Clinical improvement and shrinkage of uterine fibroids after thermal ablation by magnetic resonance-guided focused ultrasound surgery

Heart ablation using a planar rectangular high intensity ultrasound transducer and MRI guidance

The aim of this study was to evaluate a flat rectangular (3×10mm(2)) MRI compatible transducer operating at 5MHz. The main task was to explore the feasibility of creating deep lesions in heart at a depth of at least 15mm. The size of thermal necrosis in heart tissue was estimated as a function of power and time using a simulation model. The system was then tested in an excised lamb heart. In this study, we were able to create lesions of 15mm deep with acoustic power of 6W for an exposure of approximately 1min. The contrast to noise ratio (CNR) between lesion and heart tissue was evaluated using fast spin echo (FSE). The CNR value was approximately 22 using T1W FSE. Maximum CNR was achieved with repetition time (TR) between 300 and 800ms. Using T2W FSE, the corresponding CNR was approximately 13 for the 14 in vivo experiments. The average lesion depth was 11.93mm with a standard deviation of 0.62mm. In vivo irradiation conditions were 6W for 60s. The size of the lesion in the other two dimensions was close to 3×10mm(2) (size of the transducer element).

Numerical prediction of frequency dependent 3D maps of mechanical index thresholds in ultrasonic brain therapy

PURPOSE

Therapeutic ultrasound has been used in the brain for thrombolysis and high intensity focused ultrasound (HIFU) therapy. A low-frequency clinical study of sonothrombolysis, called the transcranial low-frequency ultrasound-mediated thrombolysis in brain ischemia (TRUMBI), has revealed an increased incidence of hemorrhage, which may have been caused by cavitation. The goal of this study is to determine if there is a comparable risk of generating cavitation during HIFU brain therapy at different frequencies.

METHODS

Two approaches are used to transmit acoustic energy through the skull to the brain: low-frequency ultrasound, with a wavelength that is larger than the skull thickness, and high frequency ultrasound, that is sensitive to aberrations and must use corrective techniques. At high frequency, the mechanical index (MI) is lower, which translates to a higher cavitation threshold. In addition to the nonfocused geometry of the 300 kHz sonothrombolysis treatment device, two types of focused therapeutic transducers were modeled: a low frequency 220 kHz transducer and a 1 MHz transducer that required aberration correction with a time-reversal approach, representing the lowest and highest frequencies currently used. The acoustic field was modeled with a finite difference fullwave acoustic code developed for large scale computations, that is, capable of simulating the entire brain volume. Various MI thresholds and device geometries were considered to determine the regions of the brain that have an increased probability of cavitation events.

RESULTS

For an equivalent energy deposition rate, it is shown that at a low frequency there is a significant volume of the brain that is above the MI thresholds. At a high frequency, the volume is over 3 orders of magnitude smaller, and it is entirely confined to a compact focal spot.

CONCLUSIONS

The significant frequency dependence of the volumes with an increased probability of cavitation can be attributed to two factors: First, the volume encompassed by the focal region depends on the cube of the frequency. Second, the heat deposition increases with frequency. In conclusion, according to these simulations, the acoustic environment during HIFU brain therapy at 1 MHz is not conducive to a high probability of cavitation in extended regions of the brain.

MR-guided focused ultrasound for the treatment of uterine fibroids

Magnetic resonance imaging-guided focused ultrasound (MRgFUS) ablation of uterine fibroids provides a minimally invasive outpatient technique for targeting and treating symptomatic uterine fibroids. Magnetic resonance imaging provides a guidance platform that has high temporal and spatial resolution for guiding, as well as thermal monitoring of the procedure. The high-intensity focused ultrasound provides a mechanism for delivering large amounts of energy directly into the fibroid without causing detrimental effects to the nontarget tissues. Early and intermediate follow-up of patients treated with MRgFUS provided promising results on the efficacy of the technique for providing symptom relief to patients. As more long-term follow-up data are published, the efficacy of this technique can be compared to more invasive surgical and minimally invasive catheter treatments.

Safety limitations of MR-HIFU treatment near interfaces: a phantom validation

Magnetic resonance‐guided high‐intensity focused ultrasound (MR‐HIFU) is a noninvasive image‐guided technique used to thermally ablate solid tumors. During treatment, ultrasound reflections from distal media interfaces can shift prescribed treatment locations. The purpose of this study was to investigate the effect of normal incidence reflections from air, acrylic (modeling bone), and rubber on treatment location, temperature elevation, and heating patterns by performing ultrasound exposures in a tissue‐mimicking phantom and in ex vivo porcine tissue using a clinical MR‐HIFU platform. The results demonstrated a shift in treatment location toward the distal interface when targeted closer than 2 cm from the interface, especially for acrylic. Our study demonstrated that the ultrasound wave reflections from a distal air interface had less effect than the acrylic interface (modeling bone) on the heating pattern and focal location. This study provides useful information to better understand the limitations and safety concerns of performing MR‐HIFU treatments with commercial clinical equipment.

PACS numbers: 87.61.‐c, 87.63.D

MRgFUS treatment of uterine fibroid in a nulliparous woman with acute retention of urine

Uterine fibroids are the most common tumors of the female reproductive tract. Although most fibroids are asymptomatic, about 25% are associated with symptoms that can have a significant impact on patient's quality of life, including prolonged or excessive menstrual bleeding, pelvic pain or bulkiness, dyspareunia, increased urinary frequency, and infertility. Various treatment options available for symptomatic uterine fibroids include hysterectomy, myomectomy (abdominal or laparoscopic), uterine artery embolization, MR-guided Focused Ultrasound (MRgFUS), and hormonal therapy, which also is sometimes used as adjuvant to other therapies. MRgFUS is a non-invasive treatment approach for symptomatic uterine fibroids. The following case report demonstrates successful treatment of a fibroid that is hyper-intense on T2WIs by MRgFUS with immediate alleviation of pressure symptoms on the urinary bladder.

Targeted vessel ablation for more efficient magnetic resonance-guided high-intensity focused ultrasound ablation of uterine fibroids

Purpose

To report the first clinical experience with targeted vessel ablation during magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) treatment of symptomatic uterine fibroids.

Methods

Pretreatment T1-weighted contrast-enhanced magnetic resonance angiography was used to create a detailed map of the uterine arteries and feeding branches to the fibroids. A three-dimensional overlay of the magnetic resonance angiography images was registered on 3D T2-weighted pretreatment imaging data. Treatment was focused primarily on locations where supplying vessels entered the fibroid. Patients were followed 6 months after treatment with a questionnaire to assess symptoms and quality of life (Uterine Fibroid Symptom and Quality of Life) and magnetic resonance imaging to quantify shrinkage of fibroid volumes.

Results

In two patients, three fibroids were treated with targeted vessel ablation during MR-HIFU. The treatments resulted in almost total fibroid devascularization with nonperfused volume to total fibroid volume ratios of 84, 68, and 86%, respectively, of treated fibroids. The predicted ablated volumes during MR-HIFU in patients 1 and 2 were 45, 40, and 82 ml, respectively, while the nonperfused volumes determined immediately after treatment were 195, 92, and 190 ml respectively, which is 4.3 (patient 1) and 2.3 (patient 2) times higher than expected based on the thermal dose distribution. Fibroid-related symptoms reduced after treatment, and quality of life improved. Fibroid volume reduction ranged 31–59% at 6 months after treatment.

Conclusion

Targeted vessel ablation during MR-HIFU allowed nearly complete fibroid ablation in both patients. This technique may enhance the use of MR-HIFU for fibroid treatment in clinical practice.

Clinical and future applications of high intensity focused ultrasound in cancer

High intensity focused ultrasound (HIFU) or focused ultrasound (FUS) is a promising modality to treat tumors in a complete, non invasive fashion where online image guidance and therapy control can be achieved by magnetic resonance imaging (MRI) or diagnostic ultrasound (US). In the last 10 years, the feasibility and the safety of HIFU have been tested in a growing number of clinical studies on several benign and malignant tumors of the prostate, breast, uterine, liver, kidney, pancreas, bone, and brain. For certain indications this new treatment principle is on its verge to become a serious alternative or adjunct to the standard treatment options of surgery, radiotherapy, gene therapy and chemotherapy in oncology. In addition to the now clinically available thermal ablation, in the future, focused ultrasound at much lower intensities may have the potential to become a major instrument to mediate drug and gene delivery for localized cancer treatment. We introduce the technology of MRI guided and ultrasound guided HIFU and present a critical overview of the clinical applications and results along with a discussion of future HIFU developments.

Comparing focused ultrasound and uterine artery embolization for uterine fibroids-rationale and design of the Fibroid Interventions: reducing symptoms today and tomorrow (FIRSTT) trial

OBJECTIVE

To present the rationale, design, and methodology of the Fibroid Interventions: Reducing Symptoms Today and Tomorrow (FIRSTT) study.

DESIGN

Randomized clinical trial.

SETTING

Two academic medical centers.

PATIENT(S)

Premenopausal women with symptomatic uterine fibroids.

INTERVENTION(S)

Participants are randomized to two U.S. Food and Drug Administration-approved minimally invasive treatments for uterine leiomyomas: uterine artery embolization and magnetic resonance-guided focused ultrasound.

MAIN OUTCOME MEASURE(S)

The primary endpoint is defined as the need for an additional intervention for fibroid symptoms following treatment. Secondary outcomes consist of group differences in symptom alleviation, recovery trajectory, health-related quality of life, impairment of ovarian reserve, treatment complications, and the economic impact of these issues.

RESULT(S)

The trial is currently in the phase of active recruitment.

CONCLUSION(S)

This randomized clinical trial will provide important evidence-based information for patients and health care providers regarding optimal minimally invasive treatment approach for women with symptomatic uterine leiomyomas.

CLINICAL TRIAL REGISTRATION

NCT00995878.

Magnetic resonance-guided focused ultrasound for uterine fibroids

Uterine fibroids are an important problem for women of reproductive age. Although hysterectomy has been the traditional treatment for fibroids, many women are interested in a less invasive therapy. Magnetic resonance-guided focused ultrasound (MRgFUS) is a new technique for treating a variety of solid tumors. It has been tested and approved by the U.S. Food & Drug Administration (FDA) for the treatment of uterine fibroids. The procedure is completely noninvasive. It is performed as an outpatient procedure and the patient can resume her normal activities the day following the procedure. Techniques of treatment of uterine fibroids are still being refined, but significant progress has been made in understanding some of the challenges for this new technology. Some fibroids are more responsive to the focused ultrasound; some fibroids are more resistant. Not all women are candidates for this procedure. Absolute contraindications include bowel that is in the path of the ultrasound beam, or surgical scars in the beam pathway. The procedure of MRgFUS is feasible, safe and becoming increasingly popular. Questions still remain particularly the use of this technique for patients desiring fertility, and what will be the long-term results.

Magnetic resonance-guided focused ultrasound surgery for leiomyoma-associated infertility

OBJECTIVE

To describe magnetic resonance-guided focused ultrasound surgery (FUS) as a treatment for a case of leiomyoma-associated infertility.

DESIGN

Case report from a randomized clinical trial.

SETTING

Academic medical center.

PATIENT(S)

A 37-year-old woman with known leiomyomas and a history of 18 months of home-inseminations from a known donor.

INTERVENTION(S)

Magnetic resonance-guided FUS treatment of uterine fibroids, where the dominant fibroid distorted the uterine cavity.

MAIN OUTCOME MEASURE(S)

Pregnancy.

RESULT(S)

A viable intrauterine pregnancy, with a full-term vaginal delivery, was conceived after a single clomiphene citrate and intrauterine insemination cycle.

CONCLUSION(S)

The role of FUS for enhancement of fertility in women with nonhysteroscopically resectable uterine fibroids distorting the uterine cavity should be investigated further.

ExAblate magnetic resonance-guided focused ultrasound system in multiple body applications

Focused ultrasound surgery (FUS) is a completely noninvasive method of thermally destroying a target tissue while sparing adjacent tissues and organs. Treatment is relatively painless and can be carried out under conscious sedation on an out-patient basis. The combination of magnetic resonance guidance with FUS (MRgFUS) provides the ability to plan and monitor treatments in near real-time, further increasing the safety profile of MRgFUS. This technology provides a very personalized treatment, adjusted to the individual patient anatomy, pathology and treatment response, hence it meets the needs of patients, as well as of physicians. MRgFUS has been used extensively in the successful treatment of uterine fibroids, and has been shown to be an effective treatment in the breast and in bone metastases in smaller scale studies. It shows great potential in the treatment of prostate and liver tumors, as well as in the brain and facet joints.

High frame rate ultrasound monitoring of high intensity focused ultrasound-induced temperature changes: a novel asynchronous approach

PURPOSE

When applying diagnostic ultrasound to guide focused ultrasound (FUS) thermal therapy, high frame rate ultrasonic temperature monitoring is valuable in better treatment control and dose monitoring. However, one of the potential problems encountered when performing ultrasonic temperature monitoring of a FUS procedure is interference between the FUS and imaging systems. Potential means of overcoming this problem include the switch between the FUS system and the imaging system (limited by a reduced frame rate of thermal imaging) or the development of complex synchronization protocols between the FUS therapeutic system and the ultrasonic imaging apparatus (limited by implementation efforts both for software and hardware designs, and low potential for widespread diffusion). In this paper, we apply an asynchronous idea to retrieving high frame rate and FUS-interference-free thermal imaging during FUS thermal therapy.

METHODS

Tone-burst delivery mode of the FUS energy is employed in our method, and the imaging and FUS systems are purposely operated in an asynchronous manner. Such asynchronous operation causes FUS interference to saturate sequential image frames at different A-lines; thus clean A-lines from several image frames can be extracted by a total energy-thresholding technique and then combined to reconstruct interference-free B-mode images at a high frame rate for temperature estimation. The performance of the proposed method is demonstrated by phantom experiments. Relationships of the FUS duty-cycle with the maximum reconstructed frame rate of thermal imaging and the corresponding maximum temperature increase are also studied. Its performance was also evaluated and compared with the existing manually synchronous and synchronous approaches.

RESULTS

By proper selection of the FUS duty-cycle, using our method, the frame rate of thermal imaging can be increased up to tenfold compared with that provided by the manually synchronous approach. Our method is capable of pushing the frame rate of thermal images to the same order as that of the synchronous approach while avoiding sacrificing the observable field of view (FOV) of temperature mapping.

CONCLUSIONS

The asynchronous method can be easily implemented and allows thermal imaging at an improved frame rate, without the need for complex synchronization protocols between the FUS therapeutic system and the ultrasonic imaging apparatus and without sacrifice of observable FOV. This technology may provide an effective alternative for real-time temperature measuring during thermal ablation procedures and can be easily integrated into current high intensity focused ultrasound systems.

Inhibition of glioma growth by microbubble activation in a subcutaneous model using low duty cycle ultrasound without significant heating

OBJECT

In this study, the authors sought determine whether microbubble (MB) destruction with pulsed low duty cycle ultrasound can be used to reduce brain tumor perfusion and growth through nonthermal microvascular ablation.

METHODS

Studies using C57BLJ6/Rag-1 mice inoculated subcutaneously with C6 glioma cells were approved by the institutional animal care and use committee. Microbubbles were injected intravenously, and 1 MHz ultrasound was applied with varying duty cycles to the tumor every 5 seconds for 60 minutes. During treatment, tumor heating was quantified. Following treatment, tumor growth, hemodynamics, necrosis, and apoptosis were measured.

RESULTS

Tumor blood flow was significantly reduced immediately after treatment, with posttreatment flow ranging from 36% (0.00002 duty cycle) to 4% (0.01 duty cycle) of pretreatment flow. Seven days after treatment, tumor necrosis and apoptosis were significantly increased in all treatment groups, while treatment with ultrasound duty cycles of 0.005 and 0.01 inhibited tumor growth by 63% and 75%, respectively, compared with untreated tumors. While a modest duty cycle-dependent increase in intratumor temperature was observed, it is unlikely that thermal tissue ablation occurred.

CONCLUSIONS

In a subcutaneous C6 glioma model, MB destruction with low-duty cycle 1-MHz ultrasound can be used to markedly inhibit growth, without substantial tumor tissue heating. These results may have a bearing on the development of transcranial high-intensity focused ultrasound treatments for brain tumors that are not amenable to thermal ablation.

A unified approach to combine temperature estimation and elastography for thermal lesion determination in focused ultrasound thermal therapy

Sonogram-based temperature estimation and elastography have both shown promise as methods of monitoring focused ultrasound (FUS) treatments to induce thermal ablation in tissue. However, each method has important limitations. Temperature estimates based on echo delays become invalid when the relationship between sound speed and temperature is nonlinear, and are further complicated by thermal expansion and other changes in tissue. Elastography can track thermal lesion formation over a wider range of elasticity, but with low specificity and high noise. Furthermore, this method is poor at small lesion detection. This study proposes integrating the two estimates to improve the quality of monitoring FUS-induced thermal lesions. Our unified computational kernel is tested on three types of phantoms. Experiments with type I and type II phantoms were conducted to calibrate the thermal mapping and elastography methods, respectively. The optimal settings were then used in experiments with the type III phantom, which contains ex vivo swine liver tissue. Three different spatial-peak temporal-average intensities (I(spta); 35, 133 and 240 W cm(-2)) were delivered with a sonication time of 60 s. The new procedure can closely monitor heating while identifying the dimensions of the thermal lesion, and is significantly better at the latter task than either approach alone. This work may help improve the current clinical practice, which employs sonograms to guide the FUS-induced thermal ablation procedure.

An in vitro study of a phase-shift nanoemulsion: a potential nucleation agent for bubble-enhanced HIFU tumor ablation

Phase-shift nanoemulsions have the potential to nucleate bubbles and enhance high-intensity focused ultrasound (HIFU) cancer therapy. This emulsion consists of albumin-coated dodecafluoropentane (DDFP) droplets with a mean diameter of approximately 260 nm at 37°C. It is known that superheated perfluorocarbon droplets can be vaporized with microsecond long ultrasound pulses if the acoustic pressure exceeds a specific threshold. In addition, it is well documented that particles smaller than 400 nm can extravasate through leaky tumor vessels and accumulate in the tumor interstitial space. Thus, nanoemulsions may passively target solid tumors, thus localizing cavitation nuclei for bubble-enhanced HIFU-mediated heating. In this study, we investigate the acoustic droplet vaporization of a DDFP nanoemulsion in tissue-mimicking gels and demonstrate the ability to nucleate inertial cavitation (IC) and enhance HIFU-mediated heating. The nanoemulsion was dispersed throughout albumin-acrylamide gel phantoms and sonicated with microsecond-length HIFU pulses (f = 2 MHz). The pressure threshold needed to vaporize the nanoemulsion was measured as a function of degree of superheat, pulse length and nanoemulsion concentration. It was determined that the vaporization threshold was inversely proportional with degree of superheat and independent of pulse length and concentration within the range of values tested. It was also shown that the bubbles formed from vaporized nanoemulsions reduced the IC threshold in the gel phantoms. Finally, it was demonstrated that cavitation from vaporized nanoemulsions accelerated HIFU-mediated heating. The results from this study demonstrate that phase-shift nanoemulsions can be combined with HIFU to provide a high degree of spatial and temporal control of bubble-enhanced heating.

High-intensity focused ultrasound ablation of uterine localized adenomyosis

PURPOSE OF REVIEW

To introduce recent developments in a noninvasive treatment of using high-intensity focused ultrasound (HIFU) for ablating uterine localized adenomyosis, and to discuss their potential in this application.

RECENT FINDINGS

This literature roughly reviewed conservative therapy for uterine localized adenomyosis and emphasized using HIFU for ablating it. The main histological change of HIFU treatment was the coagulative necrosis of adenomyosis cells, with damage on small blood vessels of adenomyoma. MR-guided focused ultrasound surgery (MRgFUS) and ultrasound-guided HIFU ablation of focal adenomyosis were with satisfactory results. MRgFUS was less invasive and safely ablated adenomyosis tissue close to the endometrium or to serosal surface. HIFU might be safe and effective for treating patients with adenomyosis, and the acoustic intensity was a key factor for therapeutic efficacy as the severity of symptoms might correlate with lesion extent in some patients. At a given therapeutic dose, the influence of acoustic intensity on focal temperature rise was greater than that of exposure time. Some other experiments showed that the size of adenomyoma was increased 3-4 months after HIFU treatment. The reasons were related to the size of tumor, treatment parameters, operation procedure, and the blood supply of the targeted tissue. Although recent results have been very encouraging, further trials are essential to evaluate the long-term efficacy, and cost-effectiveness of HIFU ablation in localized adenomyosis.

SUMMARY

Compared with current conservative treatments, HIFU may be a noninvasive approach and may offer complete ablation of adenomyoma, with less trauma, less complication, and low cost and short hospital stay for treating patients with uterine localized adenomyosis.

Contrast-Enhanced Dynamic MR Imaging of Uterine Fibroids as a Potential Predictor of Patient Eligibility for MR Guided Focused Ultrasound (MRgFUS) Treatment for Symptomatic Uterine Fibroids

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is a non-invasive treatment approach for symptomatic uterine fibroids. One imaging characteristic considered in selecting patients who may benefit from MRgFUS of their uterine fibroids is the signal intensity of the fibroid compared with surrounding myometrium on T2-weighted MR images. Previous reports suggest that hyper-intense fibroids are less amenable to MRgFUS compared with iso- or hypo-intense fibroids. In this case study, we utilized contrast-enhanced dynamic MR imaging to further characterize the vascularity of a hyper-intense fibroid. Based on the results of dynamic T1-weighted contrast-enhanced images, we assumed that the hyper-intense appearance resulted from high fluid content rather than high vascularity and predicted that the fibroid would respond to MRgFUS. The patient underwent the MRgFUS without complication and reported significant decrease in fibroid symptoms at 3 and 12 months post-treatment. This case suggests that pre-treatment dynamic contrast-enhanced imaging used in conjunction with T2-weighted imaging may improve the criteria for selecting uterine fibroids amenable to treatment with MRgFUS, potentially leading to improved patient outcomes.

Characteristics indicating adenomyosis coexisting with leiomyomas: a case-control study

BACKGROUND

Adenomyosis is rarely diagnosed before hysterectomy and commonly coexists with uterine leiomyomas. The objective of this study was to identify distinct features of a concurrent diagnosis of adenomyosis in women with uterine leiomyomas.

METHODS

We conducted a case-control study of women undergoing hysterectomy with a histologic diagnosis of both adenomyosis and leiomyomas and women with uterine leiomyomas but no adenomyosis. A retrospective medical record review of hospital and ambulatory records was performed to ascertain sociodemographic and anthropometric variables, as well as to confirm intraoperative and pathologic findings.

RESULTS

Our study sample comprised 255 patients, 85 women with adenomyosis and leiomyomas and 170 women with only leiomyomas. In multivariable logistic regression analyses, women with adenomyosis and leiomyomas were more likely to have more pelvic pain [odds ratio (OR) 3.4, 95% confidence interval (CI) 1.8-6.4], have less fibroid burden (OR per doubling in fibroid size 0.6, 95% CI 0.5-0.8), were more likely to be parous (OR 3.8, 95% CI 1.4-10.5) and have lower body mass index (OR per 5 unit increase in BMI 0.8, 95% CI 0.6-1.0) when compared with women with leiomyomas alone.

CONCLUSIONS

Women undergoing hysterectomy with both adenomyosis and leiomyomas have a number of different clinical features compared with women with only leiomyomas at the time of hysterectomy. Women with substantial pain despite a smaller fibroid burden may be more likely to have concomitant adenomyosis.

Safety and efficacy of high intensity focused ultrasound ablation therapy for adenomyosis

RATIONALE AND OBJECTIVES

In patients with adenomyosis, the severity of symptoms correlates roughly with the extent of adenomyosis. Thus, it was hypothesized that the ablation of enough volume of adenomyosis might alleviate symptoms. The aim of this study was to investigate the safety and efficacy of high-intensity focused ultrasound (HIFU) ablation for the treatment of adenomyosis.

MATERIALS AND METHODS

Phase I HIFU ablation of adenomyosis was performed on 12 patients. Three patients each were treated using four different acoustic intensities (290, 340, 380, and 420 W) step by step. Contrast-enhanced ultrasound was used to evaluate the necrotic region of treated adenomyosis. The efficacy of therapy was evaluated after 3 months of follow-up.

RESULTS

All patients in the four groups tolerated the therapy well, and no severe complications were found during follow-up. After treatment, nonenhanced necrotic regions were shown on contrast-enhanced ultrasound in all treated adenomyosis. The mean volumes of the nonenhanced regions were 72, 75, 68, and 124 cm(3) in the 290-W, 340-W, 380-W, and 420-W groups, respectively. At 3 months after therapy, the mean pain relief in the four groups was 25%, 58.3%, 66.7%, and 83.3%, respectively.

CONCLUSIONS

HIFU may be a safe and effective method to treat adenomyosis, and an acoustic intensity of 420 W may be able to produce larger volumes of necrosis and better pain relief.

Magnetic resonance-guided focused ultrasound (MRgFUS) compared with abdominal hysterectomy for treatment of uterine leiomyomas

OBJECTIVES

To compare women undergoing magnetic resonance-guided focused ultrasound (MRgFUS) to a group of contemporaneously recruited women undergoing total abdominal hysterectomy. Patient demographics, safety parameters, quality of life outcomes and disability measures are reported.

METHODS

One hundred and nine women were recruited in seven centers for MRgFUS treatment and 83 women who underwent abdominal hysterectomy were recruited in seven separate centers to provide contemporaneous assessment of safety. The adverse-event profile and disability parameters were prospectively assessed. Patients were also screened at baseline and at 1, 3 and 6 months using the SF-36 health survey questionnaire.

RESULTS

There were no life-threatening adverse events in either group. Overall, the number of significant clinical complications and adverse events was lower in women in the MRgFUS group compared to women undergoing hysterectomy. MRgFUS was associated with significantly faster recovery, including resumption of usual activities. At 6 months of follow-up, there were four (4%) treatment failures in the MRgFUS arm. Regarding SF-36 subscale scores, at 6 months there was improvement in all SF-36 subscales for both treatment groups. However, most of the SF-36 subscale scores were significantly better at this stage in the hysterectomy group than in the MRgFUS group. Women undergoing MRgFUS had steady improvement in all parameters throughout the 6-month follow-up period, despite the fact that they continued to have myomatous uteri and menstruation, which at baseline had given them significant symptomatology.

CONCLUSIONS

The results of this study show that MRgFUS treatment of uterine leiomyomas leads to clinical improvement with fewer significant clinical complications and adverse events compared to hysterectomy at 6 months' follow-up.

Clinical outcomes of magnetic resonance-guided focused ultrasound surgery for uterine myomas: 24-month follow-up

OBJECTIVES

To assess the volume reduction ratio, symptom improvement and reintervention rate following magnetic resonance-guided focused ultrasound surgery (MRgFUS) for uterine myomas.

METHODS

A total of 91 Japanese women with symptomatic myomas underwent MRgFUS between June 2004 and June 2008 using the ExAblate 2000 system. The volume change ratio was calculated at 6, 12 and 24 months following MRgFUS based on T2-weighted magnetic resonance images. The symptom severity score (SSS) was examined before and after the treatment (at 3, 6, 12 and 24 months). Additional post-MRgFUS treatments, such as hysterectomy, myomectomy, uterine artery embolization or repeat MRgFUS, were recorded and the reinterventional treatment rates were compared according to the signal intensity of pretreatment T2-weighted magnetic resonance images of the myomas.

RESULTS

The mean volume change ratios of low- and intermediate-intensity (Type 1/2) myomas were -36.5% 6 months post-procedure and -39.5% 24 months post-procedure. The mean +/- SD SSS value for patients with Type 1/2 myomas before MRgFUS was 35.1 +/- 21.0, and the values diminished significantly during the 24-month follow-up period to a mean value of around 15.0. High-intensity (Type 3) myomas were not observed to have decreased in size 6 months after MRgFUS. Of the 45 Type 1/2 myoma patients with complete follow-up, seven required reinterventional treatment within 24 months. The reintervention rates were 14.0% for Type 1/2 patients and 21.6% for Type 3 patients at 24 months post-treatment.

CONCLUSIONS

Moderate volume reductions of Type 1/2 myomas were noted following MRgFUS, and the reduction in SSS values and the relatively low reintervention rates observed are encouraging. We found MRgFUS to be an appropriate treatment method for Type 1/2 uterine myomas.

Reduction by 98% in uterine myoma volume associated with significant symptom relief after peripheral treatment with magnetic resonance imaging-guided focused ultrasound surgery

Magnetic resonance imaging-guided focused ultrasound surgery is a noninvasive treatment for symptomatic uterine myomas. Previous studies have demonstrated a correlation between the treated volume of the myoma, improvement in symptoms, and lesion shrinkage. We report a case in which MRgFUS treatment only at the periphery of the myoma resulted in a 98% reduction in tumor volume at 8 months posttreatment, and at 12-month follow-up, only a small lesion was visible at magnetic resonance imaging. The patient's symptoms, as assessed using the Uterine Fibroids Symptom and Quality of life (UFS-QOL) questionnaire, were substantially improved at both 6 and 12 months posttreatment. We also provide a hypothesis to explain this dramatic reduction in myoma volume after only partial MRgFUS treatment of the lesion.

Instantaneous frequency-based ultrasonic temperature estimation during focused ultrasound thermal therapy

Focused ultrasound thermal therapy relies on temperature monitoring for treatment guidance and assurance of targeting and dose control. One potential approach is to monitor temperature change through ultrasonic-backscattered signal processing. The current approach involves the detection of echo time-shifts based on cross-correlation processing from segmented radiofrequency (RF) data. In this study, we propose a novel ultrasonic temperature-measurement approach that detects changes in instantaneous frequency along the imaging beam direction. Focused ultrasound was used as the heating source, and the 1-D beamformed RF signals provided from an ultrasound imager were used to verify the proposed algorithm for temperature change estimation. For comparison, a conventional cross-correlation technique was also evaluated. Heating experiments testing tissue-mimicking phantoms and ex vivo porcine muscles were conducted. The results showed that temperature can be well estimated by the proposed algorithm in the temperature range, where the relationship of sound speed versus temperature is linear. Compared with the cross-correlation-based algorithm, the proposed new algorithm yields a six-fold increase in computational efficiency, along with comparable contrast-detection ability and precision. This new algorithm may serve as an alternative method for implementing temperature estimation into a clinical ultrasound imager for thermal therapy guidance.

Ultrasonic therapy for gynecologic tumors

Clinical and potential applications of ultrasonic therapy for gynecologic tumors are overviewed in this minireview. As a noninvasive technique, extracorporeal high-intensity focused ultrasound was clinically used to treat uterine myomas. High-intensity focused ultrasound treats leiomyomas via shrinkage of tumor size, reduction of blood supply, and suppression of cell proliferation, resulting in a relief of symptoms and improvement of quality of life. Preclinical trials have confirmed that ultrasound enhanced a cytotoxic agent against cancers of ovary and cervix; insonation overcomes doxorubicin (adriamycin) and cisplatin resistance in ovarian cancers, suggesting a modality for refractory lesions; ultrasonic hyperthermia induces high temperature increase in deeper cancer tissues thus being a potential modality for treatment of cervical cancers. Transvaginal ultrasonic therapy can be applied for a lesion near the cervix. In summary, ultrasonic therapy is a promising treatment modality for gynecologic tumors, and might change clinical practices.

Short-duration-focused ultrasound stimulation of Hsp70 expression in vivo

The development of transgenic reporter mice and advances in in vivo optical imaging have created unique opportunities to assess and analyze biological responses to thermal therapy directly in living tissues. Reporter mice incorporating the regulatory regions from the genes encoding the 70 kDa heat-shock proteins (Hsp70) and firefly luciferase (luc) as reporter genes can be used to non-invasively reveal gene activation in living tissues in response to thermal stress. High-intensity-focused ultrasound (HIFU) can deliver measured doses of acoustic energy to highly localized regions of tissue at intensities that are sufficient to stimulate Hsp70 expression. We report activation of Hsp70-luc expression using 1 s duration HIFU heating to stimulate gene expression in the skin of the transgenic reporter mouse. Hsp70 expression was tracked for 96 h following the application of 1.5 MHz continuous-wave ultrasound with spatial peak intensities ranging from 53 W cm(-2) up to 352 W cm(-2). The results indicated that peak Hsp70 expression is observed 6-48 h post-heating, with significant activity remaining at 96 h. Exposure durations were simulated using a finite-element model, and the predicted temperatures were found to be consistent with the observed Hsp70 expression patterns. Histological evaluation revealed that the thermal damage starts at the stratum corneum and extends deeper with increasing intensity. These results indicated that short-duration HIFU may be useful for inducing heat-shock expression, and that the period between treatments needs to be greater than 96 h due to the protective properties of Hsp70.