3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms

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

doi:10.1088/0031-9155/55/22/014

Cited by 20 publications

(17 citation statements)

References 48 publications

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“…41 The attenuation coefficient at 1 MHz was measured to be 0.56 dB cm −1 . 36 These properties are similar to data reported by Duck 42 for biological tissues. Transurethral ultrasound applicators were inserted into the center of a cylindrical container (diameter: 11 cm) which was placed in the standard quadrature head coil of a 3.0 T MR imager (Discovery MR750, GE HealthCare) parallel to the main magnetic field B 0 .…”

Section: Iid Tissue-mimicking Phantom Experimentssupporting

confidence: 88%

“…47 A dual-frequency strategy was showed to provide a better treatment solution by eliminating bone-related tissue damages. While neither of these situations could be confirmed with the simple gel phantoms used in these experiments, the excellent agreement between simulations with no perfusion and gel phantom experiments over a wide range of frequency and power conditions 36,38 provides confidence in the results of the simulations.…”

Section: Discussionmentioning

confidence: 79%

“…Higher SNR provided greater flexibility in imaging parameters such that more simultaneous thermometry planes could be acquired. The number of imaging planes acquired in the prostate volume was increased from five used in previous studies 36,38 to nine, while keeping an acceptable MR acquisition time of 7 s compared to the previous 5 s. The spatial resolution was also enhanced by increasing the size of the acquired matrix from 64 × 128 pixels to 128 × 128 pixels while maintaining good SNR and temperature uncertainty. The measured temperature uncertainty was ±1…”

Section: Iiib1 Experimental Mr Thermometry Feedback Control Of Thementioning

confidence: 99%

“…15,[22][23][24][25][26][27][28][29][30][31][32] Our group has been developing a MRI-controlled transurethral ultrasound therapy system for treatment of localized prostate cancer. 15,[32][33][34][35][36][37][38] Compared with transrectal HIFU, transurethral delivery enables the use of simple planar unfocused transducers within the prostate, avoiding the need to propagate sound through sensitive structures such as the rectal wall. The continuous delivery of ultrasound energy from multiple planar transducers enables a higher volumetric rate of coagulation compared with a focused approach.…”

Section: Introductionmentioning

confidence: 99%

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Coagulation of human prostate volumes with MRI-controlled transurethral ultrasound therapy: Results in gel phantoms

et al. 2012

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Purpose:The feasibility and safety of magnetic resonance imaging (MRI)-controlled transurethral ultrasound therapy were demonstrated recently in a preliminary human study in which a small subvolume of prostate tissue was treated prior to radical prostatectomy. Translation of this technology to full clinical use, however, requires the capability to generate thermal coagulation in a volume up to that of the prostate gland itself. The aim of this study was to investigate the parameters required to treat a full 3D human prostate accurately with a multi-element transurethral applicator and multiplanar MR temperature control. Methods: The approach was a combination of simulations (to select appropriate parameters) followed by experimental confirmation in tissue-mimicking phantoms. A ten-channel, MRI-compatible transurethral ultrasound therapy system was evaluated using six human prostate models (average volume: 36 cm 3 ) obtained from the preliminary human feasibility study. Real-time multiplanar MR thermometry at 3 T was used to control the spatial heating pattern in up to nine planes simultaneously. Treatment strategies incorporated both single (4.6 or 8.1 MHz) and dual (4.6 and 14.4 MHz) frequencies, as well as maximum acoustic surface powers of 10 or 20 W cm −2 . Results: Treatments at 4.6 MHz were capable of coagulating a volume equivalent to 97% of the prostate. Increasing power from 10 to 20 W cm −2 reduced treatment times by approximately 50% with full treatments taking 26 ± 3 min at a coagulation rate of 1.8 ± 0.4 cm 3 min −1 . A dual-frequency 4.6/14.4 MHz treatment strategy was shown to be the most effective configuration for achieving full human prostate treatment while maintaining good treatment accuracy for small treatment radii. The dual-frequency approach reduced overtreatment close to the prostate base and apex, confirming the simulations. Conclusions: This study reinforces the capability of MRI-controlled transurethral ultrasound therapy to treat full prostate volumes in a short treatment time with good spatial targeting accuracy and provides key parameters necessary for the next clinical trial.

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Section: Iid Tissue-mimicking Phantom Experimentssupporting

confidence: 88%

Section: Discussionmentioning

confidence: 79%

Section: Iiib1 Experimental Mr Thermometry Feedback Control Of Thementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coagulation of human prostate volumes with MRI-controlled transurethral ultrasound therapy: Results in gel phantoms

et al. 2012

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“…On the contrary, the neighboring rectal wall, where accurate temperature measurements are important to ensure no thermal damage, 21,22 can be affected by random motion caused by the presence of moving gas pockets or peristalsis of the organ. PRFS method relies on accurate registration of the reference and current phase images, as well as on an unmodified background magnetic field, as observed in the following equation, showing the resulting phase variation (∆ρ) dependence to both temperature and local magnetic susceptibility:…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal filtering of MR‐temperature artifacts arising from bowel motion during transurethral MR‐HIFU

2014

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Purpose: Transurethral MR-HIFU is a minimally invasive image-guided treatment for localized prostate cancer that enables precise targeting of tissue within the gland. The treatment is performed within a clinical MRI to obtain real-time MR thermometry used as an active feedback to control the spatial heating pattern in the prostate and to monitor for potential damage to surrounding tissues. This requires that the MR thermometry measurements are an accurate representation of the true tissue temperature. The proton resonance frequency shift thermometry method used is sensitive to tissue motion and changes in the local magnetic susceptibility that can be caused by the motion of air bubbles in the rectum, which can impact the performance of transurethral MR-HIFU in these regions of the gland. Methods: A method is proposed for filtering of temperature artifacts based on the temporal variance of the temperature, using empirical and dynamic positional knowledge of the ultrasonic heating beam, and an estimation of the measurement noise. A two-step correction strategy is introduced which eliminates artifact-detected temperature variations while keeping the noise level low through spatial averaging. Results: The filter has been evaluated by postprocessing data from five human transurethral ultrasound treatments. The two-step correction process led to reduced final temperature standard deviation in the prostate and rectum areas where the artifact was located, without negatively affecting areas distal to the artifact. The performance of the filter was also found to be consistent across all six of the data sets evaluated. The evaluation of the detection criterion parameter M determined that a value of M = 3 achieves a conservative filter with minimal loss of spatial resolution during the process. Conclusions: The filter was able to remove most artifacts due to the presence of moving air bubbles in the rectum during transurethral MR-HIFU. A quantitative estimation of the filter capabilities shows a systematic improvement in the standard deviation of the corrected temperature maps in the rectum zone as well as in the entire acquired slice. C

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Twelve-month prostate volume reduction after MRI-guided transurethral ultrasound ablation of the prostate

et al. 2018

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• MRI-guided transurethral ultrasound ablation (TULSA) achieved an 88% reduction of viable prostate tissue volume at 12 months, in excellent agreement with expectation from thermal dose calculations. • Non-perfused volume on immediate post-treatment contrast-enhanced MRI represents only 64% of the acute thermal ablation volume (ATAV), and reports only 60% (53% instead of 88% achieved) of the reduction in viable prostate tissue volume at 12 months. • MR-thermometry-based predictions of 12-month prostate volume reduction based on 240 cumulative equivalent minute thermal dose volume are in excellent agreement with reduction in viable prostate tissue volume measured on pre- and 12-month post-treatment T2w-MRI.

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3D conformal MRI-controlled transurethral ultrasound prostate therapy: validation of numerical simulations and demonstration in tissue-mimicking gel phantoms

Cited by 20 publications

References 48 publications

Coagulation of human prostate volumes with MRI-controlled transurethral ultrasound therapy: Results in gel phantoms

Coagulation of human prostate volumes with MRI-controlled transurethral ultrasound therapy: Results in gel phantoms

Spatiotemporal filtering of MR‐temperature artifacts arising from bowel motion during transurethral MR‐HIFU

Twelve-month prostate volume reduction after MRI-guided transurethral ultrasound ablation of the prostate

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