Tolerability and Feasibility of X-ray Guided Non-Invasive Ablation of the Medial Branch Nerve with Focused Ultrasound: Preliminary Proof of Concept in a Pre-clinical Model

MR-guided Focused Ultrasound for Musculoskeletal Applications

MR-guided focused ultrasound (MRgFUS) has a wide range of musculoskeletal applications. Some indications are well validated, specifically the treatment of painful osseous metastases and osteoid osteoma. Others are only beginning to be studied, such as the treatment of painful facet, sacroiliac, and knee joints. MRgFUS of soft tissue lesions also shows promise, particularly in patients whom alternative modalities are not feasible or may result in significant morbidity. Ongoing and future research will illuminate the full potential for MRgFUS in the treatment of musculoskeletal conditions.

Fluoroscopy-guided high-intensity focused ultrasound neurotomy of the lumbar zygapophyseal joints: a prospective, open-label study

OBJECTIVE

The objective of this study is to investigate safety and effectiveness of a fluoroscopy-guided high-intensity focused ultrasound (HIFU) system for thermal ablation of the lumbar medial branch nerves.

METHODS

This dual center prospective cohort study enrolled 30 participants with lumbar zygapophyseal joint syndrome. Each participant previously had a positive response to either a single diagnostic analgesic block or radiofrequency ablation (RFA). The primary effectiveness outcome was individual responder rate, defined as a reduction of two points or more on the pain intensity numerical rating scale without an increase in opioid intake, or a reduction in opioid intake without an increase in pain at 6 months after the intervention. The primary safety outcome was procedure-related or device-related adverse events (AEs). Secondary outcome variables included MRI evidence of tissue ablation, Oswestry Disability Index, 12-Item Short Form Health Survey, Brief Pain Inventory, and Patient Global Impression of Change.

RESULTS

The individual responder rate was 89.7% at 2 days, 89.7% at 7 days, 72.4% at 14 days, 82.1% at 30 days, 59.3% at 90 days and 82.6% at 180 days. The average Numeric Rating Scale for pain severity decreased from 7.1 at baseline to 3.0 (N=29) after 2 days, 3.0 (N=29) after 7 days, 3.1 (N=29) after 14 days, 3.2 (N=28) after 30 days, 4.3 (N=27) after 90 days, and 3.3 (N=23) after 180 days. All participants tolerated the procedure well with no significant side effects or complications.

CONCLUSIONS

Fluoroscopy-guided HIFU neurotomy achieved clinical responses comparable with RFA, and there were no significant device-related or procedure-related AEs.

TRIAL REGISTRATION NUMBER

NCT04129034.

Fluoroscopy-guided high-intensity focused ultrasound ablation of the lumbar medial branch nerves: dose escalation study and comparison with radiofrequency ablation in a porcine model

BACKGROUND

Radiofrequency ablation (RFA) is a common method for alleviating chronic back pain by targeting and ablating of facet joint sensory nerves. High-intensity focused ultrasound (HIFU) is an emerging, non-invasive, image-guided technology capable of providing thermal tissue ablation. While HIFU shows promise as a potentially superior option for ablating sensory nerves, its efficacy needs validation and comparison with existing methods.

METHODS

Nine adult pigs underwent fluoroscopy-guided HIFU ablation of eight lumbar medial branch nerves, with varying acoustic energy levels: 1000 (N=3), 1500 (N=3), or 2000 (N=3) joules (J). An additional three animals underwent standard RFA (two 90 s long lesions at 80°C) of the same eight nerves. Following 2 days of neurobehavioral observation, all 12 animals were sacrificed. The targeted tissue was excised and subjected to macropathology and micropathology, with a primary focus on the medial branch nerves.

RESULTS

The percentage of ablated nerves with HIFU was 71%, 86%, and 96% for 1000 J, 1500 J, and 2000 J, respectively. In contrast, RFA achieved a 50% ablation rate. No significant adverse events occurred during the procedure or follow-up period.

CONCLUSIONS

These findings suggest that HIFU may be more effective than RFA in inducing thermal necrosis of the nerve.

Low-Cost Thermochromic Quality Assurance Phantom for Therapeutic Ultrasound Devices: A Proof of Concept

High-intensity focused ultrasound (HIFU) transducer acoustic output can vary over time as a result of an inconsistent power supply, damage to the transducer or deterioration over time. Therefore, easy implementation of a daily quality assurance (DQA) method is of great importance for pre-clinical research and clinical applications. We present here a thermochromic material-based phantom validated by thermal simulations and found to provide repeatable visual power output assessments in fewer than 15 s that are accurate to within 10%. Whereas current available methods such as radiation force balance measurements provide an estimate of the total acoustic power, we explain here that the thermochromic phantom is sensitive to the shape of the acoustic field at focus by changing the aperture of a multi-element transducer with a fixed acoustic power. The proposed phantom allows the end user to visually assess the transducer's functionality without resorting to expensive, time-consuming hydrophone measurements or image analysis.

Fluoroscopy-Guided High-Intensity Focused Ultrasound Neurotomy of the Lumbar Zygapophyseal Joints: A Clinical Pilot Study

OBJECTIVE

To investigate the safety and feasibility of a fluoroscopy-guided, high-intensity focused ultrasound system for zygapophyseal joint denervation as a treatment for chronic low back pain.

METHODS

The clinical pilot study was performed on 10 participants diagnosed with lumbar zygapophyseal joint syndrome. Each participant had a documented positive response to a diagnostic block or a previous, clinically beneficial radiofrequency ablation. For a descriptive study, the primary outcome was the safety question. All device- or procedure-related adverse events were collected. Secondary outcome variables included the average numeric rating scale for pain, the Roland-Morris Disability Questionnaire, the Brief Pain Inventory, the Patient Global Impression of Change, the morphine equivalent dose, and the finding of the neurological examination.

RESULTS

All participants tolerated the procedure well with no significant device- or procedure-related adverse events; there was one episode of transient pain during the procedure. The average numeric rating scale score for pain decreased from 6.2 at baseline to 2.1 (n = 10) after 1 month, 4.9 (n = 9) after 3 months, 3.0 (n = 8) after 6 months, and 3.0 (n = 6) after 12 months. The ratio of participants who were considered a treatment success was 90% at 1 month, 50% at 3 months, 60% at 6 months, and 40% at 12 months.

CONCLUSIONS

The first clinical pilot study using a noninvasive, fluoroscopy-guided, high-intensity focused ultrasound lumbar zygapophyseal neurotomy resulted in no significant device- or procedure-related adverse events and achieved clinical success comparable with that of routine radiofrequency ablation.

Clinical application of the therapeutic ultrasound in urologic disease: Part II of the therapeutic ultrasound in urology

This article aimed to review the clinical application and evidence of the therapeutic ultrasound in detail for urological diseases such as prostate cancer, kidney tumor, erectile dysfunction, and urolithiasis. We searched for articles about high-intensity focused ultrasound (HIFU), extracorporeal shock wave therapy, ultrasound lithotripsy, and extracorporeal shockwave lithotripsy (ESWL) in the MEDLINE and Embase. HIFU may be indicated as a primary treatment for low- or intermediate-risk prostate cancer, and salvage therapy for local recurrence as a promising way to address the limitations of current standard therapies. The application of HIFU in treating kidney tumors has scarcely been reported with unsatisfactory results. Evidence indicates that low-intensity shockwave therapy improves subjective and objective erectile function in patients with erectile dysfunction. Regarding the application of ultrasound in stone management, the novel combination of ultrasound lithotripsy and other energy sources in a single probe promises to be a game-changer in efficiently disintegrating large kidney stones in percutaneous nephrolithotomy. ESWL is losing its role in managing upper urinary tract calculi worldwide. The burst-wave lithotripsy and ultrasound propulsion could be the new hope to regain its position in the lithotripsy field. According to our investigations and reviews, cavitation bubbles of the therapeutic ultrasound are actively being used in the field of urology. Although clinical evidence has been accumulated in urological diseases such as prostate cancer, kidney tumor, erectile dysfunction, and lithotripsy, further development is needed to be a game-changer in treating these diseases.