiple entre categorías de edad.Resultados: Muestra de n=54 ágiles (edad (X)=11,23años; DT=0, 7 infantiles (mnastas alevines (7,28 rol de ,11 años años; DE =3,04) y n=75 portoras (X=14,46¡ños; DT=0, 7 infantiles (mnastas alevines (7,28 rol de ,11 años años; DE=2,08) de sexo femenino distribuidas en categoría alevín, infantil, cadete, juvenil, junior y senior. En las gimnastas ágiles destacan las diferencias entre grupos en los valores phantom de proporcionalidad del peso (p= ,032), y diámetros del húmero (p= ,034), muñeca (p= ,002) y fémur (p= ,004). Así como en los índices de proporcionalidad de la longitud relativa de las extremidades superiores (p= ,016), índice esquelético (p= ,008), e índice córmico (p= ,008). En las portoras entre las diferencias generales destacan los valores phantom del peso (p= ,008), perímetro abdominal (p= ,045), glúteo (p= ,001) y brazo relajado (p= ,015), mientras que en los índices solo arroja diferencias el índice acromio ilíaco (p= ,008).Conclusiones: No existen demasiadas diferencias significativas en la proporcionalidad antropométrica entre los grupos de edad en ninguno de los roles estudiados. No pudiendo establecer una clara evolución gradual de estas. Sin embargo, el conocer la proporcionalidad y sus especificidades, permiten realizar una buena detección de talentos.

Aberration-inducing body wall phantom for high-intensity focused ultrasound applications

Aberrations induced by soft tissue inhomogeneities distort acoustic fields and often complicate HIFU therapies. An aberration-generating phantom was designed and fabricated to mimic the acoustic effects of a porcine body wall. A rippled surface pattern replicating inhomogeneities of size scales relevant to the porcine body wall was transferred to a large phantom made of fat-like and muscle-like gel materials. The acoustic distortions produced by the phantom and an ex vivo porcine body wall were characterized by hydrophone measurements with a 256-element 1.5 MHz focused ultrasound array (diameter = 144 mm, F# = 0.83). Insertion of the phantom generated large distortions for both linear and nonlinear beam focusing including displacement of the focus (up to 0.3 mm transversely), enlargement of the focal region, and reduction in focal pressures due to aberration (up to 2.5-fold peak positive pressure reduction). The phantom and porcine body wall produced similar levels of aberration and attenuation effects. An aberration correction approach was leveraged to isolate the quantitative effect of aberration and to restore shocks in nonlinear waveforms in the focus. Boiling histotripsy treatments through the phantom or body wall were subsequently demonstrated in a hematoma sample. [This work was supported by NIH R01EB7643 and R01EB25187, and RSF 20-12-00145.]

Wearable Dual-Band High-Gain Low-SAR Antenna for Off-Body Communication

A wearable dual-band folded-ring antenna, that has directional radiation pattern and offers high-gain, high-efficiency, and low-specific absorption rate (SAR) performance, is presented for 2.45/3.45 GHz off-body communication. The proposed antenna is comprised of two substrates; a folded-ring antenna as a main radiator is printed on a low-loss rigid substrate and a conductive textile is attached to a felt substrate. The conductive textile is used as the ground plane and as a protective shield to prevent incidental electromagnetic waves from propagating toward the human body. The felt substrate provides a comfortable surface for wearers. The antenna performance is verified and shows very good agreement both in free space and on phantom body environment. The measured bandwidths of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> on human body are 5.76% and 4.7% at each frequency band. The maximum broadside gains within the operating bandwidth are 5.1 and 8.6 dB, respectively. The measured radiation efficiencies on human phantom are 91% and 94%, respectively. The SAR values at lower mode based on US and EUR standards under 1 g average and 10 g average are 0.2 and 0.1 W/kg, respectively. At higher mode, the SAR values are 0.1 and 0.04 W/kg, respectively.

A gamma radiation exposure risk assessment using Monte Carlo simulation and an adult anthropomorphic phantom

The human body is vulnerable to exposure to ionizing radiation permanently. These radiations can be of natural origin such as soil and space, or of artificial and medical origins etc. Despite the great benefits that come from the applications of ionizing radiation in human life can turn at any time into threats to the life of the population once there is serious exposure to ionizing radiation. The aim of this work is to assess the risks of exposure by gamma radiation using the Monte Carlo simulation and an anthropomorphic phantom. This study is carried out on gamma rays received from the cobalt-60 irradiator of the National Institute of Agronomic Research (NIAR) Tangier / Morocco. With the code Geant4 we calculate the absorbed dose by the whole phantom body placed in front of the gamma irradiator inside the NIAR ionization cell. Dose calculations are made as a function of three parameters: phantom-irradiator distance, exposure time and as a function of gamma irradiator activity. The results clearly show that the dose absorbed and thus the danger of irradiation decreases by increasing the phantom-source distance, and by reducing the exposure time and the activity of the cobalt-60 source.

Gain‐enhancement technique for wearable patch antenna using grounded metamaterial

In this study, a metamaterial (MTM)-based high-gain compact-wearable antenna for 2.45 GHz industrial, scientific and medical radio band application has been proposed. To achieve the flexibility of the antenna, textile material felt fabric has been chosen as the substrate of the antenna as well as MTM. An omega (Ω) like structure has been taken as MTM unit cell design. High value of permeability is utilised for the gain enhancement of the antenna. In addition, very low specific absorption rate (SAR) is obtained using the MTM which makes the proposed antenna suitable for the biomedical application. The proposed antenna has achieved about 3 dB gain enhancement along with SAR value of 0.405 W/kg (1 g tissue). The design has been optimised and the prototype with the optimised parameter has been fabricated and tested over the semi-solid phantom and human body. Further, the proposed antenna over different type of textile material has also been validated.

Discussion of “Phantom Penis: Extrapolating Neuroscience and Employing Imagination for Trans Male Embodiment”

ABSTRACT Straayer synthesizes literary and scientific discourse on the trans phantom penis, presenting a compelling argument for greater roles of diversity and imagination in its conceptualization. In this response I first introduce a recently uncovered historical reference to phantom genitals that precedes those discussed by Straayer and that extends the trans phantom penis beyond the Western canon. I next compare what is known about the sensory and cortical origins of the trans phantom penis with the sparse scientific research on phantom breasts and vaginas. Finally, I elaborate on Straayer’s suggestion that sociology be considered in research on trans phantom body parts, illustrating the role of social factors both in phantom body parts and in scientific understandings of sex and gender.

Control of Insertion of Indenter into Viscoelastic Tissue using a Piezoelectric Drive

Stereotactic operations are actively used in modern minimally invasive medicine. During such operations, a flexible needle is inserted into the internal organs, with the help of which a biopsy or a local treatment is performed. The applica tion of such approaches in neurosurgery requires the accurate positioning of the needle tip at the target point. The present study is related to the creation of a robotic system that delivers the needle to a given point and uses drives compatible with magnetic resonance imaging devices that visualize the position of the needle. In this paper, we propose a finite-dimensional mathematical model of a mechatronic system that uses a piezoelectric drive (PED) to move the needle (cannula) along a given line. To describe the contact between the cannula and the soft tissue, a mathematical model of their interaction is developed. The contact problem involving two processes occurring during the introduction of the needle into the biological tissue is solved: the introduction of a rigid (compared to the tissue) indenter and its retention at a certain depth. Relaxation properties of the tissue are taken into account. The behavior of tissue is described using a phenomenological approach based on a modified Kelvin-Voigt model. This allowed for reducing the solution of the contact problem to the integration of a system of ordinary differential equations. One of recognized ways to develop medical robotic systems is to test their functioning using phantoms of biological tissues. For this purpose, a phantom of a porcine brain based on agar-agar is made. Experiments are carried out to indent a standard cannula into the phantom body. Based on the obtained experimental data, the parameters of the contact model are identified. An algorithm is proposed for controlling the PED frequency, which ensures the introduction of the cannula into the soft biological tissue to a given depth. Numerical simulation of the insertion of the cannula into the soft tissue using this algorithm is performed. The influence of feedback coefficients on the position and speed of the indenter on the nature of the implementation process is investigated.