Applications of Laser Speckle Contrast Imaging Technology in Dermatology

Abstract

Laser speckle contrast imaging or laser speckle imaging (LSI) is a noninvasive imaging technology that can detect areas of dynamic perfusion or vascular flow. Thus, LSI has shown increasing diagnostic utility in various pathologies and has been employed for intraoperative, postoperative, and long-term monitoring in many medical specialties. Recently, LSI has gained traction in clinical dermatology because it can be effective in the assessment of pathologies that are associated with increased perfusion and hypervascularity compared with that of normal tissue. To date, LSI has been found to be highly accurate in monitoring skin graft reperfusion, determining the severity of burns, evaluating neurosurgical revascularization, assessing persistent perfusion in capillary malformations after laser therapy, and differentiating malignant and benign skin lesions. LSI affords the advantage of noninvasively assessing lesions before more invasive methods of diagnosis, such as tissue biopsy, while remaining inexpensive and exhibiting no adverse events to date. However, potential obstacles to its clinical use include tissue movement artifact, primarily qualitative data, and unclear impact on clinical practice given the lack of superiority data compared with the current standard-of-care diagnostic methods. In this review, we discuss the clinical applications of LSI in dermatology for use in the diagnosis and monitoring of vascular, neoplastic, and inflammatory skin conditions.

Figure 1

Cartoon rendering LSI device function. Low-intensity, near-infrared coherent light illuminates the skin surface with a targeted lesion (1). Light is reflected toward the device sensor, allowing information about blood flow over time to be captured by the camera (2). Granular pixel pattern is analyzed using ImageJ or MATLAB software (3). LSI, laser speckle imaging.

Figure 2

Laser speckle images in normal versus lesional skin in a patient with biopsy-proven melanoma. The x- and y-axes represent pixel positions, and the color maps indicate the value of K, the local spatial variance or speckle contrast. Areas with higher blood flow have lower contrast or K. All images were captured with a laser wavelength of 785 nm and a circular aperture of 2 cm in diameter. Spatial correlation was captured over 7 × 7 pixels, and temporal correlation was analyzed over 49 images. (a) Left panel: Laser speckle images captured over normal skin in a patient seen in a dermatology clinic at the Medical University of South Carolina (Charleston, SC). Imaging of normal skin resulted in a homogeneous laser speckle pattern. (b) Right panel: Laser speckle images captured in the same patient over a lesion of cancer, confirmed with biopsy to be malignant melanoma. Imaging of melanoma shows higher blood flow around the lesion periphery than at the center of the lesion in temporal correlation as well as higher than in the control skin in a. Spatial and temporal images are similar, with improved spatial resolution reflected in the temporal correlation.

Figure 3

Laser speckle images in normal versus lesional skin in a patient with a cherry angioma. As in Figure 2, the x- and y-axes represent pixel positions, and the color maps indicate the value of K, the local spatial variance or speckle contrast. Areas with higher blood flow have lower contrast or K. All images were captured with a laser wavelength of 785 nm and a circular aperture of 2 cm in diameter. Spatial correlation was captured over 7 × 7 pixels, and temporal correlation was analyzed over 49 images. (a) Left panel: Laser speckle images captured over normal skin. Again, imaging of normal skin resulted in a homogeneous laser speckle pattern. (b) Right panel: Laser speckle images captured in the same patient over a stable cherry angioma. Imaging of cherry angioma shows overall higher blood flow than in control skin, with pinpoint areas of highest blood flow within clumped lesional blood vessels, best appreciated in spatial correlation. Temporal correlation depicts less change in speckle contrast over time than in the contrast over one image using spatial correlation.