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Iltefat Hamzavi

Publications and source records attributed to Iltefat Hamzavi.

9 recordsLinked to original sources
PubMed2006

Monte Carlo simulation of cutaneous reflectance and fluorescence measurements--the effect of melanin contents and localization.

Melanin content and distribution in skin were studied by examining a patient with white, brown and blue skin tones expressed on skin affected by vitiligo. Both diffuse reflectance and autofluorescence spectra of the three distinction skin sites were measured and compared. Monte Carlo simulations were then performed to help explain the measured spectral differences. The modeling is based on a six-layer skin optical model established from published skin optical parameters and by adding melanin content into different locations in the model skin. Both the reflectance and fluorescence spectra calculated by Monte Carlo (MC) simulation were approximately in agreement with experimental results. The study suggests that: (1) trichrome vitiligo skin may be an ideal in vivo model for studying the effect of skin melanin content and distribution on skin spectroscopy properties. (2) Based on the skin optical model and MC simulation, the content and distribution of melanin in skin, or other component of skin could be simulated and predicted. (3) Both reflectance and fluorescence spectra provided information about superficial skin structures but fluorescence spectra are capable of providing information from deeper cutaneous structures. (4) The research method, including the spectral ratio method, the method of adding and modifying the melanin content in skin optical models, and MC simulation could be applied in other non-invasive optical studies of the skin.

Computer Simulation↗
PubMed2006

Photoadaptation: a path toward rational phototherapy protocols.

Photoadaptation is defined as the diminished future response to equivalent doses of irradiation. It is most often estimated in vivo by looking at changes in the minimal erythema dose with subsequent doses of UV radiation. Although photoadaptation's mechanism of action is poorly understood, Palmer et al. help clarify the clinical significance of photoadaptation for the dosimetry of UV-based phototherapy.

Adaptation, Physiological↗
PubMed2006

Spectroscopic assessment of dermal melanin using blue vitiligo as an in vivo model.

BACKGROUND: Spectroscopic methods have been used to analyze in vivo melanin in the past but the specific effect of melanin depth on autofluorescence and reflectance spectroscopy has not been determined. In patients with blue vitiligo, three distinctive clinicopathologic patterns are present: (1) normal skin with normal epidermal melanin pigmentation (2), skin of blue vitiligo with dermal melanin pigmentation, and (3) tissue of regular vitiligo with no melanin pigmentation. Blue vitiligo may thus serve as an in vivo model to assess dermal pigment using spectroscopic techniques. OBJECTIVES: To evaluate the reflectance and autofluorescence spectra of a patient with blue vitiligo in order to assess the effect of melanin pigmentation and its localization on the optical properties of the skin. METHODS: The blue-gray, normal and depigmented lesions of a patient with blue vitiligo were analyzed using reflectance and fluorescent spectroscopy. The condition was likely induced by a phototoxic reaction in a patient with pre-existing vitiligo. These data were then correlated to the histologic and electron microscopic findings present in the various types of lesions. RESULTS: Reflectance spectroscopy detected little difference in spectral shape between skin sites affected by blue vitiligo vs. vitiligo. Autofluorescence spectroscopy detected an apparent difference between the two types of lesions, with the blue-gray lesions (blue vitiligo) showing lower fluorescence intensity and spectral maximum position red-shifted compared with regular vitiligo, whereas regular vitiligo showed more intense hemoglobin absorption than the blue vitiligo. CONCLUSIONS: Dermal melanin present in blue vitiligo can be well characterized by autofluorescence spectroscopy, while little difference in reflectance spectral shape exists between vitiligo and blue vitiligo. Thus, autofluorescence spectroscopy may better identify deeper structures in skin tissue, such as melanin, than reflectance spectroscopy.

Humans↗
PubMed2005

Narrow-band UVB induces apoptosis in human keratinocytes.

Narrow-band ultraviolet (NB-UVB) phototherapy emits mostly 311/312 nm light and is commonly used in the treatment of inflammatory skin disorders. As a source of UVB irradiation, NB-UVB causes apoptosis in T lymphocytes but its effects on keratinocytes are unknown. Herein, we have investigated the ability of NB-UVB to induce apoptosis in keratinocytes. Two types of human keratinocytes, primary and immortalized, were exposed to NB-UVB and broad-band UVB (BB-UVB; 315-280 nm) and tested for apoptosis. Both UVB light sources induced apoptosis in keratinocytes as determined by the presence of DNA ladders, although NB-UVB required approximately ten fold higher doses; NB-UVB (1000 mJ/cm2) and BB-UVB (125 mJ/cm2). By comparison, lower doses of NB-UVB (750 mJ/cm2) induced apoptosis in T lymphocytes, suggesting cell type specificity for NB-UVB induced apoptosis. Approximately, 50% or more of the cells underwent apoptosis when exposed to NB-UVB or BB-UVB as revealed by TUNEL assay. Electron micrographs showed that NB-UVB irradiated keratinocytes contained marked chromatin condensation, extensive cytoplasmic vacuolization and fragmentation of the nuclear envelope. Furthermore, Western blot analysis confirmed the presence of activated products of caspase 3 in keratinocytes that received apoptotic doses of NB-UVB. This study defines conditions by which NB-UVB irradiation causes apoptosis in keratinocytes.

Apoptosis↗
PubMed2005

Using light in dermatology: an update on lasers, ultraviolet phototherapy, and photodynamic therapy.

Indications for light-based treatments, such as lasers, UV phototherapy, and photodynamic therapy, are rapidly increasing within the arena of skin disorders. Physicians can remain current in their understanding of these modalities if they understand a few basic principles outlined in this article. Once these concepts are understood, all the rapid advances can be kept in perspective and physicians can apply the most appropriate technology to the care of their patients while informing them about the limitations of overmarketed but poorly proved strategies.

Humans↗
PubMed2004

Photodynamic therapy of multiple nonmelanoma skin cancers with verteporfin and red light-emitting diodes: two-year results evaluating tumor response and cosmetic outcomes.

BACKGROUND: Efficient treatment of patients with multiple synchronous nonmelanoma skin cancers represents a therapeutic challenge. OBJECTIVE: To study the safety and efficacy of photodynamic therapy (PDT) with verteporfin and red light in the treatment of multiple nonmelanoma skin cancers. DESIGN: Open-label, randomized, multicenter, dose-ranging phase 2 study conducted at 4 North American university-based dermatology clinics. PATIENTS: Fifty-four patients with 421 multiple nonmelanoma skin cancers including superficial and nodular basal cell carcinoma and squamous cell carcinoma in situ (Bowen disease). METHODS: A single intravenous infusion of 14 mg/m(2) of verteporfin followed 1 to 3 hours later by exposure of tumors to 60, 120, or 180 J/cm(2) of red light (688 +/- 10 nm) from a light-emitting diode panel. MAIN OUTCOME MEASURES: Pathologic response of treated sites was assessed at 6 months. Clinical and cosmetic responses were assessed and graded at 6 weeks, 3 months, and 6 months after verteporfin PDT, with optional follow-up visits at 12, 18, and 24 months. RESULTS: The histopathologic response, defined as absence of tumor on biopsy specimens 6 months after verteporfin PDT, ranged from 69% at 60 J/cm(2) to 93% at 180 J/cm(2). At 24 months of follow-up (276 tumors in 31 patients), the clinical complete response rate ranged from 51% at 60 J/cm(2) to 95% at 180 J/cm(2). No significant systemic adverse events were observed; most events occurred at the treated tumor sites and included events such as pain. Overall, 65% (95% confidence interval, 58%-71%) of tumors were judged to have good to excellent cosmesis at 24 months. CONCLUSION: A single course of verteporfin PDT showed treatment benefit for patients with multiple nonmelanoma skin cancers.

Adult↗
PubMed2004

Parametric modeling of narrowband UV-B phototherapy for vitiligo using a novel quantitative tool: the Vitiligo Area Scoring Index.

BACKGROUND: There is currently no quantitative tool for evaluating vitiligo treatment response using parametric methods. OBJECTIVE: To develop and apply a simple clinical tool, the Vitiligo Area Scoring Index (VASI), to model the response of vitiligo to narrowband UV-B (NB-UV-B) phototherapy using parametric tests. DESIGN: Prospective, randomized, controlled, bilateral left-right comparison trial. SETTING: North American tertiary care, university-affiliated phototherapy center. PATIENTS: Patients older than 18 years with stable vitiligo involving at least 5% of their total body surface in a symmetric distribution. INTERVENTION: Treatment with NB-UV-B was given 3 times a week to half of the body on all patients for either 60 treatments or 6 months. The contralateral side served as a no-treatment control. MAIN OUTCOME MEASURE: Repigmentation was assessed using the VASI, which was based on a composite estimate of the overall area of vitiligo patches at baseline and the degree of macular repigmentation within these patches over time. The VASI was validated separately against physician and patient global assessments. The overall reductions in VASI for NB-UV-B and control groups were modeled by multilevel regression with random effects and compared parametrically. RESULTS: The VASI scoring correlated well with both patient and physician global assessments (P =.05 and P<.001, respectively, using ordinal logistic regression). The extent of repigmentation after 6 months on the treated side was 42.9% (95% confidence interval, 26.7%-59.0%) vs 3.3% (95% confidence interval -19.3% to 30.0%) on the untreated side (P<.001). A significant difference between control and NB-UV-B groups was apparent within the first 2 months of therapy. The legs, trunk, and arms were much more likely to repigment than the feet and hands. CONCLUSIONS: The VASI is a quantitative clinical tool that can be used to evaluate vitiligo parametrically. Patients treated with NB-UV-B can be expected to achieve approximately 42.9% repigmentation of their vitiligo after 6 months of treatment, with the greatest response being achieved over the trunk and nonacral portions of the extremities.

Adult↗
PubMedDate not supplied

Cutaneous melanin exhibiting fluorescence emission under near-infrared light excitation.

Under ultraviolet and visible light excitation, melanin is essentially a nonfluorescent substance. This work reports our study on near-infrared (NIR) fluorescence properties of melanins, and explores potential applications of NIR fluorescence techniques for evaluating skin disorders involving melanin. The NIR fluorescence spectrum is obtained using a fiber optic NIR spectrometer under 785-nm laser excitation. In vitro measurements are performed on synthetic dihydroxyphenylalanine (DOPA) melanin, melanin extracted from Sepia ink sacs, human hair, animal fur, and bird feathers. Paired spectral comparisons of white and black skin appendages show that melanization of hair, fur, or feathers more than doubles the NIR fluorescence. In vivo NIR autofluorescence of normal dorsal and volar forearm skin of 52 volunteers is measured. Dorsal forearm skin, which is darker than volar skin, exhibits significantly greater NIR fluorescence. Patients with vitiligo (n=4), compound nevus (n=3), nevus of Ota (n=1), superficial spreading melanoma (n=3), and postinflammatory hyperpigmentation (n=1) are also evaluated. NIR fluorescence is greater within the lesion than the surrounding normal skin for all these conditions except vitiligo, where the converse was true. The observed melanin NIR fluorescence provides a new approach to in vitro and in vivo melanin detection and quantification that may be particularly useful for evaluating pigmented skin lesions.

Animals↗