Characterization of a soft tissue-mimicking agar/wood powder material for MRgFUS applications

Drakos, Theocharis; Giannakou, Marinos; Menikou, Georgios; Constantinides, Georgios; Damianou, Christakis

doi:10.1016/j.ultras.2021.106357

Cited by 20 publications

(25 citation statements)

References 42 publications

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“…Figure 1b shows the composition of the corresponding materials used in each insert. The preparation process of the phantoms was previously described in detail 3 …”

Section: Methodsmentioning

confidence: 99%

“…The preparation process of the phantoms was previously described in detail. 3 Three phantoms with varying agarose (Merck KGaA, EMD Millipore Corporation, Darmstadt, Germany) concentrations of 2%-6% weight per volume (w/v) were prepared to assess the role of agar as a modifier of the relaxation times. The effect of varying silicon dioxide (Sigma-Aldrich, St. Louis, Missouri, United States) concentration (2%-6% w/v) on the relaxation times was then investigated using a certain amount of 6% w/v agar.…”

Section: Phantoms' Developmentmentioning

confidence: 99%

“…3 Thereby, another phantom containing 2% w/v agar and 4% w/v wood powder was constructed according to the procedure previously described by our group. 3…”

Section: Phantoms' Developmentmentioning

confidence: 99%

“…25 We have previously proposed and characterized several agar-based phantoms by estimating critical tissue properties, including the mass density, speed of sound, acoustic attenuation, acoustic impedance, thermal diffusivity, specific heat, and thermal conductivity. 3,14,29 Given the current need for TMPs that can also replicate critical MR parameters, as well as the lack of targeted research on trends between added ingredients and resultant MR properties of agar phantoms, we have investigated the MR relaxation times of different mixtures of agar-based phantoms previously proposed by our group. 3,14…”

Section: Introductionmentioning

confidence: 99%

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MR relaxation times of agar‐based tissue‐mimicking phantoms

Antoniou

Georgiou

Christodoulou

et al. 2022

J Applied Clin Med Phys

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Agar gels were previously proven capable of accurately replicating the acoustical and thermal properties of real tissue and widely used for the construction of tissue-mimicking phantoms (TMPs) for focused ultrasound (FUS) applications. Given the current popularity of magnetic resonance-guided FUS (MRgFUS), we have investigated the MR relaxation times T1 and T2 of different mixtures of agar-based phantoms. Nine TMPs were constructed containing agar as the gelling agent and various concentrations of silicon dioxide and evaporated milk. An agar-based phantom doped with wood powder was also evaluated. A series of MR images were acquired in a 1.5 T scanner for T1 and T2 mapping. T2 was predominantly affected by varying agar concentrations. A trend toward decreasing T1 with an increasing concentration of evaporated milk was observed. The addition of silicon dioxide decreased both relaxation times of pure agar gels.The proposed phantoms have great potential for use with the continuously emerging MRgFUS technology. The MR relaxation times of several body tissues can be mimicked by adjusting the concentration of ingredients, thus enabling more accurate and realistic MRgFUS studies.

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“…Figure 1b shows the composition of the corresponding materials used in each insert. The preparation process of the phantoms was previously described in detail 3 …”

Section: Methodsmentioning

confidence: 99%

Section: Phantoms' Developmentmentioning

confidence: 99%

“…3 Thereby, another phantom containing 2% w/v agar and 4% w/v wood powder was constructed according to the procedure previously described by our group. 3…”

Section: Phantoms' Developmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

MR relaxation times of agar‐based tissue‐mimicking phantoms

Antoniou

Georgiou

Christodoulou

et al. 2022

J Applied Clin Med Phys

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“…The agar-based phantom was prepared with 6% weight per volume (w/v) agar (Merck KGaA; EMD Millipore Corporation) according to a procedure previously described in the literature. 19 The selection of agar as the gelling agent was based on several factors such as the ease and low cost preparation process of agar-based phantoms, as well as their tissue-like MRI signal. 20 It is noted that during phantom production, the mixture was carefully dissolved…”

Section: Mri Compatibilitymentioning

confidence: 99%

Robotic system for top to bottom MRgFUS therapy of multiple cancer types

Antoniou

Giannakou

Evripidou

et al. 2022

Robotics Computer Surgery

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Background: A robotic system for Magnetic Resonance guided Focussed Ultrasound (MRgFUS) therapy of tumours in the breast, bone, thyroid, and abdomen was developed.Methods: A special C-shaped structure was designed to be attached to the table of conventional magnetic resonance imaging (MRI) systems carrying 4 computercontrolled motion stages dedicated to positioning a 2.75 MHz spherically focussed transducer relative to a patient placed in the supine position. The developed system was evaluated for its MRI compatibility and heating abilities in agar-based phantoms and freshly excised tissue.Results: Compatibility of the system with a clinical high-field MRI scanner was demonstrated. FUS heating in the phantom was successfully monitored by magnetic resonance thermometry without any evidence of magnetically induced phenomena.Cigar-shaped discrete lesions and well-defined areas of overlapping lesions were inflicted in excised tissue by robotic movement along grid patterns. Conclusions:The developed MRgFUS robotic system was proven safe and efficient by ex-vivo feasibility studies.

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Tumor phantom model for MRI‐guided focused ultrasound ablation studies

Antoniou,

Evripidou,

Georgiou

et al. 2023

Medical Physics

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BackgroundThe persistent development of focused ultrasound (FUS) thermal therapy in the context of oncology creates the need for tissue‐mimicking tumor phantom models for early‐stage experimentation and evaluation of relevant systems and protocols.PurposeThis study presents the development and evaluation of a tumor‐bearing tissue phantom model for testing magnetic resonance imaging (MRI)‐guided FUS (MRgFUS) ablation protocols and equipment based on MR thermometry.MethodsNormal tissue was mimicked by a pure agar gel, while the tumor simulator was differentiated from the surrounding material by including silicon dioxide. The phantom was characterized in terms of acoustic, thermal, and MRI properties. US, MRI, and computed tomography (CT) images of the phantom were acquired to assess the contrast between the two compartments. The phantom's response to thermal heating was investigated by performing high power sonications with a 2.4 MHz single element spherically focused ultrasonic transducer in a 3T MRI scanner.ResultsThe estimated phantom properties fall within the range of literature‐reported values of soft tissues. The inclusion of silicon dioxide in the tumor material offered excellent tumor visualization in US, MRI, and CT. MR thermometry revealed temperature elevations in the phantom to ablation levels and clear evidence of larger heat accumulation within the tumor owing to the inclusion of silicon dioxide.ConclusionOverall, the study findings suggest that the proposed tumor phantom model constitutes a simple and inexpensive tool for preclinical MRgFUS ablation studies, and potentially other image‐guided thermal ablation applications upon minimal modifications.

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Characterization of a soft tissue-mimicking agar/wood powder material for MRgFUS applications

Cited by 20 publications

References 42 publications

MR relaxation times of agar‐based tissue‐mimicking phantoms

MR relaxation times of agar‐based tissue‐mimicking phantoms

Robotic system for top to bottom MRgFUS therapy of multiple cancer types

Tumor phantom model for MRI‐guided focused ultrasound ablation studies

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