1
|
Zubair M, Adams MS, Diederich CJ. Deployable ultrasound applicators for endoluminal delivery of volumetric hyperthermia. Int J Hyperthermia 2021; 38:1188-1204. [PMID: 34376103 DOI: 10.1080/02656736.2021.1936216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To investigate the design of an endoluminal deployable ultrasound applicator for delivering volumetric hyperthermia to deep tissue sites as a possible adjunct to radiation and chemotherapy. METHOD This study considers an ultrasound applicator consisting of two tubular transducers situated at the end of a catheter assembly, encased within a distensible conical shaped balloon-based reflector that redirects acoustic energy distally into the tissue. The applicator assembly can be inserted endoluminally or laparoscopically in a compact form and expanded after delivery to the target site. Comprehensive acoustic and biothermal simulations and parametric studies were employed in generalized 3D and patient-specific pancreatic head and body tumor models to characterize the acoustic performance and evaluate heating capabilities of the applicator by investigating the device at a range of operating frequencies, tissue acoustic and thermal properties, transducer configurations, power modulation, applicator positioning, and by analyzing the resultant 40, 41, and 43 °C isothermal volumes and penetration depth of the heating volume. Intensity distributions and volumetric temperature contours were calculated to define moderate hyperthermia boundaries. RESULTS Parametric studies demonstrated the frequency selection to control volume and depth of therapeutic heating from 62 to 22 cm3 and 4 to 2.6 cm as frequency ranges from 1 MHz to 4.7 MHz, respectively. Width of the heating profile tracks closely with the aperture. Water cooling within the reflector balloon was effective in controlling temperature to 37 °C maximum within the luminal wall. Patient-specific studies indicated that applicators with extended OD in the range of 3.6-6.2 cm with 0.5-1 cm long and 1 cm OD transducers can heat volumes of 1.1-7 cm3, 3-26 cm3, and 3.3-37.4 cm3 of pancreatic body and head tumors above 43, 41, and 40 °C, respectively. CONCLUSION In silico studies demonstrated the feasibility of combining endoluminal ultrasound with an integrated expandable balloon reflector for delivering volumetric hyperthermia in regions adjacent to body lumens and cavities.
Collapse
Affiliation(s)
- Muhammad Zubair
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Matthew S Adams
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Chris J Diederich
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| |
Collapse
|
2
|
Campwala Z, Szewczyk B, Maietta T, Trowbridge R, Tarasek M, Bhushan C, Fiveland E, Ghoshal G, Heffter T, Gandomi K, Carvalho PA, Nycz C, Jeannotte E, Staudt M, Nalwalk J, Hellman A, Zhao Z, Burdette EC, Fischer G, Yeo D, Pilitsis JG. Predicting ablation zones with multislice volumetric 2-D magnetic resonance thermal imaging. Int J Hyperthermia 2021; 38:907-915. [PMID: 34148489 PMCID: PMC9284994 DOI: 10.1080/02656736.2021.1936215] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
BACKGROUND High-intensity focused ultrasound (HIFU) serves as a noninvasive stereotactic system for the ablation of brain metastases; however, treatments are limited to simple geometries and energy delivery is limited by the high acoustic attenuation of the calvarium. Minimally-invasive magnetic resonance-guided robotically-assisted (MRgRA) needle-based therapeutic ultrasound (NBTU) using multislice volumetric 2-D magnetic resonance thermal imaging (MRTI) overcomes these limitations and has potential to produce less collateral tissue damage than current methods. OBJECTIVE To correlate multislice volumetric 2-D MRTI volumes with histologically confirmed regions of tissue damage in MRgRA NBTU. METHODS Seven swine underwent a total of 8 frontal MRgRA NBTU lesions. MRTI ablation volumes were compared to histologic tissue damage on brain sections stained with 2,3,5-triphenyltetrazolium chloride (TTC). Bland-Altman analyses and correlation trends were used to compare MRTI and TTC ablation volumes. RESULTS Data from the initial and third swine's ablations were excluded due to sub-optimal tissue staining. For the remaining ablations (n = 6), the limits of agreement between the MRTI and histologic volumes ranged from -0.149 cm3 to 0.252 cm3 with a mean difference of 0.052 ± 0.042 cm3 (11.1%). There was a high correlation between the MRTI and histology volumes (r2 = 0.831) with a strong linear relationship (r = 0.868). CONCLUSION We used a volumetric MRTI technique to accurately track thermal changes during MRgRA NBTU in preparation for human trials. Improved volumetric coverage with MRTI enhanced our delivery of therapy and has far-reaching implications for focused ultrasound in the broader clinical setting.
Collapse
Affiliation(s)
- Zahabiya Campwala
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA
| | - Benjamin Szewczyk
- Department of Neurosurgery, Albany Medical Center, Albany, NY, USA.,Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Teresa Maietta
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA
| | - Rachel Trowbridge
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA
| | | | | | | | | | | | - Katie Gandomi
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, USA
| | | | - Christopher Nycz
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Erin Jeannotte
- Animal Resources Facility, Albany Medical Center, Albany, NY, USA
| | - Michael Staudt
- Department of Neurosurgery, Albany Medical Center, Albany, NY, USA
| | - Julia Nalwalk
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA
| | - Abigail Hellman
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA
| | - Zhanyue Zhao
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, USA
| | | | - Gregory Fischer
- Robotics Engineering Department, Worcester Polytechnic Institute, Worcester, MA, USA
| | - Desmond Yeo
- GE Global Research Center, Niskayuna, NY, USA
| | - Julie G Pilitsis
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, NY, USA.,Department of Neurosurgery, Albany Medical Center, Albany, NY, USA
| |
Collapse
|
3
|
Gandomi KY, Carvalho PAWG, Tarasek M, Fiveland EW, Bhushan C, Williams E, Neubauer P, Zhao Z, Pilitsis J, Yeo D, Nycz CJ, Burdette E, Fischer GS. Modeling of Interstitial Ultrasound Ablation for Continuous Applicator Rotation With MR Validation. IEEE Trans Biomed Eng 2021; 68:1838-1846. [PMID: 32924937 PMCID: PMC8189669 DOI: 10.1109/tbme.2020.3023849] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The primary objective of cancer intervention is the selective removal of malignant cells while conserving surrounding healthy tissues. However, the accessibility, size and shape of the cancer can make achieving appropriate margins a challenge. One minimally invasive treatment option for these clinical cases is interstitial needle based therapeutic ultrasound (NBTU). In this work, we develop a finite element model (FEM) capable of simulating continuous rotation of a directional NBTU applicator. The developed model was used to simulate the thermal deposition for different rotation trajectories. The actual thermal deposition patterns for the simulated trajectories were then evaluated using magnetic resonance thermal imaging (MRTI) in a porcine skin gelatin phantom. An MRI-compatible robot was used to control the rotation motion profile of the physical NBTU applicator to match the simulated trajectory. The model showed agreement when compared to experimental measurements with Pearson correlation coefficients greater than 0.839 when comparing temperature fields within an area of 12.6 mm radius from the ultrasound applicator. The average temperature error along a 6.3 mm radius profile from the applicator was 1.27 °C. The model was able to compute 1 s of thermal deposition by the applicator in 0.2 s on average with a 0.1 mm spatial resolution and 0.5 s time steps. The developed simulation demonstrates performance suitable for real-time control which may enable robotically-actuated closed-loop conformal tumor ablation.
Collapse
|
4
|
Patel NA, Nycz CJ, Carvalho PA, Gandomi KY, Gondokaryono R, Li G, Heffter T, Burdette EC, Pilitsis JG, Fischer GS. An Integrated Robotic System for MRI-Guided Neuroablation: Preclinical Evaluation. IEEE Trans Biomed Eng 2020; 67:2990-2999. [PMID: 32078530 PMCID: PMC7529397 DOI: 10.1109/tbme.2020.2974583] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVE Treatment of brain tumors requires high precision in order to ensure sufficient treatment while minimizing damage to surrounding healthy tissue. Ablation of such tumors using needle-based therapeutic ultrasound (NBTU) under real-time magnetic resonance imaging (MRI) can fulfill this need. However, the constrained space and strong magnetic field in the MRI bore restricts patient access limiting precise placement of the NBTU ablation tool. A surgical robot compatible with use inside the bore of an MRI scanner can alleviate these challenges. METHODS We present preclinical trials of a robotic system for NBTU ablation of brain tumors under real-time MRI guidance. The system comprises of an updated robotic manipulator and corresponding control electronics, the NBTU ablation system and applications for planning, navigation and monitoring of the system. RESULTS The robotic system had a mean translational and rotational accuracy of 1.39 ± 0.64 mm and 1.27 [Formula: see text] in gelatin phantoms and 3.13 ± 1.41 mm and 5.58 [Formula: see text] in 10 porcine trials while causing a maximum reduction in signal to noise ratio (SNR) of 10.3%. CONCLUSION The integrated robotic system can place NBTU ablator at a desired target location in porcine brain and monitor the ablation in realtime via magnetic resonance thermal imaging (MRTI). SIGNIFICANCE Further optimization of this system could result in a clinically viable system for use in human trials for various diagnostic or therapeutic neurosurgical interventions.
Collapse
|
5
|
Liu D, Adams M, Burdette EC, Diederich CJ. Dual-sectored transurethral ultrasound for thermal treatment of stress urinary incontinence: in silico studies in 3D anatomical models. Med Biol Eng Comput 2020; 58:1325-1340. [PMID: 32277340 DOI: 10.1007/s11517-020-02152-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/25/2020] [Indexed: 11/24/2022]
Abstract
The purpose of this study is to investigate the feasibility and performance of a stationary, non-focused dual-sectored tubular transurethral ultrasound applicator for thermal exposure of tissue regions adjacent to the urethra for treatment of stress urinary incontinence (SUI) through acoustic and biothermal simulations on 3D anatomical models. Parametric studies in a generalized tissue model over dual-sectored ultrasound applicator configurations (acoustic surface intensities, lateral active acoustic output sector angles, and durations) were performed. Selected configurations and delivery strategies were applied on 3D pelvic anatomical models. Temperature and thermal dose distributions on the target region and surrounding tissues were calculated. Endovaginal cooling was explored as a strategy to mitigate vaginal heating. The 75-90° dual-sectored transurethral tubular transducer (3.5 mm outer diameter (OD), 14 mm length, 6.5 MHz, 8.8-10.2 W/cm2) and 2-3-min sonication duration were selected from the parametric study for acoustic and biothermal simulations on anatomical models. The transurethral applicator with two opposing 75-90° active lateral tubular sectors can create two heated volumes for a total of up to 1.8 cm3 over 60 EM43 °C, with at least 10 mm radial penetration depth, 1.2 mm urethral sparing, and no lethal damage to the vagina and adjacent bone (< 60 EM43 °C). Endovaginal cooling can be applied to further reduce the vaginal wall exposure (< 15 EM43 °C). Simulations on 3D anatomical models indicate that dual-sectored transurethral ultrasound applicators can selectively heat pelvic floor tissue lateral to the mid-urethra in short treatment durations, without damaging adjacent vaginal and bone tissues, as a potential alternative treatment option for stress urinary incontinence. Graphical abstract Schema for in silico investigation of transurethral ultrasound thermal therapy applicator for minimally invasive treatment of SUI.
Collapse
Affiliation(s)
- Dong Liu
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Matthew Adams
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | | | - Chris J Diederich
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA.
| |
Collapse
|
6
|
Kim H, Wu H, Cho N, Zhong P, Mahmood K, Lyerly HK, Jiang X. Miniaturized Intracavitary Forward-Looking Ultrasound Transducer for Tissue Ablation. IEEE Trans Biomed Eng 2019; 67:2084-2093. [PMID: 31765299 DOI: 10.1109/tbme.2019.2954524] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
OBJECTIVE This paper aims to develop a miniaturized forward-looking ultrasound transducer for intracavitary tissue ablation, which can be used through an endoscopic device. The internal ultrasound (US) delivery is capable of directly interacting with the target tumor, resolving adverse issues of currently available US devices, such as unintended tissue damage and insufficient delivery of acoustic power. METHODS To transmit a high acoustic pressure from a small aperture (<3 mm), a double layer transducer (1.3 MHz) was designed and fabricated based on numerical simulations. The electric impedance and the acoustic pressure of the actual device was characterized with an impedance analyzer and a hydrophone. Ex vivo tissue ablation tests and temperature monitoring were then conducted with porcine livers. RESULTS The acoustic intensity of the transducer was 37.1 W/cm2 under 250 Vpp and 20% duty cycle. The tissue temperature was elevated to 51.8 °C with a 67 Hz pulse-repetition frequency. The temperature profile in the tissue indicated that ultrasound energy was effectively absorbed inside the tissue. During a 5-min sonification, an approximate tissue volume of 2.5 × 2.5 × 1.0 mm3 was ablated, resulting in an irreversible lesion. CONCLUSION This miniaturized US transducer is a promising medical option for the precise tissue ablation, which can reduce the risk of unintended tissue damage found in noninvasive US treatments. SIGNIFICANCE Having a small aperture (2 mm), the intracavitary device is capable of ablating a bio tissue in 5 min with a relatively low electric power (<17 W).
Collapse
|
7
|
Liu D, Adams MS, Burdette EC, Diederich CJ. Transurethral high-intensity ultrasound for treatment of stress urinary incontinence (SUI): simulation studies with patient-specific models. Int J Hyperthermia 2018; 34:1236-1247. [PMID: 29566562 PMCID: PMC6136964 DOI: 10.1080/02656736.2018.1456679] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 02/16/2018] [Accepted: 03/17/2018] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Stress urinary incontinence (SUI) is prevalent in adult women, attributed to weakened endopelvic supporting tissues, and typically treated using drugs and invasive surgical procedures. The objective of this in silico study is to explore transurethral high-intensity ultrasound for delivery of precise thermal therapy to the endopelvic tissues adjacent to the mid-urethra, to induce thermal remodeling as a potential minimally invasive treatment alternative. METHODS 3D acoustic (Rayleigh-Sommerfeld) and biothermal (Pennes bioheat) models of the ultrasound applicator and surrounding tissues were devised. Parametric studies over transducer configuration [frequency, radius-of-curvature (ROC)] and treatment settings (power, duration) were performed, and select cases on patient-specific models were used for further evaluation. Transient temperature and thermal dose distributions were calculated, and temperature and dose metrics reported. RESULTS Configurations using a 5-MHz curvilinear transducer (3.5 × 10 mm, 28 mm ROC) with single 90 s sonication can create heated zones with 11 mm penetration (>50 °C) while sparing the inner 1.8 mm (<45 °C) radial depth of the urethral mucosa. Sequential and discrete applicator rotations can sweep out bilateral coagulation volumes (1.4 W power, 15° rotations, 600 s total time), produce large volumetric (1124 mm³ above 60 EM43 °C) and wide angular (∼50.5° per lateral sweep) coverage, with up to 15.6 mm thermal penetration and at least 1.6 mm radial urethral protection (<5 EM43 °C). CONCLUSION Transurethral applicators with curvilinear ultrasound transducers can deliver spatially selective temperature elevations to lateral mid-urethral targets as a possible means to tighten the endopelvic fascia and adjacent tissues.
Collapse
Affiliation(s)
- Dong Liu
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Matthew S. Adams
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | | | - Chris J. Diederich
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| |
Collapse
|
8
|
Suomi V, Treeby B, Jaros J, Makela P, Anttinen M, Saunavaara J, Sainio T, Kiviniemi A, Blanco R. Transurethral ultrasound therapy of the prostate in the presence of calcifications: A simulation study. Med Phys 2018; 45:4793-4805. [PMID: 30216469 DOI: 10.1002/mp.13183] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 07/24/2018] [Accepted: 09/04/2018] [Indexed: 12/14/2022] Open
Abstract
PURPOSE Transurethral ultrasound therapy is an investigational treatment modality which could potentially be used for the localized treatment of prostate cancer. One of the limiting factors of this therapy is prostatic calcifications. These attenuate and reflect ultrasound and thus reduce the efficacy of the heating. The aim of this study is to investigate how prostatic calcifications affect therapeutic efficacy, and to identify the best sonication strategy when calcifications are present. METHODS Realistic computational models were used on clinical patient data in order to simulate different therapeutic situations with naturally occurring calcifications as well as artificial calcifications of different sizes (1-10 mm) and distances (5-15 mm). Furthermore, different sonication strategies were tested in order to deliver therapy to the untreated tissue regions behind the calcifications. RESULTS The presence of calcifications in front of the ultrasound field was found to increase the peak pressure by 100% on average while the maximum temperature only rose by 9% during a 20-s sonication. Losses in ultrasound energy were due to the relatively large acoustic impedance mismatch between the prostate tissue and the calcifications (1.63 vs 3.20 MRayl) and high attenuation coefficient (0.78 vs 2.64 dB/MHz1.1 /cm), which together left untreated tissue regions behind the calcifications. In addition, elevated temperatures were seen in the region between the transducer and the calcifications. Lower sonication frequencies (1-4 MHz) were not able to penetrate through the calcifications effectively, but longer sonication durations (20-60 s) with selective transducer elements were effective in treating the tissue regions behind the calcifications. CONCLUSIONS Prostatic calcifications limit the reach of therapeutic ultrasound treatment due to reflections and attenuation. The tissue regions behind the calcifications can possibly be treated using longer sonication durations combined with proper transducer element selection. However, caution should be taken with calcifications located close to sensitive organs such as the urethra, bladder neck, or rectal wall.
Collapse
Affiliation(s)
- Visa Suomi
- Department of Radiology, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Bradley Treeby
- Department of Medical Physics and Biomedical Engineering, University College London, Gower Street, London, WC1E 6BT, UK
| | - Jiri Jaros
- Centre of Excellence IT4Innovation, Faculty of Information Technology, Brno University of Technology, Bozetechova 1/2, 612 66, Brno, Czech Republic
| | - Pietari Makela
- Department of Radiology, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Mikael Anttinen
- Department of Urology, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Jani Saunavaara
- Department of Medical Physics, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Teija Sainio
- Department of Medical Physics, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Aida Kiviniemi
- Department of Radiology, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| | - Roberto Blanco
- Department of Radiology, Turku University Hospital, Kiinamyllynkatu 4-8, 20521, Turku, Finland
| |
Collapse
|
9
|
MacDonell J, Patel N, Rubino S, Ghoshal G, Fischer G, Burdette EC, Hwang R, Pilitsis JG. Magnetic resonance-guided interstitial high-intensity focused ultrasound for brain tumor ablation. Neurosurg Focus 2018; 44:E11. [PMID: 29385926 PMCID: PMC5907801 DOI: 10.3171/2017.11.focus17613] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Currently, treatment of brain tumors is limited to resection, chemotherapy, and radiotherapy. Thermal ablation has been recently explored. High-intensity focused ultrasound (HIFU) is being explored as an alternative. Specifically, the authors propose delivering HIFU internally to the tumor with an MRI-guided robotic assistant (MRgRA). The advantage of the authors' interstitial device over external MRI-guided HIFU (MRgHIFU) is that it allows for conformal, precise ablation and concurrent tissue sampling. The authors describe their workflow for MRgRA HIFU delivery.
Collapse
Affiliation(s)
- Jacquelyn MacDonell
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, New York
- Department of Neurosurgery, Albany Medical Center, Albany, New York
| | - Niravkumar Patel
- Robotics Engineering Program, Worcester Polytechnic Institute, Worcester, Massachusetts
| | - Sebastian Rubino
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, New York
- Department of Neurosurgery, Albany Medical Center, Albany, New York
| | | | - Gregory Fischer
- Robotics Engineering Program, Worcester Polytechnic Institute, Worcester, Massachusetts
| | | | - Roy Hwang
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, New York
| | - Julie G. Pilitsis
- Department of Neuroscience and Experimental Therapeutics, Albany Medical Center, Albany, New York
- Department of Neurosurgery, Albany Medical Center, Albany, New York
| |
Collapse
|
10
|
Adams MS, Salgaonkar VA, Scott SJ, Sommer G, Diederich CJ. Integration of deployable fluid lenses and reflectors with endoluminal therapeutic ultrasound applicators: Preliminary investigations of enhanced penetration depth and focal gain. Med Phys 2017; 44:5339-5356. [PMID: 28681404 DOI: 10.1002/mp.12458] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Revised: 06/19/2017] [Accepted: 07/02/2017] [Indexed: 02/06/2023] Open
Abstract
PURPOSE Catheter-based ultrasound applicators can generate thermal ablation of tissues adjacent to body lumens, but have limited focusing and penetration capabilities due to the small profile of integrated transducers required for the applicator to traverse anatomical passages. This study investigates a design for an endoluminal or laparoscopic ultrasound applicator with deployable acoustic reflector and fluid lens components, which can be expanded after device delivery to increase the effective acoustic aperture and allow for deeper and dynamically adjustable target depths. Acoustic and biothermal theoretical studies, along with benchtop proof-of-concept measurements, were performed to investigate the proposed design. METHODS The design schema consists of an array of tubular transducer(s) situated at the end of a catheter assembly, surrounded by an expandable water-filled conical balloon with a secondary reflective compartment that redirects acoustic energy distally through a plano-convex fluid lens. By controlling the lens fluid volume, the convex surface can be altered to adjust the focal length or collapsed for device insertion or removal. Acoustic output of the expanded applicator assembly was modeled using the rectangular radiator method and secondary sources, accounting for reflection and refraction at interfaces. Parametric studies of transducer radius (1-5 mm), height (3-25 mm), frequency (1.5-3 MHz), expanded balloon diameter (10-50 mm), lens focal length (10-100 mm), lens fluid (silicone oil, perfluorocarbon), and tissue attenuation (0-10 Np/m/MHz) on beam distributions and focal gain were performed. A proof-of-concept applicator assembly was fabricated and characterized using hydrophone-based intensity profile measurements. Biothermal simulations of endoluminal ablation in liver and pancreatic tissue were performed for target depths between 2 and 10 cm. RESULTS Simulations indicate that focal gain and penetration depth scale with the expanded reflector-lens balloon diameter, with greater achievable performance using perfluorocarbon lens fluid. Simulations of a 50 mm balloon OD, 10 mm transducer outer diameter (OD), 1.5 MHz assembly in water resulted in maximum intensity gain of ~170 (focal dimensions: ~12 mm length × 1.4 mm width) at ~5 cm focal depth and focal gains above 100 between 24 and 84 mm depths. A smaller (10 mm balloon OD, 4 mm transducer OD, 1.5 MHz) configuration produced a maximum gain of 6 at 9 mm depth. Compared to a conventional applicator with a fixed spherically focused transducer of 12 mm diameter, focal gain was enhanced at depths beyond 20 mm for assembly configurations with balloon diameters ≥ 20 mm. Hydrophone characterizations of the experimental assembly (31 mm reflector/lens diameter, 4.75 mm transducer radius, 1.7 MHz) illustrated focusing at variable depths between 10-70 mm with a maximum gain of ~60 and demonstrated agreement with theoretical simulations. Biothermal simulations (30 s sonication, 75 °C maximum) indicate that investigated applicator assembly configurations, at 30 mm and 50 mm balloon diameters, could create localized ellipsoidal thermal lesions increasing in size from 10 to 55 mm length × 3-6 mm width in liver tissue as target depth increased from 2 to 10 cm. CONCLUSIONS Preliminary theoretical and experimental analysis demonstrates that combining endoluminal ultrasound with an expandable acoustic reflector and fluid lens assembly can significantly enhance acoustic focal gain and penetration from inherently smaller diameter catheter-based applicators.
Collapse
Affiliation(s)
- Matthew S Adams
- Thermal Therapy Research Group, University of California San Francisco, 2340 Sutter Street, S341, San Francisco, CA, 94115, USA.,University of California, Berkeley - University of California, San Francisco Graduate Program in Bioengineering, University of California, CA, USA
| | - Vasant A Salgaonkar
- Thermal Therapy Research Group, University of California San Francisco, 2340 Sutter Street, S341, San Francisco, CA, 94115, USA
| | - Serena J Scott
- Thermal Therapy Research Group, University of California San Francisco, 2340 Sutter Street, S341, San Francisco, CA, 94115, USA
| | - Graham Sommer
- Department of Radiology, Stanford University, Stanford, CA, 94305, USA
| | - Chris J Diederich
- Thermal Therapy Research Group, University of California San Francisco, 2340 Sutter Street, S341, San Francisco, CA, 94115, USA.,University of California, Berkeley - University of California, San Francisco Graduate Program in Bioengineering, University of California, CA, USA
| |
Collapse
|
11
|
N'Djin WA, Gerold B, Vion-Bailly J, Canney MS, Nguyen-Dinh A, Carpentier A, Chapelon JY. Capacitive Micromachined Ultrasound Transducers for Interstitial High-Intensity Ultrasound Therapies. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2017; 64:1245-1260. [PMID: 28541897 DOI: 10.1109/tuffc.2017.2707663] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Capacitive micromachined ultrasound transducers (CMUTs) exhibit several potential advantages over conventional piezo technologies for use in therapeutic ultrasound (US) devices, including ease of miniaturization and integration with electronics, broad bandwidth (>several megahertz), and compatibility with magnetic resonance imaging (MRI). In this paper, the electroacoustic performance of CMUTs designed for interstitial high-intensity contact US (HICU) applications was evaluated and the feasibility of generating US-induced heating and thermal destruction of biological tissues was studied. One-dimensional CMUT linear arrays as well as a prism-shaped 2-D array composed of multiple 1-D linear arrays mounted on a cylindrical catheter were fabricated. The electromechanical and acoustic characteristics of the CMUTs were first studied at low intensity. Then, the acoustic output during continuous wave (CW) driving was studied while varying the bias voltage ( VDC ) and driving voltage ( VAC ). US heating was performed in tissue-mimicking gel phantoms under infrared (IR) or MR-thermometry monitoring. Acoustic intensities compatible with thermal ablation were obtained by driving the CMUTs in the collapse-snapback operation mode ( [Formula: see text]). Hysteresis in the acoustic output was observed with varying VDC . IR- and MR-thermometry monitoring showed directional US-induced heating patterns in tissue-mimicking phantoms (frequency: 6-8 MHz and exposure time: 60-240 s) extending over 1.5-cm depth from the CMUT surface. Irreversible thermal damage was produced in turkey breast tissue samples ( [Formula: see text]). Multidirectional US-induced heating was also achieved in 3-D with the CMUT catheter. These studies demonstrate that CMUTs can be integrated into HICU devices and be used for heating and destruction of tissue under MR guidance.
Collapse
|
12
|
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.
Collapse
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.
| |
Collapse
|
13
|
Su H, Li G, Rucker DC, Webster Iii RJ, Fischer GS. A Concentric Tube Continuum Robot with Piezoelectric Actuation for MRI-Guided Closed-Loop Targeting. Ann Biomed Eng 2016; 44:2863-2873. [PMID: 26983842 PMCID: PMC5479710 DOI: 10.1007/s10439-016-1585-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Accepted: 03/01/2016] [Indexed: 11/30/2022]
Abstract
This paper presents the design, modeling and experimental evaluation of a magnetic resonance imaging (MRI)-compatible concentric tube continuum robotic system. This system enables MRI-guided deployment of a precurved and steerable concentric tube continuum mechanism, and is suitable for clinical applications where a curved trajectory is needed. This compact 6 degree-of-freedom (DOF) robotic system is piezoelectrically-actuated, and allows simultaneous robot motion and imaging with no visually observable image artifact. The targeting accuracy is evaluated with optical tracking system and gelatin phantom under live MRI-guidance with Root Mean Square (RMS) errors of 1.94 and 2.17 mm respectively. Furthermore, we demonstrate that the robot has kinematic redundancy to reach the same target through different paths. This was evaluated in both free space and MRI-guided gelatin phantom trails, with RMS errors of 0.48 and 0.59 mm respectively. As the first of its kind, MRI-guided targeted concentric tube needle placements with ex vivo porcine liver are demonstrated with 4.64 mm RMS error through closed-loop control of the piezoelectrically-actuated robot.
Collapse
Affiliation(s)
- Hao Su
- Wyss Institute for Biologically Inspired Engineering and the John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA.
| | - Gang Li
- Automation and Interventional Medicine (AIM) Robotics Laboratory, Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA, 01609, USA
| | - D Caleb Rucker
- Vanderbilt Institute in Surgery and Engineering, Vanderbilt University, Nashville, TN, 37235, USA
| | | | - Gregory S Fischer
- Automation and Interventional Medicine (AIM) Robotics Laboratory, Department of Mechanical Engineering, Worcester Polytechnic Institute, Worcester, MA, 01609, USA
| |
Collapse
|
14
|
Ramsay E, Mougenot C, Staruch R, Boyes A, Kazem M, Bronskill M, Foster H, Sugar L, Haider M, Klotz L, Chopra R. Evaluation of Focal Ablation of Magnetic Resonance Imaging Defined Prostate Cancer Using Magnetic Resonance Imaging Controlled Transurethral Ultrasound Therapy with Prostatectomy as the Reference Standard. J Urol 2016; 197:255-261. [PMID: 27545572 DOI: 10.1016/j.juro.2016.06.100] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2016] [Indexed: 01/02/2023]
Abstract
PURPOSE We evaluated magnetic resonance imaging controlled transurethral ultrasound therapy as a treatment for magnetic resonance imaging defined focal prostate cancer using subsequent prostatectomy and histology as the reference standard. MATERIALS AND METHODS Five men completed this pilot study, which was approved by the institutional review board. Prior to radical prostatectomy focal tumors identified by magnetic resonance imaging were treated by coagulating targeted subtotal 3-dimensional volumes of prostate tissue using magnetic resonance imaging controlled transurethral focused ultrasound. Treatment was performed with a 3 Tesla clinical magnetic resonance imaging unit combined with modified clinical planning software for high intensity focused ultrasound therapy. After prostatectomy whole mount histological sections parallel to the magnetic resonance imaging treatment planes were used to compare magnetic resonance imaging measurements with thermal damage at the cellular level and, thus, evaluate treatment and target accuracy. RESULTS Three-dimensional target volumes of 4 to 20 cc and with radii up to 35 mm from the urethra were treated successfully. Mean ± SD temperature control accuracy at the target boundary was -1.6 ± 4.8C and the mean spatial targeting accuracy achieved was -1.5 ± 2.8 mm. Mean treatment accuracy with respect to histology was -0.4 ± 1.7 mm with all index tumors falling inside the histological outer limit of thermal injury. CONCLUSIONS Magnetic resonance imaging guided transurethral ultrasound therapy is capable of generating thermal coagulation and tumor destruction in targeted 3-dimensional angular sectors out to the prostate capsule for prostate glands up to 70 cc in volume. Ultrasound parameters needed to achieve ablation at the prostate capsule were determined, providing a foundation for future studies.
Collapse
Affiliation(s)
- Elizabeth Ramsay
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | | | - Robert Staruch
- Philips Research North America, Cambridge, Massachusetts
| | - Aaron Boyes
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Mohammad Kazem
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Michael Bronskill
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Harry Foster
- Department of Anaesthesiology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto
| | - Linda Sugar
- Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Masoom Haider
- Department of Medical Imaging, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Laurence Klotz
- Department of Urology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada
| | - Rajiv Chopra
- Department of Radiology and Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.
| |
Collapse
|
15
|
Sun XR, Patel NV, Danish SF. Tissue Ablation Dynamics During Magnetic Resonance-Guided, Laser-Induced Thermal Therapy. Neurosurgery 2016; 77:51-8; discussion 58. [PMID: 26086908 DOI: 10.1227/neu.0000000000000732] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Magnetic resonance-guided, laser-induced thermal therapy is a real-time magnetic resonance thermometry-guided, minimally invasive procedure used in the treatment of intracranial tumors, epilepsy, and pain. Little is known about its dynamics and the effects of various pathologies on overall ablation. OBJECTIVE To determine the relationship between thermal energy delivery and the time to maximal estimated thermal damage and whether differences exist between various intracranial pathologies. METHODS We used real-time ablation data from 28 patients across 5 unique intracranial pathologies. All ablations were performed using the Visualase Thermal Therapy System (Medtronic, Inc, Minneapolis, Minnesota), which uses a 980-nm diffusing tip diode laser. The thermal damage area was plotted against time for each ablation. We then estimated the duration of time required to reach 50% (t50) and 97% (t97) of maximal damage. Comparisons were then made between different intracranial pathologies. RESULTS The duration required to reach maximal thermal damage estimate (TDE) among all ablations was 159 ± 62 seconds, and the t50 and t97 were 43 ± 21 and 136 ± 57 seconds, respectively, where t97 was reached at an average of 23 seconds before the maximal TDE. The t97 was shorter in the recurrent metastasis/radiation necrosis and epilepsy groups compared with the previously untreated glioblastoma multiforme group. CONCLUSION The optimal duration can be estimated by the t97, which can be achieved in less than 3 minutes and differs across ablation targets. TDE expansion decelerates with prolonged ablation. Future studies are needed to examine the radiographic and clinical outcomes as well as the effects of ablation power, irrigation speed, and the effect of previous therapies on ablation dynamics.
Collapse
Affiliation(s)
- Xiaonan R Sun
- *Division of Neurosurgery, Rutgers University, Robert Wood Johnson Medical School, New Brunswick, New Jersey; ‡Department of Neurological Surgery, Rutgers University, New Jersey Medical School, Newark, New Jersey
| | | | | |
Collapse
|
16
|
McWilliams BT, Schnell EE, Curto S, Fahrbach TM, Prakash P. A Directional Interstitial Antenna for Microwave Tissue Ablation: Theoretical and Experimental Investigation. IEEE Trans Biomed Eng 2015; 62:2144-50. [DOI: 10.1109/tbme.2015.2413672] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
17
|
Odéen H, Todd N, Diakite M, Minalga E, Payne A, Parker DL. Sampling strategies for subsampled segmented EPI PRF thermometry in MR guided high intensity focused ultrasound. Med Phys 2015; 41:092301. [PMID: 25186406 DOI: 10.1118/1.4892171] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To investigate k-space subsampling strategies to achieve fast, large field-of-view (FOV) temperature monitoring using segmented echo planar imaging (EPI) proton resonance frequency shift thermometry for MR guided high intensity focused ultrasound (MRgHIFU) applications. METHODS Five different k-space sampling approaches were investigated, varying sample spacing (equally vs nonequally spaced within the echo train), sampling density (variable sampling density in zero, one, and two dimensions), and utilizing sequential or centric sampling. Three of the schemes utilized sequential sampling with the sampling density varied in zero, one, and two dimensions, to investigate sampling the k-space center more frequently. Two of the schemes utilized centric sampling to acquire the k-space center with a longer echo time for improved phase measurements, and vary the sampling density in zero and two dimensions, respectively. Phantom experiments and a theoretical point spread function analysis were performed to investigate their performance. Variable density sampling in zero and two dimensions was also implemented in a non-EPI GRE pulse sequence for comparison. All subsampled data were reconstructed with a previously described temporally constrained reconstruction (TCR) algorithm. RESULTS The accuracy of each sampling strategy in measuring the temperature rise in the HIFU focal spot was measured in terms of the root-mean-square-error (RMSE) compared to fully sampled "truth." For the schemes utilizing sequential sampling, the accuracy was found to improve with the dimensionality of the variable density sampling, giving values of 0.65 °C, 0.49 °C, and 0.35 °C for density variation in zero, one, and two dimensions, respectively. The schemes utilizing centric sampling were found to underestimate the temperature rise, with RMSE values of 1.05 °C and 1.31 °C, for variable density sampling in zero and two dimensions, respectively. Similar subsampling schemes with variable density sampling implemented in zero and two dimensions in a non-EPI GRE pulse sequence both resulted in accurate temperature measurements (RMSE of 0.70 °C and 0.63 °C, respectively). With sequential sampling in the described EPI implementation, temperature monitoring over a 192×144×135 mm3 FOV with a temporal resolution of 3.6 s was achieved, while keeping the RMSE compared to fully sampled "truth" below 0.35 °C. CONCLUSIONS When segmented EPI readouts are used in conjunction with k-space subsampling for MR thermometry applications, sampling schemes with sequential sampling, with or without variable density sampling, obtain accurate phase and temperature measurements when using a TCR reconstruction algorithm. Improved temperature measurement accuracy can be achieved with variable density sampling. Centric sampling leads to phase bias, resulting in temperature underestimations.
Collapse
Affiliation(s)
- Henrik Odéen
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84108 and Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Nick Todd
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Mahamadou Diakite
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84108 and Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Emilee Minalga
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Allison Payne
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Dennis L Parker
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| |
Collapse
|
18
|
Burtnyk M, Hill T, Cadieux-Pitre H, Welch I. Magnetic Resonance Image Guided Transurethral Ultrasound Prostate Ablation: A Preclinical Safety and Feasibility Study with 28-Day Followup. J Urol 2015; 193:1669-75. [DOI: 10.1016/j.juro.2014.11.089] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2014] [Indexed: 11/26/2022]
Affiliation(s)
- Mathieu Burtnyk
- Profound Medical, Inc., Toronto, Ontario, Canada
- Animal Care and Veterinary Services, Western University (TH, HC-P, IW), London, Ontario, Canada
| | - Tracy Hill
- Profound Medical, Inc., Toronto, Ontario, Canada
- Animal Care and Veterinary Services, Western University (TH, HC-P, IW), London, Ontario, Canada
| | - Heather Cadieux-Pitre
- Profound Medical, Inc., Toronto, Ontario, Canada
- Animal Care and Veterinary Services, Western University (TH, HC-P, IW), London, Ontario, Canada
| | - Ian Welch
- Profound Medical, Inc., Toronto, Ontario, Canada
- Animal Care and Veterinary Services, Western University (TH, HC-P, IW), London, Ontario, Canada
| |
Collapse
|
19
|
Salgaonkar VA, Diederich CJ. Catheter-based ultrasound technology for image-guided thermal therapy: current technology and applications. Int J Hyperthermia 2015; 31:203-15. [PMID: 25799287 DOI: 10.3109/02656736.2015.1006269] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Catheter-based ultrasound (CBUS) is applied to deliver minimally invasive thermal therapy to solid cancer tumours, benign tissue growth, vascular disease, and tissue remodelling. Compared to other energy modalities used in catheter-based surgical interventions, unique features of ultrasound result in conformable and precise energy delivery with high selectivity, fast treatment times, and larger treatment volumes. We present a concise review of CBUS technology being currently utilized in animal and clinical studies or being developed for future applications. CBUS devices have been categorised into interstitial, endoluminal and endovascular/cardiac applications. Basic applicator designs, site-specific evaluations and possible treatment applications have been discussed in brief. Particular emphasis has been given to ablation studies that incorporate image guidance for applicator placement, therapy monitoring, feedback control, and post-procedure assessment. Examples of devices included here span the entire spectrum of the development cycle from preliminary simulation-based design studies to implementation in clinical investigations. The use of CBUS under image guidance has the potential for significantly improving precision and applicability of thermal therapy delivery.
Collapse
Affiliation(s)
- Vasant A Salgaonkar
- Department of Radiation Oncology, University of California , San Francisco, California , USA
| | | |
Collapse
|
20
|
N’Djin WA, Burtnyk M, Lipsman N, Bronskill M, Kucharczyk W, Schwartz ML, Chopra R. Active MR-temperature feedback control of dynamic interstitial ultrasound therapy in brain:In vivoexperiments and modeling in native and coagulated tissues. Med Phys 2014; 41:093301. [DOI: 10.1118/1.4892923] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
|
21
|
Yiallouras C, Damianou C. Review of MRI positioning devices for guiding focused ultrasound systems. Int J Med Robot 2014; 11:247-55. [PMID: 25045075 DOI: 10.1002/rcs.1601] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 06/03/2014] [Accepted: 06/04/2014] [Indexed: 11/10/2022]
Abstract
BACKGROUND This article contains a review of positioning devices that are currently used in the area of magnetic resonance imaging (MRI) guided focused ultrasound surgery (MRgFUS). METHODS The paper includes an extensive review of literature published since the first prototype system was invented in 1991. RESULTS The technology has grown into a fast developing area with application to any organ accessible to ultrasound. The initial design operated using hydraulic principles, while the latest technology incorporates piezoelectric motors. Although, in the beginning there were fears regarding MRI safety, during recent years, the deployment of MR-safe positioning devices in FUS has become routine. Many of these positioning devices are now undergoing testing in clinical trials. CONCLUSION Existing MRgFUS systems have been utilized mostly in oncology (fibroids, brain, liver, kidney, bone, pancreas, eye, thyroid, and prostate). It is anticipated that, in the near future, there will be a positioning device for every organ that is accessible by focused ultrasound.
Collapse
Affiliation(s)
- C Yiallouras
- Department of Bioengineering, City University, London, UK.,R&D, MEDSONIC LTD, Limassol, Cyprus
| | - C Damianou
- Electrical Engineering Department, Cyprus University of Technology, Cyprus.,R&D, MEDSONIC LTD, Limassol, Cyprus
| |
Collapse
|
22
|
Schlesinger D, Benedict S, Diederich C, Gedroyc W, Klibanov A, Larner J. MR-guided focused ultrasound surgery, present and future. Med Phys 2014; 40:080901. [PMID: 23927296 DOI: 10.1118/1.4811136] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
MR-guided focused ultrasound surgery (MRgFUS) is a quickly developing technology with potential applications across a spectrum of indications traditionally within the domain of radiation oncology. Especially for applications where focal treatment is the preferred technique (for example, radiosurgery), MRgFUS has the potential to be a disruptive technology that could shift traditional patterns of care. While currently cleared in the United States for the noninvasive treatment of uterine fibroids and bone metastases, a wide range of clinical trials are currently underway, and the number of publications describing advances in MRgFUS is increasing. However, for MRgFUS to make the transition from a research curiosity to a clinical standard of care, a variety of challenges, technical, financial, clinical, and practical, must be overcome. This installment of the Vision 20∕20 series examines the current status of MRgFUS, focusing on the hurdles the technology faces before it can cross over from a research technique to a standard fixture in the clinic. It then reviews current and near-term technical developments which may overcome these hurdles and allow MRgFUS to break through into clinical practice.
Collapse
Affiliation(s)
- David Schlesinger
- Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908, USA.
| | | | | | | | | | | |
Collapse
|
23
|
Zucconi F, Colombo PE, Pasetto S, Lascialfari A, Ticca C, Torresin A. Analysis and reduction of thermal dose errors in MRgFUS treatment. Phys Med 2014; 30:111-6. [DOI: 10.1016/j.ejmp.2013.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Revised: 02/27/2013] [Accepted: 04/25/2013] [Indexed: 11/27/2022] Open
|
24
|
Applicators for magnetic resonance-guided ultrasonic ablation of benign prostatic hyperplasia. Invest Radiol 2014; 48:387-94. [PMID: 23462673 DOI: 10.1097/rli.0b013e31827fe91e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
OBJECTIVES The aims of this study were to evaluate in a canine model applicators designed for ablation of human benign prostatic hyperplasia (BPH) in vivo under magnetic resonance imaging (MRI) guidance, including magnetic resonance thermal imaging (MRTI), determine the ability of MRI techniques to visualize ablative changes in prostate, and evaluate the acute and longer term histologic appearances of prostate tissue ablated during these studies. MATERIALS AND METHODS An MRI-compatible transurethral device incorporating a tubular transducer array with dual 120° sectors was used to ablate canine prostate tissue in vivo, in zones similar to regions of human BPH (enlarged transition zones). Magnetic resonance thermal imaging was used for monitoring of ablation in a 3-T environment, and postablation MRIs were performed to determine the visibility of ablated regions. Three canine prostates were ablated in acute studies, and 2 animals were rescanned before killing at 31 days postablation. Acute and chronic appearances of ablated prostate tissue were evaluated histologically and were correlated with the MRTI and postablation MRI scans. RESULTS It was possible to ablate regions similar in size to enlarged transition zone in human BPH in 6 to 18 minutes. Regions of acute ablation showed a central "heat-fixed" region surrounded by a region of more obvious necrosis with complete disruption of tissue architecture. After 31 days, ablated regions demonstrated complete apparent resorption of ablated tissue with formation of cystic regions containing fluid. The inherent cooling of the urethra using the technique resulted in complete urethral preservation in all cases. CONCLUSIONS Prostatic ablation of zones of size and shape corresponding to human BPH is possible using appropriate transurethral applicators using MRTI, and ablated tissue may be depicted clearly in contrast-enhanced magnetic resonance images. The ability accurately to monitor prostate tissue heating, the apparent resorption of ablated regions over 1 month, and the inherent urethral preservation suggest that the magnetic resonance-guided techniques described are highly promising for the in vivo ablation of symptomatic human BPH.
Collapse
|
25
|
Yiallouras C, Mylonas N, Damianou C. MRI-compatible positioning device for guiding a focused ultrasound system for transrectal treatment of prostate cancer. Int J Comput Assist Radiol Surg 2013; 9:745-53. [DOI: 10.1007/s11548-013-0964-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 11/12/2013] [Indexed: 10/25/2022]
|
26
|
Partanen A, Yerram NK, Trivedi H, Dreher MR, Oila J, Hoang AN, Volkin D, Nix J, Turkbey B, Bernardo M, Haines DC, Benjamin CJ, Linehan WM, Choyke P, Wood BJ, Ehnholm GJ, Venkatesan AM, Pinto PA. Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy of the prostate: a preclinical study with radiological and pathological correlation using customised MRI-based moulds. BJU Int 2013; 112:508-16. [PMID: 23746198 DOI: 10.1111/bju.12126] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE To characterise the feasibility and safety of a novel transurethral ultrasound (US)-therapy device combined with real-time multi-plane magnetic resonance imaging (MRI)-based temperature monitoring and temperature feedback control, to enable spatiotemporally precise regional ablation of simulated prostate gland lesions in a preclinical canine model. To correlate ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology. MATERIALS AND METHODS Three dogs were treated with three targeted ablations each, using a prototype MRI-guided transurethral US-therapy system (Philips Healthcare, Vantaa, Finland). MRI provided images for treatment planning, guidance, real-time multi-planar thermometry, as well as post-treatment evaluation of efficacy. After treatment, specimens underwent histopathological analysis to determine the extent of necrosis and cell viability. Statistical analyses (Pearson's correlation, Student's t-test) were used to evaluate the correlation between ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology. RESULTS MRI combined with a transurethral US-therapy device enabled multi-planar temperature monitoring at the target as well as in surrounding tissues, allowing for safe, targeted, and controlled ablations of prescribed lesions. Ablated volumes measured by cumulative thermal dose positively correlated with volumes determined by histopathological analysis (r(2) 0.83, P < 0.001). Post-procedural contrast-enhanced and diffusion-weighted MRI showed a positive correlation with non-viable areas on histopathological analysis (r(2) 0.89, P < 0.001, and r(2) 0.91, P = 0.003, respectively). Additionally, there was a positive correlation between ablated volumes according to cumulative thermal dose and volumes identified on post-procedural contrast-enhanced MRI (r(2) 0.77, P < 0.01). There was no difference in mean ablation volumes assessed with the various analysis methods (P > 0.05, Student's t-test). CONCLUSIONS MRI-guided transurethral US therapy enabled safe and targeted ablations of prescribed lesions in a preclinical canine prostate model. Ablation volumes were reliably predicted by intra- and post-procedural imaging. Clinical studies are needed to confirm the feasibility, safety, oncological control, and functional outcomes of this therapy in patients in whom focal therapy is indicated.
Collapse
Affiliation(s)
- Ari Partanen
- Philips Healthcare, Cleveland, OH; Department of Physics, University of Helsinki, Helsinki, Finland
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Imani F, Abolmaesumi P, Wu MZ, Lasso A, Burdette EC, Ghoshal G, Heffter T, Williams E, Neubauer P, Fichtinger G, Mousavi P. Ultrasound-guided characterization of interstitial ablated tissue using RF time series: feasibility study. IEEE Trans Biomed Eng 2013; 60:1608-18. [PMID: 23335657 DOI: 10.1109/tbme.2013.2240300] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This paper presents the results of a feasibility study to demonstrate the application of ultrasound RF time series imaging to accurately differentiate ablated and nonablated tissue. For 12 ex vivo and two in situ tissue samples, RF ultrasound signals are acquired prior to, and following, high-intensity ultrasound ablation. Spatial and temporal features of these signals are used to characterize ablated and nonablated tissue in a supervised-learning framework. In cross-validation evaluation, a subset of four features extracted from RF time series produce a classification accuracy of 84.5%, an area under ROC curve of 0.91 for ex vivo data, and an accuracy of 85% for in situ data. Ultrasound RF time series is a promising approach for characterizing ablated tissue.
Collapse
Affiliation(s)
- Farhad Imani
- Department of Electrical and Computer Engineering, Queen’s university, Kingston, ON K7L 3N6, Canada.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Chopra R, Colquhoun A, Burtnyk M, N'djin WA, Kobelevskiy I, Boyes A, Siddiqui K, Foster H, Sugar L, Haider MA, Bronskill M, Klotz L. MR imaging-controlled transurethral ultrasound therapy for conformal treatment of prostate tissue: initial feasibility in humans. Radiology 2012; 265:303-13. [PMID: 22929332 DOI: 10.1148/radiol.12112263] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
PURPOSE To evaluate the feasibility and safety of magnetic resonance (MR) imaging-controlled transurethral ultrasound therapy for prostate cancer in humans. MATERIALS AND METHODS This pilot study was approved by the institutional review board and was performed in eight men (mean age, 60 years; range, 49-70 years) with localized prostate cancer (Gleason score≤7, prostate-specific antigen level #15 μg/L) immediately before radical prostatectomy. All patients provided written informed consent. This phase 0 feasibility and safety study is the first evaluation in humans. Transurethral ultrasound therapy was performed with the patient under spinal anesthesia by using a clinical 1.5-T MR unit. Patients then underwent radical prostatectomy, and the resected gland was sliced in the plane of treatment to compare the MR imaging measurements with the pattern of thermal damage. The overall procedure time and coagulation rate were measured. In addition, the spatial targeting accuracy was evaluated, as was the thermal history along the thermal damage boundaries in the gland. RESULTS The average procedure time was 3 hours, with 2 or fewer hours spent in the MR unit. The treatment was well tolerated by all patients, and a temperature uncertainty of less than 2°C was observed in the treatments. The mean temperature and thermal dose measured along the boundary of thermal coagulation were 52.3°C±2.1 and 3457 (cumulative equivalent minutes at 43°C)±5580, respectively. The mean treatment rate was 0.5 mL/min, and a spatial targeting accuracy of -1.0 mm±2.6 was achieved. CONCLUSION MR imaging-controlled transurethral ultrasound therapy is feasible, safe, and well tolerated. This technology could be an attractive approach for whole-gland or focal therapy.
Collapse
Affiliation(s)
- Rajiv Chopra
- Imaging Research, Sunnybrook Research Institute, 2075 Bayview Ave, Room C713, Toronto, ON, Canada M4N 3M5.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Petrusca L, Ngo J, Brasset L, Blanc E, Murillo A, Auboiroux V, Cotton F, Chapelon JY, Salomir R. Experimental investigation of MRgHIFU sonication with interleaved electronic and mechanical displacement of the focal point for transrectal prostate application. Phys Med Biol 2012; 57:4805-25. [DOI: 10.1088/0031-9155/57/15/4805] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
|
30
|
N'djin WA, Burtnyk M, Bronskill M, Chopra R. Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer. Int J Hyperthermia 2012; 28:87-104. [PMID: 22235788 DOI: 10.3109/02656736.2011.622343] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Transurethral ultrasound therapy uses real-time magnetic resonance (MR) temperature feedback to enable the 3D control of thermal therapy accurately in a region within the prostate. Previous canine studies showed the feasibility of this method in vivo. The aim of this study was to reduce the procedure time, while maintaining targeting accuracy, by investigating new combinations of treatment parameters. Simulations and validation experiments in gel phantoms were used, with a collection of nine 3D realistic target prostate boundaries obtained from previous preclinical studies, where multi-slice MR images were acquired with the transurethral device in place. Acoustic power and rotation rate were varied based on temperature feedback at the prostate boundary. Maximum acoustic power and rotation rate were optimised interdependently, as a function of prostate radius and transducer operating frequency. The concept of dual frequency transducers was studied, using the fundamental frequency or the third harmonic component depending on the prostate radius. Numerical modelling enabled assessment of the effects of several acoustic parameters on treatment outcomes. The range of treatable prostate radii extended with increasing power, and tended to narrow with decreasing frequency. Reducing the frequency from 8 MHz to 4 MHz or increasing the surface acoustic power from 10 to 20 W/cm(2) led to treatment times shorter by up to 50% under appropriate conditions. A dual frequency configuration of 4/12 MHz with 20 W/cm(2) ultrasound intensity exposure can treat entire prostates up to 40 cm(3) in volume within 30 min. The interdependence between power and frequency may, however, require integrating multi-parametric functions in the controller for future optimisations.
Collapse
Affiliation(s)
- William Apoutou N'djin
- Imaging Research, Sunnybrook Health Sciences Centre, and Department of Medical Biophysics, University of Toronto, Ontario, Canada.
| | | | | | | |
Collapse
|
31
|
Todd N, Diakite M, Payne A, Parker DL. Hybrid proton resonance frequency/T1 technique for simultaneous temperature monitoring in adipose and aqueous tissues. Magn Reson Med 2012; 69:62-70. [PMID: 22392856 DOI: 10.1002/mrm.24228] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 12/21/2011] [Accepted: 02/04/2012] [Indexed: 01/11/2023]
Abstract
Thermal therapy procedures being carried out under MR guidance would be safer if temperature changes could be accurately monitored in both water-based and fat-based tissues. To this end, we present a hybrid proton resonance frequency (PRF)/T(1) approach for simultaneously measuring PRF shift temperatures in water-based tissues and T(1) changes in fat-based tissues. The hybrid PRF/T(1) sequence is a standard radiofrequency spoiled gradient echo sequence executed in a dynamic mode with two flip angles alternating every time frame. The PRF information is extracted every time frame using the image phase in the standard approach, and the T(1) information is extracted every two time frames using a variable flip angle approach. Simulation studies, ex vivo high intensity focused ultrasound heating experiments, and in vivo stability experiments were performed to test the feasibility of the approach. The results indicate that the hybrid PRF/T(1) approach provides PRF temperature maps of the same quality as those obtained by traditional PRF methods while simultaneously being able to track T(1) changes in fat-based tissues. Although several potential error sources exist for the T(1) measurements, the approach is a promising start toward realizing quantitative temperature measurements in both water-based and fat-based tissues.
Collapse
Affiliation(s)
- Nick Todd
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA.
| | | | | | | |
Collapse
|
32
|
Mast TD, Barthe PG, Makin IRS, Slayton MH, Karunakaran CP, Burgess MT, Alqadah A, Rudich SM. Treatment of rabbit liver cancer in vivo using miniaturized image-ablate ultrasound arrays. ULTRASOUND IN MEDICINE & BIOLOGY 2011; 37:1609-21. [PMID: 21821349 DOI: 10.1016/j.ultrasmedbio.2011.05.850] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2010] [Revised: 05/03/2011] [Accepted: 05/10/2011] [Indexed: 05/09/2023]
Abstract
In the preclinical studies reported here, VX2 cancer within rabbit liver has been treated by bulk ultrasound ablation employing miniaturized image-ablate arrays. Array probes were constructed with 32 elements in a 2.3 × 20 mm(2) aperture, packaged within a 3.1 mm stainless steel tube with a cooling and coupling balloon for in vivo use. The probes were measured capable of 50% fractional bandwidth for pulse-echo imaging (center frequency 4.4 MHz) with >110 W/cm(2) surface intensity available at sonication frequencies 3.5 and 4.8 MHz. B-scan imaging performance of the arrays was measured to be comparable to larger diagnostic linear arrays, although nearfield image quality was reduced by ringdown artifacts. A series of in vivo ablation procedures was performed using an unfocused 32-element aperture firing at 4.8 MHz with exposure durations 20-70.5 s and in situ spatial average, temporal average intensities 22.4-38.5 W/cm(2). Ablation of a complete tumor cross-section was confirmed by vital staining in seven of 12 exposures, with four exposures ablating an additional margin >1 mm beyond the tumor in all directions. Analysis suggests a threshold ablation effect, with complete ablation of tumor cross-sections for exposures with delivery of >838 J acoustic energy. The results show feasibility for in vivo liver cancer ablation using miniaturized image-ablate arrays suitable for interstitial deployment.
Collapse
Affiliation(s)
- T Douglas Mast
- Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH 45267-0586, USA.
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Wootton JH, Prakash P, Hsu ICJ, Diederich CJ. Implant strategies for endocervical and interstitial ultrasound hyperthermia adjunct to HDR brachytherapy for the treatment of cervical cancer. Phys Med Biol 2011; 56:3967-84. [PMID: 21666290 DOI: 10.1088/0031-9155/56/13/014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Catheter-based ultrasound devices provide a method to deliver 3D conformable heating integrated with HDR brachytherapy delivery. Theoretical characterization of heating patterns was performed to identify implant strategies for these devices which can best be used to apply hyperthermia to cervical cancer. A constrained optimization-based hyperthermia treatment planning platform was used for the analysis. The proportion of tissue ≥41 °C in a hyperthermia treatment volume was maximized with constraints T(max) ≤ 47 °C, T(rectum) ≤ 41.5 °C, and T(bladder) ≤ 42.5 °C. Hyperthermia treatment was modeled for generalized implant configurations and complex configurations from a database of patients (n = 14) treated with HDR brachytherapy. Various combinations of endocervical (360° or 2 × 180° output; 6 mm OD) and interstitial (180°, 270°, or 360° output; 2.4 mm OD) applicators within catheter locations from brachytherapy implants were modeled, with perfusion constant (1 or 3 kg m(-3) s(-1)) or varying with location or temperature. Device positioning, sectoring, active length and aiming were empirically optimized to maximize thermal coverage. Conformable heating of appreciable volumes (>200 cm(3)) is possible using multiple sectored interstitial and endocervical ultrasound devices. The endocervical device can heat >41 °C to 4.6 cm diameter compared to 3.6 cm for the interstitial. Sectored applicators afford tight control of heating that is robust to perfusion changes in most regularly spaced configurations. T(90) in example patient cases was 40.5-42.7 °C (1.9-39.6 EM(43 °C)) at 1 kg m(-3) s(-1) with 10/14 patients ≥41 °C. Guidelines are presented for positioning of implant catheters during the initial surgery, selection of ultrasound applicator configurations, and tailored power schemes for achieving T(90) ≥ 41 °C in clinically practical implant configurations. Catheter-based ultrasound devices, when adhering to the guidelines, show potential to generate conformal therapeutic heating ranging from a single endocervical device targeting small volumes local to the cervix (<2 cm radial) to a combination of a 2 × 180° endocervical and directional interstitial applicators in the lateral periphery to target much larger volumes (6 cm radial), while preferentially limiting heating of the bladder and rectum.
Collapse
Affiliation(s)
- Jeffery H Wootton
- Department of Radiation Oncology, University of California, San Francisco, CA 94115, USA
| | | | | | | |
Collapse
|
34
|
Diederich CJ. Thermal ablation and high-temperature thermal therapy: Overview of technology and clinical implementation. Int J Hyperthermia 2011; 21:745-53. [PMID: 16338857 DOI: 10.1080/02656730500271692] [Citation(s) in RCA: 177] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
High-temperature hyperthermia or thermal therapy is being applied for destruction of cancerous tissue, eradication or reduction of benign tumours and targeted tissue modification and remodelling. Many of these high-temperature technologies provide a minimally-invasive alternative with lower morbidities compared to the traditional surgical procedures. The effects of high-temperature thermal exposure on tissues, examples of heating technology and procedures of clinical practice related to high-temperature thermal therapy are reviewed. This brief review encompasses interstitial, endocavity, intraluminal and external applications of RF, microwave, ultrasound, laser and thermal conduction energy sources. The technology is prevalent and in various levels of advancement, with the move toward more spatially-accurate and controllable heating systems combined with image-guidance and treatment verification warranted, especially for the treatment of cancer.
Collapse
Affiliation(s)
- Chris J Diederich
- Thermal Therapy Research Group, Radiation Oncology Department, University of California, San Francisco, CA 94143-1708, USA.
| |
Collapse
|
35
|
Wootton JH, Hsu ICJ, Diederich CJ. Endocervical ultrasound applicator for integrated hyperthermia and HDR brachytherapy in the treatment of locally advanced cervical carcinoma. Med Phys 2011; 38:598-611. [PMID: 21452697 DOI: 10.1118/1.3512803] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
PURPOSE The clinical success of hyperthermia adjunct to radiotherapy depends on adequate temperature elevation in the tumor with minimal temperature rise in organs at risk. Existing technologies for thermal treatment of the cervix have limited spatial control or rapid energy falloff. The objective of this work is to develop an endocervical applicator using a linear array of multisectored tubular ultrasound transducers to provide 3-D conformal, locally targeted hyperthermia concomitant to radiotherapy in the uterine cervix. The catheter-based device is integrated within a HDR brachytherapy applicator to facilitate sequential and potentially simultaneous heat and radiation delivery. METHODS Treatment planning images from 35 patients who underwent HDR brachytherapy for locally advanced cervical cancer were inspected to assess the dimensions of radiation clinical target volumes (CTVs) and gross tumor volumes (GTVs) surrounding the cervix and the proximity of organs at risk. Biothermal simulation was used to identify applicator and catheter material parameters to adequately heat the cervix with minimal thermal dose accumulation in nontargeted structures. A family of ultrasound applicators was fabricated with two to three tubular transducers operating at 6.6-7.4 MHz that are unsectored (360 degrees), bisectored (2 x 180 degrees), or trisectored (3 x 120 degrees) for control of energy deposition in angle and along the device length in order to satisfy anatomical constraints. The device is housed in a 6 mm diameter PET catheter with cooling water flow for endocervical implantation. Devices were characterized by measuring acoustic efficiencies, rotational acoustic intensity distributions, and rotational temperature distributions in phantom. RESULTS The CTV in HDR brachytherapy plans extends 20.5 +/- 5.0 mm from the endocervical tandem with the rectum and bladder typically <8 mm from the target boundary. The GTV extends 19.4 +/- 7.3 mm from the tandem. Simulations indicate that for 60 min treatments the applicator can heat to 41 degrees C and deliver > 5EM(43 degrees C) over 4-5 cm diameter with Tmax < 45 degrees C and 1 kg m(-3) s(-1) blood perfusion. The 41 degrees C contour diameter is reduced to 3-4 cm at 3 kg m(-3) s(-1) perfusion. Differential power control to transducer elements and sectors demonstrates tailoring of heating along the device length and in angle. Sector cuts are associated with a 14-47 degrees acoustic dead zone, depending on cut width, resulting in a approximately 2-4 degrees C temperature reduction within the dead zone below Tmax. Dead zones can be oriented for thermal protection of the rectum and bladder. Fabricated devices have acoustic efficiencies of 33.4%-51.8% with acoustic output that is well collimated in length, reflects the sectoring strategy, and is strongly correlated with temperature distributions. CONCLUSIONS A catheter-based ultrasound applicator was developed for endocervical implantation with locally targeted, 3-D conformal thermal delivery to the uterine cervix. Feasibility of heating clinically relevant target volumes was demonstrated with power control along the device length and in angle to treat the cervix with minimal thermal dose delivery to the rectum and bladder.
Collapse
Affiliation(s)
- Jeffery H Wootton
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94115, USA
| | | | | |
Collapse
|
36
|
Ward JF. High-Intensity Focused Ultrasound for Therapeutic Tissue Ablation in Surgical Oncology. Surg Oncol Clin N Am 2011; 20:389-407, ix. [DOI: 10.1016/j.soc.2010.11.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
37
|
Sciubba DM, Burdette EC, Cheng JJ, Pennant WA, Noggle JC, Petteys RJ, Alix C, Diederich CJ, Fichtinger G, Gokaslan ZL, Murphy KP. Percutaneous computed tomography fluoroscopy–guided conformal ultrasonic ablation of vertebral tumors in a rabbit tumor model. J Neurosurg Spine 2010; 13:773-9. [DOI: 10.3171/2010.5.spine09266] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Object
Radiofrequency ablation (RFA) has proven to be effective for treatment of malignant and benign tumors in numerous anatomical sites outside the spine. The major challenge of using RFA for spinal tumors is difficulty protecting the spinal cord and nerves from damage. However, conforming ultrasound energy to match the exact anatomy of the tumor may provide successful ablation in such sensitive locations. In a rabbit model of vertebral body tumor, the authors have successfully ablated tumors using an acoustic ablator placed percutaneously via computed tomography fluoroscopic (CTF) guidance.
Methods
Using CTF guidance, 12 adult male New Zealand White rabbits were injected with VX2 carcinoma cells in the lowest lumbar vertebral body. At 21 days, a bone biopsy needle was placed into the geographical center of the lesion, down which an acoustic ablator was inserted. Three multisensor thermocouple arrays were placed around the lesion to provide measurement of tissue temperature during ablation, at thermal doses ranging from 100 to 1,000,000 TEM (thermal equivalent minutes at 43°C), and tumor volumes were given a tumoricidal dose of acoustic energy. Animals were monitored for 24 hours and then sacrificed. Pathological specimens were obtained to determine the extent of tumor death and surrounding tissue damage. Measured temperature distributions were used to reconstruct volumetric doses of energy delivered to tumor tissue, and such data were correlated with pathological findings.
Results
All rabbits were successfully implanted with VX2 cells, leading to a grossly apparent spinal and paraspinal tissue mass. The CTF guidance provided accurate placement of the acoustic ablator in all tumors, as corroborated through gross and microscopic histology. Significant tumor death was noted in all specimens without collateral damage to nearby nerve tissue. Tissue destruction just beyond the margin of the tumor was noted in some but not all specimens. No neurological deficits occurred in response to ablation. Reconstruction of measured temperature data allowed accurate assessment of volumetric dose delivered to tissues.
Conclusions
Using a rabbit intravertebral tumor model, the authors have successfully delivered tumoricidal doses of acoustic energy via a therapeutic ultrasound ablation probe placed percutaneously with CTF guidance. The authors have thus established the first technical and preclinical feasibility study of controlled ultrasound ablation of spinal tumors in vivo.
Collapse
Affiliation(s)
| | - E. Clif Burdette
- 3Systems Research Division, Acoustic MedSystems, Inc., Champaign, Illinois
| | | | | | | | | | - Christopher Alix
- 3Systems Research Division, Acoustic MedSystems, Inc., Champaign, Illinois
| | - Chris J. Diederich
- 4Department of Radiation Oncology, University of California, San Francisco, California; and
| | - Gabor Fichtinger
- 5Department of Computing, Queen's University, Kingston, Ontario, Canada
| | | | - Kieran P. Murphy
- 1Departments of Neurosurgery and
- 2Interventional Radiology, Johns Hopkins University, Baltimore, Maryland
| |
Collapse
|
38
|
Chopra R, Burtnyk M, N’djin WA, Bronskill M. MRI-controlled transurethral ultrasound therapy for localised prostate cancer. Int J Hyperthermia 2010; 26:804-21. [DOI: 10.3109/02656736.2010.503670] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
39
|
Burtnyk M, N’Djin WA, Kobelevskiy I, Bronskill M, Chopra R. 3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms. Phys Med Biol 2010; 55:6817-39. [DOI: 10.1088/0031-9155/55/22/014] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
40
|
Krafft AJ, Jenne JW, Maier F, Stafford RJ, Huber PE, Semmler W, Bock M. A long arm for ultrasound: a combined robotic focused ultrasound setup for magnetic resonance-guided focused ultrasound surgery. Med Phys 2010; 37:2380-93. [PMID: 20527572 DOI: 10.1118/1.3377777] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Focused ultrasound surgery (FUS) is a highly precise noninvasive procedure to ablate pathogenic tissue. FUS therapy is often combined with magnetic resonance (MR) imaging as MR imaging offers excellent target identification and allows for continuous monitoring of FUS induced temperature changes. As the dimensions of the ultrasound (US) focus are typically much smaller than the targeted volume, multiple sonications and focus repositioning are interleaved to scan the focus over the target volume. Focal scanning can be achieved electronically by using phased-array US transducers or mechanically by using dedicated mechanical actuators. In this study, the authors propose and evaluate the precision of a combined robotic FUS setup to overcome some of the limitations of the existing MRgFUS systems. Such systems are typically integrated into the patient table of the MR scanner and thus only provide an application of the US wave within a limited spatial range from below the patient. METHODS The fully MR-compatible robotic assistance system InnoMotion (InnoMedic GmbH, Herxheim, Germany) was originally designed for MR-guided interventions with needles. It offers five pneumatically driven degrees of freedom and can be moved over a wide range within the bore of the magnet. In this work, the robotic system was combined with a fixed-focus US transducer (frequency: 1.7 MHz; focal length: 68 mm, and numerical aperture: 0.44) that was integrated into a dedicated, in-house developed treatment unit for FUS application. A series of MR-guided focal scanning procedures was performed in a polyacrylamide-egg white gel phantom to assess the positioning accuracy of the combined FUS setup. In animal experiments with a 3-month-old domestic pig, the system's potential and suitability for MRgFUS was tested. RESULTS In phantom experiments, a total targeting precision of about 3 mm was found, which is comparable to that of the existing MRgFUS systems. Focus positioning could be performed within a few seconds. During in vivo experiments, a defined pattern of single thermal lesions and a therapeutically relevant confluent thermal lesion could be created. The creation of local tissue necrosis by coagulation was confirmed by post-FUS MR imaging and histological examinations on the treated tissue sample. During all sonications in phantom and in vivo, reliable MR imaging and online MR thermometry could be performed without compromises due to operation of the combined robotic FUS setup. CONCLUSIONS Compared to the existing MRgFUS systems, the combined robotic FUS approach offers a wide range of spatial flexibility so that highly flexible application of the US wave would be possible, for example, to avoid risk structures within the US field. The setup might help to realize new ways of patient access in MRgFUS therapy. The setup is compatible with any closed-bore MR system and does not require an especially designed patient table.
Collapse
Affiliation(s)
- Axel J Krafft
- Department of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
41
|
Burtnyk M, Chopra R, Bronskill M. Simulation study on the heating of the surrounding anatomy during transurethral ultrasound prostate therapy: A 3D theoretical analysis of patient safety. Med Phys 2010; 37:2862-75. [DOI: 10.1118/1.3426313] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
|
42
|
Fennessy FM, Tuncali K, Morrison PR, Tempany CM. MR imaging-guided interventions in the genitourinary tract: an evolving concept. Magn Reson Imaging Clin N Am 2010; 18:11-28. [PMID: 19962090 DOI: 10.1016/j.mric.2009.09.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
MR imaging-guided interventions are well established in routine patient care in many parts of the world. There are many approaches, depending on magnet design and clinical need, based on MR imaging providing excellent inherent tissue contrast without ionizing radiation risk for patients. MR imaging-guided minimally invasive therapeutic procedures have advantages over conventional surgical procedures. In the genitourinary tract, MR imaging guidance has a role in tumor detection, localization, and staging and can provide accurate image guidance for minimally invasive procedures. The advent of molecular and metabolic imaging and use of higher strength magnets likely will improve diagnostic accuracy and allow targeted therapy to maximize disease control and minimize side effects.
Collapse
Affiliation(s)
- Fiona M Fennessy
- Department of Radiology, Harvard Medical School/Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA.
| | | | | | | |
Collapse
|
43
|
Ji X, Bai JF, Shen GF, Chen YZ. High-intensity focused ultrasound with large scale spherical phased array for the ablation of deep tumors. J Zhejiang Univ Sci B 2009; 10:639-47. [PMID: 19735096 DOI: 10.1631/jzus.b0920130] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound (HIFU) is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements (diameter =1.4 cm and frequency=1 MHz) were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume (a 2 cmx2 cmx3 cm volume) at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.
Collapse
Affiliation(s)
- Xiang Ji
- Department of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | | | | | | |
Collapse
|
44
|
Petrusca L, Salomir R, Brasset L, Chavrier F, Cotton F, Chapelon JY. Sector-switching sonication strategy for accelerated HIFU treatment of prostate cancer: in vitro experimental validation. IEEE Trans Biomed Eng 2009; 57:17-23. [PMID: 19709958 DOI: 10.1109/tbme.2009.2029983] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The study investigates a new sonication strategy with high-intensity focused ultrasound (HIFU), aiming for improvement of the original Ablatherm procedure in the prostate cancer treatment. The currently implemented and clinically used method (defined as reference) uses a single-element transducer, operated with 60% duty cycle. To implement the novel strategy, the active surface was split into two sectors, which can be powered either sequentially (for temporal switching) or simultaneously (equivalent to a single-element transducer). Numerical simulations were used to predict the lesion shape and to determine for the novel strategy the best set of treatment parameters among the 99 explored cases. The same pattern for the focal point trajectory was executed irrespectively to the sector activating mode. The theoretical duty cycle reached 100% for the sector switching strategy. The HIFU device was built MRI compatible, and consisted of two mirror symmetrical sectors operating at 3 MHz, shaped as a truncated spherical cap. The two sonication strategies were experimentally tested on fresh samples of degassed porcine liver, using fast MR thermometry (proton resonance frequency shift method with voxel size 0.85 x 0.85 x 4.25 mm (3), 2 s/dynamic, 0.5 ( degrees ) C temperature accuracy, two orthogonal slices). A practical value of 87.5% overall duty cycle could be experimentally implemented. The performance of the two sonication strategies was comparatively assessed based on: cumulated thermal dose derived from MR temperature maps, postoperatory MR morphological images sensitive to tissue contrast changes (inversion-recovery T1-weighted turbo spin-echo, voxel size 0.5 x 0.5 x 4 mm (3)) and postoperatory macroscopic tissue examination. Using a sector-switching sonication strategy for prostate cancer treatment-induced lesions of similar size and shape as for the reference approach. When considering the available reserve of duty cycle and the exact lesion size, we concluded the treatment time was reduced by 20% with the new sector switching strategy at equal performance. Further in vivo studies are considered mandatory for preclinical validation.
Collapse
Affiliation(s)
- Lorena Petrusca
- National Institute for Health and Medical ResearchU556, Lyon 69424, France.
| | | | | | | | | | | |
Collapse
|
45
|
McDannold N. Quantitative MRI-based temperature mapping based on the proton resonant frequency shift: Review of validation studies. Int J Hyperthermia 2009; 21:533-46. [PMID: 16147438 DOI: 10.1080/02656730500096073] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
MRI-based temperature imaging that exploits the temperature-sensitive water proton resonant frequency shift is currently the only available method for reliable quantification of temperature changes in vivo. Extensive pre-clinical work has been performed to validate this method for guiding thermal therapies. That work has shown the method to be useful for all stages of the thermal therapy, from resolving heating below the threshold for damage to ensuring that the thermal exposure is sufficient within the target volume and protecting surrounding critical structures and to accurately predicting the extent of the ablated volume. In this paper, these validation studies will be reviewed. In addition, clinical studies that have shown this method feasible in human treatments will be overviewed.
Collapse
Affiliation(s)
- N McDannold
- Department of Radiology, Harvard Medical School and Brigham and Women's Hospital, Boston, MA 02115, USA.
| |
Collapse
|
46
|
Burtnyk M, Chopra R, Bronskill MJ. Quantitative analysis of 3-D conformal MRI-guided transurethral ultrasound therapy of the prostate: Theoretical simulations. Int J Hyperthermia 2009; 25:116-31. [DOI: 10.1080/02656730802578802] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
|
47
|
Diederich CJ, Nau WH, Kinsey A, Ross T, Wootton J, Juang T, Butts-Pauly K, Rieke V, Chen J, Bouley DM, Sommer G. Catheter-based ultrasound devices and MR thermal monitoring for conformal prostate thermal therapy. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2009; 2008:3664-8. [PMID: 19163505 DOI: 10.1109/iembs.2008.4650002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Catheter-based ultrasound applicators have been developed for delivering hyperthermia or high-temperature thermal ablation of cancer and benign disease of the prostate. These devices allow for control of heating along the length and angular expanse during therapy delivery. Four types of transurethral applicators were devised for thermal treatment of prostate combined with MR thermal monitoring: sectored tubular transducer devices with directional heating patterns and rotation; planar and curvilinear devices with narrow heating patterns and rotation; and multi-sectored tubular devices capable of dynamic angular control without applicator movement. Interstitial devices (2.4 mm OD) have been developed for percutaneous implantation with directional or dynamic angular control. In vivo experiments in canine prostate under MR temperature imaging were used to evaluate these devices and develop treatment delivery strategies. MR thermal imaging was used to monitor temperature and thermal dose in multiple slices through the target volume. Multi-sectored transurethral applicators can dynamically control the angular heating profile and target large regions of the gland in short treatment times without applicator manipulation. The sectored tubular, planar, and curvilinear transurethral devices produce directional coagulation zones, extending 15-20 mm radial distance to the outer prostate capsule. Sequential rotation under motor control and modulated dwell time can be used to tightly conform thermal ablation to selected regions. Interstitial implants with directional devices can be used to effectively ablate targeted regions of the gland while protecting the rectum. The MR derived 52 degrees C and lethal thermal dose contours (t43=240 min) effectively defined the extent of thermal damage and provided a means for real-time control of the applicators. Catheter-based ultrasound devices, combined with MR thermal monitoring, can produce relatively fast (5-40 min) and precise thermal ablation of prostate.
Collapse
Affiliation(s)
- Chris J Diederich
- Thermal Therapy Research Group, Radiation Oncology Department, University of California at San Francisco, CA 94143, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Chopra R, Tang K, Burtnyk M, Boyes A, Sugar L, Appu S, Klotz L, Bronskill M. Analysis of the spatial and temporal accuracy of heating in the prostate gland using transurethral ultrasound therapy and active MR temperature feedback. Phys Med Biol 2009; 54:2615-33. [PMID: 19351975 DOI: 10.1088/0031-9155/54/9/002] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A new MRI-guided therapy is being developed as a minimally invasive treatment for localized prostate cancer utilizing high-intensity ultrasound energy to generate a precise region of thermal coagulation within the prostate gland. The purpose of this study was to evaluate in vivo the capability to produce a spatial heating pattern in the prostate that accurately matched the shape of a target region using transurethral ultrasound heating and active MR temperature feedback. Experiments were performed in a canine model (n = 9) in a 1.5 T MR imager using a prototype device comprising a single planar transducer operated under rotational control. The spatial temperature distribution, measured every 5 s with MR thermometry, was used to adjust the acoustic power and rotation rate in order to achieve a temperature of 55 degrees C along the outer boundary of the target region. The results demonstrated the capability to produce accurate spatial heating patterns within the prostate gland. An average temperature of 56.2 +/- 0.6 degrees C was measured along the outer boundary of the target region across all experiments in this study. The average spatial error between the target boundary and the 55 degrees C isotherm was 0.8 +/- 0.7 mm (-0.2 to 3.2 mm), and the overall treatment time was < or =20 min for all experiments. Excellent spatial agreement was observed between the temperature information acquired with MRI and the pattern of thermal damage measured on H&E-stained tissue sections. This study demonstrates the benefit of adaptive energy delivery using active MR temperature feedback, and an excellent capability to treat precise regions within the prostate gland with this technology.
Collapse
Affiliation(s)
- Rajiv Chopra
- Imaging Research, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
| | | | | | | | | | | | | | | |
Collapse
|
49
|
Kinsey AM, Diederich CJ, Rieke V, Nau WH, Pauly KB, Bouley D, Sommer G. Transurethral ultrasound applicators with dynamic multi-sector control for prostate thermal therapy: in vivo evaluation under MR guidance. Med Phys 2008; 35:2081-93. [PMID: 18561684 DOI: 10.1118/1.2900131] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The purpose of this study was to explore the feasibility and performance of a multi-sectored tubular array transurethral ultrasound applicator for prostate thermal therapy, with potential to provide dynamic angular and length control of heating under MR guidance without mechanical movement of the applicator. Test configurations were fabricated, incorporating a linear array of two multi-sectored tubular transducers (7.8-8.4 MHz, 3 mm OD, 6 mm length), with three 120 degrees independent active sectors per tube. A flexible delivery catheter facilitated water cooling (100 ml min(-1)) within an expandable urethral balloon (35 mm long x 10 mm diameter). An integrated positioning hub allows for rotating and translating the transducer assembly within the urethral balloon for final targeting prior to therapy delivery. Rotational beam plots indicate approximately 90 degrees-100 degrees acoustic output patterns from each 120 degrees transducer sector, negligible coupling between sectors, and acoustic efficiencies between 41% and 53%. Experiments were performed within in vivo canine prostate (n = 3), with real-time MR temperature monitoring in either the axial or coronal planes to facilitate control of the heating profiles and provide thermal dosimetry for performance assessment. Gross inspection of serial sections of treated prostate, exposed to TTC (triphenyl tetrazolium chloride) tissue viability stain, allowed for direct assessment of the extent of thermal coagulation. These devices created large contiguous thermal lesions (defined by 52 degrees C maximum temperature, t43 = 240 min thermal dose contours, and TTC tissue sections) that extended radially from the applicator toward the border of the prostate (approximately15 mm) during a short power application (approximately 8-16 W per active sector, 8-15 min), with approximately 200 degrees or 360 degrees sector coagulation demonstrated depending upon the activation scheme. Analysis of transient temperature profiles indicated progression of lethal temperature and thermal dose contours initially centered on each sector that coalesced within approximately 5 min to produce uniform and contiguous zones of thermal destruction between sectors, with smooth outer boundaries and continued radial propagation in time. The dimension of the coagulation zone along the applicator was well-defined by positioning and active array length. Although not as precise as rotating planar and curvilinear devices currently under development for MR-guided procedures, advantages of these multi-sectored transurethral applicators include a flexible delivery catheter and that mechanical manipulation of the device using rotational motors is not required during therapy. This multi-sectored tubular array transurethral ultrasound technology has demonstrated potential for relatively fast and reasonably conformal targeting of prostate volumes suitable for the minimally invasive treatment of BPH and cancer under MR guidance, with further development warranted.
Collapse
Affiliation(s)
- Adam M Kinsey
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California, San Francisco, California 94143, USA
| | | | | | | | | | | | | |
Collapse
|
50
|
Jolesz FA, McDannold N. Current status and future potential of MRI-guided focused ultrasound surgery. J Magn Reson Imaging 2008; 27:391-9. [PMID: 18219674 DOI: 10.1002/jmri.21261] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The combination of the imaging abilities of magnetic resonance imaging (MRI) with the ability to delivery energy to targets deep in the body noninvasively with focused ultrasound presents a disruptive technology with the potential to significantly affect healthcare. MRI offers precise targeting, visualization, and quantification of temperature changes and the ability to immediately evaluate the treatment. By exploiting different mechanisms, focused ultrasound offers a range of therapies, ranging from thermal ablation to targeted drug delivery. This article reviews recent preclinical and tests clinical of this technology.
Collapse
Affiliation(s)
- Ferenc A Jolesz
- Department of Radiology, Harvard Medical School, Boston, MA 02115, USA
| | | |
Collapse
|