In most US therapy, physicians and support staff are relevant to the procedure.  Physicians are the primary provider of care for therapeutic ultrasound, while support staff often assist in monitoring patients and equipment. Musculoskeletal applications of low-intensity ultrasound are an exception to this rule. Due to the limited safety risks for low-intensity ultrasound, many physical therapists and physicians can provide this treatment with little or no assistance.

For soft tissue tumors requiring MRgUS, MRI is necessary before the procedure; this will help physicians localize the tumor and position the patient for the procedure. Prior imaging will be compared and utilized to position the patient. Musculoskeletal uses of ultrasound therapy require short preparation and include examining the overlying skin for burns, rashes, infections, and active bleeding. Personnel should always inspect equipment before the start of the procedure. 

Within the variety of FDA approved therapeutic ultrasound procedures, there are a few similarities in protocols. All ultrasound therapies transmit their waves from a transducer to the target tissues by being placed directly on the skin, through a coupling medium. The goal of the coupling medium is to conduct the waves to the target area in an efficient, predictable pattern. Various mediums have undergone testing, but hypoallergenic gels seem to produce strong transduction of waves with minimal interference[13]. Step by step outlines for some FDA approved therapies are listed below.

ESWL

• The patient gets positioned on a fluoroscopic table
• X-rays undergo review and the patient adjusted with fluoroscopic images to target stone within the kidney
• The patient may be given sedative or spinal anesthesia for pain control as shockwaves can cause discomfort
• Vertical adjustments of the table are made to position the stone within the ‘focus’ of the ultrasound wave propagation
• Bursts of shockwaves get delivered at approximately 120 shockwaves per minute

HIFU

• The patient is supported with the patient lying supine or laterally on a table
• An immobilizer is an option on tissues such as breast
• Local anesthetic (1% lidocaine, 0.5% bupivacaine with epinephrine) may be used for pain control
• The tissue of interest is visualized and outlined with ultrasound or MRI
• Head of the HIFU probe gets centered upon the tissue of interest
• A test dose gets delivered to the center of the tissue of interest
• If necessary, adjustments to power are made based on the depth of tissue
• Bursts of ultrasonic waves are delivered to the tissue
• Destruction of tissue (hyperechoic for U/S or thermometry for MRI) is verified with an imaging modality
• A burst of ultrasonic can continue to be delivered circumferentially around the tissue until adequate tissue destruction

Musculoskeletal

• The patient gets positioned comfortably
• Expose skin over the area to be treated
• Turn on the Ultrasound machine and set range at 1 to 3 MHz with an intensity of 1.0W/cm
• Apply hypoallergenic gel to the skin
• Apply ultrasound to skin utilizing a stroking motion
• Ultrasound should remain moving while applied to the skin
• Treatment time should be approximately 10 minutes
• After 10 minutes of treatment, wipe skin clean of ultrasound gel

Ultrasound therapies are alternative therapies due to their low risk of complications. Low-intensity ultrasound can cause superficial burns due to prolonged exposure times. Therefore, the ultrasound wand should remain in motion when in contact with the skin. HIFU paired with MRI has the advantage of monitoring temperatures of the tissues receiving treatment. When used correctly, this can prevent burning and necrosis of healthy tissue. ESWL presents some of the more severe complications. Internal hemorrhage and scarring can occur. Procedural techniques like duration of shockwaves and total shockwave exposure to prevent scarring of renal tissue during ESWL.[13]

Ultrasound has expanded from its diagnostic origins to become a robust, adaptable therapeutic technology for physicians in a variety of specialties. Low-intensity ultrasound has become a mainstay therapy for many acute and chronic musculoskeletal conditions in the outpatient or inpatient setting due to its ease of use and limited complication rate. Meanwhile, HIFU has emerged as a non-invasive therapy used for the ablation of many types of tissues. Though many applications are still experimental, it is likely to be widely accepted as a safe, alternative therapy for a variety of tumors and aberrant tissues.

Overall, studies of ultrasound therapies have demonstrated that it is a safe, non-invasive, and effective procedure that clinicians can offer as primary or adjuvant therapy to traditional treatments.

There is level III evidence for the use of HIFU for atrial ablation in patients with atrial fibrillation. Ninet et al. found a cure rate of 80% at six months when HIFU was used to ablate aberrant atrial tissue causing paroxysmal and persistent atrial fibrillation.[6] Additionally, this procedure can be completed without the use of cardiopulmonary bypass and without the ultrasound wand contacting blood. Complications like ARDS, SIRS, and hemodilution are common and well documented with the use of cardiopulmonary bypass, making HIFU a potentially safer alternative for atrial fibrillation cure.[14] However, this procedure is still experimental, and further studies focusing on effectiveness and safety are necessary.

Numerous studies have shown level II and Level III evidence for MRgFUS that demonstrate its safety and effectiveness for breast and uterine soft tissue masses. A systematic review conducted by Peek Et al. found the absence of a tumor or residual tumor in 95.8% of patients undergoing HIFU treatment for breast cancer.[15] Typically, breast cancer receives treatment with breast-conserving surgery or mastectomy. However, these procedures suffer from increased risk of bleeding, infection, pain, and cosmetic issues. Thus, the need for alternative therapies, like HIFU, has increased. Additionally, some patients with significant co-morbidities may not be surgical candidates or the surgery may. Hysterectomy can be curative for uterine fibroids, but should only be an option in women who are no longer interested in bearing children.[16] Stewart Et al. found 71% of women experienced symptom reduction at six months with a low incidence of adverse events.[17] Though no longitudinal studies examining the long-term effects of HIFU exist, Bohlmann Et al. reviewed 100 cases and found no increased risk of miscarriage or other obstetrical outcomes.[18] FDA approval of MRgFUS for uterine fibroids occurred in 2004, and numerous studies have demonstrated its effectiveness and safety

Lastly, there is level III evidence for the use of low-intensity ultrasound for pain in degenerative musculoskeletal disorders. Muftic et al. compared two groups receiving low-intensity ultrasound treatment at varying power settings and found visual analog scores for the pain to decrease by approximately 4 points in both groups.[19] This study included men and women suffering from chronic limb or spine pain. However, a systematic review conducted on ultrasound therapy for a variety of musculoskeletal conditions found limited benefits.[20] Shanks et al. also found limited evidence for ultrasound therapy benefits in lower limb musculoskeletal conditions.[21] More robust studies with clear indications and procedural techniques need to be conducted to make broad conclusions on low-intensity ultrasound.

This research was supported (in whole or part) by HCA Healthcare and/or an HCA Healthcare affiliated entity. The views expressed in this publication represent those of the author(s) and do not necessarily represent the official views of HCA Healthcare or any of its affiliated entities.