OBJECTIVE

Interstitial laser thermotherapy (ILT) of liver tumors is generally performed using neodyium yttrium-aluminium-garnet (Nd-YAG) lasers. More versatile diode units, developed predominantly for other clinical applications, may be equally suitable for ILT. This study compares the efficacy of diode and Nd-YAG lasers in achieving maximum tissue necrosis, at low power, in a murine model.

METHODS

Thermal ablation was induced in the liver of CBA strain mice by diode (980-nm wavelength) and Nd-YAG (1064-nm wavelength) lasers using 400-microm diameter bare fibers. Treatment time prior to tissue charring was determined for both lasers at a power output of 2 W. Tissue temperature was recorded upon completion of therapy 3 mm from the fiber insertion site. The maximum diameter of necrosis was accurately assessed by nicotinamide adenine dinucleotide (NADH) diaphorase tissue staining.

RESULTS

Maximum diameter of tissue necrosis prior to charring occurred at 20 s (40 J) with the diode laser compared to 50 s (100 J) with the Nd-YAG laser. The maximum diameter of necrosis (mean [SEM]) produced by the diode laser, 5.9 mm (0.14), was equivalent to the necrosis induced by the Nd-YAG laser, 5.9 mm (0.14) (p = 0.963). Tissue temperature 3 mm from the fiber application site immediately following ILT in the diode laser group, 40.8 degrees C (0.93), was not statistically different than that of the Nd-YAG laser group, 39.0 degrees C (0.86) (p = 0.452). Tissue charring consistently prevented treatment beyond 20 s at 2W by the diode laser.

CONCLUSION

Low power ILT with diode and Nd-YAG lasers achieves equivalent maximal necrosis when applied to the liver by a bare fiber. Treatment time to produce maximal necrosis is however significantly shorter with the diode laser.