MRI-guided and monitored radiofrequency tumor ablation

Current research status and development prospects of embolic microspheres containing biological macromolecules and others

Transcatheter arterial embolization (TACE) has been used in the treatment of malignant tumors, sudden hemorrhage, uterine fibroids, and other diseases, and with advances in imaging techniques and devices, materials science, and drug release technology, more and more embolic agents that are drug-carrying, self-imaging, or have multiple functions are being developed. Microspheres provide safer and more effective therapeutic results as embolic agents, with their unique spherical appearance and good embolic properties. Embolic microspheres are the key to arterial embolization, blocking blood flow and nutrient supply to the tumor target. This review summarizes some of the currently published embolic microspheres, classifies embolic microspheres according to matrix, and summarizes the characteristics of the microsphere materials, the current status of research, directions, and the value of existing and potential applications. It provides a direction to promote the development of embolic microspheres towards multifunctionalization, and provides a reference to promote the research and application of embolic microspheres in the treatment of tumors.

Dynamics of MRI-Guided thermal ablation of VX2 tumor in paraspinal muscle of rabbits

This study combines fast magnetic resonance imaging (MRI) and model simulation of tissue thermal ablation for monitoring and predicting the dynamics of lesion size for tumor destruction. In vivo experiments were conducted using radiofrequency (RF) thermal ablation in paraspinal muscle of rabbit with a VX2 tumor. Before ablation, turbo-spin echo (TSE) images visualized the 3-D tumor (necrotic core and tumor periphery) and surrounding normal tissue. MR gradient-recalled echo (GRE) phase and magnitude images were acquired repeatedly in 3.3 s at 30-s intervals during and after thermal ablation to follow tissue temperature distribution dynamics and lesion development in tumor and surrounding normal tissue. Final lesion sizes estimated from GRE magnitude, post-ablation TSE, and stained histologic images were compared. Model simulations of temperature distribution and lesion development dynamics closely corresponded to the experimental data from MR images in tumor and normal tissue. The combined use of MR image monitoring and model simulation has the potential for improving pretreatment planning and real-time prediction of lesion-size dynamics for guidance of thermal ablation of tumors.

[Interventional MR imaging: state of the art and technological advances]

Due to its excellent soft tissue contrast and lack of ionizing radiation, MR imaging is well suited for interventional procedures. MRI is being increasingly used for guidance during percutaneous procedures or surgery. Technical advances in interventional MR imaging are reviewed in this paper. Ergonomical factors with improved access to patients as well as advances in informatics, electronics and robotics largely explain this increasing role. Different elements are discussed from improved access to patients in the scanners to improved acquisition pulse sequences. Selected clinical applications and recent publications will be presented to illustrate the current status of this technique.

Radiofrequency, Cryoablation, and Other Modalities for Breast Cancer Ablation

This article describes several methods for breast cancer ablation. It focuses especially on radiofrequency ablation, describing how it works, relate findings from recent studies, and comparing it with other methods of breast cancer ablation.

Magnetic resonance imaging and model prediction for thermal ablation of tissue

PURPOSE

To monitor and predict tissue temperature distributions and lesion boundaries during thermal ablation by combining MRI and thermal modeling methods.

MATERIALS AND METHODS

Radiofrequency (RF) ablation was conducted in the paraspinal muscles of rabbits with MRI monitoring. A gradient-recalled echo (GRE) sequence via a 1.5T MRI system provided tissue temperature distribution from the phase images and lesion progression from changes in magnitude images. Post-ablation GRE estimates of lesion size were compared with post-ablation T2-weighted turbo-spin-echo (TSE) images and hematoxylin and eosin (H&E)-stained histological slices. A three-dimensional (3D) thermal model was used to simulate and predict tissue temperature and lesion size dynamics.

RESULTS

The lesion area estimated from repeated GRE images remained constant during the post-heating period when the temperature of the lesion boundary was less than a critical temperature. The final lesion areas estimated from multi-slice (M/S) GRE, TSE, and histological slices were not statistically different. The model-simulated tissue temperature distribution and lesion area closely corresponded to the GRE-based MR measurements throughout the imaging experiment.

CONCLUSION

For normal tissue in vivo, the dynamics of tissue temperature distribution and lesion size during RF thermal ablation can be 1) monitored with GRE phase and magnitude images, and 2) simulated for prediction with a thermal model.