1
|
Antoniou A, Evripidou N, Damianou C. Focused ultrasound heating in brain tissue/skull phantoms with 1 MHz single-element transducer. J Ultrasound 2024; 27:263-274. [PMID: 37517052 PMCID: PMC11178743 DOI: 10.1007/s40477-023-00810-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Accepted: 07/09/2023] [Indexed: 08/01/2023] Open
Abstract
PURPOSE The study aims to provide insights on the practicality of using single-element transducers for transcranial Focused Ultrasound (tFUS) thermal applications. METHODS FUS sonications were performed through skull phantoms embedding agar-based tissue mimicking gels using a 1 MHz single-element spherically focused transducer. The skull phantoms were 3D printed with Acrylonitrile Butadiene Styrene (ABS) and Resin thermoplastics having the exact skull bone geometry of a healthy volunteer. The temperature field distribution during and after heating was monitored in a 3 T Magnetic Resonance Imaging (MRI) scanner using MR thermometry. The effect of the skull's thickness on intracranial heating was investigated. RESULTS A single FUS sonication at focal acoustic intensities close to 1580 W/cm2 for 60 s in free field heated up the agar phantom to ablative temperatures reaching about 90 °C (baseline of 37 °C). The ABS skull strongly blocked the ultrasonic waves, resulting in zero temperature increase within the phantom. Considerable heating was achieved through the Resin skull, but it remained at hyperthermia levels. Conversely, tFUS through a 1 mm Resin skull showed enhanced ultrasonic penetration and heating, with the focal temperature reaching 70 °C. CONCLUSIONS The ABS skull demonstrated poorer performance in terms of tFUS compared to the Resin skull owing to its higher ultrasonic attenuation and porosity. The thin Resin phantom of 1 mm thickness provided an efficient acoustic window for delivering tFUS and heating up deep phantom areas. The results of such studies could be particularly useful for accelerating the establishment of a wider range of tFUS applications.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus.
| |
Collapse
|
2
|
Sofokleous P, Damianou C. High-quality Agar and Polyacrylamide Tumor-mimicking Phantom Models for Magnetic Resonance-guided Focused Ultrasound Applications. J Med Ultrasound 2024; 32:121-133. [PMID: 38882616 PMCID: PMC11175378 DOI: 10.4103/jmu.jmu_68_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2023] [Revised: 07/04/2023] [Accepted: 07/13/2023] [Indexed: 06/18/2024] Open
Abstract
Background Tissue-mimicking phantoms (TMPs) have been used extensively in clinical and nonclinical settings to simulate the thermal effects of focus ultrasound (FUS) technology in real tissue or organs. With recent technological developments in the FUS technology and its monitoring/guided techniques such as ultrasound-guided FUS and magnetic resonance-guided FUS (MRgFUS) the need for TMPs are more important than ever to ensure the safety of the patients before being treated with FUS for a variety of diseases (e.g., cancer or neurological). The purpose of this study was to prepare a tumor-mimicking phantom (TUMP) model that can simulate competently a tumor that is surrounded by healthy tissue. Methods The TUMP models were prepared using polyacrylamide (PAA) and agar solutions enriched with MR contrast agents (silicon dioxide and glycerol), and the thermosensitive component bovine serum albumin (BSA) that can alter its physical properties once thermal change is detected, therefore offering real-time visualization of the applied FUS ablation in the TUMPs models. To establish if these TUMPs are good candidates to be used in thermoablation, their thermal properties were characterized with a custom-made FUS system in the laboratory and a magnetic resonance imaging (MRI) setup with MR-thermometry. The BSA protein's coagulation temperature was adjusted at 55°C by setting the pH of the PAA solution to 4.5, therefore simulating the necrosis temperature of the tissue. Results The experiments carried out showed that the TUMP models prepared by PAA can change color from transparent to cream-white due to the BSA protein coagulation caused by the thermal stress applied. The TUMP models offered a good MRI contrast between the TMPs and the TUMPs including real-time visualization of the ablation area due to the BSA protein coagulation. Furthermore, the T2-weighted MR images obtained showed a significant change in T2 when the BSA protein is thermally coagulated. MR thermometry maps demonstrated that the suggested TUMP models may successfully imitate a tumor that is present in soft tissue. Conclusion The TUMP models developed in this study have numerous uses in the testing and calibration of FUS equipment including the simulation and validation of thermal therapy treatment plans with FUS or MRgFUS in oncology applications.
Collapse
Affiliation(s)
- Panagiotis Sofokleous
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
3
|
Filippou A, Evripidou N, Georgiou A, Nikolaou A, Damianou C. Estimation of the Proton Resonance Frequency Coefficient in Agar-based Phantoms. J Med Phys 2024; 49:167-180. [PMID: 39131424 PMCID: PMC11309147 DOI: 10.4103/jmp.jmp_146_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 01/26/2024] [Accepted: 03/27/2024] [Indexed: 08/13/2024] Open
Abstract
Aim Agar-based phantoms are popular in high intensity focused ultrasound (HIFU) studies, with magnetic resonance imaging (MRI) preferred for guidance since it provides temperature monitoring by proton resonance frequency (PRF) shift magnetic resonance (MR) thermometry. MR thermometry monitoring depends on several factors, thus, herein, the PRF coefficient of agar phantoms was estimated. Materials and Methods Seven phantoms were developed with varied agar (2, 4, or 6% w/v) or constant agar (6% w/v) and varied silica concentrations (2, 4, 6, or 8% w/v) to assess the effect of the concentration on the PRF coefficient. Each phantom was sonicated using varied acoustical power for a 30 s duration in both a laboratory setting and inside a 3T MRI scanner. PRF coefficients were estimated through linear trends between phase shift acquired using gradient sequences and thermocouple-based temperatures changes. Results Linear regression (R 2 = 0.9707-0.9991) demonstrated a proportional dependency of phase shift with temperature change, resulting in PRF coefficients between -0.00336 ± 0.00029 and -0.00934 ± 0.00050 ppm/°C for the various phantom recipes. Weak negative linear correlations of the PRF coefficient were observed with increased agar. With silica concentrations, the negative linear correlation was strong. For all phantoms, calibrated PRF coefficients resulted in 1.01-3.01-fold higher temperature changes compared to the values calculated using a literature PRF coefficient. Conclusions Phantoms developed with a 6% w/v agar concentration and doped with 0%-8% w/v silica best resemble tissue PRF coefficients and should be preferred in HIFU studies. The estimated PRF coefficients can result in enhanced MR thermometry monitoring and evaluation of HIFU protocols.
Collapse
Affiliation(s)
- Antria Filippou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Andreas Georgiou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Anastasia Nikolaou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
4
|
Antoniou A, Damianou C. Feasibility of Ultrasonic Heating through Skull Phantom Using Single-element Transducer. J Med Ultrasound 2024; 32:32-40. [PMID: 38665339 PMCID: PMC11040484 DOI: 10.4103/jmu.jmu_3_23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 03/14/2023] [Accepted: 03/31/2023] [Indexed: 04/28/2024] Open
Abstract
Background Noninvasive neurosurgery has become possible through the use of transcranial focused ultrasound (FUS). This study assessed the heating ability of single element spherically focused transducers operating at 0.4 and 1.1 MHz through three-dimensional (3D) printed thermoplastic skull phantoms. Methods Phantoms with precise skull bone geometry of a male patient were 3D printed using common thermoplastic materials following segmentation on a computed tomography head scan image. The brain tissue was mimicked by an agar-based gel phantom developed in-house. The selection of phantom materials was mainly based on transmission-through attenuation measurements. Phantom sonications were performed through water, and then, with the skull phantoms intervening the beam path. In each case, thermometry was performed at the focal spot using thermocouples. Results The focal temperature change in the presence of the skull phantoms was reduced to less than 20 % of that recorded in free field when using the 0.4 MHz transducer, whereas the 1.1 MHz trans-skull sonication produced minimal or no change in focal temperature. The 0.4 MHz transducer showed better performance in trans-skull transmission but still not efficient. Conclusion The inability of both tested single element transducers to steer the beam through the high attenuating skull phantoms and raise the temperature at the focus was confirmed, underlying the necessity to use a correction technique to compensate for energy losses, such those provided by phased arrays. The proposed phantom could be used as a cost-effective and ergonomic tool for trans-skull FUS preclinical studies.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
5
|
Antoniou A, Evripidou N, Georgiou L, Chrysanthou A, Ioannides C, Damianou C. Tumor phantom model for MRI-guided focused ultrasound ablation studies. Med Phys 2023; 50:5956-5968. [PMID: 37226334 DOI: 10.1002/mp.16480] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 03/24/2023] [Accepted: 05/02/2023] [Indexed: 05/26/2023] Open
Abstract
BACKGROUND The 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. PURPOSE This 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. METHODS Normal 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. RESULTS The 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. CONCLUSION Overall, 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.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Leonidas Georgiou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Antreas Chrysanthou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Cleanthis Ioannides
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
6
|
Antoniou A, Nikolaou A, Evripidou N, Georgiou A, Filippou A, Zinonos V, Giannakou M, Chrysanthou A, Ioannides C, Damianou C. Phantom-based assessment of motion and needle targeting accuracy of robotic devices for magnetic resonance imaging-guided needle biopsy. Int J Med Robot 2023; 19:e2526. [PMID: 37165718 DOI: 10.1002/rcs.2526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 04/18/2023] [Accepted: 04/24/2023] [Indexed: 05/12/2023]
Abstract
BACKGROUND The current study proposes simple methods for assessing the performance of robotic devices intended for Magnetic Resonance Imaging (MRI)-guided needle biopsy. METHODS In-house made agar-based breast phantoms containing biopsy targets served as the main tool in the evaluation process of an MRI compatible positioning device comprising a needle navigator. The motion accuracy of mechanical stages was assessed by calliper measurements. Laboratory evaluation of needle targeting included a repeatability phantom test and a laser-based method. The accuracy and repeatability of needle targeting was also assessed by MRI. RESULTS The maximum error of linear motion for steps up to 10 mm was 0.1 mm. Needle navigation relative to the phantom and alignment with the various biopsy targets were performed successfully in both the laboratory and MRI settings. The proposed biopsy phantoms offered tissue-like signal in MRI and good haptic feedback during needle insertion. CONCLUSIONS The proposed methods could be valuable in the process of validating the accuracy of MRI-guided biopsy robotic devices in both laboratory and real environments.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Anastasia Nikolaou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Andreas Georgiou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Antria Filippou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Vasiliki Zinonos
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | | | - Antreas Chrysanthou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Cleanthis Ioannides
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
7
|
Antoniou A, Damianou C. Simple, inexpensive, and ergonomic phantom for quality assurance control of MRI guided Focused Ultrasound systems. J Ultrasound 2023; 26:401-408. [PMID: 36329304 PMCID: PMC10247591 DOI: 10.1007/s40477-022-00740-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
Abstract
PURPOSE The popularity of Magnetic Resonance guided Focused Ultrasound (MRgFUS) as a beneficial therapeutic solution for many diseases is increasing rapidly, thus raising the need for reliable quality assurance (QA) phantoms for routine testing of MRgFUS systems. In this study, we propose a thin acrylic film as the cheapest and most easily accessible phantom for assessing the functionality of MRgFUS hardware and software. METHODS Through the paper, specific QA tests are detailed in the framework of evaluating an MRgFUS preclinical robotic device comprising a single element spherically focused transducer with a nominal frequency of 2.75 MHz. These tests take advantage of the reflection of ultrasonic waves at a plastic-air interface, which results in almost immediate lesion formation on the film at a threshold of applied acoustic energy. RESULTS The phantom offered qualitative information on the power field distribution of the FUS transducer and the ability to visualize different FUS protocols. It also enabled quick and reliable assessment of various navigation algorithms as they are used in real treatments, and also allowed for the assessment of the accuracy of robotic motion. CONCLUSION Therefore, it could serve as a useful tool for detecting defects in system's performance over its lifetime after establishing a baseline while concurrently contributing to establish QA and calibration guidelines for clinical routine controls.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus.
| |
Collapse
|
8
|
Martin MN, Jordanova KV, Kos AB, Russek SE, Keenan KE, Stupic KF. Relaxation measurements of an MRI system phantom at low magnetic field strengths. MAGMA (NEW YORK, N.Y.) 2023:10.1007/s10334-023-01086-y. [PMID: 37209233 PMCID: PMC10386925 DOI: 10.1007/s10334-023-01086-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 02/23/2023] [Accepted: 03/29/2023] [Indexed: 05/22/2023]
Abstract
OBJECTIVE Temperature controlled T1 and T2 relaxation times are measured on NiCl2 and MnCl2 solutions from the ISMRM/NIST system phantom at low magnetic field strengths of 6.5 mT, 64 mT and 550 mT. MATERIALS AND METHODS The T1 and T2 were measured of five samples with increasing concentrations of NiCl2 and five samples with increasing concentrations of MnCl2. All samples were scanned at 6.5 mT, 64 mT and 550 mT, at sample temperatures ranging from 10 °C to 37 °C. RESULTS The NiCl2 solutions showed little change in T1 and T2 with magnetic field strength, and both relaxation times decreased with increasing temperature. The MnCl2 solutions showed an increase in T1 and a decrease in T2 with increasing magnetic field strength, and both T1 and T2 increased with increasing temperature. DISCUSSION The low field relaxation rates of the NiCl2 and MnCl2 arrays in the ISMRM/NIST system phantom are investigated and compared to results from clinical field strengths of 1.5 T and 3.0 T. The measurements can be used as a benchmark for MRI system functionality and stability, especially when MRI systems are taken out of the radiology suite or laboratory and into less traditional environments.
Collapse
Affiliation(s)
- Michele N Martin
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA.
| | - Kalina V Jordanova
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA
| | - Anthony B Kos
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA
| | - Stephen E Russek
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA
| | - Kathryn E Keenan
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA
| | - Karl F Stupic
- U.S. Department of Commerce, National Institute of Standards and Technology, 325 Broadway, Boulder, CO, 80305, USA
| |
Collapse
|
9
|
Antoniou A, Nikolaou A, Georgiou A, Evripidou N, Damianou C. Development of an US, MRI, and CT imaging compatible realistic mouse phantom for thermal ablation and focused ultrasound evaluation. ULTRASONICS 2023; 131:106955. [PMID: 36854247 DOI: 10.1016/j.ultras.2023.106955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 11/09/2022] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
Tissue mimicking phantoms (TMPs) play an essential role in modern biomedical research as cost-effective quality assurance and training tools, simultaneously contributing to the reduction of animal use. Herein, we present the development and evaluation of an anatomically accurate mouse phantom intended for image-guided thermal ablation and Focused Ultrasound (FUS) applications. The proposed mouse model consists of skeletal and soft tissue mimics, whose design was based on the Computed tomography (CT) scans data of a live mouse. Advantageously, it is compatible with US, CT, and Magnetic Resonance Imaging (MRI). The compatibility assessment was focused on the radiological behavior of the phantom due to the lack of relevant literature. The X-ray linear attenuation coefficient of candidate materials was estimated to assess the one that matches best the radiological behavior of living tissues. The bone part was manufactured by Fused Deposition Modeling (FDM) printing using Acrylonitrile styrene acrylate (ASA) material. For the soft-tissue mimic, a special mold was 3D printed having a cavity with the unique shape of the mouse body and filled with an agar-based silica-doped gel. The mouse phantom accurately matched the size and reproduced the body surface of the imaged mouse. Tissue-equivalency in terms of X-ray attenuation was demonstrated for the agar-based soft-tissue mimic. The phantom demonstrated excellent MRI visibility of the skeletal and soft-tissue mimics. Good radiological contrast between the skeletal and soft-tissue models was also observed in the CT scans. The model was also able to reproduce realistic behavior during trans-skull sonication as proved by thermocouple measurements. Overall, the proposed phantom is inexpensive, ergonomic, and realistic. It could constitute a powerful tool for image-guided thermal ablation and FUS studies in terms of testing and optimizing the performance of relevant equipment and protocols. It also possess great potential for use in transcranial FUS applications, including the emerging topic of FUS-mediated blood brain barrier (BBB) disruption.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Anastasia Nikolaou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Andreas Georgiou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| |
Collapse
|
10
|
Motovilova E, Aronowitz E, Vincent J, Shin J, Tan ET, Robb F, Taracila V, Sneag DB, Dyke JP, Winkler SA. Silicone-based materials with tailored MR relaxation characteristics for use in reduced coil visibility and in tissue-mimicking phantom design. Med Phys 2023. [PMID: 36737839 DOI: 10.1002/mp.16255] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 12/24/2022] [Accepted: 01/15/2023] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The development of materials with tailored signal intensity in MR imaging is critically important both for the reduction of signal from non-tissue hardware, as well as for the construction of tissue-mimicking phantoms. Silicone-based phantoms are becoming more popular due to their structural stability, stretchability, longer shelf life, and ease of handling, as well as for their application in dynamic imaging of physiology in motion. Moreover, silicone can be also used for the design of stretchable receive radio-frequency (RF) coils. PURPOSE Fabrication of materials with tailored signal intensity for MRI requires knowledge of precise T1 and T2 relaxation times of the materials used. In order to increase the range of possible relaxation times, silicone materials can be doped with gadolinium (Gd). In this work, we aim to systematically evaluate relaxation properties of Gd-doped silicone material at a broad range of Gd concentrations and at three clinically relevant magnetic field strengths (1.5 T, 3 T, and 7 T). We apply the findings for rendering silicone substrates of stretchable receive RF coils less visible in MRI. Moreover, we demonstrate early stage proof-of-concept applicability in tissue-mimicking phantom development. MATERIALS AND METHODS Ten samples of pure and Gd-doped Ecoflex silicone polymer samples were prepared with various Gd volume ratios ranging from 1:5000 to 1:10, and studied using 1.5 T and 3 T clinical and 7 T preclinical scanners. T1 and T2 relaxation times of each sample were derived by fitting the data to Bloch signal intensity equations. A receive coil made from Gd-doped Ecoflex silicone polymer was fabricated and evaluated in vitro at 3 T. RESULTS With the addition of a Gd-based contrast agent, it is possible to significantly change T2 relaxation times of Ecoflex silicone polymer (from 213 ms to 20 ms at 1.5 T; from 135 ms to 17 ms at 3 T; and from 111.4 ms to 17.2 ms at 7 T). T1 relaxation time is less affected by the introduction of the contrast agent (changes from 608 ms to 579 ms; from 802.5 ms to 713 ms at 3 T; from 1276 ms to 979 ms at 7 T). First results also indicate that liver, pancreas, and white matter tissues can potentially be closely mimicked using this phantom preparation technique. Gd-doping reduces the appearance of the silicone-based coil substrate during the MR scan by up to 81%. CONCLUSIONS Gd-based contrast agents can be effectively used to create Ecoflex silicone polymer-based phantoms with tailored T2 relaxation properties. The relative low cost, ease of preparation, stretchability, mechanical stability, and long shelf life of Ecoflex silicone polymer all make it a good candidate for "MR invisible" coil development and bears promise for tissue-mimicking phantom development applicability.
Collapse
Affiliation(s)
- Elizaveta Motovilova
- Department of Radiology, Weill Cornell Medicine, New York, New York, USA.,Department of Radiology, Hospital for Special Surgery, New York, New York, USA
| | - Eric Aronowitz
- Department of Radiology, Weill Cornell Medicine, New York, New York, USA
| | | | - James Shin
- Department of Radiology, Weill Cornell Medicine, New York, New York, USA
| | - Ek Tsoon Tan
- Department of Radiology, Hospital for Special Surgery, New York, New York, USA
| | | | | | - Darryl B Sneag
- Department of Radiology, Hospital for Special Surgery, New York, New York, USA
| | - Jonathan P Dyke
- Department of Radiology, Weill Cornell Medicine, New York, New York, USA
| | | |
Collapse
|
11
|
Giannakou M, Antoniou A, Damianou C. Preclinical robotic device for magnetic resonance imaging guided focussed ultrasound. Int J Med Robot 2023; 19:e2466. [PMID: 36169287 PMCID: PMC10078206 DOI: 10.1002/rcs.2466] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 09/12/2022] [Accepted: 09/27/2022] [Indexed: 01/05/2023]
Abstract
BACKGROUND A robotic device featuring three motion axes was manufactured for preclinical research on focussed ultrasound (FUS). The device comprises a 2.75 MHz single element ultrasonic transducer and is guided by Magnetic Resonance Imaging (MRI). METHODS The compatibility of the device with the MRI was evaluated by estimating the influence on the signal-to-noise ratio (SNR). The efficacy of the transducer in generating ablative temperatures was evaluated in phantoms and excised porcine tissue. RESULTS System's activation in the MRI scanner reduced the SNR to an acceptable level without compromising the image quality. The transducer demonstrated efficient heating ability as proved by MR thermometry. Discrete and overlapping thermal lesions were inflicted in excised tissue. CONCLUSIONS The FUS system was proven effective for FUS thermal applications in the MRI setting. It can thus be used for multiple preclinical applications of the emerging MRI-guided FUS technology. The device can be scaled-up for human use with minor modifications.
Collapse
Affiliation(s)
| | - Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
12
|
Kolosova OY, Shaikhaliev AI, Krasnov MS, Bondar IM, Sidorskii EV, Sorokina EV, Lozinsky VI. Cryostructuring of Polymeric Systems: 64. Preparation and Properties of Poly(vinyl alcohol)-Based Cryogels Loaded with Antimicrobial Drugs and Assessment of the Potential of Such Gel Materials to Perform as Gel Implants for the Treatment of Infected Wounds. Gels 2023; 9:gels9020113. [PMID: 36826283 PMCID: PMC9956285 DOI: 10.3390/gels9020113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 01/26/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Physical macroporous poly(vinyl alcohol)-based cryogels formed by the freeze-thaw technique without the use of any foreign cross-linkers are of significant interests for biomedical applications. In the present study, such gel materials loaded with the antimicrobial substances were prepared and their physicochemical properties were evaluated followed by an assessment of their potential to serve as drug carriers that can be used as implants for the treatment of infected wounds. The antibiotic Ceftriaxone and the antimycotic Fluconazole were used as antimicrobial agents. It was shown that the Ceftriaxone additives caused the up-swelling effects with respect to the cryogel matrix and some decrease in its heat endurance but did not result in a substantial change in the gel strength. With that, the drug release from the cryogel vehicle occurred without any diffusion restrictions, which was demonstrated by both the spectrophotometric recording and the microbiological agar diffusion technique. In turn, the in vivo biotesting of such drug-loaded cryogels also showed that these materials were able to function as rather efficient antimicrobial implants injected in the artificially infected model wounds of laboratory rabbits. These results confirmed the promising biomedical potential of similar implants.
Collapse
Affiliation(s)
- Olga Yu. Kolosova
- A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, Bld. 1, 119334 Moscow, Russia
| | - Astemir I. Shaikhaliev
- Institute of Dentistry, I.M.Sechenov First Moscow State Medical University (Sechenov University), 119991 Moscow, Russia
| | - Mikhail S. Krasnov
- A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, Bld. 1, 119334 Moscow, Russia
| | - Ivan M. Bondar
- Institute of Dentistry, I.M.Sechenov First Moscow State Medical University (Sechenov University), 119991 Moscow, Russia
| | - Egor V. Sidorskii
- A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, Bld. 1, 119334 Moscow, Russia
| | - Elena V. Sorokina
- Microbiology Department, Biology Faculty, M.V.Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Vladimir I. Lozinsky
- A.N.Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Street 28, Bld. 1, 119334 Moscow, Russia
- Microbiology Department, Kazan (Volga-Region) Federal University, 420008 Kazan, Russia
- Correspondence: ; Tel.: +7-499-135-6492
| |
Collapse
|
13
|
Antoniou A, Georgiou L, Evripidou N, Ioannides C, Damianou C. Challenges regarding MR compatibility of an MRgFUS robotic system. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 344:107317. [PMID: 36279604 DOI: 10.1016/j.jmr.2022.107317] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 10/11/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Numerous challenges are faced when employing Magnetic Resonance guided Focused Ultrasound (MRgFUS) hardware in the Magnetic Resonance Imaging (MRI) setting. The current study aimed to provide insights on this topic through a series of experiments performed in the framework of evaluating the MRI compatibility of an MRgFUS robotic device. All experiments were performed in a 1.5 T MRI scanner. The main metric for MRI compatibility assessment was the signal to noise ratio (SNR). Measurements were carried out in a tissue mimicking phantom and freshly excised pork tissue under various activation states of the system. In the effort to minimize magnetic interference and image distortion, various set-up parameters were examined. Significant SNR degradation and image distortion occurred when the FUS transducer was activated mainly owing to FUS-induced target and coil vibrations and was getting worse as the output power was increased. Proper design and stable positioning of the imaged phantom play a critical role in reducing these vibrations. Moreover, isolation of the phantom from the imaging coil was proven essential for avoiding FUS-induced vibrations from being transferred to the coil during sonication and resulted in a more than 3-fold increase in SNR. The use of a multi-channel coil increased the SNR by up to 50 % compared to a single-channel coil. Placement of the electronics outside the coil detection area increased the SNR by about 65 %. A similar SNR improvement was observed when the encoders' counting pulses were deactivated. Overall, this study raises awareness about major challenges regarding operation of an MRgFUS system in the MRI environment and proposes simple measures that could mitigate the impact of noise sources so that the monitoring value of MR imaging in FUS applications is not compromised.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Leonidas Georgiou
- German Oncology Center, Department of Interventional Radiology, Limassol, Cyprus.
| | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| | - Cleanthis Ioannides
- German Oncology Center, Department of Interventional Radiology, Limassol, Cyprus.
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus.
| |
Collapse
|
14
|
Antoniou A, Georgiou A, Evripidou N, Damianou C. Full coverage path planning algorithm for MRgFUS therapy. Int J Med Robot 2022; 18:e2389. [PMID: 35257476 PMCID: PMC9286630 DOI: 10.1002/rcs.2389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 03/04/2022] [Accepted: 03/06/2022] [Indexed: 11/17/2022]
Abstract
Background High‐quality methods for Magnetic Resonance guided Focussed Ultrasound (MRgFUS) therapy planning are needed for safe and efficient clinical practices. Herein, an algorithm for full coverage path planning based on preoperative MR images is presented. Methods The software functionalities of an MRgFUS robotic system were enhanced by implementing the developed algorithm. The algorithm's performance in accurate path planning following a Zig‐Zag pathway was assessed on MR images. The planned sonication paths were performed on acrylic films using the robotic system carrying a 2.75 MHz single element transducer. Results Ablation patterns were successfully planned on MR images and produced on acrylic films by overlapping lesions with excellent match between the planned and experimental lesion shapes. Conclusions The advanced software was proven efficient in planning and executing full ablation of any segmented target. The reliability of the algorithm could be enhanced through the development of a fully automated segmentation procedure.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | - Andreas Georgiou
- Department of Electrical Engineering Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| |
Collapse
|
15
|
Influence of Artificial Soft Tissue on Intra-Operative Vibration Analysis Method for Primary Fixation Monitoring in Cementless Total Hip Arthroplasty. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12084027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In cementless Total Hip Arthroplasty (THA), achieving high primary implant fixation is crucial for the long-term survivorship of the femoral stem. While orthopedic surgeons traditionally assess fixation based on their subjective judgement, novel vibration-analysis fixation-monitoring techniques show promising potential in providing the surgeon with objective and quantifiable fixation measurements. This study presents a dynamic response measurement protocol for implant endpoint insertion and evaluates this protocol in the presence of artificial soft tissue. After the artificial femur was prepared in accordance with the THA protocol, the implant was inserted and progressively hammered into the cavity. The Pearson Correlation Coefficient (PCC) and Frequency Response Assurance Criterion (FRAC) corresponding to each insertion hammer hit were derived from the Frequency Response Functions (FRF) corresponding to each insertion step. The protocol was repeated with the artificial femur submerged in artificial soft tissue to imitate the influence of anatomical soft tissue. The FRAC appeared overall more sensitive than the PCC. In the presence of the artificial soft tissue the technique yielded higher PCC and FRAC values earlier in the insertion process. The measurements with artificial soft tissue produced FRFs with fewer peaks, lower resonance frequencies, and overall higher damping factors. The soft tissue appears to limit the fixation-change detection capabilities of the system and a promising potential remedy to this limitation is suggested.
Collapse
|
16
|
Antoniou A, Georgiou L, Christodoulou T, Panayiotou N, Ioannides C, Zamboglou N, Damianou C. MR relaxation times of agar-based tissue-mimicking phantoms. J Appl Clin Med Phys 2022; 23:e13533. [PMID: 35415875 PMCID: PMC9121050 DOI: 10.1002/acm2.13533] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Accepted: 12/29/2021] [Indexed: 12/31/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Leonidas Georgiou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | | | - Natalie Panayiotou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Cleanthis Ioannides
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Nikolaos Zamboglou
- Department of Interventional Radiology, German Oncology Center, Limassol, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| |
Collapse
|
17
|
Antoniou A, Giannakou M, Evripidou N, Stratis S, Pichardo S, Damianou C. Robotic system for top to bottom MRgFUS therapy of multiple cancer types. Int J Med Robot 2022; 18:e2364. [DOI: 10.1002/rcs.2364] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/05/2022] [Accepted: 01/05/2022] [Indexed: 12/18/2022]
Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering, Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | | | - Nikolas Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | - Stylianos Stratis
- Department of Electrical Engineering, Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| | - Samuel Pichardo
- Hotchkiss Brain Institute Cumming School of Medicine University of Calgary Calgary Alberta Canada
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics Cyprus University of Technology Limassol Cyprus
| |
Collapse
|