HIFU for palliative treatment of pancreatic cancer

Investigation of the long-term healing response of the liver to boiling histotripsy treatment in vivo

Boiling histotripsy (BH) is a promising High-Intensity Focused Ultrasound technique that can be employed to mechanically fractionate solid tumours. Whilst studies have shown the feasibility of BH to destroy liver cancer, no study has reported on the healing process of BH-treated liver tissue. We therefore extensively investigated the evolution of the healing response of liver to BH in order to provide an insight into the healing mechanisms. In the present study, 14 Sprague Dawley rats underwent the BH treatment and were sacrificed on days 0, 3, 7, 14, and 28 for morphological, histological, serological and qPCR analyses. The area of the treated region was 1.44 cm² (1.2 cm × 1.2 cm). A well-defined BH lesion filled with coagulated blood formed on day 0. A week after the treatment, fibroblast activation was induced at the treatment site, leading to the formation of extracellular matrix structure (ECM). The ECM was then disrupted for 7 to 28 days. Regenerated normal hepatocytes and newly formed blood vessels were found within the BH region with the absence of hepatic fibrosis. No significant morphological, histological and genetic changes around the BH lesion occurred. These results suggest that BH could be a safe and promising therapeutic tool for treating solid tumours without inducing any significant adverse effect such as the formation of liver fibrosis.

Ultrasound-Responsive Liposomes for Targeted Drug Delivery Combined with Focused Ultrasound

Chemotherapeutic drugs are traditionally used for the treatment of cancer. However, chemodrugs generally induce side effects and decrease anticancer effects due to indiscriminate diffusion and poor drug delivery. To overcome these limitations of chemotherapy, in this study, ultrasound-responsive liposomes were fabricated and used as drug carriers for delivering the anticancer drug doxorubicin, which was able to induce cancer cell death. The ultrasound-sensitive liposome demonstrated a size distribution of 81.94 nm, and the entrapment efficiency of doxorubicin was 97.1 ± 1.44%. The release of doxorubicin under the ultrasound irradiation was 60% on continuous wave and 50% by optimizing the focused ultrasound conditions. In vivo fluorescence live imaging was used to visualize the doxorubicin release in the MDA-MB-231 xenografted mouse, and it was demonstrated that liposomal drugs were released in response to ultrasound irradiation of the tissue. The combination of ultrasound and liposomes suppressed tumor growth over 56% more than liposomes without ultrasound exposure and 98% more than the control group. In conclusion, this study provides a potential alternative for overcoming the previous limitations of chemotherapeutics.

High-intensity focused ultrasound therapy for pancreatic cancer

Pancreatic cancer (PC) has one of the poorest prognoses among solid cancers, and its incidence has increased recently. Satisfactory outcomes are not achieved with current therapies; thus, novel treatments are urgently needed. High-intensity focused ultrasound (HIFU) is a novel therapy for ablating tissue from the outside of the body by focusing ultrasonic waves from multiple sources on the tumor. In this therapy, only the focal area is heated to 80-100 ºC, which causes coagulative necrosis of the tissue, with hardly any impact on the tissue outside the focal area. Although HIFU is a minimally invasive treatment and is expected to be useful, it is not yet generally known. Here, we discuss the usefulness of HIFU treatment for un-resectable advanced PC using the results of previous research, meta-analyses, and systematic reviews on its efficacy and safety. HIFU therapy for un-resectable PC is useful for its anti-tumor effect and pain relief, and is expected to prolong survival time and improve quality of life. Although HIFU for PC has several limitations and further study is needed, this technique can be safely performed on un-resectable advanced PC. In future, HIFU could be utilized as a minimally invasive treatment strategy for PC patients with a poor prognosis.

Novel Therapeutic Method for Unresectable Pancreatic Cancer-The Impact of the Long-Term Research in Therapeutic Effect of High-Intensity Focused Ultrasound (HIFU) Therapy

High-intensity focused ultrasound (HIFU) is a novel advanced therapy for unresectable pancreatic cancer (PC). HIFU therapy with chemotherapy is being promoted as a novel method to control local advancement by tumor ablation. We evaluated the therapeutic effects of HIFU therapy in locally advanced and metastatic PC. PC patients were treated with HIFU as an optional local therapy and systemic chemotherapy. The FEP-BY02 (Yuande Bio-Medical Engineering) HIFU device was used under ultrasound guidance. Of 176 PC patients, 89 cases were Stage III and 87 were Stage IV. The rate of complete tumor ablation was 90.3%, while that of symptom relief was 66.7%. The effectiveness on the primary lesions were as follows: complete response (CR): n = 0, partial response (PR): n = 21, stable disease (SD): n = 106, and progressive disease (PD): n = 49; the primary disease control rate was 72.2%. Eight patients underwent surgery. The median survival time (MST) after diagnosis for HIFU with chemotherapy compared to chemotherapy alone (100 patients in our hospital) was 648 vs. 288 days (p < 0.001). Compared with chemotherapy alone, the combination of HIFU therapy and chemotherapy demonstrated significant prolongation of prognosis. This study suggests that HIFU therapy has the potential to be a novel combination therapy for unresectable PC.

Control of the dynamics of a boiling vapour bubble using pressure-modulated high intensity focused ultrasound without the shock scattering effect: A first proof-of-concept study

Boiling histotripsy is a promising High-Intensity Focused Ultrasound (HIFU) technique that can be used to induce mechanical tissue fractionation at the HIFU focus via cavitation. Two different types of cavitation produced during boiling histotripsy exposure can contribute towards mechanical tissue destruction: (1) a boiling vapour bubble at the HIFU focus and (2) cavitation clouds in between the boiling bubble and the HIFU source. Control of the extent and degree of mechanical damage produced by boiling histotripsy is necessary when treating a solid tumour adjacent to normal tissue or major blood vessels. This is, however, difficult to achieve with boiling histotripsy due to the stochastic formation of the shock scattering-induced inertial cavitation clouds. In the present study, a new histotripsy method termed pressure-modulated shockwave histotripsy is proposed as an alternative to or in addition to boiling histotripsy without inducing the shock scattering effect. The proposed concept is (a) to generate a boiling vapour bubble via localised shockwave heating and (b) subsequently control its extent and lifetime through manipulating peak pressure magnitudes and a HIFU pulse length. To demonstrate the feasibility of the proposed method, bubble dynamics induced at the HIFU focus in an optically transparent liver tissue phantom were investigated using a high speed camera and a passive cavitation detection systems under a single 10, 50 or 100 ms-long 2, 3.5 or 5 MHz pressure-modulated HIFU pulse with varying peak positive and negative pressure amplitudes from 5 to 89 MPa and -3.7 to -14.6 MPa at the focus. Furthermore, a numerical simulation of 2D nonlinear wave propagation with the presence of a boiling bubble at the focus of a HIFU field was conducted by numerically solving the generalised Westervelt equation. The high speed camera experimental results showed that, with the proposed pressure-modulated shockwave histotripsy, boiling bubbles generated by shockwave heating merged together, forming a larger bubble (of the order of a few hundred micron) at the HIFU focus. This coalesced boiling bubble then persisted and maintained within the HIFU focal zone until the end of the exposure (10, 50, or 100 ms). Furthermore, and most importantly, no violent cavitation clouds which typically appear in boiling histotripsy occurred during the proposed histotripsy excitation (i.e. no shock scattering effect). This was likely because that the peak negative pressure magnitude of the backscattered acoustic field by the boiling bubble was below the cavitation cloud intrinsic threshold. The size of the coalesced boiling bubble gradually increased with the peak pressure magnitudes. In addition, with the proposed method, an oval shaped lesion with a length of 0.6 mm and a width of 0.1 mm appeared at the HIFU focus in the tissue phantom, whereas a larger lesion in the form of a tadpole (length: 2.7 mm, width: 0.3 mm) was produced by boiling histotripsy. Taken together, these results suggest that the proposed pressure-modulated shockwave histotripsy could potentially be used to induce a more spatially localised tissue destruction with a desired degree of mechanical damage through controlling the size and lifetime of a boiling bubble without the shock scattering effect.

Investigation of Cylindrical Piezoelectric and Specific Multi-Channel Circular MEMS-Transducer Array Resonator of Ultrasonic Ablation

BACKGROUND

A cylindrical piezoelectric element and a specific multi-channel circular microelectromechanical systems (MEMS)-transducer array of ultrasonic system were used for ultrasonic energy generation and ablation. A relatively long time is required for the heat to be conducted to the target position. Ultrasound thermal therapy has great potential for treating deep hyperplastic tissues and tumors, such as breast cancer and liver tumors.

METHODS

Ultrasound ablation technology produces thermal energy by heating the surface of a target, and the heat gradually penetrates to the target's interior. Beamforming was performed to observe energy distribution. A resonance method was used to generate ablation energy for verification. Energy was generated according to the coordinates of geometric graph positions to reach the ablation temperature.

RESULTS

The mean resonance frequency of Channels 1-8 was 2.5 MHz, and the cylindrical piezoelectric ultrasonic element of Channel A was 4.2546 Ω at 5.7946 MHz. High-intensity ultrasound has gradually been applied in clinical treatment. Widely adopted, ultrasonic hyperthermia involves the use of high-intensity ultrasound to heat tissues at 42-45 °C for 30-60 min.

CONCLUSION

In the ultrasonic energy method, when the target position reaches a temperature that significantly reduces the cell viability (46.9 °C), protein surface modification occurs on the surface of the target.

The interaction of shockwaves with a vapour bubble in boiling histotripsy: The shock scattering effect

Boiling histotripsy is a High Intensity Focused Ultrasound (HIFU) technique which uses a number of short pulses with high acoustic pressures at the HIFU focus to induce mechanical tissue fractionation. In boiling histotripsy, two different types of acoustic cavitation contribute towards mechanical tissue destruction: a boiling vapour bubble and cavitation clouds. An understanding of the mechanisms underpinning these phenomena and their dynamics is therefore paramount to predicting and controlling the overall size of a lesion produced for a given boiling histotripsy exposure condition. A number of studies have shown the effects of shockwave heating in generating a boiling bubble at the HIFU focus and have studied its dynamics under boiling histotripsy insonation. However, not much is known about the subsequent production of cavitation clouds that form between the HIFU transducer and the boiling bubble. The main objective of the present study is to examine what causes this bubble cluster formation after the generation of a boiling vapour bubble. A numerical simulation of 2D nonlinear wave propagation with the presence of a bubble at the focus of a HIFU field was performed using the k-Wave MATLAB toolbox for time domain ultrasound simulations, which numerically solves the generalised Westervelt equation. The numerical results clearly demonstrate the appearance of the constructive interference of a backscattered shockwave by a bubble with incoming incident shockwaves. This interaction (i.e., the reflected and inverted peak positive phase from the bubble with the incoming incident rarefactional phase) can eventually induce a greater peak negative pressure field compared to that without the bubble at the HIFU focus. In addition, the backscattered peak negative pressure magnitude gradually increased from 17.4 MPa to 31.6 MPa when increasing the bubble size from 0.2 mm to 1.5 mm. The latter value is above the intrinsic cavitation threshold of -28 MPa in soft tissue. Our results suggest that the formation of a cavitation cloud in boiling histotripsy is a threshold effect which primarily depends (a) the size and location of a boiling bubble, and (b) the sum of the incident field and that scattered by a bubble.

Performance Improvement of Ring-Type PZT Ceramics for Ultrasonic Dispersion System

This study has been based on the examination of the characterization of ring-type lead zirconate titanate (PZT) ceramics for high-intensity focused ultrasonic dispersion system. The ring-type PZT ceramics were fabricated by the powder molding method. The mechanical properties, dielectric constant, and microstructure of the ceramics were investigated. Consequently, the density of the ceramics was increased with increasing forming pressure while the density of ceramics that were sintered at 1350 °C was decreased due to over-sintering. Furthermore, the mechanical properties were excellent at the higher forming pressure. The dielectric property of the ring-type PZT ceramics was not clearly influenced by the manufacturing and sintering conditions. The abnormal grain growth of the ceramics, however, could be prevented by a lower heating rate in addition to reducing the porosity.

Boiling Histotripsy-induced Partial Mechanical Ablation Modulates Tumour Microenvironment by Promoting Immunogenic Cell Death of Cancers

Boiling histotripsy is a promising non-invasive High-Intensity Focused Ultrasound (HIFU) technique that employs HIFU mechanical effects to fractionate solid tumours without causing any significant thermal damage. It has been suggested that boiling histotripsy may induce a strong immune response due to the absence of denatured antigenic protein at the HIFU focus. The underlying immunological mechanisms of this technique are, however, poorly understood. In this study, we demonstrated the feasibility of using boiling histotripsy to mechanically fractionate human breast adenocarcinoma cells (MDA-MB-231) and the potential immunological effects induced by boiling histotripsy, for the first time. Our results showed that mechanical stresses produced by boiling histotripsy promote immunogenic cell death of cancer cells via TNF-induced necrosis signaling pathway. This immunogenic cell death significantly increases secretions of damage-associated molecular patterns (CRT, HSP70, HMGB-1), pro-inflammatory cytokines (IFN-γ, IL-1α, IL-1β, IL-18) and chemokines (IL-8) which are related to M1 macrophage activation. Furthermore, the levels of these signaling proteins increase with the degree of mechanical damage induced by boiling histotripsy. Together, the results presented can suggest that boiling histotripsy could be a potential therapeutic approach for not only mechanically destroying solid tumours (e.g., breast cancer) but also promoting immunogenic cell death via TNF-induced necrosis to trigger antitumour immunity.

Histotripsy in collagenous tendons

Tendon injuries comprise 45% of the 66 million musculoskeletal injuries each year with annual costs of $114 billion. Conservative therapies to treat injured tendon produce mixed success rates. Histotripsy is a high intensity focused ultrasound modality that creates and oscillates bubbles to fractionate soft tissues in a well-defined focal volume; however, highly collagenous tissues like tendon have proven resistant to histotripsy. The goal here is to explore acoustic parameters for mechanical fractionation of tendons. Large animal Achilles tendons were exposed to HIFU at 1.07-3.68 MHz with 0.005-20 ms pulses repeated at 1-1000 Hz for 15-60 s with acoustic pressures up to p+ = 97 MPa, p- = 27 MPa. A Verasonics research ultrasound imaging system and ATL L7-4 transducer was used to monitor bubble activity during exposure. Tendon samples were fixated and stained with Hematoxylin and Eosin (H&E) for cellular morphology analysis and alpha-nicotinamide dinucleotide diaphorase (αNADH-d) for enzymatic activity analysis. Results showed successful bubble creation in the focal region; however, only 1/90 samples showed focal coagulative necrosis histologically. Future work involves an evaluation of whether bubbles are of insufficient size or collapse strength to mechanically fractionate tendon. [Work supported by Penn State Seed Grant, NIH EB027886, and NSF DGE1255832].

Influence of Magnetic Nanoparticles on the Focused Ultrasound Hyperthermia

Ultrasound hyperthermia is a medical treatment used to increase temperature of tissues. It can be used independently or as a supportive method for an anticancer treatment. The therapeutic efficacy of focused ultrasound hyperthermia can be improved using sonosensitizers, nanoparticles enhancing the attenuation and dissipation of acoustic energy. As sonosensitizers, we propose magnetic nanoparticles owing to their biodegradability, biocompatibility, and simple positioning in tissues using a magnetic field. Focused ultrasound hyperthermia studies were performed using tissue-mimicking phantoms. Temperature changes were measured at various ultrasound powers and distances from the center of the ultrasound focus. Specific absorption rate (SAR) values, describing the power deposition in the tissues during the hyperthermia treatment, were evaluated for the center of the focus point and for various distances from it. The results show that the addition of nanoparticles increases the SAR almost two times compared to that for the pure phantom. The highest SAR is obtained in the ultrasound focus; it decreases with the increase of the distance from the focus.

Numerical Modeling of Ultrasound Propagation in Weakly Heterogeneous Media Using a Mixed-Domain Method

A mixed-domain method (MDM) is presented in this paper for modeling one-way linear/nonlinear wave propagation in biological tissue with arbitrary heterogeneities, in which sound speed, density, attenuation coefficients, and nonlinear coefficients are all spatial varying functions. The present method is based on solving an integral equation derived from a Westervelt-like equation. One-dimensional problems are first studied to verify the MDM and to reveal its limitations. It is shown that this method is accurate for cases with small variation of sound speed. A 2-D case is further studied with focused ultrasound beams to validate the application of the method in the medical field. Results from the MATLAB toolbox k-Wave are used as the benchmark. Normalized root-mean-square (rms) error estimated at the focus of the transducer is 0.0133 when the coarsest mesh (1/3 of the wavelength) is used in the MDM. Fundamental and second-harmonic fields throughout the considered computational domains are compared and good agreement is observed. Overall, this paper demonstrates that the MDM is a computationally efficient and accurate method when used to model wave propagation in biological tissue with relatively weak heterogeneities.

Efficacy of sub-threshold focused ultrasound irradiation against pancreatic cancer xenografts evaluated using magnetic resonance imaging

We investigated the efficacy and optimal period for using magnetic resonance imaging (MRI) to detect effects of sub-threshold focused ultrasound (FUS) irradiation. Nude mice bearing pancreatic cancer xenografts were subjected to MRI and pathology examnation before, and 24 h, 48 h, 2 weeks after irradiation, which were used to evaluate therapeutic effects of FUS. Tumor volumes were lower post-treatment than control group (P < 0.05). The T1WI turbo spin echo (T1WI-TSE) sequence was similar signal before and after treatment. On T1 enhanced scanning sequence (T1WI-SPIR) imaging, ablation lesions appeared as patchy areas of low signal after 24 h and 48 h. After 2 weeks, the ablation lesions contained low signal areas with clear borders. Hematoxylin and eosin (HE) staining revealed small vessels at ablation lesions with no obvious boundary between cell injury areas and normal tumor cells areas in early-stage, while revealed obvious boundaries 2 weeks post-treatment. Terminal deoxynucleotidyl transferase-modified, dUTP nick-end labeling (TUNEL) staining showed cell apoptosis in early-stage, and revealed reduced apoptotic cells and increased necrotic cell areas 2 weeks later. These findings indicate sub-threshold FUS induces pancreatic cancer cell apoptosis and inhibits tumor growth. Contrast-enhanced MRI delineated the ablation lesions better 2 weeks post-treatment than early stage.

Theoretical investigation of transgastric and intraductal approaches for ultrasound-based thermal therapy of the pancreas

Background

The goal of this study was to theoretically investigate the feasibility of intraductal and transgastric approaches to ultrasound-based thermal therapy of pancreatic tumors, and to evaluate possible treatment strategies.

Methods

This study considered ultrasound applicators with 1.2 mm outer diameter tubular transducers, which are inserted into the tissue to be treated by an endoscopic approach, either via insertion through the gastric wall (transgastric) or within the pancreatic duct lumen (intraductal). 8 patient-specific, 3D, transient, biothermal and acoustic finite element models were generated to model hyperthermia (n = 2) and ablation (n = 6), using sectored (210°–270°, n = 4) and 360° (n = 4) transducers for treatment of 3.3–17.0 cm³ tumors in the head (n = 5), body (n = 2), and tail (n = 1) of the pancreas. A parametric study was performed to determine appropriate treatment parameters as a function of tissue attenuation, blood perfusion rates, and distance to sensitive anatomy.

Results

Parametric studies indicated that pancreatic tumors up to 2.5 or 2.7 cm diameter can be ablated within 10 min with the transgastric and intraductal approaches, respectively. Patient-specific simulations demonstrated that 67.1–83.3% of the volumes of four sample 3.3–11.4 cm³ tumors could be ablated within 3–10 min using transgastric or intraductal approaches. 55.3–60.0% of the volume of a large 17.0 cm³ tumor could be ablated using multiple applicator positions within 20–30 min with either transgastric or intraductal approaches. 89.9–94.7% of the volume of two 4.4–11.4 cm³ tumors could be treated with intraductal hyperthermia. Sectored applicators are effective in directing acoustic output away from and preserving sensitive structures. When acoustic energy is directed towards sensitive structures, applicators should be placed at least 13.9–14.8 mm from major vessels like the aorta, 9.4–12.0 mm from other vessels, depending on the vessel size and flow rate, and 14 mm from the duodenum.

Conclusions

This study demonstrated the feasibility of generating shaped or conformal ablative or hyperthermic temperature distributions within pancreatic tumors using transgastric or intraductal ultrasound.

A meta-analysis of palliative treatment of pancreatic cancer with high intensity focused ultrasound

BACKGROUND

Pancreatic adenocarcinoma is currently the fourth-leading cause of cancer-related death. Up to 60-90% of patients with advanced disease suffer cancer-related pain, severely impacting their quality of life. Current management involves primarily pharmacotherapy with opioid narcotics and celiac plexus neurolysis; unfortunately, both approaches offer transient relief and cause undesired side-effects. High intensity focused ultrasound (HIFU) is a non-invasive thermal ablation technique that has been used to treat pancreatic cancer. This meta-analysis aims to evaluate the role of HIFU in pain palliation of advanced unresectable pancreatic adenocarcinoma.

METHODS

An electronic search was performed in PubMed Medline database up to the end of July 2016, for unresectable pancreatic cancer pain palliation with HIFU. Pertinent studies were identified through the PubMed search engine using the following keywords: HIFU, pancreas, pancreatic cancer, pain and palliation. Additional studies were included after manual search of the selected bibliographies. Pain palliation results reported in each study were analyzed using a logit-transformed random-effects model using the inverse variance method, with the DerSimonian-Laird estimator for τ2, and Cochran's Q test for heterogeneity among studies. The I2 was calculated to assess the percentage of the total variability in the different effect size estimates that can be attributed to heterogeneity among the true effects. A rank correlation test of funnel plot asymmetry was done to assess possible publication bias.

RESULTS

The meta-analysis includes a total number of 23 studies with 865 patients, 729 with pancreatic cancer. The population enrolled ranges from 3 patients in the smallest series, up to 61 in the largest study. τ2 (variance among studies) was 0.195, and I2 (percentage of variation among studies) was 40% (95% CI: 1-64%); the Q test p-value was 0.026, indicating significant heterogeneity among studies. Among 639 patients treated with HIFU, 567 complained of pancreatic pain before the treatment and 459 patients experienced partial or complete pain relief after treatment. The random effects estimate of the proportion of patients with pain reduction was 0.81 (95% CI: 0.76-86).

CONCLUSIONS

HIFU appears to be an effective tool for pain palliation in advanced pancreatic cancer. Studies assessing treatment in patients with pancreatic adenocarcinoma are limited by factors such as small sample sizes and heterogeneity in clinical definitions and assessments. Prospective randomized and standardized studies are necessary to confirm the effectiveness of HIFU in relieving pain, and to evaluate for any potential impact on tumor control and patient survival.

Enhanced efficacy of combination heat shock targeted polymer therapeutics with high intensity focused ultrasound

Combination of polymer therapeutics and hyperthermia has been shown to enhance accumulation in selectively heated tumor tissue. The additional use of heat shock (HS)-targeting towards tumor tissues can further enhance accumulation and retention, and improve therapeutic outcomes. In this work, high intensity focused ultrasound (HIFU) was used to generate hyperthermia in prostate tumor tissue. Upregulation of the cell surface HS receptor glucose regulated protein 78 kDa (GRP78) was observed after treatment with HIFU hyperthermia which was then targeted by specific HS-targeting peptides. We used the peptide sequence WDLAWMFRLPVG attached to the side chains of water-soluble N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers containing docetaxel (DOC) conjugated via a lysosomally degradable linker. It was shown that HIFU-mediated HS-targeted copolymer-DOC conjugates improved treatment efficacy in a murine prostate tumor xenograft model. These results show that the use of HIFU hyperthermia in combination with HS-targeted polymer-drug conjugates has potential to improve therapeutic outcomes in prostate cancer treatment.

High-intensity focused ultrasound combined with hysteroscopic resection to treat retained placenta accreta

We present a case of retained placenta accreta treated by high-intensity focused ultrasound (HIFU) ablation followed by hysteroscopic resection. The patient was diagnosed as submucosal myoma based on ultrasonography in local clinic. Pathologic examination of several pieces of tumor mass from the hysteroscopic procedure revealed necrotic chorionic villi with calcification. HIFU was performed using an ultrasound-guided HIFU tumor therapeutic system. The ultrasound machine had been used for real-time monitoring of the HIFU procedure. After HIFU treatment, no additional vaginal bleeding or complications were observed. A hysteroscopic resection was performed to remove ablated placental tissue 7 days later. No abnormal vaginal bleeding or discharge was seen after the procedure. The patient was stable postoperatively. We proposed HIFU and applied additional hysteroscopic resection for a safe and effective method for treating retained placenta accreta to prevent complications from the remaining placental tissue and to improve fertility options.

High intensity focused ultrasound (HIFU) applied to hepato-bilio-pancreatic and the digestive system-current state of the art and future perspectives

BACKGROUND

High intensity focused ultrasound (HIFU) is emerging as a valid minimally-invasive image-guided treatment of malignancies. We aimed to review to current state of the art of HIFU therapy applied to the digestive system and discuss some promising avenues of the technology.

METHODS

Pertinent studies were identified through PubMed and Embase search engines using the following keywords, combined in different ways: HIFU, esophagus, stomach, liver, pancreas, gallbladder, colon, rectum, and cancer. Experimental proof of the concept of endoluminal HIFU mucosa/submucosa ablation using a custom-made transducer has been obtained in vivo in the porcine model.

RESULTS

Forty-four studies reported on the clinical use of HIFU to treat liver lesions, while 19 series were found on HIFU treatment of pancreatic cancers and four studies included patients suffering from both liver and pancreatic cancers, reporting on a total of 1,682 and 823 cases for liver and pancreas, respectively. Only very limited comparative prospective studies have been reported.

CONCLUSIONS

Digestive system clinical applications of HIFU are limited to pancreatic and liver cancer. It is safe and well tolerated. The exact place in the hepatocellular carcinoma (HCC) management algorithm remains to be defined. HIFU seems to add clear survival advantages over trans arterial chemo embolization (TACE) alone and similar results when compared to radio frequency (RF). For pancreatic cancer, HIFU achieves consistent cancer-related pain relief. Further research is warranted to improve targeting accuracy and efficacy monitoring. Furthermore, additional work is required to transfer this technology on appealing treatments such as endoscopic HIFU-based therapies.

Clinical applications of low-intensity pulsed ultrasound and its potential role in urology

Low-intensity pulsed ultrasound (LIPUS) is a form of ultrasound that delivered at a much lower intensity (<3 W/cm²) than traditional ultrasound energy and output in the mode of pulse wave, and it is typically used for therapeutic purpose in rehabilitation medicine. LIPUS has minimal thermal effects due to its low intensity and pulsed output mode, and its non-thermal effects which is normally claimed to induce therapeutic changes in tissues attract most researchers’ attentions. LIPUS have been demonstrated to have a rage of biological effects on tissues, including promoting bone-fracture healing, accelerating soft-tissue regeneration, inhibiting inflammatory responses and so on. Recent studies showed that biological effects of LIPUS in healing morbid body tissues may be mainly associated with the upregulation of cell proliferation through activation of integrin receptors and Rho/ROCK/Src/ERK signaling pathway, and with promoting multilineage differentiation of mesenchyme stem/progenitor cell lines through ROCK-Cot/Tpl2-MEK-ERK signaling pathway. Hopefully, LIPUS may become an effective clinical procedure for the treatment of urological diseases, such as chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), erectile dysfunction (ED), and stress urinary incontinence (SUI) in the field of urology. It still needs an intense effort for basic-science and clinical investigators to explore the biomedical applications of ultrasound.

Retrospective analysis of high intensity focused ultrasound combined with S-1 in the treatment of metastatic pancreatic cancer after failure of gemcitabine

The purpose of this study was to verify the efficacy and safety of high intensity focused ultrasound therapy (HIFU) combined with S-1 in the treatment of metastatic pancreatic cancer after failure of gemcitabine (GEM). In total, 120 patients with GEM-refractory PC who received HIFU and S-1 between Aug 2012 and December 2014 were randomly assigned to 2 groups. The patients in group A (n = 61) received HIFU in combination with S-1 and those in group B (n = 59) were given S-1 alone. S-1 was administered orally twice a day on days 1-14. Cycles were repeated every 21 days. The follow up time was 3~19 months in both groups. The median overall survival (OS) time and progression free survival (PFS) were analysed by Kaplan-Meier method and Logrank test. The pain remission rate of the two groups was compared by χ(2) test. Patient characteristics and prognostic factors were compared. Patient characteristics did not significantly differ between the 2 groups. Median OS was significantly longer in group A (10.3 months) than in group B (6.6 months, P = 0.000). Median PFS was also significantly longer in group A than in group B (5.1 months vs 2.3 months, P = 0.000). Meanwhile, the pain remission rate was markedly higher in group A than in group B (57% vs. 20%, P = 0.000). There were mild side effects and no significant difference was observed between the two groups. The treatment effect was independently associated with a good outcome. HIFU in combination with S-1 might be effective and well tolerated as salvage chemotherapy in the treatment for metastatic pancreatic cancer.

Harmonic motion imaging for abdominal tumor detection and high-intensity focused ultrasound ablation monitoring: an in vivo feasibility study in a transgenic mouse model of pancreatic cancer

Harmonic motion imaging (HMI) is a radiationforce- based elasticity imaging technique that tracks oscillatory tissue displacements induced by sinusoidal ultrasonic radiation force to assess the resulting oscillatory displacement denoting the underlying tissue stiffness. The objective of this study was to evaluate the feasibility of HMI in pancreatic tumor detection and high-intensity focused ultrasound (HIFU) treatment monitoring. The HMI system consisted of a focused ultrasound transducer, which generated sinusoidal radiation force to induce oscillatory tissue motion at 50 Hz, and a diagnostic ultrasound transducer, which detected the axial tissue displacements based on acquired radio-frequency signals using a 1-D cross-correlation algorithm. For pancreatic tumor detection, HMI images were generated for pancreatic tumors in transgenic mice and normal pancreases in wild-type mice. The obtained HMI images showed a high contrast between normal and malignant pancreases with an average peak-to-peak HMI displacement ratio of 3.2. Histological analysis showed that no tissue damage was associated with HMI when it was used for the sole purpose of elasticity imaging. For pancreatic tumor ablation monitoring, the focused ultrasound transducer was operated at a higher acoustic power and longer pulse length than that used in tumor detection to simultaneously induce HIFU thermal ablation and oscillatory tissue displacements, allowing HMI monitoring without interrupting tumor ablation. HMI monitoring of HIFU ablation found significant decreases in the peak-to-peak HMI displacements before and after HIFU ablation with a reduction rate ranging from 15.8% to 57.0%. The formation of thermal lesions after HIFU exposure was confirmed by histological analysis. This study demonstrated the feasibility of HMI in abdominal tumor detection and HIFU ablation monitoring.

Pulsed High-Intensity Focused Ultrasound Enhances Delivery of Doxorubicin in a Preclinical Model of Pancreatic Cancer

Pancreatic cancer is characterized by extensive stromal desmoplasia, which decreases blood perfusion and impedes chemotherapy delivery. Breaking the stromal barrier could both increase perfusion and permeabilize the tumor, enhancing chemotherapy penetration. Mechanical disruption of the stroma can be achieved using ultrasound-induced bubble activity-cavitation. Cavitation is also known to result in microstreaming and could have the added benefit of actively enhancing diffusion into the tumors. Here, we report the ability to enhance chemotherapeutic drug doxorubicin penetration using ultrasound-induced cavitation in a genetically engineered mouse model (KPC mouse) of pancreatic ductal adenocarcinoma. To induce localized inertial cavitation in pancreatic tumors, pulsed high-intensity focused ultrasound (pHIFU) was used either during or before doxorubicin administration to elucidate the mechanisms of enhanced drug delivery (active vs. passive drug diffusion). For both types, the pHIFU exposures that were associated with high cavitation activity resulted in disruption of the highly fibrotic stromal matrix and enhanced the normalized doxorubicin concentration by up to 4.5-fold compared with controls. Furthermore, normalized doxorubicin concentration was associated with the cavitation metrics (P < 0.01), indicating that high and sustained cavitation results in increased chemotherapy penetration. No significant difference between the outcomes of the two types, that is, doxorubicin infusion during or after pHIFU treatment, was observed, suggesting that passive diffusion into previously permeabilized tissue is the major mechanism for the increase in drug concentration. Together, the data indicate that pHIFU treatment of pancreatic tumors when resulting in high and sustained cavitation can efficiently enhance chemotherapy delivery to pancreatic tumors. .

Endoscopic high-intensity focused US: technical aspects and studies in an in vivo porcine model (with video)

BACKGROUND

High-intensity focused US (HIFU) is becoming more widely used for noninvasive and minimally invasive ablation of benign and malignant tumors. Recent studies suggest that HIFU can also enhance targeted drug delivery and stimulate an antitumor immune response in many tumors. However, targeting pancreatic and liver tumors by using an extracorporeal source is challenging due to the lack of an adequate acoustic window. The development of an EUS-guided HIFU transducer has many potential benefits including improved targeting, decreased energy requirements, and decreased potential for injury to intervening structures.

OBJECTIVE

To design, develop, and test an EUS-guided HIFU transducer for endoscopic applications.

DESIGN

A preclinical, pilot characterization and feasibility study.

SETTING

Academic research center.

PATIENTS

Studies were performed in an in vivo porcine model.

INTERVENTION

Thermal ablation of in vivo porcine pancreas and liver was performed with EUS-guided focused US through the gastric tract.

RESULTS

The transducer successfully created lesions in gel phantoms and ex vivo bovine livers. In vivo studies demonstrated that targeting and creating lesions in the porcine pancreas and liver are feasible.

LIMITATIONS

This was a preclinical, single-center feasibility study with a limited number of subjects.

CONCLUSION

An EUS-guided HIFU transducer was successfully designed and developed with dimensions that are appropriate for endoscopic use. The feasibility of performing EUS-guided HIFU ablation in vivo was demonstrated in an in vivo porcine model. Further development of this technology will allow endoscopists to perform precise therapeutic ablation of periluminal lesions without breaching the wall of the gastric tract.

Dynamic contrast-enhanced ultrasonographic (DCE-US) assessment of the early response after combined gemcitabine and HIFU with low-power treatment for the mouse xenograft model of human pancreatic cancer

PURPOSE

To assess therapeutic efficacy of gemcitabine and HIFU for a mouse model of pancreatic cancer, and the role of DCE-US for predicting early treatment response compared with pathology.

MATERIALS AND METHODS

In 48 PANC-1- nude mice (G1, HIFU_higher power [n = 14]; G2, gemcitabine [n = 12]; G3, combined gemcitabine and HIFU_low power [n = 12]; and G4, control [n = 10]), pulsed HIFU or gemcitabine therapy was used. DCE-US was performed 1 day before and after first treatment. Seven DCE-US perfusion parameters were obtained. Therapeutic efficacy was estimated using necrotic fraction and apoptosis. Correlation between tumour size and US perfusion parameters was analysed.

RESULTS

Pathology results showed that combined gemcitabine and HIFU using low-power treatment had a more effective response than other treatments, including in the control group, i.e. necrotic fraction: 40.5 ± 4.9 vs. 16.9 ± 8.0, p = 0.000 and apoptosis: 44.3 ± 29.4 vs. 7.9 ± 4.9, p = 0.002. In this group, US perfusion parameters, including peak intensity (22.6 ± 22.6 vs. 9.6 ± 6.3, p = 0.002), AUC (961.8 ± 96.9 vs. 884.4 ± 91.4, p = 0.000), and AUCout (799.9 ± 75.6 vs. 747.1 ± 77.9, p = 0.000), had significantly decreased 1 day following first treatment (p < 0.05). In addition, peak intensity, AUC, and AUCout showed a tendency to decrease in treated groups. Alternatively, peak intensity, AUC, and AUCout showed a tendency to increase in control group.

CONCLUSION

Gemcitabine and HIFU were more effective and safer than other treatments. US perfusion parameters were useful for predicting early therapeutic response 1 day following treatment.

KEY POINTS

Recently, treatment of pancreatic cancer has changed based on a multidisciplinary approach. Combined gemcitabine_HIFU demonstrated more effective therapeutic response than other treatments. DCE-US is useful for predicting early therapeutic response 1 day after treatment. In the combined group, PI, AUC, and AUC (out) decreased 1 day after treatment.

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.

Ultrasound-guided tissue fractionation by high intensity focused ultrasound in an in vivo porcine liver model

The clinical use of high intensity focused ultrasound (HIFU) therapy for noninvasive tissue ablation has been recently gaining momentum. In HIFU, ultrasound energy from an extracorporeal source is focused within the body to ablate tissue at the focus while leaving the surrounding organs and tissues unaffected. Most HIFU therapies are designed to use heating effects resulting from the absorption of ultrasound by tissue to create a thermally coagulated treatment volume. Although this approach is often successful, it has its limitations, such as the heat sink effect caused by the presence of a large blood vessel near the treatment area or heating of the ribs in the transcostal applications. HIFU-induced bubbles provide an alternative means to destroy the target tissue by mechanical disruption or, at its extreme, local fractionation of tissue within the focal region. Here, we demonstrate the feasibility of a recently developed approach to HIFU-induced ultrasound-guided tissue fractionation in an in vivo pig model. In this approach, termed boiling histotripsy, a millimeter-sized boiling bubble is generated by ultrasound and further interacts with the ultrasound field to fractionate porcine liver tissue into subcellular debris without inducing further thermal effects. Tissue selectivity, demonstrated by boiling histotripsy, allows for the treatment of tissue immediately adjacent to major blood vessels and other connective tissue structures. Furthermore, boiling histotripsy would benefit the clinical applications, in which it is important to accelerate resorption or passage of the ablated tissue volume, diminish pressure on the surrounding organs that causes discomfort, or insert openings between tissues.

Synergistic effects of glycated chitosan with high-intensity focused ultrasound on suppression of metastases in a syngeneic breast tumor model

Stimulation of the host immune system is crucial in cancer treatment. In particular, nonspecific immunotherapies, when combined with other traditional therapies such as radiation and chemotherapy, may induce immunity against primary and metastatic tumors. In this study, we demonstrate that a novel, non-toxic immunoadjuvant, glycated chitosan (GC), decreases the motility and invasion of mammalian breast cancer cells in vitro and in vivo. Lung metastatic ratios were reduced in 4T1 tumor-bearing mice when intratumoral GC injection was combined with local high-intensity focused ultrasound (HIFU) treatment. We postulate that this treatment modality stimulates the host immune system to combat cancer cells, as macrophage accumulation in tumor lesions was detected after GC-HIFU treatment. In addition, plasma collected from GC-HIFU-treated tumor-bearing mice exhibited tumor-specific cytotoxicity. We also investigated the effect of GC on epithelial–mesenchymal transition-related markers. Our results showed that GC decreased the expression of Twist-1 and Slug, proto-oncogenes commonly implicated in metastasis. Epithelial-cadherin, which is regulated by these genes, was also upregulated. Taken together, our current data suggest that GC alone can reduce cancer cell motility and invasion, whereas GC-HIFU treatment can induce immune responses to suppress tumor metastasis in vivo.

In vitro methods for evaluating therapeutic ultrasound exposures: present-day models and future innovations

Although preclinical experiments are ultimately required to evaluate new therapeutic ultrasound exposures and devices prior to clinical trials, in vitro experiments can play an important role in the developmental process. A variety of in vitro methods have been developed, where each of these has demonstrated their utility for various test purposes. These include inert tissue-mimicking phantoms, which can incorporate thermocouples or cells and ex vivo tissue. Cell-based methods have also been used, both in monolayer and suspension. More biologically relevant platforms have also shown utility, such as blood clots and collagen gels. Each of these methods possesses characteristics that are well suited for various well-defined investigative goals. None, however, incorporate all the properties of real tissues, which include a 3D environment and live cells that may be maintained long-term post-treatment. This review is intended to provide an overview of the existing application-specific in vitro methods available to therapeutic ultrasound investigators, highlighting their advantages and limitations. Additional reporting is presented on the exciting and emerging field of 3D biological scaffolds, employing methods and materials adapted from tissue engineering. This type of platform holds much promise for achieving more representative conditions of those found in vivo, especially important for the newest sphere of therapeutic applications, based on molecular changes that may be generated in response to non-destructive exposures.

Low intensity ultrasound promotes the sensitivity of rat brain glioma to Doxorubicin by down-regulating the expressions of p-glucoprotein and multidrug resistance protein 1 in vitro and in vivo

The overall prognosis for malignant glioma is extremely poor, and treatment options are limited in part because of multidrug resistant proteins. Our previous findings suggest low intensity ultrasound (LIUS) can induce apoptosis of glioma cells. Given this finding, we were interested in determining if LIUS could help treat glioma by inhibiting multidrug resistant proteins, and if so, which pathways are involved. In this study, the toxicity sensitivity and multidrug resistance proteins of glioma induced by LIUS were investigated using CCK-8, immunohistochemistry, immunofluorency, and RT-PCR in tissue samples and cultured cells. LIUS inhibited increase of C6 cells in an intensity- and time-dependent manner. The toxicity sensitivity of C6 cells increased significantly after LIUS sonication (intensity of 142.0 mW/cm²) or Doxorubicin (DOX) at different concentration, particularly by the combination of LIUS sonication and DOX. The expressions of P-gp and MRP1 decreased significantly post-sonication at intensity of 142.0 mW/cm² both in vitro and in vivo. The expressions of p110 delta (PI3K), NF-κB-p65, Akt/PKB, and p-Akt/PKB were downregulated by LIUS sonication and DOX treatment separately or in combination at the same parameters in rat glioma. These results indicate that LIUS could increase the toxicity sensitivity of glioma by down-regulating the expressions of P-gp and MRP1, which might be mediated by the PI3K/Akt/NF-κB pathway.

High-intensity focused ultrasound: advances in technology and experimental trials support enhanced utility of focused ultrasound surgery in oncology

High-intensity focused ultrasound (HIFU) is a rapidly maturing technology with diverse clinical applications. In the field of oncology, the use of HIFU to non-invasively cause tissue necrosis in a defined target, a technique known as focused ultrasound surgery (FUS), has considerable potential for tumour ablation. In this article, we outline the development and underlying principles of HIFU, overview the limitations and commercially available equipment for FUS, then summarise some of the recent technological advances and experimental clinical trials that we predict will have a positive impact on extending the role of FUS in cancer therapy.

Higher dosage of HIFU treatment may lead to higher and longer efficacy for moderate to severe perennial allergic rhinitis

OBJECTIVES

This study was to compare the efficacies and side effects of high intensity focused ultrasound (HIFU) treatment for perennial allergic rhinitis (PAR) with regular and increased dosage.

STUDY DESIGN

A prospectively assembled cohort was retrospectively analyzed through visual analogue scale (VAS).

METHODS

Regular dosage of HIFU treatment was applied to 56 PAR patients in group A. An increased dosage as twice as the regular one was applied to 48 patients in group B. Nasal obstruction, sneezing, rhinorrhea and rhinocnesmus, which were recognized as the four main symptoms of allergic rhinitis (AR), were evaluated before treatment, 3 months after treatment, and 1 year after treatment. The satisfaction of patients was also evaluated at 1 year postoperatively. Biopsy of the inferior turbinate and morphometric analysis were applied to 11 patients in group A and 10 in group B before HIFU treatment and 3 months after treatment.

RESULTS

Comparing the AR symptoms before treatment, There is no statistical difference observed between group A and B (p>0.05). The four main symptoms at 3 months and 1 year after treatment were all significantly improved (p<0.01) in both group A and B. The VAS scores of AR symptoms in Group B were lower than those in Group A at the same stage after treatment, especially at 1 year after treatment (p<0.05). Comparing the results at 3 months and 1 year after treatment, a tendency of recurrence of these symptoms was observed statistically in group A (p<0.05), but not in group B (p>0.05). More cases of nasal dryness and perirhinal swelling were found in group B than those in group A (p<0.05), while all side effects were mild and temporary. Patients in group B were more satisfied than those in group A (p=0.0866 >0.05), though not statistically significant. More reduction of the eosinophils, other inflammatory cells, and the submucosal glands was observed after HIFU treatment in group B than that in group A (p<0.05).

CONCLUSIONS

A proper increment of HIFU dosage may be recommended to meet the needs of more improvement of AR symptoms and less recurrence.