1. A handheld optical molecular imaging system may help localize small, suspicious liver lesions during interventional radiology procedures that would otherwise be difficult to identify using current image guidance techniques.
Evidence Rating Level: 2 (Good)
Study Rundown: Focal liver lesions are commonly biopsied and treated using image guidance, which is quickly becoming the standard of care due to its high rates of technical success and few associated complications. Small lesions (<30mm) pose a particular challenge to interventionalists because they are difficult to visualize using standard computed tomography- or ultrasound-guided approaches, potentially increasing the number of false-negative biopsy results and decreasing overall treatment effectiveness. Optical molecular imaging (OMI) is an emerging technology that allows the interventionalist to confirm placement of a procedure needle within the liver tissue of interest by using a fluorophore called indocyanine green (ICG) that localizes to hepatocellular carcinomas (HCC) and intrahepatic colorectal cancer (iCRC) with a high target-to-background ratio (TBR). In the present study, OMI using ICG was shown to reliably confirm the location of suspicious focal liver lesions with a high rate of technical success, thus providing a theoretical framework for larger randomized, controlled trials. The study was limited by its small size and a large range of the background fluorescence intensities that could prevent localization of HCC or iCRC in patients with homogeneous or near-homogenous fluorescence patterns. Future studies of this technique would benefit from a larger, prospective methodology and the use of a fluorophore with higher sensitivity and specificity to particular cell types.
In-Depth [prospective cohort]: This was a single-center trial that included five patients with one or more hepatic lesions suspicious for HCC or iCRC metastasis. All enrolled patients were given an intravenous injection of the ICG fluorophore one day prior to image-guided percutaneous biopsy and/or ablation. A handheld OMI device was fashioned to obtain background and target fluorescence intensity measurements through an introducer needle. Among biopsied lesions, the final diagnosis was confirmed using subsequent pathologic analysis. In those cases where the target tissue was ablated, a one month post-procedural imaging evaluation was performed to compare the area of ablation to the targeted lesion. Of the five lesions biopsied, 80% (4/5) had tissue samples composed of either HCC, granulomatous inflammation, or iCRC, findings that suggest appropriate needle placement under OMI guidance with a good TBR. The fifth biopsy revealed benign liver parenchyma despite having a focus of fluorescence by OMI, and later evaluation of the procedure confirmed that the biopsy needle had been inappropriately placed 5 mm inferior to the identified lesion. Follow-up imaging of both ablated lesions (2/2, 100%) showed no evidence of residual disease at one month, also suggestive of appropriate needle placement under OMI guidance. There were no adverse events associated with administration of the fluorophore during or 7-days after the procedure.
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