Significance: Accurate early diagnosis of malignant skin lesions is critical in providing adequate and timely treatment; unfortunately, initial clinical evaluation of similar-looking benign and malignant skin lesions can result in missed diagnosis of malignant lesions and unnecessary biopsy of benign ones.
Aim: To develop and validate a label-free and objective image-guided strategy for the clinical evaluation of suspicious pigmented skin lesions based on multispectral autofluorescence lifetime imaging (maFLIM) dermoscopy.
Approach: We tested the hypothesis that maFLIM-derived autofluorescence global features can be used in machine-learning (ML) models to discriminate malignant from benign pigmented skin lesions. Clinical widefield maFLIM dermoscopy imaging of 41 benign and 19 malignant pigmented skin lesions from 30 patients were acquired prior to tissue biopsy sampling. Three different pools of global image-level maFLIM features were extracted: multispectral intensity, time-domain biexponential, and frequency-domain phasor features. The classification potential of each feature pool to discriminate benign versus malignant pigmented skin lesions was evaluated by training quadratic discriminant analysis (QDA) classification models and applying a leave-one-patient-out cross-validation strategy.
Results: Classification performance estimates obtained after unbiased feature selection were as follows: 68% sensitivity and 80% specificity with the phasor feature pool, 84% sensitivity, and 71% specificity with the biexponential feature pool, and 84% sensitivity and 32% specificity with the intensity feature pool. Ensemble combinations of QDA models trained with phasor and biexponential features yielded sensitivity of 84% and specificity of 90%, outperforming all other models considered.
Conclusions: Simple classification ML models based on time-resolved (biexponential and phasor) autofluorescence global features extracted from maFLIM dermoscopy images have the potential to provide objective discrimination of malignant from benign pigmented lesions. ML-assisted maFLIM dermoscopy could potentially assist with the clinical evaluation of suspicious lesions and the identification of those patients benefiting the most from biopsy examination.
Melanoma is the most aggressive type of skin cancer with an estimated 106,110 new cases in the US in 2021. The 5-year survival rate of patients with early-stage melanoma is ~99%; however, ~13% of melanoma patients are diagnosed with lesions already at intermediate or advance stages, associated with a 5-year survival rate of ~66% and ~27% respectively. The current diagnosis technique involving visual inspection and biopsy often fail to visually distinguish clinically similar lesions; in particular, melanoma can be mistaken for benign lesion pigmented seborrheic keratosis (pSK). In this work, a deep learning model using Long Short-Term Memory (LSTM) networks is trained on the multispectral autofluorescence lifetime dermoscopy images collected from 41 benign lesions including solar lentigo and pSK, and 19 malignant lesions including melanoma, superficial basal cell carcinoma (BCC) and nodular BCC. The model is trained on the image pixels containing concatenated fluorescent decay signals from three emission channels. The posterior probabilities predicted for each pixel location, is used to construct probability maps of the images. Receiver Operator Characteristics (ROC) constructed on the threshold of the median value of the posterior probability map determines the effectiveness in distinguishing benign and malignant lesions. The entire dataset is split into training, validation, and test sets. The hyperparameters are tuned using the validation set while the model performance is estimated using the test set. The mean and standard deviation of the Areas Under the Curve (AUC) of the ROCs generated with 10 random test sets is 0.82 ± 0.04.
Every year more than 5.4 million new cases of skin cancer are reported in the US. Melanoma is the most lethal type with only 5% occurrence rate, but accounts for over 75% of all skin cancer deaths. Non-melanoma skin cancer, especially basal cell carcinoma (BCC) is the most commonly occurring and often curable type that affects more than 3 million people and causes about 2000 deaths in the US annually. The current diagnosis involves visual inspection, followed by biopsy of the lesions. The major drawbacks of this practice include difficulty in border detection causing incomplete treatment and, the inability to distinguish between clinically similar lesions. Melanoma is often mistaken for the benign lesion pigmented seborrheic keratosis (pSK), making it extremely important to differentiate benign and malignant lesions. In this work, a novel feature extraction algorithm based on phasors was performed on the Fluorescence Lifetime Imaging (FLIM) images of the skin to reliably distinguish between benign and malignant lesions. This approach, unlike the standard FLIM data processing method that requires time-deconvolution of the instrument response from the measured time-resolved fluorescence signal, is computationally much simpler and provides a unique set of features for classification. Subsequently, FLIM derived features were selected using a double step cross validation approach that assesses the reliability and the performance of the resultant trained classifier. Promising FLIM-based classification performance was attained for detecting benign from malignant pigmented (sensitivity: ~80%, specificity: 79%, overall accuracy: ~79%) and nonpigmented (sensitivity: ~88%, specificity: 83%, overall accuracy: ~87%) lesions.
Non melanoma skin cancer (NMSC) can be seen as a multifaceted problem, considered primarily as a public health problem whose impact on society considers the morbidity and cost aspects of the treatment. It is a social problem, affecting all those who depend exclusively on the Brazilian public health system and need to wait months to receive any type of treatment. From the economic point of view, to treat all patients diagnosed with NMSC, it is necessary a big investment. Finally, the problem is logistical, since the territorial extension of Brazil and its population distribution do not enable the adequate care in all the places, which requires reallocation of patients from small cities to reference centers. Based on these facts, PDT for small skin lesions may be one of the best solutions from an economic point of view. Being a treatment that is easy for the training of professionals and enables to be performed in an ambulatory environment, minimizing post-treatment effects, this study shows that the cost of implementing the procedure on a large scale is extremely adequate for the national public health service. Using a strategy involving companies, national bank and medical partners, equipment, medication and protocols were tested in a multicenter study. With results collected over 5 years from a national program to implement PDT for non melanoma skin cancer over the Brazilian territory, we could reach a great economic evaluation of advances concerning the use of PDT for skin cancer.
Melanoma is the most aggressive type of skin cancer with high rates of recurrence, morbidly and mortality. Current standard treatment involves surgery, chemotherapy, immunotherapy and also radiation therapy but the response is limited to early-stage tumors. Photodynamic therapy (PDT) is already established as an effective therapeutic option for cutaneous pre-malignant lesions and non-melanoma skin cancer but has shown very limited efficacy for pigmented lesions as melanoma, where the high melanin absorption limits light penetration, preventing complete treatment. Optical clearing agents (OCA) are hyperosmotic agents that work by dehydrating tissue and matching the tissue refractive index, thereby reducing scattering and improving light penetration. here, OCA was used in combination with single and dual photosensitizer-based PDT, targeting the tumor cells and vasculature to improve treatment response in both melanotic and amelanotic melanoma models in vivo. Vascular-targeted PDT was more efficient for amelanotic tumors, independent of the use of OCA and could treat the whole tumor in a single treatment session. However, for the melanotic tumors, OCA significantly improved PDT response for the both vascular-targeted and dual-agent PDT. The best result was obtained with the latter, resulting in no tumor being detected by H&E staining and S100 immunostaining. These initial pre-clinical results show the potential use of dual agent PDT enhanced by OCA for the treatment of pigmented cutaneous melanoma.
Fluorescence spectroscopy and lifetime techniques are potential methods for optical diagnosis and characterization of biological tissues with an in-situ, fast, and noninvasive interrogation. Several diseases may be diagnosed due to differences in the fluorescence spectra of targeted fluorophores, when, these spectra are similar, considering steady-state fluorescence, others may be detected by monitoring their fluorescence lifetime. Despite this complementarity, most of the current fluorescence lifetime systems are not robust and portable, and not being feasible for clinical applications. We describe the assembly of a fluorescence lifetime spectroscopy system in a suitcase, its characterization, and validation with clinical measurements of skin lesions. The assembled system is all encased and robust, maintaining its mechanical, electrical, and optical stability during transportation, and is feasible for clinical measurements. The instrument response function measured was about 300 ps, and the system is properly calibrated. At the clinical study, the system showed to be reliable, and the achieved spectroscopy results support its potential use as an auxiliary tool for skin diagnostics.
Image processing tools have been widely used in systems supporting medical diagnosis. The use of mobile devices for the diagnosis of melanoma can assist doctors and improve their diagnosis of a melanocytic lesion. This study proposes a method of image analysis for melanoma discrimination from other types of melanocytic lesions, such as regular and atypical nevi. The process is based on extracting features related with asymmetry and border irregularity. It were collected 104 images, from medical database of two years. The images were obtained with standard digital cameras without lighting and scale control. Metrics relating to the characteristics of shape, asymmetry and curvature of the contour were extracted from segmented images. Linear Discriminant Analysis was performed for dimensionality reduction and data visualization. Segmentation results showed good efficiency in the process, with approximately 88:5% accuracy. Validation results presents sensibility and specificity 85% and 70% for melanoma detection, respectively.
Cancer is responsible for about 13% of all causes of death in the world. Over 7 million people die annually of this disease. In most cases, the survival rates are greater when diagnosed in early stages. It is known that tumor lesions present a different temperature compared with the normal tissues. Some studies have been performed in an attempt to establish new diagnosis methods, targeting this temperature difference. In this study, we aim to investigate the use of a handheld thermographic camera to discriminate skin lesions. The patients presenting Basal Cell Carcinoma, Squamous Cell Carcinoma, Actinic Keratosis, Pigmented Seborrheic Keratosis, Melanoma or Intradermal Nevus lesions have been investigated at the Skin Departament of Amaral Carvalho Hospital. Patients are selected by a dermatologist, and the lesion images are recorded using an infrared camera. The images are evaluated taken into account the temperature level, and differences into lesion areas, borders, and between altered and normal skin. The present results show that thermography may be an important tool for aiding in the clinical diagnostics of superficial skin lesions.
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