Imaging in Chronic Wound Diagnostics

Abstract

Significance: Chronic wounds affect millions of patients worldwide, placing a huge burden on health care resources. Although significant progress has been made in the development of wound treatments, very few advances have been made in wound diagnosis. Recent Advances: Standard imaging methods like computed tomography, single-photon emission computed tomography, magnetic resonance imaging, terahertz imaging, and ultrasound imaging have been widely employed in wound diagnostics. A number of noninvasive optical imaging modalities like optical coherence tomography, near-infrared spectroscopy, laser Doppler imaging, spatial frequency domain imaging, digital camera imaging, and thermal and fluorescence imaging have emerged over the years. Critical Issues: While standard diagnostic wound imaging modalities provide valuable information, they cannot account for dynamic changes in the wound environment. In addition, they lack the capability to predict the healing outcome. Thus, there remains a pressing need for more efficient methods that can not only indicate the current state of the wound but also help determine whether the wound is on track to heal normally. Future Directions: Many imaging probes have been fabricated and shown to provide real-time assessment of tissue microenvironment and inflammatory responses in vivo. These probes have been demonstrated to noninvasively detect various changes in the wound environment, which include tissue pH, reactive oxygen species, fibrin deposition, matrix metalloproteinase production, and macrophage accumulation. This review summarizes the creation of these probes and their potential implications in wound monitoring.

Keywords: chronic wound diagnostics; luminescence; neutrophils; pH; reactive oxygen species; wound imaging probes.

Ashwin Nair, PhD

Liping Tang, PhD

Figure 1.

A brief overview of wound analysis using Digital Planimetry.

Figure 2.

Luminescence imaging of pH during cutaneous wound healing. [Image courtesy from Schreml et al. (2011). “Copyright (2010) National Academy of Sciences.”]

Figure 3.

Illustration showing simultaneous imaging of pH and pO₂ in wounds using a digital camera fitted with a 405 nm-LED ring light and an emission filter for photographing wounds covered in a sensor film to generate pO₂ and pH maps comparing acute and chronic wounds.

Figure 4.

Illustration showing the application of ROS ratiometric probe on open infection wounds in a murine model. None, Medium, and High indicate various amounts of bacteria administered onto open wounds. The fluorescent, chemiluminescent, and superimposed images reflect the amounts of administered probes, ROS activities, and ratiometric ROS activities, respectively. The overall results show that, with the same amounts of probes administered, increase administered bacteria numbers intensify ratiometric ROS signals. ROS, reactive oxygen species.