When used correctly with the appropriate precautions in regards to dose, ultrasound can be applied in many therapeutic situations to benefit the patient. In fact, the use of ultrasound energy as a treatment predates its use an imaging technique and continues to be used in practice today.
Low-frequency ultrasound (1MHz) has been widely practiced since the 1950s for some conditions, such as tendinitis and bursitis. This grew into the use of high-pressure amplitude shock waves in the 1980s, which could be used to treat kidney stones and gallstones. The ultrasound waves are utilized to break up the stones into smaller pieces, such that they can be removed from the body via natural excrement processes.
There are currently several applications of ultrasound therapy that have been approved for use in practice. These include:
- Uterine fibroid ablation
- Phacoemulsification (cataract removal)
- Surgical cutting of tissue and hemostasis
- Transdermal drug delivery
- Promotion of bone fracture healing
- Targeted gene therapy
- Bacterial control
- Dental hygiene
- Detection of pelvic abnormalities
- Lithotripsy, fragmentation of calculi (e.g. kidney stones)
Each of these applications has a specific dosage or exposure level that has been determined to offer the optimal benefit with a measured degree of risk. Low doses are usually used to instigate beneficial and reversible cellular effects, whereas high doses are used when death of the cells is intended.
Both benign and malignant tumors can be targeted with high intensity focused ultrasound (HIFU) as a treatment method. This generally uses lower frequency sound waves than those used in diagnostic techniques (250-2000kHz) applied for longer periods of time. Magnetic response imaging (MRI) is often used to guide the ultrasound therapy and target the dose directly towards the affected cells.
Although higher frequency ultrasound waves have previously been used in the treatment of cancer, this is not commonly seen in practice today. This shift has arisen due to the lack of scientific evidence supporting the efficacy of ultrasound therapy and concern about significant adverse effects.
Ultrasound waves can also be used to assist other types of therapy, as an immediate imaging tool. This allows targeted treatments to be applied to specific areas of the body, with minimal effects on healthy cells.
The prime example of this is the non-surgical treatment of varicose veins. Both sclerotherapy and endovenous laser treatment work directly on the varicose veins, but rely on the use of ultrasound to view the treatment process and results in real-time. Additionally, ultrasound imaging also assists in the carrying out of lipectomy and liposuction.
Ultrasound offers an immense benefit in the diagnosis of certain health conditions.
For example, elastography can help to differentiate healthy, elastic tissue from unhealthy tissue in specific areas of the body. This differs from other ultrasound imaging as it requires both a transceiver and a transmitter, which perturbs the system and causes unhealthy tissue to oscillate.
Additionally, ultrasound waves can also be used to detect any abnormalities in the pelvic area. This is particularly beneficial as it can be difficult to reach this area and view any abnormalities that may be present.