Thermal ablation by high-intensity-focused ultrasound using a toroid transducer increases the coagulated volume. Results of animal experiments.

Surgical resection is the only treatment of colorectal liver metastases that can ensure long-term survival and cure in some patients. However, only 20% of patients are suitable for surgery. As a result, many nonresectional modalities of treatment have been assessed to provide an alternative to liver resection. Several limitations have been observed when using these techniques and available evidence is limited. Here, we report that a new design of high intensity focused ultrasound transducer can significantly enlarge the coagulated volume over short periods of time and that treatment in the liver can be guided in real-time using an integrated ultrasound imaging probe. Our long-term objective is to develop a device that can be used during surgery for eventual clinical use in conjunction with resection. Eight ultrasound emitters, divided into 256 elements, were created by sectioning a single toroid piezocomposite transducer. The focal zone was conical in shape and located 70 mm from the transducer; enabling the treatment of deep-seated tumors. A single thermal lesion was created when the eight emitters performed alternative and consecutive 5-s ultrasound exposures. This article presents in vivo evidence that the coagulated volume obtained from a 40 s total exposure in the liver was 7.0 +/- 2.5 cm(3) (minimum 1.5 - maximum 20.0 cm(3)) with an average diameter of 17.5 +/- 3.8 mm (minimum 10.0 - maximum 29.0 mm). All lesions were visible with high contrast on sonograms. The correlation between the diameter of lesions observed on sonograms and during gross examination was 92%. This method also allowed the user to easily enlarge the coagulated volume by juxtaposing single lesions. This approach may have a role in treating unresectable colorectal liver metastases and may also be used in conjunction with resection to extend its limits.

High-intensity focused ultrasound ablation for the treatment of colorectal liver metastases during an open procedure: study on the pig.

OBJECTIVE: To demonstrate in a porcine model that high-intensity focused ultrasound (HIFU) with toroid-shaped emitters may have a role in treating unresectable colorectal liver metastases. SUMMARY BACKGROUND DATA: Surgical resection is the only curative option for colorectal hepatic metastases. Only 20% of patients are suitable for surgery. Many ablative techniques have been assessed but several limitations have been documented: traumatic puncture of the parenchyma, limited size of lesions, and inability to monitor the treatment in real time. METHODS: A HIFU device with 256 toroid-shaped emitters and integrated ultrasound imaging probe was used. Single lesions, induced in 40 seconds, and juxtaposition of 6 single lesions were created under ultrasound guidance on 13 pigs. The lesions were studied on sonograms, macroscopically and microscopically up to 30 days after the treatment. RESULTS: Ninety percent of the HIFU lesions were immediately hypoechoic on ultrasound imaging. The average coagulated volume obtained from a 40 seconds total exposure in the liver was 7.0 +/- 2.5 cm (1.5-20.0), average diameter: 19.5 +/- 3.8 mm (10.0-29.0). Using the real-time visualization of the treated region, single lesions were easily juxtaposed to produce larger lesions up to 6 cm in diameter without any major complication. CONCLUSIONS: This toroid HIFU device allows short treatment times, noninvasiveness regarding the liver and real time ultrasound guidance. It seems to be simpler and more reliable to use than current ablative methods. Additionally, lesions through large vessels (up to 5 mm) being feasible, treatment of some juxta-vascular metastases should be possible.

Utility of a tumor-mimic model for the evaluation of the accuracy of HIFU treatments. results of in vitro experiments in the liver.

Presented in this article is a tumor-mimic model that allows the evaluation, before clinical trials, of the targeting accuracy of a high intensity focused ultrasound (HIFU) device for the treatment of the liver. The tumor-mimic models are made by injecting a warm solution that polymerizes in hepatic tissue and forms a 1 cm discrete lesion that is detectable by ultrasound imaging and gross pathology. First, the acoustical characteristics of the tumor-mimics model were measured in order to determine if this model could be used as a target for the evaluation of the accuracy of HIFU treatments without modifying HIFU lesions in terms of size, shape and homogeneity. On average (n = 10), the attenuation was 0.39 +/- 0.05 dB.cm(-1) at 1 MHz, the ultrasound propagation velocity was 1523 +/- 1 m.s(-1) and the acoustic impedance was 1.84 +/- 0.00 MRayls. Next, the tumor-mimic models were used in vitro in order to verify, at a preclinical stage, that lesions created by HIFU devices guided by ultrasound imaging are properly positioned in tissues. The HIFU device used in this study is a 256-element phased-array toroid transducer working at a frequency of 3 MHz with an integrated ultrasound imaging probe working at a frequency of 7.5 MHz. An initial series of in vitro experiments has shown that there is no significant difference in the dimensions of the HIFU lesions created in the liver with or without tumor-mimic models (p = 0.3049 and p = 0.8796 for the diameter and depth, respectively). A second in vitro study showed that HIFU treatments performed on five tumor-mimics with safety margins of at least 1 mm were properly positioned. The margins obtained were on average 9.3 +/- 2.7 mm (min. 3.0 - max. 20.0 mm). This article presents in vitro evidence that these tumor-mimics are identifiable by ultrasound imaging, they do not modify the geometry of HIFU lesions and, thus, they constitute a viable model of tumor-mimics indicated for HIFU therapy.

Toric HIFU transducer for large thermal ablation.

A new geometry of High Intensity Focused Ultrasound (HIFU) transducer is described to enlarge the coagulated volume and decrease treatments time. Eight transducer elements and their quarter-wave plate were diced out of a single toric piezocomposite element. Each transducer operates at a frequency of 3 MHz. The focal zone is conic and located at 70 mm from the transducer. A 7.5 MHz ultrasound imaging probe is placed in the centre of the device for guiding the treatment. Optimal exposure parameters were determined from numerical simulations. This new geometry allows achieving a thermal ablation of 7.5 cm3 when each of the eight transducers has performed a 5-s ultrasound exposure alternatively and consecutively. In vivo trials have been performed on five pigs to demonstrate this new principle. 33 elementary lesions have been performed. All lesions were reproducible and homogeneous. The average diameter of an elementary lesion obtained in 40 seconds was 19.5 +/- 3.8 mm (min 10 - max 29 mm). The coagulated volume obtained in 40 seconds was on average 9.1 +/- 4.6 cm3 (min 1.5 - max 17.6 cm3).

Frequency of anal incontinence and results of pelvic viscerography in 291 women with pelvic organ prolapse.

OBJECTIVES: To determine the prevalence of anal incontinence in a population of 291 women with pelvic organ prolapse and evaluate the results of pelvic viscerogram in this situation. MATERIALS AND METHODS: Each patient answered a standardized questionnaire on medical, obstetric and surgical past histories and answers were logged in a database. The viscerograms were performed by a single specialized radiologist. RESULTS: All patients but one were parous. The prevalence of anal incontinence was 26.1%. Stress urinary incontinence and urge urinary incontinence were significantly associated with anal incontinence. No obstetric or surgical risk factor for anal incontinence was demonstrated. Viscerography demonstrated rectoceles (n=86, 29.1%), enteroceles (n=77, 26.5%), cystoceles (n=174, 59.8%), and intra-anal rectal prolapse (n=106, 36.4%). A significant association was found between intra-anal rectal prolapse and anal incontinence. CONCLUSION: Anal incontinence is frequent in patients with pelvic organ prolapse, even more so in the presence of urinary incontinence, and should be investigated by pelvic viscerography. Pelvic floor dysfunction is frequently associated with enteroceles, rectoceles and rectal prolapse. Pelvic viscerograms should be systematically performed in the diagnostic work-up in patients with pelvic organ prolapse when surgical treatment is considered.