Laser‐induced thermotherapy (LITT) of liver metastases: MR‐guided percutaneous insertion of an MRI‐compatible irrigated microcatheter system using a closed high‐field unit

Abstract

Purpose:To evaluate the efficacy and safety of a new MRIcompatible irrigated laser microcatheter system for thermal ablation of liver metastases. Material and Methods:The new microcatheter system consists of a titanium needle with a diameter of 1.5 mm and a surrounding Teflon catheter with an outer diameter of 1.8 mm (5.5 F). In vitro laser-induced coagulation of bovine liver tissue was performed to determine the optimal perfusion rate of cooling saline flow, maximum laser energy, and ablation time. Laser-induced thermotherapy using the new microcatheter system, an Nd:YAG laser (Dornier), and a flexible laser light guide (Somatex GmbH, Berlin, Germany) was performed in 28 patients with liver metastases. Percutaneous insertion and positioning of multiple microcatheters in the lesion and monitoring of therapy was performed with a closed high-field MRI scanner using T1-weighted gradient-echo sequences during breath-hold. Results:A perfusion rate of 0.75 mL/minute, a laser energy of 15 W, and an ablation time of 20 minutes were found suitable to achieve safe and sufficient ablation of metastatic tissue. The mean volume of induced coagulation in vitro was 23.9 mL. Ablation of liver metastases in patients was technically and clinically successful. Conclusion:The new microcatheter system allows for both catheter placement and monitoring of therapy using a single imaging modality. This shortens the procedure and enables more precise puncture and therapy of liver metastases. Due to the miniaturized design of the catheter and the real-time monitoring, the procedure is minimally invasive and very well tolerated by patients. This new technique seems to be a safe and feasible alternative in treating liver metastases.

Automatic temperature control for MR-guided interstitial ultrasound ablation in liver using a percutaneous applicator: Ex vivo and in vivo initial studies

“…Thus, a delay from 1 to 2 months after the procedure is usually recommended to perform contrast-enhanced CT examination for assessment of ablative lesions (4). Although MR contrast is usually better in the liver (5)(6)(7), accurate analysis of the ablative lesion also requires a delayed contrast-enhanced examination.…”

Laser-induced thermotherapy (LITT)—evaluation of a miniaturised applicator and implementation in a 1.0-T high-field open MRI applying a porcine liver model

“…Hosten and Puls et al used an open 5.5-F Teflon microcatheter system (Monocath®) on lung and liver tumours [6,7]. Puls et al described ex-vivo volumes of necroses of up to 23.9 cm 3 with an effective output of 15 W/20 min (18 kJ) and a flow rate of cooling agent of 0.75 ml/min [7].…”

“…The feasibility of monitoring LITT with online thermometry in conventional MRI systems has been described in previous studies [1,[7][8][9], as laser fibres and catheter systems do not interfere with the MR signal. In most cases, applicator positioning was guided with CT imaging [1,10].…”

“…In principle, the miniaturisation of the applicator systems plays a key role in the continuous improvement of ablative techniques [5] and may facilitate a less traumatic approach to the specific tumour site. A 5.5-French microcatheter with an open irrigation system has been proposed for the treatment of lung and liver metastases [6,7].…”

MR-guided liver tumor ablation employing open high-field 1.0T MRI for image-guided brachytherapy

“…Other groups have tested closed bore high-field MRI for image-guided needle placement. However, in these systems access to the patient is severely limited and needle repositioning has to be performed outside of the magnet with intermittent acquisition of images [16]. Finally, open low-field MRI has been tested for MR fluoroscopy in liver intervention, but image quality has never been acceptable, and these interventions have not translated into routine clinical use [17][18][19][20].…”