Photoacoustic imaging-based assessment of vascular changes in scars: a retrospective analysis of factors influencing PDL treatment efficacy

Pulsed dye laser (PDL) is widely used for hypervascular scars, but real-time evaluation of vascular responses remains limited. Photoacoustic imaging (PAI) enables noninvasive, high-resolution assessment of skin microvasculature. To assess whether PAI can visualize post-PDL vascular changes in real time and identify factors influencing efficacy. This single-center retrospective study analyzed 32 scars treated with 595-nm PDL. Patients were grouped by pulse duration/fluence combination (0.45–6.0 J/cm², 1.5–8.0 J/cm², or 3.0–10.0 J/cm²) or by endpoint (purpuric or nonpurpuric response). PAI, Antera 3D, and Vancouver Scar Scale (VSS) assessments were performed at baseline, immediately after treatment, and 1 month later. PAI enabled real-time, layer-specific visualization of vascular change, a capability that is less readily achievable with the VSS or Antera 3D. No statistically detectable association was identified between the parameter combinations and PDL outcomes. By contrast, the treatment endpoint was significantly associated with vascular outcomes: compared with purpuric treatment, nonpurpuric treatment showed lower adjusted full-dermis vessel density (30.25% vs. 49.29%; difference, − 19.04%; 95% CI, − 28.12 to − 9.97; Holm-adjusted P < 0.001) and smaller vessel diameter (278.74 μm vs. 428.36 μm; ratio, 0.651; 95% CI, 0.500–0.846; Holm-adjusted P = 0.002). Layer-specific outcomes also showed a similar direction of effect. In the exploratory repeated-treatment subset, NPUR was associated with progressive vascular improvement. PAI helps characterize vascular features and may provide additional information to support overall treatment parameter selection. Treatment endpoint was significant correlated to vascular efficacy. PAI suggests that vascular closure without purpura maybe potentially favorable.