Photoacoustic Microscopy Offers a New Perspective on Imaging of Vascular Anomalies: A Case Series of Venous Malformations

Objectives: Vascular malformations are mostly benign but can potentially be life-threatening or function-threatening when involving vital structures or when associated with overgrowth syndromes. Yet, for these lesions that are predominantly cutaneous, diagnostic techniques like ultrasonography and magnetic resonance imaging may be inadequate in the characterization of these superficial lesions; leaving the alternative of invasive tissue biopsies. Methods: We explore an emerging imaging modality via the photoacoustic microscope, which relies on the optical properties of tissues—allowing the detection of hemoglobin, water, lipids, and other light-absorbing chromophores, resulting in greater contrast and spatial resolution than conventional ultrasonography. We detail a case series of 8 pediatric patients with venous malformations who presented at the Vascular Anomalies Clinic in KK Women’s & Children’s Hospital. The photoacoustic microscope device was applied to lesional and control skin in each patient, with measurements taken twice for each site. Results: Despite the small sample size, there was discernible visual and quantitative difference in vessel caliber and length between lesional and control skin—the majority of venous malformations had vessels with larger diameters and lengths than control vessels. Of sampled vessels, the diameter of vessels was larger in the lesional sample in 85.7% with a mean difference of +10.4 μm ( P = .02); whereas 83.3% of studied vessels had longer vessel lengths in the lesional sample with a mean difference of +81.3 μm ( P = .20). Conclusion: This descriptive case series serves as a pilot exploratory study to investigate vascular parameters (ie, vessel length and diameter) of venous malformations with an alternative noninvasive imaging tool like photoacoustic imaging, which provides higher resolution visualization and characterization of vessel architecture in superficial vascular anomalies. Subsequent studies building on this preliminary study data may be performed to compare venous malformations to other vascular anomalies. Future applications include the development of diagnostic algorithms for various vascular lesions to aid in rapid bedside diagnosis, visualization of the effects of treatment in real-time, and defining prognostic markers to determine response to treatment.