Dimensional Printing in Cardiology : Innovation for Modern Education and Clinical Implementation

Medical uses of three-dimension (3D) printing have advantages for many importances, such as tissue and organ fabrication, creation of prosthetics, and model structural anatomy. Visualization of 3-dimensional structure of heart for the importance of examination, management or education is not fully comprehensive describe toward the complexity of anatomical structure and also toward the illustration of medical procedure. The aim of this study was to identify the potential application of heart’s 3D printing for the enhancement of case understanding for doctor, medical students or residents and also for patient and its family. A normal model of heart is used in this research to stimulate next 3D object in cardiology area.We retrieved data from patients’ CT scan performed in Gadjah Mada University Hospital, Yogyakarta from December 2017 to March 2018. Our focus is on normal heart anatomy. Data from CT scan results are exported into Digital Imaging and Communications format (DICOM), then dimension measurement and threshold segmentation are performed using Mimics Medical 20.0 (Materialise) application. Finally the file must be exported into STL format due to final process to cut the desirable parts using Mesh editing application. After the final model has been done, then it will be printed by fuse deposition method to make a 3D object.The making and implementing 3D printingof heart model has many advantages for medical education especially for the doctor, medical students or residents and also for the patient and its family to be more aware on the condition of the heart. This study may stimulate another trial of using this technique into several heart abnormalities


INTRODUCTION
A 3D printing is a promising technique that may have applications in medicine.Additive manufacturing, also known as 3D printing, is the process of creating physical objects by adding successive layers of material in different shapes.This process has become more practical and affordable.
1 Medical uses of 3D printing have advantages for many importances, such as tissue and organ fabrication, creation of prosthetics, and model structural anatomy.

2
Visualization of 3 dimensional structure of heart for the importance of examination, management or education is not fully comprehensive describe toward the complexity of anatomical structure and also toward the illustration of medical procedure for doctor to threat patient, medical students or residents, and also for patient and it's family.3D printing is a technique to change and to create digital object into a real object with the same shape, size and details Finally the file must be exported into STL format due to final process to cut the desirable parts using Mesh editing application.After the final model has been done, then it will be printed by fuse deposition method to make a 3D object.Fuse Deposition Method (FDM) is chosen because of the needs of accuration, appearance, surface object, and the strength of ingredients property.FDM is based on the melting and extrusion of a polymer filament.The polymer filament will be processed begin from the melting process that ending in a nozzle, forming a thread, and shaping the thread into a plastic part until we got an object same as in the STL file.

RESULTS
The first step to create a model for medical education using 3D printing is defining the educational objective.In this research a normal heart is used.For planning the 3D prototype, there aresome essential characteristics of the model should be considered with the educational need.There are size, surrounding structures, surgical manipulation, accuracy and resolution of the model 4 .The procedure that must be performed is divided into several stages with several different software, the difference between rigid and elastic printing is only on the machine settings and the addition of a guide on the machine.The following is the process carried out to print 3D models with 3D printerwith rigid and elastic material : • Making a model, modeling is done using a computer and data inputted from CT Scan.This data is in the form of DICOM and processed into an STL file that can be processed into objects from 3D print • STL cannot be directly used to command the machine, STL must be changed to G-Code or commonly called G code.G code is the machine language that is controlled by the computer.This code contains the position that must be achieved by the machine so as to produce a shape according to the STL and the model that has been input from the previous process • Printer preparation phase, before initiate printing, the 3D printer must be calibrated.This calibration is done automatically by the 3D print machine.This calibration is in the form of checking the axis totaling 3 pieces, namely X, Y, and Z.The axis is calibrated so that the results of precision printing.

DISCUSSION
The use of 3D Printing in the manufacture of prototype machines / technical objects is based on fused deposition method.3D FDM printers are the cheapest printer with the cheapest machine manufacturing costs.This is often used by engineering professionals in making machine prototypes or initial imitations of objects to be done using metal or larger machines.
There are some superiorities of this printing, such as :  Faster production.3D printing is faster than conventional manufacturing including injection molding and subtractive production.From prototypes to final products, the idea of testing 3D printing and design quickly.Faster design and prototype production means more time to repeat the prototype and find a product market match before competitors.3D printing production only takes a few hours.Instead, testing ideas and designs with conventional manufacturing methods can take days, if not several weeks. Easy to access.3D printing has been around for decades but it really did not take off until 2010.The explosion of interest in 3D printing has brought easier to use software and hardware to consumers because more competition is entering that space.It's never easier to learn technology and you can combine it in a matter of days into your production cycle. Better Quality.Traditional manufacturing methods can easily produce bad designs, and therefore poor quality prototypes.3D printing allows assembly step by step from the object, which guarantees enhanced design and better quality objects. Cost effectiveness.With 3D printing, however, labor can be as little as one person issues a print order. Unlimited Forms and Geometry.The old method of manufacturing relies on mold and cutting technology to produce the desired shape.Designing complex geometric shapes can be difficult and expensive with this technology.3D printing faces this challenge easily and there are not many technologies that cannot be done with the right supporting material. Less Waste Production.CNC cutting and injection molding produce a lot of wasted resources.Both involve removal of material from solid blocks.Unlike both, 3D printing only uses the material needed to make prototype parts -no more, no less.In addition, reusing materials from 3D printing is relatively straight forward.As a result, additive manufacturing only produces little waste, and saves a lot of money for the company.
The accuracy of 3D model is needed to achieve a better model by precisely demonstrating the complex structure and the abnormality of heart. 7Accuracy measurement process for heart models in this section are divided into two, namely the CT dimension and measurement validation on the patient's DICOM file.Both of these processes are sequential in order to produce high-accuracy cardiac anatomical models.Yoo et al. found that in congenital heart disease for example, the surgical technique is challenging.The size of heart is small and the access for operating the heart is limited.Thus, the rareness of certain congenital heart diseases further limits the chance to study and to improve the surgical skills 8 .Integration of multiple imaging modalities may be a good solution in acquiring high-quality medical images.A combination of multi-slice CT (MSCT) and 3D TEE produces a more ideal model compared with MSCT alone to get high quality of medical images.9 Errors can be happened during any step of the process, including image acquisition and segmentation.Although accuracy of the source images and appropriate choice of printing modality and materials are critical to achieve optimum accuracy, image segmentation and STL conversion remain the most error-prone steps.Giannopoulos et al revealed that there are two main factors that may reduce errors.First, an expert in the field who ideally is a doctor should perform the image postprocessing.This will ensure that the printed model is precisely fabricate the clinical interpretation of the images, because segmentation accuracy requires proper recognition of structures and their separation from imaging modality artifacts.Second, the segmentation software is so important.There is limited software designed for medical 3D printing, the specific medical application in segmentation data from CT Scan is suggested to produce high quality and accuracy of stl file.In this study we use mimic materialise software for segmenting dicom file from CT Scan. 10

Limitations of the study
A limitation of our study is the lack of validation for evaluation the real dimension from model.The specific defect location also could not be fabricated precisely because of the difficulty to adjust the threshold in segmentation process to make STL file.The accuracy of a medical model depends on many factors especially the operator performing the virtual segmentation correctly.Besides, the reproducibility and accuracy is also depends on 3D printers specification regarding print resolution.

Making
and implementing 3D printingof heart model has many advantages for medical education especially for the doctor, medical students or residents and also for the patient and its family to be more aware on the condition of the heart.This study may stimulate another trial of using this technique into several heart abnormalities.

OC 6 Figure 1 .
Figure 1.The step to make 3D object from CT scan file

Figure 2 .
Figure 2. The comparison between pre-print data in STL format and the printed object.