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Artificial Human Phantoms: Human proxy in testing microwave apparatus that have electromagnetic interaction with the human body

A. T. Mobashsher, A. M. Abbosh

arXiv:1503.05964v2physics.med-ph

TL;DR

Microwave-device testing needs realistic, controlled validation, but human testing and simplified models have constraints. This review surveys ATE materials, fabrication, phantom types, and applications; it concludes that the synthesis can inform new phantom design while identifying limitations and research directions.

  • Problem

    Microwave systems interacting with the body need controlled performance and safety validation, while simulations cannot reflect realistic environmental interference and human testing raises safety and ethical concerns.

    Source: §I · p. 1

  • Method

    The review classifies ATE materials and surveys phantom types, fabrication procedures, applications, and limitations across body parts and operating frequencies.

    Source: §VII · pp. 12–13

  • Results

    Reported phantom choices vary by application: liquid and gel head phantoms are used for SAR and hyperthermia, while heterogeneous semi-solid phantoms are popular for implants and microwave imaging.

    Source: A. Head Phantoms · p. 8

  • Takeaways & Limitations

    The synthesis is intended to inform fabrication of more efficient phantoms for current and future electromagnetic-interaction applications.

    Source: §VII · pp. 12–13

    3D-printed phantom fabrication remains constrained by limited substrate choices and can require time-consuming shells or molds.

    Source: D. Three-Dimensional Printing and CT… · p. 12

Abstract

from arXiv · show

In this manuscript, an effort is made in this review to address different state-of-the-art artificial tissue emulating (ATE) materials and phantom types for various operating frequencies, and fabrication procedures in order to have a better understanding of the pros and cons of various ATE phantoms which leads us to develop superior version of artificial human body substitute for various applications.

I. INTRODUCTION

ATE phantoms enable controlled evaluation of microwave devices because simulations and human testing cannot fully provide realistic, repeatable, and safe validation. The section outlines their use in dosimetry, imaging, and implantable-device testing.

I. INTRODUCTION

  • Human testing introduces safety, ethical, and physiological uncertainties, while ATE phantoms support controlled testing across operating scenarios before clinical trials.The introduction also notes that SAR and hyperthermia experiments may require monitoring power intensity and temperature inside tissues.Source: §I · p. 1

A. Dosimetric Studies

  • Sensor-based SAR estimation requires probes to move inside the phantom, making liquid and gel ATE materials especially suitable for those measurements.Temperature-based approaches can use different phantom types depending on sensor placement and whether the phantom can be separated for thermographic imaging.Source: A. Dosimetric Studies · p. 3

B. Microwave Imaging

  • Microwave imaging test beds use ATE phantoms with realistic tissue properties and distributions to validate systems for detecting abnormalities in body parts.Examples include breast and head phantom imaging experiments.Source: B. Microwave Imaging · p. 3

C. Implantable Devices

  • ATE phantoms let researchers assess implantable-device performance and potential hazards, including heat generation and device failure, before clinical trials.The passage connects preclinical evaluation with assessing reliable data transfer, optimal operation, and safety.Source: C. Implantable Devices · pp. 3–4

D. Body-worn Sensors & Devices

ATE phantoms support repeatable evaluation of wearable systems and other microwave applications. The section classifies materials by physical form and describes liquid-material fabrication and constraints.

D. Body-worn Sensors & Devices

  • ATE phantoms provide repeatable analysis of body-worn device wave propagation and overall performance under body-related channel conditions.On-body communication links wearable devices or sensors, while off-body communication links a wearable device to a nearby base or mobile unit.Source: D. Body-worn Sensors & Devices · p. 4

E. Other Applications

  • ATE phantoms are used to verify hyperthermia apparatus, handheld-device antennas, microwave radiometry, and noninvasive blood-glucose monitoring.Hyperthermia studies examine electrical and thermal heat deposition.Source: E. Other Applications · p. 4

III. TYPES OF ATE MATERIALS

  • The review divides ATE materials into liquid, gel, semi-solid, and solid types to compare their advantages and disadvantages.This physical-form classification complements classification by water content and relates material choice to tissue emulation suitability.Source: §III · p. 4

A. Liquid ATE Materials

  • Liquid ATE mixtures are prepared by combining ingredients, with gentle early heating speeding solution preparation while temperature monitoring limits water evaporation.Low-permittivity tissues can be emulated with low-water recipes, oil-in-water emulsions, or salted water with nonionic surfactants.Source: A. Liquid ATE Materials · p. 5
  • Liquid mixtures can dehydrate or develop mold, and component separation can require renewed stirring; containers can also obstruct invasive tests and affect imaging through scattering.Dehydration can alter relative permittivity and conductivity, while unsuitable container electrical properties may jeopardize microwave-imaging validity.Source: A. Liquid ATE Materials · p. 5

B. Gel ATE Materials

Gel materials offer easier handling than liquids but retain some liquid-material weaknesses. Semi-solid materials can form layered tissue-like phantoms, though invasive measurements and long-term reuse remain constrained.

B. Gel ATE Materials

  • Gel ATE mixtures resist liquid-component separation and retain homogeneity, but need a container or shell to hold their shape.Fabrication uses controlled rotation as the mixture thickens before it is poured into a phantom container.Source: B. Gel ATE Materials · p. 5
  • Gel setting time can vary up to 1 day, potentially disrupting rapid phantom prototyping and system validation.Air bubbles may also become trapped during continuous rotation, so slow, consistent rotation is advised near the end of fabrication.Source: B. Gel ATE Materials · p. 6

C. Semi-solid or Jelly ATE Materials

  • Semi-solid materials conform to shapes and resist osmosis between adjacent layers, supporting multilayer phantoms with stable electrical properties.Gelatin, agar, or dough can provide castability and non-diffusive behavior while helping adjust electrical properties.Source: C. Semi-solid or Jelly ATE Materials · p. 6
  • Semi-solid materials are relatively low-cost and mimic tissues across wide frequency bands, but layer deformation complicates invasive measurements such as SAR, implant, and hyperthermia tests.They are usually neither reusable nor dielectrically adjustable and tend to dehydrate, making long-term preservation difficult,.Source: C. Semi-solid or Jelly ATE Materials · p. 6

D. Solid ATE Materials

The review contrasts solid ATE materials with other phantom types and surveys reported head phantoms and their applications. It also notes scope boundaries and limits in reported phantom lifetime information.

D. Solid ATE Materials

  • Solid ATE materials avoid hydration drawbacks and can separately tune permittivity and conductivity, but ceramic fabrication is costly and requires specialized equipment.Ceramic materials are low-loss; conductive additives help address the challenge of emulating tissue conductivity, while adhesive joints can make phantoms difficult to cut or reshape.Source: D. Solid ATE Materials · pp. 6–7

IV. ATE PHANTOMS

  • The phantom survey covers body-part phantoms across narrow and wide frequency ranges but excludes CT phantoms whose electrical properties are not considered..Source: §IV · p. 7

A. Head Phantoms

  • Reported head phantoms include liquid, gel, semi-solid, and solid forms; homogeneous liquid and gel or heterogeneous semi-solid head phantoms are used in SAR, hyperthermia, implant, and imaging applications.Solid head phantoms are mainly narrowband, while a broadband solid material has been reported for the UHF band; head phantom shelf-life reporting is often insufficient.Source: A. Head Phantoms · pp. 7–8
  • Some semi-solid head phantoms have shown 2-5% changes over 4 weeks,,,,.The review contrasts this with one liquid tissue reported to last over one year and gel dielectric consistency over 40 days.Source: A. Head Phantoms · pp. 8–9

B. Breast Phantoms

The review surveys breast, limb, and torso phantoms, describing their applications, construction, frequency coverage, and reported limitations.

B. Breast Phantoms

  • Breast phantoms mainly support microwave breast-cancer imaging; MRI-derived heterogeneous molds reproduce anatomy, while oil-gelatin versions last up to 8 weeks and Triton X-100/water mixtures about one year.Most reported breast phantoms are designed for wideband operation; solid versions are less widely adopted because their dielectric properties are non-dispersive.Source: B. Breast Phantoms · p. 9

C. Limb Phantoms

  • Limb phantoms serve broadband applications from a few kHz to tens of GHz, are usually homogeneous, and have reported lifetimes of 2 to 4 weeks.Some limb phantoms are heterogeneous, and applications include electrical impedance tomography, hyperthermia, and wearable communications.Source: C. Limb Phantoms · p. 9

D. Torso Phantoms

  • Torso phantoms support hyperthermia, SAR studies, and monitoring validation, using heterogeneous structures or tissue recipes that can be adapted from other ATE phantoms.Agar-based semi-solid materials can maintain soft-body-tissue-equivalent mechanical strength.Source: D. Torso Phantoms · pp. 9–10

V. FEATURES AND FUNCTIONS OF INGREDIENTS IN ATE MATERIALS

Ingredient composition shapes ATE materials’ physical, mechanical, and dielectric properties, while future work is expected to continue developing phantoms for accurate validation of body-centric wireless systems and devices.

V. FEATURES AND FUNCTIONS OF INGREDIENTS IN ATE MATERIALS

  • Changing ingredient proportions can control dielectric properties across a wide range, while adding or reducing ingredients can alter physical and mechanical characteristics.Muscle-mimicking materials described for head phantoms can also be applied to other body parts.Source: §V · p. 10

VI. FUTURE TRENDS OF ATE PHANTOMS

  • ATE phantom development is expected to evolve as demand grows for accurate validation of body-centric in vivo and in vitro wireless systems and devices.The review identifies issues researchers still need to address or implement for that validation.Source: §VI · p. 10

A. Age-dependent Phantoms

Age-dependent phantom research remains limited: tissue-property data are insufficient, child models raise validation concerns, and pregnancy-specific ATE phantoms are not yet reported for dosimetry.

A. Age-dependent Phantoms

  • Age-related tissue changes reflect variation in water content and organic composition, but sufficient data for age-dependent human tissue analysis are unavailable.Researchers have analyzed age-dependent dielectric changes in rats and pigs and proposed numerical estimates for human tissue properties.Source: A. Age-dependent Phantoms · p. 10
  • Dosimetric simulations report higher average brain radiation exposure in children than adults owing to anatomical differences, while age-dependent ATE phantoms are rarely reported.The reported child and adult models consider age-dependent tissue properties and MRI-scan-based child anatomy.Source: A. Age-dependent Phantoms · pp. 10–11
  • Scaling adult head models down can introduce substantial uncertainty, so applications involving children should be verified with age-dependent child ATE phantoms.The review notes that inaccurate validation may matter in clinical diagnosis, therapy, or patient monitoring.Source: A. Age-dependent Phantoms · p. 11
  • Fetal tissue-property estimates rely on assumptions when fetal and pregnancy-specific data, including placenta data, are absent, and pregnancy-specific ATE phantoms remain unreported in dosimetry research.Some reported fetal electrical and thermal properties are also uncertain.Source: A. Age-dependent Phantoms · p. 11

B. Thermal Properties

Temperature-focused applications require phantoms to match tissue thermal properties as well as electrical properties, but fabrication and validation complexity has limited reported examples; breast blood-flow emulation is also unreported.

B. Thermal Properties

  • Temperature-focused ATE materials need tissue-equivalent temperature distributions alongside electrical properties, with thermal parameters suited to the application; few phantoms address these demands in detail.A large time constant can preserve temperature distributions long enough for measurement, and high-water-content tissues have higher specific heat and thermal conductivity than low-water-content tissues.Source: B. Thermal Properties · p. 11
  • Breast phantoms that emulate blood-flow circulation for thermoregulation and cooling during hyperthermia or other therapy have not been reported.Source: B. Thermal Properties · p. 11

C. Thermal Dependencies of Dielectric Properties

Tissue dielectric properties vary with temperature, making room-temperature-only phantom properties unsuitable for temperature-dependent applications. Few ATE materials with temperature-dependent dielectric properties are reported.

C. Thermal Dependencies of Dielectric Properties

  • Tissue electrical properties vary with temperature, mainly because tissue water concentrations differ across temperatures.[45],Source: C. Thermal Dependencies of Dielectric… · p. 12
  • Phantoms based on electrical properties measured at one temperature, usually room temperature, are unsuitable for temperature-related applications.They cannot realistically estimate tissue interaction with electromagnetic waves or thermal response to accumulated electromagnetic power.Source: C. Thermal Dependencies of Dielectric… · p. 12
  • Very few ATE materials with temperature-dependent dielectric properties are reported, despite their relevance to ablation and electromagnetic hyperthermia.Temperature-related changes could significantly alter targeting, such as tumor focusing in hyperthermia, and make the system vulnerable to errors.Source: C. Thermal Dependencies of Dielectric… · p. 12

D. Three-Dimensional Printing and CT Verification

3D printing supports small-scale fabrication of complex phantom structures, but limited substrate choices leave researchers relying on time-consuming shells and molds. Fabrication errors and air bubbles motivate CT verification.

D. Three-Dimensional Printing and CT Verification

VII. CONCLUSION

The review surveys artificial phantoms and ATE materials for body-centric wireless-device validation, organizing materials by physical type and phantoms by body part and operating band. It compares material trade-offs, summarizes fabrication ingredients, and discusses limitations and future directions.

VII. CONCLUSION

  • The review classifies ATE materials as liquid, gel, semi-solid, or solid and qualitatively compares their advantages.Source: §VII · p. 12
  • Reported head, breast, limb, and torso phantoms are discussed by characteristics and intended applications, with summaries organized by operating band.Source: §VII · p. 12
  • The review lists the features and functions of main fabrication ingredients and aims to inform phantom fabrication for current and future applications.The applications rely on interactions between electromagnetic fields and specific body parts.Source: §VII · pp. 12–13
  • The review discusses existing phantom limitations and future directions, including breakthroughs requiring coordinated work across scientific disciplines.The stated aim is to support rigorous safety and performance validation of microwave devices and systems.Source: §VII · p. 13
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