Comparative assessment of near-infrared autofluorescence imaging in porcine and human adrenalectomy specimens

Abstract

Background: Near-infrared autofluorescence (NIRAF) imaging has shown promising results in neck endocrine surgery, and can also be used for image guidance in adrenal surgery. The aim of this study was to investigate the near-infrared autofluorescence characteristics of healthy and neoplastic adrenal tissues in porcine and human specimens.

Methods: Porcine adrenalectomy specimens were collected in compliance with national ethical regulations, and human adrenalectomy specimens within the retrospective observational study were handled according to institutional standards of care. Near-infrared autofluorescence signals acquired with a commercial fluorescence imaging device were quantitatively analyzed and compared between specimens by use of a standardized indocyanine green reference card.

Results: Normal porcine specimens (n = 10) had a mean adrenal-to-reference card near-infrared autofluorescence ratio like normal human cortex (0.41 ± 0.17 vs 0.51 ± 0.23; P = ns). In the 21 human adrenalectomy specimens, normal adrenal cortex had a significantly higher mean tissue-to-reference card near-infrared autofluorescence ratio than neoplasia (0.50 ± 0.24 vs 0.29 ± 0.21, P = .02) and no significant difference to adenomas. Differentiated adrenocortical tissue exhibited the strongest autofluorescence, contrasting with nonfluorescent medulla, malignant, or adipose tissue. Autofluorescence effectively highlighted subsurface adrenocortical tissue, undistinguishable by white light inspection, and post-specimen removal near-infrared autofluorescence imaging had no impact on operating time.

Conclusions: Because normal porcine and human adrenal tissue have similar autofluorescence properties, this discovery could be useful for identification of the relevant molecule. Near-infrared autofluorescence imaging shows potential for intraoperative image guidance in preoperatively indeterminate lesions and cortical-sparing approaches, and aids in identification of benign adrenocortical tissue and lesion margins. However, current evidence is insufficient to classify indeterminate lesions solely based on autofluorescence.