Page 73 - Fluorescence-guided cancer surgery

INTRODUCTION
In transsphenoidal surgery it is important to be able to distinguish between normal pituitary gland and pituitary adenoma tissue for two reasons: 1) to obtain a complete tumor resection and 2) to preserve endocrine function. The vascular pattern between the normal pituitary gland and tumor tissue di ers1;2. This di erence can be shown with preoperative magnetic resonance imaging (MRI), making use of dynamic administration of gadolinium. Normal pituitary tissue is visualized by contrast enhancement3. However, during surgery, the identi cation of normal gland and adenoma is based on di erences in tissue characteristics, such as colour and consistency. This di erence can be di cult to detect.
Transsphenoidal surgery is an established and relatively safe procedure. More than 95% of the pituitary tumors are operated via this approach4. Unfortunately, remission rates of hormone secreting tumors are not perfect, while surgery induced pituitary de ciencies still occur5. Moreover, in patients with initial remission, recurrences occur due to endocrine activity of postoperative tumor remnants. It is therefore likely that the success rate of surgery can be improved by increasing visual di erentiation between adenoma and the normal gland.
Near-infrared (NIR) uorescence imaging is an innovative technique to visualize tumors, vital structures, and lymph nodes during surgery6. It is currently clinically used for several medical indications. These are intraoperative imaging of liver metastases, breast cancer and parathyroid adenomas7-10. One of the clinically available NIR uorescent contrast agents is indocyanine green (ICG). ICG is an ideal agent for real-time visualisation of di erences in tissue vascularisation. The excitation and emission pro les of ICG in the NIR light spectrum make it possible to visualize blood vessels covered by a few millimetres of tissue. At present, ICG-imaging is widely used in a variety of surgical procedures6;11, including several cerebrovascular procedures in neurosurgical practice12;13.
Litvack et al. rst reported the use of ICG in endoscopic pituitary surgery in 201214. In this feasibility study, up to 75 mg ICG was administered intravenously for each procedure. An endoscopic NIR uorescence imaging system was used to capture uorescent signal. The authors concluded that NIR uorescence- guided endoscopy was a promising intraoperative modality towards visually distinguishing adenoma from normal gland tissue and thus possibly facilitating
Imaging in pituitary surgery 71