MRI-guided Focused Ultrasound Surgery Research Articles

Status and treatment of patients with uterine fibroids in hospitals in central China: a retrospective study from 2018 to 2021

ObjectiveTo evaluate the hospitalised patients with uterine fibroids (UFs) and describe treatment patterns in hospital-treated patients in central China from 2018 to 2021.DesignA retrospective analysis.SettingThe gynaecology departments of class A...

MRI-guided focused ultrasound surgery in musculoskeletal diseases: the hot topics.

MRI-guided focused ultrasound surgery (MRgFUS) is a minimally invasive treatment guided by the most sophisticated imaging tool available in today's clinical practice. Both the imaging and therapeutic sides of the equipment are based on non-ionizing energy. This technique is a very promising option as potential treatment for several pathologies, including musculoskeletal (MSK) disorders. Apart from clinical applications, MRgFUS technology is the result of long, heavy and cumulative efforts exploring the effects of ultrasound on biological tissues and function, the generation of focused ultrasound and treatment monitoring by MRI. The aim of this article is to give an updated overview on a "new" interventional technique and on its applications for MSK and allied sciences.

Soft-embalmed human breast tissue as a model for pre-clinical trials of HIFU - preliminary results

Around 52,000 people are diagnosed with breast cancer each year in the UK. With the controversy around over diagnosis arising from the breast screening programme there is intense interest in the possibility of safe effective non-invasive treatment of cancers. As a non-invasive method of lumpectomy, focused ultrasound surgery (FUS) may offers reduced risk of infection, fewer complications and a shorter recovery time. It also allows more precise treatment as a result of real-time guidance by magnetic resonance (MR) or ultrasound. Even though specially designed FUS transducers for breast cancer treatment are now becoming available, transducer efficacy needs to be tested with a suitable preclinical model. A specific issue is the accuracy of temperature monitoring of FUS with MRI in the breast, since the presence of large amounts of surrounding fat can impair temperature measurement with the proton resonant frequency. An appropriate anatomical model that enforces comparable physical constraints to the breast and that responds to FUS in the same way would be extremely advantageous. The aim of this feasibility study is to explore the use of soft embalmed cadaveric breast tissue for these purposes. We report here the early results of MRI-guided FUS experiments sonicating dissected breast samples from a soft-embalmed human cadaver with a high body mass index (BMI).

Focused Ultrasound as a Local Therapy for Liver Cancer

Conventional surgical treatments of liver cancer are invasive (including minimally invasive) with a high incidence of new metastasis and poor success, even after multiple resections or ablations. These limitations motivated research into new, less invasive solutions for liver cancer treatment.Focused ultrasound surgery (FUS), or high-intensity focused ultrasound, has been recognized as a noninvasive technology for benign and malignant tumor treatment. Previously, FUS was guided with ultrasound that has limited target definition and monitoring capability of the ablation process. Combining magnetic resonance imaging (MRI) with multiple-element phased-array transducers to create MRI-guided focused ultrasound thermal therapy provides more accurate targeting and real-time temperature monitoring. This treatment is hindered by the ribcage that limits the acoustic windows to the liver and the respiratory motion of the liver. New advances in MRI and transducer design will likely resolve these limitations and make MRI-guided FUS a powerful tool in local liver cancer therapy. This article reviews this technology and advances that can expand its use for cancer treatment in general and liver cancer in particular.

MRI‐based thermal dosimetry and diffusion‐weighted imaging of MRI‐guided focused ultrasound thermal ablation of uterine fibroids

To investigate tissue changes observed in diffusion-weighted imaging (DWI) and its relation to contrast imaging, thermal dosimetry, and changes in the apparent diffusion coefficient (ADC) after MRI-guided focused ultrasound surgery (MRgFUS) of uterine fibroids. Imaging data were analyzed from 45 fibroids in 42 women treated with MRgFUS. The areas of the hyperintense regions in DWI and of nonperfused regions in T1-weighted contrast enhanced imaging (both acquired immediately after treatment) were compared with each other and to thermal dosimetry based estimates. Changes in ADC were also calculated. Hyperintense regions were observed in 35/45 fibroids in DWI. When present, the areas of these regions were comparable on average to the thermal dose estimates and to the nonperfused regions, except for in several large treatments in which the nonperfused region extended beyond the treated area. ADC increased in 19 fibroids and decreased in the others. DWI changes, which includes changes in both in T2 and ADC, may be useful in many cases to delineate the treated region resulting from MRgFUS. However, clear DWI changes were not always observed, and in some large treatments, the extent of the nonperfused region was under estimated. ADC changes immediately after MRgFUS were unpredictable.

Evaluation of referenceless thermometry in MRI‐guided focused ultrasound surgery of uterine fibroids

To clinically assess a previously described method (Rieke et.al., Magn Reson Med 2004) to produce more motion-robust MRI-based temperature images using data acquired during MRI-guided focused ultrasound surgery (MRgFUS) of uterine fibroids. The method ("referenceless thermometry") uses surface fitting in nonheated regions of individual phase images to extrapolate and then remove background phase variations that are unrelated to temperature changes. We tested this method using images from 100 sonications selected from 33 patient MRgFUS treatments. Temperature measurements and thermal dose contours estimated with the referenceless method were compared with those produced with the standard phase-difference technique. Fitting accuracy and noise level were also measured. In 92/100 sonications, the difference between the two measurements was less than 3 degrees C. The average difference in the measurements was 1.5 +/- 1.4 degrees C. Small motion artifacts were observed in the phase-difference imaging when the difference was greater than 3 degrees C. The method failed in two cases. The mean absolute error in the surface fit in baseline images corresponded to a temperature error of 0.8 +/- 1.4 degrees C. The noise level was approximately 40% lower than the phase-difference method. Thermal dose contours calculated from the two methods agreed well on average. Based on the small error when compared with the standard technique, this method appears to be adequate for temperature monitoring of MRgFUS in uterine fibroids and may prove useful for monitoring temperature changes in moving organs.

Image-Based Control of the Magnetic Resonance Imaging-Guided Focused Ultrasound Thermotherapy

Magnetic resonance imaging (MRI)-guided focused ultrasound surgery (FUS) is a full noninvasive approach for localized thermal ablation of deep tissues, coupling the following: (1) a versatile, nonionizing physical agent for therapy and (2) a state-of-the art diagnosis and on-line monitoring tool. A commercially available, Food and Drug Administration-approved device using the MRI-guided FUS exists since 2004 for the ablation of benign tumors (uterine fibroids); however, the ultimate goal of the technological, methodological, and medical research in this field is to provide a clinical-routine tool for fighting localized cancer. When addressing cancer applications, the accurate spatial control of the delivered thermal dose is mandatory. Contiguous destruction of the target volume must be achieved in a minimum time, whereas sparing as much as possible the neighboring healthy tissues and especially when some adjacent regions are critical. This paper reviews some significant developments reported in the literature related to the image-based control of the FUS therapy for kidney, breast, prostate, and brain, including the own experience of the authors on the active feedback control of the temperature during FUS ablation. In addition, preliminary results of an original study of MRI-guided FUS ablation of VX2 carcinoma in kidney, under active temperature control, are described here.

Influence of post-treatment delay on the evaluation of the response to focused ultrasound surgery of breast cancer by dynamic contrast enhanced MRI

The assessment of the effectiveness of MRI-guided focused ultrasound surgery (MRIgFUS) of breast carcinomas can be performed by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters which monitor the presence of residual tumour. The aim of this study was to evaluate the effect of the post-treatment delay on this assessment. DCE-MRI data were acquired immediately and 3-14 days after MRIgFUS treatment of 26 tumours (<7 days, n = 6; = or > ge;7 days, n = 20). The percentage of residual tumour was determined histologically on the resected mass and correlated with two DCE-MRI parameters: increase in signal intensity (ISI) and positive enhancement integral (PEI). No correlation could be found between DCE-MRI data acquired immediately after treatment and the percentage of residual tumour. Good correlation coefficients were found for data acquired several days after treatment (ISI, r = 0.749; PEI, r = 0.778). However, they were higher when the post-treatment time interval was 7 days or more (ISI, r = 0.962; PEI, r = 0.934). These results suggest that a post-treatment delay of 7 days is necessary for the accurate assessment of the presence of residual tumour by DCE-MRI parameters.

MR imaging-guided focused ultrasound surgery of breast cancer: correlation of dynamic contrast-enhanced MRI with histopathologic findings.

To assess the value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters to monitor residual tumor following non-invasive MRI-guided focused ultrasound surgery (MRIgFUS) of breast tumors. DCE-MRI data were acquired before and after the MRIgFUS treatment of small breast tumors (d < 3.5 cm) for 17 patients. The lesion was surgically resected and the presence of residual tumor was determined by histopathological analysis. The percentage of residual tumor was correlated with three DCE-MRI parameters measured at the maximally enhancing site of each tumor: increase in signal intensity (ISI), maximum difference function (MDF) and positive enhancement integral (PEI). A good correlation was found between the ISI (r = 0.897), MDF (r = 0.789) and PEI (r = 0.859) parameters and the percentage of residual viable tumor determined by histopathology. A receiver operator characteristic curve analysis yielded a cutoff value for ISI at 20% with a sensitivity of 77% and a specificity of 100%. These results suggest that parameters from DCE-MRI data could provide a reliable non-invasive method for assessing residual tumor following MRIgFUS treatment of breast tumors.

MRT-überwachte Chirurgie mit hochenergetischem fokussiertem Ultraschall

High-intensity focused ultrasound allows high-precision, non-invasive thermocoagulation of tissues within seconds, with sparing of surrounding areas. The resulting tissue necrosis is so sharply demarcated that the technique is also defined focused ultrasound surgery (FUS). The combination with magnetic resonance imaging (MRI) allows an exact definition of the target volume and a safe guidance of FUS. The present paper describes the physical equipment necessary to perform MRI-guided FUS, and reports an example of application of this technique for the therapy of breast cancer. Finally, the paper outlines further examples of FUS application and future perspectives.

MR monitoring of focused ultrasound surgery in a breast tissue model in vivo

The objective of this study was to investigate MRI methods for monitoring focused ultrasound surgery (FUS) of breast tumors. To this end, the mammary glands of sheep were used as tissue model. The tissue was treated in vivo with numerous single sonications which covered extended target volumes by employing a scanning technique. The ultrasound focus position was controlled by online temperature mapping based on the temperature dependence of the relaxation time T1. This approach proved to be reliable and offers thus an alternative to proton resonance frequency methods, whose application is hampered in fatty tissues. FUS-induced tissue changes were visible on T2- as well as on pre- and post-contrast T1-weighted images. According to our initial experience, noninvasive MRI-guided FUS of breast tumors is feasible.