Here, we present a protocol to use three dimensional printed models for pre-operative planning and intra-operative reorganization of complicated vascular locations when handling a congenital aortic anomaly.
Complex congenital aortic anomalies include diverse types of malformations that may be clinically asymptomatic or present with respiratory or esophageal symptoms. These anomalies may be associated with other congenital heart diseases. It is hard to identify the accurate anatomic vessel location from two-dimensional imaging data, such as computed tomography. As an additive manufacturing method, three-dimensional (3-D) printing can covert the acquired imaging data into 3-D physical models. This protocol describes the procedure for modeling the volumetric DICOM imaging into 3-D data and printing it as an anatomically realistic 3-D model. Using this model, surgeons can identify the vessel location of complex aortic anomalies, which is helpful for pre-operative planning and intra-operative guidance.
Congenital aortic anomalies are extremely rare congenital malformations of the aortic arch system. They can be diagnosed either by imaging analysis or by evaluation of entities like dysphagia or subclavian steal1. In clinical scenarios, it is important to identify the anatomical anomaly in the confined surgical space that has limited visualization during the surgery2,3. Currently, conventional planar two-dimensional (2-D) imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), are usually presented to surgeons before the surgery. However, it is difficult for surgeons to image the anomaly based on the 2-D imaging. Consequently, they could encounter unpredictable difficulties while trying to separate the complex aortic vessels during surgery. Unpredictable injury to the vessel, the trachea and the esophagus could occur and result in disastrous outcomes.
In the last decade, 3-D imaging modeling has been used in cardiac surgery to help surgeons understand the complex anatomic anomaly4,5,6,7. Three-dimensional (3-D) printing technology can help convert the modeling data into a physical model. Compared with the digital reconstruction, 3-D printed physical models could present a better understanding of the anatomical details and provide an intuitional view of the malformation. For aortic anomaly surgery, the printed intuitional 3-D model is significant because poor understanding of aortic locations could be disastrous to patients. During the surgery, any mistake could lead to unpredictable bleeding and injury. Using the printed models, surgeons can fully understand the spatial relationships of aortic branches. During the surgery, the surgeons can also perform real-time review of the 3-D models to avoid confusion of the complex vascular locations.
Here, we present a protocol to apply 3-D printed models for pre-operative planning and intra-operative guidance while dealing with congenital aortic diseases. Kommerell's diverticulum, a type of complex congenital aortic anomaly, was selected as a case study. The steps include diagnosis based on computed tomography angiography (CTA) imaging, partitioning regions of interest, building 3-D models, preoperative surgical planning, and intra-operative reviewing of 3-D printed models8. This 3-D printing strategy could substantially reduce the risk of unpredictable tissue injury during the surgery.
The present study was approved by the ethics committee of Zhongshan Hospital Fudan University (B2016-142R) and all participants gave their informed consent.
1. Diagnosis of the Aortic Anomaly by Symptoms and Acquisition of Imaging Data
2. Segmentation of Regions of Interest
3. 3-D Reconstruction of the ROI
4. 3-D Printing
5. Preoperative Planning and Intraoperative Review Using 3-D Printed Models
Acquisition of CT angiography images, digital modeling and 3-D printing were all done in a hospital. Two hours were spent to get the 3-D model from the CT angiography image ready for the 3-D printing. Using the procedure and 3-D printer here, a patient-specific 3-D physical model can be sent to physicians quickly and the surgical decision can be made in time. The workflow from acquisition of CT angiography data to 3-D printing was shown in Figure 1. From the coronal plane (Figure 2A), the transverse plane (Figure 2B) and the sagittal plane (Figure 2C), the CT angiography image was reconstructed into a 3-D model (Figure 2D). The anatomic relationship between aorta and tracheal was displayed along the Y-axis (Figure 3A-3D).
Figure 1. Workflow from CT angiography to 3-D models Please click here to view a larger version of this figure.
Figure 2. Processing of CT angiography data in coronal plane (A), transverse plane (B) and sagittal plane (C). (D) The reconstructed CT angiography data was obtained. Please click here to view a larger version of this figure.
Figure 3. Reconstructed 3-D aorta and trachea model was displayed along Y-axis in the coronal plane (A), transverse plane (B) and sagittal plane (C). (D) The reconstructed CT angiography data was obtained. Please click here to view a larger version of this figure.
Congenital aortic anomalies comprise a rare spectrum of cardiovascular diseases, which often show complex aortic anomalies. Medical imaging, such as CT and MR, are required to elucidate complex aortic arch anomalies, the abnormal branching pattern, their relationship with the trachea and the esophagus, and other associated pathologies. Both CT and MR angiography can provide 2-D information of aortic vessel locations. With 3-D digital reconstruction of 2-D imaging, the anatomical relationship of the aortic vessels can be defined further. However, it is not sufficient to provide a clear view of realistic anatomical structure for surgeons. Kommerell's diverticulum, a rare congenital aortic anomaly, is difficult to be understood for some surgeons due to the variability and complexity of this disease1. Therefore, surgical management of this disease needs to be optimized.
The workflow described here includes diagnosis based on imaging data, partitioning the regions of interest, constructing digital 3-D models, printing the 3-D models, preoperative planning and intraoperative reviewing. CT is a common imaging modality for diagnosis of aortic anomalies before surgery. Due to its submillimeter and excellent spatial resolution, CT is commonly used for 3-D printing. Although MR images can also be used for 3-D modeling in some cases, the spatial resolution of MR is generally lower than that of CT. Based on CT datasets, segmentation can convert the anatomical information of the ROI into a patient-specific digital 3-D model. The source of the DICOM data, the complexity of the anomaly, and the operator experience with the software may greatly influence the time required for image segmentation. Moreover, surgeons are also necessary to guide the choice of the ROI in the segmentation procedure. Hence, a team involving surgeons, radiologists and engineers meet to have a discussion before surgery for efficient performance. The rapid diagnosis and in-hospital printing can save time for patients, especially for those who suffered from an emergent dissection or rupture10. Therefore, an in-hospital 3-D printing lab is necessary to be established for efficient workflow.
For fellows and residents, even for attending surgeons who have few experiences to perform surgery on complex aortic anomaly, a printed 3-D model could be used to help understand the complex abnormality. A printed model 3-D is a valuable teaching and training tool for easy access to actual anatomical specimens and help flatten the learning curve. They can also serve as an effective tool for communication with patients and their families during the pre-operative counseling.
Although the physical printed 3-D model is helpful for surgeons to understand the anomaly intuitively, it could also allow surgeons to practice the planned operation on the model. Therefore, novel materials should be applied in the 3-D printing to mimic the natural tissue. Collectively, the printed 3-D model provides an intuitional means of viewing and understanding the patient's complex aortic anatomy. It can help determine a personalized surgical process for the Kommerell's diverticulum and reduce the potential risk of injury.
The authors have nothing to disclose.
The authors acknowledge funding from National Natural Science Foundation of China (No. 81771971), Shanghai Pujiang Program (No. 14PJD008 and 17PJ1401500), "Chen Guang" Project Supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (No. 14CG06), Natural Science Foundation of Shanghai (Nos. 17411962800 and 17ZR1432900), and Science and Technology Commission of Shanghai Municipality (17JC1400200). W.Z. acknowledges funding from the National Natural Science Foundation of China (31501555 and 81772007, and 21734003), the China's 1000 Young Talents Program, Education Commission of Shanghai Municipality (Young Eastern Professorship Award), and Science and Technology Commission of Shanghai Municipality (17JC1400200 and 16391903900).
3D printer | Meditool Enterprise Co., Ltd | For 3D printing | |
Chaos Version 2.0 | Meditool Enterprise Co., Ltd | For 3D segmentation and reconstruction |