Handheld optical-resolution photoacoustic microscopy

Optical-resolution photoacoustic microscopy (OR-PAM) offers label-free Collapse

Key Words

• photoacoustic handheld probe
• optical-resolution photoacoustic microscopy
• two-axis microelectromechanical system mirror
• confocal scanning
• human skin imaging

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MESH Headings

• Animals
• Capillaries/diagnostic imaging
• Ear/blood supply
• Ear/diagnostic imaging
• Humans
• Mice
• Micro-Electrical-Mechanical Systems
• Microscopy, Acoustic
• Nevus/blood supply
• Nevus/diagnostic imaging
• Photoacoustic Techniques/instrumentation
• Spectrum Analysis

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Grants

• DP1 EB016986 NIBIB NIH HHS
• R01 CA159959 NCI NIH HHS
• R01 CA186567 NCI NIH HHS

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Separating melanin from hemodynamics in nevi using multimode hyperspectral dermoscopy and spatial frequency domain spectroscopy

Changes in the pattern and distribution of both melanocytes (pigment producing) and vasculature (hemoglobin containing) are important in distinguishing melanocytic proliferations. The ability to accurately measure melanin distribution at different depths and to distinguish it from hemoglobin is clearly important when assessing pigmented lesions (benign versus malignant). We have developed a multimode hyperspectral dermoscope (SkinSpect™) able to more accurately image both melanin and hemoglobin distribution in skin. SkinSpect uses both hyperspectral and polarization-sensitive measurements. SkinSpect’s higher accuracy has been obtained by correcting for the effect of melanin absorption on hemoglobin absorption in measurements of melanocytic nevi. In vivo human skin pigmented nevi (N=20) were evaluated with the SkinSpect, and measured melanin and hemoglobin concentrations were compared with spatial frequency domain spectroscopy (SFDS) measurements. We confirm that both systems show low correlation of hemoglobin concentrations with regions containing different melanin concentrations (R=0.13 for SFDS, R=0.07 for SkinSpect).

Multi-scale classification based lesion segmentation for dermoscopic images

This paper presents a robust segmentation method based on multi-scale classification to identify the lesion boundary in dermoscopic images. Our proposed method leverages a collection of classifiers which are trained at various resolutions to categorize each pixel as "lesion" or "surrounding skin". In detection phase, trained classifiers are applied on new images. The classifier outputs are fused at pixel level to build probability maps which represent lesion saliency maps. In the next step, Otsu thresholding is applied to convert the saliency maps to binary masks, which determine the border of the lesions. We compared our proposed method with existing lesion segmentation methods proposed in the literature using two dermoscopy data sets (International Skin Imaging Collaboration and Pedro Hispano Hospital) which demonstrates the superiority of our method with Dice Coefficient of 0.91 and accuracy of 94%.

Melanoma detection by analysis of clinical images using convolutional neural network

Melanoma, most threatening type of skin cancer, is on the rise. In this paper an implementation of a deep-learning system on a computer server, equipped with graphic processing unit (GPU), is proposed for detection of melanoma lesions. Clinical (non-dermoscopic) images are used in the proposed system, which could assist a dermatologist in early diagnosis of this type of skin cancer. In the proposed system, input clinical images, which could contain illumination and noise effects, are preprocessed in order to reduce such artifacts. Afterward, the enhanced images are fed to a pre-trained convolutional neural network (CNN) which is a member of deep learning models. The CNN classifier, which is trained by large number of training samples, distinguishes between melanoma and benign cases. Experimental results show that the proposed method is superior in terms of diagnostic accuracy in comparison with the state-of-the-art methods.

Immunohistochemical expression of cyclooxygenase-2 (COX-2) in oral nevi and melanoma

BACKGROUND

Cyclooxygenase-2 (COX-2) catalyses the conversion of arachidonic acid to prostaglandin, and its overexpression has been demonstrated in different malignant tumors, including cutaneous melanoma. However, no data about the expression of this protein in oral melanocytic lesions are available to date. The aim of this study was to evaluate the immunohistochemical expression of COX-2 in oral nevi and melanomas, comparing the results with correspondent cutaneous lesions.

METHODS

COX-2 was evaluated by immunohistochemistry in 49 oral melanocytic lesions, including 36 intramucosal nevi and 13 primary oral melanomas, and in four cutaneous nevi and eight melanomas.

RESULTS

All cases of oral and cutaneous melanomas were positive for COX-2. On the other hand, all oral and cutaneous melanocytic nevi were negative.

CONCLUSION

COX-2 is highly positive in oral melanomas and negative in oral nevi and might represent a useful marker to distinguish melanocytic lesions of the oral cavity.

Nevus and melanoma paraconsistent classification

This paper presents the first studies on Nevus and Melanoma classification by using Paraconsistent Artificial Neural Network (PANN). Nevus is usually a small growth on the skin while Melanoma is a dangerous skin cancer. The proposed automated process classifies a set of medical images as Nevus and Melanoma based on a methodology grounded on PANN which is able to deal with conflicting, paracomplete and imprecise data directly without trivialization. Such methodology performed promising results considering only border features to classify the sample.

In vivo photoacoustic microscopy of human cutaneous microvasculature and a nevus

In several human volunteers, photoacoustic microscopy (PAM) has been utilized for noninvasive cutaneous imaging of the skin microvasculature and a melanocytic nevus. Microvascular networks in both acral and nonacral skin were imaged, and multiple features within the skin have been identified, including the stratum corneum, epidermal-dermal junction, and subpapillary vascular plexus. Several vascular and structural differences between acral and nonacral skin were also observed in the photoacoustic images. In addition, a nevus was photoacoustically imaged, excised, and histologically analyzed. The photoacoustic images allowed for in vivo measurement of tumor thickness, depth, and microvasculature-values confirmed by histologic examination. The presented images demonstrate the potential of PAM to aid in the study and evaluation of cutaneous microcirculation and analysis of pigmented lesions. Through its ability to three-dimensionally image the structure and function of the microvasculature and pigmented lesions, PAM can have a clinical impact in diagnosis and assessment of systemic diseases that affect the microvasculature such as diabetes and cardiovascular disease, cutaneous malignancies such as melanoma, and potentially other skin disorders.

The Use of Ultrasound Biomicroscopy in the Evaluation of Anterior Segment Tumors and Simulating Conditions

PURPOSE

To report the ultrasound biomicroscopy (UBM) findings of anterior segment tumors and simulating conditions.

METHODS

Thirty-five patients underwent UBM. Of those, 16 had histopathologically or cytopathologically diagnosed tumors, and 19 had clinically diagnosed lesions.

RESULTS

The study material comprised 13 iris pigment epithelial (IPE) cysts, 7 ciliary body melanomas, 4 iris melanomas, 4 iris nevi, 3 intraocular invasions of conjunctival squamous cell carcinoma, 2 ring melanomas of the anterior chamber angle, 1 medulloepithelioma and 1 pars plana cyst. On UBM, all IPE cysts presented as cystic lesions with a thin cyst wall and no solid components. All ciliary body melanomas showed low to medium reflectivity, with cavitation in one case and extraocular extension in another. Iris melanomas presented as anterior (stromal) iris lesions with medium to high internal reflectivity. There was irregularity and convex bowing of the posterior iris plane in iris melanomas, a feature not seen in iris nevi. Intraocular invasion of conjunctival squamous cell carcinoma was evidenced as areas of medium to high reflectivity in the ciliary body and iris, loss of the acute angle shape and highly reflective spots in the anterior chamber.

CONCLUSIONS

UBM was particularly useful in the diagnosis of IPE cysts, in the visualization of small ciliary body melanomas, in the differentiation of iris melanomas from iris nevi and in the demonstration of intraocular invasion from conjunctival squamous cell carcinoma.

Preoperative Ultrasonic Assessment of Thin Melanocytic Skin Lesions Using a 100-MHz Ultrasound Transducer: A Comparative Study

BACKGROUND

It has been shown that tumor thickness (TT) of melanocytic skin lesions (MSL) of less than 1 mm vertical thickness assessed by 20 MHz are often incorrectly evaluated.

OBJECTIVE

We aimed to evaluate the accuracy of 100-MHz ultrasound for the determination of TT of thin MSL, compared with conventional 20-MHz ultrasound and histologic findings.

METHODS

Thirty-seven patients with 50 suspicious MSL, including tumor diameter up to 1 cm and maximum vertical TT of less than 1 mm, were recruited. The agreement between the histologically and ultrasographically measured TT was analyzed using Bland and Altman plots.

RESULTS

Compared to histology, 20-MHz ultrasound (33.9 microm) as well as 100-MHz (16 microm) resulted in overestimation of TT that was twofold higher for 20-MHz ultrasound. The latter also revealed wider 95% limits of agreement (4.9 to 63 microm) than 100-MHz ultrasound (3.5 to 28.7 microm).

CONCLUSION

Analysis of agreement clearly demonstrated that the performance of 100-MHz ultrasound is superior to conventional 20-MHz ultrasound, even though a relatively small positive bias was observed in 100-MHz ultrasound, indicating a systematic error. We consider 100-MHz ultrasound a useful tool for the noninvasive determination of TT of thin MSL in vivo.

Quantitative discrimination of pigmented lesions using three-dimensional high-resolution ultrasound reflex transmission imaging

High-resolution ultrasound-reflex transmission imaging is a non-invasive method that can be performed in vivo. We have adapted and refined this technique for skin imaging. Scans can be analyzed to produce objective parameters. Previous work has highlighted sonographic differences between benign and malignant lesions. The aim of this study was to produce and test numerical parameters from ultrasound skin images that would quantify the acoustic differences between common pigmented lesions, which may aid their discrimination from melanoma. We report our findings for randomly selected patients referred from primary care with suspected melanoma. Those subsequently classified as malignant melanoma (MM), seborrheic keratosis (SK), and benign nevi by a consultant dermatologist (n=87) were imaged by high-resolution ultrasound-reflex transmission imaging. Using surrounding normal skin as a control, numerical sonographic parameters were derived for each lesion giving a relative measure of surface sound reflectance, intra-lesional sound reflection, total sound attenuation, and the relative uniformity of each parameter across the tumor. Significant quantitative differences existed between benign and malignant pigmented lesions studied. Sufficient discrimination was produced between MM (n=25), SKs (n=24) and other benign-pigmented lesions (n=38) to potentially reduce the referral of benign tumors by 65% without missing melanoma.

Long term ultrasonic follow up of choroidal naevi and their transformation to melanomas

AIMS

To compare ultrasonographic (US) predicting factors for conversion of choroidal naevi into melanomas.

METHODS

659 consecutive eyes with choroidal naevi were examined between 1984 and 2004. 165 clinically suspicious naevi were followed clinically and ultrasonographically (thickness, base diameters, internal reflectivity and location in the eye) for 5.08 (SE 0.24) years.

RESULTS

17 naevi (2.6% of all naevi, 10.3% of suspicious naevi) converted to small choroidal melanomas. The thickness of benign and premalignant naevi differed significant only after 1.5 years of follow up. The mean initial thickness of benign and premalignant naevi was significantly different (p = 0.001), as was mean initial internal reflectivity (p = 0.002) and mean initial largest base diameter (LBD, p = 0.05). Posterior pole and nasally located naevi were more likely to become malignant. A thickness of > or = 2 mm and a LBD > or = 7 mm were most predictive of conversion to melanoma, as was a combined K(I) index of > or = 14.5 (KI = LBD + 4 x thickness + 1 (for nasal location) + 1 (for posterior pole location)). An artificial neural network did not have a better forecasting accuracy than the KI index. Logistic regression found the only significant parameters to influence the risk of conversion to melanoma to be the KI value and the initial tumour thickness.

CONCLUSIONS

A follow up of at least 1.5 years is necessary to detect conversion of naevi to choroidal melanomas. The thickness and LBD of the lesion can be used for predicting the risk.

Real-time spatial compound ultrasound imaging of skin

PURPOSE

The aim of our study was to evaluate the potential of real-time spatial compound imaging (RTSCI) in dermatology.

MATERIALS AND METHODS

An ATL 5000 SonoCT equipped with compact linear 15-7 MHz and linear 12-5 MHz transducers was obtained for skin visualization in a group of dermatological patients with various skin diseases.

RESULTS

Thirty-four people participated: 21 patients with various skin diseases and 13 persons with normal skin. The mean age was 43.4 years. For many diseases, RTSCI gave useful information about the lesional structure, thickness and relationship with surrounding structures.

CONCLUSION

RTSCI allows objective, accurate, noninvasive and easy measurements of several parameters of skin morphology. It is useful in clinical trials, for evaluation of the effects of therapy, for preoperative evaluation of dermatological lesions, and enables visualization of subclinical and deep lesions, giving physicians the possibility of starting treatment before disease intensity increases. However, even such highly advanced ultrasound cannot completely substitute the clinical dermatological approach and the occasional need for histological diagnosis. This new method may, however, become an important adjunct method for the study of skin lesions.

Needle-guided shave excision with ultrasonographic assistance: a new technique

BACKGROUND

A lack of control in the deep margin of shave excision is a drawback of this technique.

OBJECTIVE

To describe a more precise shaving technique by sonography with the use of a fine injector needle as a depth marker.

METHODS

After having examined the invasion levels of 40 benign skin lesions, a fine injector needle was intentionally threaded into the dermis horizontally just beneath the required shaving plane. Correct placement of the needle was ensured by sonographic examination after possible reinsertion trials. Large lesions needed several needles to be inserted. The tissue above the needles was then shaved off, whereas the deep dermal layer was protected.

RESULTS

Histologic examination revealed that 77% of superficial and intermediate-thickness lesions were removed totally without disturbing the derma-fat junction.

CONCLUSION

The needle-guided technique was found to be effective in the control of the deep margin of shave excision.

Linear sebaceous naevus syndrome and resistant rickets

The association between vitamin-D-resistant rickets and linear sebaceous naevus syndrome is extremely rare. Only eight cases have been described in the English literature and in none were the skeletal aspects addressed. We present three new cases and describe the musculoskeletal features. The details and outcome of surgery for correction of the deformities are discussed. The disturbances of metabolism of vitamin D and the effects of pharmacological treatment are also described.

Efficacy of (123)N-isopropyl-p-[(123)I]-iodoamphetamine single photon emission computed tomography for the diagnosis of uveal malignant melanoma

PURPOSE

To evaluate the efficacy of single photon emission computed tomography (SPECT) images with N-isopropyl-p-[(123)I]-iodoamphetamine ([(123)I]-IMP) as a radiopharmaceutical for the diagnosis of uveal melanoma.

METHODS

Consecutive interventional case series. Single photon emission computed tomography images were obtained after intravenous injection of [(123)I]-IMP in 20 patients with clinically suspected uveal melanoma (16 eyes of 16 patients) or ocular adnexal melanoma (four adnexal tumors of four patients). Histologic findings in seven eyes enucleated for uveal melanoma were analyzed with the SPECT images semiquantitatively evaluated.

RESULTS

Eight of 20 eyes with suspected uveal melanoma showed high accumulation of [(123)I]-IMP in the late phase in the area corresponding to the uveal tumor, and the diagnosis of uveal melanoma was confirmed histologically in seven enucleated eyes. Tumor size and histologic features did not reflect the intensity of scintillation counts of [(123)I]-IMP. Twelve patients with no accumulation on the SPECT images were found to have clinically or histologically iris nevus, choroidal nevus, and other intraocular and adnexal conditions.

CONCLUSION

N-isopropyl p-[(123)I]-iodoamphetamine SPECT may serve as a sensitive and specific examination for the diagnosis of uveal melanoma.

Classification of reflectance spectra from pigmented skin lesions, a comparison of multivariate discriminant analysis and artificial neural networks

Successful treatment of skin cancer, especially melanoma, depends on early detection, but diagnostic accuracy, even by experts, can be as low as 56% so there is an urgent need for a simple, accurate, non-invasive diagnostic tool. In this paper we have compared the performance of an artificial neural network (ANN) and multivariate discriminant analysis (MDA) for the classification of optical reflectance spectra (320 to 1100 nm) from malignant melanoma and benign naevi. The ANN was significantly better than MDA, especially when a larger data set was used, where the classification accuracy was 86.7% for ANN and 72.0% for MDA (p < 0.001). ANN was better at learning new cases than MDA for this particular classification task. This study has confirmed that the convenience of ANNs could lead to the medical community and patients benefiting from the improved diagnostic performance which can be achieved by objective measurement of pigmented skin lesions using spectrophotometry.

Evaluation of ocular tumors with technetium-99m-MIBI: planar pinhole technique or SPECT?

OBJECTIVE

This study compares 2 imaging protocols, planar pinhole technique (PPHT) and SPECT, for evaluating ocular masses with 99mTc-MIBI.

METHODS

Sixteen patients with ocular lesions were studied. Planar images were acquired 10 min after the injection of 740 MBq 99mTc-MIBI with an LFOV camera fitted with a pinhole collimator (5.0 mm). A SPECT study was performed immediately after the planar study, using a 360 degrees orbit, 64 steps, 20 s/stop, a 128 x 128 matrix, and a low-energy high-resolution (LEHR) collimator. Twelve lesions (9.5-18.0 mm) proved to be malignant: 8 primary tumors (ocular melanoma); 3 local relapses of different tumors of the conjunctiva; and 1 ocular metastasis from breast cancer. The remaining 4 lesions (10.0-16.0 mm) were benign: 1 inflammatory lesion; 1 benign intraocular calcification; and 2 naevi.

RESULTS

SPECT images showed 11 of 12 malignant lesions (91.6%), whereas the planar technique demonstrated only 4 of the 12 lesions (33.3%). One false-positive result, the inflammatory lesion, was visualized by both techniques. The remaining benign lesions were not detected with either method.

CONCLUSION

Technetium-99m-MIBI SPECT is a sensitive technique for detecting malignant ocular tumors. SPECT imaging is a better alternative to planar imaging for ocular tumors.

Ultrasound biomicroscopy. High-frequency ultrasound imaging of the eye at microscopic resolution

UBM presents us with a new method of imaging the anterior segment of the eye at high resolution. Its strengths lie in its ability to produce cross-sections of the living eye at microscopic resolution without violating the integrity of the globe. UBM, although lacking the resolution of optical microscopy, gives us images in living eyes without affecting the internal relationships of the structures imaged. There are many other applications of this new imaging method. Examples of other uses include imaging adnexal pathology, assessing corneal changes with refractive surgery, the assessment of trauma, and determination of intraocular lens position.

Skeletal involvement and follow-up in linear nevus sebaceous syndrome

Linear nevus sebaceous syndrome is a rare neurocutaneous syndrome in which associated radiographic findings of the peripheral skeletal system are uncommon. We report a follow-up study of a patient with mainly unilateral changes of the skeletal system involving the thorax and the right arm and leg.

[The primary study of ultrasound biomicroscope in imaging anterior segment tumors of eye]

PURPOSE

To evaluate the use of ultrasound biomicroscope (UBM) in imaging anterior segment tumors of eye.

METHODS

13 cases of anterior segment tumors of eye were examined with UBM.

RESULTS

3 cases had the ocular history of trauma or surgery and were clinically diagnosed as anterior iris cysts. UBM displayed the cysts as thin-walled, no internal reflectivity, and at the locate of anterior humour angle; 8 cases had superficial anterior humour, narrow anterior angle and clinically be suspected as tumors behind iris or ciliary body. UBM showed cystic reflectivity in 7 cases and a solid tumor in ciliary body in one case. 2 cases were clinically diagnosed as iris nevi. UBM displayed solid convex lesions.

CONCLUSION

UBM is a valuable new technique in the diagnosis and accurate localization of anterior segment tumors.

Value of high-frequency US for preoperative assessment of skin tumors

The purpose of this study was to evaluate the accuracy of high-frequency ultrasound (US) in the preoperative assessment of skin tumors. A US scanner with a 20-MHz probe was used to visualize and evaluate 70 skin lesions (38 clinically suspected melanomas and 32 suspected basilar cell carcinomas [BCCs]) before surgical resection. A US morphologic study and a Doppler analysis of vascularity were performed for each tumor. Of the 70 tumors, 62 were clearly visualized, including 19 melanomas, 12 nonmalignant nevi, and 31 BCCs. Most lesions were hypoechoic. In 13 of 19 proved melanomas, the difference between the histologic and US measurements was equal to or less than 0.2 mm. Vessels were visualized in melanomas with thicknesses greater than 3 mm. All BCCs were visualized, and in 29% of cases of BCC, tumor size at US was greater than that at clinical examination. High-frequency, high-resolution US is a simple, reliable, noninvasive method for accurate preoperative assessment of skin tumor dimensions. This technique allows surgical planning to be adapted and reexcision to be avoided. However, its role is limited in the differential diagnosis of malignant and benign skin lesions.

Visualizing ocular melanoma using iodine-123-N-(2-diethylaminoethyl)4-iodobenzamide SPECT

Radiolabeled benzamides have recently been introduced for the detection of melanoma. We evaluated the potential clinical applicability of 123I-N-(2-diethylaminoethyl) 4-iodobenzamide ([123I]IDAB) for SPECT imaging of ocular melanoma.

METHODS

Fourteen patients were studied, 10 with or suspected of malignant ocular melanoma and four with ocular naevi. All patients underwent SPECT imaging of the head and whole-body scintigraphy 4-5 hr after injection of 170 MBq [123I]IDAB.

RESULTS

A definite tracer hyperfixation was observed in the pathological eye in 9 of 10 (90%) patients with ocular melanoma. The pathological-to-normal eye ratio averaged 1.46 (range 1.07-2.86). The melanoma nature of the scintigraphic lesions was confirmed after enucleation in eight cases and by clinical evolution in two. A false-negative scan was reported in a patient with a small and hypochromic lesion. In patients with ocular naevi, no false-positive scintigrams were documented.

CONCLUSION

Iodine-123-IDAB scintigraphy may contribute significantly to decide about enucleation in cases where some doubt persists with conventional techniques.

[Objectivity, reproducibility and validity of 3D ultrasound in dermatology]

Recently it has become possible to visualize the three-dimensional (3D) architecture of sonographic structures using high-resolution ultrasound above 20 MHz (Dermascan C, Denmark; DUB 20, Germany). We studied the objectivity, reproducibility, and validity of these two 3D analysis systems on 22 skin tumors. To validate both systems, we compared the sonometric and histometric volume in 4 tumors. The objectivity was calculated by repeated evaluation of the volume on the same serial B-scan sections at 3-month intervals. The two-dimensional B-scans and 3D images exhibited similar characteristics. Volumetric evaluations were reproducible with both systems (variation coefficient < or = 9.9%), when the applicator was oriented longitudinal to the body axis. By changing the orientation, the coefficient increased up to 58.1% (DUB 20). Sonometric and histometric volumes of a phantom model and of the tumors exhibited small deviations in the Dermascan C (< or = 8.1%) and in some tumors large deviations in the DUB 20 (< or = 93.1%). We can conclude that the 3D sonography is a reproducible method, which can be used to evaluate the volume of skin tumors and metastases under chemotherapy or radiotherapy. We suggest in particular to use the in-vivo tumor volume as a prognostic parameter for the malignant melanoma.

Does high-frequency (40-60 MHz) ultrasound imaging play a role in the clinical management of cutaneous melanoma?

The assessment of cutaneous melanoma in the clinical setting is often difficult, and important features such as depth and width remain unknown until the pathology report is received. Access to prognostic features such as vertical height before excisional biopsy would offer a basis for guidance in defining surgical margins and early planning of treatment options. Recently developed high-frequency ultrasound imaging in the 40-to 60-MHz range is a noninvasive method that provides in vivo information about cutaneous lesions. Imaging at these frequencies provides high-resolution data within the range of the epidermis and dermis (3-4 mm in depth). Ten cutaneous melanomas and seven pigmented lesions were assessed in this fashion. Vertical height was documented and compared to histopathological findings. High-frequency ultrasound imaging determination of vertical height correlated well with the standard measurement of Breslow's thickness on histological sections only in midrange (1.0-3.0 mm) lesions. Inflammatory cells at the base of three melanomas provoked an overestimation of the depth measurement with ultrasonography. Thick keratin layers such as those found on the feet acted as a virtual block to the high-frequency scanner. The application of this new advance in noninvasive imaging technology to the clinical assessment of cutaneous melanoma provides interesting in vivo data but in its present state does not replace the need for the biopsy of pigmented lesions and histopathological diagnosis.