Application of high intensity focused ultrasound combined with nanomaterials in anti-tumor therapy

High intensity focused ultrasound (HIFU) has demonstrated its safety, efficacy and noninvasiveness in the ablation of solid tumor. However, its further application is limited by its inherent deficiencies, such as postoperative recurrence caused by incomplete ablation and excessive intensity affecting surrounding healthy tissues. Recent research has indicated that the integration of nanomaterials with HIFU exhibits a promising synergistic effect in tumor ablation. The concurrent utilization of nanomaterials with HIFU can help overcome the limitations of HIFU by improving targeting and ablation efficiency, expanding operation area, increasing operation accuracy, enhancing stability and bio-safety during the process. It also provides a platform for multi-therapy and multi-mode imaging guidance. The present review comprehensively expounds upon the synergistic mechanism between nanomaterials and HIFU, summarizes the research progress of nanomaterials as cavitation nuclei and drug carriers in combination with HIFU for tumor ablation. Furthermore, this review highlights the potential for further exploration in the development of novel nanomaterials that enhance the synergistic effect with HIFU on tumor ablation.

An augmented hybrid multibaseline and referenceless MR thermometry motion compensation algorithm for MRgHIFU hyperthermia

PURPOSE

A hybrid principal component analysis and projection onto dipole fields (PCA-PDF) MR thermometry motion compensation algorithm was optimized with atlas image augmentation and validated.

METHODS

Experiments were conducted on a 3T Philips MRI and Profound V1 Sonalleve high intensity focused ultrasound (high intensity focused ultrasound system. An MR-compatible robot was configured to induce motion on custom gelatin phantoms. Trials with periodic and sporadic motion were introduced on phantoms while hyperthermia was administered. The PCA-PDF algorithm was augmented with a predictive atlas to better compensate for larger sporadic motion.

RESULTS

During periodic motion, the temperature SD in the thermometry was improved from1 . 1 ± 0 . 1 $$ 1.1\pm 0.1 $$ to0 . 5 ± 0 . 1 ∘ $$ 0.5\pm 0.{1}^{\circ } $$ C with both the original and augmented PCA-PDF application. For large sporadic motion, the augmented atlas improved the motion compensation from the original PCA-PDF correction from8 . 8 ± 0 . 5 $$ 8.8\pm 0.5 $$ to0 . 7 ± 0 . 1 ∘ $$ 0.7\pm 0.{1}^{\circ } $$ C.

CONCLUSION

The PCA-PDF algorithm improved temperature accuracy to <1°C during periodic motion, but was not able to adequately address sporadic motion. By augmenting the PCA-PDF algorithm, temperature SD during large sporadic motion was also reduced to <1°C, greatly improving the original PCA-PDF algorithm.

High-Intensity Focused Ultrasound in Dentistry: A Literature Review

Although high-intensity focused ultrasound (HIFU) has been applied widely in medicine, utilising its non-invasive dual ablation and thermal coagulation properties, its application in dentistry has primarily remained in the research phase, predominantly in in vitro studies. Nonetheless, there has been a consistent increase in the number of publications on this subject in recent decades, focusing on areas such as remineralisation of dentine surfaces, removal of smear layers, drug delivery, and microbial elimination. The number of advantages HIFU can offer, such as its non-surgical nature, absence of ionising radiation, lack of residue, and absence of aerosols, is driving this upward trend, indicating the potential for HIFU in clinical dentistry and ongoing efforts towards developing HIFU-based devices for routine dental use. This succinct review aims to outline the historical context, operational mechanisms of HIFU, summarise recent dental research, and provide a forward-looking perspective on the role of HIFU in modern clinical dentistry.

MRI-based monitoring of prostate cancer after HIFU: Inter-reader agreement and diagnostic performance of the PI-FAB score

PURPOSE

To investigate inter-reader agreement, and diagnostic performance of the Prostate Imaging after Focal Ablation (PI-FAB) score applied to multiparametric MRI (mpMRI) in patients who underwent focal high-intensity focused ultrasound (HIFU) therapy for localized prostate cancer.

METHODS

In this retrospective, IRB-approved, single-center study, 73 men, who underwent focal HIFU treatment and received follow-up mpMRIs with subsequent prostate biopsies, were included. The PI-FAB score was applied to follow-up MRIs at 6, 12, and 36 months post-HIFU by two radiologists with different experience levels. Inter-reader agreement was assessed using Gwet's AC1, and the diagnostic performance of the PI-FAB score was assessed in relation to histopathologic results of subsequent prostate biopsies for each reader.

RESULTS

PI-FAB scores showed substantial to almost perfect inter-reader agreement (AC1: 0.80-0.95) and demonstrated high specificity (Reader 1: 90-98 %, Reader 2: 87-98 %) and NPVs (Reader 1: 91-100 %, Reader 2: 88-97 %) in ruling out residual or recurrent in-field prostate cancer post-HIFU. Sensitivity (Reader 1: ≥43 %, Reader 2: ≥14 %) and PPVs (Reader 1: ≥33 %, Reader 2: ≥14 %) were mostly relatively lower, with notable disparities between the two readers, indicating the potential influence of radiologist experience.

CONCLUSIONS

The PI-FAB score provides a consistent and reliable tool for post-HIFU monitoring of prostate cancer using mpMRI. It demonstrates substantial to almost perfect inter-reader agreement and is particularly effective in excluding in-field residual or recurrent prostate cancer post-HIFU treatment. Its application can potentially enhance post-treatment patient care, emphasizing its value as a non-invasive MRI-based monitoring approach after focal ablative therapy of the prostate.

Salvage high-intensity focused ultrasound (S-HIFU) for recurrence after primary radiotherapy of prostate cancer

OBJECTIVES

To evaluate functional and oncological outcomes of salvage high-intensity focal ultrasound (S-HIFU) after external beam radiotherapy (EBRT) failure in prostate cancer (PCa) patients.

METHODS

This single-center study included patients who underwent S-HIFU for local recurrence after EBRT between 2006 and 2023. Cancer-specific survival, metastasis-free survival and progression-free survival were illustrated using Kaplan-Meier curves. Disease progression was defined by one of the following criteria: increase of 2ng/mL or more above the PSA nadir, positive post-S-HIFU biopsy or initiation of androgen deprivation therapy (ADT). Multivariable Cox proportional hazards model was used to identify predictors of disease progression after S-HIFU.

RESULTS

A total of 52 S-HIFU sessions for 48 patients were performed. Median time between EBRT and S-HIFU was 6.5 years. Median PSA before S-HIFU was 3.2ng/mL and median PSA nadir after S-HIFU was 0.58ng/mL. A total of 39 (81.3%) complications was recorded, including 3 (6.3%) high grade complications according to the Clavien-Dindo classification. After a median follow-up period of 6 years, 14 (29.2%) patients developed metastatic disease. Eighteen (37.5%) patients had no recurrence, whereas 30 (62.5%) patients received ADT for disease progression. The estimated 5-yr cancer-specific survival (CSS), metastasis-free survival (MFS) and progression-free survival rates (PFSR) were 100%, 79.9% (95% CI 67-92) and 41.2% (95% CI 74-96), respectively. The estimated 10-yr CSS, MFS and PFSR were 80% (95% CI 45-100), 50.7% (95% CI 19.4-82.1) and 14% (95% CI 10.8-45), respectively. The hazard of progression increased with the intermediate (HR 3.8; 95% CI 0.99 to 15; p=0.049) and high pre-EBRT d'Amico-s risk group (HR 4.1; 95% CI 0.98 to 16.2; p=0.050). Also, the time between EBRT and S-HIFU was significantly associated with risk of progression (HR 0.61; 95% CI 0.43 to 0.86; p=0.004). No significant difference linked to the disease progression (DP) risk was found between focal vs whole-gland treatment (p=0.70).

CONCLUSION

Physicians should consider HIFU as a local salvage treatment after failed EBRT, thus avoiding or delaying palliative androgen deprivation therapy. Further studies are needed to improve patient selection for this therapy.

LEVEL OF EVIDENCE: 4

Experimental and Computational Analysis of High-Intensity Focused Ultrasound Thermal Ablation in Breast Cancer Cells: Monolayers vs. Spheroids

High-intensity focused ultrasound (HIFU) is a non-invasive therapeutic modality that uses precise acoustic energy to ablate cancerous tissues through coagulative necrosis. In this context, we investigate the efficacy of HIFU ablation in two distinct cellular configurations, namely 2D monolayers and 3D spheroids of epithelial breast cancer cell lines (MDA-MB 231 and MCF7). The primary objective is to compare the response of these two in vitro models to HIFU while measuring their ablation percentages and temperature elevation levels. HIFU was systematically applied to the cell cultures, varying ultrasound intensity and duty cycle during different sonication sessions. The results indicate that the degree of ablation is highly influenced by the duty cycle, with higher duty cycles resulting in greater ablation percentages, while sonication duration has a minimal impact. Numerical simulations validate experimental observations, highlighting a significant disparity in the response of 2D monolayers and 3D spheroids to HIFU treatment. Specifically, tumor spheroids require lower temperature elevations for effective ablation, and their ablation percentage significantly increases with elevated duty cycles. This study contributes to a comprehensive understanding of acoustic energy conversion within the biological system during HIFU treatment for 2D versus 3D ablation targets, holding potential implications for refining and personalizing breast cancer therapeutic strategies.

High-intensity focused ultrasound with visually directed power adjustment for focal treatment of localized prostate cancer: systematic review and meta-analysis

PURPOSE

To characterize patient outcomes following visually directed high-intensity focused ultrasound (HIFU) for focal treatment of localized prostate cancer.

METHODS

We performed a systematic review of cancer-control outcomes and complication rates among men with localized prostate cancer treated with visually directed focal HIFU. Study outcomes were calculated using a random-effects meta-analysis model.

RESULTS

A total of 8 observational studies with 1,819 patients (median age 67 years; prostate-specific antigen 7.1 mg/ml; prostate volume 36 ml) followed over a median of 24 months were included. The mean prostate-specific antigen nadir following visually directed focal HIFU was 2.2 ng/ml (95% CI 0.9-3.5 ng/ml), achieved after a median of 6 months post-treatment. A clinically significant positive biopsy was identified in 19.8% (95% CI 12.4-28.3%) of cases. Salvage treatment rates were 16.2% (95% CI 9.7-23.8%) for focal- or whole-gland treatment, and 8.6% (95% CI 6.1-11.5%) for whole-gland treatment. Complication rates were 16.7% (95% CI 9.9-24.6%) for de novo erectile dysfunction, 6.2% (95% CI 0.0-19.0%) for urinary retention, 3.0% (95% CI 2.1-3.9%) for urinary tract infection, 1.9% (95% CI 0.1-5.3%) for urinary incontinence, and 0.1% (95% CI 0.0-1.4%) for bowel injury.

CONCLUSION

Limited evidence from eight observational studies demonstrated that visually directed HIFU for focal treatment of localized prostate cancer was associated with a relatively low risk of complications and acceptable cancer control over medium-term follow-up. Comparative, long-term safety and effectiveness results with visually directed focal HIFU are lacking.

Changes of serum CA125 and PGE2 before and after high-intensity focused ultrasound combined with GnRH-a in treatment of patients with adenomyosis

This study aimed to investigate the changes of serum carbohydrate antigen 125 (CA125) and prostaglandin E2 (PGE2) in patients with adenomyosis before and after treatment with high-intensity focused ultrasound (HIFU) combined with gonadotropin-releasing hormone agonist (GnRH-a). One hundred and sixty-five patients with adenomyosis who received HIFU combined with GnRH-a were selected as case group. Sixty-five healthy women who underwent physical examination at the same time were taken as normal control group. At the end of follow-up 6 months after treatment, the case group were divided into effective subgroup and ineffective subgroup according to clinical efficacy. Changes of serum CA125 and PGE2 were analyzed. Serum CA125 and PGE2 levels in the case group were higher than those in the normal control group before treatment (both P < 0.001). Serum CA125 and PGE2 levels in the case group 6 months after treatment were lower than those before treatment (both P < 0.001). There was no difference in serum CA125 and PGE2 levels between effective subgroup and ineffective subgroup before treatment (P = 0.351, 0.284, respectively). Serum CA125 and PGE2 levels in the effective subgroup were lower than those in the ineffective subgroup 6 months after treatment (both P < 0.001). Serum CA125 and PGE2 may be involved in the development of adenomyosis, and their expression levels may be related to the prognosis of patients. Levels of serum CA125 and PGE2 in patients with adenomyosis decrease after treatment with HIFU combined with GnRH-a. The detection of serum CA125 and PGE2 may be used as an index to diagnose adenomyosis and evaluate the therapeutic effect of HIFU combined with GnRH-a.

In vivo exposure of the bladder using a non-invasive high intensity focused ultrasound toroidal transducer

A toroidal high-intensity focused ultrasound (HIFU) transducer was used to expose normal bladder wall tissues non-invasively in vivo in a porcine model in order to investigate the potential to treat bladder tumors. The transducer was divided into 32 concentric rings with equal surface areas, operating at 2.5 MHz. Eight animals were split into two groups of 4. In the first group, post-mortem evaluation was performed immediately after ultrasound exposure. In the second group, animals survived for up to seven days before post-mortem evaluation. The ultrasound imaging guided HIFU device was hand-held during the procedure using optical tracking to ensure correct targeting. One thermal lesion in each animal was created using a 40 s exposure at 80 acoustic Watts (free-field) in the trigone region of the bladder wall. The average (±Standard Deviation) abdominal wall and bladder wall thicknesses were 10.3 ± 1.4 mm and 1.1 ± 0.4 mm respectively. The longest and shortest axes of the HIFU ablations were 7.7 ± 2.9 mm and 6.0 ± 1.8 mm, respectively, resulting in an ablation of the whole thickness of the bladder wall in most cases. Ablation were performed at an average depth (distance from the skin surface to the centre of the HIFU lesion) of 42.5 ± 3.8 mm and extended throughout the thickness of the bladder. There were two cases of injury to tissues immediately adjacent to the bladder wall but without signs of perforation, as confirmed by histological analysis. Non-invasive HIFU ablation using a hand-held toroidal transducer was successfully performed to destroy regions of the bladder wall in vivo.

Ablation for malignant liver tumor using high-intensity focused ultrasound and radio-frequency: A meta-analysis

BACKGROUND

Primary liver cancer is a major health issue, so finding the most effective treatment is vital.

OBJECTIVE

The present meta-analysis compares high-intensity focused ultrasound (HIFU) to radiofrequency (RF) ablation for primary liver cancer treatment.

METHODS

PubMed, MEDLINE, CNKI, VIP, and Wanfang were used to search for English and Chinese papers. After carefully confirming data completeness and applying inclusion and exclusion criteria, RevMan 5.3 was used to evaluate the included literature. Data analysis utilized a fixed-effects model for heterogeneity between 0.1 and 0.5.

RESULTS

The meta-analysis included 304 patients: 119 had HIFU and 185 RF ablation. For primary liver cancer, HIFU and RF ablation were equally efficacious (odds ratio 1.02, 95% confidence interval [0.54, 1.92]). Overall survival, disease-free survival, and complications at 1, 2, and 3 years were not significantly different (odds ratio 0.72, 95% confidence range [0.04, 12.79], P= 0.82).

CONCLUSION

The meta-analysis shows no significant difference in efficacy, long-term survival rates, or complication rates between HIFU and RF ablation for primary liver cancer, but more large-scale, high-quality randomized clinical trials are needed to prove their equivalence. Both therapy strategies seem promising, but additional information is needed to determine their respective merits.

MR-guided focused ultrasound in movement disorders and beyond: Lessons learned and new frontiers

The development of MR-guided focused ultrasound (MRgFUS) has provided a new therapeutic tool for neuropsychiatric disorders. In contrast to previously available neurosurgical techniques, MRgFUS allows precise impact on deep brain structures without the need for incision and yields an immediate effect. In its high-intensity modality (MRgHIFU), it produces accurate therapeutic thermoablation in previously selected brain targets. Importantly, the production of the lesion is progressive and highly controlled in real-time by both neuroimaging and clinical means. MRgHIFU ablation is already an accepted and widely used treatment for medically-refractory Parkinson's disease and essential tremor. Notably, other neurological disorders and diverse brain targets, including bilateral treatments, are currently under examination. Conversely, the low-intensity modality (MRgLIFU) shows promising prospects in neuromodulation and transient blood-brain barrier opening (BBBO). In the former circumstance, MRgLIFU could serve as a powerful clinical and research tool for non-invasively modulating brain activity and function. BBBO, on the other hand, emerges as a potentially impactful method to influence disease pathogenesis and progression by increasing brain target engagement of putative therapeutic agents. While promising, these applications remain experimental. As a recently developed technology, MRgFUS is not without challenges and questions to be addressed. Further developments and broader experience are necessary to enhance MRgFUS capabilities in both research and clinical practice, as well as to define device constraints. This clinical mini-review aims to provide an overview of the main evidence of MRgFUS application and to highlight unmet needs and future potentialities of the technique.

Healing Process after High-Intensity Focused Ultrasound Treatment of Benign Skin Lesions: Dermoscopic Analysis and Treatment Guidelines

Background: High-Intensity Focused Ultrasound (HIFU) has emerged as a precise and non-invasive modality for tissue ablation and healing. This study presents a detailed dermoscopic analysis of skin healing post-High-Intensity Focused Ultrasound (HIFU) treatment, focusing on common benign skin lesions, such as seborrheic keratosis, sebaceous hyperplasia, vascular lesions, and sebaceous nevi. Methods: Prior to HIFU treatment, a comprehensive assessment was conducted, integrating ultrasound scanning and clinical evaluations. The TOOsonix System ONE-M was employed for HIFU treatments, with parameters tailored to each lesion type. Results: A common pattern observed across all lesions includes initial whitening post treatment, followed by scab formation and the development of a pink area with reparative vessels. This study, however, highlights distinct differences in fibrosis patterns and healing timelines across different lesion types. Each lesion type exhibited unique fibrosis patterns post treatment. Flatter variants of seborrheic keratosis healed within a month, displaying hypopigmentation and reparative vessels, alongside a distinct lattice fibrosis pattern in more verrucous forms, which took about two months to heal. Sebaceous hyperplasia, characterized by rapid healing within three weeks, demonstrated fibrosis with pink areas and perpendicular white lines, concluding with a slight depression. Vascular lesions varied in healing time based on depth, with superficial ones showing whitening and crust formation, while deeper lesions had vessel occlusion and size reduction accompanied by concentric fibrotic bands. Sebaceous nevi presented the longest healing duration of three months, characterized by amorphous white-gray structures, scab formation, and the emergence of pink areas with branching vessels, leading to clear skin with reduced white lines. Conclusions: in conclusion, this meticulous clinical evaluation highlights the unique healing characteristics and timelines for each skin lesion type treated with HIFU. These insights are invaluable for optimizing follow-up assessments, identifying potential complications, and refining treatment protocols. By providing detailed insights into the healing timelines and patterns for different types of lesions, patients can be better informed about their post-treatment journey.

Intraoperative Imaging Techniques in Oncology

Imaging-based procedures have become well integrated into the diagnosis and management of oncological patients and play a significant role in reducing morbidity and mortality rates. Here we describe the established and upcoming surgical oncological imaging techniques and their impact on cancer management.

Nanotargeted Cationic Lipid Microbubbles Carrying HSV-TK Gene Inhibit the Development of Subcutaneous Liver Tumor Model After HIFU Ablation

OBJECTIVES

High-intensity focused ultrasound (HIFU) has been widely used in clinical settings and has achieved suitable results in the treatment of many cancerous or noncancerous diseases. However, in the treatment of liver cancer, because the tumor is located deep within the liver tissue, when ultrasound penetrates the tissue, it will inevitably produce sound energy attenuation. This attenuation limits the reliability of HIFU treatment, reduce the efficacy of HIFU, and increase the risk of tumor recurrence.

METHODS

Cationic microbubbles (CMB) were successfully linked with GPC3 and HSV-TK plasmids, and targeted gene-carrying CMB were successfully constructed. Moreover, the gene-targeted cation microbubbles had suitable targeting and can specifically bind with liver cancer cells.

RESULTS

The HSV-TK transfection efficiency was high and had a significant inhibitory effect on the proliferation and invasion of liver cancer cells. After the gene-carrying cation microbubbles entered the animal body, they had a great targeting effect in vivo. They transfected the target genes into liver cancer cells, and the HSV-TK/GCV system initiated cell death, demonstrating that these targeted microbubbles, enhanced HIFU treatment.

CONCLUSIONS

Overall, CMB combined with a GPC3 antibody and HSV-TK plasmid can target residual subcutaneous liver tumor cells under the guidance of GPC3 antibody, and kill residual subcutaneous liver tumor cells under the action of ultrasound, thus enhancing the therapeutic effect of HIFU on liver cancer.

MR Imaging-Guided Prostate Cancer Therapies

Prostate cancer is the most common malignancy diagnosed in men. MR imaging-guided therapies for prostate cancer have become an increasingly common treatment alternative to traditional whole-gland therapies, such as radical prostatectomy or radiation therapy. This is especially true in men with localized, low- to intermediate-risk prostate cancer. Although long-term oncologic data remain limited, the authors describe several MR imaging-guided therapeutic options for the treatment of prostate cancer, including cryoablation, laser ablation, transrectal high-intensity focused ultrasound, and transurethral ultrasound ablation.

MRI compatibility testing of commercial high intensity focused ultrasound transducers

PURPOSE

The study aimed to compare the performance of eight commercially available single-element High Intensity Focused Ultrasound (HIFU) transducers in terms of Magnetic Resonance Imaging (MRI) compatibility.

METHODS

Imaging of an agar-based MRI phantom was performed in a 3 T MRI scanner utilizing T2-Weighted Fast Spin Echo (FSE) and Fast low angle shot (FLASH) sequences, which are typically employed for high resolution anatomical imaging and thermometry, respectively. Reference magnitude and phase images of the phantom were compared with images acquired in the presence of each transducer in terms of the signal to noise ratio (SNR), introduced artifacts, and overall image quality.

RESULTS

The degree of observed artifacts highly differed among the various transducers. The transducer whose backing material included magnetic impurities showed poor performance in the MRI, introducing significant susceptibility artifacts such as geometric distortions and signal void bands. Additionally, it caused the most significant SNR drop. Other transducers were shown to exhibit high level of MRI compatibility as the resulting images closely resembled the reference images with minimal to no apparent artifacts and comparable SNR values.

CONCLUSIONS

The study findings may facilitate researchers to select the most suitable transducer for their research, simultaneously avoiding unnecessary testing. The study further provides useful design considerations for MRI compatible transducers.

External validation of biochemical recurrence definition to predict oncologic outcomes following focal therapy for localized prostate cancer using high intensity focused ultrasound

PURPOSE

This is an external validation of several biochemical recurrence definitions based on prostate specific antigen criteria (PSA). The purpose is to predict the need of additional treatment and failure after focal therapy using high intensity focused ultrasound (HIFU) for localized prostate cancer (PCa).

MATERIALS AND METHODS

A total of 343 consecutive patients who underwent HIFU with Ablatherm® and Focal One® devices between June 2001 and November 2020 were identified. Treatment failure was defined as clinically significant PCa on postoperative biopsy, the need for salvage radical or systematic treatment, metastasis, or PCa-related death. The biochemical recurrence definitions tested were PSA nadir, time to PSA nadir, percentage of PSA reduction, Huber et al. criteria defined as PSA nadir + 1 ng/mL at 12 months or PSA nadir + 1.5 ng/mL at 24-36 months. Multivariable Cox regression analysis and decision-curve analysis were used to validate and compare criteria. Kaplan-Meier analysis was used to assess criteria associated with the highest accuracy.

RESULTS

One hundred seventy-eight patients met the inclusion criteria and were analyzed. Overall, 61 (34%) and 41 (23%) patients had an additional treatment and failure with a median follow-up of 52 months. At multivariable analysis, model including Huber et al. criteria exhibited the highest Harrell's C-index for the prediction of the need of additional treatment (hazard ratio [HR]: 10, p < 0.001, c-index: 84%) and treatment failure (HR: 9.1, p < 0.001, c-index: 82%) as well as higher net benefit. The 60-months need of additional treatment and treatment failure-free survival were 89% and 98% compared to 26% and 49%, respectively, when stratified according to Huber et al. criteria (Log-rank test, p < 0.001). Similar results were found after excluding patient with non-clinically significant PCa at initial biopsy.

CONCLUSIONS

We report an external validation of biochemical recurrence definitions predicting the need of additional treatment and failure after focal therapy using HIFU for localized PCa. Huber et al. criteria were identified as the most accurate and could be used to guide clinicians toward further evaluation and salvage treatments.

[Oncological and functional results of focal treatment of localized prostate cancer with HIFU]

INTRODUCTION

In recent years, improved diagnosis of prostate cancer has allowed the development of focal therapy, in order to reduce the morbidity of treatments. Our study assesses the medium-term oncological and functional results of FocalOne® HIFU treatment in localized prostate cancer.

METHODS

This is a retrospective, multicentre study including patients with low- or intermediate-risk localized prostate cancer treated with Focal one HIFU between November 2014 and December 2019. The primary endpoint was the retreatment rate and subgroup analyses were performed to identify predictive factors of retreatment.

RESULTS

One hundred and thirty-seven patients were included with a median follow-up of 25.5 months. Seventy percent of patients had clinical stage T2, 64% had an ISUP score of 2 or 3 on initial biopsies and 38% were treated with hemi-ablation. Follow-up biopsies were performed in 76.6% of patients during follow-up with 21.8% having clinically significant cancers. The retreatment rate at 24 months was 37.2%, with positive biopsies being the primary criterion for retreatment. Patients with a PSA>8ng/mL had a significantly higher retreatment rate. Finally, morbidity remained acceptable with 5.8% of patients requiring reoperation for complications and 21% for de novo erectile dysfunction.

CONCLUSION

Our results are in agreement with those of the literature, seeming to indicate a lower morbidity of the focal treatment by HIFU compared to the radical treatments while offering an acceptable oncological control. Prospective randomized trials are ongoing.

LEVEL OF EVIDENCE: 4

Follow-Up of Men Who Have Undergone Focal Therapy for Prostate Cancer with HIFU-A Real-World Experience

PURPOSE

To determine oncological and functional outcomes and side effects after focal therapy of prostate cancer (PCa) with high-intensity focused ultrasound (HIFU).

METHODS

This retrospective single-center study included 57 consecutive patients with localised PCa. Aged 18-80 with ≤2 suspicious lesions on mpMRI (PIRADS ≥ 3), PSA of ≤15 ng/mL, and an ISUP GG of ≤2. HIFU was performed between November 2014 and September 2018. All men had an MRI/US fusion-guided targeted biopsy (TB) combined with a TRUS-guided 10-core systematic biopsy (SB) prior to focal therapy. HIFU treatment was performed as focal, partial, or hemiablative, depending on the prior histopathology. Follow-up included Questionnaires (IIEF-5, ICIQ, and IPSS), prostate-specific antigen (PSA) measurement, follow-up mpMRI, and follow-up biopsies.

RESULTS

The median age of the cohort was 72 years (IQR 64-76), and the median PSA value before HIFU was 7.3 ng/mL (IQR 5.75-10.39 ng/mL). The median follow-up was 27.5 (IQR 23-41) months. At the time of the follow-up, the median PSA value was 2.5 ng/mL (IQR 0.94-4.96 ng/mL), which shows a significant decrease (p < 0.001). In 17 (29.8%) men, mpMRI revealed a suspicious lesion, and 19 (33.3%) men had a positive biopsy result. Only IIEF values significantly decreased from 16 (IQR 10.75-20.25) to 11.5 (IQR 4.5-17) (p < 0.001). The rate of post-HIFU complications was low, at 19.3% (11 patients). The limitation of this study is the lack of long-term follow-up.

CONCLUSIONS

HIFU as a therapy option for nonmetastatic, significant prostate cancer is effective in the short term for carefully selected patients and shows a low risk of adverse events and side effects.

Sequential high-intensity focused ultrasound treatment combined with chemotherapy for inoperable pancreatic cancer: a retrospective analysis for prognostic factors and survival outcomes

OBJECTIVE

To evaluate the effect of HIFU (High-Intensity Focused Ultrasound) therapy on the survival and prognosis of patients with inoperable pancreatic cancer, and the clinical application of serological prognostic indicators.

METHODS

We retrospectively analyzed the clinicopathological features, laboratory tests and follow-ups of 192 patients. Among the patients, 57 were treated with HIFU prior to chemotherapy (HIFU-priority), and 135 patients received chemotherapy followed by HIFU (HIFU-second). Univariate and multivariate Cox regression analysis was used to determine the prognostic value of tumor inflammation-related serological markers. A nomogram model was established based on the identified prognostic factors.

RESULTS

Univariate analysis showed that receiving the treatment regimen in HIFU-priority was a significant protective factor for overall survival (OS, p < 0.001). Tumor stage, high C-reactive protein (CRP), high gamma-glutamyl transferase(γGT) high carbohydrate antigen 125 (CA125), high neutrophil-to-lymphocyte ratio (NLR), high lymphocyte-to-monocyte ratio (LMR) and liver metastasis were significant risk factors for poor prognosis (p < 0.05). CRP combined with normal tumor marker CA125 (CRP + CA125) was associated with longer OS (p = 0.005). Multivariate analysis shows that HIFU-priority is a protective factor for OS (Hazard Ratio, HR: 0.38; 95% confidence interval(CI): 0.25-0.57), tumor stage (HR: 1.61; 95% CI: 1.12-2.31), CRP + CA125 (HR: 1.46; 95% CI: 1.02-2.08) and γGT (HR: 1.44; 95% CI: 1.04-1.98) are risk factors for OS and serve as independent prognostic factors in the nomogram.

CONCLUSION

Early application of HIFU treatment improves the OS of patients with inoperable pancreatic cancer. CRP + CA125 and γGT are independent prognostic factors.

Study on method of organ section retention and tracking through deep learning in automated diagnostic and therapeutic robotics

PURPOSE

In high-intensity focused ultrasound (HIFU) treatment of the kidney and liver, tracking the organs is essential because respiratory motions make continuous cauterization of the affected area difficult and may cause damage to other parts of the body. In this study, we propose a tracking system for rotational scanning, and propose and evaluate a method for estimating the angles of organs in ultrasound images.

METHODS

We proposed AEMA, AEMAD, and AEMAD++ as methods for estimating the angles of organs in ultrasound images, using RUDS and a phantom to acquire 90-degree images of a kidney from the long-axis image to the short-axis image as a data set. Six datasets were used, with five for preliminary preparation and one for testing, while the initial position was shifted by 2 mm in the contralateral axis direction. The test data set was evaluated by estimating the angle using each method.

RESULTS

The accuracy and processing speed of angle estimation for AEMA, AEMAD, and AEMAD++ were 23.8% and 0.33 FPS for AEMAD, 32.0% and 0.56 FPS for AEMAD, and 29.5% and 3.20 FPS for AEMAD++, with tolerance of ± 2.5 degrees. AEMAD++ offered the best speed and accuracy.

CONCLUSION

In the phantom experiment, AEMAD++ showed the effectiveness of tracking the long-axis image of the kidney in rotational scanning. In the future, we will add either the area of surrounding organs or the internal structure of the kidney as a new feature to validate the results.

Advanced software for MRgFUS treatment planning

BACKGROUND AND OBJECTIVES

Herein, a user-friendly software platform for 3-dimensional Focused Ultrasound treatment planning based on Magnetic Resonance Imaging (MRI) images is presented.

METHODS

The software directly retrieves and loads MRI images. Various design tools can be used on the MRI images to define the treatment area and the sonication parameters. Based on the treatment plan, the software controls the robotic motion and motion pattern of Magnetic Resonance guided Focused Ultrasound (MRgFUS) robotic systems to execute the treatment procedure. Real-time treatment monitoring is achieved through MRI images and thermometry. The software's functionality and performance were evaluated in both laboratory and MRI environments. Different treatment plans were designed on MRI images and sonications were executed on agar-based phantoms and polymer films.

RESULTS

Magnetic Resonance (MR) thermometry maps were acquired in the agar-based phantoms. An exceptional agreement was observed between the software-planned treatment area and the lesions produced on the polymer films.

CONCLUSIONS

The developed software was successfully integrated with the MRI and robotic system controls for performing accurate treatment planning and real-time monitoring during sonications. The software provides an extremely user-friendly interface, while in the future it could be enhanced by providing dynamic modulation of the ultrasonic parameters during the treatment process.

Focal therapy of prostate cancer: Assessment with prostate-specific membrane antigen (PSMA) imaging

Focal therapy of prostate cancer (PCa) is currently of great interest, but a metric of success. other than biopsy, is not yet available. In a patient with a repeatedly negative MRI and negative systematic biopsies, a scan employing the radioisotope ⁶⁸Ga-PSMA-11 PET/CT identified a PSMA-avid hotspot in the prostate. PSMA-guided biopsy confirmed the diagnosis of a clinically-significant PCa. Following ablation of the lesion with high-intensity focused ultrasound (HIFU), the PSMA-avid lesion disappeared and targeted biopsy confirmed a fibrotic scar with no residual cancer. PSMA imaging may have a role in guiding diagnosis, focal ablation, and follow-up of men with PCa.

The Applications of High-Intensity Focused Ultrasound (HIFU) Ablative Therapy in the Treatment of Primary Breast Cancer: A Systematic Review

BACKGROUND

This study evaluates the role of high-intensity focused ultrasound (HIFU) ablative therapy in treating primary breast cancer.

METHODS

PubMed and Scopus databases were searched according to the PRISMA guidelines to identify studies from 2002 to November 2022. Eligible studies were selected based on criteria such as experimental study type, the use of HIFU therapy as a treatment for localised breast cancer with objective clinical evaluation, i.e., clinical, radiological, and pathological outcomes. Nine studies were included in this study.

RESULTS

Two randomised controlled trials and seven non-randomised clinical trials fulfilled the inclusion criteria. The percentage of patients who achieved complete (100%) coagulation necrosis varied from 17% to 100% across all studies. Eight of the nine studies followed the treat-and-resect protocol in which HIFU-ablated tumours were surgically resected for pathological evaluation. Most breast cancers were single, solitary, and palpable breast tumours. Haematoxylin and eosin stains used for histopathological evaluation showed evidence of coagulation necrosis. Radiological evaluation by MRI showed an absence of contrast enhancement in the HIFU-treated tumour and 1.5 to 2 cm of normal breast tissue, with a thin peripheral rim of enhancement indicative of coagulation necrosis. All studies did not report severe complications, i.e., haemorrhage and infection. Common complications related to HIFU ablation were local mammary oedema, pain, tenderness, and mild to moderate burns. Only one third-degree burn was reported. Generally, the cosmetic outcome was good. The five-year disease-free survival rate was 95%, as reported in two RCTs.

CONCLUSIONS

HIFU ablation can induce tumour coagulation necrosis in localised breast cancer, with a favourable safety profile and cosmetic outcome. However, there is variable evidence of complete coagulation necrosis in the HIFU-treated tumour. Histopathological evidence of coagulation necrosis has been inconsistent, and there is no reliable radiological modality to assess coagulation necrosis confidently. Further exploration is needed to establish the accurate ablation margin with a reliable radiological modality for treatment and follow-up. HIFU therapy is currently limited to single, palpable breast tumours. More extensive and randomised clinical trials are needed to evaluate HIFU therapy for breast cancer, especially where the tumour is left in situ.

Efficacy of high-intensity focused ultrasound combined with LNG-IUS for adenomyosis: a systematic review and meta-analysis

OBJECTIVE

To evaluate the efficacy and safety of high-intensity focused ultrasound (HIFU) combined with the levonorgestrel intrauterine system (LNG-IUS) for adenomyosis.

METHODS

We searched PubMed, Embase, Cochrane Library, Web of Science, CNKI, SinoMed, Wanfang, and VIP databases from their inception to Nov 20, 2021 for relevant articles that compared HIFU combined with LNG-IUS vs. HIFU alone in patients with adenomyosis. RevMan5.4 software was used for the data analysis. The primary outcome was changes in volume of the uterine. Secondary outcomes included visual analog scale (VAS) scores for dysmenorrhea, serum CA125 level, recurrence rate, changes in volume of the adenomyotic lesion, menstrual volume scores, and adverse reactions. Data synthesis was conducted using a random-effects model with significant heterogeneity (I2 > 50%), and using a fixed-effects model otherwise. This study is registered on the PROSPERO platform (CRD42021295214).

RESULTS

The final analysis included 13 studies, with a total of 1861 patients. Results of analysis revealed that there was no significant difference in uterine volume reduction between the HIFU control group and the HIFU/LNG-IUS group at 3 months after procedure (MD:30.63). Compared with the HIFU control group, the HIFU/LNG-IUS group had more pronounced reduction in uterine volume at 6 (MD:29.04) and 12 months (MD:22.10) after procedure. The HIFU/LNG-IUS group has lower VAS scores for dysmenorrhea than the HIFU control group at 3 (MD:1.68), 6 (MD:1.69), and 12 months (MD:1.30) after procedure. Serum CA125 level in the HIFU/LNG-IUS group decreased more significantly than the HIFU control group at 6 (MD:18.34) and 12 months (MD:18.49) after procedure. The recurrence rate in the HIFU/LNG-IUS group was lower than that in the HIFU control group (RR:0.20).

CONCLUSIONS

Compared to HIFU control group, HIFU/LNG-IUS group for the management of adenomyosis had more advantages in alleviating symptoms and decreasing the volumes of the uterine and adenomyotic lesions. However, since the number of the included studies was too small and some of them were not RCT, this conclusion needs to be referenced with caution.

Pilot ex vivo study on non-thermal ablation of human prostate adenocarcinoma tissue using boiling histotripsy

Focused ultrasound technologies are of growing interest for noninvasive ablation of localized prostate cancer (PCa). Here we present the results of the first case study evaluating the feasibility of non-thermal mechanical ablation of human prostate adenocarcinoma tissue using the boiling histotripsy (BH) method on ex vivo tissue. High intensity focused ultrasound field was generated using a 1.5-MHz custom-made transducer with nominal F#=0.75. A sonication protocol of 734 W acoustic power, 10-ms long BH-pulses, 30 pulses per focal spot, 1 % duty cycle, and 1 mm distance between single foci was tested in an ex vivo human prostate tissue sample containing PCa. The protocol used here has been successfully applied in the previous BH studies for mechanical disintegration of ex vivo prostatic human tissue with benign hyperplasia. BH treatment was monitored using B-mode ultrasound. Post-treatment histologic analysis demonstrated BH produced liquefaction of the targeted tissue volume. BH treated benign prostate parenchyma and PCa had similar tissue fractionation into subcellular fragments. The results of the study demonstrated that PCa tumor tissue can be mechanically ablated using the BH method. Further studies will aim on optimizing protocol parameters to accelerate treatment while maintaining complete destruction of the targeted tissue volume into subcellular debris.

Intra-operative High-Intensity Focused Ultrasound in Patients With Colorectal Liver Metastases: A Prospective Ablate-and-Resect Study

OBJECTIVE

High-intensity focused ultrasound (HIFU) is a recent, non-ionizing and non-invasive technology of focal destruction. Independence from the heat-sink effect of blood flow makes HIFU an interesting technique for focal ablation of liver tumors. Current available technology is based on extracorporeal treatment that limits use of HIFU for the treatment of liver tumors, as elementary ablations are small and must be juxtaposed to treat tumors, resulting in long-duration treatment. We developed an HIFU probe with toroidal technology, which increases the volume of ablation, for intra-operative use, and we assessed the feasibility and efficacy of this device in patients with colorectal liver metastasis (CLM) measuring less than 30 mm.

METHODS

This study was an ablate-and-resect, prospective, single-center, phase II study. All ablations were performed in the area of liver scheduled for liver resection to avoid loss of chance of recovery. The primary objective was to ablate CLM with safety margins (>5 mm).

RESULTS

Between May 2014 and July 2020, 15 patients were enrolled and 24 CLM were targeted. The HIFU ablation time was 370 s. In total, 23 of 24 CLM were successfully treated (95.8%). No damage occurred to extrahepatic tissues. HIFU ablations were oblate shaped with an average long axis of 44.3 ± 6.1 mm and an average shortest axis of 35.9 ± 6.7 mm. On pathological examination, the average diameter of the treated metastasis was 12.2 ± 4.8 mm.

CONCLUSION

Intra-operative HIFU can safely and accurately produce large ablations in 6 min with real-time guidance (ClinicalTrials.gov identifier: NCT01489787).

An interpretable MRI-based radiomics model predicting the prognosis of high-intensity focused ultrasound ablation of uterine fibroids

BACKGROUND

Accurate preoperative assessment of the efficacy of high-intensity focused ultrasound (HIFU) ablation for uterine fibroids is essential for good treatment results. The aim of this study was to develop robust radiomics models for predicting the prognosis of HIFU-treated uterine fibroids and to explain the internal predictive process of the model using Shapley additive explanations (SHAP).

METHODS

This retrospective study included 300 patients with uterine fibroids who received HIFU and were classified as having a favorable or unfavorable prognosis based on the postoperative nonperfusion volume ratio. Patients were divided into a training set (N = 240) and a test set (N = 60). The 1295 radiomics features were extracted from T2-weighted imaging (T2WI) and contrast-enhanced T1-weighted imaging (CE-T1WI) scans. After data preprocessing and feature filtering, radiomics models were constructed by extreme gradient boosting and light gradient boosting machine (LightGBM), and the optimal performance was obtained by Bayesian optimization. Finally, the SHAP approach was used to explain the internal prediction process.

RESULTS

The models constructed using LightGBM had the best performance, and the AUCs of the T2WI and CE-T1WI models were 87.2 (95% CI = 87.1-87.5) and 84.8 (95% CI = 84.6-85.7), respectively. The use of SHAP technology can help physicians understand the impact of radiomic features on the predicted outcomes of the model from a global and individual perspective.

CONCLUSION

Multiparametric radiomic models have shown their robustness in predicting HIFU prognosis. Radiomic features can be a potential source of biomarkers to support preoperative assessment of HIFU treatment and improve the understanding of uterine fibroid heterogeneity.

CLINICAL RELEVANCE STATEMENT

An interpretable radiomics model can help clinicians to effectively predict the prognosis of HIFU treatment for uterine fibroids. The heterogeneity of fibroids can be characterized by various radiomics features and the application of SHAP can be used to visually explain the prediction process of radiomics models.

Case Report: Desmoid tumor response to magnetic resonance-guided high intensity focused ultrasound over 4 years

Desmoid tumors are a rare form of cancer, which show locally aggressive invasion of surrounding tissues and may occur anywhere in the body. Treatment options comprise conservative watch and wait strategies as tumors may show spontaneous regression as well as surgical resection, radiation therapy, nonsteroidal anti-inflammatory drugs (NSAID), chemotherapy, or local thermoablative approaches for progressive disease. The latter comprises cryotherapy, radiofrequency, microwave ablation, or thermal ablation with high intensity focused ultrasound (HIFU) as the only entirely non-invasive option. This report presents a case where a desmoid tumor at the left dorsal humerus was 2 times surgically resected and, after recurrence, thermally ablated with HIFU under magnetic resonance image-guidance (MR-HIFU). In our report, we analyze tumor volume and/or pain score during standard of care (2 years) and after HIFU treatment over a 4-year follow-up period. Results showed MR-HIFU treatment led to complete tumor remission and pain response.

Weakly nonlinear focused ultrasound in viscoelastic media containing multiple bubbles

To facilitate practical medical applications such as cancer treatment utilizing focused ultrasound and bubbles, a mathematical model that can describe the soft viscoelasticity of human body, the nonlinear propagation of focused ultrasound, and the nonlinear oscillations of multiple bubbles is theoretically derived and numerically solved. The Zener viscoelastic model and Keller-Miksis bubble equation, which have been used for analyses of single or few bubbles in viscoelastic liquid, are used to model the liquid containing multiple bubbles. From the theoretical analysis based on the perturbation expansion with the multiple-scales method, the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation, which has been used as a mathematical model of weakly nonlinear propagation in single phase liquid, is extended to viscoelastic liquid containing multiple bubbles. The results show that liquid elasticity decreases the magnitudes of the nonlinearity, dissipation, and dispersion of ultrasound and increases the phase velocity of the ultrasound and linear natural frequency of the bubble oscillation. From the numerical calculation of resultant KZK equation, the spatial distribution of the liquid pressure fluctuation for the focused ultrasound is obtained for cases in which the liquid is water or liver tissue. In addition, frequency analysis is carried out using the fast Fourier transform, and the generation of higher harmonic components is compared for water and liver tissue. The elasticity supresses the generation of higher harmonic components and promotes the remnant of the fundamental frequency components. This indicates that the elasticity of liquid suppresses shock wave formation in practical applications.

Improving tremor response to focused ultrasound thalamotomy

MRI-guided high-intensity focused ultrasound thalamotomy is an incisionless therapy for essential tremor. To reduce adverse effects, the field has migrated to treating at 2 mm above the anterior commissure-posterior commissure plane. We perform MRI-guided high-intensity focused ultrasound with an advanced imaging targeting technique, four-tract tractography. Four-tract tractography uses diffusion tensor imaging to identify the critical white matter targets for tremor control, the decussating and non-decussating dentatorubrothalamic tracts, while the corticospinal tract and medial lemniscus are identified to be avoided. In some patients, four-tract tractography identified a risk of damaging the medial lemniscus or corticospinal tract if treated at 2 mm superior to the anterior commissure-posterior commissure plane. In these patients, we chose to target 1.2-1.5 mm superior to the anterior commissure-posterior commissure plane. In these patients, post-operative imaging revealed that the focused ultrasound lesion extended into the posterior subthalamic area. This study sought to determine if patients with focused ultrasound lesions that extend into the posterior subthalamic area have a differnce in tremor improvement than those without. Twenty essential tremor patients underwent MRI-guided high-intensity focused ultrasound and were retrospectively classified into two groups. Group 1 included patients with an extension of the thalamic-focused ultrasound lesion into the posterior subthalamic area. Group 2 included patients without extension of the thalamic-focused ultrasound lesion into the posterior subthalamic area. For each patient, the percent change in postural tremor, kinetic tremor and Archimedes spiral scores were calculated between baseline and a 3-month follow-up. Two-tailed Wilcoxon rank-sum tests were used to compare the improvement in tremor scores, the total number of sonications, thermal dose to achieve initial tremor response, and skull density ratio between groups. Group 1 had significantly greater postural, kinetic, and Archimedes spiral score percent improvement than Group 2 (P values: 5.41 × 10-5, 4.87 × 10-4, and 5.41 × 10-5, respectively). Group 1 also required significantly fewer total sonications to control the tremor and a significantly lower thermal dose to achieve tremor response (P values: 6.60 × 10-4 and 1.08 × 10-5, respectively). No significant group differences in skull density ratio were observed (P = 1.0). We do not advocate directly targeting the posterior subthalamic area with MRI-guided high-intensity focused ultrasound because the shape of the focused ultrasound lesion can result in a high risk of adverse effects. However, when focused ultrasound lesions naturally extend from the thalamus into the posterior subthalamic area, they provide greater tremor control than those that only involve the thalamus.

Enabling Chemo-Immunotherapy with HIFU in Canine Cancer Patients

High intensity focused ultrasound (HIFU) is a promising non-invasive technique for treating solid tumors using thermal and histotripsy-based mechanical ablation. However, its clinical significance in different tumor types is not fully understood. To assess its therapeutic efficacy and immunomodulatory properties, we compared HIFU thermal ablation and histotripsy ablation in dogs with spontaneous tumors. We also evaluated the ability of non-ablative HIFU-based mild hyperthermia (40-45 ºC) to improve Doxorubicin delivery and immunomodulation. Our results showed that HIFU thermal ablation induced tumor remission in the majority of treated patients over 60 days, while histotripsy achieved partial response to stable disease persistence. The adverse effects of thermal ablation were minor to moderate, while histotripsy exposures were relatively well-tolerated. Furthermore, we observed a correlation between HIFU-therapeutic response and serum anti-tumor cytokine profiles and the presence of functionally active cytotoxic immune cells in patients. Similarly, Doxorubicin-treated patients showed improved drug delivery, efficacy, and anti-tumor immune responses with HIFU hyperthermia. In conclusion, our study demonstrates that depending on the tumor type and treatment parameters, HIFU treatments can enable tumor growth control, immune activation, and chemotherapy in veterinary patient. These findings have significant clinical implications and highlight the potential of HIFU as a promising cancer treatment approach.

Single-center, prospective phase 2 trial of high-intensity focused ultrasound (HIFU) in patients with unilateral localized prostate cancer: good functional results but oncologically not as safe as expected

PURPOSE

Focal therapy (FT) for localized prostate cancer (PCa) is only recommended within the context of clinical trials by international guidelines. We aimed to investigate oncological follow-up and safety data of focal high-intensity focused ultrasound (HIFU) treatment.

METHODS

We conducted a single-center prospective study of 29 patients with PCa treated with (focal) HIFU between 2016 and 2021. Inclusion criteria were unilateral PCa detected by mpMRI-US-fusion prostate biopsy and maximum prostate specific antigen (PSA) of 15 ng/ml. Follow-up included mpMRI-US fusion-re-biopsies 12 and 24 months after HIFU. No re-treatment of HIFU was allowed. The primary endpoint was failure-free survival (FFS), defined as freedom from intervention due to cancer progression.

RESULTS

Median follow-up of all patients was 23 months, median age was 67 years and median preoperative PSA was 6.8 ng/ml. One year after HIFU treatment PCa was still detected in 13/ 29 patients histologically (44.8%). Two years after HIFU another 7/29 patients (24.1%) were diagnosed with PCa. Until now, PCa recurrence was detected in 11/29 patients (37.93%) which represents an FFS rate of 62%.One patient developed local metastatic disease 2 years after focal HIFU. Adverse events (AE) were low with 70% of patients remaining with sufficient erectile function for intercourse and 97% reporting full maintenance of urinary continence.

CONCLUSION

HIFU treatment in carefully selected patients is feasible. However, HIFU was oncologically not as safe as expected because of progression rates of 37.93% and risk of progression towards metastatic disease. Thus, we stopped usage of HIFU in our department.

Robotic system for magnetic resonance imaging-guided high-intensity focus ultrasound application: Feasibility of breast fibroadenoma treatment

PURPOSE

This paper presents a high-intensity focus ultrasound (HIFU) robotic system for treating breast fibroadenoma under the guidance of magnetic resonance imaging (MRI). Based on the thermal and mechanical effects of ultrasound, the system aims to deliver ultrasound energy to a target precisely without damaging the normal tissue. The temperature elevation can be monitored in real time by MRI, and the treatment plan can be adjusted during the procedure. The requirements, design specifications, control system and registration of the robotic system are specified.

METHODS

The robotic system was designed with a 3 degrees of freedom manipulator with limit switches and encoders, a customised MRI-compatible breast coil, a water bladder with sets of breast-conforming brackets, and a probe capable of generating ultrasound. Twenty volunteers were recruited for this study, and their data were analysed to provide more precise data for the design. The accuracy of the robot was evaluated in free space using a coordinate measuring machine, phantom and ex vivo porcine tissue in MRI room. The study also verified the signal-to-noise ratio (SNR) of the MRI with the effect of the robotic system.

RESULTS

The research findings revealed that the manipulator exhibited a translational precision of 0.10 ± 0.14 mm, a rotational fidelity around the X direction of 0.11 ± 0.09°, and an oscillatory exactness around the Y direction of 0.10 ± 0.08°. The investigation of positioning accuracy demonstrated that the robot's error in free space was 0.26 ± 0.07 mm. When subjected to MRI room with agar-silica phantom and ex vivo porcine tissue, the positioning accuracy amounted to 1.11 ± 0.47 mm and 1.57 ± 0.52 mm. In the presence of the robotic system, the SNR of the MRI experienced a 4.2% reduction, which had a negligible impact on image quality.

CONCLUSIONS

The conducted experiments validate the efficacy of the proposed MRI-guided HIFU robotic system in executing agar-silica phantom and ex vivo porcine tissue investigations with adequate positioning accuracy. Consequently, this system exhibits certain feasibility for the treatment of breast fibroadenomas.

Comparison of the treatment efficacies of HIFU, HIFU combined with GnRH-a, and HIFU combined with GnRH-a and LNG-IUS for adenomyosis: A systematic review and meta-analysis

To compare the treatment efficacies of high-intensity focused ultrasound (HIFU), HIFU combined with gonadotrophin-releasing hormone agonist (GnRH-a), and HIFU combined with GnRH-a and levonorgestrel-releasing intrauterine system (LNG-IUS) for adenomyosis. We conducted a literature search in SCIENCE DIRECT, COCHRANE LIBRARY, WILLEY ONLINE LIBRARY, PUBMED, and TAYLOR FRANCIS. A total of 471 articles identified, 12 were included in a systematic review, and 11 of them deemed quantitively eligible included in the meta-analysis. The efficacies of the three treatment regimens were assessed using the dysmenorrhea and menstrual scores at 3, 6, 12, 24 months. Of the three regimens, HIFU combined with GnRH-a and LNG-IUS provides the best outcome. On dysmenorrhea score at 6 months there was significantly different higher heterogeneity with P < 0.00001 (I² = 100% WMD 21.44 [6.34, 36.53]) with statistical significance P = 0.005. At 12 months there was significantly different higher heterogeneity P < 0.00001 (I² = 100% WMD 23.47 [6.00, 40.94]) with statistically significant P < 0.008. At 24 months there was significantly different higher heterogeneity P < 0.0005 (I² = 92% WMD 6.05 [4.81, 7.30]) with statistical significance P < 0.00001. HIFU combined with GnRH-a and LNG-IUS on menstrual score at 3 months was significantly different higher heterogeneity with P < 0.00001 (I² = 100% WMD 56.23 [16.01, 96.45]) with statistical significance P = 0.006. At 6 months there was significantly different higher heterogeneity P < 0.00001 (I² = 99% WMD 93.86 [64.15, 123.57]) with statistical significance P < 0.00001. At 12 months there was significantly different higher heterogeneity P < 0.00001 (I² = 99% WMD 97.13 [67.81, 126.46]) with statistical significance P < 0.00001 compared to treatments with only HIFU and HIFU combined with GnRH-a. HIFU combined with GnRH-a and LNG-IUS treatment is more effective than only HIFU monotherapy and HIFU combined with GnRH-a.

Liver Ultrasound Histotripsy: Novel Analysis of the Histotripsy Site Cell Constituents with Implications for Histotripsy Application in Cell Transplantation and Cancer Therapy

Introduction: Allogenic hepatocyte transplantation is an attractive alternative to whole-organ transplantation, particularly for the treatment of metabolic disorders and acute liver failure. However, the shortage of human donor organs for cell isolation, the low cell yield from decellularisation regimes, and low engraftment rates from portal administration of donor cells have restricted its clinical application. Using ultrasound histotripsy to provide a nidus in the liver for direct cell transplantation offers a new approach to overcoming key limitations in current cell therapy. We have analysed the liver cavity constituents to assess their potential as a site for cell delivery and implantation. Methods: Using human organ retrieval techniques, pig livers were collected from the abattoir and transported in ice-cold storage to the laboratory. Following 2 h of cold storage, the livers were flushed with organ preservation solution and placed on an organ perfusion circuit to maintain viability. Organs were perfused with Soltran™ organ preservation solution via the portal vein at a temperature of 24-30 °C. The perfusion circuit was oxygenated through equilibration with room air. Perfused livers (n=5) were subjected to ultrasound histotripsy, producing a total of 130 lesions. Lesions were generated by applying 50 pulses at 1 Hz pulse repetition frequency and 1% duty cycle using a single element 2 MHz bowl-shaped transducer (Sonic Concepts, H-148). Following histotripsy, a focal liver lesion was produced, which had a liquid centre. The fluid from each lesion was aspirated and cultured in medium (RPMI) at 37 °C in an incubator. Cell cultures were analysed at 1 and 7 days for cell viability and a live-dead assay was performed. The histotripsy sites were excised following aspiration and H&E staining was used to characterise the liver lesions. Cell morphology was determined by histology. Results: Histotripsy created a subcapsular lesion (~5 mm below the liver capsule; size ranging from 3 to 5 mm), which contained a suspension of cells. On average, 61×10⁴ cells per mL were isolated. Hepatocytes were present in the aspirate, were viable at 24 h post isolation and remained viable in culture for up to 1 week, as determined by phalloidin/DAPI cell viability stains. Cultures up to 21 days revealed metabolically active live hepatocyte. Live-dead assays confirmed hepatocyte viability at 1 week (Day 1: 12% to Day 7: 45% live cells; p < 0.0001), which retained metabolic activity and morphology, confirmed on assay and microscopy. Cell Titre-Glo^TM showed a peak metabolic activity at 1 week (average luminescence 24.6 RLU; p < 0.0001) post-culture compared with the control (culture medium alone), reduced to 1/3 of peak level (7.85 RLU) by day 21. Conclusions: Histotripsy of the liver allows isolation and culture of hepatocytes with a high rate of viability after 1 week in culture. Reproducing these findings using human livers may lead to wide clinical applications in cell therapy.

A Systematic Review of the Efficacy of Microfocused Ultrasound for Facial Skin Tightening

Objective: to systematically review the efficacy of microfocused ultrasound (MFU) for facial skin tightening. Methods: A systematic search was performed (Pubmed, Embase) to assess the efficacy of single MFU treatments for facial skin tightening. Eligible studies included randomised controlled trials, controlled trials, cohort studies and case series (n ≥ 10). Objective and subjective outcomes were assessed. Results: A total of 693 studies were identified of which 16 studies were eligible. All the studies involved female patients. MFU is capable of tightening the skin, as observed in studies measuring the results of brow lifts (0.47−1.7 mm) and submental lifts (measured as a 26−45 mm2 reduction in the submental area on lateral photographs). Data from the Global Aesthetic Improvement Scale (GAIS) were pooled, and the day 90 pooled subjective investigator reported scores (IGAIS) (n = 337) showed that 92% of the patients demonstrated an improvement in skin tightening and/or in wrinkle reduction which continued up to one year. Longer-term follow-up data are not available. The patient-reported pooled scores (SGAIS) (n = 81) showed that the skin improvements were mild and continued to increase from 42% (90 days) to 53% (360 days) post-treatment. The MFU treatment was moderately painful and caused transient erythema with or without oedema. Other adverse effects were rare (2%), including dysesthesia (numbness or hypersensitivity), bruising and stinging, mandibular burns, striations and contact dermatitis. Various device settings, treatment protocols and energies were applied. Excessive skin laxity and a BMI > 30 were posed as relative contraindications for MFU treatment because positive results declined with an increase in laxity and BMI. Conclusions: MFU treatment is effective in tightening female patients’ mildly to moderately lax facial skin. Future studies should focus on objective treatment outcomes, optimising treatment regimens and male patients.

HIFU as an alternative modality for patients with uterine fibroids who require fertility-sparing treatment

OBJECTIVES

To compare pregnancy outcomes after high-intensity focused ultrasound ablation (HIFU), myomectomy and uterine artery embolization (UAE) for fertility-sparing patients with uterine fibroids and to investigate the possible mechanism of improving pregnancy by HIFU.

MATERIALS AND METHODS

A meta-analysis of 54 studies containing 12,367 patients was conducted to compare the pregnancy outcomes of three fertility-sparing therapies. And a retrospective self-control study of 26 patients with uterine fibroids from May 2019 to December 2020 was performed to assess the blood flow impedance of bilateral uterine arteries before and after HIFU.

RESULTS

In the analysis by treatment option, the pregnancy rate after myomectomy was 0.43 (95% CI 0.36-0.49), which was higher than 0.18 (95% CI 0.10-0.26) after HIFU, the latter was significantly higher than that after UAE (ratio 0.08, 95% CI 0.06-0.10). The miscarriage rate after HIFU was 0.08 (95% CI 0.04-0.12), which was similar to 0.15 (95% CI 0.09-0.21) after myomectomy and also similar to 0.16 after UAE (95% CI 0.01-0.30). In the subgroup analysis, women who received ultrasound guided HIFU (USgHIFU) were more likely to have ideal pregnancy outcomes than that after magnetic resonance imaging-guided HIFU. The pulsatility index and resistance index on the right side were significantly higher 3 months after HIFU than before (1.637 ± 0.435 vs. 1.845 ± 0.469; p = 0.033; 0.729 ± 0.141 vs. 0.784 ± 0.081, p = 0.039).

CONCLUSIONS

HIFU, especially USgHIFU, may be an alternative fertility-sparing modality for patients with uterine fibroids over 40 years old. HIFU may contribute to improving pregnancy rates by elevating uterine blood flow impedance.

High intensity focused ultrasound atomization and erosion in healthy and tendinopathic tendons

Objective.High-intensity focused ultrasound (HIFU) can induce thermal and mechanical mechanisms in a well-defined focal volume of tissues. Histotripsy is a form of mechanical HIFU that can initiate and interact with bubble(s) to cause shock scattering and perhaps atomization within the bubble(s) to fractionate most soft tissues. Ultrasonic atomization, or the ejection of fine droplets from an acoustically-excited liquid exposed to air, has been shown to erode planar soft tissue surfaces, which has led to theories that atomization is a mechanism in histotripsy. However, healthy tendons show resistance to conventional histotripsy; pre-treatment of tendons with heat increases susceptibility to histotripsy fractionation. This study investigates ultrasonic atomization and erosion from planar healthy and tendinopathic tendon surfaces as we evaluate HIFU parameters for histotripsy in tendons.Approach.Forty-sixex vivobovine tendon-air interfaces were pre-conditioned to surface wetting, heat baths of 20 °C (unaltered), 37 °C (body temperature), and 58 °C (collagen degradation), collagenase soaks for 1, 3, 5, and 24 h (mimicking tendinopathic tendons), and phosphate buffered saline soaks for 24 h. Ejected fragments, histology, and gross analysis determined erosion success. Tissue displacement from the HIFU radiation force was monitored with high-speed photography, and tissue relaxation was pixel-tracked and fit to a Kelvin-Voigt model to evaluate changes in viscoelastic properties.Main results.Results showed that atomization produced holes in 24 h collagenase tendons and surface pitting in 58 °C, 3 h, and 5 h collagenase tendons. Increased mound heights and viscoelastic constants in pre-heated (to 58 °C) and collagenase-soaking (3+ hours) tendinopathic models caused a decrease in elasticity and/or increase in viscosity, increasing susceptibility to erosion by HIFU atomization.Significance.Therefore, tendons with chronic tendinopathies may be more susceptible than healthy tendons to histotripsy fractionation.

Magnetic resonance imaging-guided ultrasound ablation for prostate cancer - A contemporary review of performance

Prostate cancer (PCa) is one of the most common malignancies in men, but patient outcomes are varied depending on extent of disease. Radical, whole-gland therapies, such as prostatectomy or radiotherapy, are definitive treatments for PCa, but they are associated with significant morbidity, including erectile dysfunction and urinary incontinence. Focal therapies for PCa, whereby the part of gland harboring disease is selectively treated, spares the normal surrounding structures, and minimizes the morbidity associated with whole gland treatment. The use of magnetic resonance imaging (MRI) guidance provides advantages over ultrasound guidance, such as better localization and targeting of clinically significant PCa (csPCa), as well as MRI thermometry which optimizes tissue ablation temperatures. This review will discuss two MRI-guided high-intensity focused ultrasound (HIFU) techniques - transrectal MR-guided focused ultrasound (MRgFUS) and TULSA (transurethral ultrasound ablation) ablation for localized PCa. Overall, recent major trials for MRgFUS and TULSA have shown promising oncological and functional results in the treatment of low- to intermediate-risk PCa. Recent Phase II MRgFUS trials have shown better oncologic outcomes than the published results for focal ultrasound guided HIFU and may justify the additional costs associated with MRI guidance. While initial studies on TULSA have focused on subtotal gland ablation, recent trials assessing oncological outcomes for focal treatment of angular sectors have shown promise.

Banoxantrone Coordinated Metal-Organic Framework for Photoacoustic Imaging-Guided High Intensity Focused Ultrasound Therapy

Photoacoustic (PA) imaging with high spatial resolution has great potential as desired monitoring means in the high-intensity focused ultrasound (HIFU) surgery of tumor. However, its penetration depth in the tissue is insufficient for achieving accurate intraoperative navigation, leading to residual tumor tissue. Nanomedicine provides a new opportunity for PA imaging to guide HIFU surgery. Studies have found that the hypoxic heterogeneity of tumor is effectively reversed by HIFU. Herein, a specific metal-organic framework nanosystem, constructed by coordination of banoxantrone (AQ4N) and Mn²⁺ , is designed based on HIFU to reverse the hypoxic heterogeneity of tumors. It can provide exogenous light-absorbing substances, thus improving the penetrability of PA imaging signal through the deep tissue and achieving clearer PA imaging for guiding HIFU surgery. In turn, AQ4N, in the hypoxic homogenous environment of the tumor provided by HIFU, is activated sequentially to specifically treat the residual hypoxic tumor cells. This combination treatment manifests higher tumor suppressors activation and lower expression of genes related to tumor progression. This strategy addresses the dissatisfaction with PA imaging-guided HIFU therapy and is promising for translation into a clinical combination regimen.

Italian Guidelines for the Management of Non-Functioning Benign and Locally Symptomatic Thyroid Nodules

AIM

This guideline (GL) is aimed at providing a reference for the management of non-functioning, benign thyroid nodules causing local symptoms in adults outside of pregnancy.

METHODS

This GL has been developed following the methods described in the Manual of the National Guideline System. For each question, the panel appointed by Associazione Medici Endocrinology (AME) identified potentially relevant outcomes, which were then rated for their impact on therapeutic choices. Only outcomes classified as "critical" and "important" were considered in the systematic review of evidence and only those classified as "critical" were considered in the formulation of recommendations.

RESULTS

The present GL contains recommendations about the respective roles of surgery and minimally invasive treatments for the management of benign symptomatic thyroid nodules. We suggest hemithyroidectomy plus isthmectomy as the first-choice surgical treatment, provided that clinically significant disease is not present in the contralateral thyroid lobe. Total thyroidectomy should be considered for patients with clinically significant disease in the contralateral thyroid lobe. We suggest considering thermo-ablation as an alternative option to surgery for patients with a symptomatic, solid, benign, single, or dominant thyroid nodule. These recommendations apply to outpatients, either in primary care or when referred to specialists.

CONCLUSION

The present GL is directed to endocrinologists, surgeons, and interventional radiologists working in hospitals, in territorial services, or private practice, general practitioners, and patients. The available data suggest that the implementation of this GL recommendations will result in the progressive reduction of surgical procedures for benign thyroid nodular disease, with a decreased number of admissions to surgical departments for non-malignant conditions and more rapid access to patients with thyroid cancer. Importantly, a reduction of indirect costs due to long-term replacement therapy and the management of surgical complications may also be speculated.

Treating methicillin-resistant Staphylococcus aureus (MRSA) bone infection with focused ultrasound combined thermally sensitive liposomes

OBJECTIVE

Chronic bone infection caused by Staphylococcus aureus biofilms in children and adults is characterized by reduced antibiotic sensitivity. In this study, we assessed 'heat-targeted, on-demand' antibiotic delivery for S. aureus killing by combining ciprofloxacin (CIP)-laden low-temperature sensitive liposomes (LTSLs) with local high-intensity focused ultrasound (HIFU) induced bone heating in a rat model of bone infection.

METHODS

CIP-LTSLs were prepared using the thin-film hydration and extrusion method. Bone infection was established by surgically implanting an orthopedic K-wire colonized with methicillin-resistant S. aureus (MRSA) strain into rat's femurs. For bone heating, ultrasound-guided HIFU exposures were performed to achieve a local temperature of 40-42 °C (∼15 min) concurrently with intravenous injection of CIP-LTSLs or CIP. CIP biodistribution was determined spectrophotometrically and therapeutic efficacy was determined by bacteriological, histological and scanning electron microscopy (SEM) analyses.

RESULTS

CIP-LTSLs in the range of 183.5 nm ± 1.91 showed an encapsulation efficiency of >70% at 37 °C and a complete release at ∼42 °C. The metal implantation method yielded medullary osteomyelitis characterized by suppurative changes (bacterial and pus pockets) by day 10 in bones and adjoining muscle tissues. HIFU heating significantly improved CIP delivery from LTSLs in bones, resulting in a significant reduction in MRSA load compared to HIFU and CIP alone groups. These were also verified by histology and SEM, wherein a distinct reduction in S. aureus population in the infected metal wires and tissues from the combinatorial therapy was noted.

CONCLUSION

HIFU improved CIP delivery to bones, achieving clearance of hard-to-treat MRSA biofilms.

Successful pregnancies in women with diffuse uterine leiomyomatosis after high-intensity focused ultrasound ablation: report of three cases

OBJECTIVE

To describe the reproductive outcomes of patients with diffuse uterine leiomyomatosis (DUL) treated with high-intensity focused ultrasound (HIFU) ablation.

MATERIALS AND METHODS

Three patients of reproductive age with DUL who underwent HIFU treatment were enrolled, all of whom had a strong desire to become pregnant. All patients underwent routine laboratory tests, electrocardiography (ECG), chest X-ray radiography, ultrasound, and magnetic resonance imaging (MRI) examinations after routine medical history collection and physical examination. The treatment time, treatment power, sonication time, and adverse events were recorded. One day after HIFU, MRI was performed to evaluate treatment efficacy. The patients were scheduled for follow-up at 3-, 6-, 12-, and 24-month after HIFU treatment.

RESULTS

All the three patients completed HIFU treatment successfully without any major complication. Uterine size and menstrual volume significantly decreased with the combination of medical and HIFU treatments. The shrinkage rate of uterine volume was 31-44% and the menstrual volume reduced by 1/2 or returned to normal at 3 months post-HIFU. Three patients had successful conceptions between 3 and 11 months after HIFU with healthy deliveries. No uterine rupture occurred during pregnancy and delivery.

CONCLUSION

HIFU ablation may help achieve a successful pregnancy in patients with DUL.

Erratum: Perfluorocarbon emulsion enhances MR-ARFI displacement and temperature in vitro: Evaluating the response with MRI, NMR, and hydrophone

[This corrects the article DOI: 10.3389/fonc.2022.1025481.].

A radiomics nomogram model for predicting prognosis of pancreatic ductal adenocarcinoma after high-intensity focused ultrasound surgery

OBJECTIVE

To develop and validate a radiomics nomogram for predicting the survival of patients with pancreatic ductal adenocarcinoma (PDAC) after receiving high-intensity focused ultrasound (HIFU) treatment.

METHODS

A total of 52 patients with PDAC were enrolled. To select features, the least absolute shrinkage and selection operator algorithm were applied, and the radiomics score (Rad-Score) was obtained. Radiomics model, clinics model, and radiomics nomogram model were constructed by multivariate regression analysis. The identification, calibration, and clinical application of nomogram were evaluated. Survival analysis was performed using Kaplan-Meier (K-M) method.

RESULTS

According to conclusions made from the multivariate Cox model, Rad-Score, and tumor size were independent risk factors for OS. Compared with the clinical model and radiomics model, the combination of Rad-Score and clinicopathological factors could better predict the survival of patients. Patients were divided into high-risk and low-risk groups according to Rad-Score. K-M analysis showed that the difference between the two groups was statistically significant (p < 0.05). In addition, the radiomics nomogram model indicated better discrimination, calibration, and clinical practicability in training and validation cohorts.

CONCLUSION

The radiomics nomogram effectively evaluates the prognosis of patients with advanced pancreatic cancer after HIFU surgery, which could potentially improve treatment strategies and promote individualized treatment of advanced pancreatic cancer.

High Intensity Focused Ultrasound for Treatment of Bone Malignancies-20 Years of History

High Intensity Focused Ultrasound (HIFU) is the only non-invasive method for percutaneous thermal ablation of tissue, with treatments typically performed either under magnetic resonance imaging or ultrasound guidance. Since this method allows efficient heating of bony structures, it has found not only early use in treatment of bone pain, but also in local treatment of malignant bone tumors. This review of 20 years of published studies shows that HIFU is a very efficient method for rapid pain relief, can provide local tumor control and has a very patient-friendly safety profile.

Letrozole as premedication of high intensity focused ultrasound treatment of uterine fibroids: A retrospective observation study

Background

No reports on Letrozole as a pretreatment before ablation of uterine fibroid with high intensity focused ultrasound (HIFU), so a retrospective observation study was performed to evaluate the response of different pre-HIFU medication.

Methods

We collected patients with single uterine fibroid receiving HIFU ablation from January 2018 to April 2021. All enrolled patients were classified into three group: group A (no pre-HIFU medication use), group B (Pre-HIFU letrozole use), group C (pre-HIFU gonadotrophin releasing hormone analog, GnRHa). Further associated clinical data and treatment response after HIFU treatment were reviewed and evaluated.

Results

A total of 39 patients including 21, 7, and 11 in group A, B, and C were collected respectively. After pre-HIFU medication, no difference of fibroid volume was found (A: 251.4, B: 360.6, C: 409.4 cm³, p = 0.250), and GnRHa group had significantly larger volume reduction than Letrozole users (38.6% vs. 16.4%, p = 0.007). The incidence of hypoestrogenic symptoms was higher in GnRHa group than in letrozole users (27.3% vs. 0, p = 0.170). GnRHa group had more sonication time (p = 0.001), treatment duration (p = 0.002), and ablated energy (p = 0.001) than group A and B. The treatment efficiency was higher in letrozole group than that in other 2 groups (4.52 vs. 2.39 vs. 2.34 cm³/min, p = 0.050). For patients with fibroid over 10 cm in diameter, letrozole group had even better energy efficiency (p = 0.067), treatment speed (p = 0.007), treatment efficiency (p = 0.001), NPV per energy (p = 0.005), and NPV per sonication (p = 0.004) than other 2 groups.

Conclusion

Letrozole as a pretreatment medication before HIFU treatment might increase the energy efficiency and treatment efficiency of its ablation of uterine leiomyoma, especially for fibroid over 10 cm. Future study of larger patient number is needed to confirm our results.

Experimental evaluation of high intensity focused ultrasound for fat reduction of ex vivo porcine adipose tissue

PURPOSE

The present study was stimulated by the continuous growth of commercially available high intensity focused ultrasound (HIFU) systems for fat reduction. Herein, HIFU was utilised for fat ablation using a single-element ultrasonic transducer operating in thermal mode.

METHODS

The custom-made concave transducer that operates at 1.1 MHz was assessed on excised porcine adipose tissue for its ability to reduce fat. Ultrasonic sonications were executed on the adipose tissue utilising acoustical power between 14 and 75 W and sonication time in the range of 1-10 min. The mass of the adipose tissue sample was weighed afore and after ultrasonic sonications and the effect of the sonication on the mass change was recorded.

RESULTS

Mass change was linearly dependent with either increasing acoustical power or sonication time and was in the range of 0.46-1.9 g. High acoustical power of 62.5 W for a sonication time of 1 min and a power of 75 W for a sonication time of 5 min, respectively resulted in the formation of a lesion or possible cavitation on the piece of excised adipose tissue.

CONCLUSION

The study demonstrated the efficacy of the proposed transducer in achieving a reduction of excised fat tissue. The present findings indicate the potential use of the transducer in a HIFU system indicated for the reduction of subcutaneous adipose tissue where increased values of acoustical power can result in increased amounts of fat reduction.