Near-infrared confocal imaging during mini-laparoscopy: A novel rigid endomicroscope with increased imaging plane depth

Abstract

Histopathology is the gold standard in the diagnosis of liver diseases but may be complicated by sampling error and bleeding. Confocal laser endomicroscopy (CLE) is a novel imaging modality providing in vivo histology. Previous studies using CLE for liver microscopy suffered from limited imaging depth using blue laser light and fluorescein. The aim of the current study was to evaluate a novel near-infrared (NIR) light probe with indocyanine green (ICG) contrast for in vivo confocal imaging of the human liver during mini-laparoscopy. The hand-held rigid laparoscopy probe (diameter 6.3mm) used a 780 nm diode laser. Subsurface images at different depths with < 1 microm lateral resolution were generated in real time by gently placing the sterile probe onto the liver in 22 patients under conscious analgo-sedation. Targeted biopsy was performed for histopathological correlation. Maximum imaging depth was >350 microm. Typical aspects of normal liver architecture and liver diseases, such as nuclei, sinusoids, fibrous tissue, fatty inclusions, and bile ducts but not inflammation could be visualized at high resolution. The presence of steatosis and fibrosis was predicted correctly in 81% and 90%, respectively. No liver damage or severe adverse events occurred. For the first time, ICG-augmented confocal mini-laparoscopy with a novel NIR probe allowed in vivo microscopy of human liver diseases, and with deeper imaging compared to the so far available blue laser systems. Such an increase of imaging depth could potentially also be used for submucosal imaging of the GI tract.