Ultrasonic Nakagami Imaging of High-intensity Focused Ultrasound-induced Thermal Lesions in Porcine Livers: Ex Vivo Study

High-intensity focused ultrasound (HIFU) has demonstrated the capacity to be used for local thermal ablation in clinical surgery; however, relying solely on conventional ultrasound B-mode imaging to monitor HIFU thermal ablation and determine ablation levels remains a challenge. Here, we experimentally demonstrate the ability to use Nakagami imaging to monitor HIFU-induced thermal lesions in porcine livers ex vivo. Ultrasonic Nakagami imaging has been proven to be able to characterize tissues with different scatterer concentrations and distributions. The pathological sections from HIFU thermally ablated porcine liver tissues reveal that normal and denatured tissues significantly differ in scatterer concentration and distribution. Therefore, we believe that Nakagami imaging can be used to monitor thermal ablation by tracing Nakagami parameter changes in liver tissues. The ex vivo porcine liver experiments were performed using a homemade HIFU device synchronized with a commercial diagnostic ultrasound scanner to obtain the ultrasound envelope data before and after thermal ablation. These data were used to evaluate the performance of thermal lesion characterization using Nakagami imaging and were compared with those derived from conventional B-mode imaging. Experimental results showed that Nakagami imaging can be used to identify thermal lesions, which are difficult to visualize using conventional B-mode imaging because there is no apparent bubble formation. In cases with apparent bubble formation, Nakagami imaging could provide a more accurate estimation of lesion size and position. In addition, the Nakagami imaging algorithm is characterized by low computational complexity, which means it can be easily integrated as postprocessing for existing array imaging systems.

High-intensity focused ultrasound therapy for the treatment of prostate cancer: Medium-term experience

INTRODUCTION

The treatment of localised prostate cancer seeks to minimise the impact on sexual function and urinary continence. In this respect, therapy with high-intensity focused ultrasound offers important results. We present our experience with this technique in 2 Spanish centres.

MATERIAL AND METHODS

We conducted a retrospective review of 75 patients with localised prostate cancer treated with high-intensity focused ultrasound between March 2007 and July 2016. The oncological results and perioperative complications were assessed, as well as the impact on sexual function and continence.

RESULTS

A total of 67 patients were analysed. The mean follow-up was 7.2 years. The PSA nadir was 0.2ng/mL (0-3), 24 patients (35.5%) presented biochemical recurrence, and 18 underwent a further biopsy, with 10 cases (55.5%) presenting disease recurrence. The overall biochemical relapse-free survival at 5 and 8 years was 93.2 and 80.5%, respectively. The cancer-specific survival at 5 and 8 years was 96% in both cases. In the postoperative period, 50 patients (74.6%) were continent, 16 (23.9%) reported mild incontinence, and one (1.5%) reported moderate incontinence. The median International Index of Erectile Function-5 before and after the surgery was 17 (5-25) and 16 (2-23) points, respectively. Nine patients reported de novo erectile dysfunction (13.5%).

CONCLUSION

High-intensity focused ultrasound appears to be a safe alternative for the treatment of localised prostate cancer, especially for low-risk localised prostate cancer. In our experience, this technique offers advantages in preserving urinary continence, and the medium-term oncological results are encouraging. Given the natural progression of prostate cancer, long-term studies with a larger number of cases are needed to corroborate these results.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration.

Histotripsy for Non-Invasive Ablation of Hepatocellular Carcinoma (HCC) Tumor in a Subcutaneous Xenograft Murine Model

Histotripsy fractionates tissue through a mechanical, non-invasive ultrasonic ablation process that precisely controls acoustic cavitation while utilizing real-time ultrasound (US) imaging guidance. This study investigates the potential, feasibility and tumor volume reduction effects of histotripsy for liver cancer ablation in a subcutaneous in vivo murine Hepatocellular Carcinoma (HCC) model. Hep3B tumors were generated in the right flanks of 14 NSG and 7 NOD-SCID mice. The mice were grouped as follows: A (acute, NSG with n=9 treatment and n=1 control), B (chronic, NSG with n=2 treatment and n=2 control) and C (chronic NODSCID, with n=6 treatment and n=1 control). Treatment was performed when the tumor diameters reached >5 mm. 1-2 cycle histotripsy pulses at 100 Hz PRF (p- >30 MPa) were delivered using a custom built 1 MHz therapy transducer attached to a motorized positioner, which scanned the transducer focus to traverse the targeted tumor volume, guided by real-time US imaging. Tumor ablation effectiveness was assessed by obtaining T1, T2 and T2* weighted MR images. Post euthanasia, treated tumor, brain, and lung tissue samples were harvested for histology. Histology of acute group A showed fractionation of targeted region with a sharp boundary separating it from untreated tissue. Groups B and C demonstrated effective tumor volume reduction post treatment on MRI as the homogenate and edema were resorbed within 23 weeks. However, as the tumor was subcutaneous, it was not possible to set adequate treatment margin and since the mice were immune-compromised, residual viable tumor cells eventually developed into tumor regrowth at 3-9 weeks after histotripsy. Groups B and C showed no signs of metastasis in the lung and brain. Our study successfully demonstrated the potential of histotripsy for non-invasive HCC ablation in a subcutaneous murine model. Additional work is ongoing to study the response of histotripsy in immune-competent orthotopic liver tumor models.

Preliminary study on Low Intensity Focused Ultrasound system For neuromodulation

A Prototype Low Intensity Focused Ultrasound for brain targeting in a rat model was developed and tested. Accordingly, were evaluated low intensity focused ultrasound accuracy and performance. By utilizing the Rat Brain, no death or necrosis of cells, it was confirmed that the energy is gathered at that targeted.

In Vivo Targeted, Responsive, and Synergistic Cancer Nanotheranostics by Magnetic Resonance Imaging-Guided Synergistic High-Intensity Focused Ultrasound Ablation and Chemotherapy

As one of the most representative noninvasive therapeutic modalities, high-intensity focused ultrasound (HIFU) has shown great promise for cancer therapy, but its low therapeutic efficacy and biosafety significantly hinder further extensive clinical translation and application. In this work, we report on the construction of a multifunctional theranostic nanoplatform to synergistically enhance the HIFU-therapeutic efficacy based on nanomedicine. A targeted and temperature-responsive theranostic nanoplatform (PFH/DOX@PLGA/Fe₃O₄-FA) has been designed and fabricated for efficient ultrasound/magnetic resonance dual-modality imaging-guided HIFU/chemo synergistic therapy. Especially, the folate was conjugated onto the surface of the nanoplatform for achieving active targeting to hepatoma cells by receptor-ligand interaction, which facilitates accumulation of the nanoplatforms into the tumor site. The integrated superparamagnetic iron oxide nanoparticles could generate the contrast enhancement in T₂-weighted magnetic resonance imaging. By virtue of the thermal effect as generated by HIFU, liquid-gas phase transition of perfluorohexane (PFH) in nanocomposites was induced to generate PFH microbubbles, which achieved the contrast-enhanced ultrasound imaging and significantly improved the HIFU ablation efficacy. The loaded anticancer drugs could be released from the nanocomposites in a controllable manner (both pH and HIFU responsiveness). These multifunctional nanocomposites have been demonstrated to efficiently suppress the tumor growth based on the enhanced and synergistic chemotherapy and HIFU ablation, providing an efficient theranostic nanoplatform for cancer treatment.

Contrast enhanced ultrasound of the prostate. New role in the evaluation of loco-regional therapy of prostate tumors

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Update on noninvasive body contouring techniques

Noninvasive body contouring is the fastest growing area of cosmetic dermatology. It entails the use of specific technology to optimize the definition, smoothness, and shape of the human body in a safe and effective manner. There are currently 4 leading modalities used for noninvasive body contouring: cryolipolysis, radiofrequency, high-intensity focused ultrasound, and laser therapy. This article provides an overview of each modality.

Passive acoustic mapping of cavitation using eigenspace-based robust Capon beamformer in ultrasound therapy

Pulse-echo imaging technique can only play a role when high intensity focused ultrasound (HIFU) is turned off due to the interference between the primary HIFU signal and the transmission pulse. Passive acoustic mapping (PAM) has been proposed as a tool for true real-time monitoring of HIFU therapy. However, the most-used PAM algorithm based on time exposure acoustic (TEA) limits the quality of cavitation image. Recently, robust Capon beamformer (RCB) has been used in PAM to provide improved resolution and reduced artifacts over TEA-based PAM, but the presented results have not been satisfactory. In the present study, we applied an eigenspace-based RCB (EISRCB) method to further improve the PAM image quality. The optimal weighting vector of the proposed method was found by projecting the RCB weighting vector onto the desired vector subspace constructed from the eigenstructure of the covariance matrix. The performance of the proposed PAM was validated by both simulations and in vitro histotripsy experiments. The results suggested that the proposed PAM significantly outperformed the conventionally used TEA and RCB-based PAM. The comparison results between pulse-echo images of the residual bubbles and cavitation images showed the potential of our proposed PAM in accurate localization of cavitation activity during HIFU therapy.

Treatment of benign thyroid nodules by high intensity focused ultrasound (HIFU) at different acoustic powers: a study on in-silico phantom

BACKGROUND

The non-surgical therapies of benign thyroid nodules are gaining momentum due to the possibility to reduce the nodule's volume and avoid surgery. As the last technique introduced, high intensity focused ultrasound allows the thermal tissue treatment by directing energy inside the targeted nodule with no invasive instruments. In the present study we applied the Food and Drug Administration high intensity focused ultrasound simulator to in-silico phantom to evaluate the effects obtained by different acoustic powers.

METHODS

The simulated layers were water and thyroid tissue. The source was a spherically curved circular transducer with radius r   = 2.3 cm generating a continuous wave beam at a frequency of 3 MHz. The focal distance was 6.5 cm. The sequence included a pulse (8 s) with acoustic power at different value from 5 to 50 W, and a cooling-off interval (32 s).

RESULTS

The use of acoustic power of 5 W allowed to achieve the threshold of temperature for coagulative necrosis (55 °C) at 1 s. The simulation with 50 W showed that temperature was significantly higher (above 300 °C) at 1 s and is maintained at high levels for a long interval.

CONCLUSION

Since 2016, we treated patients according to the present experience, and a significant reduction of nodule's volume was observed with good patent's comfort and no complications (unpublished data). Also, no anesthesia was practiced. We feel that the present data could contribute to develop a high intensity focused ultrasound therapy of benign thyroid nodules free from potential complications.

Oncological and functional outcomes of elderly men treated with HIFU vs. minimally invasive radical prostatectomy: A propensity score analysis

AIM

To assess outcomes of whole gland high-intensity focused ultrasound (HIFU) as compared with minimally-invasive radical prostatectomy (MIRP) in elderly patients.

MATERIALS & METHODS

Patients aged ≥70 years with, cT1-cT2 disease, biopsy Gleason score (GS) 3 + 3 or 3 + 4 and preoperative PSA ≤10 ng/mL were submitted to either whole-gland HIFU or MIRP. Propensity-score matching analysis was performed to ensure the baseline equivalence of groups. Follow-up visits were routinely performed assessing PSA and urinary function according to the International Continence Score (ICS) and the International Prostatic Symptoms Score (IPSS) questionnaires. Estimated rates of salvage-treatment free survival (SFS) overall-survival (OS), cancer-specific survival (CSS) and metastasis-free survival (MTS) were assessed and compared.

RESULTS

Overall, 84 (33.3%) and 168 (66.7%) patients were treated with HIFU and MIRP, respectively. MIRP was associated with a 5-yrs SFS of 93.4% compared to 74.8% for HIFU (p < 0.01). The two groups did not differ in terms of OS and MTS. No cancer-related deaths were registered. Patients treated with HIFU showed better short-term (6-mos) continence outcomes [mean-ICS: 1.7 vs. 4.8; p = 0.005] but higher IPSS mean scores at 12-mos assessment. A comparable rate of patients experiencing post-treatment Clavien-Dindo grade ≥III complications was observed within the two groups.

CONCLUSIONS

Whole-gland HIFU is a feasible treatment in elderly men with low-to intermediate-risk PCa and could be considered for patients either unfit for surgery, or willing a non-invasive treatment with a low morbidity burden, although a non-negligible risk of requiring subsequent treatment for recurrence should be expected.

Treatment of cornual pregnancy in a patient with adenomyosis by high-intensity focused ultrasound (HIFU) ablation: A case report

RATIONALE

Cornual ectopic pregnancy in adenomyosis patients is a rare clinical condition, which may require careful approach for accurate diagnosis and treatment.

PATIENT CONCERNS

A 38-year-old woman presented with amenorrhea for 8 weeks and serum HCG levels of 1455 mmol/L. The B ultrasound showed an endometrial thickness of 1.7 cm, and the presence of a cystic structure (16 6 mm) at the right uterine horn. Color Doppler flow imaging (CDFI) accurately detected and confirmed the position of the cystic structure with its clear boundaries.

DIAGNOSES

Cornual ectopic pregnancy in adenomyosis.

INTERVENTIONS

The diagnosis was confirmed and treated by HIFU ablation. Total ablation was performed for 738 seconds without any bleeding.

OUTCOMES

Serum HCG levels decreased to < 0.1 mmol/L after 60 days post operation, and follow-up for 11 months showed a regular menstrual cycle without dysmenorrhea. Gestational sac was not obvious at postoperative 90 days by MRI. The adenomyosis associated lesion with blood perfusion became smaller at postoperative 90 days.

LESSONS

In this case, we successfully performed HIFU ablation and treated the cornual ectopic pregnancy in an adenomyosis patient for the first time, without any adverse complications.

Non-invasive high-intensity focused ultrasound for UV-induced hyperpigmentation in Fitzpatrick skin types III and IV: a prospective, randomized, controlled, evaluator-blinded trial

Skin hyperpigmentation is a frequently encountered problem, particularly in darker skin types. Unfortunately, standard treatments for this condition have shown disappointing results. High-intensity focused ultrasound (HIFU) is commonly indicated for skin laxity, but recently was used to treat UV-induced hyperpigmentation in animal models. This study is aimed to evaluate the efficacy and safety of high-intensity focused ultrasound for UVB-induced hyperpigmentation in human subjects. A randomized, evaluator-blinded pilot study was conducted on 20 subjects. Each subject was induced three hyperpigmentary spots by local broadband UVB. After 2 weeks, each spot was randomly allocated to control, low-energy, and high-energy HIFU. Subjects were instructed to follow up weekly for a duration of 1 month. Lightness index measurements, mean improvement scores, subjects' satisfaction, pain scores, and side effects were evaluated. All 20 subjects completed the study. Fourteen subjects had Fitzpatrick (FPT) skin type III and six subjects had FPT skin type IV. Twelve subjects showed greater improvement at control sites while eight subjects showed greater improvement at HIFU-treated sites. In FPT skin type III, HIFU appeared to be inferior to control in both lightness index and mean improvement scores, but in FPT skin type IV, HIFU had greater lightness index improvement and higher improvement scores than control. Side effects were more frequent in high-energy-treated areas. Focused ultrasound may be offered in some patients with hyperpigmentary conditions. More research is needed to determine proper energy settings for optimal outcome.

Dependence of Boiling Histotripsy Treatment Efficiency on HIFU Frequency and Focal Pressure Levels

Boiling histotripsy (BH) is a high-intensity focused ultrasound (HIFU)-based method of mechanical tissue fractionation that utilizes millisecond-long bursts of HIFU shock waves to cause boiling at the focus in milliseconds. The subsequent interaction of the incoming shocks with the vapor bubble mechanically lyses surrounding tissue and cells. The acoustic parameter space for BH has been investigated previously and an inverse dependence between the HIFU frequency and the dimensions of a BH lesion has been observed. The primary goal of the present study was to investigate in more detail the ablation rate and reliability of BH in the frequency range relevant to treatment of deep abdominal tissue targets (1-2 MHz). The second goal was to investigate the effect of focal peak pressure levels and shock amplitude on BH lesion formation, given a constant duty factor, a constant ratio of the pulse duration to the time to reach boiling and a constant number of BH pulses. A custom-built 12-element sector array HIFU transducer with F-number = 1.05 was used in all experiments. BH pulses at 5 different frequencies (1, 1.2, 1.5, 1.7 and 1.9 MHz) were delivered to optically transparent polyacrylamide gel phantoms and ex vivo bovine liver and myocardium tissue to observe cavitation and boiling bubble activity with high-speed photography and B-mode ultrasound imaging, correspondingly. In gel phantoms, a cavitation bubble cloud was shown to form prefocally and to shield the focus in all exposures at 1 and 1.2 MHz and in the highest amplitude exposures at 1.5-1.7 MHz; shielding was not observed at 1.9 MHz. In ex vivo tissue, this shielding effect was observed in 25% of exposures when peak negative in situ pressure exceeded 10.2 MPa at 1 MHz and 14.5 MPa at 1.5 MHz. When shielding occurred, the exposures resulted in mild tissue disruption in the prefocal region, but not liquefaction. The dimensions of liquefied lesions followed the inverse proportionality trend with frequency; consequently, the frequency range of 1.2-1.5 MHz appeared to be preferable for BH exposures in terms of the compromise between the ablation rate and reliability. The lesion size was independent of the duration of the BH pulses (or the total "HIFU on" time), provided that the number of pulses was constant and boiling was induced within each pulse. Thus, the use of shorter (1 ms vs. 10 ms), higher amplitude BH pulses allowed up to 10-fold reduction in treatment time for a given duty factor.

Partial ablation of the pancreas of Sprague Dawley® rats by focused ultrasound reveals no significant adverse effects on glycometabolism function

To investigate the safety of focused ultrasound (FUS) partial ablation on the pancreas of Sprague Dawley® (SD) rats by histopathological examination of the outcome and investigation of glycometabolism function changes after local ablation. A total of 135 healthy SD rats were randomly divided into three groups (n=45 of each): FUS ½ group, FUS ¼ group, and control group. Levels of serum amylase was measured using the enzyme dynamics method, fasting blood glucose was measured by the glucose oxidase-peroxidase method, fasting serum insulin was measured by direct chemiluminescence assay, and an ELISA was used to measure fasting serum glucagon immediately after treatment, and at 2h, 3days, 1, 2, 3 and 4weeks, 3 and 6months after FUS ablation. Pancreatic tissue was stained with hematoxylin and eosin and the pathology of the ablation area was examined under an optical microscope; additionally, the expression of insulin and glucagon was investigated by immunohistochemistry. Compared with the control group, serum amylase and fasting blood glucose levels in the ablation groups rose significantly immediately after operation; fasting blood glucose, serum amylase, serum insulin and glucagon levels in the ablation groups were significantly different at 2h after treatment, and serum amylase levels in the ablation groups remained significantly different on day 3. Histological findings showed that the coagulation necrosis area gradually shrank, with formation of new blood vessels observed at week 3, and new ducts observable in the ablation area at the 3rd month after FUS ablation, but no formation of islets was observed. Expression of insulin and glucagon in the ablation groups were significantly higher than in the control group at 2h after FUS ablation. There were no significant adverse effects on the glycometabolic function of SD rats after FUS ablation, and the influence of FUS treatment on pancreatic functions were minimal.

Enhancing tissue permeability with MRI guided preclinical focused ultrasound system in rabbit muscle: From normal tissue to VX2 tumor

High Intensity Focused Ultrasound (HIFU) is an emerging noninvasive, nonionizing physical energy based modality to ablate solid tumors with high power, or increase local permeability in tissues/tumors in pulsed mode with relatively low power. Compared with traditional ablative HIFU, nondestructive pulsed HIFU (pHIFU) is present in the majority of novel applications recently developed for enhancing the delivery of drugs and genes. Previous studies have demonstrated the capability of pHIFU to change tissue local permeability for enhanced drug delivery in both mouse tumors and mouse muscle. Further study based on bulk tissues in large animals and clinical HIFU system revealed correlation between therapeutic effect and thermal parameters, which was absent in the previous mouse studies. In this study, we further investigated the relation between the therapeutic effect of pHIFU and thermal parameters in bulky normal muscle tissues based on a rabbit model and a preclinical HIFU system. Correlation between therapeutic effect and thermal parameters was confirmed in our study on the same bulk tissues although different HIFU systems were used. Following the study in bulky normal muscle tissues, we further created bulky tumor model with VX2 tumors implanted on both hind limbs of rabbits and investigated the feasibility to enhance tumor permeability in bulky VX2 tumors in a rabbit model using pHIFU technique. A radiolabeled peptidomimetic integrin antagonist, 111In-DOTA-IA, was used following pHIFU treatment in our study to target VX2 tumor and serve as the radiotracer for follow-up single-photon emission computed tomography (SPECT) scanning. The results have shown significantly elevated uptake of 111In-DOTA-IA in the area of VX2 tumors pretreated by pHIFU compared with the control VX2 tumors not being pretreated by pHIFU, and statistical analysis revealed averaged 34.5% enhancement 24h after systematic delivery of 111In-DOTA-IA in VX2 tumors pretreated by pHIFU compared with the control VX2 tumors.

Single-Session High-Intensity Focused Ultrasound Treatment in Large-Sized Benign Thyroid Nodules

BACKGROUND

High-intensity focused ultrasound (HIFU) is a new promising thermal ablation technique for treating benign thyroid nodules, but its effectiveness in larger-sized nodules has been less well described. The present study aimed to evaluate the treatment efficacy (i.e., extent of shrinkage at six months) of large-sized benign thyroid nodules by ultrasound (USG)-guided HIFU ablation.

MATERIALS AND METHODS

After ethics approval, all consecutive patients who underwent HIFU ablation of a symptomatic benign thyroid nodule with six or more months of follow-up were analyzed. Treated nodules were categorized according to their pre-ablation volume (group I: <10 mL; groups II: 10-30 mL; group III: >30 mL). After treatment, the nodule volume was measured by USG at one week, one month, three months, and six months. Total energy delivered to each nodule (in kJ) and the time taken (in minutes) for that delivery were automatically recorded. The primary outcome was a change in nodule volume after six months, where percentage nodule volume change was calculated as (baseline volume - volume at six months)/(baseline volume) × 100. Ablation success was defined as >50% volume reduction.

RESULTS

Seventy-three nodules were treated successfully and followed for ≥6 months. The overall median six-month volume reduction was 68.3% (range 22.77-96.50%). At six months, group III had a significantly less volume shrinkage than group I (48.1% vs. 77.6%; p < 0.001) and group II (48.1% vs. 67.9%; p = 0.002). Also, the proportion of ablation success at six months in group III was significantly less than in the other two groups (p < 0.001). Pre-ablation nodule volume >30 mL (odds ratio = 7.813 [confidence interval 1.908-32.258]; p = 0.004) and lower total energy per nodule volume (odds ratio = 3.313 [confidence interval 1.113-9.688]; p = 0.029) were significant factors for less ablation success.

CONCLUSIONS

Single-session HIFU ablation was highly effective in causing shrinkage of benign thyroid nodules at six months, but the extent of shrinkage for larger-sized nodules (>30 mL) was noticeably less than that of smaller-sized nodules. Both pre-ablation nodule volume and total energy per nodule volume were significant determinants of ablation success. For larger-sized nodules, additional HIFU treatment three to six months after initial treatment might be preferred over sequential treatment within the same session.

Feasibility of photoacoustic evaluations on dual-thermal treatment of ex vivo bladder tumors

A variety of thermal therapeutic methods have been investigated to treat bladder tumors but often cause bowel injury and bladder wall perforation due to high treatment dosage and limited clinical margins. The objective of the current study is to develop a dual-thermal modality to deeply coagulate the bladder tumors at low thermal dosage and to evaluate therapeutic outcomes with high contrast photoacoustic imaging (PAI). High intensity focused ultrasound (HIFU) is combined with 532 nm laser light to enhance therapeutic depth during thermal treatments on artificial tumor-injected bladder tissue ex vivo. PAI is employed to identify the margins of the tumors pre- and post-treatments. The dual-thermal modality achieves 3- and 1.8-fold higher transient temperature changes and 2.2- and 1.5-fold deeper tissue denaturation than laser and HIFU, respectively. PAI vividly identifies the position of the injected tumor and entails approximately 7.9 times higher image contrast from the coagulated tumor as that from the untreated tumor. Spectroscopic analysis exhibits that both 740 nm and 760 nm attains the maximum photoacoustic amplitudes from the treated areas. The proposed PAI-guided dual-thermal treatments (laser and HIFU) treatments can be a feasible therapeutic modality to treat bladder tumors in a controlled and efficient manner.

[Measurement of Phase-controlled Characteristics of HIFU Based on Infrared Thermal Imaging]

Phase-Controlled high intensity focused ultrasound 3D temperature distribution is the key indicator for measuring the efficiency of HIFU transducer. Considerable progress has been achieved in the use of infrared (IR) imaging techniques for qualitative mapping of acoustic and thermal field of high intensity focused ultrasound (HIFU) transducers. This article proposes a method to measure phased-controlled characteristics of HIFU based on infrared thermal imaging and establishes a whole measurement system to make the method more quantitative and reliable. The result shows that the proposed measurement system is able to measure pHIFU characteristics rapidly and precisely, which will be of great significance in standardizing the measurement of pHIFU acoustic field.

Efficacy of single-dose gonadotropin-releasing hormone agonist administration prior to magnetic resonance-guided focused ultrasound surgery for symptomatic uterine fibroids

PURPOSE

To investigate the effects of a single-dose GnRHa on the thermal ablation of MRgFUS in women with symptomatic fibroids.

MATERIALS AND METHOD

In this pilot study, a single-dose GnRHa was administered in 17 patients with a total of 20 fibroids. Volume and scaled signal intensity (SSI) as an objective marker of fluid contents were prospectively followed up with serial MR scans. The control group of 17 patients with 19 fibroids were retrospectively enrolled and compared with GnRHa group in terms of non-perfused volume (NPV) and thermal dosimetry to assess the efficiency of thermal ablation.

RESULTS

About 29 days after GnRHa administration, SSI and volume of fibroids were reduced by 55.1 and 10.6%, respectively (p < 0.05) but no adverse events were reported. NPV per unit energy (0.046 cm³/J ± 0.026 vs. 0.031 cm³/J ± 0.018, p = 0.041) was larger and SSI (8.4 ± 8.0 vs. 13.9 ± 12.0, p = 0.053) was lower in GnRHa group. Linear regression analysis showed that these two parameters were in a reverse correlation (p = 0.011).

CONCLUSION

GnRHa is supposed to reduce the fluid contents of fibroids including blood vessels and enhance the tissue responsiveness to thermal energy. A single dose prior to MRgFUS has the potential to improve treatment efficiency, while avoiding the side effects of multiple doses of GnRHa.

Nonlinear 3-D simulation of high-intensity focused ultrasound therapy in the Kidney

Kidney cancer is a severe disease which can be treated non-invasively using high-intensity focused ultrasound (HIFU) therapy. However, tissue in front of the transducer and the deep location of kidney can cause significant losses to the efficiency of the treatment. The effect of attenuation, refraction and reflection due to different tissue types on HIFU therapy of the kidney was studied using a nonlinear ultrasound simulation model. The geometry of the tissue was derived from a computed tomography (CT) dataset of a patient which had been segmented for water, bone, soft tissue, fat and kidney. The combined effect of inhomogeneous attenuation and soundspeed was found to result in an 11.0 dB drop in spatial peak-temporal average (SPTA) intensity in the kidney compared to pure water. The simulation without refraction effects showed a 6.3 dB decrease indicating that both attenuation and refraction contribute to the loss in focal intensity. The losses due to reflections at soft tissue interfaces were less than 0.1 dB. Focal point shifting due to refraction effects resulted in -1.3, 2.6 and 1.3 mm displacements in x-, y- and z-directions respectively. Furthermore, focal point splitting into several smaller subvolumes was observed. The total volume of the secondary focal points was approximately 46% of the largest primary focal point. This could potentially lead to undesired heating outside the target location and longer therapy times.

[Effects of high-intensity focused ultrasound on apoptosis-associated gene expression in xenografts with human pancreatic cancer]

Objective: To identify the expression of apoptosis-associated genes of high- intensity focused ultrasound(HIFU) in xenograft with human pancreatic cancer. Methods: Mice implated with human pancreatic cancer cells (YY-1) were divided into HIFU group or control group. Tumor cell apoptosis was verified by TUNEL. The expression of the apoptosis-associated genes was analyzed by Agilent Human Gene Expression. Selected genes was validated by quantitative real-time PCR(RT-PCR)and Western blot. Results: The rate of tumor cell apoptosis in HIFU group was higher than that of control group at 7, 14 days after HIFU treatment ((63.6%±15.2%)vs (19.0%±2.4%), P<0.01)and ((41.4%±7.3%)vs(18.0%±2.4%), P<0.01). Gene expression profiling revealed a total of 69 differentially expressed genes in related to apoptosis pathway, among which 44 genes were up-regulated, and 25 genes down-regulated. The RT-PCR results of selected 4 genes were consistent with those of gene expression profiling. The results of Western blot analysis at 7, 14 days after HIFU treatment showed that the expressions level of Bax protein in HIFU group was greater that of in control group ((0.39±0.11)vs (0.20±0.09), P<0.05)and ((0.46±0.12)vs(0.24±0.10), P<0.05), while the expressions level of Bcl-2 protein in HIFU group was lower than that of in control group ((0.68±0.14)vs(1.56±0.21), P<0.05)and((0.51±0.16)vs(1.57±0.22), P<0.05). Conclusions: HIFU could induce apoptosis and results in dramatic changes in gene expression, indicating that multiple pathways are involved. Although intrinsic pathway might be predominantly involved in HIFU-elicited apoptosis, further research is needed to clarify the detailed mechanisms.

Active targeting theranostic iron oxide nanoparticles for MRI and magnetic resonance-guided focused ultrasound ablation of lung cancer

Despite its great promise in non-invasive treatment of cancers, magnetic resonance-guided focused ultrasound surgery (MRgFUS) is currently limited by the insensitivity of magnetic resonance imaging (MRI) for visualization of small tumors, low efficiency of in vivo ultrasonic energy deposition, and damage to surrounding tissues. We hereby report the development of an active targeting nano-sized theranostic superparamagnetic iron oxide (SPIO) platform for significantly increasing the imaging sensitivity and energy deposition efficiency using a clinical MRgFUS system. The surfaces of these PEGylated SPIO nanoparticles (NPs) were decorated with anti-EGFR (epidermal growth factor receptor) monoclonal antibodies (mAb) for targeted delivery to lung cancer with EGFR overexpression. The potential of these targeted nano-theranostic agents for MRI and MRgFUS ablation was evaluated in vitro and in vivo in a rat xenograft model of human lung cancer (H460). Compared with nontargeting PEGylated SPIO NPs, the anti-EGFR mAb targeted PEGylated SPIO NPs demonstrated better targeting capability to H460 tumor cells and greatly improved the MRI contrast at the tumor site. Meanwhile, this study showed that the targeting NPs, as synergistic agents, could significantly enhance the efficiency for in vivo ultrasonic energy deposition in MRgFUS. Moreover, we demonstrated that a series of MR methods including T2-weighted image (T2WI), T1-weighted image (T1WI), diffusion-weighted imaging (DWI) and contrast-enhanced T1WI imaging, could be utilized to noninvasively and conveniently monitor the therapeutic efficacy in rat models by MRgFUS.

3D Quasi-Static Ultrasound Elastography With Plane Wave In Vivo

In biological tissue, an increase in elasticity is often a marker of abnormalities. Techniques such as quasi-static ultrasound elastography have been developed to assess the strain distribution in soft tissues in two dimensions using a quasi-static compression. However, as abnormalities can exhibit very heterogeneous shapes, a three dimensional approach would be necessary to accurately measure their volume and remove operator dependency. Acquisition of volumes at high rates is also critical to performing real-time imaging with a simple freehand compression. In this study, we developed for the first time a 3D quasi-static ultrasound elastography method with plane waves that estimates axial strain distribution in vivo in entire volumes at high volume rate. Acquisitions were performed with a 2D matrix array probe of 2.5 MHz frequency and 256 elements. Plane waves were emitted at a volume rate of 100 volumes/s during a continuous motorized and freehand compression. 3D B-mode volumes and 3D cumulative axial strain volumes were successfully estimated in inclusion phantoms and in ex vivo canine liver before and after a high intensity focused ultrasound ablation. We also demonstrated the in vivo feasibility of the method using freehand compression on the calf muscle of a human volunteer and were able to retrieve 3D axial strain volume at a high volume rate depicting the differences in stiffness of the two muscles which compose the calf muscle. 3D ultrasound quasi-static elastography with plane waves could become an important technique for the imaging of the elasticity in human bodies in three dimensions using simple freehand scanning.

High intensity focused ultrasound (HIFU) in tumor therapy

HIFU (high intensity focused ultrasound) is a method in which high-frequency ultrasound is focused on a tissue in order to achieve a thermal effect and the subsequent percutaneously ablation, or tissue modulation. HIFU is non-invasive and results in an immediate tissue destruction effect corresponding to surgery, either percutaneously or through body cavities. HIFU can be utilized in the treatment of both benign and malignant tumors. In neurological diseases, focused HIFU can be used in the treatment of disorders of the basal ganglia.

[New methods of uterine fibroids treatment]

Uterine fibroids are the most common benign tumors of the uterus. Their main symptoms are prolonged menstrual bleeding, leading over time to a secondary anemia, bleeding and spotting between periods, pelvic pain and infertility. It is recognized that fibroids are the most common indication for surgery in gynecology. Currently radical surgical treatment of fibroids is abandon. Ulipristalu acetate is used in pharmacological treatment. This medicine reduces the growth of fibroids. New non-invasive technique is also MR-guided focused ultrasound surgery using thermal tissue destruction by focusing ultrasound beam. Ability to avoid the often crippling surgery makes conservative methods increasingly popular.

Template-Free Synthesis of Hollow/Porous Organosilica-Fe3O4 Hybrid Nanocapsules toward Magnetic Resonance Imaging-Guided High-Intensity Focused Ultrasound Therapy

Entirely differing from the common templating-based multistep strategy for fabricating multifunctional hollow mesoporous silica nanoparticles (HMSN), a facile and template-free synthetic strategy has been established to construct a unique hollow/mesoporous organosilica nanocapsule (OSNC) concurrently encapsulating both isopentyl acetate (PeA) liquid and superparamagnetic iron oxides inside (denoted as PeA@OSNC). This novel material exhibits ultrasmall and uniform particle size (∼82 nm), high surface area (∼534 m²·g^-1), and excellent colloidal stability in aqueous solution. The oil-phase PeA with relatively low boiling point (142 °C) and high volatility not only plays a crucial role in formation of a large hollow cavity from the viewpoint of structural design but also enables the PeA@OSNC to act as an efficient enhancement agent in high-intensity focused ultrasound (HIFU) therapy. Moreover, the unique satellite-like distribution of Fe₃O₄ nanoparticles (NP) on the organosilica shell offered excellent magnetic resonance imaging (MRI) contrast capability of PeA@OSNC in vitro and in vivo. More importantly, such a novel theranostic agent has favorable biosafety, which is very promising for future clinical application in MRI-guided HIFU therapy.

[Effect of low-dose focused ultrasound pre-irradiation versus microbubbles for enhancing high-intensity focused ultrasound ablation of VX2 hepatic tumor in rabbits]

OBJECTIVE

To compare the effect of low-dose focused ultrasound pre-irradiation and microbubbles for enhancing the ablation effect of high intensity focused ultrasound (HIFU) on VX₂ hepatic tumor in rabbits.

METHODS

Fifty-five rabbits bearing VX₂ hepatic tumor were randomly divided into low-dose pre-irradiation + HIFU ablation group, microbubbles+HIFU ablation group, and HIFU ablation group for corresponding treatments. The pathological changes in the tumors after low-dose irradiation, time for HIFU ablation, tumor volume with coagulative necrosis, energy efficiency factor (EEF), pathological changes in the ablated tumor, and sound channel of HIFU ablation were observed.

RESULTS

Tumor cell edema, vacuolar changes in the cytoplasm and tumor interstitial vascular congestion were observed 24 h after low-dose pre-irradiation. The ablation time were significantly shorter, coagulative necrosis volume was larger, and EEF was lower in low-dose irradiation + HIFU ablation group and microbubbles+HIFU ablation group than in simple HIFU ablation group (P<0.05), but the differences between the former two groups were not significant. The effectiveness and stability of the synergistic effect of low-dose pre-irradiation were inferior to microbubbles, but the former ensured a better safety of the sound channel.

CONCLUSION

Low-dose irradiation has comparable synergistic effect in HIFU with microbubbles with such advantages as non-invasiveness, high concentration and good safety, and can be a potentially new method to enhance the efficiency of HIFU.

Quantitative Ultrasound for Monitoring High-Intensity Focused Ultrasound Treatment In Vivo

The success of any minimally invasive treatment procedure can be enhanced significantly if combined with a robust noninvasive imaging modality that can monitor therapy in real time. Quantitative ultrasound (QUS) imaging has been widely investigated for monitoring various treatment responses such as chemotherapy, radiation, and thermal therapy. Previously, we demonstrated the feasibility of using spectral-based QUS parameters to monitor high-intensity focused ultrasound (HIFU) treatment of in situ tumors in euthanized rats [Ultrasonic Imaging 36(4), 239-255, 2014]. In the present study, we examined the use of spectral-based QUS parameters to monitor HIFU treatment of in vivo rat mammary adenocarcinoma tumors (MAT) where significant tissue motion was present. HIFU was applied to tumors in rats using a single-element transducer. During the off part of the HIFU duty cycle, ultrasound backscatter was recorded from the tumors using a linear array co-aligned with the HIFU focus. A total of 10 rats were treated with HIFU in this study with an additional sham-treated rat. Spectral parameters from the backscatter coefficient, i.e., effective scatterer diameter (ESD) and effective acoustic concentration (EAC), were estimated. The changes of each parameter during treatment were compared with a temperature profile recorded by a fine-needle thermocouple inserted into the tumor a few millimeters behind the focus of the HIFU transducer. The mean ESD changed from 121 ±6 to [Formula: see text], and the EAC changed from 33 ±2 to [Formula: see text] during HIFU exposure as the temperature increased on average from 38.7 ±1.0 (°)C to 64.2 ±2.7 (°)C. The changes in ESD and EAC were linearly correlated with the changes in tissue temperature during the treatment. When HIFU was turned off, the ESD increased from 81 ±8 to [Formula: see text] and the EAC dropped from 46 ±3 to 36±2 dB/cm(3) as the temperature decreased from 64.2 ±2.7 (°)C to 45 ±2.7 (°)C. QUS was demonstrated in vivo to track temperature elevations caused by HIFU exposure.

Sonoluminescence characterization of inertial cavitation inside a BSA phantom treated by pulsed HIFU

The aim of this study was to investigate the inertial cavitation inside a phantom treated by pulsed HIFU (pHIFU). Basic bovine serum albumin (BSA) phantoms without any inherent ultrasound contrast agents (UCAs) or phase-shift nano-emulsions (PSNEs) were used. During the treatment, sonoluminescence (SL) recordings were performed to characterize the spatial distribution of inertial cavitation adjacent to the focal region. High-speed photographs and thermal coagulations, comparing with the SL results, were also recorded and presented. A series of pulse parameters (pulse duration (PD) was between 1 and 23 cycles and pulse repetition frequency (PRF) was between 0.5kHz and 100kHz) were performed to make a systematic investigation under certain acoustic power (APW). Continuous HIFU (cHIFU) investigation was also performed to serve as control group. It was found that, when APW was 19.5W, pHIFU with short PD was much easier to form SL adjacent to the focal region inside the phantom, while it was difficult for cHIFU to generate cavitation bubbles. With appropriate PD and PRF, the residual bubbles of the previous pulses could be stimulated by the incident pulses to oscillate in a higher level and even violently collapse, resulting to enhanced physical thermogenesis. The experimental results showed that the most violent inertial cavitation occurs when PD was set to 6 cycles (5μs) and PRF to 10kHz, while the highest level of thermal coagulation was observed when PD was set to 10 cycles. The cavitational and thermal characteristics were in good correspondence, exhibiting significant potentiality regarding to inject-free cavitation bubble enhanced thermal ablation under lower APW, compared to the conventional thermotherapy.

The efficacy of high-intensity, focused ultrasound treatment for non-neoplastic epithelial disorders of the vulva

Non-neoplastic epithelial disorders of the vulva (NNEDV) are common types of vulval lesions. Although corticosteroids represent a first-line treatment for NNEDV, concerns exist about the safety associated with long-term topical corticosteroid use. Recently, several clinical trials have identified high-intensity focused ultrasound (HIFU) as a promising treatment modality for NNEDV. The aim of this multi-center, randomized, controlled clinical trial was to investigate the efficacy of HIFU therapy in women with NNEDV based on histological alterations. We enrolled patients who were clinically diagnosed with NNEDV. They were randomized into 2 treatment groups: 1) halcinonide for 3 months or 2) HIFU once. A total of 123 patients were biopsied both prior to and after the therapy, and 62 and 61 patients were assigned to the HIFU and halcinonide groups, respectively. The histological changes were then analyzed. After the treatments, the therapeutic effects were observed in both groups. Comparing the diagnosis and alterations in lichenoid and sclerotic patterns and in chronic inflammation, we found statistically significant differences. Furthermore, when compared with the halcinonide group, the HIFU group exhibited enhanced curative effects that were statistically significant (P = 0.039). Based on the histological evidence from this randomized, controlled trial, HIFU represents an effective method for the treatment of NNEDV.

Bubble-Induced Color Doppler Feedback for Histotripsy Tissue Fractionation

Histotripsy therapy produces cavitating bubble clouds to increasingly fractionate and eventually liquefy tissue using high-intensity ultrasound pulses. Following cavitation generated by each pulse, coherent motion of the cavitation residual nuclei can be detected using metrics formed from ultrasound color Doppler acquisitions. In this paper, three experiments were performed to investigate the characteristics of this motion as real-time feedback on histotripsy tissue fractionation. In the first experiment, bubble-induced color Doppler (BCD) and particle image velocimetry (PIV) analysis monitored the residual cavitation nuclei in the treatment region in an agarose tissue phantom treated with two-cycle histotripsy pulses at [Formula: see text] using a 500-kHz transducer. Both BCD and PIV results showed brief chaotic motion of the residual nuclei followed by coherent motion first moving away from the transducer and then rebounding back. Velocity measurements from both PIV and BCD agreed well, showing a monotonic increase in rebound time up to a saturation point for increased therapy dose. In a second experiment, a thin layer of red blood cells (RBC) was added to the phantom to allow quantification of the fractionation of the RBC layer to compare with BCD metrics. A strong linear correlation was observed between the fractionation level and the time to BCD peak rebound velocity over histotripsy treatment. Finally, the correlation between BCD feedback and histotripsy tissue fractionation was validated in ex vivo porcine liver evaluated histologically. BCD metrics showed strong linear correlation with fractionation progression, suggesting that BCD provides useful quantitative real-time feedback on histotripsy treatment progression.

Phase aberration simulation study of MRgFUS breast treatments

PURPOSE

This simulation study evaluates the effects of phase aberration in breast MR-guided focused ultrasound (MRgFUS) ablation treatments performed with a phased-array transducer positioned laterally to the breast. A quantification of these effects in terms of thermal dose delivery and the potential benefits of phase correction is demonstrated in four heterogeneous breast numerical models.

METHODS

To evaluate the effects of varying breast tissue properties on the quality of the focus, four female volunteers with confirmed benign fibroadenomas were imaged using 3T MRI. These images were segmented into numerical models with six tissue types, with each tissue type assigned standard acoustic properties from the literature. Simulations for a single-plane 16-point raster-scan treatment trajectory centered in a fibroadenoma in each modeled breast were performed for a breast-specific MRgFUS system. At each of the 16 points, pressure patterns both with and without applying a phase correction technique were determined with the hybrid-angular spectrum method. Corrected phase patterns were obtained using a simulation-based phase aberration correction technique to adjust each element's transmit phase to obtain maximized constructive interference at the desired focus. Thermal simulations were performed for both the corrected and uncorrected pressure patterns using a finite-difference implementation of the Pennes bioheat equation. The effect of phase correction was evaluated through comparison of thermal dose accumulation both within and outside a defined treatment volume. Treatment results using corrected and uncorrected phase aberration simulations were compared by evaluating the power required to achieve a 20 °C temperature rise at the first treatment location. The extent of the volumes that received a minimum thermal dose of 240 CEM at 43 °C inside the intended treatment volume as well as the volume in the remaining breast tissues was also evaluated in the form of a dose volume ratio (DVR), a DVR percent change between corrected and uncorrected phases, and an additional metric that measured phase spread.

RESULTS

With phase aberration correction applied, there was an improvement in the focus for all breast anatomies as quantified by a reduction in power required (13%-102%) to reach 20 °C when compared to uncorrected simulations. Also, the DVR percent change increased by 5%-77% in seven out of eight cases, indicating an improvement to the treatment as measured by a reduction in thermal dose deposited to the nontreatment tissues. Breast compositions with a higher degree of heterogeneity along the ultrasound beam path showed greater reductions in thermal dose delivered outside of the treatment volume with correction applied than beam trajectories that propagated through more homogeneous breast compositions. An increasing linear trend was observed between the DVR percent change and the phase-spread metric (R(2) = 0.68).

CONCLUSIONS

These results indicate that performing phase aberration correction for breast MRgFUS treatments is beneficial for the small-aperture transducer (14.4 × 9.8 cm) evaluated in this work. While all breast anatomies could benefit from phase aberration correction, greater benefits are observed in more heterogeneous anatomies.

The combination therapy of high-intensity focused ultrasound with radiotherapy in locally advanced pancreatic carcinoma

BACKGROUND

The aim of the present study is to evaluate the effectiveness of the combined application of high-intensity focused ultrasound (HIFU) and radiotherapy in the treatment of locally advanced pancreatic carcinoma (LAPC).

METHODS

A total number of sixteen patients with LAPC started treatment beginning with HIFU and radiotherapy 1 week after the HIFU treatment. Evaluation of the effectiveness of treatment was performed using main clinical symptoms, serum levels of CA-19-9, Response Evaluation Criteria in Solid Tumors (RECIST) guidelines, and the Kaplan-Meier method for estimating median overall survival (OS). The occurrence of adverse reactions was recorded.

RESULTS

The main clinical symptoms including abdominal pain and lower back pain were alleviated, and the mean visual analog scale (VAS) pain score declined from 5.1 points to just 3.3 points immediately after the HIFU treatment. The median pain relief time was 5.6 months after radiotherapy, serum CA-19-9 levels began to decrease significantly 1 week after the HIFU treatment, from 102.1 to 60.8 U/ml, and the median continuous decline time was 4.3 months after radiotherapy. Partial response (PR) was observed in seven of sixteen patients, with stable disease (SD) in four patients, and progressive disease (PD) in the remaining five patients at 6 months after radiotherapy. Serum levels of amylopsin and lipase were not elevated to abnormal levels. The median OS was 14 months. No serious adverse reactions occurred.

CONCLUSIONS

Treatment with both HIFU and radiotherapy can quickly improve symptoms and the quality of life and prolong survival lengths. This combination might be a promising therapeutic treatment for patients with LAPC.

Nanoparticle-enhanced synergistic HIFU ablation and transarterial chemoembolization for efficient cancer therapy

High-intensity focused ultrasound (HIFU) is being generally explored as a non-invasive therapeutic modality to treat solid tumors. However, the clinical use of HIFU for large and deep tumor-ablation applications such as hepatocellular carcinoma (HCC) is currently entangled with long treatment duration and high operating energy. This critical issue can be potentially resolved by the introduction of HIFU synergistic agents (SAs). Traditional SAs such as microbubbles and microparticles face the problem of large size, short cycle time, damage to mononuclear phagocytic system and unsatisfactory targeting efficiency. In this work, we have developed a facile and versatile nanoparticle-based HIFU synergistic cancer surgery enhanced by transarterial chemoembolization for high-efficiency HCC treatment based on elaborately designed Fe3O4-PFH/PLGA nanocapsules. Multifunctional Fe3O4-PFH/PLGA nanocapsules were administrated into tumor tissues via transarterial injection combined with Lipiodol to achieve high tumor accumulation because transarterial chemoembolization by Lipiodol could block the blood vessels. The high synergistic HIFU ablation effect was successfully achieved against HCC tumors based on the phase-transformation performance of the perfluorohexane (PFH) inner core in the composite nanocapsules, as systematically demonstrated in VX2 liver tumor xenograft in rabbits. Multifunctional Fe3O4-PFH/PLGA nanocapsules were also demonstrated as efficient contrast agents for ultrasound, magnetic resonance and photoacoustic tri-modality imagings, potentially applicable for imaging-guided HIFU synergistic surgery. Therefore, the elaborate integration of traditional transarterial chemoembolization with recently developed nanoparticle-enhanced HIFU cancer surgery could efficiently enhance the HCC cancer treatment outcome, initiating a new and efficient therapeutic protocol/modality for clinic cancer treatment.

Ultrasound ablation enhances drug accumulation and survival in mammary carcinoma models

Magnetic resonance-guided focused ultrasound (MRgFUS) facilitates noninvasive image-guided conformal thermal therapy of cancer. Yet in many scenarios, the sensitive tissues surrounding the tumor constrain the margins of ablation; therefore, augmentation of MRgFUS with chemotherapy may be required to destroy remaining tumor. Here, we used 64Cu-PET-CT, MRI, autoradiography, and fluorescence imaging to track the kinetics of long-circulating liposomes in immunocompetent mammary carcinoma-bearing FVB/n and BALB/c mice. We observed a 5-fold and 50-fold enhancement of liposome and drug concentration, respectively, within MRgFUS thermal ablation-treated tumors along with dense accumulation within the surrounding tissue rim. Ultrasound-enhanced drug accumulation was rapid and durable and greatly increased total tumor drug exposure over time. In addition, we found that the small molecule gadoteridol accumulates around and within ablated tissue. We further demonstrated that dilated vasculature, loss of vascular integrity resulting in extravasation of blood cells, stromal inflammation, and loss of cell-cell adhesion and tissue architecture all contribute to the enhanced accumulation of the liposomes and small molecule probe. The locally enhanced liposome accumulation was preserved even after a multiweek protocol of doxorubicin-loaded liposomes and partial ablation. Finally, by supplementing ablation with concurrent liposomal drug therapy, a complete and durable response was obtained using protocols for which a sub-mm rim of tumor remained after ablation.

Effects of Thermal Preconditioning on Tissue Susceptibility to Histotripsy

Histotripsy is a non-invasive ablation method that mechanically fractionates tissue by controlling acoustic cavitation. Previous work has revealed that tissue mechanical properties play a significant role in the histotripsy process, with stiffer tissues being more resistant to histotripsy-induced tissue damage. In this study, we propose a thermal pretreatment strategy to precondition tissues before histotripsy. We hypothesize that a thermal pretreatment can be used to alter tissue stiffness by modulating collagen composition, thus changing tissue susceptibility to histotripsy. More specifically, we hypothesize that tissues will soften and become more susceptible to histotripsy when preheated at ∼60°C because of collagen denaturation, but that tissues will rapidly stiffen and become less susceptible to histotripsy when preheated at ∼90°C because of collagen contraction. To test this hypothesis, a controlled temperature water bath was used to heat various ex vivo bovine tissues (tongue, artery, liver, kidney medulla, tendon and urethra). After heating, the Young's modulus of each tissue sample was measured using a tissue elastometer, and changes in tissue composition (i.e., collagen structure/density) were analyzed histologically. The susceptibility of tissues to histotripsy was investigated by treating the samples using a 750-kHz histotripsy transducer. Results revealed a decrease in stiffness and an increase in susceptibility to histotripsy for tissues (except urethra) preheated to 58°C. In contrast, preheating to 90°C increased tissue stiffness and reduced susceptibility to histotripsy for all tissues except tendon, which was significantly softened due to collagen hydrolysis into gelatin. On the basis of these results, a final set of experiments were conducted to determine the feasibility of using high-intensity focused ultrasound to provide the thermal pretreatment. Overall, the results of this study indicate the initial feasibility of a thermal pretreatment strategy to precondition tissue mechanical properties and alter tissue susceptibility to histotripsy. Future work will aim to optimize this thermal pretreatment strategy to determine if this approach is practical for specific clinical applications in vivo without causing unwanted damage to surrounding or overlying tissue.

Feasibility study of high intensity focused ultrasound (HIFU) for the treatment of hydatid cysts of the liver

This study evaluates the feasibility of using high intensity focused ultrasound (HIFU) for the treatment of hydatid cysts of the liver. HIFU ablation was carried out in 62 patients with echinococcosis of the liver. The mean age of patients was 40.76±14.84 (range: 17-72 years). The effectiveness of the treatment was monitored in real-time by changes in the gray-scale, and by morphological studies, computed tomography, magnetic resonance imaging, and ultrasound. Criteria for evaluating the effectiveness of treatment in real time were outlines. Cytomorphological picture of destructive changes of parasitic elements was presented as well. Loss of embryonic elements of the parasite was observed at the subcellular level after HIFU-ablation and underlines the effectiveness of HIFU.

Ultrasound Guided High Intensity Focused Ultrasound for malignant tumors: The Spanish experience of survival advantage in stage III and IV pancreatic cancer

We described the experience of the HIFU Onco Unit of Hospital University Mutua Terrassa (Barcelona, Spain) treating malignant tumors, focusing on results of unresectable pancreatic tumors treated with Ultrasound Guided High Intensity Focused Ultrasound (USgHIFU) hyperthermia ablation in combination with adjuvant chemotherapy.

MATERIALS AND METHODS

From February 2008 to December 2013, we treated 140 malignant cases. Of those, 48 cases of unresectable pancreatic tumors were treated from March 2010 to December 2013, and the first 43 were included in the analysis. All the 43 cases (29 cases of stage III and 14 cases of stage IV) were treated with systemic chemotherapy. Clinical responses (thermical ablation achieved) were measured by image techniques, and complications were also recorded and analyzed.

RESULTS

The majority of the 140 cases treated at our HIFU center were pancreatic and liver tumors, among which 43 cases of pancreatic tumors were analyzed. Clinical responses (ablation obtained) were observed in 82% of the cases, and the responses lasted at 8 weeks post-procedure. We obtained 11 complete responses (25%) at the end of the combined treatment, nine from stage III patients and two from stage IV patients. Major complications included severe pancreatitis with GI bleeding (1), and skin burning of grade III that required plastic surgery (2). The median survival was 13 months (6 months-2.7 years). No deaths were registered during the course of the treatment.

CONCLUSIONS

HIFU is a potentially effective and safe modality for the treatment of malignant tumors. HIFU proves to have a survival advantage in treating unresectable pancreatic cancer.

Humane accomplishment of physicians and the philosophy of minimally-invasive and noninvasive medicine: A perspective

The highest realm in clinical medicine is the harmonious unity of medical sciences and the humanistic spirit. Given that the beauty of human nature resides in humanity, a competent medical practitioner should be a sage that personifies the rigorous scientific spirit and the humanity. It is essential for a medical practitioner to learn to seek answers to medical inquiries at the philosophical level. Important as it is to study the organs, the cells and the functions of the body, medical practitioners need to be well-versed in the utmost beauty of mankind. The central tenet of minimally-invasive therapeutic medicine is to minimize harm to patients while effectively managing the lesion. The radical changes brought about by minimally-invasive technologies, exemplified by the non-invasive high intensity focused ultrasound (HIFU) surgery, are to change the face of traditional surgery.

Preoperative ultrasound ablation for borderline resectable pancreatic cancer: A report of 30 cases

BACKGROUND AND OBJECTIVES

Currently, extended resection and preoperative neoadjuvant chemotherapy are the two main modalities for improvement of the resection rate and R0 resection rate of borderline resectable pancreatic cancer. The past few years, however, have witnessed some progress in the treatment of unresectable pancreatic cancer with high intensity focused ultrasound (HIFU). The aim of this study is twofold: first, to evaluate the feasibility and safety of HIFU ablation as a preoperative adjuvant therapy for borderline resectable pancreatic cancer, and second, to conduct pathological analyses to verify the safety and effectiveness of HIFU treatment of pancreatic cancer.

METHODS

From January 2011 to December 2012, 30 patients with borderline resectable pancreatic cancer underwent HIFU ablation by Haifu Model-JC200 Focused Ultrasound Tumor Therapeutic System prior to radical surgery. The effect of pre-operative HIFU ablation was evaluated by post-HIFU functional imaging results, operation time of radical surgery, blood loss volume, R0 resection rate, postoperative 1-year survival rate and Ca199 curve. Postoperative pathological specimens were obtained for histological examination.

RESULTS

All 30 patients with borderline resectable pancreatic cancer had completed the treatments and follow-ups. Functional image assessment after HIFU treatment showed a mean tumor ablation rate of (61.5±24.3)%. 28 patients underwent radical resection of pancreatic cancer 7-9 days after HIFU treatment (23 cases underwent pancreaticoduodenectomy. 4 patients underwent pancreatectomy and 1 patient had total pancreatectomy). 7 patients underwent combined resection and reconstruction of portal-superior mesenteric vein (23.3%), with the resectability rate of 93.3%, the R0 resection rate of 92.7%, and the 1-year survival rate of 96.7%. The biological coagulative necrosis regions identified by the postoperative pathological examination matched well with the necrosis foci identified by post-operative functional imaging.

CONCLUSION

The effectiveness of HIFU ablation of pancreatic tumors, as well as interstitial tissues within he main vascular spaces was confirmed by post-operative pathological examinations. Based on these observations, we conclude that preoperative HIFU ablation of borderline resectable pancreatic cancer can significantly improve the resection rate, R0 resection rate, and reduce the difficulty and risk of surgery. Therefore, HIFU may be a valuable pre-operative adjunct therapy for resectable pancreatic cancer. However, the safety and the efficacy on the improvement of the surgery need to established with future multicenter, randomized studies.

Simulation of thermal ablation by high-intensity focused ultrasound with temperature-dependent properties

An integrated computational framework was developed in this study for modeling high-intensity focused ultrasound (HIFU) thermal ablation. The temperature field was obtained by solving the bioheat transfer equation (BHTE) through the finite element method; while, the thermal lesion was considered as a denatured material experiencing phase transformation and modeled with the latent heat. An equivalent attenuation coefficient, which considers the temperature-dependent properties of the target material and the ultrasound diffraction due to bubbles, was proposed in the nonlinear thermal transient analysis. Finally, a modified thermal dose formulation was proposed to predict the lesion size, shape and location. In-vitro thermal ablation experiments on transparent tissue phantoms at different energy levels were carried out to validate this computational framework. The temperature histories and lesion areas from the proposed model show good correlation with those from the in-vitro experiments.

High-intensity focused ultrasound ablation for diffuse uterine leiomyomatosis: A case report

Diffuse uterine leiomyomatosis (DUL) is a rare and unique type of uterine leiomyoma which affects women of reproductive age. While treatments like medication, uterine artery embolization (UAE) and hysteroscopic myomectomy show some effectiveness, hysterectomy is currently the only known treatment capable of eliminating the symptoms of this disease. This case report demonstrates that high intensity focused ultrasound (HIFU) ablation may offer these patients a new treatment strategy that could control the symptoms of DUL and spare the uterus from hysterectomy.

The theoretical basis of minimally-invasive and non-invasive medicine: Treatments--Minimize harm to patients

This perspective, for the first time, proposed the theoretical basis for the minimally-invasive and non-invasive medicine. It sets the goal of medical treatment that is to minimize harm to patients and to maximize the natural self-healing power for fighting against the disease. It took a historical review on the technological developments shaped by the minimally-invasive and non-invasive ideology with a focus on the course of research, development and clinical deployment of the high-intensity focused ultrasound (HIFU) ablation therapy by the Chinese research team. It also summarized the highlights of the "1st Yangtze International Summit of Minimally-invasive and Non-invasive Medicine 2013" and the mandate of the newly inaugurated International Society of the Minimally-invasive and Noninvasive Medicine (ISMINIM). It provides a perspective on the future development of this emerging field and its impact on human civilization.

Treatment of liver alveococcosis with high-intensity focused ultrasound

This study evaluates the feasibility of using high intensity focused ultrasound (HIFU) for the treatment of liver alveococcosis. HIFU ablation was carried out in 36 patients with alveococcosis of the liver. The median age of patients was 39.24±12, 93 years (range: 20-66 years). The efficiency of treatment was monitored in real time with morphological evaluation, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound (US), and with morphological cytological and electron microscopy studies. HIFU ablation has shown effectiveness in destroying the protoscolexes, laminar and cell elements of the cuticular and germinal membrane of the alveococcosis larvocyst, causing the death of the cells of initial metamorphosis of alveococcosis, which is responsible for the dissemination of the parasite in the liver. Therefore HIFU-therapy is a promising and effective treatment for liver alveococcosis.

Minimal invasive treatments for liver malignancies

Minimal invasive therapies have proved useful in the management of primary and secondary hepatic malignancies. The most relevant aspects of all these therapies are their minimal toxicity profiles and highly effective tumor responses without affecting the normal hepatic parenchyma. These unique characteristics coupled with their minimally invasive nature provide an attractive therapeutic option for patients who previously may have had few alternatives. Combination of these therapies might extend indications to bring curative treatment to a wider selected population. The results of various ongoing combination trials of intraarterial therapies with targeted therapies are awaited to further improve survival in this patient group. This review focuses on the application of ablative and intra-arterial therapies in the management of hepatocellular carcinoma and hepatic colorectal metastasis.

A computer-assisted robotic platform for Focused Ultrasound Surgery: Assessment of high intensity focused ultrasound delivery

In the last century, medicine showed considerable advancements in terms of new technologies, devices and diagnostic/therapeutic strategies. Those advantages led to a significant reduction of invasiveness and an improvement of surgical outcomes. In this framework, a computer-assisted surgical robotic platform able to perform non-invasive Focused Ultrasound Surgery (FUS) - the FUTURA platform - has the ambitious goal to improve accuracy, safety and flexibility of the treatment, with respect to current FUS procedures. Aim of this work is to present the current implementation of the robotic platform and the preliminary results about high intensity focused ultrasound (HIFU) delivery in in-vitro conditions, under 3D ultrasound identification and monitoring. Tests demonstrated that the average accuracy of the HIFU delivery is lower than 0.7 mm in both X and Y radial directions and 3.7 mm in the axial direction (Z) with respect to the HIFU transducer active surface.