Automated measurement of pressure injury through image processing

Abstract

Once our algorithm is further developed, clinicians can be provided with an objective, reliable and efficient computational tool for segmentation and measurement of pressure injuries. With this, clinicians will be able to more effectively monitor the healing process of pressure injuries.

The characteristics of pressure injury photographs from the electronic health record in clinical settings

“…The centre of PI was defined as the centre of the rectangle enclosing the PI. The methods concerning (i) the automatic segmentation of the PI from a PI photograph and (ii) building a rectangle to enclose the PI are detailed in our previous publication (Li & Mathews, ). The results of this operation demonstrate that 80.1% of the PIs were located in the centre zone of the PI photographs (part b).…”

“…From previous studies and existing protocols (Li & Mathews, ; Palmer et al., ; Rennert et al., ), the shooting angle of the lens of the digital camera needs to be oriented perpendicularly to the plane of the PI when taking the photograph. The camera shooting angle is defined as the angle of the camera as it deviates from the perpendicular vis‐à‐vis the PI surface, as shown in Figure .…”

“…To correct this distortion, a process of perspective transformation can convert photographs from a three‐dimensional frame to a two‐dimensional frame. For example, Li and Mathews () have developed an image processing tool to measure wound size from PI photographs taken in clinical settings. One of the primary functions of this tool is to identify the shooting angle of the camera, relative to the PI bed, and perform the perspective transformation.…”

“…To serve this purpose, clinicians require little in the way of photographic technique. However, to render the PI photographs compatible for the current systems of telemedicine and image processing, certain standards and techniques must be followed when photographing the PIs: Use of a digital camera with industry‐standard resolution (i.e., 10.0 megapixel) for high‐quality images; Removal of all dressings, cleansing of the PI with saline and exposure of the PI surface to the photographer (Rennert, Golinko, Kaplan, Flattau, & Brem, ; Xakellis & Frantz, ); Positioning the camera to include the PI, healthy skin and surrounding cellulitis in the frame of the photograph—the zoom function can be used to adjust the framing; Positioning the camera perpendicularly to the PI—slight deviation in angle can change perspective, depth and shadow (Li & Mathews, ; Palmer, Rin, & Ledgard, ; Rennert et al., ); Holding a small measurement grid flat along edge of the PI without covering any part of the PI (Li & Mathews, ; Mager, ); Taking the photographs under adequate light—a flash can be used ensure adequate and consistent lighting if necessary. …”

“…Furthermore, image processing technologies are applied to PI photography. Through this image processing, not only the dimensions of PIs can be measured (Ahmad Fauzi et al., ; Li & Mathews, ), but also the condition of the wound tissue—and the wound bed—can be analysed without physically touching the wound bed (Ahmad Fauzi et al., ; Houghton et al., ; Rennert et al., ).…”