Three-dimensional ultrasound strain tensor imaging for classifying chronic lower back pain

Chronic myofascial pain (MP) that often appears as chronic lower back pain (cLBP) is a significant public health problem. Lack of reliable quantitative biomarkers makes the diagnosis still challenging in current clinics. This research aims to use 3-D-ultrasound to develop a classifier to quantitatively identify different cLBP cases including those with MP points (trigger or tender points) and without MP points. The hypothesis is from a previous study where reduced shear motion in the thoracolumbar fascia indicates tissue stiffening due to cLBP. We developed an approach using row-column-addressing (RCA) array to record tissue motions during lower back flexion in 3-D, followed by tissue motion tracking and 3-D strain tensor computation. Experimental results of the shear strain tensors were obtained from 81 human back sides including 34 labeled to have MP points (19 are trigger points). Significantly higher mean (p-value = 0.03) and median (p-value = 0.009) of the shear strain were found in cases with MP points. Area under (AUC) the receiver operating characteristic (ROC) curve were around 0.63 either using mean or median to classify cases with or without MP points. The preliminary result demonstrated an encouraging approach to be further developed as a surrogate biomarker to diagnose cLBP.