In the process of tissue incision by laser energy, a boiling witch’s cauldron of chemical compounds is produced. Many of these compounds are transient: some pathways lead to products that are harmful to continuing efficient surgery and/or to the patient. It would be desirable to study the chemistry of active surgical incision sites as surgery progresses, altering wavelengths, pulse parameters and radiant intensities in effort to control chemical pathways and products for designing more efficient surgical techniques. Potential improvements may range from automated anatomical structure preservation, e.g., avoidance of a urinary sphincter, to cauterization of bleeding vessels and, ultimately to automated excision of diseased tissue while sparing healthy surrounds. Even laser lithotripsy might be better tailored to the target chemistry of kidney stones.

If fiber optic spectroscopy able to be performed within the same fibers that deliver the laser energy, whether using the surgical laser wavelength for fluorescence excitation or backscatter absorption or by adding a wavelength or even a spectrum, some degree of in situ qualitative and quantitative information is surely available. One might even attempt LIBS (laser induced breakdown spectroscopy). The construction of the optical fibers used in delivering the surgical power and those used in remote spectroscopy are essentially identical so the primary barrier to shared functionality has been the rapid degradation of the optical output surface in the turbulent surgical environment. Current kidney stone fiber tips are often destroyed within minutes of initiating surgery and side fire fibers used in prostate vaporization are usually “frosted” with devitrification within several minutes.

My most recent work has been dedicated to preserving the output surfaces of fiber optics for sustaining high optical performance throughout a surgical case and some of the results have been so successful that one can now image target tissue via the surgical fiber and preserve optical clarity for hundreds of thousands of joules in tissue contact, whether by efficient sloughing-off of devitrification layers or by harvesting latent heat for localized melting and re-vitrification is as yet undetermined, but the results have been reproduced in multiple rounds of bench tests with tissue phantoms (London Broil) as well as in prostate (BPH) surgery using a thulium fiber laser (TFL).

In prostate surgery the target gland lobes are at right angles to the minimally invasive access lumen. The optical fiber is fed up the urethra until the prostate tissue is encountered as an obstruction emanating from the urethral wall distal to the bladder neck. The tip of the fiber is typically polished at the critical angle for total internal reflection, thus kicking the light off at nearly 90 degrees, into the prostate. A tiny quartz test tube protects the sharpened fiber tip. As you may imagine, considerable distortion occurs as the laser light exits cylindrical wall of the fiber and passes through the wall of the tiny test tube. The thesis for improvements enabling spectroscopy has been minimization of these distortions, first. That doing so has also preserved clarity is logical but admittedly unanticipated.