Interpretation of Near-Infrared Imaging in Acute and Chronic Wound Care

Redefining Wound Healing Using Near-Infrared Spectroscopy

OBJECTIVE

No standard definition for a completely healed wound currently exists; it is recommended that providers use a reliable wound assessment tool to determine healing. The objective of this feasibility study was to determine if a point-of-care, noncontact, near-infrared (NIR) imaging device could provide an objective measure of wound resolution and guide clinical decision-making for the optimal time to transition from protective wound dressings and gradual return to full activity.

METHODS

In this single-center feasibility study, adult patients 18 years and older with a lower extremity wound of any size and etiology were seen weekly for wound assessment and standard-of-care treatment. The researchers performed serial imaging with a point-of-care, noncontact, NIR imaging device (Snapshot NIR ; Kent Imaging Inc) to assess the wound and surrounding skin and evaluated the difference in time to 100% reepithelialization on visual inspection and homogeneous tissue oxygen saturation levels at the wound site and surrounding closed skin envelope.

RESULTS

An average time difference of 13.5 ± 10 days (median, 12 days; range, 0-35 days) was observed between 100% reepithelialization on visual wound inspection and imaging assessment. Further, NIR imaging could determine when a patient was at risk for recurrent wound breakdown.

CONCLUSIONS

The addition of point-of-care, noncontact, NIR imaging may help guide clinical decision-making for the optimal time to transition from protective wound dressings with gradual return to full activity and minimize wound recurrence.

Jet Lavage Irrigation Resolves Stage 4 Pelvic Pressure Injury Undermining

OBJECTIVE

Patients with stage 4 pelvic pressure injuries that have large, undermined cavities are at high risk for treatment failure and often fall into the category of palliative care. This case series identified five cases where treatment had stalled, and surgical reconstructive options were limited. Jet lavage irrigation in the outpatient setting was assessed as a treatment alternative.

METHODS

From an investigational review board study assessing the use of low-pressure jet lavage irrigation in the outpatient setting for chronic wounds, five patients were identified where the wound dimension increased at least 50% resulting from undermined cavities. All were considered high risk with Charlson Comorbidity Index scores of 5 or greater, and their wound healing had stalled with extended treatments of topicals and medicated dressings. A team of physical therapists irrigated these patients' wounds at the bedside with 3 L of saline 3 to 5 days per week using a special long irrigation tip to reach the depth of the undermined cavity. Digital planimetry was used to assess healing with wound size as the outcome.

RESULTS

Reduction of the undermined cavities was seen early within the first 3 weeks. No patient developed wound sepsis, and bacterial contamination was determined by use of autofluorescence digital imaging. Undermining resolution occurred in four patients, and one patient with an improving wound died of COVID-19.

CONCLUSIONS

This simple method offered clear benefits in each patient, but only one patient survived to complete wound healing. Patient and family satisfaction were high regarding the treatment, which created a painless, odor-free wound.

Arterial spin labeling magnetic resonance imaging quantifies tissue perfusion around foot ulcers

Objective

Tools that quantify tissue perfusion of the foot are deficient, contributing to the uncertainty in predicting ulcer healing potential. This pilot study aims to quantify peri-wound foot perfusion at various tissue depths using a novel application of pseudo-continuous arterial spin labeling magnetic resonance imaging.

Methods

Ten diabetic patients with neuropathic wounds and 20 healthy volunteers without wounds were recruited. Wounds were graded according to the Wound, Ischemia, Foot Infection (WIfI) system. All subjects underwent a noncontrasted ASL MRI of the foot for perfusion measurements. For healthy volunteers, perfusion was compared at rest and during sustained toe flexion between four regions: lateral plantar, medial plantar, lateral calcaneal, and medial calcaneal. Evaluations of diabetic volunteers compared perfusion between four zones: wound, near border, far border, and remote. Remote zone perfusion in diabetics was compared with perfusion in the plantar foot of healthy volunteers.

Results

There were 11 wounds, which were located over the metatarsal heads in five, the stump of a transmetatarsal amputation in three, the heel in two, and the mid foot in one. The median WIfI stage was 2. One patient had a WIfI ischemia grade of 1; the remaining patients' grades were 0. The mean ankle-brachial index was 1.0 ± 0.3. There were two patients with a WIfI foot infection grade of 1; the remaining patients' grades were 0. In healthy volunteers, plantar foot perfusion with sustained toe flexion was 43.9 ± 1.7 mL/100g/min and significantly higher than perfusion at rest (27.3 ± 2.7 mL/100g/min; P < .001). In diabetic patients, perfusion at the wound, near border, far border, and remote regions was 96.1 ± 10.7, 92.7 ± 9.4, 73.4 ± 8.2, and 62.8 ± 2.7 mL/100g/min. Although this perfusion pattern persisted throughout the depth of the wound, perfusion decreased with tissue depth. In the near border, perfusion at 20% of the wound depth was 124.0 ± 35.6 mL/100g/min and 69.9 ± 10.1 mL/100g/min at 100% (P = .006). Lastly, remote perfusion in diabetics was 2.3 times the plantar perfusion in healthy volunteers (27.3 ± 2.7 mL/100g/min; P < .001).

Conclusions

The pattern of resting tissue perfusion around nonischemic diabetic foot ulcers was successfully quantified with arterial spin labeling magnetic resonance imaging. Diabetic patients with wounds were hyperemic compared with healthy volunteers. There was a 1.5-fold increase in peri-wound tissue perfusion relative to the rest of the foot. This study is the first step in developing a tool to assess the perfusion deficit in ischemic wounds.