Interventional optical molecular imaging guidance during percutaneous biopsy

Abstract

Purpose: To investigate indocyanine green (ICG) as a molecular beacon for malignant lesions within the liver and evaluate the ability of a developed handheld imaging system to allow measurement of ICG fluorescence within focal hepatic lesions with high target-to-background ratios in a mouse model.

Materials and methods: All animal experiments were approved by the institutional animal care committee. A handheld optical molecular imaging device was constructed to pass through the introducer needle of a standard percutaneous biopsy kit. An ex vivo phantom system was constructed to quantify tissue attenuation properties of ICG in liver parenchyma. Subsequently, intrahepatic colorectal cancer metastases were generated in nude mice, and epifluorescence imaging of ICG, as well as histologic analysis of the explanted livers, was performed at 3 weeks after implantation (n = 6). Epifluorescence imaging with the handheld imaging device was then performed on intrahepatic colorectal metastases after the administration of ICG (n = 15) at 3, 6, and 24 hours after injection. Target-to-background ratios were calculated for each time point. Subsequently, a core biopsy of intrahepatic colorectal metastases was performed by using a standard clinical 18-gauge biopsy needle.

Results: There was avid localization of ICG to the focal lesions at all time points. Similarly, fluorescence within the tumors was greater than that within normal liver, as detected with the handheld imaging system (mean target-to-background ratio ± standard deviation, 3.9 ± 0.2 at 24 hours). A core biopsy of tumor and normal adjacent liver by using a standard biopsy needle demonstrated a sharp margin of fluorescence intensity at the tumor-liver interface.

Conclusion: The custom-designed molecular imaging device, in combination with ICG, readily allowed differentiation between normal and malignant tissue in a murine model of intrahepatic colorectal metastasis.

Figure 1a:

Handheld interventional OMI device. (a) Schematic demonstrates the optical train of the handheld device. (b) Photograph of the device demonstrates that the imaging endoscope slides into a standard 17-gauge biopsy introducer needle. CCD = charge-coupled device.

Figure 1b:

Handheld interventional OMI device. (a) Schematic demonstrates the optical train of the handheld device. (b) Photograph of the device demonstrates that the imaging endoscope slides into a standard 17-gauge biopsy introducer needle. CCD = charge-coupled device.

Figure 2a:

Graphs from a phantom experiment of ICG fluorescence as a function of concentration and distance through liver. (a) There is marked ICG fluorescence above background levels through 5–10 mm of homogenized liver tissue. (b) ICG fluorescence is measurable over two orders of magnitude of ICG concentration through liver tissue. arb = arbitrary units.

Figure 2b:

Graphs from a phantom experiment of ICG fluorescence as a function of concentration and distance through liver. (a) There is marked ICG fluorescence above background levels through 5–10 mm of homogenized liver tissue. (b) ICG fluorescence is measurable over two orders of magnitude of ICG concentration through liver tissue. arb = arbitrary units.

Figure 3a:

Images demonstrate ex vivo imaging of intrahepatic colorectal metastasis xenograft. (a) Photograph shows an approximately 5-mm lesion implanted at the periphery of a mouse liver. (b) ICG fluorescence image shows that 6 hours after intravenous injection of ICG, there is avid localization of ICG to the tumor, with mild residual concentration of ICG within the hepatic parenchyma.

Figure 3b:

Images demonstrate ex vivo imaging of intrahepatic colorectal metastasis xenograft. (a) Photograph shows an approximately 5-mm lesion implanted at the periphery of a mouse liver. (b) ICG fluorescence image shows that 6 hours after intravenous injection of ICG, there is avid localization of ICG to the tumor, with mild residual concentration of ICG within the hepatic parenchyma.

Figure 4a:

Hematoxylin-eosin–stained and fluorescence microscopy images of intrahepatic colorectal tumor xenograft. (a) Hematoxylin-eosin staining at 40× magnification shows colorectal tumor with densely packed cells, abnormal nuclei, and high nuclear-cytoplasmic ratios. (b) A magnified view (100× magnification) of the tumor-liver margin demonstrates the sharp transition from normal to malignant cells. (c) The sharp tumor-liver margin is evident at ICG fluorescence imaging (100× magnification; excitation wavelength, 633 nm), with increased ICG uptake within the tumoral cells. Of note, pools of ICG within the hepatic parenchyma reflect normal excretion of ICG into biliary canaliculi.

Figure 4b:

Hematoxylin-eosin–stained and fluorescence microscopy images of intrahepatic colorectal tumor xenograft. (a) Hematoxylin-eosin staining at 40× magnification shows colorectal tumor with densely packed cells, abnormal nuclei, and high nuclear-cytoplasmic ratios. (b) A magnified view (100× magnification) of the tumor-liver margin demonstrates the sharp transition from normal to malignant cells. (c) The sharp tumor-liver margin is evident at ICG fluorescence imaging (100× magnification; excitation wavelength, 633 nm), with increased ICG uptake within the tumoral cells. Of note, pools of ICG within the hepatic parenchyma reflect normal excretion of ICG into biliary canaliculi.

Figure 4c:

Hematoxylin-eosin–stained and fluorescence microscopy images of intrahepatic colorectal tumor xenograft. (a) Hematoxylin-eosin staining at 40× magnification shows colorectal tumor with densely packed cells, abnormal nuclei, and high nuclear-cytoplasmic ratios. (b) A magnified view (100× magnification) of the tumor-liver margin demonstrates the sharp transition from normal to malignant cells. (c) The sharp tumor-liver margin is evident at ICG fluorescence imaging (100× magnification; excitation wavelength, 633 nm), with increased ICG uptake within the tumoral cells. Of note, pools of ICG within the hepatic parenchyma reflect normal excretion of ICG into biliary canaliculi.

Figure 5a:

(a–c) Surface reflectance and (d) endoscope-based NIR fluorescence images acquired 3 hours after injection of ICG by using the handheld OMI system demonstrate substantially elevated ICG uptake within the intrahepatic colorectal tumor relative to the adjacent hepatic parenchyma, allowing for ready differentiation between normal and malignant tissue. WL = white light.

Figure 5b:

(a–c) Surface reflectance and (d) endoscope-based NIR fluorescence images acquired 3 hours after injection of ICG by using the handheld OMI system demonstrate substantially elevated ICG uptake within the intrahepatic colorectal tumor relative to the adjacent hepatic parenchyma, allowing for ready differentiation between normal and malignant tissue. WL = white light.

Figure 5c:

(a–c) Surface reflectance and (d) endoscope-based NIR fluorescence images acquired 3 hours after injection of ICG by using the handheld OMI system demonstrate substantially elevated ICG uptake within the intrahepatic colorectal tumor relative to the adjacent hepatic parenchyma, allowing for ready differentiation between normal and malignant tissue. WL = white light.

Figure 5d:

(a–c) Surface reflectance and (d) endoscope-based NIR fluorescence images acquired 3 hours after injection of ICG by using the handheld OMI system demonstrate substantially elevated ICG uptake within the intrahepatic colorectal tumor relative to the adjacent hepatic parenchyma, allowing for ready differentiation between normal and malignant tissue. WL = white light.

Figure 6a:

(a) Graph shows time course of ICG uptake within focal hepatic tumors and demonstrates that the target-to-background ratio of ICG uptake is 3.9 ± 0.2 at 24 hours. (b) A sharp delineation between normal and malignant tissue can be seen in an 18-gauge core biopsy specimen. The image of the needle on the right is an overlay of the photograph of an 18-gauge core-biopsy needle on the left with the epifluorescence data of the core specimen. arb = arbitrary units.

Figure 6b:

(a) Graph shows time course of ICG uptake within focal hepatic tumors and demonstrates that the target-to-background ratio of ICG uptake is 3.9 ± 0.2 at 24 hours. (b) A sharp delineation between normal and malignant tissue can be seen in an 18-gauge core biopsy specimen. The image of the needle on the right is an overlay of the photograph of an 18-gauge core-biopsy needle on the left with the epifluorescence data of the core specimen. arb = arbitrary units.