Interventional optical imaging detects tiny liver lesions

Challenging imaging artifacts in image guidance for interventional liver procedures such as those caused by biopsy needle could be ameliorated with an optical imaging technique called epifluorescence imaging, according to a study published Oct. 10 ahead of print in Radiology.

Great strides have been made in the use of MR, CT and ultrasonography (US) image-guidance for interventional radiology procedures. Percutaneous hepatic interventions are among the most commonly performed interventions and all three conventional imaging techniques, while useful, are hampered when lesions are very small. But clinicians aim to go as small as possible for earlier detection of disease.

“As cross-sectional diagnostic imaging techniques have improved during the past two decades, the ability to detect focal hepatic lesions earlier in the disease process has improved,” wrote Rahul A. Sheth, MD, from Massachusetts General Hospital in Charlestown, et al. “Consequently, the rate of percutaneous interventions in small focal hepatic lesions less than 30 millimeters in size has increased.”

The need to find alternative methods of image guidance grows as lesions get smaller and in some cases, ultrasonography will not even detect certain lesions. 

“Operator confidence in accurate needle placement with the use of conventional CT or US guidance for biopsies and ablations decreases as target lesions decrease in size,” the researchers wrote. “There exists a clinical need for a real-time, accurate method for confirming proper needle position during percutaneous hepatic interventions to complement existing image guidance technologies.

To address this need, researchers developed real-time, exogenous administration of organic fluorochromes using a indocyanine green agent that fluoresces in the near-infrared range when lased. The excitation is detected using an ultra-high resolution camera. The technology is called an epifluorescence optical molecular imaging (OMI) system. The technique has already been validated in preclinical studies. For this study, researchers assessed the imaging system in five human subjects during liver resection surgery for intrahepatic colorectal cancer metastases and hepatocellular carcinomas.

Results of this preliminary human study were encouraging. The system was able to accurately detect suspected liver lesions and is being groomed for additional trials with larger patient populations.

“We have demonstrated the feasibility of OMI assistance for percutaneous interventions,” wrote Sheth et al. “We applied a handheld OMI device that complements existing interventional needles and imaging technologies to provide intraprocedural confirmation of needle tip position during percutaneous liver biopsies and ablations, with minimal additional time; we also developed and evaluated a point-of-care OMI system to measure [indocyanine green] localization to core biopsy specimens."