MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Chopra, Rajiv; Burtnyk, Mathieu; N’Djin, W. Apoutou; Bronskill, Michael

doi:10.3109/02656736.2010.503670

Cited by 37 publications

(22 citation statements)

References 69 publications

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“…13,14 MR-HIFU is already clinically used for ablative treatments of, e.g., uterine fibroids, [15][16][17][18][19][20] bone metastasis, 21,22 and prostate cancer. [23][24][25] Investigations for using MR-HIFU for administering mild hyperthermia are also ongoing. [26][27][28][29] The volume heated by a HIFU transducer is usually small and the heating pattern is dominated by the transducer geometry and sonication frequency.…”

Section: Introductionmentioning

confidence: 99%

High intensity focused ultrasound induced in vivo large volume hyperthermia under 3D MRI temperature control

et al. 2016

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Purpose: Mild hyperthermia can be used as an adjuvant therapy to enhance radiation therapy or chemotherapy of cancer. However, administering mild hyperthermia is technically challenging due to the high accuracy required of the temperature control. MR guided high-intensity focused ultrasound (MR-HIFU) is a technology that can address this challenge. In this work, accurate and spatially uniform mild hyperthermia is demonstrated for deep-seated clinically relevant heating volumes using a HIFU system under MR guidance. Methods: Mild hyperthermia heating was evaluated for temperature accuracy and spatial uniformity in 11 in vivo porcine leg experiments. Hyperthermia was induced with a commercial Philips Sonalleve MR-HIFU system embedded in a 1.5T Ingenia MR scanner. The operating software was modified to allow extended duration mild hyperthermia. Heating time varied from 10 min up to 60 min and the assigned target temperature was 42.5• C. Electronic focal point steering, mechanical transducer movement, and dynamic transducer element switch-off were exploited to enlarge the heated volume and obtain uniform heating throughout the acoustic beam path. Multiple temperature mapping images were used to control and monitor the heating. The magnetic field drift and transducer susceptibility artifacts were compensated to enable accurate volumetric MR thermometry. Results: The obtained mean temperature for the target area (the cross sectional area of the heated volume at focal depth primarily used to control the heating) was on average 42.0 ± 0.6• C. Temperature uniformity in the target area was evaluated using T10 and T90, which were 43.1 ± 0.6 and 40.9 ± 0.6• C, respectively. For the near field, the corresponding temperatures were 39.3 ± 0.8• C (average), 40.6 ± 1.0• C (T10), and 38.0 ± 0.9• C (T90). The sonications resulted in a concise heating volume, typically in the shape of a truncated cone. The average depth reached from the skin was 86.9 mm. The results show that the heating algorithm was able to induce deep heating while keeping the near-field temperature uniform and at a safe level. Conclusions: The capability of MR-HIFU to induce accurate, spatially uniform, and robust mild hyperthermia in large deep-seated volumes was successfully demonstrated through a series of in vivo animal experiments. C

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Section: Introductionmentioning

confidence: 99%

High intensity focused ultrasound induced in vivo large volume hyperthermia under 3D MRI temperature control

et al. 2016

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“…Maximum temperature maps are shown in Figure 4 in a central thermometry slice of two simulated prostate treatments at two frequencies (4 and 8 MHz) and two surface acoustic powers [46,48], and recently in a human pilot study [68]), the device was able to treat the full prostate gland only for volumes less than 21 cm 3 ( Figure 4A, top), at the low end of expected prostate volumes in humans. For larger glands as shown in Figure 4A (bottom), the limited R max at 8 MHz led to significant undertreatment which was not improved by doubling the acoustic power due to Tmax i reaching Th between the device and prostate boundary ( Figure 4B).…”

Section: Numerical Simulationsmentioning

confidence: 97%

Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer

N’Djin

Burtnyk

Bronskill

et al. 2012

International Journal of Hyperthermia

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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.

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“…Such studies have clearly indicated the potential of using MRI to plan, monitor and evaluate tissue changes during and after prostatic ablation with such applicators, and indicate promise for controlled ablation of targeted prostate tissues with minimal damage to sensitive adjacent structures, and minimal side effects. Recently 15,16 , the feasibility of ablation of human prostatic tissues using MRI-compatible transurethral applicators incorporating planar piezoelectrics and controlled rotation has been demonstrated, furthering the preliminary translation of these MRI-guided transurethral technologies into the clinical environment.…”

Section: Introductionmentioning

confidence: 98%

Applicators for Magnetic Resonance–Guided Ultrasonic Ablation of Benign Prostatic Hyperplasia

Sommer¹,

Pauly²,

Holbrook³

et al. 2013

Investigative Radiology

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Objectives To evaluate in a canine model, applicators designed for ablation of human benign prostatic hyperplasia (BPH) in vivo under MRI guidance, including magnetic resonance thermal imaging (MRTI). To determine the ability of MRI techniques to visualize ablative changes in prostate, and to evaluate the acute and longer term histologic appearances of prostate tissue ablated during these studies. Materials and Methods A MRI-compatible transurethral device incorporating a tubular transducer array with dual 120 sectors was employed to ablate canine prostate tissue in vivo, in zones similar to regions of human BPH (enlarged transition zones (TZ)). MRTI was used for monitoring of ablation in a 3T environment, and post-ablation MRI's were performed to determine visibility of ablated regions. Three canine prostates were ablated in acute studies, and 2 animals were rescanned prior to sacrifice at 31 days post ablation. Acute and chronic appearances of ablated prostate tissue were evaluated histologically, and correlated with the MRTI and post ablation MRI scans. Results It was possible to ablate regions similar in size to enlarged TZ in human BPH in 5 to 15 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 MR images. The ability accurately to monitor prostate tissue heating, the apparent resorption of ablated regions over one month, and the inherent urethral preservation suggest the MR guided technques described are highly promising for the in vivo ablation of symptomatic human BPH.

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MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Cited by 37 publications

References 69 publications

High intensity focused ultrasound induced in vivo large volume hyperthermia under 3D MRI temperature control

High intensity focused ultrasound induced in vivo large volume hyperthermia under 3D MRI temperature control

Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer

Applicators for Magnetic Resonance–Guided Ultrasonic Ablation of Benign Prostatic Hyperplasia

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