Ultrasound Technology in Dermatology

High-Resolution Ultrasound of Odontogenic Cutaneous Sinus Tract: An International Multicentric Experience and a Review of the Literature

OBJECTIVES

To investigate the role of high-resolution ultrasound (HR-US) in the initial and differential diagnosis of the Odontogenic Cutaneous Sinus Tract (OCST) in a multicentric setting.

METHODS

Skin HR-US examinations of OCSTs performed between January 2019 and June 2023 at different Institutions were retrospectively reviewed. Epidemiological and clinical data (age, gender, location of the skin lesion, causative tooth, and the clinical suspicion) as well as HR-US imaging findings (morphology and length of the sinus tract, Doppler signal, and cortical bone interruption of maxilla or mandible) were collected. US examinations were performed by expert radiologists using a high-performance US scanner, employing a high-frequency linear probe (15 MHz or higher frequencies). In only one patient the HR-US exam was integrated with strain elastography (SE).

RESULTS

Sixteen patients were enrolled with a median age of 37.6 years (range 16-70 years). The most frequent clinical suspicion was epidermal cyst, while OCST was suspected in only two cases. In all cases, HR-US depicted the sinus tract as a nodular, triangular or "champignon-shaped" lesion in the subcutaneous layer, which continued with a slightly tortuous band structure, up to the focally interrupted cortical bone plate. Furthermore, color Doppler evaluation showed color signals around and/or within the lesion, expression of inflammation. On SE, the sinus tract showed a hard pattern, due to fibrous and granulomatous tissue.

CONCLUSIONS

HR-US, thanks to its high spatial resolution, allows the evaluation of OCST, and play a crucial diagnostic role, mainly when the clinical suspicious is different.

High-frequency photoacoustic and ultrasound imaging for skin evaluation: Pilot study for the assessment of a chemical burn

Skin architecture and its underlying vascular structure could be used to assess the health status of skin. A non-invasive, high resolution and deep imaging modality able to visualize skin subcutaneous layers and vasculature structures could be useful for determining and characterizing skin disease and trauma. In this study, a multispectral high-frequency, linear array-based photoacoustic/ultrasound (PAUS) probe is developed and implemented for the imaging of rat skin in vivo. The study seeks to demonstrate the probe capabilities for visualizing the skin and its underlying structures, and for monitoring changes in skin structure and composition during a 5-day course of a chemical burn. We analayze composition of lipids, water, oxy-hemoglobin, and deoxy-hemoglobin (for determination of oxygen saturation) in the skin tissue. The study successfully demonstrated the high-frequency PAUS imaging probe was able to provide 3D images of the rat skin architecture, underlying vasculature structures, and oxygen saturation, water, lipids and total hemoglobin.

One-Stop Shop: Diagnosis and Treatment of Basal Cell Carcinoma in One Step

Monitoring the tumor margins of basal cell carcinomas is still a challenge in everyday clinical practice. Usually, the clinical margins of the tumor are marked by the naked eye or, even better, with dermoscopy before surgery and then examined in detail after the operation using histological examination. In order to achieve tumor freedom, several surgical steps are sometimes necessary, meaning that patients spend longer periods in hospital and the healthcare system is burdened more as a result. One way to improve this is the one-stop shop method, which requires precise diagnostics and margin marking before and during surgery so that tumor freedom can be achieved after just one surgery. For this reason, the current status of the diagnosis and treatment of basal cell carcinomas before and after surgery is to be examined following extensive literature research using devices and methods that have already been tested in order to determine how a simplified process of tumor margin control of basal cell carcinomas can be made possible both in vivo and ex vivo.

Imaging the Micron: New Directions in Diagnosis with Ultra-High-Frequency Ultrasound

In recent decades, advancements in medical imaging technologies have revolutionized diagnostic and therapeutic approaches, enhancing the precision and efficacy of healthcare interventions [...].

Digitally Enhanced Methods for the Diagnosis and Monitoring of Treatment Responses in Actinic Keratoses: A New Avenue in Personalized Skin Care

Non-melanocytic skin cancers represent an important public health problem due to the increasing incidence and the important local destructive potential. Thus, the early diagnosis and treatment of precancerous lesions (actinic keratoses) is a priority for the dermatologist. In recent years, non-invasive skin imaging methods have seen an important development, moving from simple observational methods used in clinical research, to true diagnostic and treatment methods that make the dermatologist's life easier. Given the frequency of these precancerous lesions, their location on photo-exposed areas, as well as the long treatment periods, with variable, imprecise end-points, the need to use non-invasive imaging devices is increasingly evident to complete the clinical observations in the diagnosis and treatment of these lesions, with the aim of increasing accuracy and decreasing the adverse effects due to long treatment duration. This is the first review that brings together all skin imaging methods (dermoscopy, reflectance confocal microscopy, ultrasonography, dermoscopy-guided high frequency ultrasonography, and optical coherence tomography) used in the evaluation of actinic keratoses and their response to different treatment regimens.

The role of imaging technologies in the diagnosis of hidradenitis suppurativa

Hidradenitis suppurativa is a chronic, inflammatory, recurrent, and debilitating disease of the hair follicle. It presents with painful, deep-seated, inflamed lesions, such as nodules, abscesses, sinus tracts, and fistulas, generally located in the main folds. Clinical severity assessment alone can be reductive; noninvasive skin imaging technologies, such as ultrasound, magnetic resonance imaging, medical infrared thermography, computed tomography, and positron emission tomography, provide subclinical anatomical and functional details. These instrumental techniques confirm the clinical suspect, thus allowing an earlier diagnosis and improving patients' clinical evaluation, staging, and management. Finally, they might be helpful for preoperative mapping. In this contribution, we provide an overview of the current knowledge about noninvasive skin imaging techniques with a particular focus on ultrasonography, which is widely used thanks to its precision, versatility, and availability.

Quantitative Ultrasound Analysis of Oral Mucosa: An Observational Cross-Sectional Study

(1) Background: Ultrasonography is gaining popularity as a diagnostic tool in the study of the oral mucosa. The precision of ultrasound has made it possible to identify the various layers, based on their echogenicity. The aim of this study was to perform a quantitative analysis of healthy oral mucosa based on the analysis of greyscale, echo levels (dB), and attenuation values (dB/cm). (2) Methods: Thirty-three patients (17 females and 16 males; 58.42 ± 13.29 y.o) were recruited for this study. The images were acquired with the GE Logiq-e R7 with a linear probe at 18 MHz frequency (harmonic). For each tissue (epithelium, rete ridges, connective tissue, muscle, and bone), regions of interest were traced for the analysis of echo levels, grey levels, and attenuation values. One-way ANOVA and pairwise comparison were performed. (3) Results: Three-hundred and thirty images were analyzed. Analysis of echo levels and grey levels showed a significant difference between epithelium and rete ridges (p = 0.001), and between rete ridges and connective tissue (p = 0.001), but not between epithelium and connective tissue (p = 0.831) or connective and muscle layers (p = 0.383). The attenuation values appeared to be specific for each tissue layer (p = 0.001). (4) Conclusions: Quantitative analysis applied to ultrasound imaging of the oral mucosa allows the definition of specific tissue areas.

Recent Advances in Ultrasound Technology: Ultra-High Frequency Ultrasound for Reconstructive Supermicrosurgery

BACKGROUND

 Currently, microsurgeons are in the era of supermicrosurgery and perforator flap reconstruction. As these reconstructions frequently utilize vessels that are smaller than a single millimeter, understanding of location of lymphatic vessels and perforator anatomy preoperatively is essential. To change with the times, the role of ultrasound has changed from just an adjunct to primary imaging of the choice in reconstructive supermicrosurgery. Recently, a novel ultrasonographic technique involving the use of ultra-high frequency ultrasound (UHFUS) frequencies has entered the scene, and appears a promising tool in surgical planning.

METHODS

 The literatures on the applications of UHFUS in reconstructive supermicrosurgery were retrieved and reviewed from more than 60 literatures have been published on the surgical applications of UHFUS.

RESULTS

 Nine studies were retrieved from the literature on the applications of UHFUS in reconstructive supermicrosurgery. The articles report both application for lymphatic surgery and perforator flaps.

CONCLUSIONS

 UHFUS application involves an increasing number of reconstructive supermicrosurgery field. UHFUS is a valuable and powerful tool for any reconstructive surgeons who are interested in performing supermicrosurgery.

Imaging sebaceous gland using optical coherence tomography with deep learning assisted automatic identification

Imaging sebaceous glands and evaluating morphometric parameters are important for diagnosis and treatment of serum problems. In this article, we investigate the feasibility of high-resolution optical coherence tomography (OCT) in combination with deep learning assisted automatic identification for these purposes. Specifically, with a spatial resolution of 2.3 μm × 6.2 μm (axial × lateral, in air), OCT is capable of clearly differentiating sebaceous gland from other skin structures and resolving the sebocyte layer. In order to achieve efficient and timely imaging analysis, a deep learning approach built upon ResNet18 is developed to automatically classify OCT images (with/without sebaceous gland), with a classification accuracy of 97.9%. Based on the result of automatic identification, we further demonstrate the possibility to measure gland size, sebocyte layer thickness and gland density.

High-frequency ultrasound in clinical dermatology: a review

Background

Ultrasound was first introduced in clinical dermatology in 1979. Since that time, ultrasound technology has continued to develop along with its popularity and utility.

Main text summary

Today, high-frequency ultrasound (HFUS), or ultrasound using a frequency of at least 10 megahertz (MHz), allows for high-resolution imaging of the skin from the stratum corneum to the deep fascia. This non-invasive and easy-to-interpret tool allows physicians to assess skin findings in real-time, enabling enhanced diagnostic, management, and surgical capabilities. In this review, we discuss how HFUS fits into the landscape of skin imaging. We provide a brief history of its introduction to dermatology, explain key principles of ultrasonography, and review its use in characterizing normal skin, common neoplasms of the skin, dermatologic diseases and cosmetic dermatology.

Conclusion

As frequency advancements in ultrasonography continue, the broad applications of this imaging modality will continue to grow. HFUS is a fast, safe and readily available tool that can aid in diagnosing, monitoring and treating dermatologic conditions by providing more objective assessment measures.

The use of high-frequency skin ultrasound in the diagnosis of lipodermatosclerosis

Introduction

Lipodermatosclerosis is a symptom of severe venous insufficiency, the diagnosis of which is based on the clinical picture. Although the histopathology of the skin and the subcutaneous tissue allows for the most reliable diagnosis, it is not recommended due to healing disorders.

Aim

The aim of this study was to assess the usefulness of high-frequency ultrasound in the diagnosis of lipodermatosclerosis.

Materials and methods

The study included 10 patients with lipodermatosclerosis who underwent Duplex Doppler ultrasound of lower limb veins, high-frequency ultrasound of the tibial skin, and radiography of the lower leg, all of which were analyzed in correlation with clinical symptoms.

Results

The study group included 9 women and 1 man aged 39–81 years. Manifestations of lipodermatosclerosis were detected in 14 limbs. High-frequency ultrasound showed that the mean dermis thickness at the affected sites was 2.63 mm, and was significantly thicker compared to healthy skin (1.45 mm) (p = 0.00002). Higher echogenicity was detected in the affected body regions in 85.7% of cases for the skin and 92.9% of cases for the subcutaneous tissue. Subcutaneous and vascular wall calcifications were detected in 92.9% and 78.6% of cases, respectively. Fibrosis was observed in all limbs, and compression sonoelastography showed that the compliance of the subcutaneous tissue was lower than that of muscles. The border between the skin and the subcutaneous tissue was blurred in 57.1% of cases. Radiography revealed thickening of the affected skin regions in all limbs, with calcifications detected in 85.7% of cases. A blurred border between the skin and the subcutaneous tissue was observed in 35.7% of limbs.

Conclusion

High-frequency ultrasonography of the skin and the subcutaneous tissue in the lower legs supported with radiological findings is highly useful in the diagnosis of lipodermatosclerosis.

High-frequency ultrasound in the 21st century

The beginnings of skin ultrasound date back to about 50 years ago. However, the dynamic progress of skin ultrasound took place in the last twenty years, when the unprecedented development of computer technologies occurred, which resulted in the popularization of and easier access to modern ultrasound equipment. Skin tests can be performed with both classic scanners equipped with broadband transducers with a minimum frequency of 15 MHz, and specially dedicated skin systems with high-frequency scanners, which are equipped with mechanical transducers with a frequency of 20 MHz to up to 100 MHz. Owing to technologically advanced machines, ultrasonography has proved to be useful in many areas. The aim of this study was to present the current knowledge and possibilities of skin imaging using high-frequency ultrasonography. Te paper discusses technical aspects, types of devices available on the market, as well as methods for the analysis of ultrasound skin images and parameters useful in their interpretation. We also present current applications of skin ultrasound, with particular emphasis on dermatology and aesthetic medicine. In the field of dermatology, we discussed imaging of focal lesions as well as an assessment of pathologically changed skin and treatment monitoring. We also focused on the use of high-frequency ultrasonography in aesthetic medicine and cosmetology. The popularity of this method is constantly growing in these fields, and ultrasound is now used in everyday practice to assess the skin, plan and monitor procedures, as well as to treat potential complications. High-frequency ultrasonography is a highly effective method for skin evaluation, although still underappreciated in may fields. Further research is needed to standardize this modality, as well as to implement training for operators, and to popularize this imaging technique.

The efficacy of high-frequency ultrasound-guided injection lipolysis in reducing fat deposits located on the inside of the knees

Introduction

Many women consider local fat deposits unacceptable for aesthetic reasons as they have negative impact on appearance and thus, contribute to reduced self-esteem. Injection lipolysis (intralipotherapy) may be an alternative for conventional liposuction in reducing fat deposits.

Aim

The aim of this paper was to assess the efficacy of high-frequency ultrasound-guided injection of deoxycholic acid (intralipotherapy) to remove fat deposits on the inner side of knees.

Materials and methods

The procedure was performed in 7 women (14 inner sides of knees). The formulation was administered under high-frequency ultrasound guidance. The procedure was performed twice at 4-week intervals in each patient. High-frequency ultrasound guidance was used to monitor such parameters as the thickness of the dermis (DermaMed, Dramiński S.A.) or the subcutaneous tissue (Philips Epiq 5, USA). Ultrasound was performed both before and after treatment. Additionally, anthropometric measurements were taken, a questionnaire was performed, and a photographic documentation was recorded.

Results

Reduction in knee circumference and subcutaneous tissue occurred in 71.42% of patients.

Conclusions

Intralipolysis with deoxycholic acid formulation is an effective method for reducing fat deposits on the inner part of the knees. Ultrasonography proved to be a useful method to monitor the procedure (correct administration of the preparation) and to assess treatment outcomes. A small sample size was a limitation of our study; therefore further studies are needed.

The Application of Ultra-High-Frequency Ultrasound in Dermatology and Wound Management

The management of lower extremity wounds is frequently performed by means of clinical examination, representing a challenge for the clinician due to the various conditions that can potentially enter differential diagnosis. Several diagnostic techniques are available in the dermatologist’s arsenal as a support to diagnosis confirmation, including dermoscopy and ultrasonography. Recently, a novel ultrasonographic technique involving the use of ultra-high ultrasound frequencies has entered the scene, and appears a promising tool in the diagnostic workup of skin ulcerative lesions. The focus of this review is to discuss the potential role of ultra-high-frequency ultrasonography in the diagnostic workup of wounds in the light of the current applications of the technique.

Photoacoustic Imaging as a Tool for Assessing Hair Follicular Organization

Follicular unit extraction (FUE) and follicular unit transplantation (FUT) account for 99% of hair transplant procedures. In both cases, it is important for clinicians to characterize follicle density for treatment planning and evaluation. The existing gold-standard is photographic examination. However, this approach is insensitive to subdermal hair and cannot identify follicle orientation. Here, we introduce a fast and non-invasive imaging technique to measure follicle density and angles across regions of varying density. We first showed that hair is a significant source of photoacoustic signal. We then selected regions of low, medium, and high follicle density and showed that photoacoustic imaging can measure the density of follicles even when they are not visible by eye. We performed handheld imaging by sweeping the transducer across the imaging area to generate 3D images via maximum intensity projection. Background signal from the dermis was removed using a skin tracing method. Measurement of follicle density using photoacoustic imaging was highly correlated with photographic determination (R² = 0.96). Finally, we measured subdermal follicular angles-a key parameter influencing transection rates in FUE.

Use of imaging techniques for melanocytic naevi and basal cell carcinoma in integrative analysis (Review)

Early detection of skin cancer is essential in order to obtain an improved prognosis. Clinicians need more objective and non-invasive examination methods to support their decision whether to biopsy or not tumoral lesions. These may include several imaging techniques such as dermoscopy, videodermoscopy, also known as sequential digital dermoscopy (SDD), computer-aided diagnosis (CAD), total body photography, imaging and high-frequency ultrasonography (HFUS), reflectance confocal microscopy, multiphoton tomography, electrical impedance spectroscopy, Raman spectroscopy, stepwise two-photon-laser spectroscopy and quantitative dynamic infrared. This review summarizes the current developments in the field of melanocytic lesions, such as naevi and basal cell carcinoma (BCC) imaging techniques. The aim was to collect and analyze data concerning types, indications, advantages and disadvantages of modern imaging techniques for in vivo skin tumor diagnosis. Two main methods were focused on, namely videodermoscopy and HFUS, which can be included in daily dermatologists' practice. In skin tumors HFUS allows the assessment of tumoral lesions with depth smaller than 1.5 cm, being described a correlation between ultrasonographic depth and the histologic index.

The usefulness of high-frequency ultrasonography in the evaluation of vulvar dermatoses in postmenopausal women - a preliminary report

Introduction

The vulva is an external female genital organ with complex anatomy and histology. In postmenopausal women, this region is at particular risk of different types of conditions known as dermatoses.

Materials and methods

We assessed benign vulvar skin lesions using high-frequency 48 MHz ultrasound transducer (DermaView) prior to biopsy or excision. We compared ultrasonographic images with histology.

Results

We assessed benign vulvar lesions such as folliculitis, condylomata acuminatum, lichen sclerosus and vulvar intraepithelial neoplasia. We presented typical high-frequency images of these pathologies and compared them with histological images.

Conclusion

Our preliminary study confirms that high-frequency ultrasonography is a useful tool in the assessment of vulvar pathologies, especially before surgical excision. A precise visualization of certain pathologies like folliculitis, lichen sclerosus, condylomata and vulvar intraepithelial neoplasia is possible.

Early diagnosis of skin cancer by ultrasound frequency analysis

The diagnosis of cancer by modern computer tools, at the very first stages of the incident, is a very important issue that has involved many researchers. In the meantime, skin cancer is a great deal of research because many people are involved with it. The purpose of this paper is to introduce an innovative method based on tissue frequency analyzes to obtain the accurate and real-time evaluation of skin cancers. According to the Biological resonance theory, body cells have natural and unique frequencies based on their biological fluctuations, which, if the structure, profile and cellular status change, its frequency also varies. This concept and theory is considered as the basis for analyzing skin tissue health in the proposed method. Reflected ultrasound waves from tissue have been processed and studied based on frequency analysis as a new method for early detection and diagnosis of accurate location and type of skin diseases. The developed algorithm was approved through 400 patients from CRED; its ability to evaluate benign and malignant skin lesions was shown (AUC = 0.959), with comparable clinical precision; as for the selected threshold, sensitivity, and specificity were 93.8% and 97.3%, respectively. Therefore, this method can detect skin malignancy with an accurate, noninvasive and real-time procedure.

Gender- and age-related differences in facial sebaceous glands in Asian skin, as observed by non-invasive analysis using three-dimensional ultrasound microscopy

BACKGROUND

While determining sebaceous gland morphology is useful in the treatment of skin disorders such as acne, a non-invasive assessment method has not been developed. Since age and gender affect sebum level, differences in sebaceous gland morphology according to these factors were investigated.

METHODS

Facial skin was measured using a high-frequency three-dimensional ultrasound microscope. First, the ultrasound images were compared with skin sections. Next, we assessed sebaceous gland morphology. Images of sebaceous gland in the cheeks of young male, young female and elderly female subjects were obtained using ultrasound microscopy, and en face images were processed to measure the sebaceous gland area.

RESULTS

In the ultrasound images, sebaceous glands and also thin collagen fibers, which surrounded the glands, could be detected as low-intensity regions. We called them sebaceous units. In young male subjects, the sebaceous unit areas 900-μm beneath the skin surface were larger than those at 700 μm. In contrast, depth-dependent differences in sebaceous unit area were not observed in young female subjects, indicating that males had cauliflower-shaped sebaceous glands while young females had somewhat more cylindrical and smaller sebaceous glands than the young males. Regarding age, the areas of sebaceous units at 900 μm were diminished and the depth of maximum area was shallower in elderly female subjects compared to young female subjects. Hence, sebaceous glands are considered to shrink with age.

CONCLUSION

Differences in facial sebaceous unit morphology between genders as well as by age groups could be observed using high-frequency ultrasound microscopy.

Lipoma removal using a high-frequency ultrasound-guided injection of a Class III CE-marked device-Empirical findings

BACKGROUND

Lipomas are very common benign neoplasms, which constitute 99% of all adipose-derived tumors. Main treatment option includes surgical excision, which is unacceptable for a number of patients seeking ways to improve esthetic appearance of their skin. Therefore, alternative treatment options are being sought.

OBJECTIVE

The aim of the present study was to assess the efficacy of lipoma removal using a Class III CE-marked device (Aqualyx™) administered as a high-frequency ultrasound-guided injection (intralipotherapy).

METHODS

A total of 17 lipomas were treated. The procedure involved a high-frequency ultrasound-guided injection. A maximum of 3 injections per a lipoma were performed. High-frequency ultrasound was used for assessing the size of lipomas and monitoring treatment-induced changes to the lipomas and adjacent tissue.

RESULTS

Response to treatment was achieved in all cases. A complete removal was achieved in 70.59% of lipomas. The remaining 29.41% of lipomas were not completely removed, yet significantly reduced in size.

CONCLUSION

An injection of Aqualyx™, a CE-marked drug, is a good noninvasive treatment of lipomas. Ultrasound guided procedure is recommended, as it ensures appropriate technique and enables monitoring treatment-induced changes. Considering a low number of published reports of such treatment, it is crucial to continue this research.

Current applications of high-frequency ultrasonography in dermatology

The era of ultrasounds in dermatology started in 1979, when pioneering use of 15 MHz by Alexander and Miller in measuring the skin thickness was introduced. Since then, some new applications of high-frequency ultrasonography (HF-USG) have emerged providing the clinicians with an extra hand in their everyday practice. The main advantages of HF-USG include the possibility of real-time imaging, measurements of morphological and physiological aspects of the skin, safety associated with the use of non-ionizing media as well as the lack of contraindications to its performance. Currently the main clinical use of HF-USG in dermatology regards preoperative assessment of the depth of invasion in melanomas and basal cell carcinomas. The ultrasound image analysis allows noninvasive follow-up of inflammatory skin diseases, like atopic dermatitis, psoriasis and may be used for monitoring effectiveness of therapy in skin lymphomas and sclerotic skin diseases.

Efficacy of intradermal mesotherapy in cellulite reduction - Conventional and high-frequency ultrasound monitoring results

BACKGROUND

Cellulite affects the majority of women and is an unacceptable cosmetic defect. Therefore, effective methods for cellulite reduction are being sought. Intradermal mesotherapy is one of such methods.

OBJECTIVE

The aim of the study was to assess the efficacy of intradermal mesotherapy in cellulite reduction, using conventional and high-frequency ultrasound.

METHODS

Twenty-one women with cellulite underwent a series of intradermal mesotherapy procedures. The following parameters were assessed: thickness of epidermis, dermis and hypodermis, echogenicity of dermis and the surface area of serrated hypodermis-dermis junction. Furthermore, the thigh circumference was measured; body mass index and cellulite severity were assessed based on photographs using Nürnberger-Müller's scale.

RESULTS

Intradermal mesotherapy reduced severity of cellulite. The surface area of serrated hypodermis-dermis junction and hypodermis thickness decreased significantly as compared to baseline. Cellulite reduction was also confirmed by palpation, decreased thigh circumference and the Nürnberger-Müller's grade. There were no statistically significant changes in epidermis or dermis thickness, body weight and the BMI.

CONCLUSION

Intradermal mesotherapy offers effective cellulite reduction. It is a simple and safe treatment, which makes it popular. Further research in mesotherapy is essential due to a limited number of published studies. Ultrasound is a useful method to monitor intradermal mesotherapy and assess its efficacy.

Segmentation of Skin Tumors in High-Frequency 3-D Ultrasound Images

High-frequency 3-D ultrasound imaging is an informative tool for diagnosis, surgery planning and skin lesion examination. The purpose of this article was to describe a semi-automated segmentation tool providing easy access to the extent, shape and volume of a lesion. We propose an adaptive log-likelihood level-set segmentation procedure using non-parametric estimates of the intensity distribution. The algorithm has a single parameter to control the smoothness of the contour, and we describe how a fixed value yields satisfactory segmentation results with an average Dice coefficient of D = 0.76. The algorithm is implemented on a grid, which increases the speed by a factor of 100 compared with a standard pixelwise segmentation. We compare the method with parametric methods making the hypothesis of Rayleigh or Nakagami distributed signals, and illustrate that our method has greater robustness with similar computational speed. Benchmarks are made on realistic synthetic ultrasound images and a data set of nine clinical 3-D images acquired with a 50-MHz imaging system. The proposed algorithm is suitable for use in a clinical context as a post-processing tool.

Morphologic features of basal cell carcinoma using the en-face mode in frequency domain optical coherence tomography

BACKGROUND

Optical coherence tomography (OCT) has become a valuable non-invasive tool in the in vivo diagnosis of non-melanoma skin cancer, especially of basal cell carcinoma (BCC). Due to an updated software-supported algorithm, a new en-face mode - similar to the horizontal en-face mode in high-definition OCT and reflectance confocal microscopy - surface-parallel imaging is possible which, in combination with the established slice mode of frequency domain (FD-)OCT, may offer additional information in the diagnosis of BCC.

OBJECTIVES

To define characteristic morphologic features of BCC using the new en-face mode in addition to the conventional cross-sectional imaging mode for three-dimensional imaging of BCC in FD-OCT.

METHODS

A total of 33 BCC were examined preoperatively by imaging in en-face mode as well as cross-sectional mode in FD-OCT. Characteristic features were evaluated and correlated with histopathology findings.

RESULTS

Features established in the cross-sectional imaging mode as well as additional features were present in the en-face mode of FD-OCT: lobulated structures (100%), dark peritumoral rim (75%), bright peritumoral stroma (96%), branching vessels (90%), compressed fibrous bundles between lobulated nests ('star shaped') (78%), and intranodular small bright dots (51%). These features were also evaluated according to the histopathological subtype. In the en-face mode, the lobulated structures with compressed fibrous bundles of the BCC were more distinct than in the slice mode.

CONCLUSION

FD-OCT with a new depiction for horizontal and vertical imaging modes offers additional information in the diagnosis of BCC, especially in nodular BCC, and enhances the possibility of the evaluation of morphologic tumour features.

Guidelines for Performing Dermatologic Ultrasound Examinations by the DERMUS Group

OBJECTIVES

To support standardization for performing dermatologic ultrasound examinations.

METHODS

An international working group, called DERMUS (Dermatologic Ultrasound), was formed, composed of physicians who have been working on a regular basis and publishing in peer-reviewed articles on dermatologic ultrasound. A questionnaire on 5 critical issues about performance of the examinations was prepared and distributed by e-mail. The areas of discussion included technical aspects, main areas of application, minimum number of examinations per year required for assessing competence, qualifications of the personnel in charge of the examination, and organization of courses. Final recommendations were approved on the basis of the agreement of more than 50% of the members.

RESULTS

The minimum frequency recommended for performing dermatologic examinations was 15 MHz. Routine use of color Doppler ultrasound and the performance of spectral curve analysis for assessing the main vascularity of lesions were suggested. Three-dimensional reconstructions were considered optional. The main dermatologic applications were benign tumors, skin cancer, vascular anomalies, cosmetic field, nail disorders, and inflammatory diseases. The minimum number of examinations per year suggested by the group for assessing competence was 300. A physician and not a sonographer was recommended to be the person in charge of performing the examination. On course organization, a minimum of 2 levels of complexity (basic and advanced) was suggested.

CONCLUSIONS

There is a need to standardize the performance and quality of dermatologic ultrasound examinations. The present guidelines written by an international group of specialists in the field may support this objective.

[Methods for measuring skin aging]

Aging affects human skin and is becoming increasingly important with regard to medical, social and aesthetic issues. Detection of intrinsic and extrinsic components of skin aging requires reliable measurement methods. Modern techniques, e.g., based on direct imaging, spectroscopy or skin physiological measurements, provide a broad spectrum of parameters for different applications.

[High-resolution ultrasonography for differential diagnosis between nodular basal carcinoma and sebaceous hyperplasia of the face: A pilot study]

BACKGROUND

Clinical differential diagnosis between incipient nodular basal carcinoma (NBC) and sebaceous hyperplasia (SH) of the face is difficult in some cases. A comparative histological analysis of these two entities led us to the hypothesis that 20MHz high-resolution ultrasonography (HRUS) may enable differentiation between NBC and SH.

PATIENTS AND METHODS

Seventy-seven facial tumours requiring histological confirmation to distinguish between NBC and SH were scanned using HRUS before excision. No other imaging technique was used. The ultrasound scans were submitted to two blinded reviewers who were asked to classify the ultrasound pictures of the tumours as either hypoechoic or isoechoic/hyperechoic. Hypoechogenicity was defined as a diagnostic criterion for NBC.

RESULTS

Reviewer response reproducibility for 2 images of the same tumour was 90%. Both reviewers agreed regarding the echogenicity classification of an image in 87.4% of cases. The sensitivity of the procedure was 90.9% for detection of NBC and 89.4% for detection of malignant lesions. Specificity was 69.6% for detection of basal cell carcinomas and 78.8% for detection of malignant lesions.

DISCUSSION

HRUS is a non-invasive examination technique with excellent sensitivity for the detection of NBC in differential diagnosis with SH. Hypoechogenicity is not specific to NBC. The sensitivity of HRUS in our study suffered as a result of ultrasonography difficulties regarding unexpected differential diagnoses of NBC as well as tumour localisation in seborrhoeic areas.

[High frequency ultrasound]

Diagnostic ultrasound has become a standard procedure in clinical dermatology. Devices with intermediate high frequencies of 7.5-15 MHz are used in dermato-oncology for the staging and postoperative care of skin tumor patients and in angiology for improved vessel diagnostics. In contrast, the high frequency ultrasound systems with 20-100 MHz probes offer a much higher resolution, yet with a lower penetration depth of about 1 cm. The main indications are the preoperative measurements of tumor thickness in malignant melanoma and other skin tumors and the assessment of inflammatory and soft tissue diseases, offering information on the course of these dermatoses and allowing therapy monitoring. This article gives an overview on technical principles, devices, mode of examination, influencing factors, interpretation of the images, indications but also limitations of this technique.

Depth determination of skin cancers treated with superficial brachytherapy: ultrasound vs. histopathology

PURPOSE

The purpose of this study is to compare high frequency ultrasonography (HFUS) and histpathologic assessment done by punch biopsy in order to determine depth of basal cell carcinoma (BCC), in both superficial and nodular BCCs prior to brachytherapy treatment.

MATERIAL AND METHODS

This study includes 20 patients with 10 superficial and 10 nodular BCCs. First, punch biopsy was done to confirm the diagnosis and to measure tumour depth (Breslow rate). Subsequently, HFUS was done to measure tumour depth to search for correlation of these two techniques.

RESULTS

Neither clear tendency nor significance of the punch biopsy vs. HFUS depth determination is observed. Depth value differences with both modalities resulted patient dependent and then consequence of its uncertainty. Conceptually, HFUS should determine the macroscopic lesion (gross tumour volume - GTV), while punch biopsy is able to detect the microscopic extension (clinical target volume - CTV). Uncertainties of HFUS are difficult to address, while punch biopsy is done just on a small lesion section, not necessarily the deepest one.

CONCLUSIONS

According to the results, HFUS is less accurate at very shallow depths. Nodular cases present higher depth determination differences than superficial ones. In our clinical practice, we decided to prescribe at 3 mm depth when HFUS measurements give depth lesion values smaller than this value.

Reference characterisation of sound speed and attenuation of the IEC agar-based tissue-mimicking material up to a frequency of 60 MHz

To support the development of clinical applications of high-frequency ultrasound, appropriate tissue-mimicking materials (TMMs) are required whose acoustic properties have been measured using validated techniques. This paper describes the characterisation of the sound speed (phase velocity) and attenuation coefficient of the International Electrotechnical Commission (IEC) agar-based TMM over the frequency range 1 to 60 MHz. Measurements implemented a broadband through-transmission substitution immersion technique over two overlapping frequency ranges, with co-axially aligned 50 MHz centre-frequency transducers employed for characterisation above 15 MHz. In keeping with usual practice employed within the technical literature, thin acoustic windows (membranes) made of 12-μm-thick Mylar protected the TMM from water damage. Various important sources of uncertainty that could compromise measurement accuracy have been identified and evaluated through a combination of experimental studies and modelling. These include TMM sample thickness, measured both manually and acoustically, and the influence of interfacial losses that, even for thin protective membranes, are significant at the frequencies of interest. In agreement with previous reports, the attenuation coefficient of the IEC TMM exhibited non-linear frequency dependence, particularly above 20 MHz, yielding a value of 0.93 ± 0.04 dB cm(-1) MHz(-1) at 60 MHz, derived at 21 ± 0.5°C. For the first time, phase velocity, measured with an estimated uncertainty of ±3.1 m s(-1), has been found to be dispersive over this extended frequency range, increasing from 1541 m s(-1) at 1 MHz to 1547 m s(-1) at 60 MHz. This work will help standardise acoustic property measurements, and establishes a reference measurement capability for TMMs underpinning clinical applications at elevated frequencies.

Ultrasound and fine-needle aspiration in dermatology, underuse of minimally invasive, efficient diagnostic tools

BACKGROUND

Ultrasound imaging and ultrasound-guided fine-needle aspiration (FNA) are common procedures used to evaluate and sample cutaneous and subcutaneous tissue. Although ultrasound and FNA have been explored for individual neoplasms, lymph node involvement, and metastases, their use in day-to-day dermatology is not well defined.

OBJECTIVE

To investigate the use and utility of ultrasound and FNA in the dermatologic surgery division of a large academic institution.

METHODS

Retrospective case review of all ultrasound and FNA procedures ordered by a dermatologic surgeon over a 3-year period.

RESULTS

Metastatic disease was suspected in 11 of 21 (52.4%) cases. Cytology confirmed the presence of metastatic disease in two of the 11 cases, and metastatic disease was identified in one additional case in which the diagnosis was not suspected at clinical presentation. Cytology revealed leukemia or lymphoma in three (14.3%) cases, two of which were new diagnoses. Sonographic imaging and cytology revealed a benign diagnosis in 16 (76.2%) cases, five of which were reactive lymph nodes.

CONCLUSIONS

The results suggest that ultrasound and FNA are underused techniques that may play an important role in dermatology diagnostics and have the potential for expansion in day-to-day clinical practice.

High-resolution ultrasound imaging of cutaneous lesions

High-resolution variable frequency ultrasound imaging is increasingly being used in the noninvasive evaluation of various cutaneous diseases. It plays a complimentary role to physical examination in the assessment of cutaneous lesions. It is the only imaging modality useful in the evaluation of superficial cutaneous lesions that are too small to be evaluated on computed tomography (CT) or magnetic resonance imaging (MRI) and is helpful in reducing invasive procedures like biopsies and fine needle aspirations. In this article, we seek to describe the relevance and basic principles of cutaneous ultrasound, imaging findings of normal skin, current applications of high-resolution ultrasound in the diagnosis and management of various dermatological conditions, along with the features of some commonly encountered lesions.

Basal cell carcinoma - diagnosis

Basal cell carcinoma is the most common skin cancer in the Caucasian population. The cancer arises in sun exposed areas of the skin. The incidence of morbidity is high and it is still growing. The metastatic rate is low, but the enlarging tumor may cause severe tissue disfigurement and a poor cosmetic outcome. The diagnosis is usually clinical but there are many subtypes of this carcinoma and correct diagnosis is the clue to appropriate treatment of the lesion. The main problem in basal cell carcinoma management is the high recurrence rate.

Ultrasound image of the skin, apparatus and imaging basics

Ultrasound imaging of the skin is becoming more and more popular. Skin ultrasound examinations are used both in order to assess healthy skin and to evaluate pathological lesions. They are mainly performed in dermatology as well as in broadly understood aesthetic medicine and cosmetology. At present, skin imaging is enabled by high-frequency equipment and high-quality conventional devices. The introduction of high-frequency electronic transducers which are supported by conventional scanners may be a turning point in skin ultrasound equipment. Irrespective of the ultrasound scanner, three layers may be distinguished in the image of the healthy skin: epidermal echo, dermis and subcutaneous tissue. High-frequency equipment allows for detailed imaging of the epidermal echo, dermis and upper part of the subcutaneous tissue. It is also possible to visualize the skin appendages (hair with follicles and nails) as well as slight vessels that run in the dermis and upper subcutaneous tissue. Contrary to high-frequency equipment, conventional scanners do not allow for a detailed assessment of the epidermal and dermal echoes. Instead, they enable the visualization of the entire subcutaneous tissue. The following parameters are used for the assessment of skin ultrasound images: thickness of individual skin layers, caliber of blood vessels, echogenicity of the dermis or its individual layers, echogenicity of the subcutaneous tissue as well as the presence or absence of flow in slight venous vessels. Currently, the studies on the usage of sonoelastography for skin assessment are in progress. Considering the dynamic development of skin imaging equipment and its diagnostic possibilities, one might suspect that high-frequency examinations will become more common and will be fundamental for the evaluation of both healthy and pathologically altered skin. This paper is an introduction to a series of articles on the clinical application of high-frequency ultrasound. The next articles will be published in the subsequent issues.

Ultrasonographic staging of cutaneous malignant tumors: an ultrasonographic depth index

The objective of this paper is to assess the role of conventional and high-frequency ultrasound in the evaluation of the depth of cutaneous skin cancer. The study was performed on 46 subjects, divided into 3 categories, according to their skin pathology [basal cell carcinoma (BCC), 18 subjects; superficial spreading melanoma (SSM), 8 subjects; nodular melanoma (NM), 20 subjects]. Conventional and high-frequency ultrasonographic measurements were performed in order to assess the thickness of the tumors and the vascularization degree. We compared the mean values of the tumoral thickness obtained by using ultrasound (ultrasonographic depth index) with the histological depth index, obtained after performing histological sections stained with hematoxylin-eosin, and specific monoclonal antibodies in case of pigmented tumors. We established a correlation index between the histological and ultrasonographic values of the tumoral thickness. We found a strong correlation between the ultrasonographic index (measured by high-frequency sonography) and the histological index for nodular BCC (correlation of 98.4 %), NM subjects (correlation of 98.4 %), and SSM subjects (correlation of 99.4 %). An increase of the blood supply was noticed in nodular lesions only. Ultrasonography allows a very accurate assessment of skin cancer. The ultrasonographic depth index can be considered an objective, non-invasive marker for cutaneous tumors, comparable to the histological one, with a very good sensitivity (98-99 %).

Broadband focusing ultrasonic transducers based on dimpled LiNbO3 plate with inversion layer

A high-frequency broadband focusing transducer based on dimpled LiNbO(3) inversion layer plate has been fabricated and characterized. A spherical surface with a curvature radius of 6 mm is formed on the half-thickness LiNbO(3) inversion layer plate of Y36° cut orientation. The domain structure in the cross section is observed after a hydrofluoric acid etching process. For transducer fabrication, conductive epoxy is used as the backing material and polymer is deposited on the front face as the matching layer. The center frequency, bandwidth, and insertion loss of the focused transducer are measured to be 72 MHz, 136%, and -32 dB, respectively. The focused transducer has been successfully used for rabbit eyeball imaging and a better imaging capability compared with the planar transducer has been demonstrated. These promising results prove that the dimpled LiNbO(3) inversion layer plate has great potential for fabrication of high-frequency broadband focusing ultrasonic transducers.

High-resolution ultrasound imaging of human skin in vivo by using three-dimensional ultrasound microscopy

Observing the morphology of human skin is important in the diagnosis of skin cancer and inflammation and in the assessment of skin aging. High-frequency ultrasound imaging provides high spatial resolution of the deep layers of the skin, which cannot be visualized by optical methods. The objectives of the present study were to develop a three-dimensional (3-D) ultrasound microscope and to observe the morphology of normal human skin in vivo. A concave polyvinylidene fluoride transducer with a central frequency of 120 MHz was excited using an electric pulse generated by semiconductor switching. The transducer was scanned two-dimensionally by using two linear motors on the region-of-interest and the ultrasonic reflection was digitized with 2-GHz sampling. Consecutive B-mode images perpendicular to the skin surface were reconstructed to generate multiplanar reconstructed images and 3-D volume-rendering images clearly showing microstructures such as sebaceous glands and hair follicles. The 3-D ultrasound microscope could be used to successfully image the morphology of human skin noninvasively and may provide important information on skin structure.

High-definition optical coherence tomography enables visualization of individual cells in healthy skin: comparison to reflectance confocal microscopy

High-definition OCT (HD-OCT) is an innovative technique based on the principle of conventional OCT. Our objective was to test the resolution and image quality of HD-OCT in comparison with reflectance confocal microscopy (RCM) of healthy skin. Firstly, images have been made of a ultra-high-resolution line-pair phantome with both systems. Secondly, we investigated 21 healthy volunteers of different phototypes with HD-OCT and RCM on volar forearm and compared the generated images. HD-OCT displays also differences depending on the skin phototype and anatomical site. The 3-μm lateral resolution of the HD-OCT could be confirmed by the phantom analysis. The identification of cells in the epidermis can be made by both techniques. RCM offers the best lateral resolution, and HD-OCT has the best penetration depth, providing images of individual cells deeper within the dermis. Eccrine ducts and hair shafts with pilosebaceous units can be observed depending on skin site. HD-OCT provides morphological imaging with sufficient resolution and penetration depth to permit visualization of individual cells at up to 570 μm in depth offering the possibility of additional structural information complementary to that of RCM. HD-OCT further has the possibility for rapid three-dimensional imaging.

Previously reported sonographic appearances of regional melanoma metastases are not likely due to necrosis

OBJECTIVES

Sonography has proven to be a reliable tool in early detection of lymph node and in-transit cutaneous-subcutaneous metastases. Those metastases normally appear as hypoechoic or even anechoic lesions on sonography. It has been assumed that this appearance is due to necrosis of the lesions, but so far, that assumption has never been proven. The purpose of this retrospective study was to evaluate whether the hypoechoic appearance of melanoma metastasis is really due to tumor necrosis.

METHODS

From a radiographic database, we retrieved 212 melanoma cases imaged with sonography over a 2-year period for disease staging or follow-up. We selected 37 positive cases with 84 nodal and extranodal (satellite and in-transit) metastatic lesions and reviewed the sonograms and pathologic slides (slides available for 40 of 84 lesions). We retrospectively assessed the vascularization pattern (color Doppler images available for 78 of 84 lesions), categorizing it as poor, intermediate, or consistent. We also looked for necrosis on the histopathologic material, categorizing it into scores of 0, 1, 2, and 3 for absence of necrosis, less than 20% necrosis, 20% to 40% necrosis, and greater than 40% necrosis, respectively.

RESULTS

Despite their gray scale appearance, most melanoma lesions were vascularized on color Doppler imaging and showed limited necrosis at histopathologic analysis. Consistent vascularization on Doppler imaging, excluding substantial necrosis, was found in 44 of 78 lesions (56.4%). Poor vascularization on Doppler imaging, suggesting necrosis, was present in only 14% of the lesions. Substantial necrosis (scores of 2 and 3) was found pathologically in only 10% of the lesions.

CONCLUSIONS

Necrosis seems to be an uncommon event in melanoma metastasis and is probably not the basis for its low-level echo pattern on sonography. The hypoechoic appearance is very typical of melanoma metastasis and is likely due to massive melanomatous infiltration (with the poor echo reflectivity of melanin). However, confirmation in larger pathologically proven series is required.