C. Isbert

Optical Properties of Native and Coagulated Human Liver Tissue and Liver Metastases in the Near Infrared Range

Knowledge about optical parameters and the resultant light distribution in laser‐treated tissue is important for predicting the effects of laser‐induced thermotherapy of liver metastases (LITT).

Interstitial laser coagulation: Evaluation of the effect of normal liver blood perfusion and the application mode on lesion size

The effect of temporarily interrupted hepatic blood flow and multiple‐fiber application on necrosis volume in interstitial laser coagulation (ILC) was investigated.

Laser-induced thermotherapy for the treatment of liver metastasis: Correlation of gadolinium-DTPA-enhanced MRI with histomorphologic findings to determine criteria for follow-up monitoring

AbstractPurpose: To evaluate gadolinium (Gd)-diethylenetriamine-pentaacetic-acid (DTPA)-enhanced magnetic resonance imaging (MRI) for follow-up monitoring of laser-induced thermotherapy (LITT) and to determine a useful examination schedule. Methods: LITT of the liver was performed in 55 rabbits using a neodymium: yttrium-aluminum-garnet (Nd:YAG) laser (4-W power output, 840-s exposure time). Gd-DTPA MRI and histologic examinations were performed at different times (0–168 days). Results: Laser-induced lesions underwent regeneration and volume size reduction (69% after 168 days). The correlation coefficient (MR vs. macroscopic analysis) for the mean lesion diameter was r= 0.96. Histology of lesions comprised the four zones that correlated best with MRI findings. Coagulation necroses immediately after LITT was seen as an area of no enhancement on Gd-DTPA MRI. Circular enhancement was first seen 72–96 h after LITT, which was due to early mesenchymal proliferation. Conclusions: Gd-DTPA MRI is a good monitoring procedure for LITT. MRI should be performed 24 and 96 h after LITT.

Radiation Planning for Thermal Laser Treatment

Summary A dosimetry model was developed for the thermal laser treatment of biological tissue and applied to laser-induced thermotherapy of organ tumors. This model combines a Monte Carlo simulation for calculating photon distribution in the target volume, a finite difference method for computing heat dissipation and the Arrhenius formalism for predicting protein denaturation and subsequent tissue damage. Implementation was carried out on a Windows-based platform and enabled the three-dimensional control of the target volume. An in vitro evaluation in porcine liver revealed a difference of less than 7% with regard to the ablation volume.

Diffusing Fibre Tip for the Minimally Invasive Treatment of Liver Tumours by Interstitial Laser Coagulation (ILC): An Experimental Ex Vivo Study.

Abstract. A newly developed diffusing laser applicator was examined for interstitial laser coagulation (ILC) of liver tumours. The applicator consisted of a matted quartz core and a quartz glass dome, also matted on its inner surface and sealed to the fibre. The applicator provided a homogeneous light intensity distribution over an active length of about 20 mm. Lesions were created in an ex-vivo porcine liver model using a Nd-YAG laser comparing the new diffusing tip with a Ringmode®-ITT applicator in order to find optimal laser parameters and damage thresholds. The lesions were investigated using macroscopic size measurement, volume calculation and histological examination (H&E, NADPH-dehydrogenase). The damage threshold of the diffusing tip was 6 W at 14 min exposure time whereas the Ringmode®-ITT applicator had its limit at 5 W and 12 min exposure. Comparing various exposure times showed that treatment over a time of more than 840 s did not significantly increase the lesion volume. At 5 W and 720 s the mean lesion volume was 6.9±1.1 cm3 with the diffusing tip and 6.3±0.6 cm3 with the Ringmode®-ITT applicator, both having a slight ellipsoidal shape. Hence, the created lesions were not significantly different for both applicators when the same laser parameters were applied. On the other hand, the new diffusing tip had a higher damage threshold and was therefore capable of producing maximal coagulation volumes of up to 7.9±0.5 cm3 at 5 W and 20 min. The experiments showed that lesions with a dimension of 31×22 mm can be achieved with the diffusing applicator which seem suitably sized for treating small human liver metastases in a single laser session.

Laser-induced thermotherapy: intra- and extralesionary recurrence after incomplete destruction of experimental liver metastasis

Purpose: The aim of this study was to determine the energy (J/mm3 tumor volume) and temperature required for a complete laser-induced thermotherapy (LITT) of experimental liver tumors, and to find out causes and areas of local recurrence followed by incomplete treatment. Methods: In VX-2 tumor-bearing rabbits LITT was performed using neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (1064 nm) with a diffuser-tip applicator and a temperature feedback system. The animals were randomized into four groups (n = 20) that differed in the target temperature at the tumor border as follows: 45°C, 50°C, 55°C and 60°C. The target temperature was held for 10 min constant. Histologic examination (hematoxylin and eosin [H&E], nicotinamide adenine dinucleotide phosphate [NADPH]-dehydrogenase) was performed at 0 h, 24 h, 96 h, and 14 days after LITT. Results: The pretreatment tumor volume of 2191 ± 61 mm3 was the same for all groups (p > 0.05). Energy up to target temperature and total energy required, lesion size, and the rate of incomplete tumor ablation (recurrences) are listed below (ap < 0.05, Kruskal-Wallis test). Histologically, two forms of local recurrences could be differentiated intralesionary and extralesionary. Conclusions: To achieve complete in situ ablation under the given conditions, it is necessary to apply laser energy of 3 J/mm3 tumor volume. A minimum temperature of 60°C on the tumor border presumed an application of 10 min. Recurrence was found outside the coagulation zone (extralesionary) and in high vascularized areas within the coagulation zone (intralesionary).

Esophageal hypermotility associated with intramural pseudodiverticulosis. Primary esophageal disease or epiphenomena

Esophageal intramural pseudodiverticulosis is a very rare disease of unclear etiology. The clinical picture is characterized by progressive dysphagia. Because of its frequent association with alcohol abuse and subsequent weight loss, it must be differentiated reliably from esophageal carcinoma. The diagnosis is established by the characteristic detection of multiple intramural contrast accumulations in the barium esophagogram. Additional endoscopic and endosonographic confirmation and histological examination are required to exclude a malignant tumor. Moreover, associated diseases are almost always present and should also be diagnosed by pH-metry, cytology, and esophageal manometry. Good and long-lasting therapeutic success can be achieved by bouginage of the stenosis with concomitant treatment of the associated esophageal diseases. Based on two case reports of patients with this disease, we discuss the unusual association with esophageal hypermotility as well as the symptoms, clinical course, therapy, and pathogenesis of the disease.

Laser-induced thermotherapy (LITT) for the treatment of liver metastases: the correlation of Gd-DTPA-enhanced magnetic resonance imaging (MRI) and histomorphological findings in the chronic model

The purpose of the study was to evaluate Gd-DTPA-enhanced MRI for the follow-up of laser-induced thermotherapy (LITT) in the treatment of liver metastases. Interstitial laser-induced thermotherapy (LITT) was performed in 55 chinchilla bastard rabbits with a Nd:YAG laser and a specially developed diffuser tip applicator. The animals were examined at different times using MRI and histological methods. T1-weighted spin-echo sequences were made with gadolinium-DTPA and submitted to correlation analysis. The analysis yielded a good correlation (r equals 0.96) between the largest lesion diameters. Lesions showed discontinuous regeneration kinetics with a 41% volume reduction 1 month after LITT. MRI of the lesion directly after LITT showed a hyperintense transition zone. Following the application of intravenous contrast medium, transition zone enhancement was first seen 72 - 96 hours after LITT. Even after 6 months, the laser-induced lesion is visualized as a non-enhanced area. Lesion regeneration followed the principles of wound healing. It is concluded that gadolinium-DTPA- enhanced MRI yielded definitive criteria for the follow-up assessment of LITT.

Laser-induced thermotherapy (LITT): energy and temperature determination for complete in-situ ablation of liver metastasis

Purpose: The aim of this study was to determine the energy (J/mm3 tumor volume) and temperature required for a complete in-situ-ablation of experimental liver tumors. Methods: LITT was performed in VX-2 tumor-bearing rabbits using Nd-YAG-Laser (1064 nm) with a diffuser-tip applicator and a temperature feedback-system. The animals were randomized into 4 groups (n equals 20) that differed in the target temperature at the tumor border [45 degrees Celsius, 50 degrees Celsius, 55 degrees Celsius and 60 degrees Celsius]. Histological examination was done at 0 h, 24 h, 96 h and 14 days after LITT. Results: The pretreatment tumor volume of 2191 +/- 61 mm3 was the same for all groups (p > 0.05). Energy and temperature required and the rate of incomplete tumor-ablation (recurrences) are listed below (* equals p < 0.05, Kruskal-Wallis test. Conclusions: (1) To achieve complete in-situ-ablation under the given conditions, it is necessary to apply laser-energy of 3 J/mm3 tumor volume. (2) A minimum temperature of 60 degrees Celsius on the tumor border presumed an application of 10 minutes.

Die Optimierung der Laserinduzierten Thermotherapie zur Behandlung von Lebermetastasen colorectaler Carcinome, eine interdisziplinäre Aufgabe — Eine klinische Studie

Bei Patienten mit Lebermetastasen eines colorectalen Carcinoms wurde untersucht, ob mit der Laserinduzierten Thermotherapie (LITT) unter Verwendung einer computergestutzten Bestrahlungsplanung, eine lokale Tumorkontrolle erzielbar ist. In vollstandig hyperthermierten Tumoren war eine lokale Kontrolle des Tumorwachstums erzielbar. Eine Wertung der Methode in bezug auf einen prognostischen Gewinn fur die behandelten Patienten ist aufgrund des inhomogenen und kleinen Patientenkollektives (n = 20) bei der kurzen Nachbeobachtungszeit nicht moglich.