Multifrequency ultrasound transducers for conformal interstitial thermal therapy

Chopra, Rajiv; Luginbuhl, C.; Foster, F. Stuart; Bronskill, Michael

doi:10.1109/tuffc.2003.1214507

Cited by 45 publications

(27 citation statements)

References 23 publications

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“…Some of the techniques that have been considered are: applicator cooling (catheter cooled vs. internally cooled), 15,17,35 transducer sizes and shapes, [36][37][38] multifrequency transducers 39 and power modulation schemes. 40 While some studies have explored the feasibility of multiple applicator ablation with catheter-based ultrasound devices, there have been few systematic studies of multiple applicator configurations for treatment of large volume targets in the liver.…”

Section: Introductionmentioning

confidence: 99%

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

et al. 2012

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Purpose: To evaluate multiple applicator implant configurations of interstitial ultrasound devices for large volume ablation of liver tumors. Methods: A 3D bioacoustic-thermal model using the finite element method was implemented to assess multiple applicator implant configurations for thermal ablation with interstitial ultrasound energy. Interstitial applicators consist of linear arrays of up to four 10 mm-long tubular ultrasound transducers, each under separate and dynamic power control, enclosed within a water-cooled delivery catheter (2.4 mm OD). The authors considered parallel implants with two and three applicators (clustered configuration), spaced 2-3 cm apart, to simulate open surgical placement. In addition, the authors considered two applicator implants with applicators converging and diverging at angles of ∼20• , 30• , and 45• to simulate percutaneous placement. Heating experiments (10-15 min) were performed and compared against simulations employing the same experimental parameters. To estimate the performance of parallel, multiple applicator configurations in an in vivo setting, simulations were performed taking into account a range of blood perfusion levels (0, 5, 12, and 15 kg m −3 s −1 ) that may occur in tumors of varying vascularity. The impact of tailoring the power supplied to individual transducer elements along the length of applicators is explored for applicators inserted in non-parallel (converging and diverging) configurations. Thermal dose (t 43 > 240 min) and temperature thresholds (T > 52• C) were used to define the ablation zones, with dynamic changes to tissue acoustic and thermal properties incorporated within the model. Results: Experiments in ex vivo bovine liver yielded ablation zones ranging between 4.0-5.6 cm × 3.2-4.9 cm, in cross section. Ablation zone dimensions predicted by simulations with similar parameters to the experiments were in close agreement (within 5 mm). Simulations of in vivo heating showed that 15 min heating and interapplicator spacing less than 3 cm are required to obtain contiguous, complete ablation zones. The ability to create complete ablation zone profiles for nonparallel implants was illustrated by tailoring applied power levels along the length of applicators. Conclusions: Parallel implants consisting of three interstitial ultrasound applicators in a triangular configuration yield complete ablation zones measuring up to 6.2 cm × 5.7 cm after 15 min heating. At larger interapplicator spacing, the level of blood perfusion in the tumor may yield indentations along the periphery of the ablation zone. Tailoring applied power along the length of the applicator can accommodate for nonparallel implants, without compromising safety.

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Section: Introductionmentioning

confidence: 99%

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

et al. 2012

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“…The transducer shape and frequency affect the penetration of ultrasound energy; the planar transducer has a narrow, penetrating unfocused beam, the curvilinear transducer lightly focuses ultrasound energy, producing a narrower beam compared to the planar transducer, and the tubular transducer exhibits a radial decay (1/r) of energy emitted over a predefined sector with distance. Recent efforts by Chopra et al [19,27] have developed a planar transducer configuration that allows frequency modulation between 4.7 MHz and 10 MHz to adjust the radial depth of average energy deposition. The specific applicator configuration and corresponding energy penetration must be carefully considered in order to properly target specific treatment zones, reduce treatment duration, and avoid the accumulation of thermal dose in sensitive structures beyond the prostate.…”

Section: Introductionmentioning

confidence: 99%

Prostate thermal therapy with high intensity transurethral ultrasound: The impact of pelvic bone heating on treatment delivery

Wootton

Ross

Diederich

2007

International Journal of Hyperthermia

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“…An approximation to the Rayleigh-Sommerfeld integral was used to calculate high spatial resolution ultrasound fields (0.25 mm isotropic) generated by these small virtual transducer elements. The frequencies were set to 4.7 and 9.7 MHz to provide the range of depth of heating required to treat the segmented prostate volumes [5]. An explicit finitedifference solution to the Bioheat Transfer Equation (BHTE) was used to model tissue temperature dynamics considering heat conduction, blood perfusion and ultrasound energy deposition at a temporal and spatial resolution of 1 s and 1 mm 3 respectively.…”

Section: Methodsmentioning

confidence: 99%

Theoretical Analysis of the Accuracy and Safety of MRI-Guided Transurethral 3-D Conformal Ultrasound Prostate Therapy

Burtnyk

Chopra²,

Bronskill

2009

AIP Conference Proceedings

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Multifrequency ultrasound transducers for conformal interstitial thermal therapy

Cited by 45 publications

References 23 publications

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

Multiple applicator hepatic ablation with interstitial ultrasound devices: Theoretical and experimental investigation

Prostate thermal therapy with high intensity transurethral ultrasound: The impact of pelvic bone heating on treatment delivery

Theoretical Analysis of the Accuracy and Safety of MRI-Guided Transurethral 3-D Conformal Ultrasound Prostate Therapy

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