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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.
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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.
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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.
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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
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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.
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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
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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.
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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
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Ren J, Wang X, Liu C, Sun H, Tong J, Lin M, Li J, Liang L, Yin F, Xie M, Liu Y. 3D Ultrasonic Brain Imaging with Deep Learning Based on Fully Convolutional Networks. SENSORS (BASEL, SWITZERLAND) 2023; 23:8341. [PMID: 37837171 PMCID: PMC10575417 DOI: 10.3390/s23198341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 09/16/2023] [Accepted: 09/25/2023] [Indexed: 10/15/2023]
Abstract
Compared to magnetic resonance imaging (MRI) and X-ray computed tomography (CT), ultrasound imaging is safer, faster, and more widely applicable. However, the use of conventional ultrasound in transcranial brain imaging for adults is predominantly hindered by the high acoustic impedance contrast between the skull and soft tissue. This study introduces a 3D AI algorithm, Brain Imaging Full Convolution Network (BIFCN), combining waveform modeling and deep learning for precise brain ultrasound reconstruction. We constructed a network comprising one input layer, four convolution layers, and one pooling layer to train our algorithm. In the simulation experiment, the Pearson correlation coefficient between the reconstructed and true images was exceptionally high. In the laboratory, the results showed a slightly lower but still impressive coincidence degree for 3D reconstruction, with pure water serving as the initial model and no prior information required. The 3D network can be trained in 8 h, and 10 samples can be reconstructed in just 12.67 s. The proposed 3D BIFCN algorithm provides a highly accurate and efficient solution for mapping wavefield frequency domain data to 3D brain models, enabling fast and precise brain tissue imaging. Moreover, the frequency shift phenomenon of blood may become a hallmark of BIFCN learning, offering valuable quantitative information for whole-brain blood imaging.
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Affiliation(s)
- Jiahao Ren
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Xiaocen Wang
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Chang Liu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - He Sun
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Junkai Tong
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Min Lin
- Department of Mechanical Engineering, University of Wyoming, Laramie, WY 82071, USA;
| | - Jian Li
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Lin Liang
- Schlumberger-Doll Research, Cambridge, MA 02139, USA;
| | - Feng Yin
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China;
| | - Mengying Xie
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
| | - Yang Liu
- State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072, China; (J.R.); (X.W.); (C.L.); (H.S.); (J.T.); (J.L.)
- International Institute for Innovative Design and Intelligent Manufacturing of Tianjin University in Zhejiang, Shaoxing 330100, China
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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.
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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
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Filippou A, Georgiou A, Nikolaou A, Evripidou N, Damianou C. Advanced software for MRgFUS treatment planning. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2023; 240:107726. [PMID: 37480647 DOI: 10.1016/j.cmpb.2023.107726] [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: 02/12/2023] [Revised: 07/18/2023] [Accepted: 07/18/2023] [Indexed: 07/24/2023]
Abstract
BACKGROUND AND OBJECTIVES Herein, a user-friendly software platform for 3-dimensional Focused Ultrasound treatment planning based on Magnetic Resonance Imaging (MRI) images is presented. METHODS The software directly retrieves and loads MRI images. Various design tools can be used on the MRI images to define the treatment area and the sonication parameters. Based on the treatment plan, the software controls the robotic motion and motion pattern of Magnetic Resonance guided Focused Ultrasound (MRgFUS) robotic systems to execute the treatment procedure. Real-time treatment monitoring is achieved through MRI images and thermometry. The software's functionality and performance were evaluated in both laboratory and MRI environments. Different treatment plans were designed on MRI images and sonications were executed on agar-based phantoms and polymer films. RESULTS Magnetic Resonance (MR) thermometry maps were acquired in the agar-based phantoms. An exceptional agreement was observed between the software-planned treatment area and the lesions produced on the polymer films. CONCLUSIONS The developed software was successfully integrated with the MRI and robotic system controls for performing accurate treatment planning and real-time monitoring during sonications. The software provides an extremely user-friendly interface, while in the future it could be enhanced by providing dynamic modulation of the ultrasonic parameters during the treatment process.
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Affiliation(s)
- Antria Filippou
- Cyprus University of Technology, Department of Electrical Engineering, Computer Engineering, and Informatics, 30 Archbishop Kyprianou Str., Limassol 3036, Cyprus.
| | - Andreas Georgiou
- Cyprus University of Technology, Department of Electrical Engineering, Computer Engineering, and Informatics, 30 Archbishop Kyprianou Str., Limassol 3036, Cyprus
| | - Anastasia Nikolaou
- Cyprus University of Technology, Department of Electrical Engineering, Computer Engineering, and Informatics, 30 Archbishop Kyprianou Str., Limassol 3036, Cyprus.
| | - Nikolas Evripidou
- Cyprus University of Technology, Department of Electrical Engineering, Computer Engineering, and Informatics, 30 Archbishop Kyprianou Str., Limassol 3036, Cyprus.
| | - Christakis Damianou
- Cyprus University of Technology, Department of Electrical Engineering, Computer Engineering, and Informatics, 30 Archbishop Kyprianou Str., Limassol 3036, Cyprus.
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Drakos T, Evripidou G, Damianou C. An in vitro Model for Experimental Evaluation of Sonothrombolysis under Tissue-mimicking Material Conditions. J Med Ultrasound 2023; 31:211-217. [PMID: 38025011 PMCID: PMC10668898 DOI: 10.4103/jmu.jmu_52_22] [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: 05/22/2022] [Revised: 07/12/2022] [Accepted: 08/10/2022] [Indexed: 12/01/2023] Open
Abstract
Background The mechanical properties of therapeutic ultrasound (US) have attracted scientific interest for thrombolysis enhancement in combination with thrombolytic agents and microbubbles (MBs). The aim of the study was to develop an in vitro model to observe how the effects of sonothrombolysis change in the case where a tissue-mimicking material (TMM) is placed in the path of the US beam before the clot. Methods Fully retracted blood clots were prepared and pulse sonicated for 1 h under various conditions. The system was in a state of real circulating flow with a branch of an open bypass and an occluded tube containing a blood clot, thus mimicking the case of ischemic stroke. The effectiveness of thrombolysis was quantified in milligrams of clots removed. An agar-based TMM was developed around the occluded tube. Results The clot breakdown in a TMM was found to be more pronounced than in water, presumably due to the retention of the acoustic field. A higher level of acoustic power was required to initiate clot lysis (>76 W acoustic power) using only focused US (FUS). The greatest thrombolysis enhancement was observed with the largest chosen pulse duration (PD) and the use of MBs (150 mg clot mass lysis). The synergistic effect of FUS in combination with MBs on the enzymatic fibrinolysis enhanced thrombolysis efficacy by 260% compared to thrombolysis induced using only FUS. A reduction in the degree of clot lysis was detected due to the attenuation factor of the intervening material (30 mg at 1 and 4 ms PD). Conclusion In vitro thrombolytic models including a TMM can provide a more realistic evaluation of new thrombolytic protocols. However, higher acoustic power should be considered to compensate for the attenuation factor. The rate of clot lysis is slow and the clinical use of this method will be challenging.
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Affiliation(s)
| | - Georgios 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
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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.
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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.
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Filippou A, Louca I, Damianou C. Characterization of a fat tissue mimicking material for high intensity focused ultrasound applications. J Ultrasound 2023; 26:505-515. [PMID: 36414928 PMCID: PMC10247632 DOI: 10.1007/s40477-022-00746-4] [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: 07/20/2022] [Accepted: 10/11/2022] [Indexed: 11/23/2022] Open
Abstract
PURPOSE Tissue-mimicking materials (TMMs) have a prominent role in validating new high intensity focused ultrasound (HIFU) therapies. Agar-based TMMs are often developed mimicking the thermal properties of muscle tissue, while TMMs simulating fat tissue properties are rarely developed. Herein, twelve agar-based TMMs were iteratively developed with varied concentrations of agar, water, glycerol and propan-2-ol, and characterized for their suitability in emulating the thermal conductivity of human fat tissue. METHODS Varied agar concentrations (2%, 4%, 6%, 8%, 12%, 16% and 20% w/v) were utilized for developing seven water-based TMMs, while a 20% w/v agar concentration was utilized for developing two water/alcohol-based TMMs (50% v/v water and 50% v/v either glycerol or propan-2-ol) and three alcohol-based TMMs (varied glycerol and propan-2-ol concentrations). Thermal conductivity was measured for all TMMs, and the tissue mimicking material (TMM) exhibiting thermal conductivity closest to human fat was considered the optimum fat TMM and was further characterized using ultrasound (US) and Magnetic Resonance Imaging (MRI). RESULTS For the seven water-based TMMs an inverse linear trend was observed between thermal conductivity and increased agar concentration, being between 0.524 and 0.445 W/m K. Alcohol addition decreased thermal conductivity of the two water/alcohol-based TMMs to about 0.33 W/m K, while in the alcohol-based TMMs, increased concentrations of propan-2-ol emerged as a modifier of thermal conductivity. The optimum fat TMM (33.3% v/v glycerol and 66.7% v/v propan-2-ol) exhibited a 0.231 W/m K thermal conductivity, and appeared hypoechoic on US images and with increased brightness on T1-Weighted MRI images. CONCLUSION The optimum fat TMM emulates the thermal conductivity of human fat tissue and exhibits a fat-like appearance on US and MRI images. The TMM is cost-effective and has a long lifespan and possesses great potential for use in HIFU applications as a fat TMM.
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Affiliation(s)
- Antria Filippou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, 30 Archbishop Kyprianou Street, 3036, Limassol, Cyprus
| | - Irene Louca
- 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.
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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.
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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.
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12
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Filippou A, Damianou C. Evaluation of ultrasonic scattering in agar-based phantoms using 3D printed scattering molds. J Ultrasound 2022; 25:597-609. [PMID: 34997563 PMCID: PMC9402872 DOI: 10.1007/s40477-021-00630-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 09/30/2021] [Indexed: 10/19/2022] Open
Abstract
PURPOSE Acoustic characterization of tissue mimicking materials in terms of attenuation, absorption, scattering and propagation velocity is essential for their utilisation in experiments, thus sparing the need for living tissues or cadavers. Although there is a vast literature regarding the acoustic characterization of such materials in terms of attenuation or propagation velocity, there is limited data regarding the quantification of the scattering coefficient. Herein stimulated the utilisation of four agar-based phantoms featuring different sizes of scattering agar-structures on one of their surfaces so as to provide experimental evaluation of the magnitude of scattering. METHODS The agar-based phantoms were developed with 6% w/v agar and 4% w/v silica and featured scatterers of sizes of 0-1 mm. The acoustic properties of propagation speed, impedance, insertion loss and attenuation were evaluated utilising the pulse-echo and through-transmission techniques. Scattering was deduced from the data. RESULTS The propagation speed measured at 2.7 MHz was in the range of 1531.23-1542.97 m/s. Respectively the attenuation as measured at 1.1 MHz was in the range of 1.216-1.546 dB/cm increasing with increased scatterer size. Respectively the scattering coefficient was in the range of 0.078-0.324 dB/cm. Moreover, the scattering coefficient was linearly dependent on frequency in the range of 0.8-2.1 MHz indicating a 6-23% effect of the total attenuation. CONCLUSIONS The experimental results demonstrate the utilisation of the procedure for quantification of the scattering coefficient of tissue mimicking materials thus improving the diagnostic and therapeutic uses of ultrasound.
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Affiliation(s)
- Antria Filippou
- 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.
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13
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Zhong X, Cao Y, Zhou P. Thermochromic Tissue-Mimicking Phantoms for Thermal Ablation Based on Polyacrylamide Gel. ULTRASOUND IN MEDICINE & BIOLOGY 2022; 48:1361-1372. [PMID: 35623921 DOI: 10.1016/j.ultrasmedbio.2022.03.021] [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: 11/19/2021] [Revised: 03/29/2022] [Accepted: 03/30/2022] [Indexed: 06/15/2023]
Abstract
In recent years, thermal ablation has played an increasingly important role in treating various tumors in the clinic. A practical thermochromic phantom model can provide a favorable platform for clinical thermotherapy training of young physicians or calibration and optimization of thermal devices without risk to animals or human participants. To date, many tissue-mimicking thermal phantoms have been developed and are well liked, especially the polyacrylamide gel (PAG)-based phantoms. This review summarizes the PAG-based phantoms in the field of thermotherapy, details their advantages and disadvantages and provides a direction for further optimization. The relevant physical parameters (such as electrical, acoustic, and thermal properties) of these phantoms are also presented in this review, which can assist operators in a deeper understanding of these phantoms and selection of the proper recipes for phantom fabrication.
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Affiliation(s)
- Xinyu Zhong
- Department of Ultrasound, Third Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Yuting Cao
- Institute of Ultrasound Imaging & Department of Ultrasound, Second Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Ultrasound Molecular Imaging, Chongqing, China
| | - Ping Zhou
- Department of Ultrasound, Third Xiangya Hospital, Central South University, Changsha, Hunan, China.
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14
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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.
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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
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15
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Denis L, Maria K, Daria L, Anastasia N, Nicholas K. Design and validation of a phantom for transcranial ultrasonography. Int J Comput Assist Radiol Surg 2022; 17:1579-1588. [DOI: 10.1007/s11548-022-02614-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 03/17/2022] [Indexed: 11/29/2022]
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16
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Antoniou A, Damianou C. MR relaxation properties of tissue-mimicking phantoms. ULTRASONICS 2022; 119:106600. [PMID: 34627028 DOI: 10.1016/j.ultras.2021.106600] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2021] [Revised: 09/20/2021] [Accepted: 09/21/2021] [Indexed: 06/13/2023]
Abstract
High quality tissue-mimicking phantoms (TMPs) have a critical role in the preclinical testing of emerging modalities for diagnosis and therapy. TMPs capable of accurately mimicking real tissue in Magnetic Resonance guided Focused Ultrasound (MRgFUS) applications should be fabricated with precise T1 and T2 relaxation times. Given the current popularity of the MRgFUS technology, we herein performed a systematic review on the MR relaxation properties of different phantoms types. Polyacrylamide (PAA) and agar based phantoms were proven capable of accurately replicating critical thermal, acoustical, and MR relaxation properties of various body tissues. Although gelatin phantoms were also proven factional in this regard, they lack the capacity to withstand ablation temperatures, and thus, are only recommended for hyperthermia applications. Other gelling agents identified in the literature are Poly-vinyl alcohol (PVA), Polyvinyl Chloride (PVC), silicone, and TX-150/ TX-151; however, their efficacy in thermal studies is yet to be established. PAA gels are favorable in that they offer optical transparency enabling direct visualization of coagulative lesions. On the other hand, agar phantoms have lower preparation costs and were proven very promising for use with the MRgFUS technology, without the toxicity issues related to the preparation and storage of PAA materials. Remarkably, agar turned out to be the prominent modifier of the T2 relaxation time even for phantoms containing other types of gelling agents instead of agar. This review could be useful in manufacturing realistic MRgFUS phantoms while simultaneously indicating an opportunity for further research in the field with a particular focus on the MR behavior of agar-based TMPs.
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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.
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17
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Drakos T, Giannakou M, Menikou G, Damianou C. Magnetic Resonance Imaging-Guided Focused Ultrasound Positioning System for Preclinical Studies in Small Animals. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2021; 40:1343-1352. [PMID: 33031567 PMCID: PMC8246715 DOI: 10.1002/jum.15514] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/06/2020] [Accepted: 09/07/2020] [Indexed: 06/01/2023]
Abstract
OBJECTIVES A positioning device compatible with magnetic resonance imaging (MRI) used for preclinical studies in small animals was developed that fits in MRI scanners up to 7 T. The positioning device was designed with two computer-controlled linear stages. METHODS The positioning device was evaluated in an agar-based phantom, which mimics soft tissues, and in a rabbit. Experiments with this positioning device were performed in an MRI system using the agar-based phantom. The transducer used had a diameter of 50 mm, operated at 0.5 MHz, and focused energy at 60 mm. RESULTS Magnetic resonance thermometry was used to assess the functionality of the device, which showed adequate deposition of thermal energy and sufficient positional accuracy in all axes. CONCLUSIONS The proposed system fits in MRI scanners up to 7 T. Because of the size of the positioning device, at the moment, it can be used to perform preclinical studies on small animals such as mice, rats, and rabbits.
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Affiliation(s)
| | | | - Georgios Menikou
- Department of Electrical EngineeringCyprus University of TechnologyLimassolCyprus
| | - Christakis Damianou
- Department of Electrical EngineeringCyprus University of TechnologyLimassolCyprus
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18
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Antoniou A, Giannakou M, Evripidou N, Evripidou G, Spanoudes K, Menikou G, Damianou C. Robotic system for magnetic resonance guided focused ultrasound ablation of abdominal cancer. Int J Med Robot 2021; 17:e2299. [PMID: 34105234 DOI: 10.1002/rcs.2299] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 06/07/2021] [Accepted: 06/08/2021] [Indexed: 12/19/2022]
Abstract
BACKGROUND A prototype robotic system that uses magnetic resonance guided focused ultrasound (MRgFUS) technology is presented. It features three degrees of freedom (DOF) and is intended for thermal ablation of abdominal cancer. METHODS The device is equipped with three identical transducers being offset between them, thus focussing at different depths in tissue. The efficacy and safety of the system in ablating rabbit liver and kidney was assessed, both in laboratory and magnetic resonance imaging (MRI) conditions. RESULTS Despite these organs' challenging location, in situ coagulative necrosis of a tissue area was achieved. Heating of abdominal organs in rabbit was successfully monitored with MR thermometry. CONCLUSIONS The MRgFUS system was proven successful in creating lesions in the abdominal area of rabbits. The outcomes of the study are promising for future translation of the technology to the clinic.
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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
| | - Georgios Evripidou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Kyriakos Spanoudes
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
| | - Georgios Menikou
- Medical Physics Sector, State Health Services Organization, Nicosia General Hospital, Nicosia, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering, and Informatics, Cyprus University of Technology, Limassol, Cyprus
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19
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Drakos T, Giannakou M, Menikou G, Constantinides G, Damianou C. Characterization of a soft tissue-mimicking agar/wood powder material for MRgFUS applications. ULTRASONICS 2021; 113:106357. [PMID: 33548756 DOI: 10.1016/j.ultras.2021.106357] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 12/29/2020] [Accepted: 01/06/2021] [Indexed: 06/12/2023]
Abstract
This study describes the development and characterization of an agar-based soft tissue-mimicking material (TMM) doped with wood powder destined for fabricating MRgFUS applications. The main objective of the following work was to investigate the suitability of wood powder as an inexpensive alternative in replacing other added materials that have been suggested in previous studies for controlling the ultrasonic properties of TMMs. The characterization procedure involved a series of experiments designed to estimate the acoustic (attenuation coefficient, absorption coefficient, propagation speed, and impedance), thermal (conductivity, diffusivity, specific heat capacity), and MR properties (T1 and T2 relaxation times) of the wood-powder doped material. The developed TMM (2% w/v agar and 4% w/v wood powder) as expected demonstrated compatibility with MRI scanner following images artifacts evaluation. The acoustic attenuation coefficient of the proposed material was measured over the frequency range of 1.1-3 MHz and found to be nearly proportional to frequency. The measured attenuation coefficient was 0.48 dB/cm at 1 MHz which was well within the range of soft tissue. Temperatures over 37 °C proved to increase marginally the attenuation coefficient. Following the transient thermoelectric method, the acoustic absorption coefficient was estimated at 0.34 dB/cm-MHz. The estimated propagation speed (1487 m/s) was within the range of soft tissue at room temperature, while it significantly increased with higher temperature. The material possessed an acoustic impedance of 1.58 MRayl which was found to be comparable to the corresponding value of muscle tissue. The thermal conductivity of the material was estimated at 0.51 W/m K. The measured relaxation times T1 (844 ms) and T2 (66 ms) were within the range of values found in the literature for soft tissue. The phantom was tested for its suitability for evaluating MRgFUS thermal protocols. High acoustic energy was applied, and temperature change was recorded using thermocouples and MR thermometry. MR thermal maps were acquired using single-shot Echo Planar Imaging (EPI) gradient echo sequence. The TMM matched adequately the acoustic and thermal properties of human tissues and through a series of experiments, it was proven that wood concentration enhances acoustic absorption. Experiments using MR thermometry demonstrated the usefulness of this phantom to evaluate ultrasonic thermal protocols by monitoring peak temperatures in real-time. Thermal lesions formed above a thermal dose were observed in high-resolution MR images and visually in dissections of the proposed TMM.
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Affiliation(s)
| | | | - Georgios Menikou
- Medical Physics Sector, State Health Services Organization, Nicosia General Hospital, Nicosia, Cyprus.
| | - Georgios Constantinides
- Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, Limassol, Cyprus.
| | - Christakis Damianou
- Department of Electrical Engineering, Computer Engineering and Informatics, Cyprus University of Technology, Limassol, Cyprus.
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20
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Antoniou A, Evripidou N, Giannakou M, Constantinides G, Damianou C. Acoustical properties of 3D printed thermoplastics. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2021; 149:2854. [PMID: 33940906 DOI: 10.1121/10.0004772] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 04/03/2021] [Indexed: 06/12/2023]
Abstract
With focused ultrasound (FUS) gaining popularity as a therapeutic modality for brain diseases, the need for skull phantoms that are suitable for evaluating FUS protocols is increasing. In the current study, the acoustical properties of several three-dimensional (3D) printed thermoplastic samples were evaluated to assess their suitability to mimic human skull and bone accurately. Samples were 3D printed using eight commercially available thermoplastic materials. The acoustic properties of the printed samples, including attenuation coefficient, speed of sound, and acoustic impedance, were investigated using transmission-through and pulse-echo techniques. The ultrasonic attenuation, estimated at a frequency of 1.1 MHz, varied from approximately 7 to 32 dB/cm. The frequency dependence of attenuation was described by a power law in the frequency range of 0.2-3.5 MHz, and the exponential index of frequency was found to vary from 1.30 to 2.24. The longitudinal velocity of 2.7 MHz sound waves was in the range of 1700-3050 m/s. The results demonstrate that thermoplastics could potentially be used for the 3D construction of high-quality skull phantoms.
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Affiliation(s)
- Anastasia Antoniou
- Department of Electrical Engineering and Computer Engineering and Informatics, Cyprus University of Technology, 30 Archiepiskopou Kyprianou Street, Limassol, 3036, Cyprus
| | - Nikolas Evripidou
- Department of Electrical Engineering and Computer Engineering and Informatics, Cyprus University of Technology, 30 Archiepiskopou Kyprianou Street, Limassol, 3036, Cyprus
| | - Marinos Giannakou
- MEDSONIC LTD, 35 Christaki Kranou Street, Germasogia, Limassol, 4041, Cyprus
| | - Georgios Constantinides
- Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, 30 Archiepiskopou Kyprianou Street, Limassol, 3036, Cyprus
| | - Christakis Damianou
- Department of Electrical Engineering and Computer Engineering and Informatics, Cyprus University of Technology, 30 Archiepiskopou Kyprianou Street, Limassol, 3036, Cyprus
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21
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von Barm R, Tejada IM, Juhler M, Andresen M, Wilhjelm JE. Physical Model for Investigating Intracranial Pressure with Clinical Pressure Sensors and Diagnostic Ultrasound: Preliminary Results. ACTA NEUROCHIRURGICA. SUPPLEMENT 2021; 131:263-266. [PMID: 33839855 DOI: 10.1007/978-3-030-59436-7_49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
INTRODUCTION Intracranial pressure (ICP) is a commonly collected neurocritical parameter, but accurate signal modelling remains challenging. The goal of this project was to mimic clinical ICP waveforms using a physical model. MATERIALS AND METHODS A physical head model was developed. The skull was segmented from a head computed tomography (CT) scan, remodelled, 3D-printed, and filled with a brain tissue mimicking material and a pressure generator. Pressure measurements and tissue displacement around an attached pressure sensor were explored. RESULTS Analysis of the measured pressure demonstrated that the waveform did not perfectly resemble that of the clinical ICP. Through iterative improvements and using a revised second pressure generator, subpeaks could be seen in the waveform. A speckle image recorded using ultrasound during pressure application enabled visualization of tissue displacement around the pressure sensor. Comparison with measured ICP signals revealed that minuscule patterns were not distinct in the displacement images. DISCUSSION We present the first steps towards mimicking clinical ICP using a physical head phantom model. The physical model enabled pressure tests and visualization of tissue displacement and will be foundational for further improvements.
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Affiliation(s)
- Rikke von Barm
- DTU Health Technology, Technical University of Denmark, Lyngby, Denmark.
| | - Isabel Martinez Tejada
- DTU Health Technology, Technical University of Denmark, Lyngby, Denmark
- CSF Study Group, Clinic of Neurosurgery, NK 2092, Copenhagen University Hospital, Copenhagen, Denmark
| | - Marianne Juhler
- CSF Study Group, Clinic of Neurosurgery, NK 2092, Copenhagen University Hospital, Copenhagen, Denmark
| | - Morten Andresen
- CSF Study Group, Clinic of Neurosurgery, NK 2092, Copenhagen University Hospital, Copenhagen, Denmark
| | - Jens E Wilhjelm
- DTU Health Technology, Technical University of Denmark, Lyngby, Denmark
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22
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Damianou C, Giannakou M, Evripidou N, Kegel S, Huber P, Jenne J. Focused ultrasound robotic system for very small bore magnetic resonance imaging. Int J Med Robot 2020; 16:1-9. [PMID: 32927501 PMCID: PMC7816236 DOI: 10.1002/rcs.2165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 09/01/2020] [Accepted: 09/05/2020] [Indexed: 11/06/2022]
Abstract
Background A magnetic resonance imaging (MRI) compatible robotic system for focused ultrasound was developed for small animal like mice or rats that fits into a 9.4 T MRI scanner (Bruker Biospec 9420, Bruker Biospin, Ettlingen, Germany). The robotic system includes two computer‐controlled linear stages. Materials and Methods The robotic system was evaluated in a mouse‐shaped, real‐size agar‐based mimicking material, which has similar acoustical properties as soft tissues. The agar content was 6% weight per volume (w/v), 4% w/v silica while the rest was degassed water. The transducer used has a diameter of 4 cm, operates with 2.6 MHz and focuses energy at 5 cm. Results The MRI compatibility of the robotic system was evaluated in a 9.4 T small animal scanner. The efficacy of the ultrasonic transducer was evaluated in the mimicking material using temperature measurements. Conclusions The proposed robotic system can be utilized in a 9.4 T small animal MRI scanner. The proposed system is functional, compact and simple thus providing a useful tool for preclinical research in mice and rats.
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Affiliation(s)
- Christakis Damianou
- Electrical Engineering and Computer Engineering and Informatics Department, Cyprus University of Technology, Limassol, Cyprus
| | - Marinos Giannakou
- Electrical Engineering and Computer Engineering and Informatics Department, Cyprus University of Technology, Limassol, Cyprus.,MEDSONIC LTD, Limassol, Cyprus
| | - Nikolas Evripidou
- Electrical Engineering and Computer Engineering and Informatics Department, Cyprus University of Technology, Limassol, Cyprus
| | - Stefan Kegel
- German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - Peter Huber
- German Cancer Research Center (DKFZ), Heidelberg, Germany
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23
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Rai R, Holloway LC, Brink C, Field M, Christiansen RL, Sun Y, Barton MB, Liney GP. Multicenter evaluation of MRI-based radiomic features: A phantom study. Med Phys 2020; 47:3054-3063. [PMID: 32277703 DOI: 10.1002/mp.14173] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 03/09/2020] [Accepted: 03/31/2020] [Indexed: 12/13/2022] Open
Abstract
INTRODUCTION This work describes the development of a novel radiomics phantom designed for magnetic resonance imaging (MRI) that can be used in a multicenter setting. The purpose of this study is to assess the stability and reproducibility of MRI-based radiomic features using this phantom across different MRI scanners. METHODS & MATERIALS A set of phantoms were three-dimensional (3D) printed using MRI visible materials. One set of phantoms were imaged on seven MRI scanners and one was imaged on one MRI scanner. Radiomics analysis of the phantoms, which included first-order features, shape and texture features was performed. Intraclass correlation coefficient (ICC) was used to assess the stability of radiomic features across eight scanners and the reproducibility of two printed models on one scanner. Coefficient of variation (COV) was used to assess the reproducibility of radiomics measurements in the phantom on a single scanner. RESULTS The phantom models provide sufficient signal-to-noise and contrast in all the tumor models permitting robust automatic segmentation. During a 12-month period of monitoring, the phantom material was stable with T1 and T2 of 150.7 ± 6.7 ms and 56.1 ± 3.9 ms, respectively. Of all the radiomic features computed, 34 of 69 had COV < 10%. Features from first-order statistics were the most robust in stability across the eight scanners with eight of 12 (67%) having high stability. About 29 of 50 (58%) texture features had high stability and no shape features had high stability features across the eight scanners. CONCLUSION A novel MRI radiomics phantom has been developed to assess the reproducibility and stability of MRI-based radiomic features across multiple institutions. The variation in radiomic feature stability demonstrates the need for caution when interpreting these features for clinical studies.
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Affiliation(s)
- Robba Rai
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Liverpool and Macarthur Cancer Therapy Centre, Liverpool Hospital, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Lois C Holloway
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Liverpool and Macarthur Cancer Therapy Centre, Liverpool Hospital, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Centre of Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia.,Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia
| | - Carsten Brink
- Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark.,Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Matthew Field
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Rasmus L Christiansen
- Laboratory of Radiation Physics, Odense University Hospital, Odense, Denmark.,Institute of Clinical Research, University of Southern Denmark, Odense, Denmark
| | - Yu Sun
- Institute of Medical Physics, School of Physics, University of Sydney, Sydney, NSW, Australia
| | - Michael B Barton
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Liverpool and Macarthur Cancer Therapy Centre, Liverpool Hospital, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia
| | - Gary P Liney
- South Western Sydney Clinical School, University of New South Wales, Liverpool, NSW, 2170, Australia.,Liverpool and Macarthur Cancer Therapy Centre, Liverpool Hospital, Liverpool, NSW, 2170, Australia.,Ingham Institute for Applied Medical Research, Liverpool, NSW, 2170, Australia.,Centre of Radiation Physics, University of Wollongong, Wollongong, NSW, 2522, Australia
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24
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Drakos T, Giannakou M, Menikou G, Ioannides C, Damianou C. An improved method to estimate ultrasonic absorption in agar-based gel phantom using thermocouples and MR thermometry. ULTRASONICS 2020; 103:106089. [PMID: 32045747 DOI: 10.1016/j.ultras.2020.106089] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 12/30/2019] [Accepted: 01/05/2020] [Indexed: 06/10/2023]
Abstract
In this paper, a novel experimental set-up was developed that measures the absorption coefficient. The proposed system was evaluated in an agar-based gel phantom. The new experimental system provides accurate and fast measurement of the rate of temperature change within the phantom. The rate of temperature change was measured using thermocouple and was confirmed using MR thermometry. An ultrasonic transducer with a broad beam was used in order to reduce the conduction effect. The absorption coefficient of the agar-based phantom was 0.26 dB/cm-MHz using 4% agar, 30% evaporated milk and 4% silica. The absorption coefficient increased by increasing the volume of the evaporated milk, and agar. The absorption coefficient increased at low silica concentration (<4%) and then decreased at higher concentration of silica (>4%). By proper selection of evaporated milk, agar and silica concentration, it is possible to achieve similar coefficient like in soft tissues. Acoustic absorption measurement is considered as a difficult measurement in ultrasonics because obtaining the precise temperature change in the focus is challenging. Due to the quick and accurate placement of the thermocouple at the ultrasonic beam, it is possible with the proposed system to perform absorption measurement is less than one minute.
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Affiliation(s)
- T Drakos
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | - M Giannakou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | - G Menikou
- Medical Physics Division, General Hospital of Nicosia, Nicosia, Cyprus
| | - C Ioannides
- Radiology Department, Ygia Polyclinic, Limassol, Cyprus
| | - C Damianou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
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Damianou C, Giannakou M, Menikou G, Ioannou L. Magnetic resonance imaging-guided focused ultrasound robotic system with the subject placed in the prone position. ACTA ACUST UNITED AC 2020. [DOI: 10.4103/digm.digm_2_20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Parthasarathy J, Krishnamurthy R, Ostendorf A, Shinoka T, Krishnamurthy R. 3D printing with MRI in pediatric applications. J Magn Reson Imaging 2019; 51:1641-1658. [PMID: 31329332 DOI: 10.1002/jmri.26870] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 07/01/2019] [Accepted: 07/01/2019] [Indexed: 12/12/2022] Open
Abstract
3D printing (3DP) applications for clinical evaluation, preoperative planning, patient and trainee education, and simulation has increased in the past decade. Most of the applications are found in cardiovascular, head and neck, orthopedic, neurological, urological, and oncological surgical cases. This review has three parts. The first part discusses the technical pathway to realizing a physical model, 3DP considerations in pediatric MRI image acquisition, data and resolution requirements, and related structural segmentation and postprocessing steps needed to generalize both virtual and physical models. Standard practices and processing software used in these processes will be assessed. The second part discusses complementary examples in pediatric applications, including cases from cardiology, neuroradiology, neurology, and neurosurgery, head and neck, orthopedics, pelvic and urological applications, oncological applications, and fetal imaging. The third part explores other 3D printing applications and considerations such as using 3DP to develop tissue-specific phantoms and devices for testing in the MR environment, to educate patients and their families, to train clinicians and students, and facility requirements for building a 3DP program. Level of Evidence: 5 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2020;51:1641-1658.
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Affiliation(s)
| | | | - Adam Ostendorf
- Department of Neurology Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Toshiharu Shinoka
- Department of Cardiothoracic Surgery, Nationwide Children's Hospital, Columbus, Ohio, USA
| | - Rajesh Krishnamurthy
- The Department of Radiology, Nationwide Children's Hospital, Columbus, Ohio, USA
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Rai R, Wang YF, Manton D, Dong B, Deshpande S, Liney GP. Development of multi-purpose 3D printed phantoms for MRI. ACTA ACUST UNITED AC 2019; 64:075010. [DOI: 10.1088/1361-6560/ab0b49] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Zhang F, Zhang H, Zhao H, He Z, Shi L, He Y, Ju N, Rong Y, Qiu J. Design and fabrication of a personalized anthropomorphic phantom using 3D printing and tissue equivalent materials. Quant Imaging Med Surg 2019; 9:94-100. [PMID: 30788250 DOI: 10.21037/qims.2018.08.01] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To fabricate an individualized anthropomorphic lung phantom with tissue-equivalent radiation attenuation properties using a cost-effective three-dimensional (3D) printing technique. Based on anonymized human chest CT images, the phantom contained a 3D-printed skin shell, filled with tissue equivalent materials with similar radiation attenuation characteristics. The filling materials were a mixture of CaCO3, MgO, agarose, NaCl, pearl powder and silica gel. The dose calculation accuracy of different treatment planning system (TPS) algorithms was validated and compared with the ion chamber measurements in the phantom, including tumor and surrounding normal tissues. The chest phantom was shown to represent a human's chest in terms of radiation attenuation property and human anatomy. The Hounsfield unit ranges were -60 to -100, 20 to 60, and 120 to 300 for fat, muscle, and bone, respectively. The actual measured values of the ionization chamber were 213.7 cGy for the tumor, 53.85 cGy for normal lung tissue, and 4.1 cGy for the spinal cord, compared to 214.1, 55.2, and 4.5 cGy, respectively, with use of the Monte Carlo algorithm in TPS. The application of 3D printing in anthropomorphic phantoms can improve personalized medical need and efficiency with reduce costs thus, can be used for radiation dose verification.
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Affiliation(s)
- Fuquan Zhang
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Haozhao Zhang
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Huihui Zhao
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Zhengzhong He
- Radiation Department, Hubei Cancer Hospital, Wuhan 430079, China
| | - Liting Shi
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Yaoyao He
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Nan Ju
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
| | - Yi Rong
- Department of Radiation Oncology, University of California Davis Comprehensive Cancer Center, Sacramento, CA, USA
| | - Jianfeng Qiu
- Medical Engineering and Technical Center, Taishan Medical University, Taian 271000, China
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Taghizadeh S, Labuda C, Mobley J. Development of a Tissue-Mimicking Phantom of the Brain for Ultrasonic Studies. ULTRASOUND IN MEDICINE & BIOLOGY 2018; 44:2813-2820. [PMID: 30274683 DOI: 10.1016/j.ultrasmedbio.2018.08.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 08/15/2018] [Accepted: 08/17/2018] [Indexed: 06/08/2023]
Abstract
Constructing tissue-mimicking phantoms of the brain for ultrasonic studies is complicated by the low backscatter coefficient of brain tissue, causing difficulties in simultaneously matching the backscatter and attenuation properties. In this work, we report on the development of a polyvinyl alcohol-based tissue-mimicking phantom with properties approaching those of human brain tissue. Polyvinyl alcohol was selected as the base material for the phantom as its properties can be varied by freeze-thaw cycling, variations in concentration and the addition of scattering inclusions, allowing some independent control of backscatter and attenuation. The ultrasonic properties (including speed of sound, attenuation and backscatter) were optimized using these methods with talc powder as an additive. It was determined that the ultrasonic properties of the phantom produced in this study are best matched to brain tissue in the frequency range 1-3 MHz, indicating its utility for laboratory ultrasonic studies in this frequency range.
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Affiliation(s)
- Somayeh Taghizadeh
- National Center for Physical Acoustics and Department of Physics and Astronomy, University of Mississippi, University, Mississippi, USA
| | - Cecille Labuda
- National Center for Physical Acoustics and Department of Physics and Astronomy, University of Mississippi, University, Mississippi, USA.
| | - Joel Mobley
- National Center for Physical Acoustics and Department of Physics and Astronomy, University of Mississippi, University, Mississippi, USA
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Giannakou M, Yiallouras C, Menikou G, Ioannides C, Damianou C. MRI-guided frameless biopsy robotic system with the inclusion of unfocused ultrasound transducer for brain cancer ablation. Int J Med Robot 2018; 15:e1951. [PMID: 30157310 DOI: 10.1002/rcs.1951] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 08/04/2018] [Accepted: 08/06/2018] [Indexed: 11/10/2022]
Abstract
BACKGROUND A magnetic resonance image (MRI) guided robotic system dedicated for brain biopsy was developed. The robotic system carries a biopsy needle and a small rectangular unfocused, single element, planar ultrasonic transducer which can be potentially utilized to ablate small and localized brain cancer. MATERIALS AND METHODS The robotic device includes six computer-controlled axes. An agar-based phantom was developed which included an olive that mimics brain target. A rectangular ultrasonic transducer operated at 4 MHz was used. RESULTS The functionality of the robotic system was assessed by means of ultrasound imaging, MRI imaging, and MR thermometry, demonstrating effective targeting. The heating capabilities of the ultrasonic transducer were also evaluated. CONCLUSIONS A functional MRI-guided robotic system was produced which can perform frameless brain biopsy. In the future, if a tumour is proven malignant, the needle can be pulled-out and a small ultrasonic transducer can be inserted to ablate the tumour.
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Affiliation(s)
- Marinos Giannakou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | | | - Georgios Menikou
- Department of Bioengineering, City University, London, UK.,R&D, MEDSONIC LTD, Limassol, Cyprus
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Corea J, Ye P, Seo D, Butts-Pauly K, Arias AC, Lustig M. Printed Receive Coils with High Acoustic Transparency for Magnetic Resonance Guided Focused Ultrasound. Sci Rep 2018; 8:3392. [PMID: 29467432 PMCID: PMC5821831 DOI: 10.1038/s41598-018-21687-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 02/01/2018] [Indexed: 01/20/2023] Open
Abstract
In magnetic resonance guided focused ultrasound (MRgFUS) therapy sound waves are focused through the body to selectively ablate difficult to access lesions and tissues. A magnetic resonance imaging (MRI) scanner non-invasively tracks the temperature increase throughout the tissue to guide the therapy. In clinical MRI, tightly fitted hardware comprised of multichannel coil arrays are required to capture high quality images at high spatiotemporal resolution. Ablating tissue requires a clear path for acoustic energy to travel but current array materials scatter and attenuate acoustic energy. As a result coil arrays are placed outside of the transducer, clear of the beam path, compromising imaging speed, resolution, and temperature accuracy of the scan. Here we show that when coil arrays are fabricated by additive manufacturing (i.e., printing), they exhibit acoustic transparency as high as 89.5%. This allows the coils to be placed in the beam path increasing the image signal to noise ratio (SNR) five-fold in phantoms and volunteers. We also characterize printed coil materials properties over time when submerged in the water required for acoustic coupling. These arrays offer high SNR and acceleration capabilities, which can address current challenges in treating head and abdominal tumors allowing MRgFUS to give patients better outcomes.
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Affiliation(s)
- Joseph Corea
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
| | - Patrick Ye
- Radiology, Stanford University, Stanford, CA, 94305, USA
| | - Dongjin Seo
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
| | | | - Ana Claudia Arias
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
| | - Michael Lustig
- Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA.
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Rai R, Manton D, Jameson MG, Josan S, Barton MB, Holloway LC, Liney GP. 3D printed phantoms mimicking cortical bone for the assessment of ultrashort echo time magnetic resonance imaging. Med Phys 2017; 45:758-766. [DOI: 10.1002/mp.12727] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2017] [Revised: 11/13/2017] [Accepted: 12/03/2017] [Indexed: 11/08/2022] Open
Affiliation(s)
- Robba Rai
- South Western Sydney Clinical School; University of New South Wales; Liverpool NSW 2170 Australia
- Liverpool and Macarthur Cancer Therapy Centre; Liverpool Hospital; Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
| | - David Manton
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
| | - Michael G. Jameson
- South Western Sydney Clinical School; University of New South Wales; Liverpool NSW 2170 Australia
- Liverpool and Macarthur Cancer Therapy Centre; Liverpool Hospital; Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
- Centre of Radiation Physics; University of Wollongong; Wollongong NSW 2522 Australia
| | - Sonal Josan
- Siemens Healthcare; Melbourne Vic. 3207 Australia
| | - Michael B. Barton
- South Western Sydney Clinical School; University of New South Wales; Liverpool NSW 2170 Australia
- Liverpool and Macarthur Cancer Therapy Centre; Liverpool Hospital; Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
| | - Lois C. Holloway
- South Western Sydney Clinical School; University of New South Wales; Liverpool NSW 2170 Australia
- Liverpool and Macarthur Cancer Therapy Centre; Liverpool Hospital; Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
- Centre of Radiation Physics; University of Wollongong; Wollongong NSW 2522 Australia
- Institute of Medical Physics; School of Physics; University of Sydney; Sydney NSW Australia
| | - Gary P. Liney
- South Western Sydney Clinical School; University of New South Wales; Liverpool NSW 2170 Australia
- Liverpool and Macarthur Cancer Therapy Centre; Liverpool Hospital; Liverpool NSW 2170 Australia
- Ingham Institute for Applied Medical Research; Liverpool NSW 2170 Australia
- Centre of Radiation Physics; University of Wollongong; Wollongong NSW 2522 Australia
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Budak E, Beytar F, Özdemir M, Susam BN, Göker M, Ünlü A, Eroğul O. Lower limb phantom design and production for blood flow and pressure tests. EUROBIOTECH JOURNAL 2017. [DOI: 10.24190/issn2564-615x/2017/04.04] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Abstract
Phantoms are specifically designed objects that are utilized or imaged to evaluate, analyze and tune the performance of experimental devices. In this project, it is aimed to design a phantom that responds in a similar manner with how human blood circulation would act in specific flow and pressure tests such as pulse measurement. Ballistic gelatin is a member of hydrogel family with 250 Bloom value which resembles human muscle tissue in terms of mechanical features. That’s why we carried out a uniaxial compression test on our gelatin sample to analyze its similarity of human muscle tissue in terms of elastic modulus, stiffness and rupture strength. Test results indicated that our gelatin sample has approximate values with organic human muscle tissue. Designed model was X-rayed and the similarities of the model to human texture were compared. After producing of lower limb phantoms, we carried out a circulation test through them by the aid of a peristaltic pump to simulate the actual blood circulation of human body limbs. This designed phantom is made ready for available flow and pressure tests.
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Affiliation(s)
- Erdem Budak
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
| | - Faruk Beytar
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
| | - Mertcan Özdemir
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
| | - Beyza Nur Susam
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
| | - Meriç Göker
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
| | - Aytekin Ünlü
- Department of General Surgery, Gülhane Training and Research Hospital, Ankara , Turkey
| | - Osman Eroğul
- Department of Biomedical Engineering,- TOBB University of Economics and Technology, Ankara , Turkey
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Menikou G, Yiannakou M, Yiallouras C, Ioannides C, Damianou C. MRI-compatible breast/rib phantom for evaluating ultrasonic thermal exposures. Int J Med Robot 2017; 14. [DOI: 10.1002/rcs.1849] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 01/12/2023]
Affiliation(s)
| | | | - Christos Yiallouras
- Cyprus University of Technology; Limassol Cyprus
- MEDSONIC LTD; Limassol Cyprus
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Dadakova T, Krafft AJ, Özen AC, Bock M. Optimization of acoustic radiation force imaging: Influence of timing parameters on sensitivity. Magn Reson Med 2017; 79:981-986. [PMID: 28618069 DOI: 10.1002/mrm.26734] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 02/11/2017] [Accepted: 04/03/2017] [Indexed: 11/09/2022]
Abstract
PURPOSE Optimization of timing parameters for MR-guided ARFI to achieve the highest displacement signal-to-noise ratio (SNRd ). THEORY AND METHODS In MR-guided ARFI the phase change induced by motion encoding gradients (MEGs) is measured to assess tissue displacement. The sensitivity of this encoding procedure depends on several timing parameters, such as the MEG duration and the offset time between ultrasound (US) and MEG. Furthermore, mechanical and MR tissue constants and MEG schemes (bipolar or three-lobed) influence SNRd . Optimal timing parameters were determined in simulations for bipolar and three-lobed MEGs, and the results were compared with measurements. To provide clinically usable timing parameters, physiologically relevant ranges of tissue constants were considered. RESULTS For the considered ranges of tissue constants, optimal timing parameters provide only 6% higher SNRd for bipolar than for three-lobed MEG. Three-lobed MEG is less sensitive to motion as confirmed in phantom experiments. Bipolar MEG can use approximately 1.5-fold shorter MEG durations. CONCLUSION Both bipolar and three-lobed MEGs can yield approximately the same SNRd if the optimal timing parameters are chosen. Bipolar MEG allows for shorter durations, which is preferable if deposition of US energy needs to be minimized, and three-lobed MEG is more suitable when residual motion compensation is necessary. Magn Reson Med 79:981-986, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Tetiana Dadakova
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Axel Joachim Krafft
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ali Caglar Özen
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Menikou G, Damianou C. Acoustic and thermal characterization of agar based phantoms used for evaluating focused ultrasound exposures. J Ther Ultrasound 2017; 5:14. [PMID: 28572977 PMCID: PMC5452295 DOI: 10.1186/s40349-017-0093-z] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 03/01/2017] [Indexed: 11/26/2022] Open
Abstract
Background This study describes a series of experimental work completed towards characterizing candidate materials for fabricating brain and muscle tissue mimicking phantoms. Methods The acoustic speed, attenuation, impedance, thermal diffusivity, specific heat and thermal conductivity were measured. Results The resulting brain (2% w/v agar-1.2% w/v Silica Dioxide-25%v/v evaporated milk) and muscle tissue recipe (2% w/v agar-2% w/v Silica Dioxide-40%v/v evaporated milk) introduced a total attenuation coefficient of 0.59 dB/cm-MHz and 0.99 dB/cm-MHz respectively. Acrylonitrile Butadiene Styrene (ABS) possessed an attenuation coefficient of 16 dB/cm at 1 MHz which was found within the very wide range of attenuation coefficient values of human bones in literature. The thermal conductivity of the brain tissue phantom was estimated at 0.52 W/m°C and at 0.57 W/m.°Cfor the muscle. These values demonstrated that the proposed recipes conducted heat similar to the majority of most soft tissues found from bibliography. The soft tissue phantoms were also evaluated for their thermal repeatability after treating them repeatedly at different locations with the same sonication protocol and configuration. The average coefficient of variation of the maximum temperature at focus between the different locations was 2.6% for the brain phantom and 2.8% for the muscle phantom. Conclusions The proposed phantom closely matched the acoustic and thermal properties of tissues. Experiments using MR thermometry demonstrated the usefulness of this phantom to evaluate ultrasonic exposures.
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Affiliation(s)
- Georgios Menikou
- Research Centre for Biomedical Engineering, City, University of London, London, UK
| | - Christakis Damianou
- Electrical Engineering Department, Cyprus University of Technology, Limassol, Cyprus
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Yiannakou M, Menikou G, Yiallouras C, Ioannides C, Damianou C. MRI guided focused ultrasound robotic system for animal experiments. Int J Med Robot 2017; 13. [PMID: 28211622 DOI: 10.1002/rcs.1804] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Revised: 12/12/2016] [Accepted: 12/13/2016] [Indexed: 11/07/2022]
Abstract
BACKGROUND In this paper an MRI-guided focused ultrasound (MRgFUS) robotic system was developed that can be used for conducting experiments in small animals.The target for this robotic system regarding motion was to move a therapeutic ultrasound transducer in two Cartesian axes. METHODS A single element spherically focused transducer of 3 cm diameter, focusing at 7 cm and operating at 0.4 MHz was used. The positioning device incorporates only MRI compatible materials. The propagation of ultrasound is a bottom to top approach. The 2-D positioning device is controlled by custom-made software and a custom-made electronic system which controls the two piezoelectric motors. RESULTS The system was tested successfully in agar/silica/evaporated milk phantom for various tasks (robot motion, MR compatibility, and MR thermometry). The robotic system is capable of moving the focused ultrasound transducer to perform MR-guided focused ultrasound experiments in small animals. CONCLUSIONS This system has the potential to be deployed as a cost effective solution for performing experiments in small animals.
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Affiliation(s)
- Marinos Yiannakou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | | | - Christos Yiallouras
- Electrical Engineering Department, Cyprus University of Technology, Cyprus.,R&D, MEDSONIC LTD, Limassol, Cyprus
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Papadopoulos N, Menikou G, Yiannakou M, Yiallouras C, Ioannides K, Damianou C. Evaluation of a small flat rectangular therapeutic ultrasonic transducer intended for intravascular use. ULTRASONICS 2017; 74:196-203. [PMID: 27835808 DOI: 10.1016/j.ultras.2016.10.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 09/26/2016] [Accepted: 10/28/2016] [Indexed: 06/06/2023]
Abstract
BACKGROUND The aim of the proposed study was to evaluate the performance of a flat rectangular (2×10mm2) transducer operating at 4MHz. The intended application of this transducer is intravascular treatment of thrombosis and atherosclerosis. METHODS The transducer's thermal capabilities were tested in two different gel phantoms. MR thermometry was used to demonstrate the thermal capabilities of this type of transducer. RESULTS Temperature measurements demonstrated that this simple and small transducer adequately produced high temperatures, which can be utilized for therapeutic purposes. These high temperatures were confirmed using thermocouple and MR measurements. Pulsed ultrasound in combination with thrombolytic drugs and microbubbles was utilized to eliminate porcine thrombi. CONCLUSIONS The proposed transducer has the potentials to treat atherosclerotic lesions using the thermal properties of ultrasound, since high temperatures can be achieved in less than 5s. The results revealed that the destruction of thrombi using pulsed ultrasound requires long exposure time and high microbubble dosage.
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Affiliation(s)
- N Papadopoulos
- Department of Bioengineering, City University, London, UK
| | - G Menikou
- Department of Bioengineering, City University, London, UK
| | - M Yiannakou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus
| | - C Yiallouras
- Electrical Engineering Department, Cyprus University of Technology, Cyprus; R&D, MEDSONIC LTD, Limassol, Cyprus
| | - K Ioannides
- Radiology, Ygia Polyclinic, Limassol, Cyprus
| | - C Damianou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus.
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Hoang D, Perrault D, Stevanovic M, Ghiassi A. Surgical applications of three-dimensional printing: a review of the current literature & how to get started. ANNALS OF TRANSLATIONAL MEDICINE 2016; 4:456. [PMID: 28090512 DOI: 10.21037/atm.2016.12.18] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Three dimensional (3D) printing involves a number of additive manufacturing techniques that are used to build structures from the ground up. This technology has been adapted to a wide range of surgical applications at an impressive rate. It has been used to print patient-specific anatomic models, implants, prosthetics, external fixators, splints, surgical instrumentation, and surgical cutting guides. The profound utility of this technology in surgery explains the exponential growth. It is important to learn how 3D printing has been used in surgery and how to potentially apply this technology. PubMed was searched for studies that addressed the clinical application of 3D printing in all surgical fields, yielding 442 results. Data was manually extracted from the 168 included studies. We found an exponential increase in studies addressing surgical applications for 3D printing since 2011, with the largest growth in craniofacial, oromaxillofacial, and cardiothoracic specialties. The pertinent considerations for getting started with 3D printing were identified and are discussed, including, software, printing techniques, printing materials, sterilization of printing materials, and cost and time requirements. Also, the diverse and increasing applications of 3D printing were recorded and are discussed. There is large array of potential applications for 3D printing. Decreasing cost and increasing ease of use are making this technology more available. Incorporating 3D printing into a surgical practice can be a rewarding process that yields impressive results.
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Affiliation(s)
- Don Hoang
- USC Plastic and Reconstructive Surgery, Los Angeles, CA, USA
| | - David Perrault
- Division of Plastic and Reconstructive Surgery, Department of Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Milan Stevanovic
- Department of Orthopaedic Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
| | - Alidad Ghiassi
- Department of Orthopaedic Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA
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Randazzo M, Pisapia JM, Singh N, Thawani JP. 3D printing in neurosurgery: A systematic review. Surg Neurol Int 2016; 7:S801-S809. [PMID: 27920940 PMCID: PMC5122816 DOI: 10.4103/2152-7806.194059] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 06/24/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The recent expansion of three-dimensional (3D) printing technology into the field of neurosurgery has prompted a widespread investigation of its utility. In this article, we review the current body of literature describing rapid prototyping techniques with applications to the practice of neurosurgery. METHODS An extensive and systematic search of the Compendex, Scopus, and PubMed medical databases was conducted using keywords relating to 3D printing and neurosurgery. Results were manually screened for relevance to applications within the field. RESULTS Of the search results, 36 articles were identified and included in this review. The articles spanned the various subspecialties of the field including cerebrovascular, neuro-oncologic, spinal, functional, and endoscopic neurosurgery. CONCLUSIONS We conclude that 3D printing techniques are practical and anatomically accurate methods of producing patient-specific models for surgical planning, simulation and training, tissue-engineered implants, and secondary devices. Expansion of this technology may, therefore, contribute to advancing the neurosurgical field from several standpoints.
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Affiliation(s)
- Michael Randazzo
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jared M. Pisapia
- Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Nickpreet Singh
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jayesh P. Thawani
- Department of Neurosurgery, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Menikou G, Yiannakou M, Yiallouras C, Ioannides C, Damianou C. MRI-compatible bone phantom for evaluating ultrasonic thermal exposures. ULTRASONICS 2016; 71:12-19. [PMID: 27261569 DOI: 10.1016/j.ultras.2016.05.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Revised: 05/15/2016] [Accepted: 05/24/2016] [Indexed: 06/05/2023]
Abstract
OBJECTIVE The goal of the proposed study was the development of a magnetic resonance imaging (MRI) compatible bone phantom suitable for evaluating focused ultrasound protocols. MATERIALS AND METHODS High resolution CT images were used to segment femur bone. The segmented model was manufactured with (Acrylonitrile Butadiene Styrene) ABS plastic using a 3-D printer. The surrounding skeletal muscle tissue was mimicked using an agar-silica-evaporated milk gel (2% w/v-2% w/v-40% v/v). MR thermometry was used to evaluate the exposures of the bone phantom to focused ultrasound. RESULTS The estimated agar-silica-evaporated milk gel's T1 and T2 relaxation times in a 1.5T magnetic field were 776ms and 66ms respectively. MR thermometry maps indicated increased temperature adjacent to the bone, which was also shown in situations of real bone/tissue interfaces. CONCLUSION Due to growing interest of using MRI guided Focused Ultrasound Surgery (MRgFUS) in palliating bone cancer patients at terminal stages of the disease, the proposed bone phantom can be utilized as a very useful tool for evaluating ultrasonic protocols, thus minimizing the need for animal models. The estimated temperature measured and its distribution near the bone phantom/agar interface which was similar to temperatures recorded in real bone ablation with FUS, confirmed the phantom's functionality.
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Affiliation(s)
| | | | - Christos Yiallouras
- Cyprus University of Technology, Limassol, Cyprus; MEDSONIC LTD, Limassol, Cyprus
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Papadopoulos N, Damianou C. In Vitro Evaluation of Focused Ultrasound-Enhanced TNK-Tissue Plasminogen Activator-Mediated Thrombolysis. J Stroke Cerebrovasc Dis 2016; 25:1864-77. [PMID: 27156900 DOI: 10.1016/j.jstrokecerebrovasdis.2016.03.051] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Accepted: 03/27/2016] [Indexed: 12/01/2022] Open
Abstract
INTRODUCTION The low and incomplete recanalization performance of thrombolytic therapy in patients with acute ischemic stroke has created the need to use focused ultrasound (FUS) energy as a way to enhance thrombolysis efficiency (sonothrombolysis). Using an in vitro flow model, the role of various parameters involved in FUS-enhanced tenecteplase (TNK-tPA [tissue plasminogen activator])-mediated thrombolysis was evaluated. MATERIALS AND METHODS Fully retracted porcine blood clots were used for the proposed parametric studies. A spherically FUS transducer (4 cm diameter), focusing at 10 cm and operating at 1 MHz, was used. Pulsed ultrasound protocols were applied that maintained temperature elevation at the focus that never exceeded 1°C. Thrombolysis efficiency was measured as the relative reduction in the mass of the clot. RESULTS The role of various properties on thrombolysis efficacy was examined. These various properties are the acoustic power, the TNK-tPA concentration, the flow rate, the exposure time, the pulse length, the pulse repetition frequency, the duty factor, the formation of standing waves, the acoustic medium, and the administration of microbubbles. Study results have demonstrated that the parameters examined influenced thrombolysis efficacy and the degree of thrombolysis achieved by each parameter was measured. CONCLUSIONS Study findings helped us to optimize the treatment protocol for 1 MHz pulsed FUS that maximizes the thrombolytic efficacy of TNK-tPA, which potentially could be applied for therapeutic purposes. The outcome of the study showed poor thrombolysis efficacy, as with 30 minutes of FUS treatment only 370 mg of clot was removed.
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Affiliation(s)
| | - Christakis Damianou
- Electrical Engineering Department, Cyprus University of Technology, Limassol, Cyprus.
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Mitsouras D, Lee TC, Liacouras P, Ionita CN, Pietilla T, Maier SE, Mulkern RV. Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation. Magn Reson Med 2016; 77:613-622. [PMID: 26864335 DOI: 10.1002/mrm.26136] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Revised: 12/23/2015] [Accepted: 01/05/2016] [Indexed: 12/27/2022]
Abstract
PURPOSE To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties. METHODS A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom were measured and 1 H spectra were acquired to provide insight into the nature of the proton signal. Finally, T2 -weighted imaging was performed during cryoablation of the model. RESULTS The printed model produced a CT signal of 102 ± 8 Hounsfield unit, and an MR signal roughly 1/3rd that of saline in short echo time/short repetition time GRE MRI (456 ± 36 versus 1526 ± 121 arbitrary signal units). Compared with the model designed from the in vivo CT scan, the printed model differed by 0.13 ± 0.11 mm in CT, and 0.62 ± 0.28 mm in MR. The printed material had T2 ∼32 ms, T2*∼7 ms, T1 ∼193 ms, and a very small diffusion coefficient less than olive oil. MRI monitoring of the cryoablation demonstrated iceball formation similar to an in vivo procedure. CONCLUSION Current 3D printing technology can be used to print anatomically accurate phantoms that can be imaged by both CT and MRI. Such models can be used to simulate MRI-guided interventions such as cryosurgeries. Future development of the proposed technique can potentially lead to printed models that depict different tissues and anatomical structures with different MR signal characteristics. Magn Reson Med 77:613-622, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Dimitris Mitsouras
- Applied Imaging Science Lab, Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Thomas C Lee
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA
| | - Peter Liacouras
- 3D Medical Applications Center, Department of Radiology, Walter Reed National Military Medical Center, Bethesda, Maryland, USA
| | - Ciprian N Ionita
- Department of Biomedical Engineering, State University of New York at Buffalo, Buffalo, New York, USA
| | | | - Stephan E Maier
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.,Department of Radiology, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden
| | - Robert V Mulkern
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, USA.,Department of Radiology, Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Sagias G, Yiallouras C, Ioannides K, Damianou C. An MRI-conditional motion phantom for the evaluation of high-intensity focused ultrasound protocols. Int J Med Robot 2015; 12:431-41. [PMID: 27593511 DOI: 10.1002/rcs.1709] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2015] [Indexed: 11/11/2022]
Abstract
BACKGROUND The respiratory motion of abdominal organs is a serious obstacle in high-intensity focused ultrasound (HIFU) treatment with magnetic resonance imaging (MRI) guidance. In this study, a two-dimensional (2D) MRI-conditional motion phantom device was developed in order to evaluate HIFU protocols in synchronized and non-synchronized ablation of moving targets. MATERIALS AND METHODS The 2D phantom device simulates the respiratory motion of moving organs in both the left-right and craniocaudal directions. The device consists of MR-conditional materials which have been produced by a three-dimensional (3D) printer. RESULTS The MRI compatibility of the motion phantom was tested successfully in an MRI scanner. In vitro experiments were carried out to evaluate HIFU ablation protocols that are minimally affected by target motion. CONCLUSION It was shown that only in synchronized mode does HIFU produce thermal lesions, as tested on a gel phantom mimicking the moving target. The MRI-conditional phantom device was shown to be functional for its purpose and can be used as an evaluation tool for testing HIFU protocols for moving targets in an MRI environment. Copyright © 2015 John Wiley & Sons, Ltd.
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