High intensity focused ultrasound in clinical tumor ablation

Ablative Focused Ultrasound Synergistically Enhances Thermally Triggered Chemotherapy for Prostate Cancer in Vitro

High-intensity focused ultrasound (HIFU) can locally ablate biological tissues such as tumors, i.e., induce their rapid heating and coagulative necrosis without causing damage to surrounding healthy structures. It is widely used in clinical practice for minimally invasive treatment of prostate cancer. Nonablative, low-power HIFU was established as a promising tool for triggering the release of chemotherapeutic drugs from temperature-sensitive liposomes (TSLs). In this study, we combine ablative HIFU and thermally triggered chemotherapy to address the lack of safe and effective treatment options for elderly patients with high-risk localized prostate cancer. DU145 prostate cancer cells were exposed to chemotherapy (free and liposomal Sorafenib) and ablative HIFU, alone or in combination. Prior to cell viability assessment by trypan blue exclusion and flow cytometry, the uptake of TSLs by DU145 cells was verified by confocal microscopy and cryogenic scanning electron microscopy (cryo-SEM). The combination of TSLs encapsulating 10 μM Sorafenib and 8.7W HIFU resulted in a viability of less than 10% at 72 h post-treatment, which was significant less than the viability of the cells treated with free Sorafenib (76%), Sorafenib-loaded TSLs (63%), or HIFU alone (44%). This synergy was not observed on cells treated with Sorafenib-loaded nontemperature sensitive liposomes and HIFU. According to cryo-SEM analysis, cells exposed to ablative HIFU exhibited significant mechanical disruption. Water bath immersion experiments also showed an important role of mechanical effects in the synergistic enhancement of TSL-mediated chemotherapy by ablative HIFU. This combination therapy can be an effective strategy for treatment of geriatric prostate cancer patients.

Enhanced antitumor efficacy of ultrasonic cavitation with up-sized microbubbles in pancreatic cancer

Ultrasonic cavitation is a novel potential approach for cancer treatment. We optimized the techniques of ultrasonic cavitation to enhance antitumor efficacy in a mouse model with human pancreatic cancer. A polydisperse MB contrast agent formulation (TS-P) with a mean number diameter of 1.9 μm was depleted in small diameter particles by differential centrifugation, producing an “up-sized” size distribution (TS-PL) possessing a mean diameter of 2.9 μm. Mice bearing the XPA-1-RFP pancreatic tumor were treated daily for 3 consecutive days with either up-sized or standard MB. Both treatment cohorts exhibited a significant reduction in tumor volume relative to the untreated control cohort (P < 0.05), and TS-PL group has significantly reduction in tumor volume (1215.1± 324.7 mm³) compared with standard TS-P group (2131.2±753.4 mm³) (P < 0.05). The treatment with TS-PL resulted in more tumor cell necrosis and apoptosis than with TS-P. Decreased expression of CD31 and MVD was observed histologically in tumors treated with TS-PL relative to TS-P. This study demonstrates that tuning the size distribution of existing contrast agent products, specifically to reduce the concentration of small MB, is required for enhanced anti-tumor cavitation activity.

Interventional Nanotheranostics of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) accounts for over 90% of all pancreatic cancer. Nanoparticles (NPs) offer new opportunities for image-guided therapy owing to the unique physicochemical properties of the nanoscale effect and the multifunctional capabilities of NPs. However, major obstacles exist for NP-mediated cancer theranostics, especially in PDAC. The hypovascular nature of PDAC may impede the deposition of NPs into the tumor after systemic administration, and most NPs localize predominantly in the mononuclear phagocytic system, leading to a relatively poor tumor-to-surrounding-organ uptake ratio. Image guidance combined with minimally invasive interventional procedures may help circumvent these barriers to poor drug delivery of NPs in PDAC. Interventional treatments allow regional drug delivery, targeted vascular embolization, direct tumor ablation, and the possibility of disrupting the stromal barrier of PDAC. Interventional treatments also have potentially fewer complications, faster recovery, and lower cost compared with conventional therapies. This work is an overview of current image-guided interventional cancer nanotheranostics with specific attention given to their applications for the management of PDAC.

White Paper on P4 Concepts for Pediatric Imaging

Over the past decade, innovations in the field of pediatric imaging have been based largely on single-center and retrospective studies, which provided limited advances for the benefit of pediatric patients. To identify opportunities for potential "quantum-leap" progress in the field of pediatric imaging, the ACR-Pediatric Imaging Research (PIR) Committee has identified high-impact research directions related to the P4 concept of predictive, preventive, personalized, and participatory diagnosis and intervention. Input from 237 members of the Society for Pediatric Radiology was clustered around 10 priority areas, which are discussed in this article. Needs within each priority area have been analyzed in detail by ACR-PIR experts on these topics. By facilitating work in these priority areas, we hope to revolutionize the care of children by shifting our efforts from unilateral reaction to clinical symptoms, to interactive maintenance of child health.

A framework for the correction of slow physiological drifts during MR-guided HIFU therapies: Proof of concept

PURPOSE

While respiratory motion compensation for magnetic resonance (MR)-guided high intensity focused ultrasound (HIFU) interventions has been extensively studied, the influence of slow physiological motion due to, for example, peristaltic activity, has so far been largely neglected. During lengthy interventions, the magnitude of the latter can exceed acceptable therapeutic margins. The goal of the present study is to exploit the episodic workflow of these therapies to implement a motion correction strategy for slow varying drifts of the target area and organs at risk over the entire duration of the intervention.

METHODS

The therapeutic workflow of a MR-guided HIFU intervention is in practice often episodic: Bursts of energy delivery are interleaved with periods of inactivity, allowing the effects of the beam on healthy tissues to recede and/or during which the plan of the intervention is reoptimized. These periods usually last for at least several minutes. It is at this time scale that organ drifts due to slow physiological motion become significant. In order to capture these drifts, the authors propose the integration of 3D MR scans in the therapy workflow during the inactivity intervals. Displacements were estimated using an optical flow algorithm applied on the 3D acquired images. A preliminary study was conducted on ten healthy volunteers. For each volunteer, 3D MR images of the abdomen were acquired at regular intervals of 10 min over a total duration of 80 min. Motion analysis was restricted to the liver and kidneys. For validating the compatibility of the proposed motion correction strategy with the workflow of a MR-guided HIFU therapy, an in vivo experiment on a porcine liver was conducted. A volumetric HIFU ablation was completed over a time span of 2 h. A 3D image was acquired before the first sonication, as well as after each sonication.

RESULTS

Following the volunteer study, drifts larger than 8 mm for the liver and 5 mm for the kidneys prove that slow physiological motion can exceed acceptable therapeutic margins. In the animal experiment, motion tracking revealed an initial shift of up to 4 mm during the first 10 min and a subsequent continuous shift of ∼2 mm/h until the end of the intervention. This leads to a continuously increasing mismatch of the initial shot planning, the thermal dose measurements, and the true underlying anatomy. The estimated displacements allowed correcting the planned sonication cell cluster positions to the true target position, as well as the thermal dose estimates during the entire intervention and to correct the nonperfused volume measurement. A spatial coherence of all three is particularly important to assure a confluent ablation volume and to prevent remaining islets of viable malignant tissue.

CONCLUSIONS

This study proposes a motion correction strategy for displacements resulting from slowly varying physiological motion that might occur during a MR-guided HIFU intervention. The authors have shown that such drifts can lead to a misalignment between interventional planning, energy delivery, and therapeutic validation. The presented volunteer study and in vivo experiment demonstrate both the relevance of the problem for HIFU therapies and the compatibility of the proposed motion compensation framework with the workflow of a HIFU intervention under clinical conditions.

Comparison of the synergistic effect of lipid nanobubbles and SonoVue microbubbles for high intensity focused ultrasound thermal ablation of tumors

Microbubbles (MBs) are considered as an important enhancer for high intensity focused ultrasound (HIFU) treatment of benign or malignant tumors. Recently, different sizes of gas-filled bubbles have been investigated to improve the therapeutic efficiency of HIFU thermal ablation and reduce side effects associated with ultrasound power and irradiation time. However, nanobubbles (NBs) as an ultrasound contrast agent for synergistic therapy of HIFU thermal ablation remain controversial due to their small nano-size in diameter. In this study, phospholipid-shell and gas-core NBs with a narrow size range of 500-600 nm were developed. The synergistic effect of NBs for HIFU thermal ablation was carefully studied both in excised bovine livers and in breast tumor models of rabbits, and made a critical comparison with that of commercial SonoVue microbubbles (SonoVue MBs). In addition, the pathological changes of the targeted area in tumor tissue after HIFU ablation were further investigated. Phosphate buffer saline (PBS) was used as the control. Under the same HIFU parameters, the quantitative echo intensity of B-mode ultrasound image and the volume of coagulative necrosis in lipid NBs groups were significantly higher and larger than that in PBS groups, but could not be demonstrated a difference to that in SonoVue MBs groups both ex vivo and in vivo. These results showed that the synergistic effect of lipid NBs for HIFU thermal ablation were similar with that of SonoVue MBs, and further indicate that lipid NBs could potentially become an enhancer for HIFU thermal ablation of tumors.

High-intensity focused ultrasound (HIFU) for pancreatic carcinoma: evaluation of feasibility, reduction of tumour volume and pain intensity

OBJECTIVES

Prognosis of patients with locally advanced pancreatic adenocarcinoma is extremely poor. They often suffer from cancer-related pain reducing their quality of life. This prospective observational study aimed to evaluate feasibility, local tumour response, and changes in quality of life and symptoms in Caucasian patients with locally advanced pancreatic cancer treated by ultrasound-guided high-intensity focused ultrasound (HIFU).

METHODS

Thirteen patients underwent HIFU, five with stage III, eight with stage IV UICC disease. Ten patients received simultaneous palliative chemotherapy. Postinterventional clinical assessment included evaluation of quality of life and symptom changes using standardized questionnaires. CT and MRI follow-up evaluated the local tumour response.

RESULTS

HIFU was successfully performed in all patients. Average tumour reduction was 34.2 % at 6 weeks and 63.9 % at 3 months. Complete or partial relief of cancer-related pain was achieved in 10 patients (77 %), five of whom required less analgesics for pain control. Quality of life was improved revealing increased global health status and alleviated symptoms. HIFU treatment was well tolerated. Eight patients experienced transient abdominal pain directly after HIFU.

CONCLUSIONS

HIFU ablation of pancreatic carcinoma is a feasible, safe and effective treatment with a crucial benefit in terms of reduction of tumour volume and pain intensity.

KEY POINTS

• US-guided HIFU is feasible and safe for patients with unresectable pancreatic cancer. • HIFU can considerably reduce tumour volume and cancer-related pain. • Patients treated with HIFU experienced significant and lasting reduction of pain intensity. • HIFU has a crucial clinical benefit for patients with pancreatic cancer.

Cyclooxygenase-2 or tumor necrosis factor-α inhibitors attenuate the mechanotransductive effects of pulsed focused ultrasound to suppress mesenchymal stromal cell homing to healthy and dystrophic muscle

Maximal homing of infused stem cells to diseased tissue is critical for regenerative medicine. Pulsed focused ultrasound (pFUS) is a clinically relevant platform to direct stem cell migration. Through mechanotransduction, pFUS establishes local gradients of cytokines, chemokines, trophic factors (CCTF) and cell adhesion molecules (CAM) in treated skeletal muscle that subsequently infused mesenchymal stromal cells (MSC) can capitalize to migrate into the parenchyma. Characterizing molecular responses to mechanical pFUS effects revealed tumor necrosis factor-alpha (TNFα) drives cyclooxygenase-2 (COX2) signaling to locally increase CCTF/CAM that are necessary for MSC homing. pFUS failed to increase chemoattractants and induce MSC homing to treated muscle in mice pretreated with ibuprofen (nonspecific COX inhibitor) or etanercept (TNFα inhibitor). pFUS-induced MSC homing was also suppressed in COX2-knockout mice, demonstrating ibuprofen blocked the mechanically induced CCTF/CAM by acting on COX2. Anti-inflammatory drugs, including ibuprofen, are administered to muscular dystrophy (MD) patients, and ibuprofen also suppressed pFUS-induced homing to muscle in a mouse model of MD. Drug interactions with cell therapies remain unexplored and are not controlled for during clinical cell therapy trials. This study highlights potentially negative drug-host interactions that suppress stem cell homing and could undermine cell-based approaches for regenerative medicine.

Clinical Application of High-intensity Focused Ultrasound in Cancer Therapy

The treatment of cancer is an important issue in both developing and developed countries. Clinical use of ultrasound in cancer is not only for the diagnosis but also for the treatment. Focused ultrasound surgery (FUS) is a noninvasive technique. By using the combination of high-intensity focused ultrasound (HIFU) and imaging method, FUS has the potential to ablate tumor lesions precisely. The main mechanisms of HIFU ablation involve mechanical and thermal effects. Recent advances in HIFU have increased its popularity. Some promising results were achieved in managing various malignancies, including pancreas, prostate, liver, kidney, breast and bone. Other applications include brain tumor ablation and disruption of the blood-brain barrier. We aim at briefly outlining the clinical utility of FUS as a noninvasive technique for a variety of types of cancer treatment.

Treatment of Osteoid Osteomas Using a Navigational Bipolar Radiofrequency Ablation System

BACKGROUND

Percutaneous CT-guided radiofrequency ablation is a safe and effective minimally invasive treatment for osteoid osteomas. This technical case series describes the use of a recently introduced ablation system with a probe that can be curved in multiple directions, embedded thermocouples for real-time monitoring of the ablation volume, and a bipolar design that obviates the need for a grounding pad.

METHODS

Medical records of all patients who underwent radiofrequency ablation of an osteoid osteoma with the STAR Tumor Ablation System (DFINE; San Jose, CA) were reviewed. The location of each osteoid osteoma, nidus volume, and procedural details were recorded. Treatment efficacy and long-term complications were assessed at clinical follow-up.

RESULTS

During the study period, 18 osteoid osteomas were radiofrequency ablated with the multidirectional bipolar system. Lesion locations included the femur (50%; 9/18), tibia (22%; 4/18), cervical spine (11%; 2/18), calcaneus (5.5%; 1/18), iliac bone (5.5%; 1/18), and fibula (5.5%; 1/18). The median nidus volume of these cases was 0.33 mL (range 0.12-2.0 mL). All tumors were accessed via a single osseous channel. Median cumulative ablation time was 5 min and 0 s (range 1 min and 32 s-8 min and 50 s). All patients with clinical follow-up reported complete symptom resolution. No complications occurred.

CONCLUSION

Safe and effective CT-guided radiofrequency ablation of osteoid osteomas can be performed in a variety of locations using a multidirectional bipolar system.

Three cases of complications after high-intensity focused ultrasound treatment in unmarried women

High-intensity focused ultrasound (HIFU) has been regarded as a non-surgical, minimally invasive therapeutic option for patients who prioritize uterus-conservation. Although many studies have shown that HIFU therapy is a safe and effective treatment of uterine fibroid, not all fibroids are suitable for HIFU due to risks of serious complications. We experienced three cases of complications after the HIFU ablation for huge uterine fibroids, including two cases of rapid myoma enlargement and one case of heavy vaginal bleeding.

Cluster analysis of DCE-MRI data identifies regional tracer-kinetic changes after tumor treatment with high intensity focused ultrasound

Evaluation of high intensity focused ultrasound (HIFU) treatment with MRI is generally based on assessment of the non-perfused volume from contrast-enhanced T1-weighted images. However, the vascular status of tissue surrounding the non-perfused volume has not been extensively investigated with MRI. In this study, cluster analysis of the transfer constant K(trans) and extravascular extracellular volume fraction ve , derived from dynamic contrast-enhanced MRI (DCE-MRI) data, was performed in tumor tissue surrounding the non-perfused volume to identify tumor subregions with distinct contrast agent uptake kinetics. DCE-MRI was performed in CT26.WT colon carcinoma-bearing BALB/c mice before (n = 12), directly after (n = 12) and 3 days after (n = 6) partial tumor treatment with HIFU. In addition, a non-treated control group (n = 6) was included. The non-perfused volume was identified based on the level of contrast enhancement. Quantitative comparison between non-perfused tumor fractions and non-viable tumor fractions derived from NADH-diaphorase histology showed a stronger agreement between these fractions 3 days after treatment (R(2) to line of identity = 0.91) compared with directly after treatment (R(2) = 0.74). Next, k-means clustering with four clusters was applied to K(trans) and ve parameter values of all significantly enhanced pixels. The fraction of pixels within two clusters, characterized by a low K(trans) and either a low or high ve , significantly increased after HIFU. Changes in composition of these clusters were considered to be HIFU induced. Qualitative H&E histology showed that HIFU-induced alterations in these clusters may be associated with hemorrhage and structural tissue disruption. Combined microvasculature and hypoxia staining suggested that these tissue changes may affect blood vessel functionality and thereby tumor oxygenation. In conclusion, it was demonstrated that, in addition to assessment of the non-perfused tumor volume, the presented methodology gives further insight into HIFU-induced effects on tumor vascular status. This method may aid in assessment of the consequences of vascular alterations for the fate of the tissue.

Application of analyzer based X-ray imaging technique for detection of ultrasound induced cavitation bubbles from a physical therapy unit

BACKGROUND

The observation of ultrasound generated cavitation bubbles deep in tissue is very difficult. The development of an imaging method capable of investigating cavitation bubbles in tissue would improve the efficiency and application of ultrasound in the clinic. Among the previous imaging modalities capable of detecting cavitation bubbles in vivo, the acoustic detection technique has the positive aspect of in vivo application. However the size of the initial cavitation bubble and the amplitude of the ultrasound that produced the cavitation bubbles, affect the timing and amplitude of the cavitation bubbles' emissions.

METHODS

The spatial distribution of cavitation bubbles, driven by 0.8835 MHz therapeutic ultrasound system at output power of 14 Watt, was studied in water using a synchrotron X-ray imaging technique, Analyzer Based Imaging (ABI). The cavitation bubble distribution was investigated by repeated application of the ultrasound and imaging the water tank. The spatial frequency of the cavitation bubble pattern was evaluated by Fourier analysis. Acoustic cavitation was imaged at four different locations through the acoustic beam in water at a fixed power level. The pattern of cavitation bubbles in water was detected by synchrotron X-ray ABI.

RESULTS

The spatial distribution of cavitation bubbles driven by the therapeutic ultrasound system was observed using ABI X-ray imaging technique. It was observed that the cavitation bubbles appeared in a periodic pattern. The calculated distance between intervals revealed that the distance of frequent cavitation lines (intervals) is one-half of the acoustic wave length consistent with standing waves.

CONCLUSION

This set of experiments demonstrates the utility of synchrotron ABI for visualizing cavitation bubbles formed in water by clinical ultrasound systems working at high frequency and output powers as low as a therapeutic system.

Fluorocarbon nanodrops as acoustic temperature probes

This work investigated the use of superheated fluorocarbon nanodrops for ultrasound thermal imaging and the use of mixed fluorocarbons for tuning thermal and acoustic thresholds for vaporization. Droplets were fabricated by condensing phospholipid-coated microbubbles containing C3F8 and C4F10 mixed at various molar ratios. Vaporization temperatures first were measured in a closed system by optical transmission following either isothermal pressure release or isobaric heating. The vaporization temperature was found to depend linearly on the percentage of C4F10 in the droplet core, indicating excellent tunability under these fluorocarbon-saturated conditions. Vaporization temperatures were then measured in an open system using contrast-enhanced ultrasound imaging, where it was found that the mixed droplets behaved like pure C4F10 drops. Additionally, the critical mechanical index for vaporization was measured at the limits of therapeutic hyperthermia (37 and 60 °C), and again the mixed droplets were found to behave like pure C4F10 drops. These results suggested that C3F8 preferentially dissolves out of the droplet core in open systems, as shown by a simple mass transfer model of multicomponent droplet dissolution. Finally, proof-of-concept was shown that pure C4F10 nanodrops can be used as an acoustic temperature probe. Overall, these results not only demonstrate the potential of superheated fluorocarbon emulsions for sonothermetry but also point to the limits of tunability for fluorocarbon mixtures owing to preferential release of the more soluble species to the atmosphere.

Using passive cavitation images to classify high-intensity focused ultrasound lesions

Passive cavitation imaging provides spatially resolved monitoring of cavitation emissions. However, the diffraction limit of a linear imaging array results in relatively poor range resolution. Poor range resolution has limited prior analyses of the spatial specificity and sensitivity of passive cavitation imaging in predicting thermal lesion formation. In this study, this limitation is overcome by orienting a linear array orthogonal to the high-intensity focused ultrasound propagation direction and performing passive imaging. Fourteen lesions were formed in ex vivo bovine liver samples as a result of 1.1-MHz continuous-wave ultrasound exposure. The lesions were classified as focal, "tadpole" or pre-focal based on their shape and location. Passive cavitation images were beamformed from emissions at the fundamental, harmonic, ultraharmonic and inharmonic frequencies with an established algorithm. Using the area under a receiver operating characteristic curve (AUROC), fundamental, harmonic and ultraharmonic emissions were found to be significant predictors of lesion formation for all lesion types. For both harmonic and ultraharmonic emissions, pre-focal lesions were classified most successfully (AUROC values of 0.87 and 0.88, respectively), followed by tadpole lesions (AUROC values of 0.77 and 0.64, respectively) and focal lesions (AUROC values of 0.65 and 0.60, respectively).

Using the Promise of Sonodynamic Therapy in the Clinical Setting against Disseminated Cancers

Sonodynamic therapy (SDT) is a form of ultrasound therapy in which specialized chemotherapeutic agents known as sonosensitizers are administered to increase the efficacy of ultrasound-mediated preferential damage of neoplastic cells. Multiple in vitro and in vivo studies have indicated that SDT has the ability to exhibit profound physical and chemical changes on cellular structure. As supportive as the data have been, assessment of this method at the clinical level has been limited to only solid tumors. Although SDT has shown efficacy against multiple adherent neoplastic cell lines, it has also shown particular promise with leukemia-derived cell lines. Potential procedures to administer SDT to leukemia patients are heating the appendages as ultrasound is applied to these areas (Heat and Treat), using an ultrasound probe to scan the body for malignant growths (Target and Destroy), and extracorporeal blood sonication (EBS) through dialysis. Each method offers a unique set of benefits and concerns that will need to be evaluated in preclinical mammalian models of malignancy before clinical examination can be considered.

Hyperthermia approaches for enhanced delivery of nanomedicines to solid tumors

Drug delivery to solid tumors has received much attention in order to reduce harmful side effects and improve the efficacy of treatment. Different strategies have been utilized with nanoparticle drug delivery systems, or nanomedicines, including passive and active targeting strategies, as well as the incorporation of stimuli sensitivity. Additionally, hyperthermia has been used in combination with such systems to further improve accumulation, localization, penetration, and subsequently efficacy. Localized hyperthermia within the solid tumor tissue can be applied through different mechanisms able to trigger vascular and cellular mechanisms for enhanced delivery of nanomedicines. This review covers the use of nanoparticles in drug delivery, the different methods for inducing localized hyperthermia, combination effects of hyperthermia, and successful strategies for improving the delivery of nanomedicines using hyperthermia.

MRI methods for the evaluation of high intensity focused ultrasound tumor treatment: Current status and future needs

Thermal ablation with high intensity focused ultrasound (HIFU) is an emerging noninvasive technique for the treatment of solid tumors. HIFU treatment of malignant tumors requires accurate treatment planning, monitoring and evaluation, which can be facilitated by performing the procedure in an MR-guided HIFU system. The MR-based evaluation of HIFU treatment is most often restricted to contrast-enhanced T1 -weighted imaging, while it has been shown that the non-perfused volume may not reflect the extent of nonviable tumor tissue after HIFU treatment. There are multiple studies in which more advanced MRI methods were assessed for their suitability for the evaluation of HIFU treatment. While several of these methods seem promising regarding their sensitivity to HIFU-induced tissue changes, there is still ample room for improvement of MRI protocols for HIFU treatment evaluation. In this review article, we describe the major acute and delayed effects of HIFU treatment. For each effect, the MRI methods that have been-or could be-used to detect the associated tissue changes are described. In addition, the potential value of multiparametric MRI for the evaluation of HIFU treatment is discussed. The review ends with a discussion on future directions for the MRI-based evaluation of HIFU treatment.

New approach for local cancer treatment using pulsed high-intensity focused ultrasound and phase-change nanodroplets

PURPOSE

The aim of this study was to investigate the combination effects of pulsed HIFU (pHIFU) and phase-change nanodroplets (PCND) as a sensitizer on efficient induction of mechanical effects of pHIFU and chemically enhanced tumor growth inhibition for local anti-tumor therapy.

METHOD

Changes in growth of colon 26 tumor tissue inoculated onto CDF1 mice were evaluated by the following treatments. (1) pHIFU exposure (1.1 MHz, 3.2 kW/cm(2), 300 cycles, and 50 ms interval) for 60 s, (2) PCND (1 %) injection, (3) adriamycin (4 mg/kg) injection, (4) pHIFU exposure after PCND injection, and (5) pHIFU exposure after PCND + adriamycin injection simultaneously.

RESULTS

Significant changes in tumor growth were observed in the group with combination of pHIFU and PCND, although single therapy did not show any significant difference. PCND enhanced mechanical tissue fractionation by pHIFU, which was detectable by Real-time tissue elastography. Moreover, the combination of pHIFU and PCND + Adriamycin suppressed the tumor growth for 2 weeks, and 3 of 4 mice did not show any sign of regrowth during the 30-day observation.

CONCLUSION

The combination of pHIFU and PCND exerted a significant anti-tumor effect and may be a new candidate for treatment of locally advanced cancer.

Complementary and alternative medicine for the treatment of obesity: a critical review

CONTEXT

Obesity and its associated morbidities pose a major health hazard to the public. Despite a multiplex of available diet and exercise programs for losing and maintaining weight, over the past years, interest in the use of complementary and alternative medicine (CAM) for obesity treatment has greatly increased.

EVIDENCE ACQUISITION

We searched PubMed, Google scholar and the Cochrane databases for systemic reviews, review articles, meta-analysis and randomized clinical trials up to December 2013.

RESULTS

In this review, the efficacy and safety of the more commonly used CAM methods for the treatment of obesity, namely herbal supplements, acupuncture, and non-invasive body-contouring, are briefly discussed. The evidence supporting the effectiveness and safety of these methods is either lacking or point to a negligible clinical benefit, barely surpassing that of the placebo. Furthermore, several limitations are observed in the available scientific literature. These shortcomings include, without being limited to, uncontrolled trial designs, non-random allocation of subjects to treatment arms, small number of patients enrolled, short durations of follow-up, and ambiguous clinical and laboratory endpoints.

CONCLUSIONS

Further investigations are necessary to accurately determine the efficacy, safety, standard dosage/procedure, and potential side effects of the various CAM methods currently in use.

Thermal ablative treatment of uterine fibroids

In addition to surgical methods of treating uterine fibroids, numerous non-invasive treatments have been developed. Many of these involve the use of hyperthermia, the heating of tissue by a variety of methods. These include the use of lasers, radiofrequency, microwave energy and high intensity focused ultrasound, guided by both ultrasound and magnetic resonance imaging. In this review we examine the technology behind these treatment modalities and review the current evidence for their use.

Traumatic intra-abdominal hemorrhage control: has current technology tipped the balance toward a role for prehospital intervention?

BACKGROUND

The identification and control of traumatic hemorrhage from the torso remains a major challenge and carries a significant mortality despite the reduction of transfer times. This review examines the current technologies that are available for abdominal hemorrhage control within the prehospital setting and evaluates their effectiveness.

METHODS

A systematic search of online databases was undertaken. Where appropriate, evidence was highlighted using the Oxford levels of clinical evidence. The primary outcome assessed was mortality, and secondary outcomes included blood loss and complications associated with each technique.

RESULTS

Of 89 studies, 34 met the inclusion criteria, of which 29 were preclinical in vivo trials and 5 were clinical. Techniques were subdivided into mechanical compression, endovascular control, and energy-based hemostatic devices. Gas insufflation and manual pressure techniques had no associated mortalities. There was one mortality with high intensity focused ultrasound. The intra-abdominal infiltration of foam treatment had 64% and the resuscitative endovascular balloon occlusion of the aorta had 74% mortality risk reduction. In the majority of cases, morbidity and blood loss associated with each interventional procedure were less than their respective controls.

CONCLUSION

Mortality from traumatic intra-abdominal hemorrhage could be reduced through early intervention at the scene by emerging technology. Manual pressure or the resuscitative endovascular balloon occlusion of the aorta techniques have demonstrated clinical effectiveness for the control of major vessel bleeding, although complications need to be carefully considered before advocating clinical use. At present, fast transfer to the trauma center remains paramount.

LEVEL OF EVIDENCE

Systematic review, level IV.

Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review

Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials' behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers.

Acoustic power measurement of high-intensity focused ultrasound transducer using a pressure sensor

The acoustic power of high-intensity focused ultrasound (HIFU) is an important parameter that should be measured prior to each treatment to guarantee effective and safe outcomes. A new calibration technique was developed that involves estimating the pressure distribution, calculating the acoustic power using an underwater pressure blast sensor, and compensating the contribution of harmonics to the acoustic power. The output of a clinical extracorporeal HIFU system (center frequency of ~1 MHz, p+ = 2.5-57.2 MPa, p(-) = -1.8 to -13.9 MPa, I(SPPA) = 513-22,940 W/cm(2), -6 dB size of 1.6 × 10 mm: lateral × axial) was measured using this approach and then compared with that obtained using a radiation force balance. Similarities were found between each method at acoustic power ranging from 18.2 W to 912 W with an electrical-to-acoustic conversion efficiency of ~42%. The proposed method has advantages of low weight, smaller size, high sensitivity, quick response, high signal-to-noise ratio (especially at low power output), robust performance, and easy operation of HIFU exposimetry measurement.

Ultrasound-guided high-intensity focused ultrasound treatment of breast fibroadenoma-a multicenter experience

Background

The aim of our multicenter study was to assess the clinical outcome and safety of ultrasound (US)-guided high-intensity focused ultrasound (HIFU) in patients with breast fibroadenoma (FA).

Methods

From May 2011 to February 2013, 42 women with 51 FA in one or both breasts were selected for treatment with US-guided HIFU. Eight of 51 FA were treated twice. Patients’ age ranged from 16 to 52 years (mean 32 years). All patients with FA underwent core needle biopsy with histological confirmation. HIFU treatment was performed as an outpatient procedure under conscious sedation. Exclusion criteria were pregnant or lactating women, microcalcifications within the lesion at mammogram, history of breast cancer, previous laser or radiation therapy, and breast implant in the same breast. All patients signed written informed consent. After the treatment, follow-up US with volume evaluation was performed at 2, 6, and 12 months.

Results

The FA mean baseline volume was 3.89 ml (0.34–19.66 ml). At 2-month follow-up, the mean volume reduction was 33.2% ± 19.1% and achieved significance at 6-month (59.2% ± 18.2%, p < 0.001) and 12-month (72.5% ± 16.7%, p < 0.001) follow-up. Related side effects as superficial skin burn with blister-like aspect in three patients and hyperpigmentation over the treated area in one patient were transient and resolved spontaneously. In one patient, asymptomatic subcutaneous induration persisted at the end of the study.

Conclusions

US-guided HIFU treatment is an effective noninvasive method for the treatment of breast FA and well tolerated by the patients. Preliminary results are encouraging and show that HIFU could be an alternative to surgery for breast FA.

Clinician-performed ultrasound in hemodynamic and cardiac assessment: a synopsis of current indications and limitations

Accurate hemodynamic and intravascular volume status assessment is essential in the diagnostic and therapeutic management of critically ill patients. Over the last two decades, a number of technological advances were translated into a variety of minimally invasive or non-invasive hemodynamic monitoring modalities. Despite the promise of less invasive technologies, the quality, reliability, reproducibility, and generalizability of resultant hemodynamic and intravascular volume status data have been lacking. Since its formal introduction, ultrasound technology has provided the medical community with a more standardized, higher quality, broadly applicable, and reproducible method of accomplishing the above-mentioned objectives. With the advent of portable, hand-carried devices, the importance of sonography in hemodynamic and volume status assessment became clear. From basic venous collapsibility and global cardiac assessment to more complex tasks such as the assessment of cardiac flow and tissue Doppler signals, the number of real-life indications for sonology continues to increase. This review will provide an outline of the essential ultrasound applications in hemodynamic and volume status assessment, focusing on evidence-based uses and indications.

Therapeutic ultrasound for glaucoma: clinical use of a low-frequency low-power ultrasound device for lowering intraocular pressure

BACKGROUND

This is a first-in-human study to determine the efficacy and tolerability of a new method of treating glaucoma using a low-power, low-frequency, focused therapeutic ultrasound for glaucoma (TUG) device designed to trigger an inflammatory reaction in the anterior chamber angle and trabecular meshwork to enhance outflow. The use of the device is anticipated for mild or moderate open-angle glaucoma as an enhancement to outflow.

METHODS

In a two-branch clinical trial, a total of 26 primary open-angle glaucoma patients underwent a procedure consisting of the external application of the TUG device. In branch 1, nine of these patients were naïve to pharmaceutical treatment or had been off of medication for over 6 months. In branch 2, 17 patients were treated after a medication washout period. All patients in the study were followed for 12 months.

RESULTS

In branch 1, there was a decrease in intraocular pressure averaging over 20% lasting at least a year in 74% of the eyes with non-normotensive open-angle glaucoma. In branch 2, an average of two visits while on medication provided the comparison intraocular pressure (IOP) to the effect of the TUG treatment after washout. It was seen that the intraocular pressure over the year post-treatment was equal to or better than the pharmaceutical control in close to 80% of measurements.

CONCLUSION

A novel device for lowering intraocular pressure is described with a potential for adding to our armamentarium for treating glaucoma. This is a small cohort study which indicates beneficial trends.

TRIAL REGISTRATION NUMBER

The study was a registered clinical trial, #ISRCTN50904302.

Transsclera Drug Delivery by Pulsed High-Intensity Focused Ultrasound (HIFU): An Ex Vivo Study

PURPOSE/AIM OF STUDY: Drug delivery to the ocular posterior segment is of importance, but it is a challenge in the treatment of irreversible blindness disease, such as age-related macular degeneration. Although some methods (i.e. intraocular injection, sustained release by polymer and iontophoresis) have been applied, some technical drawbacks, such as slow rate and damage to the eye, need to be overcome for wide use.

MATERIALS AND METHODS

In this study, the feasibility of high-intensity focused ultrasound (HIFU) to enhance the transsclera drug delivery was tested for the first time. One-hundred HIFU pulses with the driving frequency of 1.1 MHz, acoustic power of 105.6 W, pulse duration of 10-50 ms and pulse repetition frequency of 1 Hz were delivered to the fresh ex vivo porcine sclera specimen.

RESULTS

In comparison to the passive diffusion (control), 50-ms HIFU can increase the penetration depth by 2.0 folds (501.7 ± 126.4 µm versus 252.4 ± 29.2 µm) using bicinchoninic acid assay and Rhodamine 6 G fluorescence intensity by 3.1 folds (22.4 ± 12.3 versus 7.1 ± 4.1) and coverage area by 2.6 folds (40.4 ± 9.1% versus 15.8 ± 2.9%). No morphological changes on the sonicated sclera samples were found using a surface electron microscope.

CONCLUSIONS

In summary, pulsed-HIFU may be an effective modality in the transsclera drug delivery with a high transporting rate and depth. In vivo studies are necessary to further evaluate its performance, including the drug penetration and its possible side effects.

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.

Novel use of noninvasive high-intensity focused ultrasonography for intercostal nerve neurolysis in a swine model

BACKGROUND

High-intensity focused ultrasound (HIFU) is a noninvasive thermal ablation technique. High-intensity focused ultrasound has been used in small-animal models to lesion neural tissue selectively. This study aimed to evaluate the efficacy of HIFU in a large-animal model for ablation of nerves similar in size to human nerves.

METHODS

Twelve acute magnetic resonance-guided HIFU ablation lesions were created in intercostal nerves in a swine model. In a second pig, as a control, 4 radiofrequency ablation and 4 alcohol lesions were performed on intercostal nerves under ultrasound guidance. Preprocedural and postprocedural magnetic resonance imaging was then performed to evaluate radiologically the lesion size created by HIFU. Animals were euthanized 1 hour postprocedure, and necropsy was performed to collect tissue samples for histopathologic analysis.

RESULTS

On gross and histological examination of the intercostal nerve, acute HIFU nerve lesions showed evidence of well-demarcated, acute, focally extensive thermal necrosis. Four intercostal nerves ablated with HIFU were sent for histopathologic analysis, with 2 of 4 lesions showing pathologic damage to the intercostal nerve. Similar results were shown with radiofrequency ablation technique, whereas the intercostal nerves appeared histologically intact with alcohol ablation.

CONCLUSIONS

High-intensity focused ultrasound may be used as a noninvasive neurolytic technique in swine. High-intensity focused ultrasound may have potential as a neuroablation technique for patients with chronic and cancer pain.

Alternative therapies in management of leiomyomas

Leiomyomas are benign soft-tissue neoplasms that arise from smooth muscle. Relief of symptoms (abnormal uterine bleeding, pain, pressure) is the major goal in management of women with significant symptoms. For symptomatic myomas, hysterectomy is a definitive solution; however, there are emerging less-invasive options. Magnetic resonance imaging-guided focused ultrasound surgery, cryomyolysis, and temporary occlusion of the uterine arteries are treatment options that are minimally invasive interventions with the benefit of preserving the uterus. This review summarizes procedure techniques, eligibility, complications, and outcomes of these alternate therapies.

Tumor ablation: common modalities and general practices

Tumor ablation is a minimally invasive technique that is commonly used in the treatment of tumors of the liver, kidney, bone, and lung. During tumor ablation, thermal energy is used to heat or cool tissue to cytotoxic levels (less than -40°C or more than 60°C). An additional technique is being developed that targets the permeability of the cell membrane and is ostensibly nonthermal. Within the classification of tumor ablation, there are several modalities used worldwide: radiofrequency, microwave, laser, high-intensity focused ultrasound, cryoablation, and irreversible electroporation. Each technique, although similar in purpose, has specific and optimal indications. This review serves to discuss general principles and technique, reviews each modality, and discusses modality selection.

High-intensity focused ultrasound treatment for advanced pancreatic cancer

Pancreatic cancer is under high mortality but has few effective treatment modalities. High-intensity focused ultrasound (HIFU) is becoming an emerging approach of noninvasively ablating solid tumor in clinics. A variety of solid tumors have been tried on thousands of patients in the last fifteen years with great success. The principle, mechanism, and clinical outcome of HIFU were introduced first. All 3022 clinical cases of HIFU treatment for the advanced pancreatic cancer alone or in combination with chemotherapy or radiotherapy in 241 published papers were reviewed and summarized for its efficacy, pain relief, clinical benefit rate, survival, Karnofsky performance scale (KPS) score, changes in tumor size, occurrence of echogenicity, serum level, diagnostic assessment of outcome, and associated complications. Immune response induced by HIFU ablation may become an effective way of cancer treatment. Comments for a better outcome and current challenges of HIFU technology are also covered.

Preparation of nanobubbles carrying androgen receptor siRNA and their inhibitory effects on androgen-independent prostate cancer when combined with ultrasonic irradiation

Objective

The objective of this study was to investigate nanobubbles carrying androgen receptor (AR) siRNA and their in vitro and in vivo anti-tumor effects, when combined with ultrasonic irradiation, on androgen-independent prostate cancer (AIPC).

Materials and Methods

Nanobubbles carrying AR siRNA were prepared using poly-L-lysine and electrostatic adsorption methods. Using C4-2 cell activity as a testing index, the optimal irradiation parameters (including the nanobubble number/cell number ratio, mechanical index [MI], and irradiation time) were determined and used for transfection of three human prostate cancer cell lines (C4-2, LNCaP, and PC-3 cells). The AR expression levels were investigated with RT-PCR and Western blot analysis. Additionally, the effects of the nanobubbles and control microbubbles named SonoVue were assessed via imaging in a C4-2 xenograft model. Finally, the growth and AR expression of seven groups of tumor tissues were assessed using the C4-2 xenograft mouse model.

Results

The nanobubbles had an average diameter of 609.5±15.6 nm and could effectively bind to AR siRNA. Under the optimized conditions of a nanobubble number/cell number ratio of 100∶1, an MI of 1.2, and an irradiation time of 2 min, the highest transfection rates in C4-2, LNCaP, and PC-3 cells were 67.4%, 74.0%, and 63.96%, respectively. In the C4-2 and LNCaP cells, treatment with these binding nanobubbles plus ultrasonic irradiation significantly inhibited cell growth and resulted in the suppression of AR mRNA and protein expression. Additionally, contrast-enhanced ultrasound showed that the nanobubbles achieved stronger signals than the SonoVue control in the central hypovascular area of the tumors. Finally, the anti-tumor effect of these nanobubbles plus ultrasonic irradiation was most significant in the xenograft tumor model compared with the other groups.

Conclusion

Nanobubbles carrying AR siRNA could be potentially used as gene vectors in combination with ultrasonic irradiation for the treatment of AIPC.

A case-control study of high-intensity focused ultrasound combined with sonographically guided intratumoral ethanol injection in the treatment of uterine fibroids

OBJECTIVES

The purpose of this study was to explore the feasibility of high-intensity focused ultrasound combined with sonographically guided intratumoral ethanol injection in the treatment of uterine fibroids and to compare its therapeutic effects and potential side effects with those of simple high-intensity focused ultrasound treatment.

METHODS

Forty patients with uterine fibroids from the Department of Ultrasonography in our hospital were randomly divided into 2 groups of the same size: group H, which only underwent high-intensity focused ultrasound treatment; and group H + A, which underwent sonographically guided intratumoral ethanol injection therapy first and then high-intensity focused ultrasound treatment the following day. The treatment times, treatment doses, pain scores, side effects, and therapeutic effect rates of the groups were then recorded and compared.

RESULTS

Both the treatment time and dose of group H + A were significantly less than those of group H, and the differences were statistically significant (P < .05). A lower pain score and fewer side effects were achieved in group H + A, also with statistically significant differences (P < .05). The therapeutic effect rate of group H + A was also higher than that of group H, and the difference was also statistically significant (P < .05).

CONCLUSIONS

In the treatment of uterine fibroids, high-intensity focused ultrasound combined with sonographically guided intratumoral ethanol injection requires less treatment time and a lower dose than simple high-intensity focused ultrasound treatment and significantly reduces the pain and side effects commonly experienced by patients. High-intensity focused ultrasound combined with sonographically guided intratumoral ethanol injection is a feasible, safe, and more effective way to treat patients with uterine fibroids.

MR-guided focused ultrasound surgery, present and future

MR-guided focused ultrasound surgery (MRgFUS) is a quickly developing technology with potential applications across a spectrum of indications traditionally within the domain of radiation oncology. Especially for applications where focal treatment is the preferred technique (for example, radiosurgery), MRgFUS has the potential to be a disruptive technology that could shift traditional patterns of care. While currently cleared in the United States for the noninvasive treatment of uterine fibroids and bone metastases, a wide range of clinical trials are currently underway, and the number of publications describing advances in MRgFUS is increasing. However, for MRgFUS to make the transition from a research curiosity to a clinical standard of care, a variety of challenges, technical, financial, clinical, and practical, must be overcome. This installment of the Vision 20∕20 series examines the current status of MRgFUS, focusing on the hurdles the technology faces before it can cross over from a research technique to a standard fixture in the clinic. It then reviews current and near-term technical developments which may overcome these hurdles and allow MRgFUS to break through into clinical practice.

An ex vivo human lung model for ultrasound-guided high-intensity focused ultrasound therapy using lung flooding

The usability of an ex vivo human lung model for ablation of lung cancer tissue with high-intensity focused ultrasound (HIFU) is described. Lung lobes were flooded with saline, with no gas remaining after complete atelectasis. The tumor was delineated sono-morphologically. Speed of sound, tissue density and ultrasound attenuation were measured for flooded lung and different pulmonary cancer tissues. The acoustic impedance of lung cancer tissue (1.6-1.9 mega-Rayleighs) was higher than that of water, as was its attenuation coefficient (0.31-0.44 dB/cm/MHz) compared with that of the flooded lung (0.12 dB/cm/MHz). After application of HIFU, the temperature in centrally located lung cancer surrounded by the flooded lung increased as high as 80°C, which is sufficient for treatment. On the basis of these preliminary results, ultrasound-guided HIFU ablation of lung cancer, by lung flooding with saline, appears feasible and should be explored in future clinical studies.

Characterization of a setup to test the impact of high-amplitude pressure waves on living cells

The impact of pressure waves on cells may provide several possible applications in biology and medicine including the direct killing of tumors, drug delivery or gene transfection. In this study we characterize the physical properties of mechanical pressure waves generated by a nanosecond laser pulse in a setup with well-defined cell culture conditions. To systematically characterize the system on the relevant length and time scales (micrometers and nanoseconds) we use photon Doppler velocimetry (PDV) and obtain velocity profiles of the cell culture vessel at the passage of the pressure wave. These profiles serve as input for numerical pressure wave simulations that help to further quantify the pressure conditions on the cellular length scale. On the biological level we demonstrate killing of glioblastoma cells and quantify experimentally the pressure threshold for cell destruction.