Multimodal Visibility (Radiography, Computed Tomography, and Magnetic Resonance Imaging) of Microspheres for Transarterial Embolization Tested in Porcine Kidneys:

Microfluidic fabrication of X-ray-visible sodium hyaluronate microspheres for embolization

Catheter embolization is a minimally invasive technique that relies on embolic agents and is now widely used to treat various high-prevalence medical diseases. Embolic agents usually need to be combined with exogenous contrasts to visualize the embolotherapy process. However, the exogenous contrasts are quite simply washed away by blood flow, making it impossible to monitor the embolized location. To solve this problem, a series of sodium hyaluronate (SH) loaded with bismuth sulfide (Bi₂S₃) nanorods (NRs) microspheres (Bi₂S₃@SH) were prepared in this study by using 1,4-butaneglycol diglycidyl ether (BDDE) as a crosslinker through single-step microfluidics. Bi₂S₃@SH-1 microspheres showed the best performance among other prepared microspheres. The fabricated microspheres had uniform size and good dispersibility. Furthermore, the introduction of Bi₂S₃ NRs synthesized by a hydrothermal method as Computed Tomography (CT) contrast agents improved the mechanical properties of Bi₂S₃@SH-1 microspheres and endowed the microspheres with excellent X-ray impermeability. The blood compatibility and cytotoxicity test showed that the Bi₂S₃@SH-1 microspheres had good biocompatibility. In particular, the in vitro simulated embolization experiment results indicate that the Bi₂S₃@SH-1 microspheres had excellent embolization effect, especially for the small-sized blood vessels of 500-300 and 300 μm. The results showed the prepared Bi₂S₃@SH-1 microspheres have good biocompatibility and mechanical properties, as well as certain X-ray visibility and excellent embolization effects. We believe that the design and combination of this material has good guiding significance in the field of embolotherapy.

Recent advances and applications of microspheres and nanoparticles in transarterial chemoembolization for hepatocellular carcinoma

Transarterial chemoembolization (TACE) is a recommended treatment for patients suffering from intermediate and advanced hepatocellular carcinoma (HCC). As compared to the conventional TACE, drug-eluting bead TACE demonstrates several advantages in terms of survival, treatment response, and adverse effects. The selection of embolic agents is critical to the success of TACE. Many studies have been performed on the modification of the structure, size, homogeneity, biocompatibility, and biodegradability of embolic agents. Continuing efforts are focused on efficient loading of versatile chemotherapeutics, controlled sizes for sufficient occlusion, real-time detection intra- and post-procedure, and multimodality imaging-guided precise treatment. Here, we summarize recent advances and applications of microspheres and nanoparticles in TACE for HCC. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Percutaneous Irreversible Electroporation for Treatment of Small Hepatocellular Carcinoma Invisible on Unenhanced CT: A Novel Combined Strategy with Prior Transarterial Tumor Marking

INTRODUCTION

To explore the feasibility, safety, and efficiency of ethiodized oil tumor marking combined with irreversible electroporation (IRE) for small hepatocellular carcinomas (HCCs) that were invisible on unenhanced computed tomography (CT).

METHODS

A retrospective analysis of the institutional database was performed from January 2018 to September 2018. Patients undergoing ethiodized oil tumor marking to improve target-HCC visualization in subsequent CT-guided IRE were retrieved. Target-HCC visualization after marking was assessed, and the signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNR) were compared between pre-marking and post-marking CT images using the paired t-test. Standard IRE reports, adverse events, therapeutic endpoints, and survival were summarized and assessed.

RESULTS

Nine patients with 11 target-HCCs (11.1-18.8 mm) were included. After marking, all target-HCCs demonstrated complete visualization in post-marking CT, which were invisible in pre-marking CT. Quantitatively, the SNR of the target-HCCs significantly increased after marking (11.07 ± 4.23 vs. 3.36 ± 1.79, p = 0.006), as did the CNR (4.32 ± 3.31 vs. 0.43 ± 0.28, p = 0.023). In sequential IRE procedures, the average current was 30.1 ± 5.3 A, and both the delta ampere and percentage were positive with the mean values of 5.8 ± 2.1 A and 23.8 ± 6.3%, respectively. All procedures were technically successful without any adverse events. In the follow-up, no residual unablated tumor (endpoint-1) was observed. The half-year, one-year, and two-year local tumor progression (endpoint-2) rate was 0%, 9.1%, and 27.3%. The two-year overall survival rate was 100%.

CONCLUSIONS

Ethiodized oil tumor marking enables to demarcate small HCCs that were invisible on unenhanced CT. It potentially allows a safe and complete ablation in subsequent CT-guided IRE.

Microfluidic-prepared, monodisperse, X-ray-visible, embolic microspheres for non-oncological embolization applications

Embolotherapy using particle embolics is normally performed with exogenous contrast to assist in visualization. However, the exact location of the embolics cannot be identified after contrast washout. We developed a novel, pseudo-check valve-integrated microfluidic device, that partitions barium- impregnated alginate from crosslinking solution, thereby preventing nozzle failure. This enables rapid and continuous generation of inherently X-ray-visible embolic microspheres (XEMs) with uniform size. The XEMs are visible under clinical X-ray and cone beam CT both in vitro and in vivo. In particular, we demonstrated the embolization properties of these XEMs in large animals, performing direct intra- and post-procedural assessment of embolic delivery. The persistent radiopacity of these XEMs enables real-time evaluation of embolization precision and offers great promise for non-invasive follow-up examination without exogenous contrast. We also demonstrated that bariatric arterial embolization with XEMs significantly suppresses weight gain in swine, as an example of a non-oncological application of embolotherapy.

Novel MR-Visible, Biodegradable Microspheres for Transcatheter Arterial Embolization: Experimental Study in a Rabbit Renal Model

PURPOSE

To assess feasibility, embolization success, biodegradability, reperfusion, biocompatibility and in vivo visibility of novel temporary microspheres (MS) for transcatheter arterial embolization.

MATERIAL AND METHODS

In 9 New Zealand white rabbits unilateral superselective embolization of the lower kidney pole was performed with biodegradable MS made of polydioxanone (PDO) (size range 90-300 and 200-500 µm) impregnated with super-paramagnetic iron oxide (SPIO). Magnetic resonance imaging (MRI) was performed post-interventionally to assess in vivo visibility. Embolization success was assessed on digital subtraction angiography, MRI and gross pathology. One animal was killed immediately after embolization to assess original particle appearance. 8 animals were randomly assigned to different observation periods (1, 4, 8, 12 and 16 weeks), after which control angiography and MRI were obtained to determine recanalization. Histopathological analysis was performed to determine biodegradability and biocompatibility by using dedicated quantitative assessment analysis.

RESULTS

Ease of injection was moderate. Embolization was technically successful in 7 of 8 animals, one rabbit received non-selective embolization of the whole kidney and abdominal off-target embolization. Arterial occlusion was achieved in all kidneys, infarct areas in macro- and microscopic analysis confirmed embolization success. Control angiograms showed evidence of partial reperfusion. The microspheres showed extensive degradation over the course of time along with increasing inflammatory response and giant cell formation. SPIO-loaded MS were visible on MRI at all time points.

CONCLUSIONS

SPIO-impregnated biodegradable PDO-MS achieved effective embolization with in vivo visibility on MRI and increasing biodegradation over time while demonstrating good biocompatibility, i.e., a physiologically immune response without transformation into chronic inflammation. Further studies are needed to provide clinical applicability.

Temperature sensitive hydrogel for preoperative treatment of renal carcinoma

Surgical resection has been suggested as an effective and first-line treatment of renal cell carcinoma (RCC). However, operation is quite difficult for the patients with stage of middle-late or hypervascularized tumors. Transarterial chemoembolization (TACE) plays an important role in decreasing the size of tumors before surgery. In this work, we prepared an injectable drug-delivery system of doxorubicin-loaded temperature sensitive hydrogel for transarterial chemoembolization in RCC. The sol-gel transition behavior and rheologic analysis showed that the doxorubicin-loaded temperature sensitive hydrogel had good temperature sensitivity. Then, The X-ray experiment of hydrogel showed excellent visibility under the digital subtraction angiography and computed tomography scans in vitro and in vivo. Moreover, the studies of embolization in beagle's right kidney showed good properties in embolizing of renal arteries. In TACE therapy studies of rabbit VX₂ renal tumors, angiography, computed tomography and histopathological analysis verified that TACE therapy of doxorubicin-loaded temperature sensitive hydrogel had excellent embolic efficiency as a result of repressing the tumor growth. This hydrogel could provide valuable option in the treatment of renal cell carcinoma before surgery.

In Vitro Characterization of a Novel Type of Radiopaque Doxorubicin-Loaded Microsphere

PURPOSE

To evaluate and compare the material characteristics of a novel type of radiopaque doxorubicin-loaded microsphere (V-100) with radiopaque and non-radiopaque doxorubicin-loaded microspheres.

MATERIALS AND METHODS

The prototype V-100 featuring inherent radiopacity and three available commercial controls (DC-Bead-LUMI™-70-150, Embozene-Tandem™-100 and DC-Bead™-M1) were analyzed before and after doxorubicin loading (37.5 mg doxorubicin/1 ml microspheres) in suspension with aqua and/or aqua/iodixanol-320. Study goals included inherent radiopacity [e.g., using conventional computed tomography (CT)], doxorubicin loading efficacy, morphology using light and fluorescence microscopy, size distribution using laser diffraction/light scattering, time-in-suspension, rheological properties using rheometer analysis, and microsphere stability observed over a period of 5 days after doxorubicin loading.

RESULTS

V-100 showed good inherent radiopacity without adverse imaging artifacts. Under conventional CT, the quantitative radiopacity was as follows: 480.4 ± 2.9HU for V-100, 2432.7 ± 3.2HU for DC-Bead-LUMI™-70-150, 118.1 ± 3.0HU for Embozene-Tandem™-100, and 19.8 ± 1.5HU for DC-Bead™-M1. All of the types of microspheres showed a similar loading efficiency (> 98%) after 24 h; however, there were slower doxorubicin loading velocities for the radiopaque microspheres. The doxorubicin-loaded V-100 and Embozene-Tandem™-100 showed typical narrow-sized distributions. In aqua/iodixanol-320 suspension, doxorubicin-loaded V-100 showed the best suspension features and ideal deformability and elasticity characteristics. Similar to other microspheres, doxorubicin-loaded V-100 was very stable and storable for at least 5 days.

CONCLUSION

V-100 is a promising novel type of radiopaque doxorubicin-loaded microsphere. Compared with the controls, V-100 shows good inherent radiopacity without adverse imaging artifacts and with comparable doxorubicin loading efficacy. Further advantages of V-100 include narrow-sized distribution and excellent suspension, rheology, and stability features.

Computed tomography and histopathological findings after embolization with inherently radiopaque 40μm-microspheres, standard 40μm-microspheres and iodized oil in a porcine liver model

Purpose

The present study compared standard computed tomography (CT) and histopathological findings after endovascular embolization using a prototype of inherently radiopaque 40μm-microspheres with both standard 40μm-microspheres and iodized oil in a porcine liver model.

Materials and methods

Twelve pigs were divided into six study groups, of two pigs each. Four pigs were embolized with iodized oil alone and four with radiopaque microspheres; two animals in each group were sacrificed at 2 hours and two at 7 days. Two pigs were embolized with radiopaque microspheres and heparin and sacrificed at 7 days. Two pigs were embolized with standard microspheres and sacrificed at 2 hours. CT was performed before and after segmental embolization and before sacrifice at 7 days. The distribution of embolic agent, inflammatory response and tissue necrosis were assessed histopathologically.

Results

Radiopaque microspheres and iodized oil were visible on standard CT 2 hours and 7 days after embolization, showing qualitatively comparable arterial and parenchymal enhancement. Quantitatively, the enhancement was more intense for iodized oil. Standard microspheres, delivered without contrast, were not visible by imaging. Radiopaque and standard microspheres similarly occluded subsegmental and interlobular arteries and, to a lesser extent, sinusoids. Iodized oil resulted in the deepest penetration into sinusoids. Necrosis was always observed after embolization with microspheres, but never after embolization with iodized oil. The inflammatory response was mild to moderate for microspheres and moderate to severe for iodized oil.

Conclusion

Radiopaque 40μm-microspheres are visible on standard CT with qualitatively similar but quantitatively less intense enhancement compared to iodized oil, and with a tendency towards less of an inflammatory reaction than iodized oil. These microspheres also result in tissue necrosis, which was not observed after embolization with iodized oil. Both radiopaque and standard 40μm-microspheres are found within subsegmental and interlobar arteries, as well as in hepatic sinusoids.

Modelling of endoluminal and interstitial ultrasound hyperthermia and thermal ablation: applications for device design, feedback control and treatment planning

Endoluminal and catheter-based ultrasound applicators are currently under development and are in clinical use for minimally invasive hyperthermia and thermal ablation of various tissue targets. Computational models play a critical role in device design and optimisation, assessment of therapeutic feasibility and safety, devising treatment monitoring and feedback control strategies, and performing patient-specific treatment planning with this technology. The critical aspects of theoretical modelling, applied specifically to endoluminal and interstitial ultrasound thermotherapy, are reviewed. Principles and practical techniques for modeling acoustic energy deposition, bioheat transfer, thermal tissue damage, and dynamic changes in the physical and physiological state of tissue are reviewed. The integration of these models and applications of simulation techniques in identification of device design parameters, development of real time feedback-control platforms, assessing the quality and safety of treatment delivery strategies, and optimisation of inverse treatment plans are presented.