Jean-Yves Chapelon - Academia.edu (original) (raw)

Papers by Jean-Yves Chapelon

Journal of Clinical Oncology, 2016

102 Background: Up to a third of patients with localized prostate cancer (LPCa) have unilateral d... more 102 Background: Up to a third of patients with localized prostate cancer (LPCa) have unilateral disease that may be suitable for a treatment of one lobe. Our aim was to evaluate the ability of HIFU to achieve a local control of the tumor in patients with unilateral LPCa. Methods: The French Urological Association (AFU) conducted a multi-institutional study, to evaluate hemi-ablation with HIFU as a primary treatment for patients >50 years, T1C or T2A, PSA<10ng/ml, Gleason ≤7 (3+4), and unilateral disease. 111 patients were treated: mean age 64.8 ±6.18 years, mean PSA 6.23±2.5 ng/ml. Gleason sum was ≤6 in 73.9% and 7 in 26.1%.primary outcome was the negative biopsy rate. Secondary outcomes were genitourinary side effects measured using validated questionnaires. The tumor was localized using MRI followed by random and targeted transrectal biopsies. Only the pathological prostate lobe was treated using HIFU. Results: The PSA nadir value was 1.87±1.49 ng/ml and the PSA at 12 months...

Ultrasound in Medicine & Biology, 2008

The present study proposes a new integrated imaging (II) high-intensity focused ultrasound (HIFU)... more The present study proposes a new integrated imaging (II) high-intensity focused ultrasound (HIFU) probe intended as an improvement to the Ablatherm™ prostate cancer treatment. Because of a perforation in the center of the II probe, the expected lesion differs from the one obtained for the original Ablatherm™ probe. In this paper, the new geometry and the strategy followed to establish the treatment parameters are presented. The original probe has a 40-mm focal length, a 50-mm aperture and is truncated at 31 mm. The II probe has a 45-mm focal length, a 61-mm aperture, a central perforation of 25 mm and is truncated at 31 mm. Both probes operate at 3 MHz. A mathematical model for lesion prediction was used for setting the treatment parameters for the II probe. These parameters should ensure equivalence between the lesions obtained with the original and II probes. Simulation-obtained parameters were validated by in-vitro and in-vivo (on liver of 70 New Zealand rabbits) experiments. The new II probe was used clinically to treat 30 patients. The mean age was 70.9 ؎ 5.3 years (SD), the mean prostate volume 26.9 ؎ 7.7 mL and the mean serum prostate specific antigen (PSA) concentration before treatment was 9.2 ؎ 5.5 ng/mL. Simulations showed that for the II probe acoustical power and duration when the transducer is inactive should be reduced of 14% and 1s. In-vitro and in-vivo experiments confirmed the equivalence between the lesions obtained with the two probes. The lesion volume obtained under in-vitro conditions (for a traversed tissue depth of 16 mm to the focus) was 5 ؎ 0.4 cm 3 and 5.1 ؎ 0.5 cm 3 for the original and II probes, respectively. Under in-vivo conditions, the lesion volume (for a traversed tissue depth of 18 mm) was 5.3 ؎ 1.1 cm 3 and 5.1 ؎ 1.1 cm 3 for the original and II probes, respectively. During the clinical trial, a correction of ؉ 1s in the exposure time was required to recreate the same degree of efficacy observed with the original probe (p ‫؍‬ 0.97): 66.7 % of negative biopsies and 75% of patients with PSA at 3 mo <1 ng/mL. The morbidity observed was minimal and identical to that observed with the original probe.

The Journal of Urology, 2014

IRBM, 2009

Communication brève Développement d'un dispositif expérimental ultrasonore pour le largage ciblé ... more Communication brève Développement d'un dispositif expérimental ultrasonore pour le largage ciblé et contrôlé d'une chimiothérapie encapsulée Design and test of an ultrasonic experimental setup for controlled delivery of encapsulated chemotherapy

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2002

Current Opinion in Urology, 2009

To outline the current status of high-intensity focused ultrasound (HIFU) for the treatment of re... more To outline the current status of high-intensity focused ultrasound (HIFU) for the treatment of renal tumors. Application of extracorporeal HIFU for renal tumors is well tolerated with no serious perioperative complications. However, the techniques available do not permit sufficient tumor destruction that can be considered as an alternative to surgical extirpation. Laparoscopic HIFU avoids problems with respiratory movement and interphases and may achieve a greater rate of tumor destruction. At the current time, HIFU of renal tumors has to be considered an experimental treatment approach. Prospective evaluation of laparoscopic HIFU is necessary to evaluate its oncologic efficacy.

Applied Physics Letters, 2013

We present an approach to extract from the local measurement of a complex field a wavelength tomo... more We present an approach to extract from the local measurement of a complex field a wavelength tomography. In contrast with noise correlation techniques developed in recent years in seismology or ultrasound, field measurement is under-sampled which opens applications to slow imaging devices. Through simulations and experiments, it is demonstrated that the loss of time and/or spatial coherence of the field measurement is not an obstacle for tomography reconstruction. We present an application in shear wave imaging: a conventional ultrasonic scanner working at 25 Hz is tested in a medical phantom and in the thyroid of a healthy volunteer.

AIP Conference Proceedings, 2017

AlN-based piezoelectric micromachined ultrasonic transducer for photoacoustic imaging

Computers in Biology and Medicine, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Clinical Oncology, 2017

77 Background: In the field of curative treatment for localized prostate cancer, HIFU (High Inten... more 77 Background: In the field of curative treatment for localized prostate cancer, HIFU (High Intensity Focused ultrasound) is one of salvage option after EBRT(external beam radiation therapy) failure and EBRT is the standard salvage option for local relapse after HIFU.Our aim was to compare and evaluate the oncologic outcomes between HIFU first + salvage EBRT versus EBRT first +salvage HIFU. Methods: Using a matched pair analysis, 342 Patients (171 in each group) treated between 1994 and 2014 in the same institution were prospectively followed and matched to a 1:1 basis. Outcome measurements: Overall Survival Rate(OSR), cancer specific(CSSR) and metastasis free (MFSR) survival rates were the primary endpoints. Secondary endpoints were survival rate free of hormone therapy (HTFR) and the rate of side effects Clavien score ≥ 3. Results: Mean follow-up were 114 and 124 months for HIFU+ S-EBRT and EBRT + S-HIFU respectively. At 7 years from the primary treatment , the MFSR were significa...

Journal of Therapeutic Ultrasound, 2015

British Journal of Cancer, 1993

Cavitation (volume oscillations and collapse of gas bubbles), as generated by a co-administration... more Cavitation (volume oscillations and collapse of gas bubbles), as generated by a co-administration of shockwaves (SW) and microbubbles (SWB), induces cytotoxicity in vitro. Moreover, cavitation potentiates the effects of Fluorouracil (FUra) on colon cancer cells. We aimed at reproducing such effects in vivo. A peritoneal carcinomatosis was induced in BDIX rats by intraperitoneal (IP) injection of DHDK12PROb cells. Cavitation was produced by various SW regimens (250 to 750SW) combined with bubbles (air/gelatin emulsion) infused through an IP catheter. In two consecutive experiments, microtumours (day 3 after cell injection) were submitted to various combinations of cavitation and/or Fluorouracil (FUra) and Cisplatinum (CDDP) at either high or low doses. After 30 days, 100% of control animals were dead or presented carcinomatosis with ascites, vs 60% after FUra 5 mg kg dy, day 4 through 8, and 0% after 250 SWB, day 4 and 6 + FUra 5 mg kg dy, day 4 through 8 (P<0.001); similar differences were found with CDDP. Survival after low dose FUra + SWB was comparable to high dose FUra (25 mg kg dy day 4 through 8) and was improved as compared to low-dose FUra alone. Only a high dose FUra + SWB schedule induced 40% long term (> 150 days) disease-free survival, but also a higher undesirable toxicity (40% toxic deaths within 1 month). It is concluded that cavitation is cytotoxic in vivo and that it potentiates the effects of FUra and CDDP in this animal model.

Journal of the Acoustical Society of America, 2015

The objective of this clinical study was to validate the effectiveness, accuracy, tolerance, and ... more The objective of this clinical study was to validate the effectiveness, accuracy, tolerance, and safety of a HIFU treatment developed for the treatment of liver metastases in a prospective, phase I-II trial. The transducer has a toroidal shape (diameter: 70 mm, radius of curvature: 70 mm) and was divided into 32 ring-shaped emitters operating at 3 MHz. HIFU was delivered immediately before scheduled hepatectomy. Ablations were performed on healthy tissue within the areas scheduled for resection. First, 30 ablations were carried out in 15 patients. These ablations were all generated within 40 seconds and on average measured 27.5 × 21.0 mm2. The phase I study (n = 6) showed that use of the HIFU device was feasible and safe and did not damage neighboring tissue. The phase IIa study (n = 9) showed that the area of ablation could be precisely targeted on a previously implanted metallic mark. Ablations were achieved with a precision of 1–2 mm. The phase IIb study (n = 10) demonstrated abl...

2002 IEEE Ultrasonics Symposium, 2002. Proceedings.

ABSTRACT

1996 IEEE Ultrasonics Symposium. Proceedings

ABSTRACT

2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006

A new high intensity focused ultrasound (HIFU) probe has been designed and tested by using MRI. T... more A new high intensity focused ultrasound (HIFU) probe has been designed and tested by using MRI. The probe is intended to be used by physicians to correct valvular dysfunction in the saphenous vein, which is known to be the cause of superficial venous insufficiency (SVI) and varicose veins. Treating SVI with HIFU is possible, since venous tissue undergoes localized partial shrinkage when subjected to HIFU. In vitro experiments have demonstrated that diameter shrinkage should be sufficient to restore valvular function, as is done in the more aggressive approach known as external valvuloplasty. Numerical simulations and optimization have led to a probe design with two HIFU elements that focus sound uniformly over a line of length 7 mm, at a depth of 15 mm from the skin. A prototype of the probe has been constructed, with a holder that provides space for an MRI-imaging antenna. The probe has been tested by measuring pressure and temperature fields. Results are in good agreement with those predicted by an analytical approach and numerical simulations.

Ultrasonics, 2004

Vibro-acoustography technique known by its noncontact excitation was used to detect resonance fre... more Vibro-acoustography technique known by its noncontact excitation was used to detect resonance frequencies of objects in water. Two intersecting ultrasound beams generated by a 40 mm-diameter annular array transducer, focused at 35 mm and driven at f 1 ¼ 2:2 MHz and f 2 ¼ 2:22 MHz respectively, were targeted inside the object under test to produce a radiation force beating at the difference frequency f 2 À f 1. This low frequency radiation force was used to excite the resonance vibration modes of the object by sweeping the frequency f 2 between 2.22 and 2.275 MHz. The amplitude of the acoustic emission produced by the vibrations of the object was detected by a low frequency hydrophone (BW ¼ 60 kHz). By this approach, it was possible to detect resonance frequencies through amplitude variations of the measured acoustic emission. Experiments were conducted in a water tank for objects of different shapes and sizes. With a chalk sphere (15 mm-diameter) two resonance frequencies were detected at 45.75 and 68.75 kHz, and with a cylinder (10.38 mm-diameter and 32.20 mm-length) four principal resonance frequencies were identified in the 60 kHzbandwidth of the hydrophone. It was shown with finite element calculations performed with Ansys, in which both solid and fluid parts were modelled, that the measured resonance frequencies corresponded to compressional or dilatation vibration modes of the object. It was verified that shear waves generated by torsional vibration modes were not propagated in water, as it is well known. The use of this technique to characterize heterogeneities in different media seems to be relatively more advantageous to other ultrasonic methods.

Magnetic Resonance in Medicine, 2011

We investigated a technique based on phase‐contrast cine MRI combined with deconvolution of the p... more We investigated a technique based on phase‐contrast cine MRI combined with deconvolution of the phase shift waveforms to measure rapidly varying pulsatile motion waveforms. The technique does not require steady‐state displacement during motion encoding. Simulations and experiments were performed in porcine liver samples in view of a specific application, namely the observation of transient displacements induced by acoustic radiation force. Simulations illustrate the advantages and shortcomings of the methods. For experimental validation, the waveforms were acquired with an ultrafast ultrasound scanner (Supersonic Imagine Aixplorer), and the rates of decay of the waveforms (relaxation time) were compared. With bipolar motion‐encoding gradient of 8.4 ms, the method was able to measure displacement waveforms with a temporal resolution of 1 ms over a time course of 40 ms. Reasonable agreement was found between the rate of decay of the waveforms measured in ultrasound (2.8 ms) and in MRI...

Actas Urológicas Españolas, 2010

Objetivos: Es conocida la aplicació n de los ultrasonidos focalizados de alta intensidad (HIFU) e... more Objetivos: Es conocida la aplicació n de los ultrasonidos focalizados de alta intensidad (HIFU) en el tratamiento de los tumores só lidos dentro de las terapias mínimamente invasivas, habié ndose desarrollado en los ú ltimos añ os transductores que permiten la aplicació n de ultrasonidos desde un foco extracorpó reo. Presentamos una revisió n del desarrollo, los principios físicos, el estado actual y la experiencia inicial propia de esta terapia en el tratamiento de los tumores renales. Material y métodos: Actualmente el HIFU extracorpó reo está siendo utilizado en el tratamiento de tumores, principalmente hepá ticos, ginecoló gicos y ó seos, y se ha iniciado su uso en la terapia para las neoplasias renales con buenos resultados. Presentamos una revisió n bibliográ fica (bú squeda estructurada en la base electró nica MEDLINE online) de los principios físicos de este tratamiento y su acció n bioló gica. Describimos la metodología de tratamiento de los primeros casos de carcinoma renal tratados en nuestro hospital con é xito mediante HIFU. Resultados: Esta terapia ha sido empleada con é xito para tratar tumores só lidos en varios centros de Europa, Amé rica y Asia. En nuestro centro tenemos una amplia experiencia en el tratamiento mediante HIFU extracorpó reo de tumores ginecoló gicos, y ya hemos tratado tumores renales sin complicaciones, si bien el seguimiento es todavía corto. Conclusiones: El uso de esta energía de forma extracorpó rea aparece como una nueva opció n dentro de las terapias no invasivas del cá ncer renal en casos seleccionados, con un escaso índice de complicaciones, aunque hace falta mucho má s tiempo de seguimiento para valorar sus resultados desde el punto de vista oncoló gico.

Journal of therapeutic ultrasound, Mar 17, 2017

When exposed to sufficiently high ultrasound pressures, microbubbles can be generated spontaneous... more When exposed to sufficiently high ultrasound pressures, microbubbles can be generated spontaneously in tissue and undergo inertial cavitation where collapses result in physical effects. These effects range from petechial haemorrhage to complete cellular disruption, termed Histotripsy, depending on ultrasound parameters. This presentation will explore the mechanisms associated with histotripsy along with the tissue effects and the wide range of potential applications for this mechanical disruption method.

Journal of Clinical Oncology, 2016

102 Background: Up to a third of patients with localized prostate cancer (LPCa) have unilateral d... more 102 Background: Up to a third of patients with localized prostate cancer (LPCa) have unilateral disease that may be suitable for a treatment of one lobe. Our aim was to evaluate the ability of HIFU to achieve a local control of the tumor in patients with unilateral LPCa. Methods: The French Urological Association (AFU) conducted a multi-institutional study, to evaluate hemi-ablation with HIFU as a primary treatment for patients >50 years, T1C or T2A, PSA<10ng/ml, Gleason ≤7 (3+4), and unilateral disease. 111 patients were treated: mean age 64.8 ±6.18 years, mean PSA 6.23±2.5 ng/ml. Gleason sum was ≤6 in 73.9% and 7 in 26.1%.primary outcome was the negative biopsy rate. Secondary outcomes were genitourinary side effects measured using validated questionnaires. The tumor was localized using MRI followed by random and targeted transrectal biopsies. Only the pathological prostate lobe was treated using HIFU. Results: The PSA nadir value was 1.87±1.49 ng/ml and the PSA at 12 months...

Ultrasound in Medicine & Biology, 2008

The present study proposes a new integrated imaging (II) high-intensity focused ultrasound (HIFU)... more The present study proposes a new integrated imaging (II) high-intensity focused ultrasound (HIFU) probe intended as an improvement to the Ablatherm™ prostate cancer treatment. Because of a perforation in the center of the II probe, the expected lesion differs from the one obtained for the original Ablatherm™ probe. In this paper, the new geometry and the strategy followed to establish the treatment parameters are presented. The original probe has a 40-mm focal length, a 50-mm aperture and is truncated at 31 mm. The II probe has a 45-mm focal length, a 61-mm aperture, a central perforation of 25 mm and is truncated at 31 mm. Both probes operate at 3 MHz. A mathematical model for lesion prediction was used for setting the treatment parameters for the II probe. These parameters should ensure equivalence between the lesions obtained with the original and II probes. Simulation-obtained parameters were validated by in-vitro and in-vivo (on liver of 70 New Zealand rabbits) experiments. The new II probe was used clinically to treat 30 patients. The mean age was 70.9 ؎ 5.3 years (SD), the mean prostate volume 26.9 ؎ 7.7 mL and the mean serum prostate specific antigen (PSA) concentration before treatment was 9.2 ؎ 5.5 ng/mL. Simulations showed that for the II probe acoustical power and duration when the transducer is inactive should be reduced of 14% and 1s. In-vitro and in-vivo experiments confirmed the equivalence between the lesions obtained with the two probes. The lesion volume obtained under in-vitro conditions (for a traversed tissue depth of 16 mm to the focus) was 5 ؎ 0.4 cm 3 and 5.1 ؎ 0.5 cm 3 for the original and II probes, respectively. Under in-vivo conditions, the lesion volume (for a traversed tissue depth of 18 mm) was 5.3 ؎ 1.1 cm 3 and 5.1 ؎ 1.1 cm 3 for the original and II probes, respectively. During the clinical trial, a correction of ؉ 1s in the exposure time was required to recreate the same degree of efficacy observed with the original probe (p ‫؍‬ 0.97): 66.7 % of negative biopsies and 75% of patients with PSA at 3 mo <1 ng/mL. The morbidity observed was minimal and identical to that observed with the original probe.

The Journal of Urology, 2014

IRBM, 2009

Communication brève Développement d'un dispositif expérimental ultrasonore pour le largage ciblé ... more Communication brève Développement d'un dispositif expérimental ultrasonore pour le largage ciblé et contrôlé d'une chimiothérapie encapsulée Design and test of an ultrasonic experimental setup for controlled delivery of encapsulated chemotherapy

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2002

Current Opinion in Urology, 2009

To outline the current status of high-intensity focused ultrasound (HIFU) for the treatment of re... more To outline the current status of high-intensity focused ultrasound (HIFU) for the treatment of renal tumors. Application of extracorporeal HIFU for renal tumors is well tolerated with no serious perioperative complications. However, the techniques available do not permit sufficient tumor destruction that can be considered as an alternative to surgical extirpation. Laparoscopic HIFU avoids problems with respiratory movement and interphases and may achieve a greater rate of tumor destruction. At the current time, HIFU of renal tumors has to be considered an experimental treatment approach. Prospective evaluation of laparoscopic HIFU is necessary to evaluate its oncologic efficacy.

Applied Physics Letters, 2013

We present an approach to extract from the local measurement of a complex field a wavelength tomo... more We present an approach to extract from the local measurement of a complex field a wavelength tomography. In contrast with noise correlation techniques developed in recent years in seismology or ultrasound, field measurement is under-sampled which opens applications to slow imaging devices. Through simulations and experiments, it is demonstrated that the loss of time and/or spatial coherence of the field measurement is not an obstacle for tomography reconstruction. We present an application in shear wave imaging: a conventional ultrasonic scanner working at 25 Hz is tested in a medical phantom and in the thyroid of a healthy volunteer.

AIP Conference Proceedings, 2017

AlN-based piezoelectric micromachined ultrasonic transducer for photoacoustic imaging

Computers in Biology and Medicine, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of Clinical Oncology, 2017

77 Background: In the field of curative treatment for localized prostate cancer, HIFU (High Inten... more 77 Background: In the field of curative treatment for localized prostate cancer, HIFU (High Intensity Focused ultrasound) is one of salvage option after EBRT(external beam radiation therapy) failure and EBRT is the standard salvage option for local relapse after HIFU.Our aim was to compare and evaluate the oncologic outcomes between HIFU first + salvage EBRT versus EBRT first +salvage HIFU. Methods: Using a matched pair analysis, 342 Patients (171 in each group) treated between 1994 and 2014 in the same institution were prospectively followed and matched to a 1:1 basis. Outcome measurements: Overall Survival Rate(OSR), cancer specific(CSSR) and metastasis free (MFSR) survival rates were the primary endpoints. Secondary endpoints were survival rate free of hormone therapy (HTFR) and the rate of side effects Clavien score ≥ 3. Results: Mean follow-up were 114 and 124 months for HIFU+ S-EBRT and EBRT + S-HIFU respectively. At 7 years from the primary treatment , the MFSR were significa...

Journal of Therapeutic Ultrasound, 2015

British Journal of Cancer, 1993

Cavitation (volume oscillations and collapse of gas bubbles), as generated by a co-administration... more Cavitation (volume oscillations and collapse of gas bubbles), as generated by a co-administration of shockwaves (SW) and microbubbles (SWB), induces cytotoxicity in vitro. Moreover, cavitation potentiates the effects of Fluorouracil (FUra) on colon cancer cells. We aimed at reproducing such effects in vivo. A peritoneal carcinomatosis was induced in BDIX rats by intraperitoneal (IP) injection of DHDK12PROb cells. Cavitation was produced by various SW regimens (250 to 750SW) combined with bubbles (air/gelatin emulsion) infused through an IP catheter. In two consecutive experiments, microtumours (day 3 after cell injection) were submitted to various combinations of cavitation and/or Fluorouracil (FUra) and Cisplatinum (CDDP) at either high or low doses. After 30 days, 100% of control animals were dead or presented carcinomatosis with ascites, vs 60% after FUra 5 mg kg dy, day 4 through 8, and 0% after 250 SWB, day 4 and 6 + FUra 5 mg kg dy, day 4 through 8 (P<0.001); similar differences were found with CDDP. Survival after low dose FUra + SWB was comparable to high dose FUra (25 mg kg dy day 4 through 8) and was improved as compared to low-dose FUra alone. Only a high dose FUra + SWB schedule induced 40% long term (> 150 days) disease-free survival, but also a higher undesirable toxicity (40% toxic deaths within 1 month). It is concluded that cavitation is cytotoxic in vivo and that it potentiates the effects of FUra and CDDP in this animal model.

Journal of the Acoustical Society of America, 2015

The objective of this clinical study was to validate the effectiveness, accuracy, tolerance, and ... more The objective of this clinical study was to validate the effectiveness, accuracy, tolerance, and safety of a HIFU treatment developed for the treatment of liver metastases in a prospective, phase I-II trial. The transducer has a toroidal shape (diameter: 70 mm, radius of curvature: 70 mm) and was divided into 32 ring-shaped emitters operating at 3 MHz. HIFU was delivered immediately before scheduled hepatectomy. Ablations were performed on healthy tissue within the areas scheduled for resection. First, 30 ablations were carried out in 15 patients. These ablations were all generated within 40 seconds and on average measured 27.5 × 21.0 mm2. The phase I study (n = 6) showed that use of the HIFU device was feasible and safe and did not damage neighboring tissue. The phase IIa study (n = 9) showed that the area of ablation could be precisely targeted on a previously implanted metallic mark. Ablations were achieved with a precision of 1–2 mm. The phase IIb study (n = 10) demonstrated abl...

2002 IEEE Ultrasonics Symposium, 2002. Proceedings.

ABSTRACT

1996 IEEE Ultrasonics Symposium. Proceedings

ABSTRACT

2006 International Conference of the IEEE Engineering in Medicine and Biology Society, 2006

A new high intensity focused ultrasound (HIFU) probe has been designed and tested by using MRI. T... more A new high intensity focused ultrasound (HIFU) probe has been designed and tested by using MRI. The probe is intended to be used by physicians to correct valvular dysfunction in the saphenous vein, which is known to be the cause of superficial venous insufficiency (SVI) and varicose veins. Treating SVI with HIFU is possible, since venous tissue undergoes localized partial shrinkage when subjected to HIFU. In vitro experiments have demonstrated that diameter shrinkage should be sufficient to restore valvular function, as is done in the more aggressive approach known as external valvuloplasty. Numerical simulations and optimization have led to a probe design with two HIFU elements that focus sound uniformly over a line of length 7 mm, at a depth of 15 mm from the skin. A prototype of the probe has been constructed, with a holder that provides space for an MRI-imaging antenna. The probe has been tested by measuring pressure and temperature fields. Results are in good agreement with those predicted by an analytical approach and numerical simulations.

Ultrasonics, 2004

Vibro-acoustography technique known by its noncontact excitation was used to detect resonance fre... more Vibro-acoustography technique known by its noncontact excitation was used to detect resonance frequencies of objects in water. Two intersecting ultrasound beams generated by a 40 mm-diameter annular array transducer, focused at 35 mm and driven at f 1 ¼ 2:2 MHz and f 2 ¼ 2:22 MHz respectively, were targeted inside the object under test to produce a radiation force beating at the difference frequency f 2 À f 1. This low frequency radiation force was used to excite the resonance vibration modes of the object by sweeping the frequency f 2 between 2.22 and 2.275 MHz. The amplitude of the acoustic emission produced by the vibrations of the object was detected by a low frequency hydrophone (BW ¼ 60 kHz). By this approach, it was possible to detect resonance frequencies through amplitude variations of the measured acoustic emission. Experiments were conducted in a water tank for objects of different shapes and sizes. With a chalk sphere (15 mm-diameter) two resonance frequencies were detected at 45.75 and 68.75 kHz, and with a cylinder (10.38 mm-diameter and 32.20 mm-length) four principal resonance frequencies were identified in the 60 kHzbandwidth of the hydrophone. It was shown with finite element calculations performed with Ansys, in which both solid and fluid parts were modelled, that the measured resonance frequencies corresponded to compressional or dilatation vibration modes of the object. It was verified that shear waves generated by torsional vibration modes were not propagated in water, as it is well known. The use of this technique to characterize heterogeneities in different media seems to be relatively more advantageous to other ultrasonic methods.

Magnetic Resonance in Medicine, 2011

We investigated a technique based on phase‐contrast cine MRI combined with deconvolution of the p... more We investigated a technique based on phase‐contrast cine MRI combined with deconvolution of the phase shift waveforms to measure rapidly varying pulsatile motion waveforms. The technique does not require steady‐state displacement during motion encoding. Simulations and experiments were performed in porcine liver samples in view of a specific application, namely the observation of transient displacements induced by acoustic radiation force. Simulations illustrate the advantages and shortcomings of the methods. For experimental validation, the waveforms were acquired with an ultrafast ultrasound scanner (Supersonic Imagine Aixplorer), and the rates of decay of the waveforms (relaxation time) were compared. With bipolar motion‐encoding gradient of 8.4 ms, the method was able to measure displacement waveforms with a temporal resolution of 1 ms over a time course of 40 ms. Reasonable agreement was found between the rate of decay of the waveforms measured in ultrasound (2.8 ms) and in MRI...

Actas Urológicas Españolas, 2010

Objetivos: Es conocida la aplicació n de los ultrasonidos focalizados de alta intensidad (HIFU) e... more Objetivos: Es conocida la aplicació n de los ultrasonidos focalizados de alta intensidad (HIFU) en el tratamiento de los tumores só lidos dentro de las terapias mínimamente invasivas, habié ndose desarrollado en los ú ltimos añ os transductores que permiten la aplicació n de ultrasonidos desde un foco extracorpó reo. Presentamos una revisió n del desarrollo, los principios físicos, el estado actual y la experiencia inicial propia de esta terapia en el tratamiento de los tumores renales. Material y métodos: Actualmente el HIFU extracorpó reo está siendo utilizado en el tratamiento de tumores, principalmente hepá ticos, ginecoló gicos y ó seos, y se ha iniciado su uso en la terapia para las neoplasias renales con buenos resultados. Presentamos una revisió n bibliográ fica (bú squeda estructurada en la base electró nica MEDLINE online) de los principios físicos de este tratamiento y su acció n bioló gica. Describimos la metodología de tratamiento de los primeros casos de carcinoma renal tratados en nuestro hospital con é xito mediante HIFU. Resultados: Esta terapia ha sido empleada con é xito para tratar tumores só lidos en varios centros de Europa, Amé rica y Asia. En nuestro centro tenemos una amplia experiencia en el tratamiento mediante HIFU extracorpó reo de tumores ginecoló gicos, y ya hemos tratado tumores renales sin complicaciones, si bien el seguimiento es todavía corto. Conclusiones: El uso de esta energía de forma extracorpó rea aparece como una nueva opció n dentro de las terapias no invasivas del cá ncer renal en casos seleccionados, con un escaso índice de complicaciones, aunque hace falta mucho má s tiempo de seguimiento para valorar sus resultados desde el punto de vista oncoló gico.

Journal of therapeutic ultrasound, Mar 17, 2017

When exposed to sufficiently high ultrasound pressures, microbubbles can be generated spontaneous... more When exposed to sufficiently high ultrasound pressures, microbubbles can be generated spontaneously in tissue and undergo inertial cavitation where collapses result in physical effects. These effects range from petechial haemorrhage to complete cellular disruption, termed Histotripsy, depending on ultrasound parameters. This presentation will explore the mechanisms associated with histotripsy along with the tissue effects and the wide range of potential applications for this mechanical disruption method.