title: Monitoring of tumor radio frequency ablation using derivative spectroscopy.
abstract: Despite the widespread use of radio frequency (RF) ablation, an effective way to assess thermal tissue damage during and after the procedure is still lacking. We present a method for monitoring RF ablation efficacy based on thermally induced methemoglobin as a marker for full tissue ablation. Diffuse reflectance (DR) spectra were measured from human blood samples during gradual heating of the samples from 37 to 60, 70, and 85°C. Additionally, reflectance spectra were recorded real-time during RF ablation of human liver tissue ex vivo and in vivo. Specific spectral characteristics of methemoglobin were extracted from the spectral slopes using a custom optical ablation ratio. Thermal coagulation of blood caused significant changes in the spectral slopes, which is thought to be caused by the formation of methemoglobin. The time course of these changes was clearly dependent on the heating temperature. RF ablation of liver tissue essentially led to similar spectral alterations. In vivo DR measurements confirmed that the method could be used to assess the degree of thermal damage during RF ablation and long after the tissue cooled.
authors.affiliation: The Netherlands Cancer Institute, Department of Surgery, Plesmanlaan 121, Amsterdam 1066CX, The Netherlands.
authors.forename: Jarich W
authors.initials: JW
authors.lastname: Spliethoff
authors.affiliation: The Netherlands Cancer Institute, Department of Surgery, Plesmanlaan 121, Amsterdam 1066CX, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Tanis
authors.affiliation: The Netherlands Cancer Institute, Department of Surgery, Plesmanlaan 121, Amsterdam 1066CX, The Netherlands.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Evers
authors.affiliation: Minimally Invasive Healthcare, Philips Research, High Tech Campus 34, Eindhoven 5656 AE, The Netherlands.
authors.forename: Benno H W
authors.initials: BH
authors.lastname: Hendriks
authors.affiliation: The Netherlands Cancer Institute, Department of Radiology, Plesmanlaan 121, Amsterdam 1066CX, The Netherlands.
authors.forename: Warner
authors.initials: W
authors.lastname: Prevoo
authors.affiliation: The Netherlands Cancer Institute, Department of Surgery, Plesmanlaan 121, Amsterdam 1066CX, The NetherlandsdUniversity of Twente, MIRA Institute, Building Zuidhorst P.O. Box 217, Enschede 7500 AE, The Netherlands.
authors.forename: Theo J M
authors.initials: TJ
authors.lastname: Ruers
mesh_terms: D001777:Blood Coagulation; D017115:Catheter Ablation / Q000009:adverse effects*; D006454:Hemoglobins / Q000032:analysis / Q000737:chemistry; D006801:Humans; D008099:Liver / Q000293:injuries / Q000528:radiation effects / Q000601:surgery; D008113:Liver Neoplasms / Q000601:surgery*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D006454:Hemoglobins