Surgical Applications of Lymphatic Vessel Visualization Using Photoacoustic Imaging and Augmented Reality

Abstract

Lymphaticovenular anastomosis (LVA) is a widely performed surgical procedure for the treatment of lymphedema. For good LVA outcomes, identifying lymphatic vessels and venules is crucial. Photoacoustic lymphangiography (PAL) is a new technology for visualizing lymphatic vessels. It can depict lymphatic vessels at high resolution; therefore, this study focused on how to apply PAL for lymphatic surgery. To visualize lymphatic vessels, indocyanine green was injected as a color agent. PAI-05 was used as the photoacoustic imaging device. Lymphatic vessels and veins were visualized at 797- and 835-nm wavelengths. First, it was confirmed whether the branching of the vasculature as depicted by the PAL was consistent with the actual branching of the vasculature as confirmed intraoperatively. Second, to use PAL images for surgical planning, preoperative photoacoustic images were superimposed onto the patient limb through augmented reality (AR) glasses (MOVERIO Smart Glass BT-30E). Lymphatics and venule markings drawn using AR glasses were consistent with the actual intraoperative images obtained during LVA. To anastomose multiple lymphatic vessels, a site with abundant venous branching was selected as the incision site; and selecting the incision site became easier. The anatomical morphology obtained by PAL matched the surgical field. AR-based marking could be very useful in future LVA.

Imaging of the Lymphatic Vessels for Surgical Planning: A Systematic Review

“… 148 , 150 Lastly, the imaged anatomical morphology has also been successfully matched to the surgical field. 149 …”

“…Studies showed that 3D highresolution imaging and differentiation of lymphatic and blood vessels is possible along with DBF characterization. [145][146][147][148][149][150] Figure 7 shows example PAI images.…”

“…PAI also seemed to be less affected by thicker subcutaneous tissue146 but was less sensitive for ICG in the interstitium due to dilution 148,150. Lastly, the imaged anatomical morphology has also been successfully matched to the surgical field 149.…”

“…Light of the specific wavelength is absorbed by chromophores such as melanin, hemoglobin, or ICG, causing thermoelastic expansion and generating acoustic waves detected with an ultrasound transducer. Studies showed that 3D highresolution imaging and differentiation of lymphatic and blood vessels is possible along with DBF characterization [145][146][147][148][149][150]. Figure7shows example PAI images.Lymphedema severity classification was proposed based on visualization of lymphatic collectors, precollectors, and capillaries 148,150.…”

LED-based photoacoustic imaging for preoperative visualization of lymphatic vessels in patients with secondary limb lymphedema

“…Several clinical laser-based systems such as the PAI-05 [59] and the iThera Medical MSOT Acuity [60] , [61] have also been used for lymphatic vessel imaging, producing high-resolution images. However, these systems are bulky or not portable at all, extra safety precautions are obligatory, and computationally intensive post-processing steps are needed [50] , [51] , [62] . This adds further challenges to the clinical implementation in multiple settings such as outpatient clinics and operating rooms.…”