Skin diseases are common human conditions, and their detection and diagnosis are necessary. Because of the influence of doctors' subjectivity and skin trauma, traditional detection methods are inadequate for accurate and effective diagnosis of skin diseases. Therefore, skin imaging techniques are gradually being used for diagnosis. The photoacoustic imaging technique is an emerging imaging method that combines the high contrast of optical imaging with the deep imaging advantages of ultrasound imaging. Photoacoustic images provide structural and functional information to assist doctors in diagnosing diseases and to improve the accuracy of assessment and treatment. Photoacoustic skin imaging technology can satisfy imaging requirements of different hardware configurations, and its variety of hardware forms ensures that the technology can achieve microscopic and macroscopic imaging, with the potential to respond to diverse clinical needs. By using this technology, melanin and hemoglobin can be detected when capturing images of melanin particles and microvessels at different depths in the palm of the human hand, which can be used for diagnosing pigmented and vascular skin diseases. Photoacoustic skin imaging provides high-resolution images of all skin layers, which is crucial for the early diagnosis and evaluation of skin diseases. Therefore, this paper reviews the systematic classification of existing photoacoustic skin imaging modalities and the performance enhancement methods of image reconstruction algorithms, describes several applications of photoacoustic imaging in clinical human research, and analyzes the advantages and clinical potential of photoacoustic skin imaging as an emerging imaging technology. Thus, readers can gain a detailed and comprehensive understanding of photoacoustic skin imaging technology.
This paper reviews and summarizes the photoacoustic skin imaging technology. First, photoacoustic skin systems are classified based on the imaging modality. Existing photoacoustic skin imaging systems are divided into photoacoustic microscopic and other photoacoustic skin imaging systems. The latter includes photoacoustic tomography and ultrasound/photoacoustic multimodal-imaging systems. This article summarizes research with superior performance in terms of imaging principles, resolution, imaging depth, scanning modes, and other hardware specifications. The corresponding system components are outlined. Subsequently, the research progress in photoacoustic microscopic skin imaging systems and other photoacoustic skin imaging systems is summarized in terms of comparison of the overall system performance.
In studies on photoacoustic microscopy imaging systems, significant progress has been achieved in improving photoacoustic dermoscopy systems, in-vivo skin microimaging, and multiscale skin microimaging, resulting in advancements in system performance (Table 1). Moreover, for other types of photoacoustic skin imaging systems, studies have focused on various aspects, such as photoacoustic tomography of subcutaneous blood vessels in the extremities, three-dimensional photoacoustic tomography, diode laser-based skin tomography systems, and ultrasound/photoacoustic multimodal imaging systems. These investigations lead to noteworthy research outcomes and enhancements in the hardware performance of skin imaging systems (Table 2). In addition, the inclusion of commercial skin imaging systems in the listings validates the practical application value of photoacoustic skin imaging systems.
This paper summarizes existing methods and strategies for enhancing the performance of photoacoustic imaging systems, with a focus on advancements in reconstruction algorithms. The analysis categorizes and discusses these methods based on three main aspects: imaging resolution enhancement algorithms, imaging depth enhancement algorithms, and noise removal algorithms. Each category is analyzed chronologically, starting with an overview of conventional and pivotal performance enhancement algorithms. Subsequently, the discussion encompasses performance enhancement algorithms that integrate deep-learning techniques. Finally, existing specialized algorithms are discussed.
This paper summarizes research on the clinical application of photoacoustic skin imaging technology, classifies skin diseases into two categories (skin cancer and other skin diseases), and summarizes the photoacoustic skin imaging methods for detecting typical diseases. On the one hand, the research teams are currently focusing on detecting melanin and collagen content in the detection and investigation of skin cancer. On the other hand, the imaging of blood vessel shape and distribution pattern can be used as a criterion to determine whether the detected area is diseased and to identify the lesion boundary. In this paper, other skin diseases are classified as inflammatory, vascular, or pigmented according to their causative factors. The pathological features of the diseases and detection methods based on photoacoustic skin imaging technology are described using typical diseases as examples. A summary of the clinical applications of this technology for diverse skin diseases demonstrates its unique advantages and potential for clinical applications.
The concluding section of this article highlights the prevailing challenges of photoacoustic skin imaging and outlines the corresponding research directions aimed at addressing these issues. These challenges include resolving the issue of dynamic changes in clinical data, advancing multimodal imaging capabilities, developing user-friendly imaging devices, and establishing standardized imaging protocols and data analysis techniques.
Photoacoustic skin imaging is an emerging technique with several advantages, such as excellent imaging quality, cost-effectiveness, tissue safety, and promising clinical potential. Photoacoustic imaging is anticipated to become widely used in the future for clinical skin examinations. Further exploration and development of photoacoustic skin imaging technology are required to advance its clinical applications and facilitate its integration into medical practice.
