Lokale Radiofrequenzablation von Leberherden - Möglichkeiten und Grenzen

Role of B-mode ultrasound screening in detection of local tumor recurrence in the first year after radiofrequency ablation in the liver

BACKGROUND

Ultrasound is known to be useful in imaging radiofrequency ablation (RFA) lesions intra- and postoperatively. The presented study intends to prove the value of ultrasound examination as a means of screening RFA-treated patients for local tumor recurrence.

PATIENTS AND METHODS

During a period of 47 months, 91 RFA treatments were performed in 61 patients in a single institution. Indications for RFA were hepatocellular carcinoma (74%), colorectal metastases (18%), recurrent cholangiocellular carcinoma (5%) and one neuroendocrine tumor metastasis as well as one metastasis of pancreatic cancer (1.5% each). RFA was only considered in non-resectable liver cancer. All applications were conducted under sonographic guidance following preoperative evaluation. Postoperative screening included sonographic examinations at intervals of 3, 6 and 12 months postoperatively, and further annual follow-up examinations. Mean follow-up period was 11.8 months.

RESULTS

Within the first 12 months after treatment, the lesions become more and more inhomogenous with mixed echogeneity. Occasionally, this evolves as a misleading finding, mimicking early tumor recurrence. To clarify suspicious cases (31%), magnetic resonance imaging (20%) or computed tomography (10%) was engaged. Ultrasound led to the detection of local tumor recurrence in 78% of recurrent HCC (13 patients), but only in 67% of metastatic diseases (3 patients). Overall local recurrence rate was 18%.

CONCLUSION

Ultrasound screening as a follow-up of primary hepatic malignancies is, due to its sensitivity, capable of detecting early local recurrence despite its low specifity. Appropriate application of particular criteria of local recurrence allows B-mode ultrasound to play a major role in screening RFA-treated patients.

Laser-induced thermotherapy for lung tissue—evaluation of two different internally cooled application systems for clinical use

Thermal ablation techniques like radiofrequency or laser-induced thermotherapy (LITT) are increasingly used to treat tumors of parenchymatous organs. Minimal access, parenchymal preservation, and a low complication rate render them suitable for pulmonary tumors as well. Their successful clinical application depends on the induction of sufficiently large lesions and a knowledge of the energy parameters required for complete thermal ablation. The aim of this study was to establish a dose-response relationship for a percutaneous and an intraoperative system for LITT of lung tissue. Thermal lesions were induced in healthy porcine lungs using an Nd:YAG laser (1,064 nm). LITT was performed with a percutaneous application system in group I (n = 18) and an intraoperative application system in group II (n = 90). Laser energy was applied for 600-1,200 s in a power range of 20-32 W (12,000-38,400 J). The lesions were longitudinally and transversally measured, and the volume was calculated after the intervention. Furthermore, an open application system was used to perform LITT under in vivo conditions during lung perfusion and ventilation in domestic pigs. Lesion volumes in both groups showed a plateau-like curve when the laser power increased from an initial level of 25 W. With the percutaneous puncture system (group I), the application of 28 W (16,800 J) for 10 min generated the largest lesions with a volume of 12.54 +/- 1.33 cm(3), an axial diameter of 39.33 +/- 2.52 mm, and a diametrical diameter of 24.67 +/- 1.15 mm. A longer application time was not possible due to thermal instability of the applicator. Moreover, group I started developing extensive carbonizations at a laser power of 22 W (13,200 J). The intraoperative application system (group II) achieved the largest lesion volumes of 11.03 +/- 2.54 cm(3) with diameters of 34.6 +/- 4.22 mm (axial) and 25.6 +/- 2.51 mm (diametrical) by an exposure time of 20 min and a power of 32 W (38,400 J). Here extensive carbonizations only started to occur at 28 W (33,600 J). Under in vivo conditions, all pigs tolerated the LITT procedure well without complications. Besides a typical cooling effect in the vicinity of blood vessels, the thermal lesions were about three times smaller than the ex vivo lesions. Both the percutaneous and the open LITT application system induced reproducible, clinically relevant lung lesions. The percutaneous puncture set generated large relevant lesions, although its usability is limited by its restricted capacity and high carbonization risk. It is suitable for powers up to 22 W. The intraoperative application system allows higher energy exposure to induce larger lesion volumes. This study elucidates the dose-effect relation of two clinically relevant puncture sets.