Multispectral fluorescence imaging during laparoscopic hybrid sentinel node biopsy

Objectives Recently, the hybrid tracer indocyanine green (ICG)-99mTc-nanocolloid allowing for combined radioactive/fluorescence detection was successfully introduced for sentinel node (SN) biopsy. However, in laparoscopic procedures the limited penetration depth of ICG may difficult lymph duct visualization Multispectral fluorescence imaging using dyes with different penetration depth, e.g. fluorescein and the near-infrared dye ICG, can help the surgeon by providing optical feedback on different physiological/molecular features. In this study, we evaluated the use of fluorescein for laparoscopic lymphangiography in addition to SN detection with ICG-99mTc-nanocolloid in a protocol of multispectral imaging.

Methods For SN identification, the hybrid tracer ICG-99mTc-nanocolloid was injected under transrectal ultrasound guidance (total volume 2mL). SPECT/CT imaging was performed directly after the late lymphoscintigram (2 hrs) in order to determine the number and location of the SNs. Just before the start of the operation, 2 mL fluorescein (200 mg) was injected under transrectal ultrasound guidance. Intraoperatively a multispectral fluorescence laparoscope (KARL STORZ, Tuttlingen, Germany) was used.

Results Preoperative imaging with ICG-99mTc-nanocolloid revealed on average 4 SNs per patient. During surgery, fluorescence imaging of fluorescein allowed real-time visualization of the lymphatic ducts draining from the prostate to the SN; all SNs could be accurately identified using the ICG settings of the fluorescence laparoscope. Ex vivo, the presence of the hybrid tracer (ICG-99mTc-nanocolloid) and fluorescein in the SN and prostate could be confirmed.

Conclusions Multispectral fluorescence imaging has the potential to intraoperatively visualize complementary features that jointly aid laparoscopic SN retrieval.

Research Support This research was partially supported by an NWO-STW-VIDI grant (no. STW-BGT11272).