Biomedical subjects
Publications and source records attributed to C Dierickx.
A systematic and logical approach for laser hair removal demands an understanding of its biologic and physical bases. This article presents an overview of hair anatomy and physiology followed by a mathematically nonrigorous review of tissue optics and thermal responses to laser irradiation. The reader is provided with a step by step approach to laser hair removal.
The tremendous demand for removal of unwanted hair has led to the development of a wide range of noninvasive, user-friendly laser and light source systems; however, despite considerable advances in this field, these devices still have the potential to cause injury when used improperly. It is important to follow precise treatment guidelines in order to attain optimal results. This article gives an overview of the currently available lasers and light sources. It focuses on the practical aspect of laser hair removal by discussing patient selection, safety precautions, techniques using the different systems, pre- and post-laser treatment care, proper treatment endpoints, expected outcome, and possible side-effects and complications.
Skin precooling can be used to reduce epidermal thermal damage in laser procedures (such as hair removal) where the target structures are located up to several millimetres below the skin surface. We have developed and experimentally verified a computational model that describes contact precooling of a multilayered skin structure prior to laser irradiation. The skin surface is assumed to be brought into thermal contact with a cold plate made of material with a high thermal conductivity. The approximate analytical solution for the skin temperature is obtained by considering the plate as a local heat sink. The time evolution of temperature (in both the skin and the plate) is simulated numerically to yield the optimal cooling parameters. To experimentally verify the numerical results of the model, we performed direct measurements of skin temperature for contact cooling with a sapphire plate held at several different temperatures in the range +10 to -30 degrees C.
BACKGROUND: Although many temporary treatments exist for hirsutism and hypertrichosis, a practical and permanent hair removal treatment is needed. OBJECTIVE: Our purpose was to study the use of normal-mode ruby laser pulses (694 nm, 270 microseconds, 6 mm beam diameter) for hair follicle destruction by selective photothermolysis. METHODS: Histologically assessed damage in ex vivo black-haired dog skin after the use of different laser fluences was used to design a human study; 13 volunteers with brown or black hair were exposed to normal-mode ruby laser pulses at fluences of 30 to 60 J/cm2, delivered to both shaved and wax-epilated skin sites. An optical delivery device designed to maximize light delivery to the reticular dermis was used. Hair regrowth was assessed at 1, 3, and 6 months after exposure by counting terminal hairs. RESULTS: Fluence-dependent selective thermal injury to follicles was observed histologically. There was a significant delay in hair growth in all subjects at all laser-treated sites compared with the unexposed shaven and epilated control sites. At 6 months, there was significant hair loss only in the areas shaved before treatment at the highest fluence. At 6 months, four subjects had less than 50% regrowth, two of whom showed no change between 3 and 6 months. Transient pigmentary changes were observed; there was no scarring. CONCLUSION: Selective photothermolysis of hair follicles with the normal-mode ruby laser produces a growth delay consistent with induction of prolonged telogen with apparently permanent hair removal in some cases.
Fifteen patients with erythematous/hypertrophic scars and 11 patients with postinflammatory hyperpigmentation were treated with a flashlamp pumped pulsed-dye laser at 585 nm or a flashlamp pulsed-dye laser at 510 nm. An average of 1.8 treatments resulted in an average improvement of 77 percent. Forty-seven percent of the patients had 100 percent improvement after one to three treatments. Eleven patients with postinflammatory hyperpigmentation were treated with the flashlamp pumped pulsed-dye laser at 510 nm with a pulse width of 300 ns. There was an average of 80 percent improvement with 1.45 treatments. Forty-five percent of the patients had 100 percent improvement after one or two treatments. The pathophysiology of postoperative scarring is reviewed. Theoretical reasons for the efficacy of laser treatment are detailed.
The application of facial cosmetic tattoos (eyeliner, lipliner, and rouge) has become popular over the past five years and has resulted in an increasing number of patients requesting removal of these permanent cosmetics. Poor positioning or misapplication of the tattoo pigment has been the most common reason for requesting removal. Because of the almost inevitable probability of scarring, removal of these facial tattoos has been difficult at best. We report the successful removal of facial cosmetic tattoos in ten different patients with the use of five different lasers. We have found the superpulsed CO2 laser and the Q-switched alexandrite laser to be effective in removal of black tattoo pigment. The alexandrite laser is effective without causing scarring, and the CO2 laser is extremely precise and provides the capability of removing tattoo pigment between eyelash or eyebrow hairs without damaging the hair follicles. Both the argon laser and the flashlamp pumped dye laser reacted with red tattoo pigment and offered some improvement but were not ideally suited for tattoo removal. However, the flashlamp pumped dye laser for pigment was very effective in removing red tattoo pigment possibly because of its short pulse width (300 ns) in addition to its appropriate wavelength. The combination of these three lasers (super-pulsed CO2, alexandrite, and flashlamp pigment lasers) is very effective in removing black and red (or shades thereof) facial tattoos. Caution must be taken to determine the presence of flesh-colored tattoo pigment, as this pigment (FE2O3) will reduce to black (FeO) upon laser impact.
We reviewed 20 patients with a painful massive, irreparable rotator cuff tear, classified as type III according to Gerber (11). They were all treated with an open partial acromionectomy, an attempt for primary repair and an anterior deltoid muscle inlay flap, as described by Apoil and Augereau. After minimum follow-up of 12 months (average 23.5 months) 17 out of 20 patients were satisfied and better, and the UCLA shoulder scoring (9) improved from an average of 9.35 to an average of 25.7 (max. of 35). Pain and function improved in all patients, with an average of 4.35 and 4.00 points respectively. Active forward flexion improved in 17, and strength of forward flexion improved in 15 patients. Our results were compared with those of Apoil and Augereau, and with the results obtained by other authors after open or closed acromioplasty and cuff tear debridement. This retrospective study tries to give a critical view of this French technique, and concludes that, although no negative effect can be demonstrated by the use of a deltoid muscle flap, a definite advantage cannot be proved.
Explore the source record for details and available documents.
Explore the source record for details and available documents.