A new method for the visualization and quantification of internal skin elasticity by ultrasound imaging

The Intra-rater reliability and validity of ultrasonography in the evaluation of hypertrophic scars caused by burns

PURPOSE

Hypertrophic scars that occur after burns are less flexible and less elastic than normal skin. Objective measurement tools are required to assess hypertrophic scars after thermal injury. Cutometer® MPA 580 has been widely used for evaluating the properties of hypertrophic scars. Ultrasonography can evaluate elasticity, stiffness, and structure of tissues simultaneously using elastography and B-mode. This study aimed to investigate the intra-rater reliability and validity of elastography to visualize hypertrophic scars.

METHODS

Sixteen participants with a total of 96 scars were evaluated. The measurement sequence was elastography, Cutometer®, and elastography every 10 min. We then analyzed the intra-rater reliability using intraclass correlation coefficients (ICC). The results measured using elastography on the hypertrophic scars and surrounding normal skin were compared. The relationships between the elastographic and Cutometer® measurements using the 2-and 8-mm probes were compared.

RESULTS

The intra-rater reliability of elastographic measurements was acceptable for clinical use in terms of strain ratio (SR), shear-wave elastography (SWE), shear-wave speed (SWS), and SWE ratio ( ICC = 0.913, ICC=0.933, ICC = 0.842, and ICC = 0.921). The average SWS and SWE in hypertrophic scars were significantly greater than that for normal skin ( p < 0.001 and p < 0.001). SWE showed correlations with the R0 (r = -0.32, p = 0.002) and R8 (r = -0.30, p = 0.003) measured with the 8-mm probe. The SWE ratio was correlated with the R7 (r = -0.34, p = 0.001) measured with the 2-mm probe. The thickness of hypertrophic scars showed correlations with the R5 (r = 0.33, p < 0.001), R6 (r = 0.44, p < 0.001) and R8 (r = -0.35, p < 0.001) measured with the 8-mm probe. R0-R9 measured with 2-mm Cutometer® probes were not correlated with scar thickness ( r < 0.30, P > 0.05). The total scores of mVSS showed correlations with the R0 (r = 0.35, p < 0.001), R1(r = 0.32., p = 0.001), R3 (r = 0.38, p < 0.001), R4 (r = 0.38, p < 0.001), R8 (r = 0.34, p = 0.001), and R9 (r = 0.34, p = 0.001) measured with the 2-mm probe. R0-R9 measured with 8-mm Cutometer® probes were not correlated with mVSS ( r < 0.30, P > 0.05). The thickness of hypertrophic scars showed correlations with the SWE (r = 0.38, p < 0.001) and SWE ratio (r = 0.35, p < 0.001). Elastographic findings were not correlated with mVSS ( r < 0.30, P > 0.05).

CONCLUSION

In this study, together with the Cutometer®, ultrasound was confirmed as an evaluation tool that can objectively compare and analyze the difference between normal skin and hypertrophic scars.

Examination of age-related changes of viscoelasticity in the dermis and subcutaneous fat layer using ultrasound elastography

BACKGROUND

Using ultrasound elastography, the present study aimed to measure the viscoelasticity in each skin layer and to determine the relationship between the measured value, age, and body mass index (BMI).

MATERIALS AND METHODS

The present study included 77 Japanese women. We calculated the BMI and measured the facial cheek via elastography. With the use of the elastographic image, the dermis was divided into two layers, and the subcutaneous fat layer was divided into five equal sections according to the depth, ultimately obtaining seven layers. Furthermore, the thickness and viscoelasticity of each divided layer were measured.

RESULTS

The analysis of echo images revealed that the thickness of the upper dermis layer decreased with age, whereas that of the subcutaneous fat layer tended to increase with age and BMI. As measured by elastography, the viscoelasticity of both the lower dermis and the upper subcutaneous fat layer decreased with age. As the BMI increased, the viscoelasticity of the lower subcutaneous layer also increased, but that of the upper subcutaneous layer decreased.

CONCLUSIONS

The present study revealed the relationship between aging and viscoelasticity in the lower dermis and the relationship between aging, BMI, and viscoelasticity in the upper subcutaneous fat layer.

Elastography reference values of facial skin elasticity

Introduction

With an introduction of new ultrasonographic transducers, skin elastography may find an application in dermatology and aesthetic medicine enabling direct evaluation of various pathological or natural processes.

Aim

To verify which elastographic technique, strain elastography (SE) or shear wave elastography (SWE), is a better candidate for the reference method of facial skin elasticity examination and to determine normal ranges for elastographic parameters in various facial regions.

Material and methods

The study included 71 female volunteers (age: 40–67 years, mean: 52 ±7.5 years). All participants were subjected to SE and SWE of the skin in five anatomical regions: the forehead, suborbital regions, cheeks, nasolabial folds and chin. Reference ranges for elastographic parameters were defined as 95% confidence intervals and ±2 standard deviations and estimated by means of ROC analysis.

Results

Shear wave elastography parameters, but not SE indices, showed strong inverse correlations with the patient age. No significant correlations were found between SE and SWE parameters of the facial skin. In contrast to SWE, no significant correlations were observed between bilateral SE parameters. Based on these findings, SWE was chosen as the reference method to determine age-specific normative values for the elasticity of the facial skin. Reference and cut-off values of SWE parameters were defined for three age groups.

Conclusions

Shear wave elastography is suitable for the determination of elastographic parameters of normal facial skin, and can be used to determine reference ranges thereof. Elasticity of the facial skin decreases considerably with age, and this factor should be considered during determination of reference values for the elastographic parameters.

Ultrasonographic elastography in the evaluation of normal and pathological skin - a review

The aim of this review article is to discuss the role of ultrasonographic elastography, a technique used to quantify tissue stiffness, in the evaluation of normal and pathological skin. A growing body of evidence suggests that elastography may be used for the diagnosis and monitoring of skin pathologies, in particular tumors, and fibrotic and sclerotic processes. Our knowledge about the elastographic parameters of normal skin is sparse, which together with the lack of reference values for cutaneous stiffness constitutes a serious limitation to the use of elastography in some medical disciplines, including aesthetic medicine.

Visualization of viscoelastic behavior in skin equivalent using optical coherence tomography-based straingraphy

BACKGROUND/PURPOSE

The relationships between the skin components and these mechanical roles are still unclear. To clarify these relationships, we investigated spatial mapping of the mechanical behavior of cultured skin equivalents (SEs) using optical coherence tomography (OCT)-based straingraphy.

METHODS

We built a strain relaxation test system combined with OCT and developed an algorithm that could visualize a time-dependent strain distribution, named dynamic-optical coherence straingraphy (D-OCSA). Using this system, we analyzed how the spatial mechanical changes in the SEs depended on the culture duration. For quantitative analysis of viscoelastic behavior, we defined a relaxation attenuation coefficient of strain rate, which indicates the ratio of viscosity and elasticity in the Klevin-Voight model.

RESULTS

By culturing for 4 days in comparison to culturing for 1 day, the strain relaxation attenuation coefficient of the whole skin, especially at the region of the dermal-epidermal junction (DEJ), significantly increased in the negative direction. In tissue slices taken for microscopy, several cracks were observed in the SEs cultured for 4 days.

CONCLUSION

This study is the first to provide quantified evidence that the DEJ is a dynamically specialized region. An OCT-based straingraphy system (D-OCSA) would be beneficial for evaluating the quality of SEs, as well as functional analysis of their mechanics.

Immediate Changes to Skin and Subcutaneous Tissue Strains Following Manual Lymph Drainage in Legs with Lymphedema

OBJECTIVES

To study the immediate impact of manual lymph drainage (MLD) on skin and subcutaneous tissue strains in legs with lymphedema using free-hand real-time tissue elastography (RTE).

METHODS

Skin and subcutaneous tissue strain measurements were taken at the middle of the inner thigh and calf by RTE in 20 legs with lymphedema of 18 patients (stage II: 11, late stage II: 7, stage III: 2) and in 70 legs of 35 normal subjects. In patients with lymphedema, the same measurements were repeated immediately following MLD.

RESULTS

Significant negative correlations were found between pre-MLD strains and the MLD-induced changes in thigh and calf skin strains (thigh skin: p <0.01, calf skin: p = 0.05), but not in subcutaneous tissue strains. Pre-MLD intercepts of these regression lines were closer to normal values as compared to mean pre-MLD values (normal thigh skin: 0.54% ± 0.30%, calf skin: 0.25% ± 0.18%, Pre-MLD thigh skin: 0.39% ± 0.20%, calf skin: 0.17% ± 0.12%, Pre-MLD intercept of thigh skin: 0.48%, Pre-MLD intercept of calf skin: 0.31%).

CONCLUSIONS

It appears that MLD did not simply soften the skin, but rather normalized it in terms of strain. However, this was not confirmed in the subcutaneous tissue.

Quantified ultrasound elastography in the assessment of cutaneous carcinoma

OBJECTIVE

To evaluate the feasibility of high-frequency ultrasound and ultrasound elastography (USE) in discriminating benign from malignant skin lesions in a prospective cohort study and to introduce the use of a "strain ratio" for evaluation of skin lesions.

METHODS

A commercial ultrasound system with a 14-MHz transducer was used to visualize skin lesions requiring biopsy on clinical evaluation. Anatomic ultrasound and USE imaging of the skin lesions was performed using 2- to 4-mm gel stand-off pads. A region of interest was manually selected over the area of each lesion with the lowest strain. The concept of a strain ratio of the compressibility of the normal skin at the corresponding layer to that of the least compressible region of a lesion in question was created and applied. This ratio was subsequently correlated with blind histopathological evaluation for malignancy.

RESULTS

55 patients were included in the study with a total of 67 lesions evaluated. 29 lesions were malignant and 38 benign. All malignant lesions had strain ratios ≥3.9. All benign lesions had strain ratios ≤3.0. A diagnostic value between 3.0 and 3.9 would result in 100% sensitivity and specificity in the characterization of these lesions as malignant.

CONCLUSION

This pilot study demonstrated that USE plus strain ratio appears to be a promising modality in providing diagnostic determination between cancerous and benign primary solitary skin lesions prior to biopsy.

ADVANCES IN KNOWLEDGE

This is the first reported study applying an original mathematical elastographic ratio, or strain ratio, to evaluate primary solitary skin lesions.

Skin and subcutaneous tissue strain in legs with lymphedema and lipodermatosclerosis

We compared skin and subcutaneous tissue strains in legs with lymphedema (LE) of varying severity and legs with lipodermatosclerosis (LDS) using real-time tissue elastography. Strain was assessed at the inner thigh and calf in 62 legs with LE (International Society of Lymphology [ISL] stage 0: 16, stage I: 5, stage II: 28, late stage II: 7, stage III: 6) and 15 legs with LDS. In thighs and calves with LE, skin strain and subcutaneous tissue strain did not significantly differ between ISL stage 0, that is, asymptomatic legs, and other stages. However, strain values in calves with LDS were lower than values in calves with stage 0, II and late II LE. These results indicate that skin and subcutaneous tissue strains were not lower in legs with symptomatic LE than in asymptomatic legs until an advanced stage.

Comparison of superior-level facet joint violations during open and percutaneous pedicle screw placement

BACKGROUND

Superior-level facet joint violation by pedicle screws may result in increased stress to the level above the instrumentation and may contribute to adjacent segment disease. Previous studies have evaluated facet joint violations in open or percutaneous screw cases, but there are no reports describing a direct institutional comparison.

OBJECTIVE

To compare the incidence of superior-level facet violation for open vs percutaneous pedicle screws and to evaluate patient and surgical factors that affect this outcome.

METHODS

We reviewed 279 consecutive patients who underwent an index instrumented lumbar fusion from 2007 to 2011 for degenerative spine disease with stenosis with or without spondylolisthesis. We used a computed tomography grading system that represents progressively increasing grades of facet joint violation. Patient and surgical factors were evaluated to determine their impact on facet violation.

RESULTS

Our cohort consisted of 126 open and 153 percutaneous cases. Percutaneous procedures had a higher overall violation grade (P = .02) and a greater incidence of high-grade violations (P = .006) compared with open procedures. Bivariate analysis showed significantly greater violations in percutaneous cases for age < 65 years, obesity, pedicle screws at L4, and 1- and 2-level surgeries. Multivariate analysis showed the percutaneous approach and depth of the spine to be independent risk factors for high-grade violations.

CONCLUSION

This study demonstrates greater facet violations for percutaneously placed pedicle screws compared with open screws.

Multi-directional in vivo tensile skin stiffness measurement for the design of a reproducible tensile strain elastography protocol

BACKGROUND/AIMS

Elastography is a promising new medical imaging modality, displaying spatial distribution of biomechanical properties such as local tissue strain response to an applied stress. To develop a reproducible test protocol for skin elastography, the effect of various parameters on skin stiffness measurements was investigated.

METHODS

The parameters investigated were: history of skin loading before test loading (preconditioning), direction of test loading (anisotropy) and posture (pre-stress). If a sample of skin is loaded, its stiffness will temporarily change. Finally, the reproducibility of skin stiffness and anisotropy measurements, using the developed techniques, was investigated.

RESULTS

By measuring how the stiffness changed with different time delays between loading cycles, the time required for healthy skin to return to its original pre-loaded state was in the region of 125 s. A second finding, which supports and extends previous work, was that skin stiffness varied with direction, by an approximate factor of 2, and that anisotropy was less apparent with preconditioned skin than non-preconditioned skin. Study of the effect of posture showed that care needs to be taken over which stiffness measure is used. For example, measurement of the load at a given displacement was found to be highly dependent on posture, whereas measurement of the phase III stiffness was independent of posture.

CONCLUSION

It was shown that when the measurement variables and methods of analysis were standardised, skin stiffness could be measured reproducibly enough to distinguish between the stiffest and softest directions, and that these methods allowed formation of skin elastograms free from confounding influences.

The recent progress in quantitative medical image analysis for computer aided diagnosis systems

Computer-aided diagnosis (CAD) has become one of the major research subjects in medical imaging and diagnostic radiology. Many different CAD schemes are being developed for use in the detection and/or characterization of various lesions found through various types of medical imaging. These imaging technologies employ conventional projection radiography, computed tomography, magnetic resonance imaging, ultrasonography, etc. In order to achieve a high performance level for a computerized diagnosis, it is important to employ effective image analysis techniques in the major steps of a CAD scheme. The main objective of this review is to attempt to introduce the diverse methods used for quantitative image analysis, and to provide a guide for clinicians.