High-Frequency (20 MHz) Focused Ultrasound: A Novel Method for Noninvasive Tattoo Removal.

Alternatives or complements to laser tattoo removal are needed. Laser removal requires 8-12 sessions and can easily take longer than a year. Some colors cannot be removed, and scars may appear. Applied to allergic reactions in red tattoos, lasers can boost the allergy. A recently developed 20 MHz high-intensity focused ultrasound (HIFU) is introduced as a complementary method to lasers, but also as a stand-alone treatment for selected groups. 20 MHz HIFU allows for application of high-power ultrasound energy to very small focal targets in the dermis, and thereby precise confinement of thermal lesions in the outer layers of human skin, precisely where tattoo inks are deposited. HIFU treatment is "color blind" and can target any type of colored pigment in the dermis. It produces a controlled thermal lesion (up to 65°C) with superficial necrosis followed by an eschar with embedded tattoo pigment. This eschar, containing the tattoo pigment, is discharged over some weeks, and finally replaced by healed skin. HIFU can efficiently remove tattoos of any color in only 1-3 sessions. It can be applied to tattoos when lasers fail to produce efficient removal. The types of side effects are the same as with lasers. The operator shall be trained and knowledgeable. 20 MHz HIFU can furthermore be used in clinical and esthetic dermatology for various other applications, and a range of applications are open in clinical dermatology.

Removal of Common Warts by High-Intensity Focused Ultrasound: An Introductory Observation.

Therapies of common warts are cumbersome and not very effective. Recurrences are common. A new 20 MHz high-intensity focused ultrasound (HIFU) method is introduced as a new potential treatment modality. With HIFU, selected targets in the epidermis and dermis can be treated with full control of the depth and position of the ultrasound lesion and the energy applied to the target. The treatment can be monitored directly in real-time via an integrated dermoscope in the ultrasound probe. Two warts were treated with 8-10 shoulder-by-shoulder treatment doses, focal depth 1.3 mm, and 1.2 J/dose. Pretreatment ultrasound B-mode scanning had shown the thickness and depth of the warts. The treated areas developed a dry wound covered by a crust over the next 1-2 days. After 2 weeks the skin was healed, with no wart and no scar. Observation showed no reoccurrence. HIFU has future potential for treatment of common warts and flat warts, and a broad range of skin lesions being logic further candidates for targeted ablative treatment. One single treatment may suffice. It is, therefore, a new modality in dermatology with a large range of indications.

High-frequency (20 MHz) high-intensity focused ultrasound: New Treatment of actinic keratosis, basal cell carcinoma, and Kaposi sarcoma. An open-label exploratory study.

BACKGROUND: Skin cancer is common, growing, challenging, and in need of progress in early-stage treatment. 20 MHz high-intensity focused ultrasound (HIFU) is new and applied to actinic keratosis (AK) and skin cancers for the first time. HIFU of lower frequency is already used in the treatment of internal cancers. MATERIALS AND METHODS: Eight patients with 201 AK lesions, one patient with 7 basal cell carcinomas (reoccurrences after PDT), and one patient with 7 Kaposi sarcoma lesions (4 treated with radiotherapy in the past) were given 1-3 HIFU treatments. Twenty megahertz HIFU was dosed as 150 ms at 0.6-1.2 J/shot applied to target lesions. Probes with different target depths were available. The preferred shot energy and focal depth in AK were 0.9 J and 1.3 mm. A "Sandwich" strategy with HIFU applied in two depths were tried in cancers. The follow-up period was 3-6 months. RESULTS: All AK cleared except 5, giving a cure rate of 97%. Post-treatment lesion healed in 1-2 weeks with no scar. VAS pain was from 1 to 8, and in any case less than experienced with previous PDT. In both basal cell carcinoma (BCC) and sarcoma, healing was confirmed by histological verification. DISCUSSION/CONCLUSION: 20 MHz HIFU was an effective and safe treatment of AK. This new treatment, applicable to any anatomical site, has promising advantages relative to PDT and has the potential to replace or supplement PDT in future. Case-observations indicated that HIFU can be useful in skin cancers as well.

High-frequency (20 MHz) high-intensity focused ultrasound: New ablative method for color-independent tattoo removal in 1-3 sessions. An open-label exploratory study.

BACKGROUND: High-intensity focused ultrasound (HIFU) operating at 20 MHz is new and potentially applicable to ablative tattoo removal. The method was documented safe and rational in preclinical testing. MATERIALS AND METHODS: High-intensity focused ultrasound was introduced to subjects when lasers and dermatome shaving had failed or caused side effects. Transducers with focal depths between 1.1 mm and 1.7 mm in the skin were used, and settings of 0.4-1.2 J/shot at pulse durations of 150 ms were applied. Tattoos were covered with synergistic "shoulder-by-shoulder" focused ultrasound shots. Effectiveness and side effects were measured. RESULTS: Twenty-two subjects with 67 tattoos were treated. 62% benefitted (19% cleared, 43% partially cleared), and 28% had minor effect. VAS pain was 5-6 versus 7-9 with previous lasers removal. Wound healing was longer after HIFU ablation (1-3 months). 57% of subjects had no scar or minor visible changes of skin surface markings only, while 19% had moderate or major skin thickening. Hypertrophic scar or keloid scars were not observed. DISCUSSION/CONCLUSION: High-intensity focused ultrasound was effective in removal of difficult tattoos of any color where Nd:YAG lasers had failed. The method only needs 1-3 sessions. As an ablative method, the wound healing period is longer than with laser removal and needs attention. Focused ultrasound can be used as a first-line treatment of smaller tattoos independent of color, and second line when Nd:YAG lasers have failed or caused problems. The operator shall be qualified, as with lasers.

High-frequency (20 MHz) high-intensity focused ultrasound system for dermal intervention: A 12-week local tolerance study in minipigs.

BACKGROUND: High-intensity focused ultrasound (HIFU) operating at 20 MHz is new and applicable to skin. Details of use and instrumentation are not documented. MATERIALS AND METHODS: A GLP compliant 12-week study of Göttingen minipigs (n = 3) was undertaken. Effects of HIFU treatment at different focal depths, energy levels and field size (single shot vs 5 × 5 multiple shots) were studied. Clinical scoring and histology of treated sites were made. RESULTS: High-intensity focused ultrasound showed instant and initial effects with wheal and flare responses followed by delayed inflammatory reactions associated with outer skin necrosis, depending on energy dose. HIFU treatment was tunable in the range 0.3-1.5 J, ablative at higher energy level. Transducers with deeper focal points gave more profound effects, while epidermal effects were comparable. Multiple doses of 5 × 5 shots produced stronger reactions than single dose indicating that nearby applied shots were synergistic. Recovery from single doses was faster than in multidose areas. Clinical scarring at the end point was not seen despite occasional fibrous change of dermis. Findings illustrated intended therapeutic use; no special safety issues of concern were raised. CONCLUSION: The new 20 MHz HIFU was reproducible, tunable and produced targeted effects in the outer skin, for example instant wheal and flare followed by inflammation and possibly necrosis depending on energy setting. Reactions recovered during the study with only minor findings at study end. No special safety concerns were raised. The method can be controlled and modulated, and it is ready for clinical testing of dermatological disease indications including conditions presently treated with lasers.

High-frequency (20-MHz) high-intensity focused ultrasound (HIFU) system for dermal intervention: Preclinical evaluation in skin equivalents.

BACKGROUND: High-intensity focused ultrasound (HIFU) for non-invasive treatment of a range of internal pathologies including cancers of major organs and cerebral pathologies is in exponential growth. Systems, however, operate at relatively low frequencies, in the range of 200-2000 kHz as required for deep axial penetration of the body. HIFU utilizing frequencies in excess of 15 MHz has so far not been explored, but presents an opportunity to extend the HIFU modality to target specific dermal lesions and small animal research. MATERIALS AND METHODS: A new 20-MHz HIFU system (TOOsonix ONE-R) with narrow focus corresponding to the dermis was studied in acoustic skin equivalents, for example, in a tissue-mimicking gel and in bovine liver. HIFU lesion geometry, depth, and diameter were determined. The temperature increase in the focal point was measured as a function of acoustic power and the duration of HIFU exposure. RESULTS: The system produces highly reproducible ultrasound lesions with predictable and configurable depths of 1-2 mm, thus corresponding to the depth of the human dermis. The lesion geometry was elongated triangular and sized 0.1-0.5 mm, convergent to a focal point skin deep. Focal point temperature ranged between 40 and 90°C depending on the chosen setting. Observations were confirmed ex vivo in bovine liver and porcine muscle. Variation of acoustic power and duration of exposure produced linear effects in the range of the settings studied. Thus, effects could be adjusted within the temperature interval and spatial field relevant for clinical therapy and experimental intervention targeting the dermal layer of human skin. CONCLUSION: The tested 20-MHz HIFU system for dermal applications fulfilled key prerequisite of narrow-field HIFU dedicated to cutaneous applications regarding reproducibility, geometry, and small size of the applied ultrasound lesions. Controlled adjustment of acoustic lesions within the temperature range 40-90°C qualifies the system for a range of non-ablative and ablative applications in dermatological therapy.