Evaluation of diabetic foot ulcer healing with hyperspectral imaging of oxyhemoglobin and deoxyhemoglobin

Abstract

Objective: Foot ulceration remains a major health problem for diabetic patients and has a major impact on the cost of diabetes treatment. We tested a hyperspectral imaging technology that quantifies cutaneous tissue hemoglobin oxygenation and generated anatomically relevant tissue oxygenation maps to assess the healing potential of diabetic foot ulcers (DFUs).

Research design and methods: A prospective single-arm blinded study was completed in which 66 patients with type 1 and type 2 diabetes were enrolled and followed over a 24-week period. Clinical, medical, and diabetes histories were collected. Transcutaneous oxygen tension was measured at the ankles. Superficial tissue oxyhemoglobin (oxy) and deoxyhemoglobin (deoxy) were measured with hyperspectral imaging from intact tissue bordering the ulcer. A healing index derived from oxy and deoxy values was used to assess the potential for healing.

Results: Fifty-four patients with 73 ulcers completed the study; at 24 weeks, 54 ulcers healed while 19 ulcers did not heal. When using the healing index to predict healing, the sensitivity was 80% (43 of 54), the specificity was 74% (14 of 19), and the positive predictive value was 90% (43 of 48). The sensitivity, specificity, and positive predictive values increased to 86, 88, and 96%, respectively, when removing three false-positive osteomyelitis cases and four false-negative cases due to measurements on a callus. The results indicate that cutaneous tissue oxygenation correlates with wound healing in diabetic patients.

Conclusions: Hyperspectral imaging of tissue oxy and deoxy may predict the healing of DFUs with high sensitivity and specificity based on information obtained from a single visit.

Trial registration: ClinicalTrials.gov NCT00617916.

Figure 1

Visible and hyperspectral image of a healing DFU taken with the HTOM system. The top panels show a healed DFU case. HTOM values are 75, 34, and 69% for oxy, deoxy, and StO₂, respectively. The bottom panels show a nonhealed DFU case. HTOM values are 60, 53, and 53% for oxy, deoxy, and StO₂, respectively. Tissue oxygenation is higher in the healed ulcer as seen by the more purplish tone compared with the more cyan/green tone. Mean oxy and deoxy values were determined for each ulcer from an approximate 1-cm–thick band drawn within the periwound area.

Figure 2

A: Oxy and deoxy values for healed and nonhealed DFUs. The diagonal solid line represents the decision line for a healing algorithm based on oxy and deoxy values. Ninety percent of points lying to the right of the line healed. The diagonal dashed line represents a second decision line where 87% of the points (seven of eight excluding calluses) lying to the left of the line did not heal. B: Probability of healing based on HTOM healing index for healed and nonhealed DFUs. An ulcer with a positive healing index has a higher likelihood to heal. ♢, Ulcers with underlying osteomyelitis that did not heal; ♦, ulcers that did not heal at 24 weeks; ○, ulcers that healed and were surrounded by callus; , ulcers that healed at 24 weeks. arb, arbitrary.