Characterization of port wine stain skin erythema and melanin content using cross-polarized diffuse reflectance imaging

BACKGROUND AND OBJECTIVES: Objective methods to assess quantitatively port wine stain (PWS) blanching in response to laser therapy are needed to improve laser therapeutic outcome. Previous studies have attempted to assess objectively PWS color based on point measurement devices. To date, these approaches have typically been limited by a number of factors such as small test area and need for contact. To address these issues, a cross-polarized diffuse reflectance imaging system and color image analysis method has been developed to evaluate quantitatively erythema and melanin content in PWS skin. STUDY DESIGN/MATERIALS AND METHODS: A cross-polarized diffuse reflectance system has been constructed to acquire high resolution digital images while minimizing artifacts such as glare, shadowing, and nonuniform illumination effects that can compromise image fidelity. Furthermore, an image analysis algorithm has also been developed to analyze normal and PWS skin in terms of CIEL*a*b* color space parameters. Using the algorithm, images of color space intensity, L*, and saturation, a*, indices have been calculated to extract quantitative metrics of melanin and erythema, respectively. RESULTS: Compared to the cross-polarized diffuse reflectance image, the a* index image enhanced the contrast in regions of high and low erythema and seems to have quasi correlation with the L* index image. In the presented PWS patient example, the relative a* index difference (Deltaa*) image showed less erythema in PWS skin after laser treatment when compared to pre-treatment values. CONCLUSIONS: Our cross-polarized imaging system and color image analysis method is a simple, noncontact technique that can indirectly provide quantitative measurement of erythema and melanin content in PWS skin.     

A new method of skin erythrosis evaluation in digital images

In the clinical field, reproducible and comparable assessments of skin color are needed for objective evaluation of lesions and efficacy of treatments. In order to provide objective, quantitative color information in skin lesions, devices such as reflectance spectrophotometer and reflectance colorimeter have been successfully used during the past decade, though they are too expensive and technically complex to be handled in routine clinical situations. Reflectance skin color measurements require direct contact of the probe with the skin, and the compression significantly influences readings. Color measurements obtained from digitized images have been proposed as a simple and cost-effective way to evaluate skin color and promote efficacy of treatments. The disadvantage is its direct and close relation to the ambient light: even if an accurate control of subject illumination is provided, readings vary between different laboratories. We propose a standard system for computerized color image analysis of skin erythrosis modification after Intense Pulsed Light (IPL) treatments, making it possible to compare readings taken by different observers in different environmental light conditions. The goal of our study is the introduction of fixed color internal controls in digital imaging in order to calculate a normalization factor of measurements, resulting not in a method of absolute quantification of erythema or erythrosis but in a method that provides the possibility of translation and comparison of the red values between systems in different environmental conditions. Between December 2004 and May 2005 we evaluated 30 patients at the Department of Plastic and Reconstructive Surgery at the University "La Sapienza" of Rome. Three points of standard colored paper (Red Green Blue) were applied with a plastic pattern (standard intersection lines) and white point in non involved area for skin control. For every patient we took a series of pictures pre-treatment and after a standard cycle of 5/6 IPL. We evaluate the grade of reproducibility of our procedure with a careful analysis of pre-treatment digital images obtained in different environmental conditions. The statistic analysis of the standard deviation between the values of R obtained (using different light conditions), and the respective normalized valor (normalized to the referent image), did not show any significant statistical difference and allows us to achieve our goal: the reproducibility of the results.     

Use of erythema index imaging for systematic analysis of port wine stain skin response to laser therapy

BACKGROUND AND OBJECTIVES: Quantitative methods to assess port wine stain (PWS) skin response to laser therapy are needed to improve therapeutic outcome. In this study, PWS skin erythema was analyzed using erythema index difference (DeltaEI: erythema index difference between PWS and normal skin) images before and after treatment to investigate systematically subject-dependent response to laser therapy. STUDY DESIGN/MATERIALS AND METHODS: Cross-polarized digital skin color images were acquired from 17 subjects with facial PWS and the associated DeltaEI images were computed. Qualitative and quantitative analyses of PWS skin erythema were performed with DeltaEI images, in which ranges of 40-6 and 5-0 represented PWS and normal skin, respectively. RESULTS: After laser therapy, we qualitatively observed a reduction in the DeltaEI values for all subjects. Regression fitting of DeltaEI values before and after PWS laser therapy was associated with strong positive linear correlation. CONCLUSIONS: The imaging modality and analysis method allowed systematic analysis of PWS skin erythema in response to laser therapy. PWS skin response was dependent on pretreatment DeltaEI values, suggesting that erythema can be utilized as an effective parameter to monitor PWS response to laser therapy.     

Non-invasive quantification of skin injury resulting from exposure to sulphur mustard and Lewisite vapours

The severity and progression of skin lesions resulting from exposure to the chemical warfare agents Lewisite (L) and sulphur mustard (SM) have been investigated using the non-invasive biophysical methods of evaporimetry and reflectance spectroscopy in large white pigs in vivo. Erythema (redness) expressed immediately after exposure to L or SM vapours appeared to be related to the lesion severity as demonstrated by histopathological analysis. Skin brightness correlated well with scab formation whereas blueness (cyanosis) did not appreciably alter throughout the study. Rates of transepidermal water loss (TEWL) changed both with occlusion (during vapour exposure) and also mirrored the progression of macroscopic skin injury after 12 h. Whilst no single parameter could be used in isolation to ascertain the severity and subsequent progression of the skin lesions, measurement of erythema, skin brightness and TEWL could provide quantitative, non-invasive methods for determining the efficacy of antidotes or therapies to prevent the toxic effects of chemical warfare agents. However, neither colourimetry or TEWL provided a clinical evaluation of such lesions that were comparable with the prognostic capabilities of laser Doppler imaging.     

In vivo monitoring of microvessels in skin flaps: introduction of a novel technique.

Orthogonal polarization spectral (OPS) imaging was validated against intravital fluorescence microscopy (IFM) for microvascular measurements in skin flaps of hairless mice. Examinations were performed 1, 6, and 24 hours after elevation (n = 8) with both OPS imaging and IFM. A fluorescent dye was a prerequisite for IFM measurements but not for OPS imaging. Our findings show that OPS imaging can visualize the skin flap microcirculation independent from the application of fluorescent tracers. From these images, quantitative analysis of functional capillary density (FCD) was feasible. As expected, FCD was significantly lower in the distal part of the flap compared with its base (171.8 +/- 34.7 versus 62.0 +/- 25.6, mean +/- SD; 1 hour data). Comparison of OPS imaging and IFM revealed a significant correlation of FCD values (P < 0.001) at all time points. Given the success of this validation study on mouse skin flaps, clinical investigations will have to prove that OPS imaging can also successfully be used to monitor flaps in humans.     

The hemodynamic effects of cell-free hemoglobin during general and epidural anesthesia

Local anesthetics inhibit edema and improve circulation in experimental burns. We evaluated the effect of topical local anesthetics on human skin burns in volunteers using computerized color analysis that allowed repeated noninvasive quantitative measurements. A standardized partial-thickness burn (1 cm2) was induced in one forearm of 10 healthy volunteers and in the opposite forearm a week later. The burned areas were treated with lidocaine/prilocaine cream (EMLA; Astra, Sweden) or a placebo cream for 1 h. The experimental skin area was photographed before and 1, 2, 4, and 12 h postburn. Digitized images were evaluated using normalized red-green-blue and Hue-Saturation-Intensity. Differences in erythema between skin treated with EMLA and placebo were not significant during the first 4 h postburn. However, 12 h postburn, a pronounced decrease in the degree of erythema was observed in EMLA-treated skin compared with placebo-treated skin. We conclude that topical local anesthetics administered for 1 h postburn significantly reduces the duration of erythema after a mild thermal injury, which suggests a potential use in clinical practice in the treatment of minor skin burns. IMPLICATIONS: Burn injury constitutes a serious type of tissue damage that activates inflammatory mechanisms, often causing pain, disfiguration, or malfunction. We treated burns using an anesthetic cream and demonstrated a reduction in burn-induced inflammation by using computer-based color image analysis.     

Real-Time Compound Imaging Ultrasound of Hidradenitis Suppurativa

BACKGROUND Hidradenitis suppurativa (HS) is a difficult disease to treat. Surgery may be curative, but just like cancer surgery, it must be complete to effect a cure. Preoperative imaging of hidradenitis lesions is therefore of interest.
OBJECTIVE The objective was to study the ultrasound characteristics of hidradenitis and compare these to the clinical findings.
MATERIALS AND METHODS Real-time compound imaging ultrasound systems were used (Philips HDI 5000 and iU22) to visualize HS lesions in seven patients and regional controls images from eight healthy volunteers.
RESULTS Hidradenitis-related features were identified: various fluid collections, increased dermal thickness (mean±SD, 3.3±1.0 mm vs. 1.4±0.3 mm for controls) and lower echogenicity of the skin. In comparison with clinical examination, we were able to identify both subclinical lesions and subclinical extension of lesions into clinically normal looking paralesional skin. Hair follicles appeared distended.
CONCLUSION A number of HS features can be identified by ultrasound. These features include both actual lesions and possible predisposing factors such as skin thickness and hair follicle morphology. Ultrasonography can identify the true extent of lesions in HS, which may be of use in the preoperative planning.     

Determination of an optimized conversion matrix for device independent skin color image analysis

BACKGROUND AND OBJECTIVE: A cross-polarized diffuse reflectance (CDR) color imaging system was developed for quantitative evaluation of port wine stain (PWS) response to laser therapy. To obtain calibrated Commission International de l'Eclairage (CIE) color space images from RGB (red, green, and blue) images, it was necessary to derive an optimized conversion matrix specific to our imaging system. STUDY DESIGN/MATERIALS AND METHODS: A chromameter (CR-200, Minolta) and CDR imaging system were used to acquire CIELAB (CIE L*, a*, and b*) tristimulus values and RGB image values, respectively. A cost function was defined using these sample data sets and then a minimization algorithm was applied to obtain an optimized conversion matrix for our imaging system and illumination conditions. CIELAB color space values (L*, a*, and b*) obtained with the chromameter and CDR color images were compared to assess the accuracy of the derived matrix. RESULTS: In measurements using in vitro standard color patch or in vivo human skin samples, use of the optimized conversion matrix resulted in a good correlation with standard chromameter values for PWS human skin sites. CONCLUSIONS: The cost function minimization algorithm resulted in an optimized conversion matrix for our CDR imaging system. Use of the optimized matrix improved the utility of CDR color image analysis as a simple non-contact measurement technique to monitor quantitatively PWS response to laser therapy.     

Advances in imaging of rheumatoid arthritis

Several new imaging modalities have been found useful in clinical evaluation of patients with rheumatoid arthritis (RA). Magnetic resonance (MR) imaging has proven to be an excellent noninvasive method to evaluate the spine, shoulder, hip, and knees; its use for the evaluation of smaller joints is still being investigated. In patients with RA, MR imaging has been used to evaluate cervical spine instability, rotator cuff tear, osteonecrosis, and osteomyelitis. Patients with RA may have advanced osteoporosis, predisposing to insufficiency fractures. This includes fractures associated with increased activity after hip or knee arthroplasty. Newer methods for measuring the degree of osteoporosis include single photon absorptiometry, dual photon absorptiometry, quantitative computed tomography (CT), and dual-energy projection radiography. It has not yet been determined which of these methods will be most widely used in the future, but quantitative CT and dual-energy projection radiography currently show the most promise. Ultrasonography provides an excellent noninvasive method for the diagnosis of popliteal cysts, and color Doppler sonography can differentiate cyst and popliteal aneurysm. As compared to radiography or conventional CT, high-resolution CT provides an improved method to detect the early changes of RA in the lung parenchyma.     

P53 Immunohistochemical Expression in Early Posttransplant-Associated Malignant and Premalignant Cutaneous Lesions

Background.  Current evidence suggests that p53 accumulation is critical to the development of skin cancer in the general population. It is possible, however, that the molecular steps involved in transplant-associated and non-transplant-associated skin carcinogenesis may differ.
Objective.  Our purpose was to examine p53 expression in premalignant and malignant skin lesions from renal transplant recipients (RTRs) in their first 3 years of immunosuppression, as well as in equivalent lesions from immunocompetent normal individuals.
Methods.  p53 expression was examined by routine immunohistochemical methods using the anti-p53 monoclonal antibody DO7.
Results.  p53 immunoreactivity was more prevalent in dysplastic epidermal keratoses and cutaneous carcinomas from RTRs than in equivalent lesions from nontransplant controls. Statistical analysis revealed significant differences, however, only in premalignant skin lesions ( p = 0.03).
Conclusion.  This study demonstrates that accumulation of p53 protein is frequently encountered in both premalignant and malignant skin lesions of RTRs, and that this may occur as an early step in transplant-associated skin carcinogenesis.     

胃造影动态容积CT三维重建技术的建立及应用

目的 探讨胃造影动态容积CT三维重建技术在胃部疾病诊断和病情评估的临床应用价值.方法 结合320排容积CT具有“薄”（层厚0.5 mm）、“大”（人体纵轴16 cm）、“快”（单圈扫描0.35s）等特点,胃造影动态容积CT扫描后应用三维重建技术,具体分析胃及十二指肠球部的大小、形态、位置、壁厚薄、蠕动性、黏膜病变、动态增强表现及上腹部（包括肝、胆、胰、脾等脏器与周围血管等）的影像信息,并与纤维胃镜进行对比分析.共收集62例胃部疾病患者,包括胃肿瘤性病变29例、溃疡性病变6例、胃炎20例、胃憩室2例（均由手术病理或胃镜组织活检证实）,胃周血管病变5例（由血管造影证实）.结果 溃疡性病变及肿瘤性病变的诊断结果接近纤维胃镜的诊断结果,胃炎的诊断结果略差;肿瘤性病变能准确定位、定性、明确病灶转移及血供情况.结论 胃造影动态容积CT三维重建技术对胃及十二指肠疾病的准确定位及定性均有重要价值,尤其对肿瘤性病变术前的具体病情评估及手术方案拟定具有明显优势,为胃及十二指肠疾病的诊断提供了一个崭新的研究方法,值得临床推广应用.     

Optical biopsy of epithelial cancers by optical coherence tomography (OCT)

Optical coherence tomography (OCT) is an optical technique that measures the backscattering of near-infrared light by tissue. OCT yields in 2D and 3D images at micrometer-scale resolution, thus providing optical biopsies, approaching the resolution of histopathological imaging. The technique has shown to allow in vivo differentiation between benign and malignant epithelial tissue, through qualitative assessment of OCT images, as well as by quantitative evaluation, e.g., functional OCT. This study aims to summarize the principles of OCT and to discuss the current literature on the diagnostic value of OCT in the diagnosis of epithelial (pre)malignant lesions. The authors did a systematic search of the electronic databases PubMed and Embase on OCT in the diagnostic process of (pre)malignant epithelial lesions. OCT is able to differentiate between benign and (pre)malignant lesions of epithelial origin in a wide variety of tissues. In this way, OCT can detect skin cancers, oral, laryngeal, and esophageal cancer as well as genital and bladder cancer. OCT is an innovative technique which enables an optical biopsy of epithelial lesions. The incorporation of OCT in specific tools, like handheld and catheter-based probes, will further improve the implementation of this technology in daily clinical practice.     

紫外线照射后无毛鼠皮肤纹理的变化及其定量分析

目的 通过用长波紫外线[ultraviolet A，UVA（320～400nm）]、中波紫外线[ultraviolet B，UVB（280～320nm）]及UVA＋UVB照射无毛鼠，观察不同种类紫外线对无毛鼠皮肤纹理的影响，为临床防治皮肤光老化寻找理论依据。方法 无毛鼠经紫外线照射20周、UVA总计量222J／cm^2，UVB总计量5．9J／cm^2。通过肉眼、皮纹放大及应用彩色皮肤病理图像定量分析系统，对接受紫外线（ultraviolet，UV）照射后的无毛鼠皮肤纹理进行对比观察。结果 对照组：皮纹细腻，皮沟、皮脊分布均匀，无明显角化。UVA组：皮肤略显粗糙，皮沟、皮脊分布尚均匀，无明显角化。定量分析结果与正常未照射组差异不明显。UVB组：皮纹粗乱，皮沟加深、加宽，皮脊增宽，分布不均匀，皮肤明显角化。定量分析结果与正常未照射组差异显著。UVA＋UVB组：皮纹更加粗乱，皮沟加深、加宽、皮脊增宽，分布不均匀，皮肤角化更加明显。定量分析结果与对照组差异显著。结论 通过对UV照射后无毛小鼠皮肤纹理的结构和定量分析表明，UVA对皮肤皱纹的产生作用不明显，UVB、uVA＋UVB对皮肤皱纹的产生明显，UVA、UVB有协同作用，UVB是紫外线造成皮肤皱纹产生的关键成分。     

Assessment of tissue perfusion changes in port wine stains after vascular targeted photodynamic therapy: a short-term follow-up study

The occlusion effect of vascular targeted photodynamic therapy (V-PDT) for malformed vessels in port wine stains (PWS) often last for some time after the treatment. A relatively longer period after V-PDT is needed to accurately assess the final response of PWS microcirculation to the treatment. In this study, we intended to use laser speckle imaging (LSI) to assess the tissue perfusion changes of PWS at follow-up after V-PDT and preliminarily analyze the relationship between perfusion change and color bleaching. Seventeen patients with 40 PWS lesions were scanned by LSI before and 3–6 months after they received V-PDT. The speckle flow indices of PWS lesions and normal skin before and at follow-up after V-PDT were recorded. We also performed analyses on the correlation between perfusion changes and color bleaching. Before V-PDT, the 40 PWS lesions showed higher perfusion than the normal skin (1,421?±?463 and 1,115?±?386 perfusion unit (PU), respectively, P?<?0.01). The PWS lesions scanned at follow-up showed decreased perfusion level compared to the preoperative values (1,282?±?460 and 1,421?±?463 PU, respectively, P?<?0.01). After V-PDT, the perfusion change rates coincide well with the color bleaching rates (correlation coefficient, 0.73). In conclusion, the LSI system is capable of imaging PWS perfusion precisely, and it has shown promising results in assessing the changes of tissue perfusion of V-PDT for PWS, with objective and quantitative data, real-time images, and a shorter detection time. It may also provide an effectiveness assessment method for the treatment of PWS.     

Efficacy of 1% 4-Ethoxybenzaldehyde in Reducing Facial Erythema

Background. Facial erythema is a common postsurgical and dermatologic problem. It is commonly the result of dermal inflammation arising from either a facial surgical procedure, such as laser resurfacing, dermabrasion, or a face peel, or from an underlying dermatologic condition, such as rosacea. Facial erythema is difficult for the dermatologist to treat in both settings because topical corticosteroids cannot be used long term on the thin facial skin and anti-inflammatory oral or topical antibiotics have associated side effects.
Objective. The goal of this pilot study was to evaluate the anti-inflammatory effect of 1% 4-ethoxybenzaldehyde in a rosacea model of facial erythema.
Methods. Thirty subjects with mild to moderate stable rosacea were enrolled in this 4-week, double-blind, vehicle-controlled study. Photographs, investigator assessment, and subject assessment were the efficacy criteria.
Results. There was a statistically significant reduction in facial erythema (p<.01) in those subjects who used the active for 4 weeks, as well as a statistically significant improvement in uneven skin tone (p<.01) and the overall severity of the disease (p<.01). There was no statistically significant difference in any of these three indices in the vehicle-treated group.
Conclusion. The results suggest that benzaldehyde-derived anti-inflammatory agents may be useful in reducing facial erythema in a rosacea model.
THIS STUDY WAS FUNDED BY AN EDUCATIONAL GRANT FROM CUTANIX CORPORATION. ZOE DRAELOS, MD, HAS INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS. BRYAN FULLER, PHD, IS THE INVENTOR OF THE ACTIVE, WHICH WAS LICENSED THROUGH THE OKLAHOMA HEALTH SCIENCES CENTER TO CUTANIX.     

Analysis of Erythema after Er:YAG Laser Skin Resurfacing

BACKGROUND Postoperative erythema can be expected to occur in every patient after laser resurfacing, and pigmentary disturbances may be related to the intensity and the duration of erythema.
OBJECTIVE This study was undertaken to assess the clinical features of erythema, the factors that influence its duration, and the relation between the duration of erythema and the incidence of hyperpigmentation and hypopigmentation in skin of Asian persons after Er:YAG laser resurfacing.
METHODS A total of 218 patients (skin phototypes III to V) were recruited and treated with a short-pulsed Er:YAG laser, a variable-pulsed Er:YAG laser, or a dual-mode Er:YAG laser for skin resurfacing. Clinical assessments were performed retrospectively using medical charts and serial photographs.
RESULTS Postoperative erythema was observed in all patients after Er:YAG laser resurfacing with a mean duration of 4.72 months. In 98.2% of patients, erythema faded completely within 12 months. Postinflammatory hyperpigmentation was observed in 38.1% of patients after Er:YAG laser resurfacing.
CONCLUSIONS Skin phototype, level of ablation, and depth of thermal damage caused by a long-pulsed laser appear to be important factors that affect the duration of erythema. Moreover, prolonged erythema was related to the risk of postinflammatory hyperpigmentation.     

Pathology, diagnosis, and classification of pressure ulcers: comparing clinical and imaging techniques

Pressure ulcer classification systems are based on the clinical manifestations of the skin and tissue layer affected rather than underlying pathology. The objective of this study was to compare the validity of the clinical grading of erythema (blanching and nonblanching) with a measurement of skin perfusion. Therefore, an exploratory study comparing erythema with laser Doppler imaging of the sacrum and buttock skin areas was undertaken. Acute and major elective general, vascular, and orthopedic surgical in-patients, aged 55 years or over with an expected length of hospital stay of 5 or more days were recruited. Fifty laser Doppler images from 37 patients were obtained and included in a discriminant analysis. Discriminant analysis suggested that blanching and nonblanching erythema were physiologically distinct from "normal" skin; clinically, these could be assessed with reasonable accuracy. Imaging also determined that high blood flow of differing intensity characterized blanching and nonblanching erythema. There was no evidence of the "no flow" phenomenon.     

Diagnostic study of vascular lesions

Detailed diagnostic evaluation of upper extremity vascular lesions is not possible with any single existing test or study. Arteriography and improved arteriographic techniques, including digital subtraction imaging, have increased dramatically the resolution of this procedure. Unfortunately, reactive vasospasm and limited run-off still preclude the provision of complete information about vascular anatomy. Surgical exploration, of course, provides direct access to arterial and venous structures in a limited area, but it has obvious limitations. Indirect information about the structural anatomy can be obtained by Doppler techniques, ultrasound scans, and radionuclide imaging. These techniques also provide limited information about changes in perfusion during stress. Plethysmography, thermography, thermometry, and measurements of segmental arterial pressure, when combined with stress testing, provide excellent indirect evidence of both static and dynamic states. A combination of pressure measurements and intraoperative ultrasound associated with direct surgical measurement will provide quantitative and qualitative analysis of antegrade and retrograde flow and allow the surgeon to look at the intima of vessels without surgically traumatizing the vessel wall. Within the next decade, real-time information with three-dimensional reconstruction of arterial and venous structures as well as quantitative analysis of segmental areas of blood flow will be provided by the use of combinations of these techniques or techniques that have not yet been reported.     

VISIA 皮肤检测仪检测数值在皮肤美容中的临床应用

VISIA皮肤检测仪是认可度及实用度最高的非侵袭性皮肤检测仪器，通过百分位数、分值、特 征计数三种数值指标定量分析面部斑点、皱纹、深层色素和皮肤红斑区等美容主治项目的治疗效果，全面 客观地评估和记录皮肤状态，指导治疗决策，跟踪治疗效果，对医疗美容行业皮肤诊断及市场发展有重要 意义。但在其使用过程中，医生只专注VISIA成像的视觉效果对比，忽略了数据评估，缺乏对皮肤状态客 观评估的证据，存在一定局限性，因此本文就VISIA数值在医疗美容行业的应用进行综述，旨在为临床医 生应用皮肤检测仪提供参考。     

Perfusion and vascular permeability: Basic concepts and measurement in DCE-CT and DCE-MRI

The microvascular network formed by the capillaries supplies the tissues and permits their function. It provides a considerable surface area for exchanges between blood and tissues. All pathological conditions cause changes in the microcirculation. These changes can be used as imaging biomarkers for the diagnosis of lesions and optimisation of treatment. Among the many imaging techniques developed to study the microcirculation, the analysis of the tissue kinetics of intravenously injected contrast agents is the most widely used, either as positive enhancement for CT, T1-weighted MRI and ultrasound – dynamic contrast-enhanced-imaging (DCE-imaging) – or negative enhancement in T2*-weighted brain MRI – dynamic susceptibility contrast-MRI (DSC-MRI) –. Acquisition involves an injection of contrast agent during the acquisition of a dynamic series of images on a zone of interest. These kinetics may be analyzed visually, to define qualitative criteria, or with software using mathematical modelling, to extract quantitative physiological parameters. The results depend on the acquisition conditions (type of imaging device, imaging mode, frequency and total duration of acquisition), the type of contrast agent, the data pre-processing (motion correction, conversion of the signal into concentration) and the data analysis method. Because of these multiple choices it is necessary to understand the physiological processes involved and understand the advantages and limits of each strategy.