RPS 609b - Experimental

Purpose:

To validate the algorithm within the radiation dose index monitoring software NEXO[DOSE]® (Bracco Injeneering SA, Lausanne). It provides the skin dose distribution in interventional radiology procedures.

Methods and materials:

To determine the skin dose distribution in interventional radiology procedures, the software uses exposure parameters taken from the radiation dose structured report and additional information specific to each angiographic system. To test the algorithm accuracy, GafChromic® XR-RV3 films, wrapped on a cylindrical PMMA phantom, were irradiated with different setups and two different angiographic systems. The film measurements were compared in terms of absolute dose and geometric accuracy, with the ones that the software calculated on the same cylindrical model.

Results:

The cumulative dose values estimated by the software are in correlation with the GafChromic® measurements (differences lower than 15%) within the regions of the higher dose, whereas we are more interested in assessing patient exposure. Concerning the geometric accuracy, the differences between the dose spatial distribution simulated and the measured ones are less than 3 mm (4%) in simple tests and 5 mm (5%) in setups closer to clinical practice. Moreover, similar results are obtained for the two different angiographic system vendors.

Conclusion:

In the tests performed, NEXO[DOSE]® provides an accurate estimate of skin dose similar to or better than those obtained by other software packages. The validation on cylindrical geometry phantom proved that the calculation can be extended to anthropomorphic geometry and can be used to simulate the patient skin dose.

Limitations:

The dose value discrepancies increase up to 33% in regions with lower doses because the software does not consider the out-of-field scatter contribution of the neighbouring fields.

Ethics committee approval

n/a

Funding:

No funding was received for this work.

Purpose:

Evaluation of the technical success and patient safety of high-power MR-guided microwave ablation using a wide-bore 1.5T MR system.

Methods and materials:

13 Patients (61.0 years ± 6.8 [standard deviation]) with 17 hepatic malignancies (6 hepatocellular carcinomas, 11 hepatic metastases) underwent MR-guided tumour ablation with a high-power, water-cooled microwave ablation system from 08/2018-09/2019. The mean tumour size was 13.7 mm ± 5.9 (range: 6-25 mm). Planning, applicator placement, therapy monitoring, and control imaging were carried out using a 1.5T MR system. Technical success and ablation zone diameters were assessed by contrast-enhanced post-ablative control MR imaging. The mean follow-up was 3.6 months ± 4.4 (range: 0-14 months).

Results:

Technical success was achieved in all lesions. Lesions were treated using 1.5 ± 0.5 applicator positions with an ablation power of 100W. The mean energy applied was 70,6kJ ± 31,4kJ per tumour (range: 18-120 kJ). The mean total duration of energy application was 11.7 min ± 5.2 (range: 3-20 min) per tumour. Ablation zone short-axis and long-axis diameters were 29.0 mm ± 6.9 (range: 19-41 mm) and 39.6 mm ± 7.8 (range: 28-58 mm), respectively. 3 patients developed new tumour manifestations in the untreated liver during initial follow-up. No complications were observed.

Conclusion:

MR-guided high-power microwave ablation provides safe and effective treatment of hepatic malignancies with short ablation durations.

Limitations:

The small study population and short follow-up due to the relatively short availability of the MR-conditional microwave ablation system.

Ethics committee approval

Institutional review board approval and patient informed consent were obtained for this prospective study.

Funding:

No funding was received for this work.

Purpose:

One limitation of mechanical thrombectomy (MT) is clot migration during the procedure. This might be caused by abruption of the trapped thrombus at the distal access catheter (DAC) tip during stent-retriever retraction due to the cylindrical shaped tip of the DAC. Aiming to solve this problem, this study evaluates the proof-of-concept of a new designed funnel-shaped tip in an experimental in vitro setting.

Methods and materials:

Two catheter models, one with a funnel-shaped tip and one with a cylindrical-shaped tip, were compared in an experimental setup. For MT, a self-made vessel model and thrombi generated from pig’s blood were used. MT was performed 20 times for each device using two different stent-retrievers, 10 times respectively

Results:

For the funnel-shaped model, MT was successful with both stent-retrievers (Trevo XP ProVue 3/20 mm; Trevo XP ProVue 4/20 mm) at the first pass in 9/10 times (90%), respectively. For the cylindrical-shaped model, MTs were successful at the first pass with the smaller stent-retriever 5/10 (50 %) and 6/10 (60%) for the larger stent-retriever.

Conclusion:

The in vitro experiments show a better recanalisation rate for the funnel-shaped tip compared to the cylindrical-shaped tip. Further studies are needed to verify the safety and efficacy of the proposed funnel-shaped tip.

Limitations:

A single in vitro experimental setting with missing in-vivo experiments due to a not yet feasible prototype of the novel DAC for in-vivo experiments.

Ethics committee approval

Animal experiments were carried out after receiving approval by the local government committee (Landesuntersuchungsamt Rheinland-Pfalz, Germany) under reference number 23 177-07/G 14-1-094 and in accordance with the German Animal Welfare Act (Tierschutzgesetz). All applicable international, national, and/or institutional guidelines for the care and use of animals were adhered to.

Funding:

No funding was received for this work.

Purpose:

To investigate the effectiveness of photothermal (PT)-mediated local heating for suppressing stent-induced tissue hyperplasia and to evaluate in vivo temperature during local heating of a rat's gastric outlet.

Methods and materials:

A branched gold nanoparticle (BGNP)-coated self-expandable metallic stent (SEMS) was produced for PT-mediated local heating under near-infrared laser irradiation. 45 rats were randomly divided into three groups (15 rats each). Group A received non-coated SEMS. Group B received BGNP-coated SEMS with local heating at 55°C. Group C received BGNP-coated SEMS without local heating. 5 rats in each group were sacrificed after heating. The remaining 10 rats were sacrificed 4 weeks after stent placement. The effectiveness of local heating was assessed by western blot and histopathological analysis results.

Results:

BGNP-coated SEMSs were successfully fabricated. All procedures were successful in all rats. Stent-induced tissue hyperplasia-related variables were significantly lower in group B than in groups A and C (all p<0.001). The mean degree of CD31-positive deposition was significantly lower in group B than in groups A and C (all p<0.001). The mean degree of TUNEL-positive deposition was significantly higher in group B than in groups A and C (all p<0.001). Ki67-positive mesothelial monolayers were more prominent in groups A and C than in group B.

Conclusion:

PT-mediated local heating suppressed tissue hyperplasia after stent placement in a rat's gastric outlet. The in vivo temperatures were significantly decreased compared to the in vitro temperatures during local heating.

Limitations:

It is necessary to determine timing for local heating to suppress stent-induced tissue hyperplasia.

Ethics committee approval

Animal Board approval obtained.

Funding:

Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2019R1F1A1040357).