Intraoperative Fluorescence Visualization of the Parathyroid Gland in Rats

Bilateral neck exploration is the standard procedure of primary hyperparathyroidism. Preoperative localization is not mandatory. Intraoperative visualization methods help to avoid unsuccessful explorations and to reduce morbidity rates. In our study, the application of 5-Aminolevulinic acid (5-ALA), a precursor in the heme biosynthesis pathway, led to Protoporphyrin IX (PpIX) accumulation within the parathyroid gland (PTG). PpIX, a metabolite of 5-ALA, causes red fluorescence (635 nm) when stimulated by light of a defined wavelength. Largely invisible under conventional illumination, all PTGs were fluorescence positive and detectable after PpIX targeting and blue light excitation (380-440 nm). Point spectrometry to measure fluorescence intensities, showed a fluorescence ratio between PTG and surrounding thyroid gland tissue of 5.7:1 (p < 0.001). Fluorescence guided PTG biopsies showed no false positive findings in histology. 5-ALA induced PpIX fluorescence to detect PTGs suggests to be a highly sensitive intraoperative visualization method. Hence, the performance of minimally invasive video-assisted parathyroidectomy will be facilitated by this innovative technique.