Laser lithotripsy of salivary stones: Correlation with physical and radiological parameters

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Abstract

Background and Objectives:

Sialolithiasis is a common disease of the major salivary glands. Owing to the variety of conservative and minimally invasive techniques, it is now possible to treat most cases of sialolithiasis without removal of the affected salivary gland. One treatment option is the endoscopic removal of the calculi. In cases of larger concretions, intraductal disintegration using laser-induced shock waves can be appropriate to allow endoscopic removal. In the present study, we investigated whether physical and radiological parameters of salivary stones can effectively predict the applicability of laser lithotripsy. Furthermore, we determined to what extent the applied laser energy resulted in tissue damage.

Study Design/Materials and Methods:

In addition to basic parameters like size and density, we analysed 47 salivary stones using fluorescence spectroscopy, infrared spectroscopy, Raman spectroscopy, and dual-energy computed tomography. Subsequent fragmentation of all stones was performed with a Ho:YAG laser in a near-contact manner. Fragmentation rates were calculated and correlated with the previously measured physical and radiological parameters. Finally, to test for tissue damage, we performed HE-histology of salivary duct mucosa treated with the same laser energy used for stone fragmentation.

Results:

Blue light excitation induced either green or red fluorescence emission. Dual-energy CT resulted in evidence of calcium-containing material. Infrared spectroscopy and Raman spectroscopy, both identified carbonate apatite as the main component of salivary stones. Disintegration into pieces smaller than 2 mm was possible in all cases. Fragmentation rates depended on the energy per pulse applied but not on any of the analysed physical and radiological parameters. In contrast to lithotripsy with 500 mJ per pulse, which was associated with no tissue damage, lithotripsy with 1,000 mJ per pulse resulted in damage of salivary duct mucosa. This suggests that the optimal laser energy for stone fragmentation is between 500 and 1,000 mJ per pulse.

Conclusion:

Laser lithotripsy using Ho:YAG laser is a highly efficient treatment, at least in vitro. All salivary stones could be disintegrated irrespective of their physical and radiological composition. Lasers Surg. Med. 47:342–349, 2015. © 2015 Wiley Periodicals, Inc.

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