Abstract:

A prototype is well established as a “design tool” for its key role in problem-solving. Prototypes for industrial applications are well investigated and demonstrated. Prototype making involves a lot of creativity besides necessary skill and resources. With the advent of three dimensional (3-D) CAD and 3-D printing, making prototype has become somewhat effortless.

Since last decade, 3-D printed prototypes are being used for various healthcare applications. From published literature, we can see its applications are growing. Some of its applications include anatomical models for teaching, procedural planning, surgery guides and implants. The medical image information obtained as DICOM data can be processed to integrate and regenerate shape of anatomy. This forms the basis of medical 3-D virtual modelling and subsequently its fabrication using 3-D printing.

From literature study, we see work on hard tissues while soft-tissue applications are sparse. This is due to certain challenges they pose in image processing. The current research study, focus on one of the soft tissue based organs, namely, the heart. The motivation comes from the risks that the organ poses at birth, called Congenital Heart Disease (CHD). They are caused due to the malformed heart during embryonic development in the foetus. Due to the random nature of defect occurrence, they manifest in many varieties. Many such defects which are mild, get resolved in the early infancy. However, the severe and moderate defects need surgical interventions. Like any treatment, early detection helps to plan treatment management. The echocardiography of neonate is a gold standard to assess the condition in most cases. However, there are a few complexities which are hard to diagnose and plan corrective procedure. The infant’s heart surgeries are generally risky and planning such intervention on the operation table can be risky and can lead to loss of precious time. In such cases, clinicians may study the digital models on a computer. The virtual 3D models can be zoomed in and panned and rotated to explore. Surgeons are used to spatial visualization wherein touch and feel is essential. With just the virtual models on screen, the rich heart morphology cannot be completely visualised. It is here that we see clinicians need physical models for haptic exploration in true size and shape to plan interventional procedures. These physical models can be called patient-specific heart models. While the literature shows such applications; we observed few gaps: absence of standard workflow procedure, to identify the nature of cases which demand models, how to accurately produce them and how to evaluate their accuracy.

In this research, we investigated the role of physical prototype models in complex morphology visualization. The study involved totally 21 cases live of CHD. The process of 3-D modelling was established with a pilot study on five samples. 16 Patient-specific heart models of CHD were successfully built. The models were checked for accurate fabrication and were issued to the clinicians. Out of the 16 live cases, we found 19\% were simple VS defects and models just reconfirmed defects already diagnosed, so, it did not add any additional value. 37% felt that they could visualise more details in the models then what they initially saw from the image data. 44% of the cases comprising of combination defects had ambiguous image reports and were not conclusive. In all such cases, the clinicians found availability models very useful. They opined that visualization of defect morphology from the models aided in understanding the defect condition better. The enhanced understanding helped them to plan treatment management. Models also helped them to communicate with the kin better. From the study, it is clear that the models help in better visualization of defect morphology. They further enable exploratory surgical options and scenario building. The initial condition, surgical plan with model and procedural outcome were analysed with expert clinicians.

A validated detailed workflow including an approach to building accurate models and evaluation for accurate recreation with optimum sections are the main contribution of this research study. A new benchmark model for ascertaining the accuracy of the 3-D printer and printed output for Bioforms is proposed and demonstrated. The study further investigates into the threshold need for such models. Combination defects need models to plan and manage treatment. The study helps adoption of 3-D printing for complex congenital heart defect evaluations and save a fragile precious life.

Optimum Sections, 3-D scatter map of defect volume, use of VR / AR gear are few new thoughts synthesized in this research study, hold good potential for further work.