Page 81 - Fluorescence-guided cancer surgery

imaging. In comparison, in other studies an ICG dose between 2.5 mg, or 0.2 – 0.5 mg/kg was demonstrated successful for the assessment of tissue perfusion after intravenous administration15-17. For tumor imaging of colorectal or uveal melanoma liver metastases, intravenous administration of 10 mg ICG proved to be su cient7;18. Furthermore it allows for repeated injections, so that NIR uorescence imaging can be used during various phases of the tumor resection. The lower dose used in this study compared to the dose used by Litvack et al. appears su cient and leads to satisfactory results within the timing windows of imaging we used.
The observed FCR between normal gland and tumor tissue was 1.5 ± 0.2. The dynamic character of the imaging facilitated detection of a clear gradient between the normal pituitary gland and the adenoma. Our obtained quantitative ratios cannot be compared to results obtained by others, because only semi-qualitative results are reported yet14. To the best of our knowledge, to-date, no quantitative analysis of NIR uorescence imaging in pituitary surgery had been reported. In future studies, quantitative analysis of NIR uorescence imaging in pituitary surgery should become a standard in order to further objectively assess the additional value of this technique. A contrast ratio above 2 is generally considered optimal for intraoperative di erentiation between tissues. For example, in colorectal liver metastases18, breast cancer10 and parathyroid adenomas9 imaging, FCRs of respectively 7.0, 2.4 and 6.1 are reported. The FCR in pituitary surgery is thus relatively low, although su cient. In the future hopefully improved contrast agents and imaging systems could potentially further enhance the FCR in pituitary surgery as well.
Optimal timing of ICG administration is crucial to obtain optimal distinction between normal and abnormal tissue. In the current research protocol, the rst ICG administration was performed before opening of the dura. The vascularisation of the dura was thereby visualised, but no additional value for identi cation of the gland or the adenoma was obtained. In our experience, this rst gift of ICG was too early. It may help to assess changes in the vascularisation of the dura, suggesting invasive growth of the adenoma. However, we believe that the optimal timing of ICG administration is when the surgeon detects di erences in tissue colour and consistency, suggesting that the normal pituitary gland may be identi ed. The FCR was su cient to reliably di erentiate adenoma from normal gland. Interestingly, adenoma resection only under NIR uorescence guidance, e.g. without alternating between white and blue
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