Introduction
Three-dimensional (3D) printing technology, which was defined as the process of creating solid, 3D objects from a collection of images in the form of a digital file, has been applied to the medical field and played an increasingly significant role in the diagnosis and treatment of cardiac diseases due to the continuous advancement of materials, medical imaging technology, and the vigorous development of individualized cardiac therapy1. As a bridge between physical and imaging data, the 3D printed models can display the complex intracardiac pathological anatomy with a more comprehensive, intuitive way and provide preoperative exercise opportunities for individualized surgery as well. Scholars have reported the application of 3D printing technology in the diagnosis and treatment of cardiac disease for such procedures as valve replacement and formation, complex congenital heart disease 2,3 .
CT (computed tomography) is the mainstream data source of 3D printing technology, but it may involve intravenous contrast and ionizing radiation, the image quality is affected by heart rate4,5. Three-dimensional echocardiography is another imaging modality with strong linear correlation with CT,new echocardiographic transducers and advanced software and hardware have optimized 3D echocardiographic images. Moreover, because of its portability, safety, none radiation exposure, high spatial and temporal resolution, superior ability to image fast moving structure6, involves no sedation or general anesthesia, echocardiography images may be more advantageous as the data source in the procedure of printing 3D models7,8.
Atrial septal defect (ASD) is one of the most common congenital heart diseases, accounting for 20% to 30% of adult congenital heart disease. As the effective therapeutic methods, ASD occlusion has been widely applied. Imaging data provided by different techniques always play a significant role in the diagnosis and treatment of ASD. However, they are lack of comprehensive, real touch and visual experience that can be obtained by a patient-specific physical model 9. 3D printed models based on echocardiography images may show the anatomical details of the pathological structure clearly and act as the guidance for individualized treatment.
Feasibility and fidelity are prerequisites and guarantees for the ultrasound-derived 3D printing ASD models to be fully utilized. Whether it can highly retain and replicate the original image information is the basis for the 3D printed model to fully combine the advantages of three-dimensional transesophageal echocardiography (3D-TEE images) and 3D printing technology. Only when fidelity was guaranteed will the 3D printed model considered as an accurate measurement tool as the conventional 3D-TEE images and provide visual and tactile perception well. However, steps of creating 3D ASD model from an echocardiogram to a tangible 3D model are so complex that errors may be brought in, there is a risk of introducing design errors and manipulating the original source data in order to generate oversimplified 3D models10. Focused on process-oriented outcomes, which means analysis the parameters in each step of the printing process, is an efficient method to assess the fidelity of the 3D models in some studies2,11.
This study aims to evaluate the feasibility and fidelity of 3D printed ASD models from echocardiographic images. Moreover, our study intends providing evidence for potential applications of 3D printing technology based on echocardiographic data in ASD therapy, especially individualized ASD occlusion.