Magnetic resonance-guided focused ultrasound treatment of facet joint pain: summary of preclinical phase.

STUDY DESIGN: A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted to test the feasibility, safety, and efficacy of magnetic resonance-guided focused ultrasound (MRgFUS) for treating facet joint pain. OBJECTIVE: The goal of the current study was to develop a novel method for accurate and safe noninvasive facet joint ablation using MRgFUS. SUMMARY OF BACKGROUND DATA: Facet joints are a common source of chronic back pain. Direct facet joint interventions include medial branch nerve ablation and intra-articular injections, which are widely used, but limited in the short and long term. MRgFUS is a breakthrough technology that enables accurate delivery of high-intensity focused ultrasound energy to create a localized temperature rise for tissue ablation, using MR guidance for treatment planning and real-time feedback. METHODS: We validated the feasibility, safety, and efficacy of MRgFUS for facet joint ablation using the ExAblate 2000® System (InSightec Ltd., Tirat Carmel, Israel) and confirmed the system's ability to ablate the edge of the facet joint and all terminal nerves innervating the joint. A phantom experiment, two thermocouple experiments, three in vivo pig experiments, and a simulated treatment on a healthy human volunteer were conducted. RESULTS: The experiments showed that targeting the facet joint with energies of 150-450 J provides controlled and accurate heating at the facet joint edge without penetration to the vertebral body, spinal canal, or root foramina. Treating with reduced diameter of the acoustic beam is recommended since a narrower beam improves access to the targeted areas. CONCLUSIONS: MRgFUS can safely and effectively target and ablate the facet joint. These results are highly significant, given that this is the first study to demonstrate the potential of MRgFUS to treat facet joint pain.

Pain palliation in patients with bone metastases using MR-guided focused ultrasound surgery: a multicenter study.

BACKGROUND: Noninvasive thermal ablation using magnetic resonance (MR)-guided focused ultrasound (MRgFUS) has been shown to be clinically effective in uterine fibroids, and is being evaluated for ablation of breast, liver, and brain lesions. Recently MRgFUS has been evaluated for palliation of pain caused by bone metastases. We present the clinical results of a multicenter study using MRgFUS for palliation of bone metastases pain. METHODS: A multicenter study to evaluate the safety and efficacy of MRgFUS palliative treatment of bone metastases was conducted in patients suffering from painful metastatic bone lesions for which other treatments were either ineffective or not feasible. Thirty-one patients with painful bone metastases underwent the MRgFUS procedure in three medical centers. Treatment safety was evaluated by assessing the device-related complications. Effectiveness of pain palliation was evaluated using the visual analog pain score (VAS), and measurable changes in the intake of opioid analgesics. RESULTS: Thirty-six procedures were performed on 31 patients. Mean follow-up time was 4 months. 25 patients underwent the planned treatment and were available for 3 months post-treatment follow-up. 72% of the patients (18/25) reported significant pain improvement. Average VAS score was reduced from 5.9 prior to treatment to 1.8 at 3 months post treatment. 67% of patients with recorded medication data reported a reduction in their opioid usage. No device-related severe adverse events were recorded. CONCLUSION: The results suggest that MRgFUS has the ability to provide an accurate, effective, and safe noninvasive palliative treatment for patients with bone metastases.

A new MRI method, tested in vitro for the assessment of thermal coagulation and demonstrated in vivo on focused ultrasound ablation.

A new MRI method is described. It is implemented for the assessment of thermal coagulation after thermal treatment. The method does not require injection of a contrast agent. The image is based on the amount of magnetization exchange between macromolecules and water in the tissue. Coagulated tissue has a faster magnetization exchange rate, forming the new contrast. In this study, the new imaging method is shown to have good contrast between coagulated and untreated excised tissues of porcine liver and muscle. The method is also successfully demonstrated in vivo in rat thigh muscle thermally treated with focused ultrasound.

Magnetic resonance-guided focused ultrasound surgery using an enhanced sonication technique in a pig muscle model.

THE PURPOSE OF THIS STUDY: To evaluate the safety and efficacy of an enhanced magnetic resonance-guided focused ultrasound (MRgFUS) emission protocol that results in more extensive treatment by increasing the volume of each focal ablation using the same energy. MATERIALS AND METHODS: Six pigs were treated with an MRgFUS system combined with real-time MR, for imaging and temperature mapping, with 102 "enhanced" and 97 "regular" focal ablations performed on both buttock muscles. Real-time imaging, temperature mapping, and acoustic reflected spectrum data enabled immediate evaluation of the results. MR contrast-enhanced images and pathology examinations were used for confirmation. RESULTS: The location of the ablated volume by "enhanced" sonication is predictable, with a maximum possible shift of 6 mm toward, and 3 mm away, from the transducer. The ablated volume after enhanced sonication was, on average, 1.8 times larger than after a regular sonication of the same energy. Pathology results showed the same thermally induced damage patterns in the enhanced sonications and the regular sonications. CONCLUSION: Accelerated MRgFUS with enhanced sonication is a safe, controllable, and more effective tissue ablative modality than standard sonication. This new technology may significantly reduce the length of tumor ablation procedures. (Isn't the new technology you're talking about MRgFUS? If so, you don't need to repeat it at the end of this sentence.).

Magnetic resonance-guided focused ultrasound surgery (MRgFUS): ablation of liver tissue in a porcine model.

BACKGROUND: Liver surgery is technically demanding and is considered a major procedure with relatively high morbidity rates. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) uses focused ultrasonic energy to create a heat coagulation lesion, which can be achieved in a totally controlled, very accurate manner (<1 mm). The aim of this study was to evaluate the safety and accuracy of non-invasive focal ablation of liver tissue achieved by consecutive MRgFUS sonications. MATERIALS AND METHODS: Six MRgFUS procedures were performed in five pigs under general anesthesia, with the ExAblate 2000 system (InSightec, Israel). Real-time imaging and temperature mapping (Signa Twinspeed 1.5T, GEHC, USA) enabled the immediate evaluation of the results of each sonication. Different foci were chosen within the liver. These mock lesions were ablated by several sonications, each of them performed during 20-30 s of apnea. Between sonications, the pigs were normally ventilated. The pigs were sacrificed 3-21 days after the procedure and their livers were examined. RESULTS: The MRgFUS created complete tissue destruction of mock lesions in different areas of the pig's liver. The lesion sizes in each animal varied according to the number of sonications used and the extent of overlap between adjacent sonications. The lesion ranged in size from 1.5 cm x 1.5 cm x 2.0 cm to 5.5 cm x 4.5 cm x 2.0 cm. There was no morbidity. CONCLUSIONS: MRgFUS under general anesthesia is a safe, completely non-invasive technology for the ablation of liver tissue. Liver tissue can be ablated in a very accurate manner, based on the pre-treatment planning on the MR images. The MR imaging characteristics, including real-time temperature mapping, enable real-time control of every step of the ablation process. Mechanical ventilation with intermittent periods of apnea is a technique that overcomes the problem of the respiratory movements of the liver.

Magnetic resonance-guided focused ultrasound surgery (MRgFUS). Four ablation treatments of a single canine hepatocellular adenoma.

BACKGROUND: Canine hepatocellular adenomas are benign, well-differentiated, primary hepatic tumors. Surgical resection is technically demanding and is considered a major procedure with relatively high morbidity rates. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) uses focused ultrasonic energy to non-invasively create a heat-coagulated lesion deep within the body. This effect can be achieved in a controlled, accurate manner. The aim of this study was to evaluate the safety, accuracy and efficacy of non-invasive focal ablation of tissue volumes of a canine benign liver tumour by consecutive MRgFUS sonications. MATERIALS AND METHODS: Four MRgFUS procedures were performed in a 10-year-old, male, mixed large breed dog (45 kg) under general anaesthesia. The exact location and volume of the ablated areas were planned on the MR images. Real-time MR imaging and temperature mapping enabled the immediate evaluation of the effect of each sonication. Different areas were chosen within the tumour. These volumes of tumoral tissue were ablated by multiple sonications. To allow accurate targeting and quality imaging, sonications were performed during 20-30 s of apnoea. Between the sonications the dog was normally ventilated. The dog was operated 21 days after the fourth ablative procedure. The tumour was resected and histopathologically examined. RESULTS: The MRgFUS created necrosis with contiguous areas of complete tissue destruction within the liver tumour, in full accordance with the planning. A focal thermal injury to the cartilage of the right lower ribs was noted after the fourth treatment. This lesion became infected and was treated surgically. Ten months after the last treatment the dog is well and healthy. CONCLUSIONS: Focused ultrasound ablation of liver tumoral tissue with MR guidance under general anaesthesia and controlled apnoea is a safe and accurate treatment modality. Its main advantage is that it is a completely non-invasive image-guided treatment. The ablation of significant volumes of a highly vascular liver tumoral tissue was achieved. Such tissue can be ablated in a very accurate manner, exactly according to the pretreatment planning on the MR images. The MR imaging characteristics, including real-time temperature mapping, enable real-time control of every step of the ablation process. Mechanical ventilation with intermittent apnoea periods overcomes the problem of the respiratory movements of the liver. Care must be taken to avoid the passage of the ultrasound beam through energy-absorbing calcified tissue.

Divalent cation levels in serum and preovulatory follicular fluid of women undergoing in vitro fertilization embryo transfer.

In this controlled clinical study, we determined the serum and follicular fluid concentrations of the biologically active fractions of magnesium (Mg) and calcium (Ca) in 39 women undergoing controlled ovarian stimulation (COH) for in vitro fertilization (IVF) embryo transfer (ET). Serum levels of ionized Ca (Ca2+) and ionized Mg (Mg2+) were measured during day 3 of the IVF cycle, on the day of ovum pickup and 12 days following ET. Follicular fluid levels were measured on the day of ovum pickup. Serum levels of Mg2+ decreased and Ca2+ levels increased during the IVF cycle. Mg levels were significantly higher in follicular fluid than in serum. Ca2+ and Mg2+ may play a role in the preovulatory follicle, a possibility that warrants further study.