Page 67 - Fluorescence-guided cancer surgery

Laparoscopic imaging of hepatic uveal melanoma metastases 65
DISCUSSION
Because only 3% 15;16 of patients with uveal melanoma are candidates for curative resection of hepatic metastases, a precise and minimally invasive method for selecting appropriate candidates is desperately needed. To the best of our knowledge, this is the rst paper describing the use of laparoscopic NIR uorescence imaging with ICG for the detection and removal of liver metastasis in this disease. Due to hampered visibility and the inability to palpate the liver surface during laparoscopy, NIR uorescence imaging adds value to the procedure itself. In contrast to ultrasonography, which can only show where the resection margins can be kept before resection, NIR uorescence imaging provides real-time guidance, helps minimize the resection of normal liver tissue, and permits inspection of the area to ensure the completeness of tumor resection.
In all 3 patients of this study, lesions were found by NIR uorescence that were not seen on preoperative US and CT scans. Moreover, in one patient, one lesion intraoperatively characterized as hemangioma by visual inspection, and not identi ed by LUS, was successfully identi ed as metastasis with NIR uorescence imaging and could be radically removed under real-time uorescence guidance.
A major limitation of NIR uorescence imaging is its limited depth penetration of ≈ 5 mm. In gure 4, a depth penetration of at least 5 mm can be inferred because the NIR uorescence signal of the lesion was identi ed at the anterior surface of the liver (supplementary video part 1), while the lesion itself was located at the posterior surface of the liver. More sensitive imaging systems and uorophores with higher quantum yield could potentially increase depth penetration even further. Preoperative CT scanning and LUS do not have this disadvantage and are consequently more appropriate for deeper lesions. However, small and super cially located occult metastases are known to be di cult to detect using LUS and inspection. Although LUS is a reliable modality to identify liver metastases17, and still required to identify deep (≥ 5 mm) metastases in the liver, our results suggest that NIR uorescence imaging is complementary, and helps to nd small, super cially located lesions. In addition, as shown in the supplementary video, NIR uorescence imaging becomes of value in the resection of even deep lesions once they are initially identi ed.