Purpose: 3D-printing of patient-specific phantoms such as the mitral valve (MV) is challenging due to inability of current imaging systems to reconstruct fine moving features and 3D printing constraints. We investigated methods to 3D-print MV structures using ex-vivo micro-CT. Materials and Methods: A dissected porcine MV was imaged using micro-CT in diastole, using a special fixation holder. The holder design was based on a patient ECG gated cardiac CT scan using as reference points the papillary muscles and annulus. Next the micro-CT volume was segmented and 3D-printed in various elastic materials. We tested different postprocessing techniques for support material removal and surface coatings to preserve the MV integrity. To test the error a Cloud Comparison of the porcine valve-mesh file and the valve-mesh file from the patient ECG gated cardiac CT scan was performed. Results: Best results for the 3D-printed models were achieved using TangoPlus poly-jet material with a Objet Eden printer. The error computation yielded a 2.6mm deviation-distance between the two aligned valves indicating adequate alignment. The post-processing methods for support removal were challenging and required 24+ hours sample-emersion in slow agitating sodium hydroxide baths. Conclusions: The most challenging part for MV manufacturing is 3D volume acquisition and the post-printing methods during support cleaning. We developed methods to circumvent both, the imaging and the 3D-printing challenges and to ensure that the final phantom includes the fine chordae and valve geometry. Using these solutions, we were able to create complete MV structures which could benefit medical research and device testing.
Purpose: Intracranial aneurysm (IA) treatment using flow diverters (FDs) has become a widely used endovascular therapy with occlusion rates between 70 to 90 percent resulting in reduced mortality and morbidity. This significant variation in occlusion rates could be due to variations in patient anatomy, which causes different flow regimes in the IA dome. We propose to perform detailed in-vitro studies to observe the relation between the FD geometrical properties and IA hemodynamics changes. Materials and Methods: Idealized and patient-specific phantoms were 3D-printed, treated with FDs, and connected into a flow loop where intracranial hemodynamics were simulated using a programmable pump. Pressure measurements were acquired before and after treatment in the main arteries and IA domes for optimal and sub-optimal diameter sizing of the FD when compared with the main artery. The 3D-printed phantoms were scanned using a micro-CT to measure the ostium coverage, calculate the theoretical FD hydraulic resistance, and study its effect on flow. Results: The pressure differences between arteries and the IA dome for optimal FDs’ diameter with a hydraulic resistance of 3.4 were ~7 mmHg. When the FD was undersized, the hydraulic resistance was 4.2 and pressure difference increased to ~11 mmHg. Conclusion: 3D-printing allows development of very precise benchtop experiments where pressure sensors can be embedded in vascular phantoms to study hemodynamic changes due to various therapies such as IA treatment with FDs. In addition, precise imaging, such as micro-CT can be used in order to evaluate complex deployment geometries and study their correlation with flow.