In vitro evaluation of radiopacity of contrast-loaded superabsorbent polymer microspheres (SAP-MS) with static imaging and flow model.

<bold>Purpose: </bold>To evaluate the radiopacity of contrast-loaded superabsorbent polymer microspheres (SAP-MS) under X-ray imaging.<bold>Materials and Methods: </bold>SAP-MS were suspended in contrast material (iodixanol) and the diameter change was assessed. The diameter of contrast-loaded SAP-MS in saline was measured sequentially. Radiography of the contrast-loaded SAP-MS was evaluated as radiopacity by contrast-to-noise ratio and visibility by multiple reader scoring. Under digital subtraction angiography, contrast-loaded SAP-MS were injected into a flow model. The flow speed was 1-10 cm/s, and images were acquired at 1-7.5 frames per second using a pulse width of 10-85 ms. Images were assessed by multiple reader scoring.<bold>Results: </bold>The diameter of SAP-MS increased to 4.0-5.0 times its original size for approximately 15 min. The diameter of contrast-loaded SAP-MS in saline further increased by 10-30% within several minutes and returned to the previous size. Radiopacity and visibility of contrast-loaded SAP-MS decreased in 30 min after mixing with saline. Visibility was better with slow flow speed and narrow pulse width.<bold>Conclusion: </bold>For effective observation, contrast-loaded SAP-MS should be kept in non-diluted contrast material until use. The conditions of slower flow and use of a narrow pulse width are recommended. [ABSTRACT FROM AUTHOR]