Water‐jet‐cooled Nd:YAG laser coagulation of experimental liver metastases: Correlation between ultrasonography and histology

Abstract

To establish the value of ultrasonography in imaging laser coagulation of tumor and surrounding tissue, the relation between measurements on ultrasound and histology was determined in a rat tumor model. A piece of colon carcinoma CC531 was implanted in the liver of 21 Wag/Rij rats; 20 days later, tumors (mean diameter 5.3 mm) were treated with a water-jet-cooled Nd:YAG laser at 10 W and either 150 J, 300 J, 600 J, 1,200 J, 1,700 J, or 2,400 J. Ultrasonography was done just pre- and immediately post-laser treatment. The animals were sacrificed and livers removed for light microscopical evaluation. Depth and width of coagulation were measured directly on ultrasound, and on histological samples by computer-assisted image analysis. Laser treatment did not change the echogenic aspect of the tumor on ultrasound. However, liver damage appeared hypoechoic compared to normal liver. A significant correlation was found between the total size of the lesion on ultrasound and histology (P = 0.015, r = 0.57 for depth; P = 0.012, r = 0.58 for width), suggesting that laser induced tumor destruction may be derived from the amount of surrounding hepatic damage on ultrasound.

Efficacy of Direct Electrical Current Therapy and Laser-Induced Interstitial Thermotherapy in Local Treatment of Hepatic Colorectal Metastases: An Experimental Model in the Rat

“…According to van Hillegersberg et al [71], we considered them as vital, because even though they showed signs of cell death with a shrunken, smaller, more intensively colored cell nucleus, and an indistinct cell membranecytoplasm border, they were not cleared in the inflammation reaction by macrophages. Neither did they demonstrate any signs of apoptosis.…”

Mechanisms of Focal Heat Destruction of Liver Tumors

“…Paradoxically, carbonization limits the extent of tissue injury by creating a heat trap [34]. This carbonization also increases tissue interstitial pressures and may result in dissemination of cancer cells deep into the liver and blood vessels [31].…”

“…Classical hyperthermia relies on a temperature of 42°C to 45°C for periods of 30 to 60 min to cause irreversible cellular damage [27][28][29][30]. The inactivation of vital enzymes is a key feature of tissue injury at these temperatures [31]. As the tissue temperature rises to 60°C, the time required to achieve irreversible cellular damage decreases exponentially.…”

Interstitial laser thermotherapy in the treatment of colorectal liver metastases

“…Gas bubble production is seen in most cases in close proximity to the ®bre tip [66±68]. A number of animal studies have found good correlation between ultrasonographic ®ndings and histological assessment [66,67,69]. Malone and colleagues, however, reported that ultrasonography consistently overestimated the size of the thermal lesion in the early phase and late scans tended to underestimate the size of the lesions.…”