Patient-specific or personalised 3D printed models created from cardiac imaging data can be applied to research areas beyond the current domains of 3D printing in cardiovascular disease, which mainly focuses on pre-surgical planning and simulation, medical education and training, as well as doctor-patient communication. These areas represent the most commonly used applications of 3D printed models, in particular, use of 3D printing models on congenital heart disease is a very promising field with sufficient evidence provided by randomised controlled trials. Further, 3D printed heart models are shown to play an important role in guiding patient's surgical planning and treatment as reported by single and multi-center studies. 3D printed models are also useful to educate medical students, healthcare professionals or junior residents in improving their understanding of complex cardiac anatomy and pathology. In addition to these reported applications, the realistic physical models serve as a valuable tool in studying appropriate cardiac CT protocols for the purpose of optimizing CT scanning techniques.

Zhonghua Sun, a professor and medical imaging researcher from Curtin University, Australia has been in search of new ways to acquire accurate and efficient medical images. Prof Sun's research interests include 3D visualization and diagnosis of cardiovascular disease, 3D printing in medical applications. In his recent work, published in Current Medical Imaging, Prof. Sun presents a new research direction for using 3D printed personalised cardiovascular models in studying CT protocols for the purpose of minimizing radiation dose without compromising image quality. He has developed the research team to focus on 3D printing in congenital heart disease, aortic and coronary disease and pulmonary embolism.

In his latest review, Prof Sun provides readers with information on how 3D printed aorta, pulmonary and coronary models can be used as an alternative to conventional anthropomorphic phantoms in studying optimal CT imaging protocols. In particular, there are two challenging areas of cardiac CT imaging highlighted in the review: calcified coronary plaques and coronary stenting. Although improved spatial and temporal resolution with advanced CT scanners, coronary CT angiography has moderate diagnostic value in imaging calcified plaques due to blooming artifacts, and in coronary stents because of metal-related artifacts which significantly affect its visualization and assessment of coronary lumen, resulting in high false positive rates. Thus, these 3D printed coronary models represent a novel phantom since the models are printed using patient's CT data, which replicate normal coronary anatomy including coronary artery branches, curvature and angle. Preliminary results indicate the feasibility of simulating calcified plaques and coronary stents in these printed models with promising results reported in the literature, although further research is needed to validate these findings by testing different scanning parameters.

CTA is not only the reference method in preoperative imaging of aortic aneurysm and dissection but also a preferred modality in the follow-up of patients with aortic aneurysmal disease after treated with endovascular stent graft repair. Regular follow-ups of these patients with CTA at 3 months, 6 months and 12 months thereafter increase cumulative radiation dose. Therefore, dose optimization is clinically important. "3D printed aortic models play a role in this area, in addition to its reported value in guiding complex aortic surgery or endovascular aortic repair," says Prof. Sun, adding that "Printing aortic dissection models is very challenging compared to other cardiovascular models due to very thin membranous structure of the intimal flap."

Prof. Sun's team is continuing to carry out more research on the development of aortic dissection models. CT pulmonary artery (CTPA) is a widely recognised modality in the detection of pulmonary embolism with high accuracy, thus, serving as the first line technique in the clinical diagnosis. Due to its widespread use, reduction of radiation dose and contrast dose has become a necessity with many low-dose protocols available. "3D printed pulmonary models can replicate normal pulmonary arteries with simulation of pulmonary emboli in both large and peripheral artery branches with low-dose protocols identified," says Dr. Sun. However, he insists that further experiments with reduction of contrast medium dose need to be conducted.

"Our work encourages more research to be conducted along this pathway and we expect further interesting results available soon in medical imaging literature," notes Prof. Sun.

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