Diffuse Reflectance Spectroscopy During Experimental Radio Frequency Ablation

• The aim of the study was to investigate the spectral changes during heating and to estimate threshold temperatures for initiation of the thermal coagulation. A brain electrode with optical fibers was used to generate lesions in ex-vivo porcine white and gray matter as well as in fat and meat from pork chop. Radio frequency ablation (60 s, 48–90 °C, steps of 2-10 °C) was performed while simultaneous spectroscopy measurements were made in the range 490–900 nm.The optical signal recorded from porcine gray and white brain matter was unstable with the reflected light intensity fluctuating a lot. Nevertheless an abrupt increase in light intensity during coagulation in gray matter was found at 48 ± 6 °C (n = 21), probably indicating onset of coagulation. The reflected light intensity from white matter showed no consistent behavior during coagulation.The results for pork chop meat and fat were considerably more consistent. The reflected light intensity from pork chop meat stayed stable up to a mean temperature of 42.5 ± 3.5 °C (n = 11). Above this temperature it abruptly increased for all wavelengths. The reflected light intensity from pork chop fat dropped over all wavelengths immediately as the temperature increased and remained low as the fat cooled (n = 8).In conclusion diffuse reflectance spectroscopy appears to be suitable to detect onset of coagulation in muscle tissue and gray matter. The estimated initiation temperature of coagulation varied and was dependent on tissue type.

Nyckelord

Radio frequency ablation

diffuse reflectance spectroscopy

brain

muscle

fat

MEDICINE

MEDICIN

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