Multimodality Imaging of Ethiodized Oil–loaded Radiopaque Microspheres during Transarterial Embolization of Rabbits with VX2 Liver Tumors

Abstract

equally to this work.q RSNA, 2015 Purpose:To assess the visibility of radiopaque microspheres during transarterial embolization (TAE) in the VX2 rabbit liver tumor model by using multimodality imaging, including singlesnapshot radiography, cone-beam computed tomography (CT), multidetector CT, and micro-CT. Materials and Methods:The study was approved by the institutional animal care and use committee. Fifteen VX2-tumor-bearing rabbits were assigned to three groups depending on the type of embolic agent injected: 70-150-mm radiopaque microspheres in saline (radiopaque microsphere group), 70-150-mm radiopaque microspheres in contrast material (radiopaque microsphere plus contrast material group), and 70-150-mm radiolucent microspheres in contrast material (nonradiopaque microsphere plus contrast material group). Rabbits were imaged with singlesnapshot radiography, cone-beam CT, and multidetector CT. Three to 5 weeks after sacrifice, excised livers were imaged with micro-CT and histologic analysis was performed. The visibility of the embolic agent was assessed with all modalities before and after embolization by using a qualitative three-point scale score reading study and a quantitative assessment of the signal-to-noise ratio (SNR) change in various regions of interest, including the tumor and its feeding arteries. The Kruskal-Wallis test was used to compare the rabbit characteristics across groups, and the Wilcoxon signed rank test was used to compare SNR measurements before and after embolization. Results:Radiopaque microspheres were qualitatively visualized within tumor feeding arteries and targeted tissue with all imaging modalities (P , .05), and their presence was confirmed with histologic examination. SNRs of radiopaque microsphere deposition increased after TAE on multidetector CT, cone-beam CT, and micro-CT images (P , .05). Similar results were obtained when contrast material was added to radiopaque microspheres, except for additional image attenuation due to tumor enhancement. For the group with nonradiopaque microspheres and contrast material, retained tumoral contrast remained qualitatively visible with all modalities except for micro-CT, which demonstrated soluble contrast material washout over time. Conclusion:Radiopaque microspheres were visible with all imaging modalities and helped increase conspicuity of the tumor as well as its feeding arteries after TAE in a rabbit VX2 liver tumor model.q RSNA, 2015

131I-Labeled Copper Sulfide-Loaded Microspheres to Treat Hepatic Tumors via Hepatic Artery Embolization

“…Additionally, our work showed that SPECT/photoacoustic imaging mediated by 131 I-HCuSNPs-MS-PTX could help to confirm the delivery of the microspheres to the targeted tumors and to guide therapy planning for near-infrared laser irradiation. Previous studies have focused on embolic microsphere detection with CT and magnetic resonance (MR) imaging 67 - 69 ; however, the high sensitivity of SPECT/CT and high specificity of photoacoustic imaging in our study obviated the need for additional imaging.…”

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

“…In the clinical setting, after embolization with standard microspheres, such imaging features can be achieved only with a low degree of reproducibility since the iodinated contrast agent is rapidly and unpredictably washed out [ 13 , 24 , 25 ]. Moreover, the transient intratumoral contrast agent saturation may not represent the exact location of the microspheres but mainly stasis of the iodinated contrast agent column [ 12 , 13 , 24 , 29 ]. Using inherently radiopaque microspheres, the true intra- and peritumoral microsphere distribution could be assessed objectively, and treatment endpoints could be optimized and standardized (e.g.…”

“…Using inherently radiopaque microspheres, the true intra- and peritumoral microsphere distribution could be assessed objectively, and treatment endpoints could be optimized and standardized (e.g. by using microsphere quantification techniques for the embolized target volume) [ 12 , 13 , 30 ]. Another important issue is the sensitivity of the imaging method which is being used for visualizing radiopaque embolic agents.…”

“…Another important issue is the sensitivity of the imaging method which is being used for visualizing radiopaque embolic agents. In previous animal studies, the visibility of embolic agents was frequently assessed by applying experimental imaging techniques (e.g., micro CT or high-dose CT) [ 12 , 14 , 31 ]. For usability in clinical practice, the embolic agent needs to be visible when applying standard CT with clinically established acquisition and image reconstruction parameters.…”

“…The introduction of inherently radiopaque, x-ray-visible microspheres is another trend in liver tumor embolization [ 12 – 16 ]. Currently, the commercially available Embozene microspheres are not inherently visible applying standard x-ray or magnetic resonance imaging (MRI) techniques.…”