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To quantify the cooling effect of hepatic vessels on liver radiofrequency (RF) ablation ex situ. Bipolar RF applicators (diameter = 1.8 mm, electrode length = 30 mm) were inserted parallel to perfused glass tubes (diameter = 5 and 10 mm; flow = 250–1,800 ml/min) at distances of 5 and 10 mm in porcine livers ex vivo. RF ablation was performed at 30 W/15 kJ. RF lesions were analyzed by measuring the maximum (r max) and minimum radius (r min) and the lesion area. Glass tubes without flow showed no influence on RF lesions, whereas perfused glass tubes had a significant cooling effect on lesions. r min was reduced to 50% at 5 mm applicator-to-vessel distance and the lesion area was reduced from 407 to 321 mm2 (p

PURPOSE: To assess the effect of laser-induced thermotherapy (LITT) on liver metastases of various size from colon carcinoma in an animal model. MATERIALS AND METHODS: Liver metastases were implanted in 20 Wistar Albino Glaxo (WAG) rats by subcapsular injection of cells from a colorectal strain (CC531) (day 0). The animals were divided into two groups with regard to the measured tumor size of 0.05 - 0.06 cm (3) (group A) and 0.10 - 0.12 cm (3) (group B). On day 14 after laparotomy, the tumors were exposed to 1064 nm Nd:YAG laser light at 2 watts for 5 minutes after intratumoral placement of the laser applicator set. The tumor volumes before (V1, at day 13) and after treatment (V2, at day 28) were determined by MRI and the mean tumor growth ratio (V2/V1) was calculated. RESULTS: The mean tumor volumes V1 and V2 were 0.05 +/- 0.003 cm (3) and 0.23 +/- 0.016 cm (3) in group A, and 0.11 +/- 0.006 cm (3) and 0.68 +/- 0.037 cm (3) in group B. The mean tumor growth ratio (V2/V1) was 4.31 +/- 0.19 in group A and 6.11 +/- 0.14 in group B. The mean volume of the induced necrosis (0.15 +/- 0.01 cm (3)) was the same for both groups ( p > 0.05). Compared to group B, liver metastases of group A showed a significant slower tumor growth velocity (paired t-test, p < 0.0001). CONCLUSION: The interventional treatment of large hepatic tumors with LITT leads to faster tumor growth compared to smaller lesions.

To evaluate experimentally and clinically an internally cooled power laser system for percutaneous treatment of liver metastases, with magnetic resonance (MR) imaging guidance, to increase the volume of coagulative necrosis with single laser beam applications.The power laser system consisted of standard cannulation paraphernalia and a specially designed 7-F protective catheter for cooling the laser tip during treatment to avoid carbonization. A microdome laser beam applicator with a laser tip diameter of 0.95 mm kept the entire device as small as possible. After the unit was tested in 40 porcine livers, 532 laser beam applications (mean power, 27.5 W [range, 22.1-30.0 W]; mean application time, 19.8 minutes [range, 14-30 minutes]) were performed with MR guidance in 127 patients with 318 liver metastases. The safety of the procedure and the volume of induced necrosis were evaluated.In vitro, cuboid areas of coagulative necrosis with a mean greatest diameter of 4.3 cm +/- 0.5 (SD) were demonstrated after single applications. In vivo, MR thermometry allowed accurate demarcation of changes induced by heat, with a mean diameter of necrosis of 3.3 cm +/- 1.4. No carbonization or vaporization of tissue or damage of equipment occurred during treatment.This power laser system can increase the volume of laser-induced necrosis in liver metastases with a single application, thereby simplifying and accelerating the treatment of larger lesions.

A case of subperiosteal temporal abscess of otitic origin is presented. This is an unusual complication of otitis media. The pathogenesis of Luc's abscess is different from other extracranial complications of middle-ear infections in that it is notassociated with mastoid infection which results in subperiosteal pus formation. Based on our experience and the reports from the turn of the century. we present the presumptive pathogenesis and clinical features. We contend that these patients run an unexpectedly benign course, and require concomitantly more conservative treatment than other otitic abscesses.

The laser is a well established surgical instrument in lung therapy. This report provides information on the biophysical basics of the laser-induced thermotherapy (LITT) of lung metastases. Optical properties like absorption and scattering determine the penetration depth of laser radiation in tissue. These parameters vary dynamically during the application and define in combination with thermal tissue properties the achievable destruction volume. Parenchyma behaves very differently compared to more dense tissues due to local inhomogenities and the large amount cavaties filled with air. Beside an account of the affecting parameters an overview of therapy options is given. Therapeutic results depend not only on the tissue properties but also on the technical equipment, e.g. the applicator design and the energy applied. Complex dosimetric models allow for a calculation of the lesion's size in advance.

Introduction The goal of this study was to compare the optical properties (o.p.) of colorectal primary tumors with that of synchronous hepatic metastases to ascertain whether the o.p of the primary tumor can be used to determine suitable application parameters and dosimetry for metastases.

Stimulated emission is an amplification process for photons, e.g. light (see Chap. 1-1). Depending on the output wavelength, its technical manifestation is a laser (light amplification by stimulated emission of radiation) or a maser (microwave amplification by stimulated emission of radiation) or a graser (gamma ray amplification by stimulated emission of radiation).