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J M Lagarde

Publications and source records attributed to J M Lagarde.

14 recordsLinked to original sources
PubMed2006

High spatial resolution quantitative MR images: an experimental study of dedicated surface coils.

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).

Artifacts↗
PubMed2005

A post-processing method for multiexponential spin-spin relaxation analysis of MRI signals.

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%.

Adipose Tissue↗
PubMed2005

Topography and anisotropy of the skin surface with ageing.

BACKGROUND/PURPOSE: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Adult↗
PubMed2003

Radiation-induced skin fibrosis after treatment of breast cancer: profilometric analysis.

BACKGROUND/AIM: Treatment of breast cancer involves an association of conservative surgery and radiotherapy. This implies various cutaneous complications, well known for their clinical and histological aspects. Little data are available concerning modifications of the cutaneous microrelief after radiotherapy. We have done a profilometric analysis of the skin of breast cancer patients treated with surgery and radiotherapy. The results obtained on the irradiated breast have been compared with the ones of the controlateral normal breast. METHODS: Twenty women, 43-55 year old were enrolled in the study 6-16 months after the end of a treatment associating conservative surgery and radiotherapy for breast cancer. Imprints using a silicone rubber material were performed over symmetrical areas of the treated breast and the controlateral one. All measures were performed over the upper-medial quadrant of each breast. The imprints are then blindly analysed using an image analyser. The following parameters were measured: RA (average roughness of the skin), RZ (average of the furrows depth), RS (residual length), Rn (number of furrows) and AR (space between the furrows). RESULTS: The comparison of the imprints shows important modifications of the microrelief after irradiation. We observe a slight increase of the skin roughness (RA: 26, 39 +/- 2, 58 versus 21, 84 +/- 1, 59), a significantly increase of the furrows depth (RZ: 121, 66 +/- 10, 46 versus 101, 26 +/- 6, 99) along with an increase of the residual length (RS: 580, 60 +/- 60, 60 versus 450, 46 +/- 48, 43). The number of furrows has not significantly decreased but the space between the furrows has increased on the irradiated breast. CONCLUSION: This study shows a breakdown effect of irradiation on the skin in correlation with the fibrosis inducing by ionising radiation. The imprints modifications are clearly different from those usually observed in the ageing process. Our results can be a basis for studying the effects of treatments on cutaneous complications linked to the radiation-induced fibrosis.

Adult↗
PubMed2001

Skin topography measurement by interference fringe projection: a technical validation.

BACKGROUND/AIMS: The quantitative analysis of skin topography is frequently used in cosmetology to evaluate the efficacy of hydrating or anti-wrinkle creams (micro-topography studies) or creams for slimming or to alleviate stretch marks (macro-topography studies). Numerous methods involving the three-dimensional (3-D) reconstruction of the topography from silicone replicas have been developed. Some of the main techniques applied include optical profilometry based on the reflection of oblique lighting or on transparency, and profilometry by laser focusing or triangulation. METHODS: We chose to test the Dermatop system developed by Eotech Co., which is based on interference fringe projection profilometry associated with the Toposurf surface processing software. Owing to the system's principle of operation, we first ran three experiments to evaluate the influence of ambient lighting on the 3-D reconstruction and the surface roughness parameters, the influence of the calibration device built into the acquisition system and the influence of calibration in terms of ambient lighting correction. We then evaluated the accuracy, the repeatability and the reproducibility of the measurements provided by the system from known metal topographic standards and skin replicas. RESULTS: It was seen that external lighting can cause variations in the calculation of parameters SPa, SPt and SPtm which can reach error levels of about 5% if the operator does not almost systematically calibrate the apparatus between each measurement. These three experiments enabled us to standardise the protocol for the acquisition of 3-D information, in order to minimise the lighting problems and yet respect the requirements for routine studies. The correlation coefficient between the theoretical values and the mean of experimental values was 0.9955 for parameter SPa and 0.9983 for parameter SPtm. Repeatability presented variations of under 4%, irrespective of the parameters, and reproducibility of under 6%. CONCLUSIONS: The technique provides very satisfactory results from the point of view of accuracy, repeatability and reproducibility. It is an excellent compromise between cost, accuracy and the time required.

Dermatology↗
PubMed2001

Nonablative remodeling: clinical, histologic, ultrasound imaging, and profilometric evaluation of a 1540 nm Er:glass laser.

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.

Adult↗
PubMed2001

Treatment of wrinkles with the nonablative 1,320-nm Nd:YAG laser.

Ablative laser resurfacing with the CO2 and Er:YAG lasers has become a well-accepted and well-reported modality for skin rejuvenation of photoaged and photodamaged skin. However, the side effects associated with these lasers, such as exudation and crusting followed by prolonged erythema, are often socially disturbing for the patient. A nonablative 1,320-nm pulsed Nd:YAG system has been developed that controls dermal collagen damage while preserving the epidermis. Thirteen patients are presented on whom periocular wrinkle treatment was carried out during two sessions 1 month apart. Side effects were minimal. Histology showed improvement in the previously typical sun-damaged dermis. However, although physician assessment noted a trend toward macroscopic improvement, almost all patients failed to see any improvement. The authors conclude that further studies of the ideal parameters are required before the 1,320-nm Nd:YAG laser can be indicated successfully in stand-alone, nonablative wrinkle removal. In addition, patients should be selected carefully, and a complementary minimally aggressive technique should be used to restore a youthful appearance to the epidermis.

Adult↗
PubMed2000

Microrelief of the skin using a light transmission method.

The recently developed Skin Visiometer, based on light transmission through blue-coloured silicone replicas, was used to study skin microrelief. Calibrated metal plates displaying lines with depths between 6 and 361 microns, were used to determine the accuracy, sensitivity and reproducibility of the technique as well as the parameters of importance during measurement. The precision of the measurements was particularly good between 10 microns and 361 microns. The sensitivity of the method was between 10 and 20 microns. Replicas of volar forearm skin were taken from four groups (n = 15) of male and female volunteers in the age ranges 20 to 30 years and 55 to 65 years. In addition to the instrumental roughness parameters (Rz, Rt, Rm and Ra), the surface of the furrows, the number of primary and secondary lines and the number of intersections were determined. For both sexes, significantly lower values were observed for Rz, Rm and Rt in the younger age group than in the older age group. In addition, the numbers of primary and secondary lines and the number of intersections were higher, pointing to a more structured microrelief in younger forearm skin. Diurnal rhythm, the relative humidity of the measuring room and the position of the forearm were found to be significant factors, while room temperature and precleansing of the skin with mild products were not. Following the application of a hydrating cream (twice daily for 14 days) to the forearm skin of the older female age group, the Rz, Rt, Rm and Ra decreased, while the other parameters measured, except for the surface taken in by the lines, increased, indicating that the microrelief was modified towards the typical pattern observed in young skin.

Adult↗
PubMed2000

Characterisation of gravity-induced facial skin oedema using biophysical measurement techniques.

BACKGROUND/AIMS: In humans, the microgravity environment can be expected to induce swelling of facial tissues and shrinking of the tissues in the lower limbs, together with a loss in body weight. To evaluate fluid shifts in skin, the head-down bed-rest model was used. The aim of the present study was to evaluate the appearance of facial oedema in subjects undergoing anti-orthostatic bed-rest at an angle of -10 degrees. METHODS: The forehead of each of four subjects was measured before and after 1, 10 and 24 h in this head-down tilt position. At these time points, interstitial fluid migration and facial oedema were assessed using a high resolution B-scan ultrasound and a device for measuring the skin's mechanical properties. RESULTS: The results obtained showed a progressive increase in dermal thickness and initial stress, and a reduction in stiffness and elasticity of the skin during the study period. CONCLUSIONS: This preliminary study has demonstrated the feasibility of the method in measuring fluid displacement and retention in the skin. Furthermore, it highlights the influence of fluids on the mechanical behaviour of the skin. These techniques could be used for studying the redistribution of liquid masses during periods spent in space.

Aerospace Medicine↗
PubMed1998

Profilometric evaluation of photodamage after topical retinaldehyde and retinoic acid treatment.

OBJECTIVE: We compared the activity and tolerance profile of a 0.05% retinaldehyde cream with a 0.05% retinoic acid cream and the retinaldehyde vehicle in patients with photodamaged skin of the face. METHODS: A silicone replica of the left crow's feet area was taken at baseline and at weeks 18 and 44. Skin replicas were then analyzed by means of an optical profilometry technique. Standard wrinkle and roughness features were then calculated and statistically analyzed. The tolerance profile of the test products was also clinically evaluated during the entire study. RESULTS: A total of 125 patients (40 in the retinoic acid group, 40 in the retinaldehyde group, and 45 in the vehicle group) were studied. At week 18, a significant reduction of the wrinkle and roughness features was observed with both retinaldehyde and retinoic acid. At week 44, a less pronounced reduction was demonstrated in both active groups. No statistically significant changes were observed with the retinaldehyde vehicle at any assessment point. A total of 135 patients constituted the safety population. Retinaldehyde was well tolerated during the entire study. In contrast, retinoic acid caused more local irritation, and affected compliance of the patients. CONCLUSION: Retinaldehyde was efficacious and well tolerated in patients with photodamage.

Adult↗
PubMed1994

Confocal microscopy of hair.

Confocal microscopy is an excellent method for studying the localization of fluorescent stains. Used in this way, superior 3D images can be obtained from multiple optical sections with very shallow depth of field. The main advantage of this technique is that the sample is not damaged. We have taken serial confocal sections of hair and via specific image enhancement routines have obtained high-quality 3D images enabling the visualization of cuticle scale and its pattern of distribution. This has been done on various types of hair: bleached, permed and in certain pathological conditions. This first step will allow us to characterize the hair surface in terms of its roughness, and the distribution and form of cuticular scale, parameters that have potential in the assessment of dermocosmetic efficacy.

Hair↗
PubMed1981

Long-term effects of a tryptophan-free diet on serotonin metabolism and sleep-waking balance in rats.

1. A long-term (up to 16 weeks) tryptophan (TRP)-free diet was administered to chronically implanted adult rats in order to study the effects of a sustained reduction of endogenous brain serotonin (5-HT) levels on the sleep-waking cycle. Twenty-four hours polygraphic recordings were made either periodically on an EEG apparatus, or uninterruptedly over 50 days by a frequency analyser. Quantitative changes in wakefulness (W), slow wave sleep (SWS) and paradoxical sleep (PS), as well as the number and duration of these episodes, were studied over 24 h, with a dark period (DP) and a light period (LP). Biochemical changes in 5-HT metabolism were measured in both plasma and brain. 2. Under control conditions, the percentage of W was twice as great in DP as in LP, while the quantities of SWS and PS were twice as high in LP as in DP. Surprisingly, in spite of a decrease of about 50% in brain 5-HT under TRP-deprived conditions, no dramatic changes were observed in the qualitative or quantitative aspects of W, SWS or PS. The only electrocorticographic (ECoG) change was a disappearance of sleep spindles, which became total after 14 weeks. During the first month, there was a 7% increase in W accompanied by a 6% decrease in SWS and a 5-9% reduction in PS. Later, W and SWS returned to their control values, while the PS deficit persisted throughout the TRP-deprivation period. Despite the absence of severe quantitative disturbances over 24 h, an internal reorganization of the sleep cycle took place. This new balance, established after 2 months, was characterized by a tendency toward an equal distribution of the stages in DP and LP, resulting in the disappearance of the sleep circadian rhythm. 3. Our results are compared with those of other authors who lowered the endogenous 5-HT levels by various means, including 'acute' or partial TRP-deprivation. The present findings suggest that adaptive cerebral mechanisms are able to compensate for the disturbances in 5-HT metabolism, in structures responsible for W and SWS. They indicate that the neurohumoral processes underlying sleep circadian rhythm in the rat are serotoninergic and/or noradrenergic.

Animals↗