Kinetics of intraoperative fluorescence diagnosis of parathyroid glands

Abstract

Objective: Identification of parathyroid glands is often a challenge even for experienced surgeons. The feasibility and efficacy of fluorescence diagnosis for localization of parathyroids has already been proven in an experimental setting. In preparation for a clinical application of this technique in patients undergoing surgery for hyperparathyroidism, we evaluated the kinetics of fluorescence diagnosis. Design and methods: Fifty rats were randomized into eight groups with different photosensitization parameters using the photosensitizer aminolevulinic acid (ALA): a peritoneal lavage was performed with either 1.5 or 3.0% ALA solution and the induced photosensitization times varied from 0.5, 1 and 2 to 4 h. Under special fluorescence illumination, D-light, the exposed operative site with thyroid, parathyroid glands and neck muscles was examined. The identified parathyroid glands were studied according to fluorescence intensity by spectrometric measurement and compared with surrounding tissue.Results: Photosensitizer accumulation in parathyroid glands, indirectly measured by spectrometry, was up to 3.2 times higher than in thyroid and 2.6 times higher than in muscle tissue (2 h photosensitization with 3.0% ALA). Using 1.5% ALA, the optimum fluorescence intensity and ratio/contrast was slightly lower (parathyroid-to-thyroid ratio £ 3.0, parathyroid-to-muscle ratio £ 1.9) but was reached earlier (1 h) and hence considered as the parameter of choice for a clinical application. Conclusions: In future clinical application, intraoperative fluorescence diagnosis is expected to increase the ease of identification of atypically located or supernumeric glands. In combination with preoperative diagnostics, this may result in reduced operation time and avoidance of persistent hypercalcaemia.European Journal of Endocrinology 150 743-747

Fluorescence-guided minimally invasive parathyroidectomy: a novel detection technique for parathyroid glands

“…Fluorescence diagnosis using aminolevulinic acid (ALA) to identify parathyroid glands during bilateral neck exploration for hyperparathyroidism in an experimental setting has been described [6,16]. As an intermediate of heme biosynthesis, ALA is a naturally occurring substance and precursor of fluorescent protoporphyrin IX (PpIX), which can act as a photosensitizer.…”

Fluorescent Detection of Rat Parathyroid Glands via 5‐Aminolevulinic Acid

“…To our knowledge, only a single group has described the use of 5‐ALA for fluorescent detection of parathyroid tissue. Gahlen et al 18–20 have demonstrated fluorescent visualization of parathyroid glands in normal rats as well as a model simulating secondary hyperparathyroidism in rats genetically engineered to express polycystic kidney disease. In our experiments, significantly higher doses were required to observe parathyroid fluorescence 18,19 .…”

“…Gahlen et al 18–20 have demonstrated fluorescent visualization of parathyroid glands in normal rats as well as a model simulating secondary hyperparathyroidism in rats genetically engineered to express polycystic kidney disease. In our experiments, significantly higher doses were required to observe parathyroid fluorescence 18,19 . Zero animals in our trials had parathyroid tissue fluorescence detected at their published optimal doses of 50 mg/kg at 2 hours and 100 mg/kg at 4 hours.…”

“…In our experiments, significantly higher doses were required to observe parathyroid fluorescence. 18,19 Zero animals in our trials had parathyroid tissue fluorescence detected at their published optimal doses of 50 mg/kg at 2 hours and 100 mg/kg at 4 hours. Discrepancies between the 5-ALA dosage used in the current study and that used by Gahlen et al are most likely related to the difference in commercial source of the 5-ALA.…”

Intraoperative photodynamic detection of normal parathyroid glands using 5‐aminolevulinic acid

“…Fluorescence‐guided detection of normal parathyroid glands using 5‐aminolevulinic acid (5‐ALA) has been reported recently in rats 7–9. However, there are few reports of fluorescence‐guided localization of normal parathyroid glands in humans.…”