Thermal damage patterns of diode hair-removal lasers according to various skin types and hair densities and colors: a simulation study.

BACKGROUND AND OBJECTIVE: It is important to prevent unwanted side effects of diode hair-removal lasers especially in dark skin tones. This study simulates the thermal damage patterns caused by diode hair-removal lasers in different skin types, hair colors, and hair densities. MATERIALS AND METHODS: LITCIT software has been used with the tissue modeled as two components, the skin and the hair. The absorption coefficients of various skin types (f(mel)=5%, 10%, 15%, and 20%), laser parameters, and optothermal properties of tissue were inputs. RESULTS: For all skin types there was a significant unwanted thermal damage to the epidermis as a result of fluence increase. Using longer pulse durations is accompanied by effective thermal damage to the hair follicle, while preserving the epidermis in skin types II and III, an effect not achieved in darker skins. Regardless of pulse duration, when the distance between hair follicles is ≤ 0.5 mm, there is a significant increase in thermal damage to interfollicular epidermis with high fluences compared with lower hair densities (interfollicular space ≥ 1 mm). In lighter hairs, while using longer pulse durations, higher fluences are needed in order to obtain the same level of thermal damage in the hair follicle as shorter pulse widths. CONCLUSIONS: In lighter skin types, lengthening the pulse duration of diode lasers (up to 400 ms) increases efficacy while preserving epidermis from unwanted thermal damage. However, it is necessary to use lower fluences while using longer pulse duration to avoid irreversible thermal damage to epidermis in darker tones, as is also true for locations with higher hair densities.

Histological evaluation of drill fragments obtained during osteoid osteoma radiofrequency ablation.

OBJECTIVE: Osteoid osteoma (OO) is a benign bone tumor diagnosed mainly on the basis of the patient's history and radiological data. Histological evaluation may not be available before treatment. The aim of this study was to assess the diagnostic value of a histological evaluation of the bone fragments obtained during radiofrequency ablation (RFA). MATERIALS AND METHODS: During a 2-year period, 39 patients diagnosed clinically with OO were entered into this study. The procedure was performed under computed tomography (CT) guidance. An 11-gauge needle was initially placed as a coaxial guide. After drill removal, RFA was performed. Bone fragments collected from the drill were examined by two experienced pathologists, independently. RESULTS: There was strong association between pathologists' reports (P <0.001). In 27 cases (69.2%) this diagnosis was confirmed pathologically. No significant relationship was found between nidus diameter and positive histological findings (P = 0.35). CONCLUSION: Histological confirmation of OO based on drill fragments is similarly frequent as previously reported for standard bone biopsy.

Radiofrequency ablation of osteoid osteoma in atypical locations: a case series.

BACKGROUND: Osteoid osteoma has a nidus surrounded by sclerotic bone with a size usually less than 20 mm. Its diagnosis is made on typical presentation of nocturnal pain and imaging findings. Excision of the niduses, which are often small and difficult to precisely identify, sometimes may result in resection of surrounding normal bone. Minimally invasive percutaneous treatments have been used to try to minimize resection of normal bone. Although minimally invasive radiofrequency ablation generally relieves pain, its ability to relieve pain is less well known in locations other than lower extremity long bones. QUESTIONS/PURPOSES: We determined the pain relief and complication rates after radiofrequency ablation of osteoid osteomas presenting in atypical locations and followed patients to assess possible recurrence or late complications. PATIENTS AND METHODS: We retrospectively reviewed 21 patients with osteoid osteomas in unusual locations (eg, hip, radioulnar joint, and proximal phalanx) in whom we used radiofrequency ablation. Postoperative activities were not restricted for any of the patients. We assessed the time for patients to become symptom free, their activity status, and possible recurrence or complications. The minimum clinical followup was 12 months (mean, 27.8 months; range, 12-37 months). RESULTS: All patients became symptom free within 24 hours to 1 week. During followup, none of the patients experienced recurrence or any major complications. CONCLUSIONS: Radiofrequency ablation for osteoid osteomas in unusual locations reliably relieves pain with few complications and recurrences at short-term followup. LEVEL OF EVIDENCE: Level IV, case series. See Guidelines for Authors for a complete description of level of evidence.

Relieving pain in minor aphthous stomatitis by a single session of non-thermal carbon dioxide laser irradiation.

This randomized controlled clinical trial was designed to evaluate the efficacy of single-session, non-thermal, carbon dioxide (CO(2)) laser irradiation in relieving the pain of minor recurrent aphthous stomatitis (miRAS) as a prototype of painful oral ulcers. Fifteen patients, each with two discrete aphthous ulcers, were included. One of the ulcers was randomly allocated to be treated with CO(2) laser (1 W of power in de-focused continuous mode) and the other one served as a placebo. Before laser irradiation, a layer of transparent, non-anesthetic gel was placed on both the laser lesions and the placebo lesions. The patients were requested to grade their pain on a visual analog scale up to 96 h post-operatively. The reduction in pain scores was significantly greater in the laser group than in the placebo group. The procedure itself was not painful, so anesthesia was not required. Powermetry revealed the CO(2) laser power to be 2-5 mW after passing through the gel, which caused no significant temperature rise or any visual effect of damage to the oral mucosa. Our results showed that a low-intensity, non-thermal, single-session of CO(2) laser irradiation reduced pain in miRAS immediately and dramatically, with no visible side effects.