Key Points to Select a Device for Dermatologic Ultrasound

Advanced US of the Skin, Nerves, and Muscles of the Neck: Pearls and Pitfalls with Use of High-Frequency Transducers

High-frequency US provides excellent visualization of superficial structures and lesions, is a preferred diagnostic modality for anatomic characterization of neck abnormalities, and has a central role in clinical decision making. Recent technological advancements have led to the development of transducers that surpass 20 MHz, elevating high-frequency US to a highly valuable diagnostic tool with broader clinical use and enabling greater spatial resolution in the assessment of skin and superficial nerves and muscles. The authors focus on evolving applications of high-frequency US in neck imaging, emphasizing practical insights and strategies in skin and neuromuscular applications. ©RSNA, 2024 Supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Ultrasound in Skin Cancer: Why, How, and When to Use It?

BACKGROUND

Skin cancer is the most common cancer in human beings. Ultrasound is a powerful and non-invasive imaging technique that has expanded its use in dermatology, including in the skin cancer field. The full range of critical anatomical information provided by ultrasound cannot be deduced from a naked eye examination, palpation, or other imaging techniques such as dermoscopy, confocal microscopy, magnetic resonance imaging, or PET-CT (Positron Emission Tomography-Computed Tomography).

METHODS

This review practically analyzes the main ultrasonographic features of the most common types of skin cancers and the performance of the locoregional staging according to the literature, which is illustrated by state-of-the-art clinical and ultrasonographic correlations.

RESULTS

The most common types of skin cancer show recognizable ultrasonographic patterns.

CONCLUSIONS

Among the current radiological imaging techniques, ultrasound has the highest axial spatial resolution. Compared to other imaging techniques used in dermatology, it shows the great advantage of penetrating the soft tissues thoroughly, which allows us to detect and identify the most common skin types of skin cancer, including both the primary tumor and its locoregional metastases.

Ultrasonographic features of nonvascular complications of hyaluronic acid fillers: a retrospective study at a reference center for dermatologic ultrasonography

Hyaluronic acid filler injections have been associated with early, temporary, and delayed-onset complications. High-resolution ultrasound with Doppler analysis has been increasingly used to detect and identify such complications. We comprehensively describe the most common ultrasonographic findings of nonvascular complications associated with hyaluronic acid filler injections. This retrospective, cross-sectional, observational study was conducted at a reference center for dermatologic ultrasound in Bogotá, Colombia. Ultrasound reports documented the ultrasonographic findings of nonvascular complications of hyaluronic acid filler injections. Fifty-two complications were documented in a cohort of 50 patients (women, 88%). The infraorbital region was the most common site affected (23%), followed by the nasolabial region (22%). The Tyndall effect was the most common complication (25% of all), followed by changes in rheology (21%) and pseudosarcoidal (foreign body granuloma) reaction (15%). The Tyndall effect stood out for its distinctive ultrasonographic characteristics. We discuss the ultrasonographic findings and pathogenesis of other complications, including filler migration, early hypersensitivity, aseptic abscess, overcorrection, and filler material interaction. The clinical presentation of hyaluronic acid filler complications can be confusing, delaying timely diagnosis and treatment. High-resolution ultrasound with Doppler analysis is a valuable tool for avoiding unnecessary treatments and ensuring timely diagnosis and treatment.

Role of high-frequency ultrasound in differentiating benign and malignant skin lesions: potential and limitations

PURPOSE

This study examined the diagnostic value of high-frequency ultrasound (HFUS) features in differentiating between benign and malignant skin lesions.

METHODS

A total of 1,392 patients with 1,422 skin lesions who underwent HFUS examinations were included in an initial dataset (cohort 1) to identify features indicative of malignancy. Qualitative clinical and HFUS characteristics were recorded for all lesions. To determine which HFUS and clinical features were suggestive of malignancy, univariable and multivariable logistic regression analyses were employed. The diagnostic performance of HFUS features combined with clinical information was evaluated. This assessment was validated using internal data (cohort 2) and multicenter external data (cohort 3).

RESULTS

Features significantly associated with malignancy included age above 60 years; lesion location in the head, face, and neck or genital regions; changes in macroscopic appearance; crawling or irregular growth pattern; convex or irregular base; punctate hyperechogenicity; blood flow signals; and feeding arteries. The area under the receiver operating characteristic curve, sensitivity, and specificity of HFUS features combined with clinical information were 0.946, 92.5%, and 86.9% in cohort 1; 0.870, 93.1%, and 80.8% in cohort 2 (610 lesions); and 0.864, 86.2%, and 86.6% in cohort 3 (170 lesions), respectively. However, HFUS is not suitable for evaluating lesions less than 0.1 mm in thickness or lesions exhibiting surface hyperkeratosis.

CONCLUSION

In a clinical setting, the integration of HFUS with clinical information exhibited good diagnostic performance in differentiating malignant and benign skin lesions. However, its utility was limited in evaluating extremely thin lesions and those exhibiting hyperkeratosis.

High-Resolution Ultrasound for Complications of Botulinum Toxin Use: A Case Series and Literature Review

Botulinum toxin (BTX) has revolutionized both aesthetic and therapeutic medicine by selectively inhibiting acetylcholine release at the neuromuscular junction, inducing localized muscle relaxation. However, its use can be associated with various complications. As a diagnostic modality, high-resolution ultrasound can better characterize these complications. Here, we present four clinical cases of complications associated with the application of BTX, along with their corresponding ultrasonographic findings. In this study, cases were selected randomly, irrespective of the timing of BTX injections, to illustrate a spectrum of complications observed in clinical practice. Despite its benefits, BTX can have adverse effects ranging from mild to severe, including aesthetic and functional complications, such as hematoma, ptosis, facial asymmetry, nodules, or pseudoaneurysm. High-resolution ultrasound emerges as a crucial tool in the multidisciplinary management of these complications, allowing for accurate evaluation and effective therapeutic guidance.

Integrating vascularity into the pattern classification of pilomatricomas on ultrasound provides a more competent approach for discriminative evaluation

BACKGROUND

Pilomatricoma has various manifestations on color Doppler ultrasound, and a differential diagnosis is challenging. The objective of this study was to investigate which characteristics of skin lesions on color Doppler ultrasound are effective in distinguishing pilomatricoma from epidermoid cyst and dermatofibrosarcoma protuberans.

MATERIALS AND METHODS

Records of patients with pilomatricomas (n = 63), epidermoid cysts (n = 76), and dermatofibrosarcoma protuberans (n = 19) who underwent color Doppler ultrasound evaluation and surgical excision were reviewed. The anatomical distribution and color Doppler ultrasound characteristics of these lesions were analyzed. The 63 pilomatricomas were categorized into five types based on their color Doppler ultrasound characteristics, and the roles of these five types in the differential diagnosis of the aforementioned diseases were studied.

RESULTS

Pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans exhibited some similar characteristics. Dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity were the major characteristics of pilomatricomas. The pilomatricomas could be categorized into five types, with type II having a diagnostic performance of sensitivity of 65.08%, specificity of 98.95%, area under the receiver operating characteristic curve (AUC) of 0.743, positive predictive value of 97.62%, and negative predictive value of 81.03% for the diagnosis of the aforementioned skin diseases.

CONCLUSION

A combination of dominantly markedly hyperechoic or hyperechoic appearance, posterior acoustic shadowing, and the presence of vascularity exhibits higher diagnostic performance for the differential diagnosis of pilomatricomas, epidermoid cysts, and dermatofibrosarcoma protuberans.

Ultrasound Pattern of Cutis Verticis Gyrata

Cutis verticis gyrata (CVG) is a cutaneous benign condition that usually presents symmetric or asymmetric convoluted folds and deep furrows in the scalp, which mimic the disposition of the cerebral sulci and gyri. This scalp deformation may be a worrying situation for the patients and their families. Clinically, its diagnosis may be challenging because it can mimic other cutaneous conditions. So far, the ultrasonographic pattern of CVG has not been reported. Thus, we aim to review the ultrasound findings of this entity. All patients (n = 14) presented zones with dermal and hypodermal thickening that corresponded with the elevated clinical zones, followed by folds with normal cutaneous thicknesses. There was undulation of the cutaneous layers in all cases. The scalp areas involved the frontal, parietal, and occipital regions bilaterally. The mean maximum dermal and hypodermal thicknesses and echogenicities and the color Doppler characteristics are provided. No significant dilation of the hair follicles was detected. In conclusion, CVG presents an ultrasonographic pattern that can support its diagnosis and follow-up. This can help its differential diagnosis with other scalp dermatologic conditions.

Ultrasound Morphea Activity Scoring (US-MAS): Modified US-MAS

Morphea, an autoimmune connective tissue disease that affects the skin, can be supported by color Doppler ultrasound in its diagnosis and assessment of activity. To date, there are no reliable laboratory parameters to track activity, and ultrasound presents a higher axial spatial resolution than magnetic resonance imaging and computed tomography, which is critical for studying the superficial layers. The quality of the ultrasonographic assessment of activity in morphea depends on the standardization and features of the acquisition of the anatomical data. We propose a detailed ultrasound morphea activity scoring called modified US-MAS (mUS-MAS) that could allow us to systematically register the cutaneous abnormalities in the corporal regions and their subregions. The selection of the scanning sites will depend on the corporal regions of involvement and their adjacent segments. Through systematic and sequential ultrasound data analysis, we propose that this scoring system can better support description and activity tracking accuracy.

Ultrasound Assessment of Skin Tumors Local Recurrence

Skin cancer may recur at or around the surgical site despite wide excisions. Prompt clinical and sonographic detection of local recurrence is important since subjects with relapsing melanomas or nonmelanoma malignancies can be managed efficaciously, with a relevant impact on morbidity and survival. Ultrasound is being employed with increasing frequency in the assessment of skin tumors, but most of the published articles relate to initial pretherapeutic diagnosis and staging. This review aims to offer an illustrated guide to the sonographic evaluation of locally recurring skin cancer. We introduce the topic, then we provide some sonographic tips for patient follow-up, then we describe the ultrasound findings in case of local recurrence, illustrating the main mimickers, and finally, we mention the role of ultrasound in guiding diagnostic and therapeutic percutaneous procedures.

Ultrasonographic Patterns of Calcium Hydroxyapatite According to Dilution and Mix With Hyaluronic Acid

OBJECTIVES

To assess the ultrasonographic patterns of different calcium hydroxyapatite (CaHA) formulations, including the undiluted, diluted, and mixed with hyaluronic acid (HA) compounds.

METHODS

To review the ultrasonographic images of patients ≥18 years with confirmed injections of CaHA clinically and ultrasonographically, and without different concomitant types of fillers in the same region or other systemic or localized cutaneous diseases.

RESULTS

Twenty-one patients met the criteria (90% female; 10% male; mean age: 52 years ± 12.8). Of these, 33.3% have been injected with an undiluted formulation, 33.3% with diluted, and 33.3% with a mixed formulation. All cases were studied with devices presenting frequencies that ranged from 18 to 24 MHz. Twelve cases (57%) were also studied with the 70 MHz. The ultrasonographic patterns of CaHA presented differences in the presence and intensity of PAS and the degree of inflammation according to the dilution and mix with HA. Diluted formulations show a milder intensity posterior acoustic shadowing (PAS) artifact than undiluted at 18-24 MHz. In mixed formulations, 57% showed mild PAS, and 43% demonstrated no PAS artifact at 18-24 MHz, besides fewer inflammatory changes in the periphery of the deposits.

CONCLUSIONS

The ultrasonographic patterns of CaHA show differences in the presence and intensity of PAS and the degree of inflammation according to the dilution and mix with HA. Awareness of these ultrasonographic variations can support better discrimination of CaHA.

The Role of Ultra-High-Frequency Ultrasound in Pyoderma Gangrenosum: New Insights in Pathophysiology and Diagnosis

Pyoderma gangrenosum (PG) is a neutrophilic dermatological disease, whose pathogenesis is still poorly clarified. Because of the lack of validated criteria for diagnosis and response, PG treatment is still challenging and should be differentiated in the inflammatory and non-inflammatory phases. Our study aimed to provide a new semi-quantitative approach for PG diagnosis and monitoring, identifying ultra-high-frequency ultrasound (UHFUS) early biomarkers associated with the transition between the two phases. We enrolled 13 patients affected by painful PG lesions evaluated during the inflammatory phase (T0) and during the non-inflammatory phase (T1): pain was measured by the Visual Analogue Scale (VAS); clinical features were recorded through digital photography; epidermis and dermis ultrasound (US) characteristics were evaluated by UHFUS examination with a 70 MHz probe (Vevo MD® FUJIFILM VisualSonics). In T1 UHFUS examination, the presence of hyperechoic oval structures was lower compared to T0 (p value < 0.05). An hyperechogenic structure within the oval structure, suggestive of a hair tract, was evident in T0 and absent in T1 (p value < 0.05). In T0, blood vessels appear as U-shaped and V-shaped anechoic structures with a predominance of U-shaped vessels (p value < 0.05) compared to the more regular distribution found in T1. Finding early biomarkers of the transition from the inflammatory to the non-inflammatory phase could provide new insight in terms of therapeutic decision making and response monitoring. The differences found by this study suggest a potential use of UHFUS for the development of an objective standardized staging method. Further investigations will be necessary to confirm our preliminary results, thus providing a turning point in PG early detection, differential diagnosis and treatment monitoring.

Deep Learning-Based Evaluation of Ultrasound Images for Benign Skin Tumors

In this study, a combined convolutional neural network for the diagnosis of three benign skin tumors was designed, and its effectiveness was verified through quantitative and statistical analysis. To this end, 698 sonographic images were taken and diagnosed at the Department of Dermatology at Severance Hospital in Seoul, Korea, between 10 November 2017 and 17 January 2020. Through an empirical process, a convolutional neural network combining two structures, which consist of a residual structure and an attention-gated structure, was designed. Five-fold cross-validation was applied, and the train set for each fold was augmented by the Fast AutoAugment technique. As a result of training, for three benign skin tumors, an average accuracy of 95.87%, an average sensitivity of 90.10%, and an average specificity of 96.23% were derived. Also, through statistical analysis using a class activation map and physicians' findings, it was found that the judgment criteria of physicians and the trained combined convolutional neural network were similar. This study suggests that the model designed and trained in this study can be a diagnostic aid to assist physicians and enable more efficient and accurate diagnoses.

Ultrasound imaging of the axilla

Axilla is a pyramidal-in-shape "virtual cavity" housing multiple anatomical structures and connecting the upper limb with the trunk. To the best of our knowledge, in the pertinent literature, a detailed sonographic protocol to comprehensively assess the axillary region in daily practice is lacking. In this sense, the authors have briefly described the anatomical architecture of the axilla-also using cadaveric specimens-to propose a layer-by-layer sonographic approach to this challenging district. The most common sonographic pathological findings-for each and every anatomical compartment of the axilla-have been accurately reported and compared with the corresponding histopathological features. This ultrasound approach could be considered a ready-to-use educational guidance for the assessment of the axillary region. CRITICAL RELEVANCE STATEMENT: Axilla is a pyramidal-in-shape "virtual cavity" housing multiple anatomical structures and connecting the upper limb with the trunk. The aim of this review article was to describe the anatomical architecture of the axilla, also using cadaveric specimens, in order to propose a layer-by-layer sonographic approach to this challenging district.

[Ultrasound of the neck]

Ultrasound examination of the neck organs enables an assessment that in many cases is superior to that of magnetic resonance imaging and computed tomography. Ultrasound is therefore not only a first line or point of care imaging modality but can provide imaging for the concluding diagnosis in cases. Because of the good sonographic accessibility of the majority of the structures of the neck, many technical advances, in particular high-resolution ultrasound and signal post-processing have a major influence on the possibilities of ultrasound. Lymph nodes and salivary glands are the main focus in clinical applications, although other diseases and swellings of the neck can also be clarified with ultrasound. Special applications are ultrasound-guided interventions, e.g., biopsies or the sonographic assessment of peripheral nerves. As in any imaging modality, a comprehensive clinical knowledge is necessary for the diagnostic assessment. Because of constant assessment and thus continuous modification of the examination, ultrasound examinations may only be performed adequately with the appropriate clinical knowledge.

High-frequency ultrasound assessment of vulvar lichen sclerosus treated with photodynamic therapy

BACKGROUND

Patients with vulvar lichen sclerosus (VLS) are faced with a decreased quality of life and an increased risk of vulvar malignancy. 5-Aminolevulinic acid-based photodynamic therapy (ALA-PDT) can serve as an alternative for refractory VLS patients. However, high-frequency ultrasound (HFUS) has never been introduced in the ALA-PDT outcome assessment for VLS patients.

METHODS

A prospective study was conducted. Refractory VLS patients received two treatment courses of ALA-PDT (3 times of remedies at 2-week intervals for each course), and underwent clinical, HFUS and histopathological assessment. Statistical analysis comparing parameters at baseline and after ALA-PDT was performed.

RESULTS

Thirty-one VLS patients were included. Both subjective symptoms (itch and burning pain) and objective severity (lesion size and hypopigmentation) were relieved significantly after ALA-PDT treatment. Hypoechoic dermal band (HDB) thickness revealed by HFUS decreased progressively with successive ALA-PDT treatment, and the reduction value had a positive correlation with the reduction of inflammatory infiltration depth in histopathology. Collagen homogenization depth decrease was also noticed. Besides, adverse effects were recorded, mainly as mild and transient post-treatment edema and pain.

CONCLUSIONS

ALA-PDT is an effective and safe therapeutic option for refractory VLS patients. HFUS can act as a complement to the non-invasive treatment monitoring for its objectivity, quantifiability and precision in the distinct vertical perspective.