Institute of Fundamental Technological Research

A 30-MHz ultrasonic scanner was used to collect B-scan images together with appropriate radiofrequency echoes from diseased and healthy skin regions of patients with diagnosed basal cell carcinoma and pre-cancerous lesions (actinic keratosis). Radiofrequency data were processed to obtain the attenuation coefficient and statistics of the backscattered echo signal determination (K-distribution and effective density of scatterers [EDS]). The attenuation coefficient was significantly higher for patients with basal cell carcinoma than for healthy patients. Also, the pre-cancerous skin lesions had increased attenuation. The averaged EDS values for cancer lesions were significantly lower than those for pre-cancerous lesions and healthy skin. The successful differentiation between the tissue groups examined suggests the potential value of the attenuation coefficient and EDS for carcinoma characterization.

Quantitative ultrasound, High frequency, Human skin, Skin lesions, K-distribution, Attenuation coefficient, Tissue characterization

Aim.
The aim of our study was to assess the usefulness of high frequency ultrasonography in the diagnosis of melanoma. Methods. We examined 84 patients with suspicious melanocytic skin lesions, including 19 cases of melanoma. In vivo high-resolution ultrasonography (30 MHz) was performed prior to excision.

Results.
In ultrasound scans early melanomas presented as flat oval or fusiform shaped structures and were clearly demarcated, while advanced melanomas were characterized by a roundish shape with less distinct borders. The ultrasonographic thickness of in situ melanomas ranged from 0.02 to 0.85 mm. In the case of invasive tumors, the mean thickness evaluated by high frequency ultrasonography was 10.7% higher compared to the Breslow Score (1.44±0.8 mm and 1.3±0.88 mm, respectively). In all melanomas of Breslow Score of 1 mm or more ultrasound also indicated a Breslow Score of 1 mm or more.

Conclusion.
High frequency ultrasound examination has limited value in differential diagnosis of melanoma, but it gives a clear picture of the size and depth of the tumor. The method should be used as a complementary method (after dermoscopy and, where applicable, reflectance confocal microscopy) in preoperative evaluation of the tumor. In some cases of locally advanced melanoma, ultrasound examination may allow to reduce the number of surgical procedures and favor the decision of a one-time surgical treatment (removal of primary tumor and sentinel lymph node biopsy at the same time).

Dermoscopy - Diagnosis - Melanoma - Microscopy, confocal - Ultrasonography

The paper presents a classification of the healthy skin and the skin lesions (basal cell carcinoma) basing on a statistics of the envelope of ultrasonic echoes. The echoes envelopes distributions were modeled using Rayleigh and K-distribution. The distributions were compared with empirical data to find which of them better models the statistics of the echo-signal obtained from the human skin. The results indicated that the K-distribution provides a better fit. Also, a characteristic parameter of the K-distribution, the effective number of scatterers (M), was investigated. The values of the M parameter, obtained for the skin cancer (basal cell carcinoma), were lower as compared to those obtained for the healthy skin. The results indicate that the statistical quantitative ultrasound parameters have a potential for extracting information useful for characterization of the skin condition.

statistics, K-distribution, Rayleigh distribution, ultrasonic scattering, human dermis

Propagation of ultrasonic waves in the tissue is sensitive to the alternation of tissue composition and structure.. This paper presents the classification of healthy skin and skin lesions (basal cell carcinoma (BCC)) based on statistic parameters of the envelope of echosignal. The statistics of envelope of the ultrasonic signal was modeled using Rayleigh and non-Rayleigh (the K-distribution) statistics. Furthermore the characteristic parameter of K-distribution, the effective number of scaterrers (M) was investigated.
Comparison of the results obtained for region of the skin where the BCC was diagnosed and the regions of healthy skin has shown differences in the values of M parameter. These results indicate that this parameter has the potential for extracting information useful for characterizing skin lesions.

high frequency, ultrasound, basall cell carcinoma, ststistics

Typical diagnostic process in dermatology includes clinical assessment, dermoscopic and histopathologic examination. Microsonography was initiated in seventies and much progress in the development of high-frequency scanners occurred since that time. The aim of the study was the assessment of high frequency ultrasonography in dermatologic diagnostics. Material and methods. Examination was performed with 30 MHz ultrasound transducer with 0,1 mm resolution and 7 mm penetration. We examined patients with benign and malignant neoplasms, cicatrical alopecia and morphea. Results. Sonographically, the normal skin is composed of three layers: an epidermal entry echo, dermis and subcutaneous tissue. In healthy skin we can image small hypoechoic areas which correspond to hair folicules, vessels and sebaceous glands. Most of small skin neoplasmatic lesions were hypoechogenic and homogeneous on examination. Extensive lesions were multicomponent with normo-, hypo- and anechogenic structures. The assessment of lesion’s boarders allows sometimes to conclude the invasiveness of the lesion. Areas of skin with clinically visible atrophy showed diffuse increasing of echogenicity. In early lesions, without accomplished fibrosis, diffuse decreasing of echogenicity can be observed, that is probably caused by inflammatory infiltration. In comparison to the healthy skin, the ultrasound scan of sclerotic skin shows a wide entry echo and highly reflective, thicker dermis as a result of the collagen fibers accumulation. Conclusions. Above data suggest that ultrasonographic examination may be a valuable dermatologic diagnostic tool that completes classical dermatologic diagnostics and helps to plan the treatment.

high frequency ultrasonography, benign neoplasms, malignant neoplasms, cicatrical alopecia, morphea

The scattering of ultrasonic waves depends on the size, shape, acoustical properties and concentration of scatterers in tissue. In these study K distribution of the ultrasound backscatter envelope was used to assess the structural properties of the skin tissue. The custom-designed high frequency ultrasonic scanner was applied to obtain RF B-scans of the skin in vivo at the frequency of 20-30MHz.
The results are encouraging. The K distribution models the envelope statistics very well. The parameters of the K-distribution, namely, the effective number of scatterers may be useful for the skin characterization.

skin characterization, ultrasound, K distribution

The scattering of ultrasonic waves depends on the size, shape, acoustical properties and concentration of scatterers in the tissue. The spectrum of the ultrasonic backscatter can be used to characterize non-invasively the structural and mechanical properties of tissue. We intend to apply the custom-designed high-frequency ultrasonic scanner for the skin and cutaneous lesions characterization by evaluating their attenuating and scattering properties. In this pilot study, we have explored the possibility of extracting the human skin backscattering coefficient (BC) from the ultrasonic B-scans obtained in vivo at 20–30 MHz. The measured BC values of normal skin (dermis) agree well with the published data. We have found also that the spatial resolution of the BC determination using our scanner is sufficient (aprox. 1 mm2) to characterize small skin lesions and assess their penetration depth.

attenuation coefficient, backscattering coefficient, dermis

Basal cell carcinoma is the most common cutaneous malignancy, representing 80% of all skin cancer cases. The quantitative ultrasound can provide information potentially helpful in diagnosing. The goal of this study was to find the quantitative measure of the skin tissue backscattering properties that could be used for differentiating the changes of tissue structure induced by Basal Cell Carcinoma (BCC) and precancerous lesions - Actinic Keratosis (AK). The study presents the results concerning the statistical properties of ultrasonic echoes scattered in cancer lesions and attenuation coefficient determined from the backscatter.

tissue characterization, quantitative ultrasound,skin lesions, statistical distribution, attenuation coefficient

Quantitative ultrasounds were applied for the detection and assessment of skin lesions. 30MHz ultrasonic scanner was used to collect B-scan images together with appropriate RF echoes from the pathological and healthy skin regions of skin of patients with diagnosed Basal Cell Carcinoma and precancerous states. The RF data were processed for the attenuation coefficient and statistics assessment (K distribution and effective number of scatterers – M). For patients with BCC the attenuation coefficient was significantly higher than for the healthy skin ones. Also, precancerous skin lesions revealed increased attenuation. The averaged M parameter for cancer lesions was significantly lower than for precancerous states and healthy skin. Similar results were obtained from numerical simulations of the ultrasonic echoes scattered in skin and skin lesions.

skin cancer, K distribution, effective number of scatterers, high frequency ultrasound

While the needles biopsy is still the gold standard in skin cancer diagnosis there is a growing interest in application of the high frequency ultrasound for the skin lesions detection and their thickness assessment. The quantitative ultrasound can provide additional information, potentially helpful in diagnosis. The purpose of this study was to assess the usefulness of the attenuating and statistical properties of the backscattered ultrasounds for the skin tissues characterization. The paper presents the classification of the healthy skin and skin lesions (BCC-basal cell carcinoma and AK-actinic keratosis). For patients with BCC the attenuation coefficient was significantly higher than for the healthy ones. Also, precancerous skin lesions revealed increased attenuation. The statistical properties were different for BCC comparing to AK lesions and healthy skin.

basal cell carcinoma, actinic keratosis, attenuation coefficient, statistical properties, high frequency ultrasound

Determination of attenuating properties of the tissue from the echoes of waves emitted by the focused transducer requires to compensate the echo signal for the effects of focusing. We propose the diffraction/focusing effects correcting (FC) technique that compensates focusing-induced mean frequency
shift (MFS) of the propagating pulse. The method corrects mean frequency estimates derived from echo pulses propagating in attenuating tissue with locally varying attenuation coefficient. The FC algorithm applies the diffraction correcting coefficients obtained experimentally from the probing pulses focused in water for assessing the expected values of MFS of pulses focused in attenuating tissue. The calculations involves the pulse ‘history’ that due to overall attenuation along the traveled path downshifts the pulse spectrum resulting in variation of the focusinginduced MFS obtained in water.

attenuation estimation, difraction correction, parametric imaging