Interventional optical molecular imaging: Development and application of a translatable handheld imaging device for percutaneous sampling of focal hepatic lesions

Objectives With features such as high spatial resolution, real-time image display, and highly sensitive imaging agents, optical molecular imaging has the potential to significantly advance image guidance during interventional radiology (IR) procedures. We evaluated the applicability of a custom-designed, translatable, catheter-based handheld imaging system towards one of the most common IR procedures, namely, the percutaneous sampling of focal hepatic lesions. We additionally assessed the ability of the clinically approved imaging agent indocyanine green (ICG) to localize with high target-to-background ratios (TBRs) within focal hepatic lesions.

Methods A handheld optical molecular imaging device was constructed to slide through the introducer needle of a standard 18 gauge percutaneous biopsy kit. Intrahepatic colorectal cancer metastases (human colorectal cancer cell line HT-29) were generated in nude mice (n = 25). Epifluorescence imaging of the tumors was performed 4 weeks later at various time points following the intravenous administration of 0.5mg/kg ICG. The mice were then imaged using the custom designed handheld imaging device, and measurements of fluorescence intensity within normal liver versus tumor were acquired.

Results There was avid localization of ICG to the focal hepatic lesions, with a TBR of ~ 3.5 - 4.0. The TBR was relatively invariant at 3, 6, and 24 hours. Similarly, fluorescence intensity within the tumors was significantly greater than within normal liver as detected by the handheld imaging system, with a TBR of ~ 4.0. A core biopsy of tumor and normal adjacent liver using a standard 18 gauge biopsy needle demonstrates a sharp margin of fluorescence intensity at the tumor-liver interface.

Conclusions The custom-designed molecular imaging device, in combination with ICG, was able to readily differentiate between normal versus malignant tissue, an ability that is of tremendous potential utility in IR. Both device and imaging agent are ready for immediate clinical translation.