Intraoperative fluorescence visualization of the parathyroid gland in rats

Bilateral neck exploration is the standard procedure of primary hyperparath yroidism. Preoperative localization is not mandatory. Intraoperative visual ization methods help to avoid unsuccessful explorations and to reduce morbi dity rates. In our study, the application of 5-Aminolevulinic acid (5-ALA), a precursor in the heme biosynthesis pathway, led to Protoporphyrin IX (Pp IX) accumulation within the parathyroid gland (PTG). PpIX, a metabolite of 5-ALA, causes red fluorescence (635 nm) when stimulated by light of a defin ed wavelength. Largely invisible under conventional illumination, all PTGs were fluorescence positive and detectable after PpIX targeting and blue lig ht excitation (380-440 nm). Point spectrometry to measure fluorescence inte nsities, showed a fluorescence ratio between PTG and surrounding thyroid gl and tissue of 5.7 : 1 (p <0.001). Fluorescence guided PTG biopsies showed n o 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 parathy roidectomy will be facilitated by this innovative technique.