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Akyüz O, Tatar Z. Is it safe to use a thermocautery device for circumcision? Examination of the histopathological changes emerging after thermocautery-assisted circumcisions. Andrologia 2021; 53:e13968. [PMID: 33421180 DOI: 10.1111/and.13968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 12/08/2020] [Accepted: 12/26/2020] [Indexed: 11/28/2022] Open
Abstract
Multiple number of techniques and devices have been described concerning circumcision method so far. One of them is thermocautery device, and it has been widely used. Although there is controversy that the penis may be damaged due to the heat generated during the use of the device, not enough histopathological studies have been conducted. We aimed to determine the histopathological changes in human foreskin caused by heat after circumcision with thermocautery and to demonstrate the safety of the use of a thermocautery-assisted circumcision. Forty-one patients were divided into two groups according to the thermal energy used during cutting with thermocautery as follows: high temperature (Group 1, n = 22) and low temperature (Group 2, n = 19). The effect of the heat intensity and depth of the coagulation necrosis produced with thermocautery-assisted circumcisions performed at low and high temperatures were evaluated. The difference between the groups was not statistically significant. Tissue damage is extremely limited in thermocautery-assisted circumcisions, even when it is used at high temperatures. The thermocautery device can be used for effective and safe circumcisions.
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Affiliation(s)
- Osman Akyüz
- Medicine Hospital Department of Urology, Atlas University, Istanbul, Turkey
| | - Zeynep Tatar
- Patomer Pathological Cytological Research Center, Istanbul, Turkey
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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.
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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.
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Anthony GJ, Bader KB, Wang J, Zamora M, Ostdiek A, Antic T, Krueger S, Weiss S, Trogler WC, Blair SL, Kummel AC, Sammet S. MRI-guided transurethral insonation of silica-shell phase-shift emulsions in the prostate with an advanced navigation platform. Med Phys 2019; 46:774-788. [PMID: 30414276 PMCID: PMC6367027 DOI: 10.1002/mp.13279] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 10/24/2018] [Accepted: 10/26/2018] [Indexed: 02/05/2023] Open
Abstract
PURPOSE In this study, the efficacy of transurethral prostate ablation in the presence of silica-shell ultrasound-triggered phase-shift emulsions (sUPEs) doped with MR contrast was evaluated. The influence of sUPEs on MR imaging assessment of the ablation zone was also investigated. METHODS sUPEs were doped with a magnetic resonance (MR) contrast agent, Gd2 O3 , to assess ultrasound transition. Injections of saline (sham), saline and sUPEs alone, and saline and sUPEs with Optison microbubbles were performed under guidance of a prototype interventional MRI navigation platform in a healthy canine prostate. Treatment arms were evaluated for differences in lesion size, T1 contrast, and temperature. In addition, non-perfused areas (NPAs) on dynamic contrast-enhanced (DCE) MRI, 55°C isotherms, and areas of 240 cumulative equivalent minutes at 43°C (CEM43 ) dose or greater computed from MR thermometry were measured and correlated with ablated areas indicated by histology. RESULTS For treatment arms including sUPEs, the computed correlation coefficients between the histological ablation zone and the NPA, 55°C isotherm, and 240 CEM43 area ranged from 0.96-0.99, 0.98-0.99, and 0.91-0.99, respectively. In the absence of sUPEs, the computed correlation coefficients between the histological ablation zone and the NPA, 55°C isotherm, and 240 CEM43 area were 0.69, 0.54, and 0.50, respectively. Across all treatment arms, the areas of thermal tissue damage and NPAs were not significantly different (P = 0.47). Areas denoted by 55°C isotherms and 240 CEM43 dose boundaries were significantly larger than the areas of thermal damage, again for all treatment arms (P = 0.009 and 0.003, respectively). No significant differences in lesion size, T1 contrast, or temperature were observed between any of the treatment arms (P > 0.0167). Lesions exhibiting thermal fixation on histological analysis were present in six of nine insonations involving sUPE injections and one of five insonations involving saline sham injections. Significantly larger areas (P = 0.002), higher temperatures (P = 0.004), and more frequent ring patterns of restricted diffusion on ex vivo diffusion-weighted imaging (P = 0.005) were apparent in lesions with thermal fixation. CONCLUSIONS T1 contrast suggesting sUPE transition was not evident in sUPE treatment arms. The use of MR imaging metrics to predict prostate ablation was not diminished by the presence of sUPEs. Lesions generated in the presence of sUPEs exhibited more frequent thermal fixation, though there were no significant changes in the ablation areas when comparing arms with and without sUPEs. Thermal fixation corresponded to some qualitative imaging features.
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Affiliation(s)
| | | | - James Wang
- The University of California San DiegoSan DiegoCA92093USA
| | | | | | | | | | | | | | - Sarah L. Blair
- The University of California San DiegoSan DiegoCA92093USA
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Scott SJ, Adams MS, Salgaonkar V, Sommer FG, Diederich CJ. Theoretical investigation of transgastric and intraductal approaches for ultrasound-based thermal therapy of the pancreas. J Ther Ultrasound 2017; 5:10. [PMID: 28469915 PMCID: PMC5414307 DOI: 10.1186/s40349-017-0090-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 02/07/2017] [Indexed: 02/07/2023] Open
Abstract
Background The goal of this study was to theoretically investigate the feasibility of intraductal and transgastric approaches to ultrasound-based thermal therapy of pancreatic tumors, and to evaluate possible treatment strategies. Methods This study considered ultrasound applicators with 1.2 mm outer diameter tubular transducers, which are inserted into the tissue to be treated by an endoscopic approach, either via insertion through the gastric wall (transgastric) or within the pancreatic duct lumen (intraductal). 8 patient-specific, 3D, transient, biothermal and acoustic finite element models were generated to model hyperthermia (n = 2) and ablation (n = 6), using sectored (210°–270°, n = 4) and 360° (n = 4) transducers for treatment of 3.3–17.0 cm3 tumors in the head (n = 5), body (n = 2), and tail (n = 1) of the pancreas. A parametric study was performed to determine appropriate treatment parameters as a function of tissue attenuation, blood perfusion rates, and distance to sensitive anatomy. Results Parametric studies indicated that pancreatic tumors up to 2.5 or 2.7 cm diameter can be ablated within 10 min with the transgastric and intraductal approaches, respectively. Patient-specific simulations demonstrated that 67.1–83.3% of the volumes of four sample 3.3–11.4 cm3 tumors could be ablated within 3–10 min using transgastric or intraductal approaches. 55.3–60.0% of the volume of a large 17.0 cm3 tumor could be ablated using multiple applicator positions within 20–30 min with either transgastric or intraductal approaches. 89.9–94.7% of the volume of two 4.4–11.4 cm3 tumors could be treated with intraductal hyperthermia. Sectored applicators are effective in directing acoustic output away from and preserving sensitive structures. When acoustic energy is directed towards sensitive structures, applicators should be placed at least 13.9–14.8 mm from major vessels like the aorta, 9.4–12.0 mm from other vessels, depending on the vessel size and flow rate, and 14 mm from the duodenum. Conclusions This study demonstrated the feasibility of generating shaped or conformal ablative or hyperthermic temperature distributions within pancreatic tumors using transgastric or intraductal ultrasound.
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Affiliation(s)
- Serena J Scott
- Department of Radiation Oncology, Thermal Therapy Research Group, University of California, San Francisco, 1600 Divisadero Street, Suite H1031, San Francisco, CA 94143-1708 USA
| | - Matthew S Adams
- Department of Radiation Oncology, Thermal Therapy Research Group, University of California, San Francisco, 1600 Divisadero Street, Suite H1031, San Francisco, CA 94143-1708 USA.,UC Berkeley - UC San Francisco Graduate Program in Bioengineering, California, USA
| | - Vasant Salgaonkar
- Department of Radiation Oncology, Thermal Therapy Research Group, University of California, San Francisco, 1600 Divisadero Street, Suite H1031, San Francisco, CA 94143-1708 USA
| | - F Graham Sommer
- Department of Radiology, Stanford University School of Medicine, Stanford, CA USA
| | - Chris J Diederich
- Department of Radiation Oncology, Thermal Therapy Research Group, University of California, San Francisco, 1600 Divisadero Street, Suite H1031, San Francisco, CA 94143-1708 USA.,UC Berkeley - UC San Francisco Graduate Program in Bioengineering, California, USA
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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.
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Affiliation(s)
- Vasant A Salgaonkar
- Department of Radiation Oncology, University of California , San Francisco, California , USA
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de Bever J, Todd N, Payne A, Christensen DA, Roemer RB. Adaptive model-predictive controller for magnetic resonance guided focused ultrasound therapy. Int J Hyperthermia 2014; 30:456-70. [DOI: 10.3109/02656736.2014.968223] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Goharrizi AY, Kwong R, Chopra R. Development of robust/predictive control strategies for image-guided ablative treatments using a minimally invasive ultrasound applicator. Int J Hyperthermia 2014; 30:438-46. [PMID: 25314227 DOI: 10.3109/02656736.2014.963702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
PURPOSE One important challenge in image-guided ablative therapies is the effect of heat diffusion which can cause damage to surrounding organs and limit the ability to achieve a conformal pattern of thermal damage. Furthermore, tissue properties such as perfusion and energy absorption can be dynamic and difficult to measure. This paper attempts to address these problems by proposing new control methods. MATERIALS AND METHODS A novel predictive approach was developed to compensate for the effect of heat diffusion using a minimally invasive rotating ultrasound heating applicator for ablative therapy. This method can be merged into any closed-loop control strategy. A binary controller, a previously developed adaptive proportional-integral controller, and a model reference adaptive controller were employed and compared, all with the predictive element incorporated. The reason for choosing these controllers was that none of them needed a model of the tissue or exact values of their parameters. RESULTS The effectiveness of these controllers was demonstrated through both simulation and experimental studies. The results were consistent and demonstrated equivalent performance between controllers. CONCLUSIONS The dominant influence on radial targeting accuracy was the prediction element described in this paper. A binary controller with a predictive element may provide the best balance of performance and simplicity for this application.
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Goharrizi AY, Kwong RH, Chopra R. A self-tuning adaptive controller for 3-D image-guided ultrasound cancer therapy. IEEE Trans Biomed Eng 2014; 61:911-9. [PMID: 24557692 DOI: 10.1109/tbme.2013.2292559] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
One of the challenges in MRI-controlled hyperthermia cancer treatment for localized tumor is that the tissue properties are dynamic and difficult to measure. Therefore, tuning the optimal gains for a constant gain controller can be challenging. In this paper, a new multi-input single-output adaptive controller strategy is proposed to address these problems. The inputs to the controller block are the frequency, rotation rate, and applied power level of an interstitial applicator, and the output is the boundary temperature during treatment. The time-varying gains of the new controller are updated over time using Lyapunov-based stability analysis. The robustness of the new controller to changes in the parameters of the tissue is investigated and compared to a constant gain controller through simulation studies. Simulations take into account changes in tissue properties and other conditions that may be encountered in a practical clinical situation. Finally, the effectiveness of the proposed controller is validated through an experimental study.
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Coakley FV, Foster BR, Farsad K, Hung AY, Wilder KJ, Amling CL, Caughey AB. Pelvic applications of MR-guided high intensity focused ultrasound. ACTA ACUST UNITED AC 2014; 38:1120-9. [PMID: 23589077 DOI: 10.1007/s00261-013-9999-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
MR-guided high intensity focused ultrasound (MRg HIFU) is a novel method of tissue ablation that incorporates high energy focused ultrasound for tissue heating and necrosis within an MR scanner that provides simultaneous stereotactic tissue targeting and thermometry. To date, MRg HIFU has been used primarily to treat uterine fibroids, but many additional applications in the pelvis are in development. This article reviews the basic technology of MRg HIFU, and the use of MRg HIFU to treat uterine fibroids, adenomyosis, and prostate cancer.
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Affiliation(s)
- Fergus V Coakley
- Department of Diagnostic Radiology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Mail Code: L340, Portland, OR, 97239, USA,
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10
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Scott SJ, Prakash P, Salgaonkar V, Jones PD, Cam RN, Han M, Rieke V, Burdette EC, Diederich CJ. Approaches for modelling interstitial ultrasound ablation of tumours within or adjacent to bone: theoretical and experimental evaluations. Int J Hyperthermia 2014; 29:629-42. [PMID: 24102393 DOI: 10.3109/02656736.2013.841327] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
PURPOSE The objectives of this study were to develop numerical models of interstitial ultrasound ablation of tumours within or adjacent to bone, to evaluate model performance through theoretical analysis, and to validate the models and approximations used through comparison to experiments. METHODS 3D transient biothermal and acoustic finite element models were developed, employing four approximations of 7-MHz ultrasound propagation at bone/soft tissue interfaces. The various approximations considered or excluded reflection, refraction, angle-dependence of transmission coefficients, shear mode conversion, and volumetric heat deposition. Simulations were performed for parametric and comparative studies. Experiments within ex vivo tissues and phantoms were performed to validate the models by comparison to simulations. Temperature measurements were conducted using needle thermocouples or magnetic resonance temperature imaging (MRTI). Finite element models representing heterogeneous tissue geometries were created based on segmented MR images. RESULTS High ultrasound absorption at bone/soft tissue interfaces increased the volumes of target tissue that could be ablated. Models using simplified approximations produced temperature profiles closely matching both more comprehensive models and experimental results, with good agreement between 3D calculations and MRTI. The correlation coefficients between simulated and measured temperature profiles in phantoms ranged from 0.852 to 0.967 (p-value < 0.01) for the four models. CONCLUSIONS Models using approximations of interstitial ultrasound energy deposition around bone/soft tissue interfaces produced temperature distributions in close agreement with comprehensive simulations and experimental measurements. These models may be applied to accurately predict temperatures produced by interstitial ultrasound ablation of tumours near and within bone, with applications toward treatment planning.
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Affiliation(s)
- Serena J Scott
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California , San Francisco , California
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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.
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Affiliation(s)
- David Schlesinger
- Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908, USA.
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12
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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.
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Phillips LC, Puett C, Sheeran PS, Wilson Miller G, Matsunaga TO, Dayton PA. Phase-shift perfluorocarbon agents enhance high intensity focused ultrasound thermal delivery with reduced near-field heating. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:1473-82. [PMID: 23927187 PMCID: PMC3745500 DOI: 10.1121/1.4812866] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 01/04/2013] [Accepted: 01/08/2013] [Indexed: 05/19/2023]
Abstract
Ultrasound contrast agents are known to enhance high intensity focused ultrasound (HIFU) ablation, but these perfluorocarbon microbubbles are limited to the vasculature, have a short half-life in vivo, and may result in unintended heating away from the target site. Herein, a nano-sized (100-300 nm), dual perfluorocarbon (decafluorobutane/dodecafluoropentane) droplet that is stable, is sufficiently small to extravasate, and is convertible to micron-sized bubbles upon acoustic activation was investigated. Microbubbles and nanodroplets were incorporated into tissue-mimicking acrylamide-albumin phantoms. Microbubbles or nanodroplets at 0.1 × 10(6) per cm(3) resulted in mean lesion volumes of 80.4 ± 33.1 mm(3) and 52.8 ± 14.2 mm(3) (mean ± s.e.), respectively, after 20 s of continuous 1 MHz HIFU at a peak negative pressure of 4 MPa, compared to a lesion volume of 1.0 ± 0.8 mm(3) in agent-free control phantoms. Magnetic resonance thermometry mapping during HIFU confirmed undesired surface heating in phantoms containing microbubbles, whereas heating occurred at the acoustic focus of phantoms containing the nanodroplets. Maximal change in temperature at the target site was enhanced by 16.9% and 37.0% by microbubbles and nanodroplets, respectively. This perfluorocarbon nanodroplet has the potential to reduce the time to ablate tumors by one-third during focused ultrasound surgery while also safely enhancing thermal deposition at the target site.
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Affiliation(s)
- Linsey C Phillips
- Department of Biomedical Engineering, University of North Carolina at Chapel Hill, 109 Mason Farm Road, 304 Taylor Hall, CB 7575, Chapel Hill, North Carolina 27599, USA.
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Vincenot J, Melodelima D, Chavrier F, Vignot A, Kocot A, Chapelon JY. Electronic beam steering used with a toroidal HIFU transducer substantially increases the coagulated volume. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1241-54. [PMID: 23643055 DOI: 10.1016/j.ultrasmedbio.2013.01.019] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 12/29/2012] [Accepted: 01/27/2013] [Indexed: 05/09/2023]
Abstract
Treatment with high-intensity focused ultrasound is well established but requires extended treatment time. A device composed of 256 elements arranged on a toroidal transducer was developed to increase the coagulated volume. When all the elements are working in phase for 40 s, a volume of 6-8 cm(3) can be ablated. However, the mechanical juxtaposition of single lesions is still necessary for treating one tumor with a diameter of 2 cm. The objective of this study was to combine this toroidal transducer geometry with electronic beam steering to ablate tumors with adequate normal tissue margins and without any mechanical displacement of the high-intensity focused ultrasound device. In vitro tests demonstrated that the coagulated volume obtained from 130 s of total exposure has an average diameter of 41.4 ± 4.0 mm and an average length of 53.3 ± 6.1 mm. This single lesion can be used to treat various size of metastasis, located at depths in the liver ranging 5-45 mm.
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Prakash P, Salgaonkar VA, Diederich CJ. Modelling of endoluminal and interstitial ultrasound hyperthermia and thermal ablation: applications for device design, feedback control and treatment planning. Int J Hyperthermia 2013; 29:296-307. [PMID: 23738697 PMCID: PMC4087028 DOI: 10.3109/02656736.2013.800998] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Endoluminal and catheter-based ultrasound applicators are currently under development and are in clinical use for minimally invasive hyperthermia and thermal ablation of various tissue targets. Computational models play a critical role in device design and optimisation, assessment of therapeutic feasibility and safety, devising treatment monitoring and feedback control strategies, and performing patient-specific treatment planning with this technology. The critical aspects of theoretical modelling, applied specifically to endoluminal and interstitial ultrasound thermotherapy, are reviewed. Principles and practical techniques for modeling acoustic energy deposition, bioheat transfer, thermal tissue damage, and dynamic changes in the physical and physiological state of tissue are reviewed. The integration of these models and applications of simulation techniques in identification of device design parameters, development of real time feedback-control platforms, assessing the quality and safety of treatment delivery strategies, and optimisation of inverse treatment plans are presented.
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Affiliation(s)
- Punit Prakash
- Department of Electrical and Computer Engineering, Kansas State University, Manhattan, KS 66506, USA.
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Sommer G, Bouley D, Gill H, Daniel B, Pauly KB, Diederich C. Focal ablation of prostate cancer: four roles for magnetic resonance imaging guidance. THE CANADIAN JOURNAL OF UROLOGY 2013; 20:6672-6681. [PMID: 23587506 PMCID: PMC4045501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
INTRODUCTION There is currently a great deal of interest in the possible use of focal therapies for prostate cancer, since such treatments offer the prospect for control or cure of the primary disease with minimal side effects. Many forms of thermal therapy have been proposed for focal ablation of prostate cancer, including laser, high intensity ultrasound and cryotherapy. This review will demonstrate the important roles that magnetic resonance imaging (MRI) guidance can offer to such focal ablation, focusing on the use of high intensity ultrasonic applicators as an example of one promising technique. MATERIALS AND METHODS Transurethral and interstitial high intensity ultrasonic applicators, designed specifically for ablation of prostate tissue were tested extensively in vivo in a canine model. The roles of MRI in positioning the devices, monitoring prostate ablation, and depicting ablated tissue were assessed using appropriate MRI sequences. RESULTS MRI guidance provides a very effective tool for the positioning of ablative devices in the prostate, and thermal monitoring successfully predicted ablation of prostate tissue when a threshold of 52 ºC was achieved. Contrast enhanced MRI accurately depicted the distribution of ablated prostate tissue, which is resorbed at 30 days. CONCLUSIONS Guidance of thermal therapies for focal ablation of prostate cancer will likely prove critically dependent on MRI functioning in four separate roles. Our studies indicate that in three roles: device positioning; thermal monitoring of prostate ablation; and depiction of ablated prostate tissue, MR techniques are highly accurate and likely to be of great benefit in focal prostate cancer ablation. A fourth critical role, identification of cancer within the gland for targeting of thermal therapy, is more problematic at present, but will likely become practical with further technological advances.
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Affiliation(s)
- Graham Sommer
- Department of Radiology, Standford University School of Medicine
| | - Donna Bouley
- Department of Comparative Medicine, Standford University School of Medicine
| | - Harcharan Gill
- Department of Urology, Stanford University School of Medicine
| | - Bruce Daniel
- Department of Radiology, Standford University School of Medicine
| | - Kim Butts Pauly
- Department of Radiology, Standford University School of Medicine
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Goharrizi AY, N'Djin WA, Kwong R, Chopra R. Development of a new control strategy for 3D MRI-controlled interstitial ultrasound cancer therapy. Med Phys 2013; 40:033301. [DOI: 10.1118/1.4793261] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Napoli A, Cartocci G, Boni F, Del Monte M, Noce V, Anzidei M, Catalano C. Focused Ultrasound Therapy of the Prostate with MR Guidance. CURRENT RADIOLOGY REPORTS 2013. [DOI: 10.1007/s40134-013-0011-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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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]
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Zini C, Hipp E, Thomas S, Napoli A, Catalano C, Oto A. Ultrasound- and MR-guided focused ultrasound surgery for prostate cancer. World J Radiol 2012; 4:247-52. [PMID: 22778876 PMCID: PMC3391669 DOI: 10.4329/wjr.v4.i6.247] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 05/15/2012] [Accepted: 05/22/2012] [Indexed: 02/06/2023] Open
Abstract
Prostate cancer (PC) is one of the most frequently diagnosed cancers in men. There are a number of treatment options for PC with a different therapeutic approach between USA and Europe. Radical prostatectomy is one of the most used therapies but focal gland therapy is an emerging approach, especially for localized tumors. In this scenario, high intensity focused ultrasound (HIFU) has been incorporated in certain medical association guidelines. HIFU has been employed for about 10 years especially for localized PC. Results are promising with a 5-year biochemical survival rate ranging from 45% to 84%. Collateral events are rare and HIFU retreatment is not common. Magnetic resonance guided focused ultrasound surgery (MRgFUS) was recently presented as a method for ablation with focused ultrasound under magnetic resonance imaging guidance. It has the advantage of improved targeting and real time temperature monitoring but only a few studies have been conducted with human patients. The aim of this review is to describe the current status of HIFU and MRgFUS in the therapy of PC.
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Prakash P, Diederich CJ. Considerations for theoretical modelling of thermal ablation with catheter-based ultrasonic sources: implications for treatment planning, monitoring and control. Int J Hyperthermia 2012; 28:69-86. [PMID: 22235787 DOI: 10.3109/02656736.2011.630337] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PURPOSE To determine the impact of including dynamic changes in tissue physical properties during heating on feedback controlled thermal ablation with catheter-based ultrasound. Additionally, we compared the impact of several indicators of thermal damage on predicted extents of ablation zones for planning and monitoring ablations with this modality. METHODS A 3D model of ultrasound ablation with interstitial and transurethral applicators incorporating temperature-based feedback control was used to simulate thermal ablations in prostate and liver tissue. We investigated five coupled models of heat dependent changes in tissue acoustic attenuation/absorption and blood perfusion of varying degrees of complexity. Dimensions of the ablation zone were computed using temperature, thermal dose, and Arrhenius thermal damage indicators of coagulative necrosis. A comparison of the predictions by each of these models was illustrated on a patient-specific anatomy in the treatment planning setting. RESULTS Models including dynamic changes in blood perfusion and acoustic attenuation as a function of thermal dose/damage predicted near-identical ablation zone volumes (maximum variation < 2.5%). Accounting for dynamic acoustic attenuation appeared to play a critical role in estimating ablation zone size, as models using constant values for acoustic attenuation predicted ablation zone volumes up to 50% larger or 47% smaller in liver and prostate tissue, respectively. Thermal dose (t(43) ≥ 240 min) and thermal damage (Ω ≥ 4.6) thresholds for coagulative necrosis are in good agreement for all heating durations, temperature thresholds in the range of 54°C for short (<5 min) duration ablations and 50°C for long (15 min) ablations may serve as surrogates for determination of the outer treatment boundary. CONCLUSIONS Accounting for dynamic changes in acoustic attenuation/absorption appeared to play a critical role in predicted extents of ablation zones. For typical 5-15 min ablations with this modality, thermal dose and Arrhenius damage measures of ablation zone dimensions are in good agreement, while appropriately selected temperature thresholds provide a computationally cheaper surrogate.
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Affiliation(s)
- Punit Prakash
- Thermal Therapy Research Group, Department of Radiation Oncology, University of California-San Francisco, CA 94143, USA.
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Miller DL, Smith NB, Bailey MR, Czarnota GJ, Hynynen K, Makin IRS. Overview of therapeutic ultrasound applications and safety considerations. JOURNAL OF ULTRASOUND IN MEDICINE : OFFICIAL JOURNAL OF THE AMERICAN INSTITUTE OF ULTRASOUND IN MEDICINE 2012; 31:623-34. [PMID: 22441920 PMCID: PMC3810427 DOI: 10.7863/jum.2012.31.4.623] [Citation(s) in RCA: 331] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Applications of ultrasound in medicine for therapeutic purposes have been accepted and beneficial uses of ultrasonic biological effects for many years. Low-power ultrasound of about 1 MHz has been widely applied since the 1950s for physical therapy in conditions such as tendinitis and bursitis. In the 1980s, high-pressure-amplitude shock waves came into use for mechanically resolving kidney stones, and "lithotripsy" rapidly replaced surgery as the most frequent treatment choice. The use of ultrasonic energy for therapy continues to expand, and approved applications now include uterine fibroid ablation, cataract removal (phacoemulsification), surgical tissue cutting and hemostasis, transdermal drug delivery, and bone fracture healing, among others. Undesirable bioeffects can occur, including burns from thermal-based therapies and severe hemorrhage from mechanical-based therapies (eg, lithotripsy). In all of these therapeutic applications of ultrasound bioeffects, standardization, ultrasound dosimetry, benefits assurance, and side-effect risk minimization must be carefully considered to ensure an optimal benefit to risk ratio for the patient. Therapeutic ultrasound typically has well-defined benefits and risks and therefore presents a manageable safety problem to the clinician. However, safety information can be scattered, confusing, or subject to commercial conflicts of interest. Of paramount importance for managing this problem is the communication of practical safety information by authoritative groups, such as the American Institute of Ultrasound in Medicine, to the medical ultrasound community. In this overview, the Bioeffects Committee of the American Institute of Ultrasound in Medicine outlines the wide range of therapeutic ultrasound methods, which are in clinical use or under study, and provides general guidance for ensuring therapeutic ultrasound safety.
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Affiliation(s)
- Douglas L Miller
- Department of Radiology, University of Michigan, 3240A Medical Science Building I, 1301 Catherine St, Ann Arbor, MI 48109-5667, USA.
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Yarmolenko PS, Moon EJ, Landon C, Manzoor A, Hochman DW, Viglianti BL, Dewhirst MW. Thresholds for thermal damage to normal tissues: an update. Int J Hyperthermia 2011; 27:320-43. [PMID: 21591897 DOI: 10.3109/02656736.2010.534527] [Citation(s) in RCA: 416] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The purpose of this review is to summarise a literature survey on thermal thresholds for tissue damage. This review covers published literature for the consecutive years from 2002-2009. The first review on this subject was published in 2003. It included an extensive discussion of how to use thermal dosimetric principles to normalise all time-temperature data histories to a common format. This review utilises those same principles to address sensitivity of a variety of tissues, but with particular emphasis on brain and testis. The review includes new data on tissues that were not included in the original review. Several important observations have come from this review. First, a large proportion of the papers examined for this review were discarded because time-temperature history at the site of thermal damage assessment was not recorded. It is strongly recommended that future research on this subject include such data. Second, very little data is available examining chronic consequences of thermal exposure. On a related point, the time of assessment of damage after exposure is critically important for assessing whether damage is transient or permanent. Additionally, virtually no data are available for repeated thermal exposures which may occur in certain recreational or occupational activities. For purposes of regulatory guidelines, both acute and lasting effects of thermal damage should be considered.
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Affiliation(s)
- Pavel S Yarmolenko
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
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Tempany CMC, McDannold NJ, Hynynen K, Jolesz FA. Focused ultrasound surgery in oncology: overview and principles. Radiology 2011; 259:39-56. [PMID: 21436096 DOI: 10.1148/radiol.11100155] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Focused ultrasound surgery (FUS) is a noninvasive image-guided therapy and an alternative to surgical interventions. It presents an opportunity to revolutionize cancer therapy and to affect or change drug delivery of therapeutic agents in new focally targeted ways. In this article the background, principles, technical devices, and clinical cancer applications of image-guided FUS are reviewed.
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Affiliation(s)
- Clare M C Tempany
- Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St, Room 050, L1, Boston, MA 02129, USA.
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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
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Bouchoux G, Owen N, Chavrier F, Berriet R, Fleury G, Chapelon JY, Lafon C. Interstitial thermal ablation with a fast rotating dual-mode transducer. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2010; 57:1086-1095. [PMID: 20442018 DOI: 10.1109/tuffc.2010.1520] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Interstitial ultrasound applicators can be a minimally invasive alternative for treating targets that are unresectable or are inaccessible by extracorporeal methods. Dual-mode transducers for ultrasound imaging and therapy were developed to address the constraints of a miniaturized applicator and real-time treatment monitoring. We propose an original treatment strategy that combines ultrasound imaging and therapy using a dual-mode transducer rotating at 8 revolutions per second. Real-time B-mode imaging was interrupted to emit high-intensity ultrasound over a selected therapy aperture. A full 360 degrees image was taken every 8th rotation to image the therapy aperture. Numerical simulations were performed to study the effect of rotation on tissue heating, and to study the effect of the treatment sequence on transducer temperature. With the time-averaged transducer surface intensity held at 12 W/cm(2) to maintain transducer temperature below 66 degrees C, higher field intensities and deeper lesions were produced by narrower therapy apertures. A prototype system was built and tested using in vitro samples of porcine liver. Lesions up to 8 mm were produced using a time-averaged transducer surface intensity of 12 W/cm(2) applied for a period of 240 s over a therapy aperture of 40 degrees. Apparent strain imaging of the therapy aperture improved the contrast between treated and spared tissues, which could not be differentiated on B-mode images. With appropriate limits on the transducer output, real-time imaging and deep thermal ablation are feasible and sustainable using a rotating dual-mode transducer.
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Affiliation(s)
- Guillaume Bouchoux
- Institut National de la Sante et de la Recherche Medicale (Inserm), U556 Lyon, France
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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.
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Affiliation(s)
- Lorena Petrusca
- National Institute for Health and Medical ResearchU556, Lyon 69424, France.
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Owen NR, Bouchoux G, Seket B, Murillo-Rincon A, Merouche S, Birer A, Paquet C, Delabrousse E, Chapelon JY, Berriet R, Fleury G, Lafon C. In vivo evaluation of a mechanically oscillating dual-mode applicator for ultrasound imaging and thermal ablation. IEEE Trans Biomed Eng 2009; 57:80-92. [PMID: 19497808 DOI: 10.1109/tbme.2009.2023994] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here, we report the in vivo evaluation of an interstitial applicator with a mechanically oscillating five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120-s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 or 27 W/cm (2). Electroacoustic conversion efficiency was maximally 72 +/- 3% and impulse response length was 295 +/- 1.0 ns at -6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six sites, M-mode data exhibited a reduction in gray-scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the gray-scale intensity dropped by 7.8 +/- 3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 +/- 2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring.
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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.
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Affiliation(s)
- Rajiv Chopra
- Imaging Research, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
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