The potential role of dynamic MRI in assessing the effectiveness of high-intensity focused ultrasound ablation of breast cancer

MR Imaging-Guided Focused Ultrasound for Breast Tumors

Breast tumors remain a complex and prevalent health burden impacting millions of individuals worldwide. Challenges in treatment arise from the invasive nature of traditional surgery and, in malignancies, the complexity of treating metastatic disease. The development of noninvasive treatment alternatives is critical for improving patient outcomes and quality of life. This review aims to explore the advancements and applications of focused ultrasound (FUS) technology over the past 2 decades. FUS offers a promising noninvasive, nonionizing intervention strategy in breast tumors including primary breast cancer, fibroadenomas, and metastatic breast cancer.

Five-year follow-up after a single US-guided high intensity focused ultrasound treatment of breast fibroadenoma

The aim of this study was to evaluate the long-term efficacy of a single ultrasound-guided high-intensity focused ultrasound (US-HIFU) treatment in patients with breast fibroadenoma (FA) in terms of volume and pain reduction as well as palpation findings. From december 2013 until november 2014 27 women with a symptomatic FA were treated in one HIFU-session. Follow-up visits were performed after 7 days, 6 months and 1, 2, 3 and 5 years with clinical examination and ultrasound. One year after the procedure, a core needle biopsy of the residual lesion was offered. There was a significant volume reduction 6 months after HIFU from 1083.10 to 347.13 mm3 (p < 0.0001) with a mean volume reduction ratio (VRR) of 61.63%. Thereafter the FAs showed a further, but no longer significant decrease in size. One patient with an initial incomplete ablation and histologically confirmed persistent vital cells after 1 year showed a strong regrowth after 3 years. Excluding this patient from analysis, the mean VRR at months 12, 24, 36, and 60 was 86.44%, 94.44%, 94.90%, and 97.85%, respectively. Before HIFU, 59.26% of the patients had pain (22.33/100 VAS) which decreased to 6.56/100 after 12 months and remained reduced over the 5 year follow up period. A decrease in palpability from 85.19 to 7.69% was observed within 24 months. A single HIFU intervention let to a substantial reduction in size, pain, and palpability with its most potential effect during the first 12 months. Subsequently, the observed effect remained stable over a 5 year follow up period. Incomplete initial treatment was associated with the risk of regrowth.

Tissue Ablation: Applications and Perspectives

Tissue ablation techniques have emerged as a critical component of modern medical practice and biomedical research, offering versatile solutions for treating various diseases and disorders. Percutaneous ablation is minimally invasive and offers numerous advantages over traditional surgery, such as shorter recovery times, reduced hospital stays, and decreased healthcare costs. Intra-procedural imaging during ablation also allows precise visualization of the treated tissue while minimizing injury to the surrounding normal tissues, reducing the risk of complications. Here, the mechanisms of tissue ablation and innovative energy delivery systems are explored, highlighting recent advancements that have reshaped the landscape of clinical practice. Current clinical challenges related to tissue ablation are also discussed, underlining unmet clinical needs for more advanced material-based approaches to improve the delivery of energy and pharmacology-based therapeutics.

An in vitro and in vivo study on extracorporeal transducer optimization for high-intensity focused ultrasound to improve the safety and efficacy of breast tumor ablation

OBJECTIVE

To observe the characteristics of a new extracorporeal high intensity focused ultrasound transducer, titled Haifu system JCQ-B, and to compare its safety and efficacy for breast ablation with the standard Haifu system JC transducer.

MATERIALS AND METHODS

Ox liver with pig skin and pork ribs were prepared in a semi-sphere shape, served as in vitro acoustic model. The udders of female goats were used as in vivo acoustic model. Both in vitro and in vivo models were ablated by either JCQ-B or JC transducer. The morphology of biological focal region (BFR), the coagulative necrosis volume, and the temperature increase were observed and compared.

RESULTS

The BFR morphology of JCQ-B transducer was circular both in vitro and in vivo, with a length-width ratio close to one. Under the same sonication parameters (sonication power, time and depth in tissue), coagulation necrosis volume caused by JCQ-B transducer was larger than that caused by JC transducer both in vitro and in vivo. The increase in temperature in the near and far acoustic pathways with JCQ-B transducer was significantly lower than that of JC transducer in vitro. After receiving high sonication energy during in vivo experimentation, there were no complications observed after the ablation of JCQ-B transducer, while small skin damage was observed after the ablation of JC transducer.

CONCLUSIONS

The JCQ-B transducer improved the safety and efficacy of treatment by optimizing BFR morphology and ablation efficiency, which could be applied in the treatment of breast tumor.

The Role of High Intensity Focused Ultrasound in the Treatment of Fibroadenomas: A Systematic Review

Introduction

Fibroadenomas are solid, mobile, and non-tender benign breast lumps, with highest prevalence amongst young women aged between 15 and 35. Symptoms can include discomfort, and they can become problematic, particularly when they enlarge, resulting in many referrals for biopsies, with fibroadenomas accounting for 30-75% of the cases. Diagnosis is based on triple assessment that involves a clinical examination, ultrasound imaging, and mammography, as well as core needle biopsies. Current management includes observation for 6-12 months, with the indication of definitive surgery, in cases that are older than 35 years or with fibroadenoma persistence. Serious adverse effects of surgery might include nipple areolar distortion, scarring, and damage to the breast tissue, as well as the risks associated with surgery and anesthesia, making it a non-feasible option.

Methods

A literature search was performed on the databases Embase, MEDLINE/PubMed, Google Scholar, and Ovid for English language papers published between January 1, 2000, and March 17, 2021. A structured protocol was employed to devise a comprehensive search strategy with keywords and Boolean operators defined by the research question. The keywords used for the search were "HIFU", "High Intensity Focused Ultrasound," "Fibroadenoma," "Breast," "Lesion." This review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

Results

Recently, a thermal ablative technique, high intensity focused ultrasound (HIFU), was found to be a safe, noninvasive, and technically successful alternative, having displayed promising outcomes in reducing the volume of fibroadenomas, pain experienced by patients, and the length of hospitalization. Quality of life improvement was also evidenced, exhibited by the disappearance of symptoms, and enhanced physical activity post-intervention, in addition to patients' satisfaction with the cosmetic results and future recommendation of the procedure to other patients.

Conclusion

Overall, HIFU is a well-tolerated treatment associated, with low risk of complications, that can potentially include erythema, skin discoloration, and bruising with the majority of these self-resolving shortly after the procedure.

Percutaneous Management of Breast Cancer: a Systematic Review

PURPOSE OF REVIEW

Surgical treatment of breast cancer is becoming increasingly more minimally invasive. We review the development status of percutaneous management for primary breast cancer and the evidence relating to tumor size as a fundamental determinant of treatment clinical outcome.

RECENT FINDINGS

It is safe and feasible for percutaneous management to treat breast cancer. For tumor size ≤ 2 cm, percutaneous management is a promising alternative modality. For tumor size ≤ 3 cm, it is controversial whether percutaneous management can achieve similar effects to surgery, especially its long-term effects. For tumor size > 3 cm, it is still in the initial exploration stage and showed the potential in the treatment of unresectable cancer by benefitting the local control of primary cancer. Percutaneous management of breast cancer is a valuable method for breast cancer treatment in selected patients. However, it will be necessary to provide the high level of evidence for widespread clinical application.

Medical Device Advances in the Treatment of Glioblastoma

Despite decades of research and the growing emergence of new treatment modalities, Glioblastoma (GBM) frustratingly remains an incurable brain cancer with largely stagnant 5-year survival outcomes of around 5%. Historically, a significant challenge has been the effective delivery of anti-cancer treatment. This review aims to summarize key innovations in the field of medical devices, developed either to improve the delivery of existing treatments, for example that of chemo-radiotherapy, or provide novel treatments using devices, such as sonodynamic therapy, thermotherapy and electric field therapy. It will highlight current as well as emerging device technologies, non-invasive versus invasive approaches, and by doing so provide a detailed summary of evidence from clinical studies and trials undertaken to date. Potential limitations and current challenges are discussed whilst also highlighting the exciting potential of this developing field. It is hoped that this review will serve as a useful primer for clinicians, scientists, and engineers in the field, united by a shared goal to translate medical device innovations to help improve treatment outcomes for patients with this devastating disease.

New Perspectives for Eye-Sparing Treatment Strategies in Primary Uveal Melanoma

Simple Summary

Uveal melanoma is the most common intraocular cancer. The current eye-sparing treatment options include mostly plaque brachytherapy. However, the effectiveness of these methods is still unsatisfactory. In this article, we review several possible new treatment options. These methods may be based on the physical destruction of the cancerous cells by applying ultrasounds. Another approach may be based on improving the penetration of the anti-cancer agents. It seems that the most promising technologies from this group are based on enhancing drug delivery by applying electric current. Finally, new advanced nanoparticles are developed to combine diagnostic imaging and therapy (i.e., theranostics). However, these methods are mostly at an early stage of development. More advanced studies on experimental animals and clinical trials would be needed to introduce some of these techniques to routine clinical practice.

Abstract

Uveal melanoma is the most common intraocular malignancy and arises from melanocytes in the choroid, ciliary body, or iris. The current eye-sparing treatment options include surgical treatment, plaque brachytherapy, proton beam radiotherapy, stereotactic photon radiotherapy, or photodynamic therapy. However, the efficacy of these methods is still unsatisfactory. This article reviews several possible new treatment options and their potential advantages in treating localized uveal melanoma. These methods may be based on the physical destruction of the cancerous cells by applying ultrasounds. Two examples of such an approach are High-Intensity Focused Ultrasound (HIFU)—a promising technology of thermal destruction of solid tumors located deep under the skin and sonodynamic therapy (SDT) that induces reactive oxygen species. Another approach may be based on improving the penetration of anti-cancer agents into UM cells. The most promising technologies from this group are based on enhancing drug delivery by applying electric current. One such approach is called transcorneal iontophoresis and has already been shown to increase the local concentration of several different therapeutics. Another technique, electrically enhanced chemotherapy, may promote drug delivery from the intercellular space to cells. Finally, new advanced nanoparticles are developed to combine diagnostic imaging and therapy (i.e., theranostics). However, these methods are mostly at an early stage of development. More advanced and targeted preclinical studies and clinical trials would be needed to introduce some of these techniques to routine clinical practice.

Development of a noninvasive HIFU treatment for breast adenocarcinomas using a toroidal transducer based on preliminary attenuation measurements

Breast cancer is the most commonly diagnosed type of cancer among women. For the last fifteen years, treatments that are less invasive than lumpectomy, such as high-intensity focused ultrasound (HIFU) therapy, have been developed, with encouraging results. In this study, a toroidal HIFU transducer was used to create lesions of at least 2 cm in diameter within less than one minute of treatment. The toroidal HIFU transducer created two focal zones that led to large, fast and homogeneous ablations (10.5 cc/min). The experiments were conducted in 30 human samples of normal breast tissues recovered from mastectomies to measure acoustic attenuation (N = 30), and then, HIFU lesions were created (N = 15). Eight HIFU ablations were performed to evaluate the reproducibility of the lesions. HIFU lesions were created in 45 s with a toroidal HIFU transducer working at 2.5 MHz. The longest and shortest axes of the HIFU lesions were 21.7 ± 3.1 mm and 23.5 ± 3.3 mm respectively, corresponding to an average volume of 7.3 ± 1.4 cm³. These HIFU lesions were performed at an average depth of 19.0 ± 1.5 mm, while the integrity of the skin was preserved. The HIFU-treated breast tissues had a higher level of attenuation (0.57 ± 0.11 Np.cm^-1.MHz^-1) when compared to the untreated tissues (0.21 ± 0.04 Np.cm^-1.MHz^-1). This study shows the feasibility of a fast and fully noninvasive treatment using a toroidal transducer for breast tumors measuring up to 15 mm in diameter.

Image-guided Microinvasive Percutaneous Treatment of Breast Lesions: Where Do We Stand?

Treatment of breast lesions has evolved toward the use of less-invasive or minimally invasive techniques. Minimally invasive treatments destroy focal groups of cells without surgery; hence, less anesthesia is required, better cosmetic outcomes are achieved because of minimal (if any) scarring, and recovery times are shorter. These techniques include cryoablation, radiofrequency ablation, microwave ablation, high-intensity focused US, laser therapy, vacuum-assisted excision, and irreversible electroporation. Each modality involves the use of different mechanisms and requires specific considerations for application. To date, only cryoablation and vacuum-assisted excision have received U.S. Food and Drug Administration approval for treatment of fibroadenomas and have been implemented as part of the treatment algorithm by the American Society of Breast Surgeons. Several clinical studies on this topic have been performed on outcomes in patients with breast cancer who were treated with these techniques. The results are promising, with more data for radiofrequency ablation and cryoablation available than for other minimally invasive methods for treatment of early-stage breast cancer. Clinical decisions should be made on a case-by-case basis, according to the availability of the technique. MRI is the most effective imaging modality for postprocedural follow-up, with the pattern of enhancement differentiating residual or recurrent disease from postprocedural changes. ^©RSNA, 2021.

Applications of High-Intensity Focused Ultrasound in the Treatment of Different Pathologies

Objective:

The purpose of this literature search was to review the benefits of high-intensity focused ultrasound (HIFU) and its application for different pathologies.

Methods:

This review summarizes the implementation of HIFU for different pathologic conditions. An National Center for Biotechnology Information, PubMed, MEDLINE, Medscape, and Google Scholar database search (1992–2016) was done with the following keywords: high-intensity focused ultrasound; uses of HIFU; and applications of HIFU in the liver, bones, uterine fibroids, prostate, breast, thyroid, pancreas, kidneys, brain, urinary bladder, and so on. Tables and graphs were created for all the variables included in the study, and descriptive statistics were applied.

Results:

In total, 110 records were identified, through database search. In addition, 20 articles were identified through other sources. Screening of the articles was performed, and 20 were removed due to duplication; further screening was performed for 110 articles, and 30 records were further excluded. Full-text articles were assessed for eligibility and 30 were retained. Full-text articles were excluded (N = 36) on the basis that research was performed on animals, and this review article was performed solely for human application. There were 42 qualitative syntheses that researches added to the review. In addition, 42 quantitative synthesis (meta-analysis) were added to the review.

Conclusion:

The conclusion of this narrative review indicates that HIFU is noninvasive, nonharmful, and effective in treating diseases and tumors of the brain, breast, bone, hepatic, renal, pancreas, and prostate; uterine fibroids; and many other solid tumors. Recent technological development suggests that HIFU is likely to play a significant role in future surgical practices. Further research works should be conducted on a large sample size to obtain more accurate results in the application of HIFU.

The applicability and efficacy of magnetic resonance-guided high intensity focused ultrasound system in the treatment of primary trigeminal neuralgia

Primary trigeminal neuralgia is a common clinical refractory neuralgia characterized by an onset of excruciating pain that can severely affect patients' quality of life. Long-term suffering from this pain may lead to depression, anxiety, and suicide. Current treatments, however, are associated with high recurrent rates and severe complications. We hypothesize that both the applicability and efficacy of magnetic resonance-guided high intensity focused ultrasound (MR-HIFU) treatment in primary trigeminal neuralgia can be achieved under the following conditions: a specific target focus and incident channel, a temperature measurement system that does not incur damage to surrounding tissues, and an optimal radiation dose. Successful non-invasive treatment of primary trigeminal neuralgia by MR-HIFU systems could represent a breakthrough of this technology applied to the oral and maxillofacial region.

High-intensity focused ultrasound enhances the effect of bufalin by inducing apoptosis in pancreatic cancer cells

Purpose

High-intensity focused ultrasound (HIFU) has the potential to be an effective therapeutic strategy for pancreatic cancer (PC). However, owing to the high malignancy and poor prognosis of PC, the use of HIFU therapy alone is not sufficient to impair the progression of PC. Bufalin, a compound extracted from traditional medicine, is known to inhibit the growth and progression of PC cells. However, the effect of the combination therapy of HIFU plus bufalin (HIFU+bufalin) is still uncertain.

Materials and methods

A colony formation assay and flow cytometry were performed to measure the growth and induction of apoptosis in PC cells. Western blotting was used to explore the potential mechanism of HIFU and bufalin therapy. The in vivo efficacy of HIFU+bufalin was tested in a MiaPaCa₂ xenograft model.

Results

Bufalin inhibited the growth of PC cells more obviously compared to HIFU. Combining bufalin with HIFU further decreased the growth of MiaPaCa₂ cells compared with single therapy in vitro. Flow cytometry results showed that the percentage of surviving MiaPaCa₂ cells in the bufalin-treated group and the HIFU-treated group was approximately three-fold and two-fold higher than in the HIFU+bufalin-treated group. Contrasting results were found in Panc-1 cells. Biochemical analysis revealed that HIFU+bufalin treatment elevated PARP expression and increased caspase-8 activation in MiaPaCa₂ and Panc-1 cells. HIFU+bufalin significantly reduced the growth of MiaPaCa₂ tumors compared with HIFU or bufalin treatment alone. HIFU+bufalin treatment decreased Ki67 staining and increased activated caspase-3 and caspase 8 staining, when compared with HIFU or bufalin treatment alone in mouse tumors.

Conclusion

HIFU enhanced the effect of bufailn by inducing apoptosis in PC cells. A combination of HIFU and bufalin may be employed as an alternative therapeutic strategy for PC.

High-intensity focused ultrasound in the treatment of breast tumours

High-intensity focused ultrasound (HIFU) is a minimally invasive technique that has been used for the treatment of both benign and malignant tumours. With HIFU, an ultrasound (US) beam propagates through soft tissue as a high-frequency pressure wave. The US beam is focused at a small target volume, and due to the energy building up at this site, the temperature rises, causing coagulative necrosis and protein denaturation within a few seconds. HIFU is capable of providing a completely non-invasive treatment without causing damage to the directly adjacent tissues. HIFU can be either guided by US or magnetic resonance imaging (MRI). Guided imaging is used to plan the treatment, detect any movement during the treatment and monitor response in real-time. This review describes the history of HIFU, the HIFU technique, available devices and gives an overview of the published literature in the treatment of benign and malignant breast tumours with HIFU.

High-intensity focused ultrasound in the treatment of breast fibroadenomata (HIFU-F trial)

BACKGROUND

High-intensity focussed ultrasound (HIFU) is a non-invasive ablative technique utilising the application of high frequency ultrasound (US) pressure waves to cause tissue necrosis. This emerging technology is currently limited by prolonged treatment times. The aim of the HIFU-F trial was to perform circumferential HIFU treatment as a means of shortening treatment times.

METHODS

A prospective trial was set up to treat 50 consecutive patients ≥18 years of age. Eligible patients possessed symptomatic fibroadenomata, visible on US. Patients ≥25 years of age required histological confirmation of the diagnosis. Primary outcome measures were reduction in treatment time, reduction in volume on US after 12 months and complication rates.

RESULTS

HIFU treatment was performed in 51 patients (53 treatments) with a mean age of 29.8 years (SD 7.2 years) and a diameter of 2.6 cm (SD 1.4 cm). Circumferential ablation reduced treatment times by an estimated 19.9 min (SD 25.1 min), which is a 29.4% (SD 15.2%) reduction compared with whole lesion ablation. Volume reduction of 43.2% (SD 35.4%; p < 0.005, paired t-test) was observed on US at 12 months post-treatment. Local complications completely resolved at 1 month apart from skin hyper-pigmentation, which persisted in nine cases at three months, six cases at 6 months and six at 12 months.

CONCLUSION

Circumferential HIFU treatment for breast fibroadenomata is feasible to reduce both lesion size and treatment time. HIFU is a non-invasive alternative technique for the treatment of breast fibroadenomata. ISRCTN registration: 76622747.

The efficacy of a new high intensity focused ultrasound therapy for locally advanced pancreatic cancer

PURPOSE

To compare the survival benefit and safety of the low power cumulative and traditional high intensity focused ultrasound (HIFU) for locally advanced pancreatic cancer.

METHOD

We retrospectively analyzed 38 patients with locally advanced, inoperable, stage III pancreatic patients received HIFU treatment between January 2008 and April 2014 in the Department of Surgery, the Second Affiliated Hospital, Zhejiang University, School of Medicine. 11 of them received the low power cumulative HIFU treatment, while other 27 received the traditional HIFU treatment. The HIFU device used was the FEP-BY02 (Yuande Biomedical Engineering Co. Ltd, Beijing, China). Serum biochemistry and adverse events were assessed before and after treatment. All the patients were followed up until death. The survival rate and adverse events of two groups were compared.

RESULTS

In 38 patients, the baseline characteristics including gender, age, Karnofsky performance status (KPS) score, tumor location of two groups were generally well balanced (P > 0.05). The median overall survival (OS) for low power cumulative HIFU group was 10.3 months (95% CI, 6.3-14.3 months), which is significantly longer than traditional HIFU group with 6.0 months (95% CI, 5.2-6.8 months) (P = 0.018). In low power cumulative HIFU group, the 6-month and 12-month survival rates were higher than traditional group, 100% v.s 44.4%, 11.1% v.s 36.4%, respectively. The adverse events in both groups include abdominal pain, fever, C-reactive protein (CRP) elevated. The incidence was lower in low power cumulative HIFU group, however, without statistical significance.

CONCLUSION

The low power cumulative HIFU treatment showed a statistical significance in survival benefit with better safety profile compared to the traditional HIFU treatment in patients with locally advanced pancreatic cancer.

Minimally invasive ablative techniques in the treatment of breast cancer: a systematic review and meta-analysis

PURPOSE

Breast-conserving surgery is effective for breast cancer treatment but is associated with morbidity in particular high re-excision rates. We performed a systematic review and meta-analysis to assess the current evidence for clinical outcomes with minimally invasive ablative techniques in the non-surgical treatment of breast cancer.

METHODS

A systematic search of the literature was performed using PubMed and Medline library databases to identify all studies published between 1994 and May 2016. Studies were considered eligible for inclusion if they evaluated the role of ablative techniques in the treatment of breast cancer and included ten patients or more. Studies that failed to fulfil the inclusion criteria were excluded.

RESULTS

We identified 63 studies including 1608 patients whose breast tumours were treated with radiofrequency (RFA), high intensity focussed ultrasound (HIFU), cryo-, laser or microwave ablation. Fifty studies reported on the number of patients with complete ablation as found on histopathology and the highest rate of complete ablation was achieved with RFA (87.1%, 491/564) and microwave ablation (83.2%, 89/107). Short-term complications were most often reported with microwave ablation (14.6%, 21/144). Recurrence was reported in 24 patients (4.2%, 24/570) and most often with laser ablation (10.7%, 11/103). The shortest treatment times were observed with RFA (15.6 ± 5.6 min) and the longest with HIFU (101.5 ± 46.6 min).

CONCLUSION

Minimally invasive ablative techniques are able to successfully induce coagulative necrosis in breast cancer with a low side effect profile. Adequately powered and prospectively conducted cohort trials are required to confirm complete pathological ablation in all patients.

A review of ablative techniques in the treatment of breast fibroadenomata

Introduction

Breast fibroadenomata (FAD) are benign lesions which occur in about 10 % of all women. Diagnosis is made by triple assessment (physical examination, imaging and/or histopathology/cytology). For a definitive diagnosis of FAD, the treatment is conservative unless the patient is symptomatic. For symptomatic patients, the lumps can be surgically excised or removed interventionally by vacuum-assisted mammotomy (VAM). Ablative techniques like high-intensity focused ultrasound (HIFU), cryo-ablation and laser ablation have also been used for the treatment of FAD, providing a minimally invasive treatment without scarring or poor cosmesis. This review summarises current trials using minimally invasive ablative techniques in the treatment of breast FAD.

Methods

A comprehensive review of studies using minimally invasive ablative techniques was performed.

Results

There are currently several trials completed or recruiting patients using HIFU, cryo-ablation and laser ablation in the treatment of breast FAD. The results look very promising but cannot be compared at this point due to heterogeneity between studies.

Conclusion

Minimally invasive ablative techniques like HIFU, cryo-ablation and laser ablation are promising in the treatment of breast FAD. Future trials should be randomised and contain larger numbers of patients to determine the effectiveness of ablative techniques with more precision.

Surgical treatment of nonpalpable primary invasive and in situ breast cancer

Breast cancer is the most-common cancer among women worldwide, and over one-third of all cases diagnosed annually are nonpalpable at diagnosis. The increasingly widespread implementation of breast-screening programmes, combined with the use of advanced imaging modalities, such as magnetic resonance imaging (MRI), will further increase the numbers of patients diagnosed with this disease. The current standard management for nonpalpable breast cancer is localized surgical excision combined with axillary staging, using sentinel-lymph-node biopsy in the clinically and radiologically normal axilla. Wire-guided localization (WGL) during mammography is a method that was developed over 40 years ago to enable lesion localization preoperatively; this technique became the standard of care in the absence of a better alternative. Over the past 20 years, however, other technologies have been developed as alternatives to WGL in order to overcome the technical and outcome-related limitations of this technique. This Review discusses the techniques available for the surgical management of nonpalpable breast cancer; we describe their advantages and disadvantages, and highlight future directions for the development of new technologies.

Systematic review of high-intensity focused ultrasound ablation in the treatment of breast cancer

BACKGROUND

A systematic review was undertaken to assess the clinical efficacy of non-invasive high-intensity focused ultrasound (HIFU) ablation in the treatment of breast cancer.

METHODS

MEDLINE/PubMed library databases were used to identify all studies published up to December 2013 that evaluated the role of HIFU ablation in the treatment of breast cancer. Studies were eligible if they were performed on patients with breast cancer and objectively recorded at least one clinical outcome measure of response (imaging, histopathological or cosmetic) to HIFU treatment.

RESULTS

Nine studies fulfilled the inclusion criteria. The absence of tumour or residual tumour after treatment was reported for 95·8 per cent of patients (160 of 167). No residual tumour was found in 46·2 per cent (55 of 119; range 17-100 per cent), less than 10 per cent residual tumour in 29·4 per cent (35 of 119; range 0-53 per cent), and between 10 and 90 per cent residual tumour in 22·7 per cent (27 of 119; range 0-60 per cent). The most common complication associated with HIFU ablation was pain (40·1 per cent) and less frequently oedema (16·8 per cent), skin burn (4·2 per cent) and pectoralis major injury (3·6 per cent). MRI showed an absence of contrast enhancement after treatment in 82 per cent of patients (31 of 38; range 50-100 per cent), indicative of coagulative necrosis. Correlation of contrast enhancement on pretreatment and post-treatment MRI successfully predicted the presence of residual disease.

CONCLUSION

HIFU treatment can induce coagulative necrosis in breast cancers. Complete ablation has not been reported consistently on histopathology and no imaging modality has been able confidently to predict the percentage of complete ablation. Consistent tumour and margin necrosis with reliable follow-up imaging are required before HIFU ablation can be evaluated within large, prospective clinical trials.

Magnetic resonance imaging for the exploitation of bubble-enhanced heating by high-intensity focused ultrasound: a feasibility study in ex vivo liver

Bubble-enhanced heating (BEH) may be exploited to improve the heating efficiency of high-intensity focused ultrasound in liver and to protect tissues located beyond the focal point. The objectives of this study, performed in ex vivo pig liver, were (i) to develop a method to determine the acoustic power threshold for induction of BEH from displacement images measured by magnetic resonance acoustic radiation force imaging (MR-ARFI), and (ii) to compare temperature distribution with MR thermometry for HIFU protocols with and without BEH. The acoustic threshold for generation of BEH was determined in ex vivo pig liver from MR-ARFI calibration curves of local tissue displacement resulting from sonication at different powers. Temperature distributions (MR thermometry) resulting from "conventional" sonications (20 W, 30 s) were compared with those from "composite" sonications performed at identical parameters, but after a HIFU burst pulse (0.5 s, acoustic power over the threshold for induction of BEH). Displacement images (MR-ARFI) were acquired between sonications to measure potential modifications of local tissue displacement associated with modifications of tissue acoustic characteristics induced by the burst HIFU pulse. The acoustic threshold for induction of BEH corresponded to a displacement amplitude of approximately 50 μm in ex vivo liver. The displacement and temperature images of the composite group exhibited a nearly spherical pattern, shifted approximately 4 mm toward the transducer, in contrast to elliptical shapes centered on the natural focal position for the conventional group. The gains in maximum temperature and displacement values were 1.5 and 2, and the full widths at half-maximum of the displacement data were 1.7 and 2.2 times larger than in the conventional group in directions perpendicular to ultrasound propagation axes. Combination of MR-ARFI and MR thermometry for calibration and exploitation of BEH appears to increase the efficiency and safety of HIFU treatment.

Visualization of thermal ablation lesions using cumulative dynamic contrast enhancement MRI

A novel robust and user friendly method for post-processing dynamic contrast enhanced (DCE) MRI data is presented, which provides reliable real-time delineation of the borders of thermal ablation lesions on low SNR images shortly after contrast agent injection without any model-based curve fitting. Some simple descriptors of the DCE process are calculated in a time efficient recursive manner and combined into a single image reflecting both current and previous enhancement states of each pixel, which allows robust discrimination between tissue areas with different perfusion properties. The resulting cumulative DCE (CDCE) images are shown to exhibit a strong correlation with histopathology and late gadolinium enhancement representations of the thermal damage in soft tissue. It is shown that the outer border of the non-perfused ablation lesion core on CDCE MRI corresponds to the histopathological lesion border. The described method has a potential not only to facilitate thermal ablation outcome assessment, but also to improve detection of infiltrative tumours and reduce the administered contrast agent dose in any DCE scans.

Magnetic resonance image-guided versus ultrasound-guided high-intensity focused ultrasound in the treatment of breast cancer

Image-guided high-intensity focused ultrasound (HIFU) has been used for more than ten years, primarily in the treatment of liver and prostate cancers. HIFU has the advantages of precise cancer ablation and excellent protection of healthy tissue. Breast cancer is a common cancer in women. HIFU therapy, in combination with other therapies, has the potential to improve both oncologic and cosmetic outcomes for breast cancer patients by providing a curative therapy that conserves mammary shape. Currently, HIFU therapy is not commonly used in breast cancer treatment, and efforts to promote the application of HIFU is expected. In this article, we compare different image-guided models for HIFU and reviewed the status, drawbacks, and potential of HIFU therapy for breast cancer.

Toward MR-guided high intensity focused ultrasound for presurgical localization: focused ultrasound lesions in cadaveric breast tissue

PURPOSE

To investigate magnetic resonance image-guided high intensity focused ultrasound (MR-HIFU) as a surgical guide for nonpalpable breast tumors by assessing the palpability of MR-HIFU-created lesions in ex vivo cadaveric breast tissue.

MATERIALS AND METHODS

MR-HIFU ablations spaced 5 mm apart were made in 18 locations using the ExAblate2000 system. Ablations formed a square perimeter in mixed adipose and fibroglandular tissue. Ablation was monitored using T1-weighted fast spin echo images. MR-acoustic radiation force impulse (MR-ARFI) was used to remotely palpate each ablation location, measuring tissue displacement before and after thermal sonications. Displacement profiles centered at each ablation spot were plotted for comparison. The cadaveric breast was manually palpated to assess stiffness of ablated lesions and dissected for gross examination. This study was repeated on three cadaveric breasts.

RESULTS

MR-ARFI showed a collective postablation reduction in peak displacement of 54.8% ([4.41 ± 1.48] μm pre, [1.99 ± 0.82] μm post), and shear wave velocity increase of 65.5% ([10.69 ± 1.60] mm pre, [16.33 ± 3.10] mm post), suggesting tissue became stiffer after the ablation. Manual palpation and dissection of the breast showed increased palpability, a darkening of ablation perimeter, and individual ablations were visible in mixed adipose/fibroglandular tissue.

CONCLUSION

The results of this preliminary study show MR-HIFU has the ability to create palpable lesions in ex vivo cadaveric breast tissue, and may potentially be used to preoperatively localize nonpalpable breast tumors.

Imaging in interventional oncology

Medical imaging in interventional oncology is used differently than in diagnostic radiology and prioritizes different imaging features. Whereas diagnostic imaging prioritizes the highest-quality imaging, interventional imaging prioritizes real-time imaging with lower radiation dose in addition to high-quality imaging. In general, medical imaging plays five key roles in image-guided therapy, and interventional oncology, in particular. These roles are (a) preprocedure planning, (b) intraprocedural targeting, (c) intraprocedural monitoring, (d) intraprocedural control, and (e) postprocedure assessment. Although many of these roles are still relatively basic in interventional oncology, as research and development in medical imaging focuses on interventional needs, it is likely that the role of medical imaging in intervention will become even more integral and more widely applied. In this review, the current status of medical imaging for intervention in oncology will be described and directions for future development will be examined.