Noninvasive Surgery Research Articles

A 3D time reversal cavity for the focusing of high-intensity ultrasound pulses over a large volume

Shock wave ultrasound therapy techniques, increasingly used for non-invasive surgery, require extremely high pressure amplitudes in precise focal spots, and large high-power transducers arranged on a spherical shell are usually used to achieve that. This solution allows limited steering of the beam around the geometrical focus of the device at the cost of a large number of transducer elements, and the treatment of large and moving organs like the heart is challenging or impossible. This paper validates numerically and experimentally the possibility of using a time reversal cavity (TRC) for the same purpose. A 128-element, 1 MHz power transducer combined with different multiple scattering media in a TRC was used. We were able to focus high-power ultrasound pulses over a large volume in a controlled manner, with a limited number of transducer elements. We reached sufficiently high pressure amplitudes to erode an Ultracal® target over a 10 cm2 area.

Development and validation of a MRgHIFU non-invasive tissue acoustic property estimation technique

MR-guided high-intensity focussed ultrasound (MRgHIFU) non-invasive ablative surgeries have advanced into clinical trials for treating many pathologies and cancers. A remaining challenge of these surgeries is accurately planning and monitoring tissue heating in the face of patient-specific and dynamic acoustic properties of tissues. Currently, non-invasive measurements of acoustic properties have not been implemented in MRgHIFU treatment planning and monitoring procedures. This methods-driven study presents a technique using MR temperature imaging (MRTI) during low-temperature HIFU sonications to non-invasively estimate sample-specific acoustic absorption and speed of sound values in tissue-mimicking phantoms. Using measured thermal properties, specific absorption rate (SAR) patterns are calculated from the MRTI data and compared to simulated SAR patterns iteratively generated via the Hybrid Angular Spectrum (HAS) method. Once the error between the simulated and measured patterns is minimised, the estimated acoustic property values are compared to the true phantom values obtained via an independent technique. The estimated values are then used to simulate temperature profiles in the phantoms, and compared to experimental temperature profiles. This study demonstrates that trends in acoustic absorption and speed of sound can be non-invasively estimated with average errors of 21% and 1%, respectively. Additionally, temperature predictions using the estimated properties on average match within 1.2 °C of the experimental peak temperature rises in the phantoms. The positive results achieved in tissue-mimicking phantoms presented in this study indicate that this technique may be extended to in vivo applications, improving HIFU sonication temperature rise predictions and treatment assessment.

Medically resistant pediatric insular-opercular/perisylvian epilepsy. Part 1: invasive monitoring using the parasagittal transinsular apex depth electrode.

OBJECTIVE Insular lobe epilepsy (ILE) is an under-recognized cause of extratemporal epilepsy and explains some epilepsy surgery failures in children with drug-resistant epilepsy. The diagnosis of ILE usually requires invasive investigation with insular sampling; however, the location of the insula below the opercula and the dense middle cerebral artery vasculature renders its sampling challenging. Several techniques have been described, ranging from open direct placement of orthogonal subpial depth and strip electrodes through a craniotomy to frame-based stereotactic placement of orthogonal or oblique electrodes using stereo-electroencephalography principles. The authors describe an alternative method for sampling the insula, which involves placing insular depth electrodes along the long axis of the insula through the insular apex following dissection of the sylvian fissure in conjunction with subdural electrodes over the lateral hemispheric/opercular region. The authors report the feasibility, advantages, disadvantages, and role of this approach in investigating pediatric insular-opercular refractory epilepsy. METHODS The authors performed a retrospective analysis of all children (< 18 years old) who underwent invasive intracranial studies involving the insula between 2002 and 2015. RESULTS Eleven patients were included in the study (5 boys). The mean age at surgery was 7.6 years (range 0.5-16 years). All patients had drug-resistant epilepsy as defined by the International League Against Epilepsy and underwent comprehensive noninvasive epilepsy surgery workup. Intracranial monitoring was performed in all patients using 1 parasagittal insular electrode (1 patient had 2 electrodes) in addition to subdural grids and strips tailored to the suspected epileptogenic zone. In 10 patients, extraoperative monitoring was used; in 1 patient, intraoperative electrocorticography was used alone without extraoperative monitoring. The mean number of insular contacts was 6.8 (range 4-8), and the mean number of fronto-parieto-temporal hemispheric contacts was 61.7 (range 40-92). There were no complications related to placement of these depth electrodes. All 11 patients underwent subsequent resective surgery involving the insula. CONCLUSIONS Parasagittal transinsular apex depth electrode placement is a feasible alternative to orthogonally placed open or oblique-placed stereotactic methodologies. This method is safe and best suited for suspected unilateral cases with a possible extensive insular-opercular epileptogenic zone.

Rheological evaluations and in vitro studies of injectable bioactive glass-polycaprolactone-sodium alginate composites.

Composite pastes composed of various amounts of melt-derived bioactive glass 52S4 (MG5) and polycaprolactone (PCL) microspheres in sodium alginate solution were prepared. Rheological properties in both rotatory and oscillatory modes were evaluated. Injectability was measured as injection force versus piston displacement. In vitro calcium phosphate precipitation was also studied in simulated body fluid (SBF) and tracked using scanning electron microscopy, X-ray diffraction and FTIR analyses. All composite pastes were thixotropic in nature and exhibited shear thinning behavior. The magnitude of thixotropy decreased by adding 10-30wt% PCL, while further amounts of PCL increased it again. Moreover, the composites were viscoelastic materials in which the elastic modulus was higher than viscous term. The pastes which were just made of MG5 or PCL had poor injectability, whereas the composites containing both of these constituents exhibited reasonable injectability. All pastes revealed adequate structural stability in contact with SBF solution. In vitro calcium phosphate precipitation was well observed on the paste made of MG5 and somewhat on the pastes with 10-40wt% PCL, however the precipitated layer was amorphous in nature. Overall, the produced composites may be appropriate as injectable biomaterials for non-invasive surgeries but more biological evaluations are essential.

Position control of a servo-pneumatic actuator with mis-matched uncertainty using multiple-surface sliding mode controller and high-gain observer

This research develops a multiple-surface sliding mode control (MSSC) approach for position control of a servo-pneumatic system in the presence of mismatched uncertainties due to the friction force of the cylinder sealing. Servo-pneumatic actuators have many applications such as industrial automation, haptic interfaces, rehabilitation robots and non-invasive surgeries. Non-linearities due to internal and external disturbances, such as the friction force between the piston seal and cylinder wall, make it difficult to achieve adequate performance from these actuators. Thus, modelling and identification of friction parameters is an essential part of the controller design procedure. A simple model for friction such as the Stribeck model may be used in order to reduce the complexity of the identification procedure. In addition, a bounded uncertainty owing to the unmodelled dynamics of friction is considered. The lack of direct measurement for systems velocity necessitates finding a solution to estimate this parameter. One answer to this problem is to employ a high-gain observer. Whereas mismatched uncertainties appear in the state space equation of the system before control input, control input cannot apply directly to them. In the proposed framework, an MSSC scheme has been used to cope with these types of uncertainties. Asymptotic stability of the closed-loop system is proven by using the Lyapunov method; experimental results show that the proposed controller can deliver a good tracking performance and is robust to uncertainties. Experimental results validate the controller performance.

Selective focusing through target identification and experimental acoustic signature extraction: Numerical experiments

Using transducer arrays and appropriate emission delays allow to focus acoustic waves at a chosen location in a medium. The focusing spatial accuracy depends on the accurate knowledge of its acoustic properties. When those properties are unknown, methods based on the Time-Reversal principle allow accurate focusing. Still, these methods are either intrusive (an active source has to be introduced at the target location first), either blind (the target cannot be selected in the presence of several objects.) The purpose of the present work is to achieve non-invasive accurate focusing on a selected target using inaccurate acoustic properties for the investigated medium. Potential applications are for instance noninvasive surgery based on High Intensity Focused Ultrasound (HIFU). Numerical experiments are presented and demonstrate accurate focusing on a previously designated target located in an unknown heterogeneous medium.

Radio frequency ultrasound time series signal analysis to evaluate high-intensity focused ultrasound lesion formation status in tissue

High-intensity focused ultrasound (HIFU) is a novel treatment modality used by scientists and clinicians in the recent decades. This modality has had a great and significant success as a noninvasive surgery technique applicable in tissue ablation therapy and cancer treatment. In this study, radio frequency (RF) ultrasound signals were acquired and registered in three stages of before, during, and after HIFU exposures. Different features of RF time series signals including the sum of amplitude spectrum in the four quarters of the frequency range, the slope, and intercept of the best-fit line to the entire power spectrum and the Shannon entropy were utilized to distinguish between the HIFU-induced thermal lesion and the normal tissue. We also examined the RF data, frame by frame to identify exposure effects on the formation and characteristics of a HIFU thermal lesion at different time steps throughout the treatment. The results obtained showed that the spectrum frequency quarters and the slope and intercept of the best fit line to the entire power spectrum both increased two times during the HIFU exposures. The Shannon entropy, however, decreased after the exposures. In conclusion, different characteristics of RF time series signal possess promising features that can be used to characterize ablated and nonablated tissues and to distinguish them from each other in a quasi-quantitative fashion.

From Catheters To Ventricular Assist Devices: 60 Years of Cardiovascular Experiences With William L. Winters, JR., M.D.

Automatic typewriters, transistor radios, microfiche, black and white television…while considered high-tech in the 1950s, these technologies seem limited when viewed from the 21st century. The same is true for cardiovascular medicine, which back then relied on electrocardiograms and X-rays for most diagnoses. In the 60 years since, advances in medical capabilities have progressed at a staggering pace. Patient research that once required months poring over paper charts is now reduced to hours using electronic medical record databases. Diagnostic images that once took days to process can now be accessed instantly through ultrasound and magnetic resonance imaging. While a half-century ago no one would have imagined accessing any and all information with a 5-second Google search, so too would noninvasive heart surgery been considered unimaginable. Since the 1950s when he graduated from medical school, William L. Winters, Jr., has been a first-hand witness to breathtaking innovations in cardiovascular medicine-both globally and in Houston. Author of Houston Hearts: A History of Cardiovascular Surgery and Medicine at Houston Methodist DeBakey Heart & Vascular Center and long-time medical editor of the Methodist DeBakey Cardiovascular Journal, Dr. Winters sat down with the journal editors this past April to share his insights from the last half-century of medical practice.

Real-time MRI feedback of cavitation ablation therapy (histotripsy)

Histotripsy ablation of liver tumors is a non-invasive surgery that uses high-intensity acoustic pulses to control an inertial cavitation cloud. Repeated exposure to the cavitation cloud renders a target tissue into a homogenous slurry which is then gradually absorbed by the body. Like other non-invasive surgeries, histotripsy requires a feedback system that can estimate therapy location and dose in real-time. Because the time-average power output of histotripsy is very small, the treatment region does not express a significant rise in temperature, making MRI thermometry an ineffective method to actively monitor therapy. Previous work has shown that MRI pulse sequences can be made sensitive to the chaotic water flow present during inertial cavitation. This is done by synchronizing the timing of the histotripsy pulses with the timing of the sequence’s gradient waveforms. Incoherent water flow caused by cavitation attenuates the MR signal through a process similar to that used in diffusion-weighted MRI. It was shown that these sequences can give localized contrast specific to histotripsy bubble clouds. However, the MR images could only be acquired in a piecemeal fashion over several minutes such that a single image represented the influence of many cavitation events. Here, we introduce a single-shot MR acquisition sequence that is able to rapidly acquire a complete MR image and remain sensitive to histotripsy cavitation. This is done by synchronizing each histotripsy pulse with incoherent motion-weighting gradients placed just before the readout portion of the sequence. When repeated at the same rate as the histotripsy pulses, the resulting MR images can give feedback on the location of every cavitation cloud applied to the target tissue.

The biopsychosocial characteristics associated with self-management and self-efficacy for individuals in the longer term after stroke

reporting it to be compulsory and 4 (27%) to be optional. Also, chest clearance is compulsory in 10 (66%) responding countries and optional in 5 (33%). Only 9 (60%) responders indicated that patient assessment is compulsory, 5 (33%) that is optional and 1 (6%) that is not covered. The areas which were considered least compulsory were: Non-invasive ventilation, abdominal surgery, intensive care, and paediatrics. Student assessment of respiratory practice was reported by 10 (66%) participants with only 7 (47%) receiving a mark or grade for their respiratory physiotherapy practice assessment. Conclusion(s): There is a wide range of models used in practice respiratory physiotherapy education. Not all physiotherapy students in Europe have an opportunity to experience and learn about respiratory physiotherapy in practice. Further differences concern content and assessment methods. There is very little harmonisation of requirements for respiratory physiotherapy. Implications: This study highlights the lack of harmonisation of respiratory physiotherapy PE, which may impact on physiotherapy safe practice across borders and lack of specialists in this area of physiotherapy. There is a need for future enhanced provision of respiratory PE to all physiotherapy students in Europe.

Real Time Target Tracking in a Phantom Using Ultrasonic Imaging

In this paper we present a real-time ultrasound image guidance method suitable for tracking the motion of tumors. A 2D ultrasound based motion tracking system was evaluated. A robot was used to control the focused ultrasound and position it at the target that has been segmented from a real-time ultrasound video. Tracking accuracy and precision were investigated using a lesion mimicking phantom. Experiments have been conducted and results show sufficient efficiency of the image guidance algorithm. This work could be developed as the foundation for combining the real time ultrasound imaging tracking and MRI thermometry monitoring non-invasive surgery.

Control of a thin catheter bending at bifurcation points in artificial blood vessel by using acoustic radiation force.

In this paper, control of a thin catheter bending by using acoustic radiation force was carried out to develop precise and noninvasive surgery in small blood vessel. First, it was elucidated that the acting force to a thin catheter made from perfluoroalkoxy (PFA) copolymer could be obtained from the cantilever equation in the effective range, where the displacement of the catheter divided by the cube of the length of the catheter was less than 1.0×10(-5) mm(-2). Next, under the above cantilever theory, acoustic radiation force acting to the catheter was measured in the condition of the continuous ultrasound radiation. Furthermore, it was observed that the force depended on the ultrasound frequency. We confirmed that the force was obtained in the practical condition by the experiment and controlled it bending in artificial blood vessel including multiple bifurcations. It was suggested that the therapy using thin catheter and ultrasound is fully promising.

Integrated diagnostic and therapeutic techniques: Toward an intelligent medical system

Rapid technical advances in medical information and tools ave attracted significant interest in close integration of research n medicine, life sciences, physics, chemistry, computer science, nd engineering. However, most prediction and diagnosis techiques in conventional medicine have been used in a separate step rior to treatment. Technical advances in therapeutic delivery and growing demand for patient-specific treatment have recently ccelerated the clinical applications of related diagnosis and theraeutic techniques. Techniques for diagnosis and treatment have een integrated, e.g., through imaging modalities and intervenion devices and thus provide high-precision minimally invasive reatment. There have been significant advances in the field of minimally nvasive and non-invasive surgeries. Compared with conventional iagnosis and therapy, future research on and clinical trials prooting minimally invasive surgery are expected to shift medical maging from a primarily diagnostic modality to a therapeutic and nterventional aid. Integrated diagnostic and therapeutic processes ill be streamlined through the application of intra-operative medcal information and robotic-assisted intervention and brought o clinical trials. Along with developments in minimally invaive treatment methodologies, the integration of diagnosis and reatment techniques has gradually attracted increasing attention rom research groups across the globe. Numerous representative ntegrated techniques have been developed for the design and abrication of medical tools [1–3]. Corresponding diagnostic and herapeutic techniques and medical devices have also been develped for use in clinical trials, such as neurosurgery, cardiovascular urgery, and abdominal surgery in recent years. Furthermore, bioedical imaging has played an increasingly important role in argeted therapy with interventions such as drug or gene therpy, which provide more accurate delivery tailored to individual atients. Intelligent systems in medicine with pre-targeting and local reatment devices have also been developed. These systems enable paradigm shift in healthcare technology research; the focus s moving from developing pharmaceutical products that target

Pathophysiological mechanisms of high-intensity focused ultrasound-mediated vascular occlusion and relevance to non-invasive fetal surgery

High-intensity focused ultrasound (HIFU) is a non-invasive technology, which can be used occlude blood vessels in the body. Both the theory underlying and practical process of blood vessel occlusion are still under development and relatively sparse in vivo experimental and therapeutic data exist. HIFU would however provide an alternative to surgery, particularly in circumstances where serious complications inherent to surgery outweigh the potential benefits. Accordingly, the HIFU technique would be of particular utility for fetal and placental interventions, where open or endoscopic surgery is fraught with difficulty and likelihood of complications including premature delivery. This assumes that HIFU could be shown to safely and effectively occlude blood vessels in utero. To understand these mechanisms more fully, we present a review of relevant cross-specialty literature on the topic of vascular HIFU and suggest an integrative mechanism taking into account clinical, physical and engineering considerations through which HIFU may produce vascular occlusion. This model may aid in the design of HIFU protocols to further develop this area, and might be adapted to provide a non-invasive therapy for conditions in fetal medicine where vascular occlusion is beneficial.

Statistical model based 3D shape prediction of postoperative trunks for non-invasive scoliosis surgery planning

One of the major concerns of scoliosis patients undergoing surgical treatment is the aesthetic aspect of the surgery outcome. It would be useful to predict the postoperative appearance of the patient trunk in the course of a surgery planning process in order to take into account the expectations of the patient. In this paper, we propose to use least squares support vector regression for the prediction of the postoperative trunk 3D shape after spine surgery for adolescent idiopathic scoliosis. Five dimensionality reduction techniques used in conjunction with the support vector machine are compared. The methods are evaluated in terms of their accuracy, based on the leave-one-out cross-validation performed on a database of 141 cases. The results indicate that the 3D shape predictions using a dimensionality reduction obtained by simultaneous decomposition of the predictors and response variables have the best accuracy.

Revascularization Saves Limbs and Function in Frail Elderly

Revascularization Saves Limbs and Function in Frail Elderly

High-intensity focused ultrasound for potential treatment of polycystic ovary syndrome: toward a noninvasive surgery

To investigate the feasibility of using high-intensity focused ultrasound (HIFU), under dual-mode ultrasound arrays (DMUAs) guidance, to induce localized thermal damage inside ovaries without damage to the ovarian surface. Laboratory feasibility study. University-based laboratory. Ex vivo canine and bovine ovaries. DMUA-guided HIFU. Detection of ovarian damage by ultrasound imaging, gross pathology, and histology. It is feasible to induce localized thermal damage inside ovaries without damage to the ovarian surface. DMUA provided sensitive imaging feedback regarding the anatomy of the treated ovaries and the ablation process. Different ablation protocols were tested, and thermal damage within the treated ovaries was histologically characterized. The absence of damage to the ovarian surface may eliminate many of the complications linked to current laparoscopic ovarian drilling (LOD) techniques. HIFU may be used as a less traumatic tool to perform LOD.

Computational study on the propagation of strongly focused nonlinear ultrasound in tissue with rib-like structures

The presence of a rib cage is a significant hindrance to the potential applications of focused ultrasound as a noninvasive extracorporeal surgery modality for various internal organs. Here the influence of ribs on the propagation of strongly focused high-intensity nonlinear ultrasound beam inside the body is studied. Based on the spheroidal beam equation, a three-dimensional numerical algorithm is developed to solve the nonlinear acoustic field generated by a focused ultrasonic transducer with a large aperture angle. Idealized ribs, of rectangular cross sectional, with high absorption and impedance, and various dimensions, are used to simulate human anatomical configurations. The changes in the spatial distribution of acoustic intensity and the reduction of the acoustic pressure amplitude and heat deposition rate due to the presence of "ribs" are investigated. It is somewhat surprising that in some cases, the axial peak positions shift less than 2 mm and more than 80% of the sound energy can propagate through the space of the rib cage in the strongly focused sound field. This study also includes quantitative analyses of the effects of different rib configurations and transducers of various f-numbers. The results can be used as reference information for further study and clinical applications.

Non-invasive ultrasonic surgery of the brain in non-human primates

High-intensity focused ultrasound causes selective tissue necrosis efficiently and safely, namely, in the prostate, liver, and uterine fibroid. Nevertheless, ablation of brain tissue using focused ultrasound remains limited due to strong aberrations induced by the skull. To achieve ultrasonic transcranial brain ablation, such aberrations have to be compensated. In this study, non-invasive therapy was performed on monkeys using adaptive correction of the therapeutic beam and 3D simulations of transcranial wave propagation based on 3D computed tomographic (CT) scan information. The aim of the study was two-fold: induce lesions in a non-human primate brain non-invasively and investigate the potential side effects. Stereotactic targeting was performed on five Macaca fascicularis individuals. Each hemisphere was treated separately with a 15-day interval and animals were sacrificed two days after the last treatment. The ultrasonic dose delivered at the focus was increased from one treatment location to the other to estimate the thermal dose for tissue alteration. Thermal doses in the brain were determined by numerical computations. Treatment efficiency and safety were evaluated histologically. The threshold for tissue damage in the brain was measured to be between 90 and 280 cumulative equivalent minutes at 43 °C. Intravenous injection of corticoids before the treatment limited the side effects.

Subacute Transcatheter CoreValve Thrombotic Obstruction

An 86-year-old man with severe symptomatic aortic stenosis (additive Euroscore 7) underwent a transcatheter aortic valve implantation with a CoreValve bioprosthesis (26 mm, CoreValve Revalving Technology, Medtronic, Inc., Minneapolis, MN). The patient was discharged on aspirin and clopidogrel and advised to stop the clopidogrel after 3 months. This first 6-month follow-up was uneventful. Repeated echocardiograms obtained during this period revealed a slight increase in mean transprosthetic aortic pressure gradient without significant concomitant aortic regurgitation. At the last visit, 1 year later, the patient became symptomatic (New York Heart Association class II–III). He had no fever. Between the 6th and 12th month of follow-up, there was a documented increase in transprosthetic aortic peak velocity (4.11 m/s) and mean gradient (41 mm Hg) and a significant reduction in aortic effective orifice area (0.69 cm2), which indicated severe prosthetic valve stenosis. To evaluate the shape of the CoreValve, both transesophageal echocardiogram and cardiac computed tomography were performed. Although computed tomography revealed no change in prosthesis position (when compared with pre–transcatheter aortic valve implantation computed tomography) and the absence of significant deformation of the stent by any calcifications (Figure 1A–1D), transesophageal echocardiogram evidenced thickened …