Background: Lymphedema is a common complaint of post-breast cancer treatment. Some prior
ultrasound imaging studies of lymphedema-affected upper extremities focused upon estimating
the thickness of the dermis and subcutis areas. In contrast, however, the reliability
and validity of texture features derived from ultrasound images obtained using a low-cost
portable ultrasound device have not been reported. This study examined the reliability and
validity of the first and second order quantitative image texture measures, average pixel intensity
and entropy, and compared their site-specific correlations.
Methods and Results: A total of 10 ultrasound images of an ipsilateral affected elbow and
the corresponding unaffected contralateral elbow were obtained using a portable ultrasound
device. A Graphical User Interface software package for image analysis was developed and
tested. Entropy and average pixel intensity at six adjacent regions of interest corresponding
to the dermis and subcutis areas were calculated. Entropy had smaller coefficients of variation
for each image compared to average pixel intensity with the intracluster correlation reliability
coefficient for entropy being twice that of average pixel intensity. Both measures discriminated
between the affected and unaffected sites (p < 0.001). However, the correlation
between the two measures differed for affected (r = −0.060, p = 0.667) and unaffected
(r = +0.595, p < 0.001) sites.
Conclusions: The second order measure entropy is preferable to that of the first order average
pixel intensity as a measure of image texture to characterize ultrasound images of extremity
lymphedema.
