Invited Commentary
August 2, 2023
Magic Pen?—An Innovative Adjunct for Intraoperative Identification of Parathyroid Glands
Michelle B. Mulder, Quan-Yang Duh
JAMA Surg. Published online August 2, 2023. doi:10.1001/jamasurg.2023.3257
DeHoog et al1 introduce the MasSpec Pen (MSPen), a new technology that uses real-time mass spectroscopy for intraoperative parathyroid identification. This device is able to distinguish among parathyroid, thyroid, and lymphatic tissue by analyzing metabolic constituents, extracted following tissue contact with a droplet of sterile water, to determine tissue origin.
Other techniques and technologies have been used to facilitate identification and preservation of parathyroid glands during thyroid and parathyroid operations.2-4 Usually, the surgeon can visually identify parathyroid glands by their characteristic appearance, helped by knowledge of anatomical landmarks and embryology. However, patient-specific limitations, prior operations, ectopic locations, and concomitant pathology can complicate visual identification even for experienced surgeons. Various adjuncts have thus been proposed to help identify parathyroid glands intraoperatively, but each has its limitations.
Parathyroid tissue can be confirmed intraoperatively by frozen section, or measuring parathyroid hormone on tissue aspirate, but these methods are time consuming, resource intensive, and sacrifice valuable tissue.3 Parathyroid glands can be identified visually by intravenous injection of dyes, such as methylene blue, 5-aminolevulinic acid, and indocyanine green, but they can have adverse systemic effects (including neurotoxicity with methylene blue and phototoxicity with 5-aminolevulinic acid), and parathyroid glands can be obscured if the contrast extravasates.3,4
Optical technologies using near infrared autofluorescence can be probe-based (eg, PTeye, [AiBiomed]) or image-based (eg, Fluobeam, [Fluoptics]) and are noninvasive, safe, and US Food and Drug Administration approved.2However, they can have false positives (eg, with brown fat or colloid) and false negatives (eg, limited depth of penetration).2,4
Other optical technologies, such as dynamic optical contrast imaging (which measures the rate of fluorescent decay to identify parathyroids by wavelength), optical coherence tomography (high-resolution reconstruction of the tissue microarchitecture in 3-dimensional imaging via low-coherence interferometry), and Raman spectroscopy (chemical composition of tissues determined by the molecular energy created from the inelastic scattering of monochromatic light) have shown promise in tissue differentiation.2,4,5 However, the applications are limited, as the results are restricted to ex vivo analysis (dynamic optical contrast imaging and Raman spectroscopy) or failed replication in vivo (optical coherence tomography).4-6
Measurements of parathyroid gland perfusion and vascularity, while unavailable in the MSPen, can be measured by indocyanine green angiography, laser doppler flowmetry, and laser speckle contrast imaging (interference pattern created from reflected light creates a speckle pattern that, when dynamic, indicates vascular flow). However, laser speckle contrast imaging is limited by motion artifacts.4,7
The MSPen is an innovative and promising device for intraoperative parathyroid identification. Additional technological enhancement, multicenter validation, and analysis of cost-effectiveness is necessary before routine use by endocrine and head and neck surgeons. As we appreciate these clinical innovations, it is essential to recognize that no amount of technology can replace the fundamental surgical knowledge and judgment of an expert surgeon required for successful surgical outcomes.
