Enhancing Parathyroid Gland Visualization Using a Near Infrared Fluorescence-Based Overlay Imaging System

Abstract

Background: Misidentifying parathyroid glands (PGs) during thyroidectomies or parathyroidectomies, could significantly increase post-operative morbidity. Imaging systems based on near-infrared autofluorescence (NIRAF) detection can localize PGs with high accuracy. These devices however depict NIRAF images on remote display monitors, where images lack spatial context and comparability with actual surgical field-of-view (FOV). In this study, we designed an Overlay Tissue Imaging System (OTIS) that detects tissue NIRAF and back-projects the collected signal as a visible image directly onto the surgical FOV instead of a display monitor, and tested its ability for enhancing parathyroid visualization. Study Design:The OTIS was first calibrated with a fluorescent ink grid and initially tested with parathyroid, thyroid and lymph node tissues ex vivo. For in vivo measurements, the surgeon's opinion on tissue-of-interest was first ascertained. After the surgeon looked away, the OTIS backprojected visible green light directly onto the tissue-of-interest, only if the device detected relatively high NIRAF as observed in PGs. System accuracy was determined by correlating NIRAF projection with surgeon's visual confirmation for in-situ PGs or histopathology report for excised PGs.Results: OTIS yielded 100% accuracy when tested ex vivo with parathyroid, thyroid and lymph node specimens. Subsequently, the device was evaluated in 30 patients who underwent thyroidectomy and/or parathyroidectomy. 97% of exposed tissue-of-interest were visualized correctly as PGs by the OTIS without requiring display monitors or contrast agents.

Preoperative and Intraoperative Methods of Parathyroid Gland Localization and the Diagnosis of Parathyroid Adenomas

“…The strong green light marks PGs and supports the surgeon's visual interpretation. This method excludes the need of looking at external monitors and issues related to the inappropriate interpretation of images from the screen [15]. To best of our knowledge, only one study focused on the identification of primary hyperparathyroidism with NIR.…”

“…Postoperative studies regarding hypocalcemia as a result of surgical procedures showed that transient hypocalcemia is observed in 27% of patients who underwent thyroidectomy, while permanent in 1% of cases [14]. Similarly, the risk of reoperation after incomplete removal of PGs during parathyroidectomies can reach even up to 30% (an upper limit); however, as it is affected by numerous factors, some centers report the risk to be relatively low (<5%) [15][16][17].…”

Recent Advances and the Potential for Clinical Use of Autofluorescence Detection of Extra-Ophthalmic Tissues

“…Several research groups tried to overcome this disruption to surgical routines by introducing specially designed devices. McWade et al reported on the Overlay Tissue Imaging System (OTIS), which back-projects the collected AF signal in real time in the surgical field-of-view [112]. Thomas et al designed the now commercially available PTeye device (AiBiomed Corp., Santa Barbara, CA, USA), a handheld fiber-optic probe that gives auditory feedback when in contact with suspected PTG tissue [113].…”

“…Benmiloud et al quantified the duration of the operations, which was significantly longer in the NIR AFI group compared to the standard-care group (eight minutes between median values of both groups) [111]. Several attempts at intraoperative real-time monitoring of PTGs without delaying the operation were developed, and may even allow optimization of operation times without waiving intraoperative NIR AFI PTG detection [112,113,115,143]. A second limitation is that, foremost, only inexperienced surgeons profit from the intraoperative AFI guidance, requiring a case-to-case decision of whether or not to use intraoperative NIR AFI.…”

Imaging methods of the parathyroid glands in primary hyperparathyroidism. Literature review

“…В эндокринной хирургии метод может быть полезен для хирургии ЩЖ и ОЩЖ, за счет физиологических аутофлюоресцентных свойств ОЩЖ при использовании лазера с длиной волны ~785 Нм в условиях выключенного света в операционной изображение детектируется с помощью обычной камеры с фильтром для флуоресценции 830-870 Нм, оборудованной дополнительно белым светом (3000К). Неинвазивный и простой метод, позволяющий достаточно эффективно локализовать околощитовидные железы в операционном поле, по некоторым данным, чувствительность и специфичность могут достигать 95-100% [107][108][109][110][111] (рис. 12.1 и 12.2).…”