Real-Time Monitoring of High-Intensity Focused Ultrasound Thermal Therapy Using the Manifold Learning Method

High-intensity focused ultrasound (HIFU) induces thermal lesions by increasing the tissue temperature in a tight focal region. The main ultrasound imaging techniques currently used to monitor HIFU treatment are standard pulse-echo B-mode ultrasound imaging, ultrasound temperature estimation and elastography-based methods. The present study was carried out on ex vivo animal tissue samples, in which backscattered radiofrequency (RF) signals were acquired in real time at time instances before, during and after HIFU treatment. The manifold learning algorithm, a non-linear dimensionality reduction method, was applied to RF signals which construct B-mode images to detect the HIFU-induced changes among the image frames obtained during HIFU treatment. In this approach, the embedded non-linear information in the region of interest of sequential images is represented in a 2-D manifold with the Isomap algorithm, and each image is depicted as a point on the reconstructed manifold. Four distinct regions are chosen in the manifold corresponding to the four phases of HIFU treatment (before HIFU treatment, during HIFU treatment, immediately after HIFU treatment and 10-min after HIFU treatment). It was found that disorganization of the points is achieved by increasing the acoustic power, and if the thermal lesion has been formed, the regions of points related to pre- and post-HIFU significantly differ. Moreover, the manifold embedding was repeated on 2-D moving windows in RF data envelopes related to pre- and post-HIFU exposure data frames. It was concluded that if mean values of the points related to pre- and post-exposure frames in the reconstructed manifold are estimated, and if the Euclidean distance between these two mean values is calculated and the sliding window is moved and this procedure is repeated for the whole image, a new image based on the Euclidean distance can be formed in which the HIFU thermal lesion is detectable.     

Evaluating the safety profile of focused ultrasound and microbubble-mediated treatments to increase blood-brain barrier permeability

Introduction: Treatment of several diseases of the brain are complicated by the presence of the skull and the blood-brain barrier (BBB). Focused ultrasound (FUS) and microbubble (MB)-mediated BBB treatment is a minimally invasive method to transiently increase the permeability of blood vessels in targeted brain areas. It can be used as a general delivery system to increase the concentration of therapeutic agents in the brain parenchyma.

Areas covered: Over the past two decades, the safety of using FUS+MBs to deliver agents across the BBB has been interrogated through various methods of imaging, histology, biochemical assays, and behavior analyses. Here we provide an overview of the factors that affect the safety profile of these treatments, describe methods by which FUS+MB treatments are controlled, and discuss data that have informed the assessment of treatment risks.

Expert opinion: There remains a need to assess the risks associated with clinically relevant treatment strategies, specifically repeated FUS+MB treatments, with and without therapeutic agent delivery. Additionally, efforts to develop metrics by which FUS+MB treatments can be easily compared across studies would facilitate a more rapid consensus on the risks associated with this intervention.     

高强度聚焦超声（HIFU）治疗肝癌肝硬化脾功能亢进的疗效观察

目的：观察高强度聚焦超声(HIFU)治疗肝癌肝硬化脾功能亢进的疗效。方法收集我院消化内科的住院患者,收集时间为2011年11月~2013年12月,共计21例,所有研究对象均诊断为由于肝癌肝硬化脾功能亢进,男16例,女5例,平均年龄(54.2±17.5)岁,随机分为A组,B组,C组,分别接受高强度聚焦超声90次、60次、30次。结果研究对象中最多见的不良反应是发热,共计5例,体温(37.6±0.4)℃,4例研究对象在治疗后1天有局部红肿,蜕皮,在皮肤科治疗后症状消失,继续治疗。所有研究对象在治疗间期均无内出血、腹腔积液增多、胸腔积液、周围脏器受损、及血尿现象。我们发现A组接受高强度聚焦超声治疗最多90次,其组在0月、1月、2月、3月时的白细胞、血红蛋白以及血小板最高,肿瘤缩小最大,C组接受高强度聚焦超声治疗最少30次,其组在0月、1月、2月、3月时的白细胞、血红蛋白以及血小板最低,肿瘤缩小最小,差异有统计学意义(P<0.05)。结论随着高强度聚焦超声治疗次数的增加,肝癌肝硬化脾功能亢进患者白细胞、血红蛋白以及血小板恢复的越好,肿块缩小最大。     

High Intensity Positive Pressure Ventilation and Long Term Pulmonary Function Responses in Severe Stable COPD. A Delicate and Difficult Balance

Method to improve minute ventilation (MV) during spontaneous breathing (SB) in stable severe chronic obstructive pulmonary disease (COPD) have a great clinical relevant in long term outcome. In this scenario, recommendations of early use of high-Intensity non-invasive Positive pressure Ventilation (HI-NPPV) or intelligent Volume Assured Pressure (iVAP) Support in Hypercapnic COPD have been proposed by safe therapeutics options. We analyze in this letter, Ekkernkamp et al. study that described the effect of HI-NPPV compared with SB on MV in patients receiving long-term treatment. We consider that interpretation of relationships between ABG, functional parameters, and respiratory mechanics reported need clarifications. Further prospective large clinical trials identifying the best mode of ventilation according to the characteristics in severe stable COPD are necessary to balance an effective approach and response on clinical symptoms and long-term effects.     

Focused Cardiac Ultrasonography: Current Applications and Future Directions

Focused cardiac ultrasonography is performed by clinicians at the bedside and is used in time‐sensitive scenarios to evaluate a patient's cardiovascular status when comprehensive echocardiography is not immediately available. This simplified cardiac ultrasonography is often performed by noncardiologists using small, portable devices to augment the physical examination, triage patients, and direct management in both critical care and outpatient settings. However, as the use of focused cardiac ultrasonography continues to expand, careful consideration is required regarding training, scope of practice, impact on patient outcomes, and medicolegal implications. In this review, we examine some of the challenges with rapid uptake of this technique and explore the benefits and potential risk of focused cardiac ultrasonography. We propose possible mechanisms for cross‐specialty collaboration, quality improvement, and oversight.     

Establishment of a scoring system for predicting the difficulty level of high-intensity focussed ultrasound ablation of uterine fibroids

Purpose: To establish a scoring system that predicts the difficulty level of high-intensity focussed ultrasound (HIFU) ablation of uterine fibroids.

Materials and methods: Four hundred and twenty-two patients with fibroids were enrolled. The energy efficiency factor (EEF) and sonication time were set as dependent variables, with factors possibly affecting EEF and sonication time including age, body mass index (BMI), the volume of fibroids, the location of the uterus, the type of fibroids, the signal intensity on the T2-weighted imaging (T2WI), the enhancement type, the thickness of the rectus abdominis and the subcutaneous fat layer, the distance from the anterior/posterior surface of the fibroid to the skin, and the abdominal wall scars were set as predictors for building optimal scaling regression models.

Results: The volume of the fibroids, the location of the uterus, the signal intensity on T2WI, enhancement type, rectus abdominis thickness, subcutaneous fat thickness, and distance from the anterior surface of fibroid to the skin were related to EEF. Signal intensity on T2WI, the volume of fibroids, distance from the posterior surface of fibroid to the skin, and enhancement type were related to sonication time. Models that can predict the difficulty level of HIFU for fibroids have been established: for EEF, y?′?=?0.338X?′₁???0.231X?′₂+0.156X?′₃+0.167X?′₄?; for sonication time, y?=?0.227X₁+0.321X₂+0.157X₃+0.194X₄.

Conclusions: A scoring system for predicting the difficulty level of HIFU treatment for uterine fibroids has been established and it can be used to help select patients and to predict the sonication time for a given fibroid.     

Design and analysis of annular antenna arrays with different reflectors

The design and performance of annular antenna arrays with reflectors is presented. Arrays with three shapes of reflectors are analysed and simulated. These include the corner reflector, the circular reflector and the elliptical reflector. Power-density distributions within the annular arrays with and without reflectors are obtained by using the FDTD method. Also, the image theory method is used to verify the FDTD results in one case. By comparing the power-density distribution pattern of all four of the array designs (three with different reflectors, one without reflector), it is readily seen in each case that the array with reflectors yields better power-efficiency than the array without reflectors and the elliptical reflector yields the best performance. Comparisons of each array are made using 4, 6 and 8 antennae in the annular array. By using the optimized results of the elliptical reflector, the requirement for the input-power level to each antenna is greatly reduced.     

Traitements de rattrapage après irradiation prostatique : place de l’urologue

The management of recurrent prostate cancer after radiotherapy or brachytherapy is non-standardized and rapidly evolving. Local recurrence is observed on average in 30% of cases several years following irradiation. A key challenge is to determine the site of recurrence and imaging (MRI and PET choline) coupled to prostate biopsies are important to confirm the local character. Salvage therapy performed by the urologist can then control the situation. Radical prostatectomy subject to strict technical conditions is one of the most efficient local treatments, however it comes at the cost of significant urinary morbidity; minimally invasive therapies (focused ultrasound and cryotherapy) have also their place in specific indications. Each clinical situation should be discussed in pluridisciplinary meetings integrating the oncologic and functional status at recurrence, the risk/benefit ratio of each treatment, the patient's wishes and probability of survival.     

Experimental Methods for Improved Spatial Control of Thermal Lesions in Magnetic Resonance-Guided Focused Ultrasound Ablation

Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU, or MRgFUS) is a hybrid technology that was developed to provide efficient and tolerable thermal ablation of targeted tumors or other pathologic tissues, while preserving the normal surrounding structures. Fast 3-D ablation strategies are feasible with the newly available phased-array HIFU transducers. However, unlike fixed heating sources for interstitial ablation (radiofrequency electrode, microwave applicator, infra-red laser applicator), HIFU uses propagating waves. Therefore, the main challenge is to avoid thermo-acoustical adverse effects, such as energy deposition at reflecting interfaces and thermal drift of the focal lesion toward the near field. We report here our investigations on some novel experimental solutions to solve, or at least to alleviate, these generally known tolerability problems in HIFU-based therapy. Online multiplanar MR thermometry was the main investigational tool extensively used in this study to identify the problems and to assess the efficacy of the tested solutions. We present an improved method to cancel the beam reflection at the exit window (i.e., tissue-to-air interface) by creating a multilayer protection, to dissipate the residual HIFU beam by bulk scattering. This study evaluates selective de-activation of transducer elements to reduce the collateral heating at bone surfaces in the far field, mainly during automatically controlled volumetric ablation. We also explore, using hybrid US/MR simultaneous imaging, the feasibility of using disruptive boiling at the focus, both as a far-field self-shielding technique and as an enhanced ablation strategy (i.e., boiling core controlled HIFU ablation).