192 - MR Guided Catheter-Based Radiotherapy/Brachytherapy of Liver Tumours – First Experience and Feasibility

Purpose: To show feasibility and safety of MR guided catheter-based radiotherapy/brachytherapy of primary or secondary liver tumours

Materials and Methods: Between June 2023 and April 2024, a total of 27 patients with 54 liver lesions were treated within a prospective single-center trial on MR guided catheter-based radiotherapy (MR BRIGHT trial). Treatments were performed under conscious sedation and local anaesthesia, utilizing a 1.5T MRI system (Magnetom Solafit, Siemens Healthineers) with a 15 cm loop coil. Each procedure involved administering gadoxetic acid at 0.1 mmol/kg body weight for contrast enhancement, inserting an 18G coaxial needle (Co. ITP) and navigating to the lesion through real-time gradient-echo (TE 3.4ms, TR 7.3ms, FA 30°) fluoroscopy sequences (with iMRI UI Extension, Research Software Package), subsequently exchanging the needle over a nitinol wire for a 6F hydrophilic angiography sheath harbouring a 6F brachytherapy catheter. 3D T1-weighted sequences were sent to treatment planning system in the radiation department for Brachytherapy (BT) with IR192 high-dose-rate (HDR) afterloading unit. Target doses ranged from 15 to 25 Gray (Gy) depending on the tumour entity, including HCC (33.3%), CRC (22.2%), GIST (11%), NET (11.1%) and metastases from other primaries (22.2%). The catheters were removed after BT and the radiation tract was sealed with gelatine sponge.

Results: The average lesion diameter was 13 ± 6 mm, whereas the average clinical target volume (CTV) was 3.0 ± 2.9 cm³. The average room time was 74 ± 35 minutes, the average time for catheter placement was 19 ± 11 minutes. The mean dose administered per lesion (D100) was 18.9 ± 3.6 Gy. Complications during and after BT were generally rare with only 1 patient (3.7 %.) having a minor bleeding without need for blood transfusion or intervention.

Conclusion: Overall, MR-guided catheter-based radiotherapy for liver tumours is feasible and safe, particularly for small lesions. With low complication rates and precise dosimetry achieved through advanced imaging, this approach holds promise for effective tumour management.