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

Noninvasive thermal ablation of hepatocellular carcinoma by using magnetic resonance imaging-guided focused ultrasound

A number of minimally invasive methods have been tested for the thermal ablation of liver tumors as an alternative to surgical resection. The use of focused ultrasound transducers to ablate deep tumors offers the first completely noninvasive alternative to these techniques. By increasing the flexibility of this technology with modern phased-array transducer design and by combining it with magnetic resonance imaging for targeting and online guidance, a powerful tool results with the potential to offer treatment to a larger population of patients, to reduce trauma to the patient, and to reduce the cost of treatment. In this article, we review previous work with focused ultrasound in the liver and recent experimental results with magnetic resonance imaging guidance.

In vivo feasibility of image-guided transvaginal focused ultrasound therapy for the treatment of intracavitary fibroids

OBJECTIVE

To determine the feasibility of uterine tissue ablation in vivo using a transvaginal focused ultrasound applicator guided by ultrasound imaging.

DESIGN

Randomized in vivo animal study.

SETTING

Academic research environment.

ANIMAL(S)

Healthy anesthetized sheep.

INTERVENTION(S)

Uterine treatment location was determined using a computerized targeting system. Five sonications 10 seconds in duration and averaging 2,000 W/cm(2) of focal ultrasound intensity were applied in each animal's uterus. Animals were euthanized either immediately or 2, 7, or 30 days post-treatment.

MAIN OUTCOME MEASURE(S)

Gross and microscopic analysis of the dissected uterus was used to quantitatively and qualitatively determine the ablated region and treatment side effects.

RESULT(S)

Treatments resulted in coagulative necrosis. Histopathological analysis showed that over 7 days, inflammatory cells appeared and smooth muscle bundles regenerated. By day 30, treated tissues healed and scar tissue formed. None of the animals showed abnormal behavior or medical problems. Complications in three animals were damage to the vaginal wall and colon, possibly due to inadequate applicator cooling and an empty bladder during treatment.

CONCLUSION(S)

Transvaginal image-guided high-intensity focused ultrasound has potential for treating uterine fibroids. Further safety testing of this treatment will prepare it for human use.

Activated anti-tumor immunity in cancer patients after high intensity focused ultrasound ablation

T cell-mediated immune responses represent the main cellular antitumor immunity in cancer patients. Recent studies have shown that that both surgical procedure and radiation therapy could cause the functional suppression of lymphocyte-mediated cellular immunity. The purpose of current study is to evaluate whether high intensity focused ultrasound (HIFU) might change a systemic antitumor immunity, particularly T lymphocyte-mediated immunity in cancer patients. A total of 16 patients with solid malignancies were treated with HIFU. Among them, six patients had osteosarcoma (Enneking stage, II(B)4, III(B) 2), five had hepatocellular carcinoma (TNM stage, III 3, IV 2), and five had renal cell carcinoma (TNM stage, III 2, IV 3). Using flow cytometry technique, T lymphocyte and subset, B lymphocyte and natural killer cell (NK) in the peripheral blood were measured in these patients on the day before HIFU and 7 to 10 d after HIFU. The statistical significance of any observed difference is evaluated by Student's t-test. The results showed a significance increase in the population of CD4(+) lymphocytes (p < 0.01) and the ratio of CD4(+) /CD8(+) (p < 0.05) in the circulation of cancer patients after HIFU treatment. The abnormal levels of CD3(+) lymphocytes returned toward the normal range in two patients, CD4(+)/CD8(+) ratio in 3, CD19(+) lymphocytes in one and cytotoxic NK in one, respectively, in comparison to control values. It is concluded that HIFU could enhance a systemic antitumor cellular immunity in addition to local tumor destruction in patients with solid malignancies.

Analysis of clinical effect of high-intensity focused ultrasound on liver cancer

AIM: To evaluate the clinical effect of high-intensity focused ultrasound (HIFU) in the treatment of patients with liver cancer.

METHODS: HIFU treatment was performed in 100 patients with liver cancer under general anesthesia and by a targeted ultrasound. Evaluation of efficacy was made on the basis of clinical symptoms, liver function tests, AFP, MRI or CT before and after the treatment.

RESULTS: After HIFU treatment, clinical symptoms were relieved in 86.6%(71/82) of patients. The ascites disappeared in 6 patients. ALT (95 ± 44) U/L and AST (114 ± 58) U/L before HIFU treatment were reduced to normal in 83.3%(30/36) and 72.9%(35/48) patients, respectively, after the treatment. AFP was lowered by more than 50% in 65.3%(32/49) patients. After HIFU treatment, MRI or CT findings indicated coagulation necrosis and blood supply reduction or disappearance of tumor in the target region.

CONCLUSION: HIFU can efficiently treat the patients with liver cancer. It will offer a significant noninvasive therapy for local treatment of liver tumor.

Contrast-enhanced ultrasound assessment of tissue response to high-intensity focused ultrasound

We report the use of contrast-enhanced ultrasonography as an immediate means of assessing the clinical response to high-intensity focused ultrasound (US) or HIFU treatment of liver tumours. HIFU is a noninvasive transcutaneous technique for the ablation of tumours that has been shown to destroy tumour vasculature, as well as to cause coagulative necrosis of tumour cells. As a dynamic indicator of tissue perfusion, microbubble contrast agents have already been reported to increase the diagnostic sensitivity of ultrasonography in the detection of liver tumours. This report documents the ability of one i.v. microbubble contrast agent (SonoVue, Bracco, Italy) to delineate the extent of HIFU ablation by comparison of pre- and immediately posttreatment perfusion within the target tumour. Observed changes were seen to correlate well with the ablated volume on histologic evaluation of the treated volume. This is the first time that this imaging technique has been reported in this setting.

Temperature estimation using ultrasonic spatial compound imaging

The feasibility of temperature estimation during high-intensity focused ultrasound therapy using pulse-echo diagnostic ultrasound data has been demonstrated. This method is based upon the measurement of thermally-induced modifications in backscattered RF echoes due to thermal expansion and local changes in the speed of sound. It has been shown that strong ripple artifacts due to the thermo-acoustic lens effect severely corrupt the temperature estimates behind the heated region. We propose here a new imaging technique that improves the temperature estimation behind the heated region and reduces the variance of the temperature estimates in the entire image. We replaced the conventional beamforming on transmit with multiple steered plane wave insonifications using several subapertures. A two-dimensional temperature map is estimated from axial displacement maps between consecutive RF images of identically steered plane wave insonifications. Temperature estimation is then improved by averaging the two-dimensional maps from the multiple steered plane wave insonifications. Experiments were conducted in a tissue-mimicking gelatin-based phantom and in fresh bovine liver.

Extracorporeal high intensity focused ultrasound ablation in the treatment of 1038 patients with solid carcinomas in China: an overview

The ideal treatment of localized cancer should directly cause an irreversible and complete death of tumor cells without damage to surrounding normal tissue. High intensity focused ultrasound (HIFU) is such a potential treatment, which induces a complete coagulative necrosis of a tumor at depth through the intact skin. The idea that using an extracorporeal source of therapeutic ultrasound was introduced more than 50 years ago [J. Gen. Physiol. 26 (1942) 179]. However, up to now, most of the studies on HIFU have been dealing with animal experiments because this extracorporeal technique is very complicated in clinical applications. The purpose of this study is to introduce Chinese clinical experience of using extracorporeal HIFU for the treatment of patients with various kinds of solid tumor. From December 1997 to October 2001, a total of 1038 patients with solid tumors underwent HIFU ablation in China. Among them, 313 patients were treated at the Chongqing University of Medical Sciences, China. Pathological examination showed that the target region presented clear evidence of cellular destruction. Small blood vessels less than 2 mm in diameter were severely damaged. Follow-up diagnostic imaging revealed that there was no, or reduced, blood supply, and no uptake of radioisotope in the treated tumor after HIFU, both indicating a positive therapeutic response and an absence of viable tumor. Imaging at 6-12 months showed obvious regression of the lesion. Four-year follow-up data were significantly observed in patients with hepatocellular carcinoma, osteosarcoma, and breast cancer. An extremely low major complication rate was noted. It is concluded that HIFU ablation is a safe, effective, and feasible modality for the ablation of carcinomas.

High-intensity focused ultrasound for the treatment of liver tumours

High-intensity focused ultrasound (HIFU) has been investigated as a tool for the treatment of cancer for many decades, but is only now beginning to emerge as a potential alternative to conventional therapies. In recent years, clinical trials have evaluated the clinical efficacy of a number of devices worldwide. In Oxford, UK, we have been using the JC HIFU system (HAIFU Technology Company, Chongqing, PR China) in clinical trials since November 2002. This is the first report of its clinical use outside mainland China. The device is non-invasive, and employs an extracorporeal transducer operating at 0.8-1.6 MHz (aperture 12-15 cm, focal length 9-15 cm), operating clinically at Isp (free field) of 5-15 KWcm(-2). The aims of the trials are to evaluate the safety and performance of the device. Performance is being evaluated through two parallel protocols. One employs radiological assessment of response with the use of follow-up magnetic resonance imaging and microbubble-contrast ultrasound. In the other, histological assessment will be made following elective surgical resection of the HIFU treated tumours. Eleven patients with liver tumours have been treated with HIFU to date. Adverse events include transient pain and minor skin burns. Observed response from the various assessment modalities is discussed.

Circulating tumor cells in patients with solid malignancy treated by high-intensity focused ultrasound

The theoretical possibility that exposure of a solid malignancy to high-intensity focused ultrasound (US), or HIFU, could lead to an increased rate of metastasis still remains. Using reverse transcriptase polymerase chain reaction (RT-PCR), the potential risk of hematogenous dissemination was assessed in HIFU-treated patients with solid malignancy. RT-PCR can demonstrate the presence or absence of specific RNA fragments. On the day before HIFU ablation, 5-mL peripheral blood samples were collected, and again 5 to 7 days after HIFU, from 26 enrolled patients (hepatocellular carcinoma, HCC: 10; osteosarcoma: 16). Total RNA was isolated and RT-PCR was performed to analyze the mRNA expression of (alpha-fetoprotein (AFP) and bone-specific alkaline phosphatase (BALP) genes. Positive AFP mRNA expression was preoperatively detected in 8 of 10 patients with HCC. In the postoperative specimens, positive expression was also detected in 8 of 10 patients. In 2 patients, circulating tumor cells were found preoperatively, but not postoperatively. Conversely, 2 patients with no circulating tumor cells preoperatively were found to have circulating tumor cells after HIFU. Of 16 osteosarcoma patients, 12 patients had circulating tumor cells and 4 had none. After HIFU treatment, 2 of the 12 patients had converted from presence to absence of circulating cells and the remaining 4 patients remained negative. It is concluded that patients undergoing complete HIFU ablation may demonstrate conversion from presence to absence of circulating tumor-specific marker mRNA, and that HIFU would not enhance the potential risk of metastasis in patients with malignant diseases.

A randomised clinical trial of high-intensity focused ultrasound ablation for the treatment of patients with localised breast cancer

High-intensity focused ultrasound (HIFU) is a noninvasive treatment that induces complete coagulative necrosis of a tumour at depth through the intact skin. This study was to explore the possibility of using HIFU for the treatment of patients with localised breast cancer in a controlled clinical trial. A total of 48 women with biopsy-proven breast cancer (T(1-2), N(0-2), M0) were randomised to the control group in which modified radical mastectomy was performed, and the HIFU group in which an extracorporeal HIFU ablation of breast cancer was followed by modified radical mastectomy. Short-term follow-up, pathologic and immunohistochemical stains were performed to assess the therapeutic effects on tumour and complications of HIFU. The results showed that no severe side effect was observed in the HIFU-treated patients. Pathologic findings revealed that HIFU-treated tumour cells underwent complete coagulative necrosis, and tumour vascular vessels were severely damaged. Immunohistochemical staining showed that no expression of PCNA, MMP-9, and CD44v6 was detected within the treated tumour cells in the HIFU group, indicating that the treated tumour cells lost the abilities of proliferation, invasion, and metastasis. It is concluded that, as a noninvasive therapy, HIFU could be effective, safe, and feasible in the extracorporeal treatment of localised breast cancer.

Preliminary experience using high intensity focused ultrasound for the treatment of patients with advanced stage renal malignancy

PURPOSE

We present the preliminary results of patients with advanced stage renal malignancy treated with high intensity focused ultrasound (HIFU), and investigate the safety and feasibility of using HIFU in the treatment of selected patients with renal tumors.

MATERIALS AND METHODS

HIFU treatment was performed in 12 patients with advanced stage renal cell carcinoma and 1 patient with colon cancer metastasized to kidney. Patients were followed after treatment to observe complications and long-term therapeutic efficacy. Complications and changes in symptoms seen at presentation were recorded. Mid stream urine specimens were sent for microscopy and serum creatinine was measured postoperatively. Followup radiological examinations were performed to detect tumor response to the ablation.

RESULTS

A total of 13 patients received HIFU treatment safely, including 10 who had partial ablation and 3 who had complete tumor ablation. After HIFU hematuria disappeared in 7 of 8 patients and flank pain of presumed malignant origin disappeared in 9 of 10 patients. Postoperative images showed decrease in or absence of tumor blood supply in the treated region and significant shrinkage of the ablated tumor. Of the 13 patients 7 died (median survival 14.1 months, range 2 to 27) and 6 were still alive with median followup of 18.5 months (range 10 to 27).

CONCLUSIONS

This preliminary experience suggests that HIFU could be safe and feasible in the treatment of patients with advanced renal malignancy.

Liver hemostasis with high-intensity ultrasound: repair and healing

OBJECTIVE

Previous studies have shown that high-intensity focused ultrasound can effectively control bleeding from injuries of liver, spleen, and blood vessels. This study investigated long-term hemostasis and tissue repair after high-intensity focused ultrasound treatment in liver.

METHODS

A total of 21 rabbits were randomly assigned to 2 groups: high-intensity focused ultrasound treatment (n = 14) and sham treatment (n = 7). All animals had sterile laparotomy and liver exposure. The high-intensity focused ultrasound-treated animals received liver incisions, 20 to 25 mm long and 4 to 6 mm deep, followed immediately by high-intensity focused ultrasound application until complete hemostasis was achieved. After recovery, sonographic images, blood samples, and histologic samples were collected immediately and on days 1, 3, 7, 14, 28, and 60 after treatment.

RESULTS

All 14 liver injuries were hemostatic after an average +/- SD of 78 +/- 44 seconds of high-intensity focused ultrasound application, with no rebleeding at any time point after the treatment. Subsequent blood analysis showed no significant difference in serial hematologic or coagulation measures between the high-intensity focused ultrasound and sham groups. Alanine aminotransferase and aspartate aminotransferase levels increased immediately after surgery by as much as 285% up to day 3 and returned to normal values by day 7. Hematocrit and white blood cell counts showed no statistically significant difference from normal values at all time points. Histologic examination up to 60 days after treatment revealed scarring and liver tissue regeneration at the treatment site.

CONCLUSIONS

High-intensity focused ultrasound appears to provide long-lasting hemostasis of acute liver injury. Healing and repair mechanisms after high-intensity focused ultrasound application appear to be intact.

Extracorporeal focused ultrasound surgery for treatment of human solid carcinomas: early Chinese clinical experience

The objective of this article is to introduce the early Chinese clinical experience of using extracorporeal focused ultrasound (US) surgery (FUS) for the treatment of solid tumors. From December 1997 to October 2001, a total of 1038 patients with solid tumors underwent FUS ablation in 10 Chinese hospitals. The tumors included primary and metastatic liver cancer, malignant bone tumors, breast cancer, soft tissue sarcomas, kidney cancer, pancreatic cancer, abdominal and pelvic malignant tumors, uterine myoma, benign breast tumors, hepatic hemangioma and other solid tumors. In this article, pathologic changes in tumors treated with FUS, real-time diagnostic imaging for targeting, monitoring and assessment of results by follow-up images are presented. Early clinical results and complications of the technique are also reported.

Leiomyosarcoma of the cervix

BACKGROUND

Epithelioid leiomyosarcoma arising from the uterine cervix is extremely rare, with only three cases reported in the world literature. We present the case report of a 14-cm epithelioid leiomyosarcoma arising from the uterine cervix.

CASE

A 47-year-old female presented with a 1-year history of worsening menorrhagia and was found to have a large pelvic mass extending into and filling the upper vagina. She underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy, revealing a 14 x 10 x 9 cm cervical epithelioid leiomyosarcoma.

CONCLUSION

Although exceedingly rare, leiomyosarcoma is able to arise primarily from the uterine cervix. Given its extreme rarity, management of cervical LMS must be extrapolated from the currently accepted management for uterine LMS.

Attenuation of porcine tissues in vivo after high-intensity ultrasound treatment

The attenuation of ultrasound (US) waves in biologic tissues is an important determinant of energy absorption and wave propagation; thus, important in optimization of high-intensity focused US (HIFU) therapy. We measured attenuation of selected porcine tissues (liver, spleen and abdominal wall) in vivo in the frequency range of 1 to 5 MHz, using the pulse-transmission method, before and after HIFU treatment. In all tissues, an increase in attenuation was observed with increasing frequency. The attenuation coefficient was higher in HIFU-treated tissues than in the untreated tissues. The lowest attenuation was measured in the liver, both in normal and HIFU-treated cases. Mechanisms that may be responsible for the observed attenuation coefficient increase in HIFU-treated tissues include thermally induced change in the tissue macromolecular structure and presence of gas/vapor bubbles due to cavitation and/or boiling.

Experimental evaluation of lesion prediction modelling in the presence of cavitation bubbles: Intended for high-intensity focused ultrasound prostate treatment

The accuracy of high-intensity focused ultrasound (HIFU) lesion prediction modelling was evaluated for a truncated spherical transducer designed for prostate cancer treatment The modelling adapted the bio heat transfer equation (BHTE) to take into account the activity of cavitation bubbles generated during HIFU exposure. This modelling was used to predict the lesions produced by three different transducer geometries: fixed-focus, concentric-ring and 1.5D phased-array. Lesions were predicted for different ultrasound exposure conditions close to those used in prostate cancer treatment. Twenty-one in vitro and nine in vitro experiments were performed on pig liver to validate the accuracy of the predictions. A good match was found between the predicted and experimental lesion shapes. Lesion dimensions (maximum depth and length, area at the centre of the lesion or central surface area) were measured on experimental and predicted lesions. The central surface area was predicted by the model with a range of error of 0.15-6.5% for in vitro tests and 0.97-9% in vivo. For comparison, BHTE without bubbles had a range of error of 0.4-55.5% (in vitro) and 9-25.5% (in vivo). The model should be accurate enough to predict HIFU lesions under ultrasound exposure conditions used in prostate cancer treatment.

The emergent role of focal liver ablation techniques in the treatment of primary and secondary liver tumours

Only 20% of patients with primary or secondary liver tumours are suitable for resection because of extrahepatic disease or the anatomical distribution of their disease. These patients could be treated by ablation of the tumour, thus preserving functioning liver. This study presents a detailed review of established and experimental ablation procedures. The relative merits of each technique will be discussed and clinical data regarding the efficacy of the techniques evaluated. A literature search from 1966 to 2003 was undertaken using Medline, Pubmed and Web of Science databases. Keywords were Hepatocellular carcinoma, liver metastases, percutaneous ethanol injection, cryotherapy, microwave coagulation therapy, radiofrequency ablation, interstitial laser photocoagulation, focused high-intensity ultrasound, hot saline injection, electrolysis and acetic acid injection. Ablative techniques offer a promising therapeutic modality to treat unresectable tumours. Large-scale randomised controlled trials are required before widespread acceptance of these techniques can occur.

A microbubble agent improves the therapeutic efficiency of high intensity focused ultrasound: a rabbit kidney study

Eighty kidneys (40 left and 40 right kidneys) of New Zealand rabbits were ablated using high intensity focused ultrasound (HIFU), (14,300 W/cm(2), 1.0 MHz). Kidneys were randomly divided into two groups. HIFU was performed in the manner of linear scan in both groups. Prior to HIFU, normal saline solution and isovolumetric microbubble agent were administrated intravenously in groups I and II, respectively. HIFU was finished in all left kidneys and in 26/40 right ones. The therapeutic efficiency was reflected using necrosis rate (cubic centimeters per second), which was the tissue volume of coagulative necrosis per 1 s HIFU exposure. In both groups, predetermined volumes were damaged without harming overlying tissues. Necrosis rates were increased in group II both in left (0.0089+/-0.0107 vs. 0.0493+/-0.0777, P=0.0323) and in right (0.0039+/-0.0055 vs. 0.0162+/-0.0168, P=0.0248) kidneys. Pathological examinations confirmed that there were no intact tissue focuses within exposed regions in either group. These findings suggested that the microbubble agent improved the therapeutic efficiency of HIFU. Hemorrhage and hyperemia were also detected on the margin of the ablated tissues (both in cortex and medulla) in both groups.

High intensity focused ultrasound: surgery of the future?

For 50 years, high intensity focused ultrasound (HIFU) has been a subject of interest for medical research. HIFU causes selective tissue necrosis in a very well defined volume, at a variable distance from the transducer, through heating or cavitation. Over the past decade, the use of HIFU has been investigated in many clinical settings. This literature review aims to summarize recent advances made in the field. A Medline-based literature search (1965-2002) was conducted using the keywords "HIFU" and "high intensity focused ultrasound". Additional literature was obtained from original papers and published meeting abstracts. The most abundant clinical trial data comes from studies investigating its use in the treatment of prostatic disease, although early research looked at applications in neurosurgery. More recently horizons have been broadened, and the potential of HIFU as a non-invasive surgical tool has been demonstrated in many settings including the treatment of tumours of the liver, kidney, breast, bone, uterus and pancreas, as well as conduction defects in the heart, for surgical haemostasis, and the relief of chronic pain of malignant origin. Further clinical evaluation will follow, but recent technological development suggests that HIFU is likely to play a significant role in future surgical practice.

Changes in biologic characteristics of breast cancer treated with high-intensity focused ultrasound

Proliferation, invasion, immortalization and metastasis are the main malignant characteristics of cancer. Previous studies have shown that high-intensity focused ultrasound (US), or HIFU, can induce irreversible damage both to breast cancer cells and to tumor blood vessels. However, light microscopy alone may not always show this clearly. In this study, molecular biologic techniques were used to examine any changes in molecular markers associated with malignant behavior after exposure to HIFU. A total of 48 women with breast cancer were randomized to a control group (mastectomy) and a HIFU group (HIFU followed by mastectomy). Immunohistochemical staining, messenger RNA (mRNA) in situ hybridization and telomere-repeat amplification protocol-enzyme-linked immunosorbent assay (TRAP-ELISA) techniques were used to detect tumor expression of proliferating cell nuclear antigen (PCNA), cell adhesion molecule CD44v6, matrix metalloproteinase-9 (MMP-9), erbB2 mRNA, and to measure telomerase activity in both groups. The results demonstrated that there were significant alterations in expression of PCNA, CD44v6, MMP-9, erbB2 mRNA, and a dramatic decrease in telomerase activity in the HIFU group. It is concluded that malignant tumor characteristics are arrested by HIFU, and that biologic factors are potential markers for assessing HIFU efficacy.

Treatment of uterine fibroid tumors in an in situ rat model using high-intensity focused ultrasound

OBJECTIVE

To determine the efficacy and safety of high-intensity focused ultrasound (HIFU) for the treatment of uterine fibroid tumors in an in situ animal model.

DESIGN

High-intensity focused ultrasound was applied intraoperatively to uterine fibroid tumors in rats.

SETTING

Department of Bioengineering, and Applied Physics Laboratory, University of Washington, Seattle, Washington.

ANIMAL(S)

Thirty-five tumors in 27 Eker rats that had spontaneous in situ uterine fibroids were randomly assigned into two groups receiving HIFU (n = 29) or sham (n = 6) treatments.

INTERVENTION(S)

Animals were anesthetized, and tumors were exposed surgically. The HIFU was applied at 3.5 MHz in 10-second bursts to produce coagulative necrosis lesions (3 mm by 10 mm), spaced 5 mm apart. Sham treatments consisted of exposing the tumors, and handling them similarly to those in the HIFU treatment group, but HIFU was not applied.

MAIN OUTCOME MEASURE(S)

Tumor volume was measured every week transabdominally using B-mode ultrasound imaging. Gross examination and histological analysis were performed after euthanasia.

RESULT(S)

More than half of the tumors in the HIFU treatment group showed significant tumor volume reduction. The average tumor volume in the sham treatment group increased 40-fold. Gross and histological analysis showed coagulative necrosis of tumor cells in the HIFU treatment group.

CONCLUSION(S)

The HIFU may provide an effective and safe method of treating uterine fibroid tumors.

High-intensity focused US: a potential new treatment for GI bleeding

BACKGROUND

High-intensity focused US has been shown to achieve hemostasis in lacerated large veins and arteries. High-intensity focused US was studied as a potential endoscopic treatment for GI bleeding.

METHODS

A segment of the auricular vein of the rabbit was lacerated longitudinally and then treated with a high-intensity focused US transducer driven at 3.9 MHz (focal intensity of 750 W/cm(2)) in 15 animals until hemostasis was achieved. Sham treatment was delivered to 3 vessels. Rabbits were euthanized on days 0, 2, 7, 14, and 28 to allow for histologic evaluation of the response to treatment.

RESULTS

Hemostasis was achieved in all treated vessels and in none of the sham treatments. Mean treatment time was 13 seconds. Histology initially demonstrated acute thermal injury with subsequent thrombus formation and chronic inflammation leading to replacement of the vessel by fibrous scar tissue.

CONCLUSIONS

High-intensity focused US causes hemostasis in acutely bleeding veins and results in occlusion of treated vessel with subsequent granulation tissue formation.

Tumor growth reduction and DNA transfer by cavitation-enhanced high-intensity focused ultrasound in vivo

The potential application of high-intensity focused ultrasound (US), HIFU, was investigated for nonthermal gene transfer and tumor ablation. Renal carcinoma (RENCA) tumors were implanted on the hind leg of BALB/c mice and injected with a marker plasmid. Optison US contrast agent was also injected into the tumor (IT) or into the venous (IV) circulation. HIFU at 1.55 MHz was applied to the tumors with guidance from diagnostic US images. One test of transfection was also performed with lithotripter shock waves. In one set of exposures, tumor volume was followed for 4 days and a beta-galactosidase marker plasmid was used for localization of transfected cells. A second set of exposures employed a luciferase marker plasmid for assessing overall transfection after 2 days. Use of 100-ms bursts at 8-MPa peak rarefactional pressure amplitude stopped tumor growth during the 4-day period, compared to a 2.8-fold growth in shams and yielded luciferase expression 34-fold greater than in shams. Longer bursts or higher pressure amplitudes led to decreases in tumor growth, but did not yield increases in transfection. The HIFU results were similar to those of shock waves for cavitation enhanced by IT Optison. These results should aid in optimizing the application of HIFU for nonthermal tumor treatment.

Study of a "biological focal region" of high-intensity focused ultrasound

The aim of this study was to explore a law of energy deposition of high-intensity focused ultrasound (HIFU) in various tissues and the expression of such a law. A focused ultrasound (US) tumor therapeutic system was used to apply a focused US beam to tissues both in vivo and in vitro. The formation of individual ellipsoid-shaped regions of coagulative necrosis has been observed. Results showed that the volume of the ellipsoid-shaped coagulative necrosis region was different from that of the acoustic focal region (AFR), both in vitro and in vivo. Acoustic intensities ranging from 7 x 10(3) W/cm(2) to 27.7 x 10(3) W/cm(2) and exposure times from 1 to 20 s gave volumes of ellipsoid-shaped coagulative necrosis of 0.2 to 2000 mm(3). Although the HIFU doses applied were identical, the volumes of individual ellipsoid-shaped coagulative necrotic regions varied with the structures of tissues, their functional status and the irradiation depths. Individual ellipsoid-shaped regions of coagulative necrosis induced by HIFU can be added to produce coagulative necrosis of an entire tumor. We define the individual ellipsoid-shaped coagulative necrosis produced by the US energy deposition of a single exposure as the "biological focal region" (BFR) of HIFU. This serves as the basic unit for HIFU ablation of tumors, and is plotted as a function of AFR, acoustic intensity, exposure time, irradiation depth, the tissue structure and its functional status.

Histologic evolution of high-intensity focused ultrasound in rabbit muscle

RATIONALE AND OBJECTIVES

The purpose of this study was to examine the histologic evolution over time of rabbit skeletal muscle thermally ablated with high-intensity focused ultrasound. The objectives included determining the extent and focality of damage created by this noninvasive, transcutaneous ablative technology.

METHODS

Transcutaneous, thermal ablation with an external focused ultrasound transducer was applied to the paraspinous muscles of 19 rabbits. At varying times, up to 100 days after therapy, single sonications were examined histologically.

RESULTS

Initially, only subtle staining changes were identified within lesions. In the chronic phase (day 51-100), the muscle was replaced or infiltrated by variable amounts of scar and fat similar to degenerative muscle disorders. Histologic changes were limited to the tissue within the intensity focus of the transducer and were not seen in intervening tissues.

DISCUSSION

The current study took a systematic approach to study the long term, in vivo histologic effects of single HIFU lesions in a nonregenerative tissue. This experience in muscle tissue will provide a basis for understanding ultrasound effects for clinical applications such as treatment of uterine fibroids, cardiac tissue, and sarcomas.

Experimental demonstration of noninvasive transskull adaptive focusing based on prior computed tomography scans

Developing minimally invasive brain surgery by high-intensity focused ultrasound beams is of great interest in cancer therapy. However, the skull induces strong aberrations both in phase and amplitude, resulting in a severe degradation of the beam shape. Thus, an efficient brain tumor therapy would require an adaptive focusing, taking into account the effects of the skull. In this paper, we will show that the acoustic properties of the skull can be deduced from high resolution CT scans and used to achieve a noninvasive adaptive focusing. Simulations have been performed with a full 3-D finite differences code, taking into account all the heterogeneities inside the skull. The set of signals to be emitted in order to focus through the skull can thus be computed. The complete adaptive focusing procedure based on prior CT scans has been experimentally validated. This could have promising applications in brain tumor hyperthermia but also in transcranial ultrasonic imaging.

Reversal of adriamycin resistance in ovarian carcinoma cell line by combination of verapamil and low-level ultrasound

In order to determine whether ultrasound, alone or combined with verapamil, could reverse resistance in adriamycin resistant human ovarian carcinoma cell line SKOV(3)/ADR in vitro, cells were subjected to a variable concentration of adriamycin. Verapamil, ultrasound exposure and both of the two were used concurrently or sequentially. Survival rates were decreased in groups in which acoustic irradiation was exerted, or verapamil pretreated and both of which applied. Intracellular adriamycin levels were high where cytotoxicity was enhanced. These results revealed that ultrasound reverse drug resistance in ovarian carcinoma cells, and synergism also existed between verapamil and acoustic exposure if administrated sequentially. These effects were ascribed to increase of intracellular adriamycin accumulation.

Spleen hemostasis using high-intensity ultrasound: survival and healing

BACKGROUND

Previous studies have shown that high-intensity focused ultrasound (HIFU) can effectively control bleeding of incised livers and spleens and punctured vessels. This current study investigated the long-term safety of HIFU in splenic hemostasis.

METHODS

A total of 21 rabbits were randomly assigned to two groups: HIFU treatment (n = 14), and sham treatment (n = 7). All animals underwent sterile laparotomy and splenic exposure. The HIFU-treated animals received splenic incisions, 8 to 10 mm long and 4 to 5 mm deep, and immediate 9.6-MHz HIFU until hemostasis was achieved. After recovery, ultrasound images, blood samples, and histologic samples were collected on days 0, 1, 3, 7, 14, 28, and 60.

RESULTS

All 14 splenic injuries were hemostatic after an average of 96 seconds of HIFU application. There was evidence of rebleeding in one animal between days 3 and 7 posttreatment. Subsequent blood analysis showed no significant difference in serial hematologic or coagulation measures between HIFU and sham groups. Histologic examination up to 60 days posttreatment revealed scarring and spleen tissue regeneration at the treatment site.

CONCLUSION

HIFU provides an effective and safe method of achieving hemostasis after acute splenic injury.

An image-guided high intensity focused ultrasound device for uterine fibroids treatment

A high intensity focused ultrasound (HIFU) device was developed for treating uterine fibroid tumors. This prototype device enables image-guided therapy by aligning a commercially available abdominal ultrasound image probe to a vaginal HIFU transducer so the HIFU focus is in the image plane. The device was designed based on anatomical constraints of the female pelvic structures. HIFU was generated using a 3.5 MHz PZT-8 crystal, 25.4 mm in diameter, bonded to an aluminum lens. Computer simulations were performed to ensure that effective focusing was achievable at a fixed focal depth of 40 mm. Transducer efficiency was empirically determined to be 58%, and the half pressure maximum focal dimensions were 11 mm in length and 1.2 mm in width. A water-filled latex condom surrounding the transducer provided acoustic coupling, a stand-off, and allowed water circulation for transducer cooling. In vitro experiments in a tissue-mimicking gel phantom and in turkey breast demonstrated ultrasound image-guided lesion formation, or tissue necrosis, at the focus due to HIFU induced thermal and cavitation effects. The HIFU treatment site appeared as a hyperechoic spot on the ultrasound image at intensities above 1250 W/cm2. The results of in vitro experiments and in vivo ergonomic testing in six human volunteers indicated that the device has the potential of providing a nonsurgical approach for uterine fibroid treatment. Future in vivo studies in large animal models and fibroids patients are planned.

Treatment of uterine leiomyosarcoma in a xenograft nude mouse model using high-intensity focused ultrasound: a potential treatment modality for recurrent pelvic disease

OBJECTIVE

The objective was to test the efficacy of high-intensity focused ultrasound (HIFU) for treatment of uterine leiomyosarcoma in a Xenograft nude mouse model.

METHODS

A total of 65 athymic nude mice were inoculated subcutaneously with 5 to 7 x 10(6) ELT-5B cells, a uterine leiomyosarcoma cell line derived from the Eker rat. Thirty animals showed tumor growth. The tumor volume was measured transcutaneously once a week. Animals were randomly assigned to three groups: HIFU treatment (n = 17), sham treatment (n = 7), and control (n = 6). A HIFU device, operating at a frequency of 2.0 MHz and an intensity of 2000 W/cm(2), was used for treatment.

RESULTS

Within 3 weeks of a single HIFU treatment, 100% reduction in tumor volume was observed in all animals, except one. A second HIFU treatment was applied to that animal, resulting in 100% reduction in tumor volume. The tumors in the sham-treated animals continued to grow at a similar rate to that of the control group to approximately 500% of the tumor volume at the time of treatment. All animals were monitored for a maximum of 3 months. No metastasis was observed in the HIFU-treated animals. Histological examination confirmed a complete tumor disappearance after HIFU treatment.

CONCLUSION

We have shown that HIFU can effectively treat uterine leiomyosarcoma tumors inoculated in Xenograft nude mice, demonstrating HIFU's potential use for treatment of recurrent uterine leiomyosarcoma.

Thermal ablation therapy for hepatocellular carcinoma

Thermal ablation strategies, including the use of radiofrequency, microwaves, lasers, and high-intensity focused ultrasound, are gaining increasing attention as an alternative to standard surgical therapies in the treatment of primary hepatocellular carcinoma. Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real-time imaging guidance, ability to perform ablative procedures on an outpatient basis, and the potential application in a wider spectrum of patients-including those who are not surgical candidates. In this review, the authors examine the reported clinical success of each of these four therapies, potential complications, current limitations, and future directions of development.

Radiofrequency ablation of hepatic tumors

Radiofrequency thermal ablation is receiving increasing attention as an alternative to standard surgical therapies for the treatment of liver neoplasms. Benefits over surgical resection include the anticipated reduction in morbidity and mortality, low cost, suitability for real time image guidance, the ability to perform ablative procedures on outpatients, and the potential application in a wider spectrum of patients, including nonsurgical candidates. This review examines reported clinical results of this new therapeutic technique, potential complications, current limitations, thermal ablation mechanisms, as well as technical features and diagnostic modalities used in the procedure.

Tumor vessel destruction resulting from high-intensity focused ultrasound in patients with solid malignancies

The purpose of this study was to explore the sequential imaging and histologic alterations of tumor blood vessels in the patient with solid malignancies after extracorporeal treatment of high-intensity focused ultrasound (HIFU). A total of 164 patients underwent extracorporeal HIFU ablation of malignant solid tumors. After HIFU treatment, enhanced magnetic resonance imaging (MRI), color Doppler ultrasound (US) imaging, dynamic radionuclide scanning, digital subtraction angiography, and histologic study were performed to monitor the response of tumor vessels to HIFU ablation. Compared with tumor images in the patients before HIFU, clinical images showed an abrupt interruption, followed by the cessation of blood flow within the tumor vessels after HIFU treatment. The histologic examination indicated that not only the treated tumor cells showed coagulative necrosis, but also small tumor vessels were severely damaged by the HIFU treatment. The results strongly imply that the damaged tumor vessels might play a critical role in secondary tumor cell death, and then indirectly strengthen the destructive force of focused US beams on tumor tissue. It is concluded that tumor vessel damage can be induced by HIFU, which may be a promising strategy in the treatment of patients with solid malignancies.