Pathological changes in human malignant carcinoma treated with high-intensity focused ultrasound

Noninvasive body sculpting technologies with an emphasis on high-intensity focused ultrasound

BACKGROUND

Body-sculpting procedures are becoming increasingly popular in the United States. Although surgical lipoplasty remains the most common body sculpting procedure, a demand exists for noninvasive alternatives capable of reducing focal adiposity without the risks of adverse events (AEs) associated with invasive excisional body-sculpting procedures.

METHODS

This report describes the mechanism of action, efficacy, safety, and tolerability of cryolipolysis, radiofrequency ablation, low-level external laser therapy, injection lipolysis, low-intensity nonthermal ultrasound, and high-intensity focused ultrasound (HIFU), with an emphasis on thermal HIFU. The articles cited were identified via a PubMed search, with additional article citations identified by manual searching of the reference lists of articles identified through the literature search.

RESULTS

Each of the noninvasive treatments reviewed can be administered on an outpatient basis. These treatments generally have fewer complications than lipoplasty and require little or no anesthesia or analgesia. However, HIFU is the only treatment that can produce significant results in a single treatment, and only radiofrequency, low-level laser therapy, and cryolipolysis have been approved for use in the United States. Early clinical data on HIFU support its efficacy and safety for body sculpting. In contrast, radiofrequency, laser therapy, and injection lipolysis have been associated with significant AEs.

CONCLUSIONS

The published literature suggests that noninvasive body-sculpting techniques such as radiofrequency ablation, cryolipolysis, external low-level lasers, laser ablation, nonthermal ultrasound, and HIFU may be appropriate options for nonobese patients requiring modest reduction of adipose tissue.

The effect of the scanning pathway in high-intensity focused ultrasound therapy on lesion production

Because tumors are much larger in size compared with the beam width of high-intensity focused ultrasound (HIFU), raster scanning throughout the entire target is conventionally performed for HIFU thermal ablation. Thermal diffusion affects the temperature elevation and the consequent lesion formation. As a result, the lesion will grow continuously over the course of HIFU therapy. The purpose of this study was to investigate the influence of scanning pathways on the overall thermal lesion. Two new scanning pathways, spiral scanning from the center to the outside and spiral scanning from the outside to the center, were proposed with the same HIFU parameters (power and exposure time) for each treatment spot. The lesions produced in the gel phantom and bovine liver were compared with those using raster scanning. Although more uniform lesions can be achieved using the new scanning pathways, the produced lesion areas (27.5 ± 12.3 mm(2) and 65.2 ± 9.6 mm(2), respectively) in the gel phantom are significantly smaller (p < 0.05) than those using raster scanning (92.9 ± 11.8 mm(2)). Furthermore, the lesion patterns in the gel phantom and bovine liver were similar to the simulations using temperature and thermal dose-threshold models, respectively. Thermal diffusion, the scanning pathway and the biophysical aspects of the target all play important roles in HIFU lesion production. By selecting the appropriate scanning pathway and varying the parameters as ablation progresses, HIFU therapy can achieve uniform lesions while minimizing the total delivered energy and treatment time.

Treatment of small hepatocellular carcinomas with US-guided high-intensity focused ultrasound

High-intensity focused ultrasound (HIFU) is a noninvasive method that can cause complete coagulation necrosis without requiring the insertion of any instruments. The purpose of this study was to evaluate the safety and efficacy of HIFU treatment for small liver cancers without performing transcatheter arterial chemoembolization (TACE) or rib resection. HIFU ablation was performed without rib resection or the aid of TACE or percutaneous ethanol injection (PEI) in 12 patients with hepatocelullar carcinoma. The HIFU system (Chongqing Haifu Tech, Chongqing, China) was used under ultrasound guidance. All 12 patients completed the treatment without experiencing any adverse events. Complete coagulation was achieved by applying the sonications from the intercostal space when the tumor was located in the right lobe. After treatment, serum alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST) levels were significantly higher than the baseline values; these levels recovered within 1 week. C-reactive protein (CRP) levels increased 1 week after treatment but decreased within 1 month. An epidural anesthetic provided sufficient pain suppression during the procedure. Edema of the subcutaneous tissue was detected in five cases, but the edema disappeared within 1 month. None of the patients developed acute hepatic failure, liver abscess or renal dysfunction. In conclusion, HIFU is effective for the treatment of patients with small liver cancer.

Ultrasound-guided high intensity focused ultrasound treatment for extra-abdominal desmoid tumours: preliminary results

PURPOSE

The aim of this study was to evaluate the feasibility, safety and therapeutic effects of ultrasound (US)-guided high intensity focused US (HIFU) ablation in the treatment of extra-abdominal desmoid tumours.

MATERIALS AND METHODS

From May 2006 to May 2010, ten consecutive patients with pathologically proven extra-abdominal desmoid tumours were treated by US-guided HIFU ablation. Eight patients with multiple recurrent tumours were treated with a palliative aim, two patients with new solitary tumours were treated with a curative aim. The mean size of the largest tumour was 9.2 cm (range 5.9-12.8 cm). An acoustic power of 300-500 W was used according to the echogenic changes after energy exposure, intermittent HIFU exposure of 2-3 s was applied until the planned target area became hyperechoic on US. Outcome of HIFU ablation was observed by serial contrast-enhanced imaging examinations during follow up.

RESULTS

HIFU ablation was successfully performed without major complications. Large volume coagulation necrosis was obtained in all patients. During a mean follow up of 30 months (range 8-55 months), the treated tumours (n = 25) shrank significantly (>50% in volume). Complete tumour necrosis was observed in the two patients with solitary new tumours. Two patients received repeat HIFU ablation for enlarged residual tumours. No tumour spread along the treated area was observed in any patient.

CONCLUSION

US-guided HIFU ablation could be used as an effective minimally invasive therapy for local control of extra-abdominal desmoid tumours.

Focused ultrasound surgery in oncology: overview and principles

Focused ultrasound surgery (FUS) is a noninvasive image-guided therapy and an alternative to surgical interventions. It presents an opportunity to revolutionize cancer therapy and to affect or change drug delivery of therapeutic agents in new focally targeted ways. In this article the background, principles, technical devices, and clinical cancer applications of image-guided FUS are reviewed.

Locoregional therapy for hepatocellular carcinoma

Locoregional therapies for hepatocellular carcinoma have progressed greatly in the last 30 years, beginning with the introduction of chemoembolization. Embolization techniques have evolved with the use of drug-eluting beads and radioembolization with yttrium-90. In the last 10 years, several new ablation techniques were developed including radiofrequency ablation, microwave ablation, cryoablation, laser ablation, and irreversible electroporation. Isolated or in combination, these techniques have already shown that they can improve patient survival and/or provide acceptable palliation.

Concurrent chemotherapy and pulsed high-intensity focused ultrasound therapy for the treatment of unresectable pancreatic cancer: initial experiences

Objective

This study was performed to evaluate the potential clinical value of concurrent chemotherapy and pulsed high intensity focused ultrasound (HIFU) therapy (CCHT), as well as the safety of pulsed HIFU, for the treatment of unresectable pancreatic cancer.

Materials and Methods

Twelve patients were treated with HIFU from October 2008 to May 2010, and three of them underwent CCHT as the main treatment (the CCHT group). The overall survival (OS), the time to tumor progression (TTP), the complications and the current performance status in the CCHT and non-CCHT groups were analyzed. Nine patients in the non-CCHT group were evaluated to determine why CCHT could not be performed more than twice.

Results

The OS of the three patients in the CCHT group was 26.0, 21.6 and 10.8 months, respectively, from the time of diagnosis. Two of them were alive at the time of preparing this manuscript with an excellent performance status, and one of them underwent a surgical resection one year after the initiation of CCHT. The TTP of the three patients in the CCHT group was 13.4, 11.5 and 9.9 months, respectively. The median OS and TTP of the non-CCHT group were 10.3 months and 4.4 months, respectively. The main reasons why the nine patients of the non-CCHT group failed to undergo CCHT more than twice were as follows: pancreatitis (n = 1), intolerance of the pain during treatment (n = 4), palliative use of HIFU for pain relief (n = 1) and a poor physical condition due to disease progression (n = 3). No major complications were encountered except one case of pancreatitis.

Conclusion

This study shows that CCHT is a potentially effective and safe modality for the treatment of unresectable pancreatic cancer.

Findings of multidetector row computed tomography of HCCs treated by HIFU ablation

PURPOSE

We evaluated the efficacy of high-intensity focused ultrasound (HIFU) ablation for hepatocellular carcinoma (HCC), and a long-term study by follow-up multidetector-row computed tomography (CT) was conducted to evaluate the changes occurring in the treatment area following the HIFU ablation.

MATERIALS AND METHODS

HIFU ablation was carried out in 14 patients with small HCCs (≤3 lesions, ≤3cm in diameter). The HIFU system (Chongqing Haifu Tech) was used under ultrasound guidance. The evaluations were performed by follow-up CT at 1 week, 1, 3, 6 and 12 months after the HIFU ablation.

RESULTS

HIFU ablation was carried out successfully in 11 of the 14 patients. At 1 week after the HIFU, a peripheral rim enhancement was found in all cases (100%). This finding was persistent in 6 of the 11 cases (54.5%) at 1 month, and in 1 of the 11 (9%) cases at 3 months after HIFU ablation. In all cases, the rim enhancement disappeared by 6 or 12 months after the HIFU ablation. At the 12 months follow-up, a decrease in the diameter of the ablated lesions was found. The enhancement around the treated area was found to be persistent at the 12 months follow-up in the one case of recurrence of the treated site in which the safety margin was not sufficiently wide. During the follow-up period, there were 2 cases with residual of HCC tumors. We performed radiofrequency ablation (RFA) for these residual tumors after the HIFU ablation.

CONCLUSION

To ascertain the cause of the peripheral enhancement on follow-up CT images after the HIFU ablation, in particular, to determine whether it might be caused by residual tumor or recurrence at the treated site, careful follow-up is important, especially in cases where the safety margin of the ablated area was not sufficiently wide.

Treatment with high intensity focused ultrasound: secrets revealed

For many decades open surgery remained the only way available for local control of body tumors. In order to decrease the patients' morbidity and mortality several image guided minimally invasive procedures have been adopted. High intensity focused ultrasound (HIFU) is an extracorporeal non invasive method for tumor ablation. High intensity ultrasonic waves can be focused to a focal point resulting in lethal elevation of the temperature at the target site with consequent damage of the tumoral cells. The advances in HIFU technology during the past two decades expanded the HIFU applications to include ablation of both benign and malignant tumors with different treatment strategies being implemented for each type. The aim of this review is to introduce the reader to the details of the treatment process including pretreatment preparation, treatment planning, different ablation strategies, patients' after care as well as the follow up regimens for the most common HIFU applications.

Usefulness of US-CT 3D dual imaging for the planning and monitoring of hepatocellular carcinoma treatment using HIFU

PURPOSE

We evaluated the safety and usefulness of high-intensity focused ultrasound (HIFU) assisted by ultrasound-computed tomography three-dimensional (US-CT 3D) dual imaging for the treatment of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

HIFU ablation was performed in 13 patients with small HCC (≤3 lesions, ≤3 cm in diameter). The HIFU system (Chongqing Haifu Tech) was used under ultrasound guidance. By transferring the sagittal or axial plane of the 3D US and the CT volume data into the ZioM900, multiplanar reconstruction images were displayed in a manner resembling conventional monitor US to assist the HIFU treatment.

RESULTS

Overall, 69% (9/13) of the patients in whom good visualization using B-mode sonography could not be obtained because of the influence of multi-reflections, rib shadows, and unclear tumor margins were successfully treated under the guidance of US-CT 3D dual imaging. In 5 of the 13 patients, multi-reflections were responsible for the poor visualization. In 2 cases, the tumor was poorly visualized because of a rib shadow. In one case, the margin of the tumor was too unclear to be detected using ultrasography. The 3D US images obtained as part of the US-CT 3D dual imaging had a high resolution and were useful for examining the area of HCC invasion and for determining the extent of the ablation area. The CT images, which are not influenced by bone shadows or multi-reflections, were useful for detecting the tumors and for visualizing the presence of the intestines in the sonication zone. HIFU treatments were successfully performed in all the patients with the assistance of US-CT 3D dual imaging.

CONCLUSION

US-CT 3D dual imaging is useful for HIFU treatment for HCC, compensating for the occasionally poor visualization provided by US monitor.

High intensity focused ultrasound in clinical tumor ablation

Recent advances in high intensity focused ultrasound (HIFU), which was developed in the 1940s as a viable thermal tissue ablation approach, have increased its popularity. In clinics, HIFU has been applied to treat a variety of solid malignant tumors in a well-defined volume, including the pancreas, liver, prostate, breast, uterine fibroids, and soft-tissue sarcomas. In comparison to conventional tumor/cancer treatment modalities, such as open surgery, radio- and chemo-therapy, HIFU has the advantages of non-invasion, non-ionization, and fewer complications after treatment. Over 100 000 cases have been treated throughout the world with great success. The fundamental principles of HIFU ablation are coagulative thermal necrosis due to the absorption of ultrasound energy during transmission in tissue and the induced cavitation damage. This paper reviews the clinical outcomes of HIFU ablation for applicable cancers, and then summarizes the recommendations for a satisfactory HIFU treatment according to clinical experience. In addition, the current challenges in HIFU for engineers and physicians are also included. More recent horizons have broadened the application of HIFU in tumor treatment, such as HIFU-mediated drug delivery, vessel occlusion, and soft tissue erosion (“histotripsy”). In summary, HIFU is likely to play a significant role in the future oncology practice.

Experimental ablation of the pancreas with high intensity focused ultrasound (HIFU) in a porcine model

The aim of this study was to determine the feasibility and safety of high intensity focused ultrasound's (HIFU) in pancreatic diseases. Twelve pigs were divided into three groups. The pancreases of pigs in Group A were ablated directly with HIFU, but those in Group B and C ablated by extracorporeal HIFU. The pigs in Group C were sacrificed at day 7 after HIFU. Serological parameters were determined pre-operation and post-operation. The entire pancreas was removed for histological examination. Each animal tolerate the HIFU ablation well. The complete necrosis was observed in targeted regions. The margins of the necrotic regions were clearly delineated from the surrounding normal tissues. Infiltration of inflammatory cells and phorocytosis on the boundary were found in group C. Blood and urine amylase levels were relatively steady after HIFU. No acute pancreatitis or severe complications occurred. In conclusion, HIFU ablation on the pancreas was safe and effective in experimental pigs.

Noninvasive thermometry assisted by a dual-function ultrasound transducer for mild hyperthermia

Mild hyperthermia is increasingly important for the activation of temperature-sensitive drug delivery vehicles. Noninvasive ultrasound thermometry based on a 2-D speckle tracking algorithm was examined in this study. Here, a commercial ultrasound scanner, a customized co-linear array transducer, and a controlling PC system were used to generate mild hyperthermia. Because the co-linear array transducer is capable of both therapy and imaging at widely separated frequencies, RF image frames were acquired during therapeutic insonation and then exported for off-line analysis. For in vivo studies in a mouse model, before temperature estimation, motion correction was applied between a reference RF frame and subsequent RF frames. Both in vitro and in vivo experiments were examined; in the in vitro and in vivo studies, the average temperature error had a standard deviation of 0.7°C and 0.8°C, respectively. The application of motion correction improved the accuracy of temperature estimation, where the error range was 1.9 to 4.5°C without correction compared with 1.1 to 1.0°C following correction. This study demonstrates the feasibility of combining therapy and monitoring using a commercial system. In the future, real-time temperature estimation will be incorporated into this system.

Comparison between diffusion-weighted imaging, T2-weighted, and postcontrast T1-weighted imaging after MR-guided, high intensity, focused ultrasound treatment of uterine leiomyomata: preliminary results

PURPOSE

To investigate the comparison between diffusion-weighted imaging (DWI), T2-weighted imaging, (T2WI) and contrast T1-weighted imaging (cT1WI) in uterine leiomyoma following treatment by magnetic resonance imaging-guided, high intensity focused ultrasound surgery (MRg-HIFUS).

METHODS

Twenty one patients (45 +/- 5 yrs) with clinical symptoms of uterine leiomyoma (fibroids) were treated by MRg-HIFUS using an integrated 1.5T MRI-HIFUS system. MRI parameters consisted of DWI, T2WI, and T1-weighted fast spoiled gradient echo before and after contrast. The post-MRg-HIFUS treatment volume in the fibroid was assessed by cT1WI and DWI. Trace apparent diffusion coefficient maps were constructed for quantitative analysis. The regions of the treated uterine tissue were defined by a semisupervised segmentation method called the "eigenimage filter," using both cT1WI and DWI. Signal-to-noise ratios were determined for the T2WI pretreatment images. Segmented regions were tested by a similarity index for congruence. Descriptive, regression, and Bland-Altman statistics were calculated.

RESULTS

All the patients exhibited heterogeneously increased DWI signal intensity localized in the treated fibroid regions and were colocalized with the cT1WI defined area. The mean pretreatment T2WI signal intensity ratios were T2WI/muscle = 1.8 +/- 0.7 and T2WI/myometrium = 0.7 +/- 0.4. The congruence between the regions was significant, with a similarity of 84% and a difference of 8% between the regions. Regression analyses of the cT1WI and DWI segmented treatment volume were found to be significantly correlated (r2 = 0.94, p < 0.05) with the linear equation, (cT1WI) = 1.1 (DWI)-0.66. There is good agreement between the regions defined by cT1WI and DWI in most of the cases as shown from the Bland-Altman plots.

CONCLUSIONS

Diffusion-weighted imaging exhibited excellent agreement, congruence, and correlation with the cT1WI-defined region of treatment in uterine fibroid. Therefore, DWI could be useful as an adjunct for assessing treatment of uterine fibroids by MRg-HIFUS.

Dual-mode IVUS catheter for intracranial image-guided hyperthermia: feasibility study

In this study, we investigated the feasibility of modifying 3-Fr IVUS catheters in several designs to potentially achieve minimally-invasive, endovascular access for image-guided ultrasound hyperthermia treatment of tumors in the brain. Using a plane wave approximation, target frequencies of 8.7 and 3.5 MHz were considered optimal for heating at depths (tumor sizes) of 1 and 2.5 cm, respectively. First, a 3.5-Fr IVUS catheter with a 0.7-mm diameter transducer (30 MHz nominal frequency) was driven at 8.6 MHz. Second, for a low-frequency design, a 220-μm-thick, 0.35 x 0.35-mm PZT-4 transducer--driven at width-mode resonance of 3.85 MHz--replaced a 40-MHz element in a 3.5-Fr coronary imaging catheter. Third, a 5 x 0.5-mm PZT-4 transducer was evaluated as the largest aperture geometry possible for a flexible 3-Fr IVUS catheter. Beam plots and on-axis heating profiles were simulated for each aperture, and test transducers were fabricated. The electrical impedance, impulse response, frequency response, maximum intensity, and mechanical index were measured to assess performance. For the 5 x 0.5-mm transducer, this testing also included mechanically scanning and reconstructing an image of a 2.5-cm-diameter cyst phantom as a preliminary measure of imaging potential.

Ultrasound-guided high-intensity focused ultrasound treatment for needle-track seeding of hepatocellular carcinoma: preliminary results

PURPOSE

To evaluate therapeutic efficacy of ultrasound (US)-guided high-intensity focused ultrasound (HIFU) ablation for treatment of needle-track seeding of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Nine patients with needle-track seeding of HCC were treated as outpatients using US-guided HIFU ablation. The mean size of the lesion was 1.8 cm (range 1.1 to 2.6 cm), two lesions were located on the abdominal wall, seven lesions were located on the chest wall. An acoustic power of 200 to 400 W was used determined by the echo changes after energy exposures, intermittent HIFU exposures of 1 to 2 s were used during treatment. Treatment was considered complete when the entire nodule and a surrounding 0.5 cm margin become hyperechoic on US. The outcome of HIFU ablation was observed by US and contrast-enhanced magnetic resonance imaging during follow up.

RESULTS

HIFU ablation was performed smoothly in all patients, the treatment lasted for 6 to 21 min (mean 12 min). No major complications occurred. During a mean follow up of 10.3 months (range 7-15 months), persistent absence of lesion enhancement was seen in eight patients, one patient developed a recurrent lesion near the treated area, which was successfully treated by a repeat HIFU ablation.

CONCLUSIONS

US-guided HIFU ablation may be an effective treatment for needle-track seeding of HCC.

High-intensity focused ultrasound combined with transarterial chemoembolization for unresectable hepatocellular carcinoma: long-term follow-up and clinical analysis

OBJECTIVE

High-intensity focused ultrasound (HIFU) combined with transarterial chemoembolization (TACE) has been used to treat unresectable HCC, but its long-term effects and major prognostic factors remain to be determined. The purpose of this study was to assess its long-term effects and find major prognostic factors to help us select eligible patients in the future.

METHODS

73 patients with unresectable HCC received follow-up after HIFU+TACE. The variables of sex, age, AFP level, liver function, tumor location, tumor number, tumor size, TNM staging (5th edition), TNM staging (6th edition), portal vein invasion, ultrasonic pathway of HIFU, TACE session and ablation response were evaluated by univariate analysis. Those variables with significant difference were assessed by multivariate analysis.

RESULTS

The mean follow-up time was 11.7±11.1 months (range, 1-60 months). The median survival time and overall survival rates of 1, 2, 3-year were 12 months, 49.1%, 18.8%, 8.4%, respectively. 45.2% patients achieved complete ablation. At the end of follow-up, 51 patients (69.9%) died from tumor progression (27 patients), liver function failure (18 patients), hemorrhage of upper digestive tract (3 patients) and infection (3 patients). 1 with liver abscess, 2 with serious skin burns and 2 with rib fracture were observed after HIFU. On univariate analysis, age (P=0.017), tumor size (P=0.000), tumor number (P=0.039), the 5th edition of TNM staging (P=0.023), portal vein invasion (P=0.02) and ablation response (P=0.000) had significant difference. On multivariate analysis, ablation response (P=0.001) and tumor size (P=0.013) were major prognostic factors.

CONCLUSION

HIFU combined with TACE is a safe method with a low rate of severe complications. As major prognostic factors, ablation response and tumor size may help us predict the survival and select eligible patients clinically.

FOCUS SPLITTING ASSOCIATED WITH PROPAGATION OF FOCUSED ULTRASOUND THROUGH THE RIB CAGE

The effect of focus splitting after propagation of focused ultrasound through a rib cage is investigated theoretically. It is shown that the mechanism of this effect is caused by the interference of waves from two or more spatially separated sources, such as intercostal spaces. Analytical estimates of the parameters of splitting are obtained, i.e., the number of foci, their amplitudes, diameter, and the distance between them, depending on the transducer parameters, as well as the dimensions of the rib cage and position of ribs relative to the radiator. Various configurations of the relative positioning of ribs and radiator are considered; it is shown which of them are the most effective for real surgical operations.

Enhancement of antitumor vaccine in ablated hepatocellular carcinoma by high-intensity focused ultrasound

AIM: To investigate whether tumor debris created by high-intensity focused ultrasound (HIFU) could trigger antitumor immunity in a mouse hepatocellular carcinoma model.

METHODS: Twenty C57BL/6J mice bearing H22 hepatocellular carcinoma were used to generate antitumor vaccines. Ten mice underwent HIFU ablation, and the remaining 10 mice received a sham-HIFU procedure with no ultrasound irradiation. Sixty normal mice were randomly divided into HIFU vaccine, tumor vaccine and control groups. These mice were immunized with HIFU-generated vaccine, tumor-generated vaccine, and saline, respectively. In addition, 20 mice bearing H22 tumors were successfully treated with HIFU ablation. The protective immunity of the vaccinated mice was investigated before and after a subsequent H22 tumor challenge. Using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, the cytotoxicity of splenic lymphocytes co-cultured with H22 cells was determined in vitro before the tumor challenge, and tumor volume and survival were measured in vivo after the challenge in each group. The mechanism was also explored by loading the vaccines with bone marrow-derived dendritic cells (DCs).

RESULTS: Compared to the control, HIFU therapy, tumor-generated and HIFU-generated vaccines significantly increased cytolytic activity against H22 cells in the splenocytes of the vaccinated mice (P < 0.001). The tumor volume was significantly smaller in the HIFU vaccine group than in the tumor vaccine group (P < 0.05) and control group (P < 0.01). However, there was no tumor growth after H22 rechallenge in the HIFU therapy group. Forty-eight-day survival rate was 100% in mice in the HIFU therapy group, 30% in both the HIFU vaccine and tumor vaccine groups, and 20% in the control group, indicating that the HIFU-treated mice displayed significantly longer survival than the vaccinated mice in the remaining three groups (P < 0.001). After bone marrow-derived DCs were incubated with HIFU-generated and tumor-generated vaccines, the number of mature DCs expressing MHC-II⁺, CD80⁺ and CD86⁺ molecules was significantly increased, and interleukin-12 and interferon-γ levels were significantly higher in the supernatants when compared with immature DCs incubated with mouse serum (P < 0.001). However, no differences of the number of mature DCs and cytokine levels were observed between the HIFU-generated and tumor-generated vaccines (P > 0.05).

CONCLUSION: Tumor debris remaining after HIFU can improve tumor immunogenicity. This debris releases tumor antigens as an effective vaccine to develop host antitumor immune response after HIFU ablation.

Therapeutic effects and prognostic factors in high-intensity focused ultrasound combined with chemoembolisation for larger hepatocellular carcinoma

The purpose of this study is to evaluate high-intensity focused ultrasound (HIFU) ablation combined with transcatheter arterial chemoembolisation (TACE) in the treatment of larger hepatocellular carcinoma (HCC). Eighty-nine (89) patients with unrespectable larger HCC were randomised into a TACE group (n=45) and a TACE plus HIFU group (n=44). Therapeutic effects were assessed at follow-up with physical examination, level of serum alpha-fetoprotein and computed tomography or magnetic resonance imaging. All patients were followed up to observe long-term therapeutic effects and evaluated prognostic factors for survival. No severe complication was observed. Follow-up images showed that total effective rate in tumour response accounted for 72.8% in the TACE-HIFU group, which were significantly higher than that of TACE group (44.5%, P<0.05). The 1-, 2-, 3- and 5-year overall survival rates for the TACE-HIFU group were 72.7%, 50.0%, 31.8% and 11.4%, respectively; correspondingly, for the TACE group were 47.2%, 16.7%, 2.8% and 0%, respectively (P<0.01). The 1-, 2-, 3- and 5-year disease-free survival rates for the TACE-HIFU group were 34.1%, 18.2%, 9.1% and 0%, respectively; correspondingly, for the TACE group were 13.9%, 5.6%, 0% and 0%, respectively (P<0.01). TNM stage, portal vein tumour thrombosis and Child-Pugh classification each had a significant effect on the survival. HIFU ablation combined with TACE is safe, effective and a promising approach for the treatment of larger HCC.

Electrode displacement strain imaging of thermally-ablated liver tissue in an in vivo animal model

PURPOSE

Percutaneous thermal ablation is increasingly being used to destroy hepatic tumors in situ. The success of ablative techniques is highly dependent on adequate ablation zone monitoring, and ultrasound-based strain imaging could become a convenient and cost-effective means to delineate ablation zone boundaries. This study investigates in vivo electrode displacement-based strain imaging for monitoring hepatic ablation procedures that are difficult to perform with conventional elastography.

METHODS

a In our method, minute displacements (less than a millimeter) are applied to the unconstrained end of the ablation electrode, resulting in localized tissue deformation within the ablation zone that provides the mechanical stimuli required for strain imaging. This article presents electrode displacement strain images of radiofrequency ablation zones created in porcine liver in vivo (n = 13).

RESULTS

Cross-sectional area measurements from strain images of these ablation zones were obtained using manual and automated segmentation. Area measurements from strain images were highly correlated with areas measured on histopathology images, quantitated using linear regression (R = 0.894, P < 0.001 and R = 0.828, P < 0.001, respectively).

CONCLUSIONS

This study further demonstrates that electrode displacement elastography is capable of providing high-contrast images using widely available commercial ultrasound systems which may potentially be used to assess the extent of thermal ablation zones.

Transcranial magnetic resonance imaging- guided focused ultrasound surgery of brain tumors: initial findings in 3 patients

OBJECTIVE

This work evaluated the clinical feasibility of transcranial magnetic resonance imaging-guided focused ultrasound surgery.

METHODS

Transcranial magnetic resonance imaging-guided focused ultrasound surgery offers a potential noninvasive alternative to surgical resection. The method combines a hemispherical phased-array transducer and patient-specific treatment planning based on acoustic models with feedback control based on magnetic resonance temperature imaging to overcome the effects of the cranium and allow for controlled and precise thermal ablation in the brain. In initial trials in 3 glioblastoma patients, multiple focused ultrasound exposures were applied up to the maximum acoustic power available. Offline analysis of the magnetic resonance temperature images evaluated the temperature changes at the focus and brain surface.

RESULTS

We found that it was possible to focus an ultrasound beam transcranially into the brain and to visualize the heating with magnetic resonance temperature imaging. Although we were limited by the device power available at the time and thus seemed to not achieve thermal coagulation, extrapolation of the temperature measurements at the focus and on the brain surface suggests that thermal ablation will be possible with this device without overheating the brain surface, with some possible limitation on the treatment envelope.

CONCLUSION

Although significant hurdles remain, these findings are a major step forward in producing a completely noninvasive alternative to surgical resection for brain disorders.

Dendritic cells loaded with ultrasound-ablated tumour induce in vivo specific antitumour immune responses

Previous studies have shown that high-intensity focused ultrasound (HIFU) ablation can induce a local inflammation with marked infiltration of dendritic cells (DCs). The purpose of this study was to investigate whether DCs could capture and present activating signals delivered by necrotic tumour cells that remain in situ after HIFU, thus initiating specific antitumour immunity. Tumour debris was derived from a mouse H22 tumour model after HIFU ablation. Bone marrow-derived DCs were loaded with HIFU-treated tumour, tumour lysate and mouse serum. Syngeneic naïve C57BL/6J mice were immunised with three loaded DCs followed by a subsequent H22 tumour challenge. Tumour size and survival were then recorded in each vaccinated mouse. The results showed that both HIFU-ablated tumour and tumour lysate could significantly increase the number of mature DCs and the secretion of IL-12 and IFN-gamma (p<0.001). The proliferation of splenic lymphocytes co-incubated with the loaded-DCs was significantly higher in both HIFU-ablated tumour and tumour lysate groups (p<0.01). Cytotoxocity and TNF-alpha and IFN-gamma secretion of cytotoxic T lymphocytes against H22 cells were significantly higher in HIFU-ablated tumour group than that in tumour lysate group (p<0.01). After the H22 tumour challenge, a significant decrease of tumour volume was observed in HIFU-ablated tumour group (p<0.01). However, there was no statistical difference of long-term survival rates among three groups (p>0.05). It is concluded that DCs can be activated by HIFU-ablated tumour debris and, thus, initiate host specific antitumour immune response after HIFU therapy.

High intensity focused ultrasound in the treatment of abdominal and gynaecological diseases

In recent years high intensity focused ultrasound (HIFU) has received increasing interest as a non-invasive modality for the treatment of tumours of solid organs. Surgeons continue their quest to find the optimal technique whereby a diseased organ can be treated with a minimum of damage to the patient, while providing a comprehensive treatment to produce either cure or resolution of symptoms. Two of the areas in which HIFU is beginning to establish itself as a real therapeutic alternative, are in the treatment of abdominal and gynaecological disease. In this paper, we will review the literature available regarding the use of HIFU in the treatment of various organs: liver, kidney, pancreas, bladder, uterus and vulva.

Complications of High Intensity Focused Ultrasound for Patients with Hepatocellular Carcinoma

High intensity focused ultrasound (HIFU) is a noninvasive treatment modality that induces complete coagulative necrosis of a deep tumor through the intact skin. This study was conducted to analyze and evaluate the complications of HIFU for the treatments of hepatocellular carcinoma. A total of 59 patients with hepatocellular carcinoma, with a total of 72 lessions were enrolled in this study. Tumor size ranged from 2.5 to 14.0 cm in diameter, with a mean diameter of 7.6 cm. All patients had accepted HIFU treatment, and the median number of HIFU sessions was 1.32 per patient. Results: The common complications from HIFU therapy were skin burns of various grades (eight cases of grade 1 skin burns, 48 of grade 2, three cases of 3), and pain in the treatment regions (15 cases of mild pain, 37 cases of moderate pain, 7 cased of severe pain). Other systemic complications were relatively rare and included fever (5 cases), hypertension (8 cases), supraventricular tachycardia (3 cases), mild impairment of hepatic function (48 cases), and mild mpairment of renal function (2 cases). Local damage consisted of acute cholecystitis (2 cases), hematuria (6 cases), cholangiectasis (5 cases), light pericardial effusion (2 cases), impairment of peripheral nerves (10 cases), pleural effusion in the right thorax (3 cases), and impairment of vertebral column (1 case). No gastric or intestinal tract perforation, big vessel rupture, or hepatic rupture occurred. Conclusions: HIFU is a minimally invasive treatment for patients with hepatocellular carcinoma; however, there are some systemic and local complications that should be taken into consideration in evaluating HIFU for therapeutic use.

Acute increases in murine tumor echogenicity after antivascular ultrasound therapy: a pilot preclinical study

OBJECTIVE

This study was designed to determine whether the echogenicity of neoplastic tissues changed as a result of low-intensity insonation and whether such alterations were related to an anti-vascular effect.

METHODS

In 21 mice, implanted melanomas were insonated at either 1, 2, or 3 MHz using low-intensity ultrasound (spatial-average temporal-average intensity, 2.1 W/cm(2)). B-mode (mean gray scale) and contrast-enhanced power Doppler (percentage area of flow) measurements were made on each tumor before and after therapy.

RESULTS

There was an increase in the echogenicity of the tumors with the increase in the frequency of the therapy beam and an accompanying decrease in tumor vascularity.

CONCLUSIONS

Although the mechanisms responsible for the echogenicity change are not fully understood, it appears that an increase in the tumor mean gray scale was, at least in part, related to tissue inhomogeneities formed after disruption of the tumor neovasculature.

Dual-mode intracranial catheter integrating 3D ultrasound imaging and hyperthermia for neuro-oncology: feasibility study

In this study, we investigated the feasibility of an intracranial catheter transducer with dual-mode capability of real-time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. Feasibility is demonstrated in two ways: first by using a 50-element linear array transducer (17 mm x 3.1 mm aperture) operating at 4.4 MHz with our Volumetrics diagnostic scanner and custom, electrical impedance-matching circuits to achieve a temperature rise over 4 degrees C in excised pork muscle, and second, by designing and constructing a 12 Fr, integrated matrix and linear-array catheter transducer prototype for combined RT3D imaging and heating capability. This dual-mode catheter incorporated 153 matrix array elements and 11 linear array elements diced on a 0.2 mm pitch, with a total aperture size of 8.4 mm x 2.3 mm. This 3.64 MHz array achieved a 3.5 degrees C in vitro temperature rise at a 2 cm focal distance in tissue-mimicking material. The dual-mode catheter prototype was compared with a Siemens 10 Fr AcuNav catheter as a gold standard in experiments assessing image quality and therapeutic potential and both probes were used in an in vivo canine brain model to image anatomical structures and color Doppler blood flow and to attempt in vivo heating.

Increased infiltration of activated tumor-infiltrating lymphocytes after high intensity focused ultrasound ablation of human breast cancer

BACKGROUND

Previous studies have shown that high intensity focused ultrasound (HIFU) ablation can induce a distinct inflammatory reaction with marked infiltration of lymphocytes after direct tumor destruction. In this study, we investigated the status of tumor-infiltrating lymphocytes (TILs) after HIFU ablation of human breast cancer and explored mechanisms that may be involved in HIFU-triggered, antitumor immune response.

METHODS

A total of 48 female patients with biopsy-proven breast cancer were divided randomly into 1 of 2 groups: control group (n = 25), in which only modified radical mastectomy was performed, or HIFU group (n = 23), in which HIFU ablation of the primary breast cancer was performed prior to modified radical mastectomy. Using semiquantitative immunohistochemical analysis, tumor-infiltrating T lymphocytes and subsets, B lymphocytes, and natural killer (NK) cells were assessed in all patients. Expression of Fas ligand (FasL), granzyme, and perforin on TILs was also studied in both groups.

RESULTS

TILs infiltrated along the margins of the ablated region in all HIFU-treated neoplasms, and the numbers of tumor-infiltrating CD3, CD4, CD8, CD4/CD8, B lymphocytes, and NK cells was increased significantly in the HIFU group. The number of FasL(+), granzyme(+), and perforin(+) TILs was significantly greater in the HIFU group than in the control group.

CONCLUSION

HIFU ablation induced marked infiltration of CD3, CD4, CD8, B lymphocytes, and NK cells in the treated breast lesions. The number of FasL(+), granzyme(+), and perforin(+) TILs was significantly increased after HIFU treatment.

Comparison of one-dimensional and two-dimensional least-squares strain estimators for phased array displacement data

In this study, the performances of one-dimensional and two-dimensional least-squares strain estimators (LSQSE) are compared. Furthermore, the effects of kernel size are examined using simulated raw frequency data of a widely-adapted hard lesion/soft tissue model. The performances of both methods are assessed in terms of root-mean-squared errors (RMSE), elastographic signal-to-noise ratio (SNRe) and contrast-to-noise ratio (CNRe). RMSE analysis revealed that the 2D LSQSE yields better results for phased array data, especially for larger insonification angles. Using a 2D LSQSE enabled the processing of unfiltered displacement data, in particular for the lateral/horizontal strain components. The SNRe and CNRe analysis showed an improvement in precision and almost no loss in contrast using 2D LSQSE. However, the RMSE images for different kernel sizes revealed that the optimal 2D kernel size depends on the region-of-interest and showed that the LSQ kernel size should be limited to avoid loss in resolution.

High-intensity focused ultrasound in ovarian cancer xenografts

INTRODUCTION

The purpose of this study was to determine whether high-intensity focused ultrasound (HIFU) is an effective treatment for ovarian carcinoma in an athymic nude mouse model.

METHODS

Thirty-nine female athymic nude mice were inoculated subcutaneously with 5-7 x 10(6) SKOV3 human ovarian cancer cells. Thirty-two animals developed tumours and were randomly divided into three groups: HIFU (n=18), sham treatment (n=8) and control (n=6). The sonographic appearance of the tumours during therapy was recorded. After therapy, the tumours were examined transcutaneously by ultrasound every 4 days for 4 weeks. Tissue samples were taken from the treatment sites and histopathologically examined by light or electron microscopy.

RESULTS

Three weeks after HIFU treatment, a 100% reduction in tumour volume was observed in all animals in the HIFU group, whereas tumours in the sham-treated and control groups continued to grow. Pathological examination of HIFU-treated tumour tissue samples showed complete coagulation necrosis of the tumour.

CONCLUSION

Our results indicate that HIFU appears to be an effective therapy for ovarian carcinoma tumours in the athymic nude mouse model. We suggest that it may hold promise for the clinical treatment of late-stage and recurrent ovarian cancer.

New integrated imaging high intensity focused ultrasound probe for transrectal prostate cancer treatment

The present study proposes a new integrated imaging (II) high-intensity focused ultrasound (HIFU) probe intended as an improvement to the Ablatherm prostate cancer treatment. Because of a perforation in the center of the II probe, the expected lesion differs from the one obtained for the original Ablatherm probe. In this paper, the new geometry and the strategy followed to establish the treatment parameters are presented. The original probe has a 40-mm focal length, a 50-mm aperture and is truncated at 31 mm. The II probe has a 45-mm focal length, a 61-mm aperture, a central perforation of 25 mm and is truncated at 31 mm. Both probes operate at 3 MHz. A mathematical model for lesion prediction was used for setting the treatment parameters for the II probe. These parameters should ensure equivalence between the lesions obtained with the original and II probes. Simulation-obtained parameters were validated by in-vitro and in-vivo (on liver of 70 New Zealand rabbits) experiments. The new II probe was used clinically to treat 30 patients. The mean age was 70.9 +/- 5.3 years (SD), the mean prostate volume 26.9 +/- 7.7 mL and the mean serum prostate specific antigen (PSA) concentration before treatment was 9.2 +/- 5.5 ng/mL. Simulations showed that for the II probe acoustical power and duration when the transducer is inactive should be reduced of 14% and 1s. In-vitro and in-vivo experiments confirmed the equivalence between the lesions obtained with the two probes. The lesion volume obtained under in-vitro conditions (for a traversed tissue depth of 16 mm to the focus) was 5 +/- 0.4 cm(3) and 5.1 +/- 0.5 cm(3) for the original and II probes, respectively. Under in-vivo conditions, the lesion volume (for a traversed tissue depth of 18 mm) was 5.3 +/- 1.1 cm(3) and 5.1 +/- 1.1 cm(3) for the original and II probes, respectively. During the clinical trial, a correction of + 1s in the exposure time was required to recreate the same degree of efficacy observed with the original probe (p = 0.97): 66.7 % of negative biopsies and 75% of patients with PSA at 3 mo < or =1 ng/mL. The morbidity observed was minimal and identical to that observed with the original probe.

Current status and future potential of MRI-guided focused ultrasound surgery

The combination of the imaging abilities of magnetic resonance imaging (MRI) with the ability to delivery energy to targets deep in the body noninvasively with focused ultrasound presents a disruptive technology with the potential to significantly affect healthcare. MRI offers precise targeting, visualization, and quantification of temperature changes and the ability to immediately evaluate the treatment. By exploiting different mechanisms, focused ultrasound offers a range of therapies, ranging from thermal ablation to targeted drug delivery. This article reviews recent preclinical and tests clinical of this technology.

Shape-based ultrasound tomography using a Born model with application to high intensity focused ultrasound therapy

A shaped-based ultrasound tomography method is proposed to reconstruct ellipsoidal objects using a linearized scattering model. The method is motivated by the desire to detect the presence of lesions created by high intensity focused ultrasound (HIFU) in applications of cancer therapy. The computational size and limited view nature of the relevant three-dimensional inverse problem renders impractical the use of traditional pixel-based reconstruction methods. However, by employing a shape-based parametrization it is only necessary to estimate a small number of unknowns describing the geometry of the lesion, in this paper assumed to be ellipsoidal. The details of the shape-based nonlinear inversion method are provided. Results obtained from a commercial ultrasound scanner and a tissue phantom containing a HIFU-like lesion demonstrate the feasibility of the approach where a 20 mm x 5 mm x 6 mm ellipsoidal inclusion was detected with an accuracy of around 5%.

Image-guided focused ultrasound ablation of breast cancer: current status, challenges, and future directions

Image-guided focussed ultrasound (FUS) ablation is a non-invasive procedure that has been used for treatment of benign or malignant breast tumours. Image-guidance during ablation is achieved either by using real-time ultrasound (US) or magnetic resonance imaging (MRI). The past decade phase I studies have proven MRI-guided and US-guided FUS ablation of breast cancer to be technically feasible and safe. We provide an overview of studies assessing the efficacy of FUS for breast tumour ablation as measured by percentages of complete tumour necrosis. Successful ablation ranged from 20% to 100%, depending on FUS system type, imaging technique, ablation protocol, and patient selection. Specific issues related to FUS ablation of breast cancer, such as increased treatment time for larger tumours, size of ablation margins, methods used for margin assessment and residual tumour detection after FUS ablation, and impact of FUS ablation on sentinel node procedure are presented. Finally, potential future applications of FUS for breast cancer treatment such as FUS-induced anti-tumour immune response, FUS-mediated gene transfer, and enhanced drug delivery are discussed. Currently, breast-conserving surgery remains the gold standard for breast cancer treatment.