C. T. Germer

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.

SigmadivertikulitisOperationsindikation und -zeitpunkt

ZusammenfassungBei der chirurgischen Therapie der Kolondivertikelkrankheit sind OP-Indikation und -zeitpunkt vom Stadium der Erkrankung abhängig. Daher ist eine prätherapeutische, klinisch-pragmatische Stadieneinteilung die Voraussetzung für eine stadienadaptierte Therapie. Darüber hinaus sind Kenntnisse über den Spontanverlauf der Erkrankung, den Verlauf nach konservativer und operativer Therapie sowie über die individuellen Risikofaktoren für die Entwicklung eines komplizierten Verlaufs notwendig, um die richtige Indikation zur OP zu stellen. Bei der blanden Divertikulose und der unkomplizierten Divertikulitis ist keine Operation indiziert, die akute komplizierte Divertikulitis dagegen ist eine generelle OP-Indikation. Entscheidend für das Stellen der OP-Indikation ist daher eine möglichst exakte prätherapeutische Differenzierung zwischen komplizierter und unkomplizierter Divertikulitis. In Abhängigkeit von der Komplikationsart und dem klinischen Bild ist der OP-Zeitpunkt für die akute komplizierte Divertikulitis notfallmäßig oder frühelektiv nach initial konservativer und/oder interventioneller Therapie festzulegen. Bei der chronisch-rezidivierenden Divertikulitis ist ebenfalls eine OP indiziert. Als OP-Zeitpunkt ist die elektive Intervalloperation nach dem zweiten entzündlichen Schub anzustreben. Risikogruppen wie z. B. immunsupprimierte Patienten sollten bereits nach dem ersten entzündlichen Schub operiert werden.AbstractIndication and time for surgery of diverticular disease are determined by the stage of the disease. Clinically pragmatic pretreatment staging is thus a prerequisite for stage-adapted therapy. The correct indication for surgery is also based on knowledge of the spontaneous disease course, its course after conservative and operative therapy and the individual risk factors for complicated diverticular disease. Surgery is not indicated for bland diverticulosis or uncomplicated diverticulitis. It is generally indicated, however, for acute complicated diverticulitis. Decisive in establishing the indication for surgery is therefore the precise pretherapeutic differentiation of complicated and uncomplicated diverticulitis. Depending on the type of complication and the clinical appearance, the time for surgery of acute complicated diverticulitis is fixed on an emergency or early elective basis following initial conservative and/or interventional therapy. Chronically recurrent diverticulitis is likewise an indication for surgery. In terms of timing, an elective interval operation is best after the second inflammatory episode but should already be performed after the first one in risk groups, e.g. immunosuppressed patients.

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).

Nonoperative ablation for liver metastases. Possibilities and limitations as a curative treatment

ZusammenfassungUnter dem Begriff der „nichtoperativen Ablation“ werden eine Reihe heterogener Techniken zur Behandlung von Lebermetastasen zusammengefasst, wie beispielsweise die Radiofrequenztherapie (RF), die laserinduzierte Thermotherapie (LITT) und die Kryotherapie. Bislang galten die Verfahren im Wesentlichen als palliative Therapieoptionen. Wesentliche limitierende Faktoren waren die Induktion klinisch relevanter Läsionsvolumina und das Fehlen von Langzeitstudien. Innerhalb der letzten Jahre werden mit neu entwickelten Applikationssystemen der RF und LITT bemerkenswerte Ergebnisse erzielt, und erste klinische Studien zeigen bei selektierten Patienten vergleichbare Daten mit denen der chirurgischen Resektion. Die vorliegende Arbeit soll eine Übersicht über Möglichkeiten und Grenzen der nichtoperativen Ablation in Bezug auf den Einsatz unter kurativer Intention geben, wobei ein besonderes Gewicht auf die histopathologischen Grundlagen hyperthermer Läsionen sowie den klinischen Ergebnissen in Hinblick auf die „R0-Ablation“ und das Langzeitüberleben gelegt wird.AbstractUnder the term “nonoperative ablation” are grouped a number of heterogeneous approaches for the treatment of liver metastases, including laser-induced thermotherapy (LITT), radio-frequency therapy (RF), and cryotherapy. In general these procedures had been intended only for palliative purposes. The establishment of clinically relevant lesion size and a lack of long-term survival data were regarded as main limitations to using them with curative intention. During the last years however, new application systems have demonstrated remarkable results in RF and LITT, and some clinical studies have shown long-term survival in selected patients comparable to that for hepatic resection. We review possibilities and limitations of nonoperative ablation procedures with curative intent, highlighting the histopathological bases of thermal ablation techniques and clinical aspects such as R0 ablation and long-term survival.

Laparoscopic gastrostomy according to Janeway

Abstract. Percutaneous endoscopic gastrostomy is not suitable for all patients requiring gastrostomies. Patients with endoscopically impassable tumors require a safe and effective alternative procedure for paraesophageal alimentation. We present the surgical technique and results of the laparoscopic gastrostomy according to Janeway. Using an endoscopic stapling device a gastric tube is created from a stomach fold, led out through the trocar site, and fixed to the skin in the left upper quadrant. Via an inserted catheter enteral alimentation can be performed intermittently since the gastrostoma is continent. Between July 1995 and November 1996 laparoscopic gastrostomy was performed in 15 patients (10 male, five female) with tumors in the pharynx or esophagus. Mean operation time was 35 min. One stoma necrosis developed; the other postoperative courses were complication-free. All gastrostomies were continent. Laparoscopic gastrostomy is easy to perform and involves minimal discomfort and complications for the patient.

Laserinduzierte Thermotherapie Technische Voraussetzungen zur Behandlung maligner Lebertumoren

Summary. Laser-induced thermotherapy is an in situ ablation method for the local treatment of liver tumors. The basic prerequisite for induction of adequate treatment volumes for clinical use was the development of a thermostable application system. In an ex vivo test series, the specially developed application system (diffuser tip) with 5760 J had a higher thermic loading capacity than the Ringmode applicator with 4200 J, thus enabling the induction of significantly larger lesions with a volume of 7.6 cm3. The results of a further in vivo test series demonstrated that the lesions were subject to a four-phase connective-tissue organization within a 6-month period. Furthermore, the same laser energy (4200 J) was associated with a significantly lower lesion volume of 2.5 cm3 in the in vivo than in the ex vivo test series. The influence of liver perfusion on the inducible lesion volume was examined in a further animal experimental study. By temporarily interrupting hepatic blood perfusion (Pringles maneuver) during laser application, the effective volume could be increased to 50.3 cm3 (P < 0.01) using an optical beam splitter. These results show that the technical prerequisites for reliable clinical application of laser-induced thermotherapy have been fulfilled.Zusammenfassung. Die laserinduzierte Thermotherapie (LITT) ist eine Form der In-situ-Ablationsmethode zur lokalen Behandlung von Lebertumoren. Eine Grundvoraussetzung zur Induktion ausreichend großer Behandlungsvolumina für den klinischen Einsatz war die Entwicklung thermostabiler Applikationssysteme. In einer Ex-vivo-Versuchsreihe zeigte ein eigens entwickeltes Applikationssystem (Diffuser-Tip) mit 5760 J im Vergleich zu dem Ringmode®-Applikator mit 4200 J eine höhere thermische Belastbarkeit, so daß signifikant größere Läsionen mit einem Volumen von 7,6 cm3 induziert werden konnten. Die Ergebnisse einer weiterführenden In-vivo-Versuchsreihe demonstrierten, daß die Läsionen in einem Zeitraum von 6 Monaten, einer in 4 Phasen verlaufenden bindegewebigen Organisation unterlagen. Darüber hinaus resultierten in der In-vivo-Versuchsreihe bei gleicher Laserenergie (4200 J) mit 2,5 cm3 signifikant geringere Läsionsvolumina als in der Ex-vivo-Studie. In einer weiteren tierexperimentellen Studie wurde der Einfluß der Leberperfusion auf das induzierbare Läsionsvolumen untersucht. Durch die temporäre Unterbrechung der hepatischen Blutperfusion (Pringle-Manöver) während der Laserapplikation war bei Verwendung eines optischen Strahlteilers eine Vergrößerung des Wirkvolumens auf 50,3 cm3 (p < 0,01) erzielbar. Diese Daten zeigen, daß die technischen Voraussetzungen zur Induktion ausreichend großer Läsionsvolumina für die Behandlung humaner Lebermetastasen mit der LITT geschaffen wurden.