Combined use of intraoperative ultrasound and indocyanine green fluorescence imaging to detect liver metastases from colorectal cancer

Abstract

Objectives: Surgical excision is the standard strategy for managing liver metastases from colorectal carcinoma. The achievement of negative (R0) margins is a major determinant of disease-free survival in these patients. Current imaging techniques are of limited value in achieving this goal. A new approach to the intraoperative detection of colorectal liver metastatic tissue based on the emission of indocyanine green (ICG) fluorescence was evaluated.

Methods: A total of 25 consecutive patients with liver metastases from primary colorectal cancers who were eligible for liver resection received a bolus of ICG (0.5 mg/kg body weight) 24 h before surgery. During surgery, ICG fluorescence, which accumulates around lesions as a result of defective biliary clearance, was detected with a near-infrared camera system, the Photodynamic Eye (PDE). Numbers of lesions detected by, respectively, PDE + ICG, intraoperative ultrasound (IOUS) and preoperative computed tomography (CT) were recorded.

Results: The near-infrared camera plus ICG revealed a total of 77 metastatic liver nodules. Preoperative CT demonstrated 45 (58.4%) and IOUS showed 55 (71.4%). Preoperative CT and IOUS alone were inferior to the combined use of PDE + ICG and IOUS in the detection of lesions of ≤ 3 mm in size.

Conclusions: This experience suggests that PDE + ICG, combined with IOUS, may represent a safe and effective tool for ensuring the complete surgical eradication of liver metastases from colorectal cancer.

Figure 1

In computed tomography (a) and intraoperative ultrasound (b), findings appear to be unremarkable. (c) Near-infrared imaging using the Photodynamic Eye demonstrates a nodule

Figure 2

Stratification of findings among the cases. Only one event was deemed a false positive. CT, computed tomography; IOUS, intraoperative ultrasound; PDE, Photodynamic Eye; ICG, indocyanine green

Figure 3

Overall evaluation of all observed nodules. CT, computed tomography; IOUS, intraoperative ultrasound; PDE, Photodynamic Eye; NS, not significant

Figure 4

Stratification of the nodules by size shows no difference in findings of tumours of >3 mm. CT, computed tomography; IOUS, intraoperative ultrasound; PDE, Photodynamic Eye; NS, not significant

Figure 5

Stratification of the nodules by size shows that the combined use of intraoperative ultrasound and the Photodynamic Eye allows a significant advantage in the detection of nodules of ≤3 mm. CT, computed tomography; IOUS, intraoperative ultrasound; PDE, Photodynamic Eye; NS, not significant

Figure 6

The figure is a proof of concept demonstrated by resection specimens and associated images obtained using the Photodynamic Eye (PDE) with indocyanine green (ICG) staining. (a, b) When PDE + ICG is used to detect large nodules, it allows a safe resection in which the rim represents the limit of resection. A parenchyma-sparing resection is safer with this technique. (c, d) The PDE + ICG technique is particularly suited to demonstrating small nodules that may be missed by computed tomography and intraoperative ultrasound. The technique can be used to change the staging of the disease and possibly the therapeutic approach