J M Lagarde

Centre de Recherche Pierre Fabre, Tolosa de Llenguadoc, Midi-Pyrénées, France

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Publications (39)51.59 Total impact

  • A Delalleau, G Josse, J M Lagarde
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    ABSTRACT: This paper presents a procedure for characterising the mechanical properties of skin using stochastic inverse identification. It is based on the minimisation of a cost function relative to the comparison between experimental suction experiments and their corresponding finite element models. Two different models are compared: a classical single-layer approach and a dual-layer medium which account for both the dermis and the hypodermis. Finite element results are used to construct the pre-optimisation database which is required for the inverse analysis. To compare the calculations, the entire identification is based on a dual-parameter optimisation procedure: for the single-layer approach a quadratic hyperelastic constitutive equation is used, whereas for the dual-layer medium a simple neo-Hookean potential is used. Theoretical conclusions, which are developed first, are then compared with actual case studies.
    Computer Methods in Biomechanics and Biomedical Engineering 12/2011; 15(1):83-92. · 1.39 Impact Factor
  • Journal of dermatological science 01/2010; 57(3):214-6. · 3.71 Impact Factor
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    ABSTRACT: Quantitative transverse relaxation time (T(2)) magnetic resonance (MR) imaging has been used with the aim to characterize subcutaneous adipose tissue. Protons in adipose tissue have a fast exchange behavior giving bi-component transverse relaxation processes with short and long relaxation time values depending on the tissue properties. MR images were acquired on a 1 T Siemens MR scan using a multi-spin-echo sequence. A high sensitive surface coil, enabling low noise MR images with voxel size of 10 mm(3), was used for performing accurate quantitative T(2) imaging. These acquisition parameters were determined by a preliminary study performed on an oil phantom known to be a valuable model for mimicking in vivo adipose tissue. In vivo study of the thigh adipose tissue was carried out on 30 volunteers. 20 women with various clinically diagnosed cellulite grades and 10 males, among them five showed overweight. Tissue characterization was finally performed through the analysis of the T(2) distributions. Phantom study showed that improvements in the precision in T(2) measurement are obtained at the expense of the spatial resolution. Uncertainties in T(2) measurements are three times lower by considering a region of interest of 3 x 3 pixels compared with a pixel by pixel analysis. The in vivo study showed that women groups present higher mean short T(2S) component values than men. Histogram of T(2) distribution showed that the maximum amplitude is observed at a lower value for the overweight men group. In addition, larger values around the septae were visualized on the long relaxation time images. This study shows that precise T(2) map of adipose tissue can be computed. The balance between precision and spatial resolution is examined. Preliminary results relative to tissue organization and to difference between clinical groups proves the potential of the quantitative MRI.
    Skin Research and Technology 03/2009; 15(1):45-50. · 1.41 Impact Factor
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    ABSTRACT: Corticosteroids are widely prescribed for systemic or local treatment of inflammatory autoimmune disorders. Long-term therapy is associated with side effects and causes cutaneous atrophy of the epidermis and the dermis. The present study aims to evaluate with several noninvasive techniques, the skin modifications observed during corticosteroids treatment. The potential of skin mechanical measurement and ultrasound radio frequency (RF) signal analysis are proposed as new measures more closely related to the functional impairments. Thirteen young healthy women volunteers had two applications per day on one arm of topical Clobetasol propionate 0.05% for 28 days, and they were followed for 28 days more. Skin modifications were studied by high-frequency ultrasound imaging, ultrasound RF signal analysis, optical coherence tomography and by the suction test. For all the techniques, a statistically significant change is observed with treatment. Large variations, around 30%, are observed for all techniques, but less for ultrasound imaging (10%). Dermis and epidermis thickness presented stable measurements on the nontreated zone. At the end of the study, measures returned to normal. The dynamic is mainly observed within the first 14 days of treatment and within the first 14 days after its cessation. Similar dynamics of skin modification during corticosteroid treatment was observed with very different techniques. Moreover, the potential of RF ultrasound analysis and mechanical skin measurement for characterizing skin structural and functional impairments has been evaluated.
    Skin Research and Technology 03/2009; 15(1):35-9. · 1.41 Impact Factor
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    ABSTRACT: Human immunodeficiency virus (HIV) infection generally induces lipodystrophy. For targeted treatment a better understanding of its development is necessary. The utility of high-resolution magnetic resonance imaging (MRI) is explored. The present study presents a way to visualize the adipose tissue architecture in vivo and to inspect modifications associated with the atrophy. High-resolution MRI scans with surface coils were performed on the calf and at the lumbar region of three groups of patients: HIV patients with lipoatrophy, HIV patients without lipoatrophy and healthy volunteers. All patients underwent a clinical examination. In addition, dual energy X-ray absorptiometry (DEXA) measurements were taken. On the MRI scans adipose tissue thickness and adipose nodule size were measured. Results High-resolution MRI enabled identification of a clear disorganization of adipose tissue in patients with lipoatrophy. In addition, these patients presented a very small adipose tissue thickness on the calf and a very small nodule size. led to the hypothesis that adipose tissue disorganization appears before changes in DEXA measurements or clinically visible modifications. High-resolution MRI enabled visualization in vivo of precise changes in tissue organization due to HIV lipoatrophy. This imaging technique should be very informative for better monitoring of the atrophy.
    British Journal of Dermatology 01/2009; 160(4):741-6. · 3.76 Impact Factor
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    ABSTRACT: Here we propose to quantify local temperature variations using thermal imaging to assess the effect of dermatological lasers. To quantify the temperature raise induced by laser application and to differentiate the effects of a potassium titanyl phosphate (KTP) laser and an intense pulsed light (IPL). A randomized comparative study was performed on 10 adult volunteers with symmetrical rosacea treated by KTP laser or IPL. Skin temperature measurements were performed on inclusion, immediately after laser treatment and 3 min after thermal water application, using a high-resolution (0.08 degrees C) infrared thermal video camera. KTP laser treatment induced a significant rise in local skin temperature whereas no significant change was revealed by the IPL treatment. The infrared camera is a reliable and reproducible technique that allows a follow-up of skin temperature without skin contact. Thermography using an infrared camera could potentially be applied in clinical pharmacology for inflammatory reactions or scarring processes.
    Skin Research and Technology 12/2008; 14(4):381-4. · 1.41 Impact Factor
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    ABSTRACT: Background. Nonablative remodeling has been recently proposed as an alternative to CO2 and Er:YAG resurfacing.Objective. To evaluate the efficacy and safety of a 1540 nm Er:glass laser with contact cooling in nonablative skin remodeling, focused on perioral and periorbital rhytides.Methods. Sixty patients (mean age 47 years), Fitzpatrick skin types I–IV were treated four times over 6-week intervals. Patients were evaluated using digital photographs, histology, ultrasound imaging, and profilometry with silicone imprints in order to quantitate the degree of clinical improvement.Results. All subjects reported subjective improvement in the quality and visual aspect of their skin. This was confirmed by a 40.2% reduction of anisotropy (P < .001) 6 weeks after the fourth treatment. Ultrasound imaging demonstrated a 17% increase of dermis thickness (P < .005). Biopsy specimens showed evidence of new collagen formation.Conclusion. This study has clearly demonstrated that irradiation with 1540 nm Er:glass laser can lead to new collagen formation, dermis thickening, reduction of anisotropy of the skin, and clinical improvements. The lack of adverse effects confirmed that this 1540 nm laser emitting in a pulsed mode coupled with an efficient cooling system is safe.
    Dermatologic Surgery 07/2008; 27(9):799 - 806. · 1.87 Impact Factor
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    ABSTRACT: Cutaneous fibrosis is the quite mandatory sequela after a breast cancer treated by radiotherapy and it induces more or less important functional troubles. The LPG technique is a technique of mechanical massage that allows skin mobilization by folding/unfolding. The aim of this study was to evaluate the changes on irradiated skin before and after LPG treatment by clinical and skin replica analysis. Twenty women, 43-55 years old, who had been treated from 6 to 16 months before, for breast cancer with a conservative surgery and radiotherapy, had been enrolled in the trial. They were divided into two groups after randomization: the first group was LPG treated three times a week for 1 month; the second group was only placed under medical supervision. The clinical criteria studied were systematically studied before (T0), at the end of treatment (T1) and 1 month after the end of treatment (T2): pain, itching, skin dryness, erythema, skin infiltration, feeling of tightness and of induration of the skin. Softening of the skin was assessed at T1 and T2. Cutaneous replica was performed on the internal upper 1/4 of each breast with silicone material before, after and 1 month later after the end of the treatment. After polymerization, the replica was stored and then blindly analyzed by image analysis software. The following parameters were systematically measured: average skin roughness, average of wrinkles' depth and residual length, wrinkle number and the space between them. Clinically, the LPG treatment induced a decrease of erythema (10% of the patients vs. 40% before treatment), a decrease of pain and pruritus (10% vs. 20% and 40%, respectively) and a decrease of the feeling of induration of the skin (10% of the patients vs. 70% before treatment). Furthermore, a skin-softening sensation was noted by seven patients vs. one in the control group. Replica shows an increase of roughness and of furrow depth without any change in the residual length and an increase in the space between the wrinkles, whose number decreases. This study confirms the impact of the clinical sequelae induced on skin after radiotherapy and shows improvement of the clinical signs after treatment by the LPG technique. The latter induces changes of micro relief, suggesting a softening effect on the skin. These preliminary results have to be confirmed on a more important group of patients.
    Skin Research and Technology 03/2008; 14(1):71-6. · 1.41 Impact Factor
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    ABSTRACT: The human skin is a material that exhibits complex behaviors. However, the determination of its mechanical characteristics is a paramount goal for dermatology (pathologies), and for the cosmetics industry (skin ageing). In this study, we propose a new method for the determination of mechanical characteristics of human skin in vivo. This identification is based on experimental results that are obtained with the extensometry test. Its principle is to carry out a tensile test using two devices pasted to the skin. Then, experimental results are compared to those extracted from finite element models of this test. This comparison is made through an inverse method that uses a scheme of Extended Kalman filters. It enables to determine representative elastic mechanical parameters of this tissue. We introduce here experimental devices, the inverse method that we developed, and different analyses of phenomena that are related to cutaneous tissues stressed in that way.
    Wear 01/2008; 264(5-6):405-410. · 1.26 Impact Factor
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    ABSTRACT: In this article, we present an inverse method for the identification of the mechanical properties of human skin, a complex multi-layered organ which has been studied in vivo using a suction deformation technique. To identify the required properties, experimental results were compared to finite element solutions of the test, with the assumption that skin behaves as a single isotropic hyperelastic layer. The inverse method used in this article is based on that of the extended Kalman filters principle, with two modifications of this standard formulation for use in skin analysis. The modified formulation was then tested using Finite Element Method (FEM) simulated mechanical data and also with a study of linear and nonlinear theoretical problems. The results of the new formulation were also compared with the Gauss–Newton, recursive least square and Kalman smoother approaches. Finally, the reliability of the method was tested on a case study.
    Inverse Problems in Science and Engineering 01/2008; 16(3):325-347. · 0.75 Impact Factor
  • A. Delalleau, G. Josse, J.M. Lagarde
    Computer Methods in Biomechanics and Biomedical Engineering 01/2008; Vol.(1):81-82. · 1.39 Impact Factor
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    ABSTRACT: Experimental studies of wound healing lack methods for standardized wounding and in situ depth assessment. Consequently, in this pilot study, an Erbium (Er):YAG laser has been used for wound induction with a non-invasive 3-D imaging technique as an alternative to histology. Erbium:YAG ablation of human skin ex vivo was performed with total fluences of 10, 50 and 200 J/cm(2), removing the stratum corneum, epidermis/papillary dermis and deeper dermis, respectively. Wound depth was measured with the 3-D method and histologically. Wound depth was proportional to fluence for both techniques : 3-D, 17.7+/-1.7, 43.9+/-16 and 245.2+/-61 microm; histology, 14.6+/-1.7, 50.6+/-11.6 and 238+/-102 microm, respectively. The 3-D technique compares well with and is an improvement on histological measurement, providing true wound depth measurement, avoiding shape changes inherent with histology. Furthermore, the Er:YAG laser is a highly appropriate means of wound induction due to its rapidity and precision.
    Skin Research and Technology 12/2007; 13(4):399-405. · 1.41 Impact Factor
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    ABSTRACT: In recent years, increasing use of injectable resorbable fillings has been reported for facial wrinkle treatment. However, the physiological processes involved such as the localization and subsequent diffusion of the injected product in skin tissues are poorly documented. This may be noninvasively achieved using quantitative magnetic resonance imaging (MRI), which is duly presented in this pilot study. Hyaluronic acid (HA) was injected intradermally in the forearm of a young male volunteer. High-resolution MRI scans using a surface antenna were performed just after injection, and after 2, 4 and 9 months. Morphological images were compared with transverse relaxation time (T(2)) images computed from a pixel-by-pixel analysis. On high-resolution morphological MR images the HA injection is barely visible, but with quantitative MRI the zone of injection is clearly seen. This is due to HA having a distinctly different transverse relaxation time, T(2) approximately 600 ms, compared with dermal and hypodermal tissues, 35 and 80 ms, respectively. These preliminary results demonstrate the ability of the T(2) images for in vivo visualization of the filler agent and also for characterization of tissue modifications. In addition, the diffusion and progressive degradation of the filler agent can be monitored by T(2) measurements over time.
    Skin Research and Technology 12/2007; 13(4):385-9. · 1.41 Impact Factor
  • Computer Methods in Biomechanics and Biomedical Engineering 01/2007; 10(sup1):195-196. · 1.39 Impact Factor
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    ABSTRACT: Measuring spin-spin relaxation times (T2) by quantitative MR imaging represents a potentially efficient tool to evaluate the physicochemical properties of various media. However, noise in MR images is responsible for uncertainties in the determination of T2 relaxation times, which limits the accuracy of parametric tissue analysis. The required signal-to-noise ratio (SNR) depends on the T2 relaxation behaviour specific to each tissue. Thus, we have previously shown that keeping the uncertainty in T2 measurements within a limit of 10% implies that SNR values be greater than 100 and 300 for mono- and biexponential T2 relaxation behaviours, respectively. Noise reduction can be obtained either by increasing the voxel size (i.e., at the expense of spatial resolution) or by using high sensitivity dedicated surface coils (which allows us to increase SNR without deteriorating spatial resolution in an excessive manner). However, surface coil sensitivity is heterogeneous, i.e., it--and hence SNR--decreases with increasing depth, and the more so as the coil radius is smaller. The use of surface coils is therefore limited to the analysis of superficial structure such as the hypodermic tissue analysed here. The aim of this work was to determine the maximum limits of spatial resolution and depth compatible with reliable in vivo T2 quantitative MR images using dedicated surface coils available on various clinical MR scanners. The average thickness of adipose tissue is around 15 mm, and the results obtained have shown that obtaining reliable biexponential relaxation analysis requires a minimum achievable voxel size of 13 mm3 for a conventional volume birdcage coil and only of 1.7 mm3 for the smallest available surface coil (23 mm in diameter). Further improvement in spatial resolution allowing us to detect low details in MR images without deteriorating parametric T2 images can be obtained by image filtering. By using the non-linear selective blurring filter described in a previous work, the voxel size was reduced to 0.8 mm3, allowing us to detect microstructures such as fibrous septae while preserving precision in T2 measurements. This paper provides practical information allowing us to perform reliable T2 quantitative MR micro images. High resolution imaging with dedicated surface coils, which is only well-suited to near surface organs, might lead to highly valuable results in this context, especially to analyse the hypodermis involved in the lipodystrophy seen in patients with human immuno-deficiency virus (HIV).
    Physics in Medicine and Biology 07/2006; 51(11):2843-55. · 2.70 Impact Factor
  • D Black, J Boyer, J M Lagarde
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    ABSTRACT: The severity of scaling disorders can be evaluated objectively using the D-Squame technique coupled with image analysis. The parameters of scaling derived using this approach need to be clinically relevant and should have greater discrimination than visual grading. Improvements to an existing method that fulfil these requirements are presented. Three scaling parameters were calculated using image analysis of digitized video-captured images of obliquely lit D-Squame samples. These parameters were compared to clinical scores of scaling made by five observers from photographs of the same areas sampled with D-Squame. In addition, two clinical studies were carried out to assess moisturizer effects on different degrees of xerosis, and to compare two different moisturizer preparations. The three scaling parameters gave correlation coefficients, r, between 0.6 and 0.75 when compared with global clinical scores of scaling. Significant reductions in all parameters were observed with 2 weeks of moisturizer use on lower leg skin with marked xerosis compared to an untreated control. The same moisturizer had a similar effect on milder xerosis of the forearm, and showed a greater decrease than a moisturizer with lower glycerol content. Increases in skin hydration, as measured with a corneometer, were also seen in both clinical studies, and corresponded well with D-Squame results. Differences in the degrees of scaling between these two anatomical sites were also detected with this technique. In a previous publication, the same technique was shown to be repeatable and reproducible; in the current article its correlation with clinical observations of scaling or flaking skin has been demonstrated.
    International journal of cosmetic science 03/2006; 28(1):35-44.
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    ABSTRACT: Quantitative MR imaging is a potential tool for tissue characterization; in particular, proton density and proton relaxation times can be derived from MR signal analysis. However, MR image noise affects the accuracy of measurements and the number of tissue parameters that can be reliably estimated. Filtering can be used to limit image noise; however this reduces spatial resolution. In this work we studied, using both simulations and experiments, a filter called a 'selective blurring filter'. Compared to other classical filters, this filter achieves the best compromise between spatial resolution and noise reduction. The filter was specifically used to reliably determine the bi-component transverse relaxation of protons in adipose tissue. Long and short relaxation times and the relative proton fraction of each component were obtained with a degree of uncertainty of less than 10% and an accuracy of 95%.
    Physics in Medicine and Biology 09/2005; 50(16):3755-72. · 2.70 Impact Factor
  • J M Lagarde, C Rouvrais, D Black
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    ABSTRACT: Most studies of how the relief of the skin surface changes on ageing are based solely on topography, and a few have taken into account anisotropy parameters. However, the calculation of these parameters is often carried out manually and as the techniques of data acquisition have progressed rapidly, a certain degree of obsolescence has been reached. It is for this reason that we have undertaken a similar study but with more advanced equipment. The Dermatop system analyses the relief of Silflo negative prints of the skin surface. It is based on the projection of interference fringes and phase shift and provides surface parameters and not profiles. In addition, the Toposurf software enables image processing and the precise and automatic calculation of the topography parameters (roughness, developed surface area and peak-trough amplitude) and anisotropy (level of anisotropy and furrow density). These parameters were studied on the forearm and temple of 40 men and 40 women evenly distributed into two groups: the first including subjects aged 25-35 years and the second 50-65 years. Roughness of both sites increases with age, independent of sex, but to a lesser extent in women than in men. The developed surface area and the peak-trough amplitude increase significantly with age irrespective of the site and the sex. The level of anisotropy increases with age, in both men and women, on the forearm and the temple, the site more exposed to light being more affected. The density of the furrows decreases with age in both sexes and both sites but with a greater increase for the temple, which is more exposed to solar ageing. The study of these new parameters will allow objective evaluation of the action of topical dermatological and cosmetic treatment, and new techniques in plastic surgery (e.g. laser resurfacing), and will enable the accurate follow-up of certain pathologies.
    Skin Research and Technology 06/2005; 11(2):110-9. · 1.41 Impact Factor
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    ABSTRACT: As remodeling is getting more popular with patients, long-term studies are becoming necessary. The aim of this 35-month clinical study was to evaluate the long-term benefits obtained using a 1540-nm Er:glass laser for non-ablative remodeling of perioral and periorbital rhytids. The role of maintenance treatments was also investigated. Eleven women with periorbital and perioral rhytids underwent a series of five treatments at 6-week intervals with an Er:glass laser. Five patients subsequently received two maintenance retreatments and six did not. The maintenance treatments were performed at 14 and 20 months. Silicone imprints were performed to measure anisotropy before treatment, at 6 months, at 14 months and at 35 months. Patient self-evaluation/questionnaire was also done to assess adverse effects and subjective clinical improvement. For all 11 patients, the percentage of anisotropy reduction was 41.21% at 6 months, 51.76% at 14 months and 29.87% at 35 months. No adverse effects were noted. Patient satisfaction was high at the end of the evaluation. Retreated patients were more satisfied than non-retreated ones. However, there was no difference in the anisotropy factor between the two groups. Treatment of facial rhytids with a non-ablative 1540-nm Er:glass laser system can produce benefits that persist over 2 years after the last treatment.
    Journal of Cosmetic and Laser Therapy 12/2004; 6(3):126-30. · 0.86 Impact Factor
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    ABSTRACT: Nonablative remodeling has been recently proposed as a new, no-down-time, anti-aging treatment. Objective. The objective was to evaluate the efficacy and safety of nonablative skin remodeling with a 1540-nm Er:Glass laser on neck lines and forehead rhytids. Twenty female patients (mean age 45 years) were enrolled. Skin thickness and mechanical properties were measured before the first treatment, 1 month after the third treatment, 1 month after the fifth treatment, and 3 months after the fifth treatment. All patients reported an improvement in both skin tone and texture. Using ultrasound imaging, dermal thickness of neck and forehead increased, respectively, by 70+/-13 microm (p<0.001) and 110+/-19 microm (p<0.003). A dramatic increase of initial stress of the forehead skin (firmness) was obtained, from 7.62+/-3.68 before treatment to 16.68+/-7.44 3 months after the fifth treatment (p<0.0002). No immediate or late adverse effects were noted throughout the treatment regimen. This study demonstrates that irradiation with a 1540-nm Er:Glass laser emitting in a pulsed mode and coupled with an efficient contact cooling system increases dermal thickness and firmness, leading to a clinical improvement of neck lines and forehead rhydits.
    Dermatologic Surgery 06/2004; 30(6):872-9; discussion 879-80. · 1.87 Impact Factor

Publication Stats

538 Citations
51.59 Total Impact Points

Institutions

  • 1995–2011
    • Centre de Recherche Pierre Fabre
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2009
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2005–2009
    • Paul Sabatier University - Toulouse III
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2004
    • Clinique Saint-Jean Languedoc
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2000
    • University of Barcelona
      Barcino, Catalonia, Spain