In the surgical treatment of unruptured intracranial aneurysms (UIAs), a thorough understanding of the positional relationship of the aneurysm with the parent artery and its branches, bones, brain parenchyma, and cranial nerves is of great importance [6]. In the past, surgical treatment was acquired through practical experience gained during actual operations. Recently, however, there have been increasingly fewer opportunities for junior surgeons to receive on-the-job training owing to restrictions imposed by society and the extensive use of endovascular techniques [5].

To resolve this problem, three-dimensional (3D) printing technology has been adopted as neurosurgical training in recent years [3,11,12]. With rapid advances in additive manufacturing and 3D printing [1], 3D models of any organ can now be created directly from two-dimensional (2D) computed tomography scans or magnetic resonance images [9]. These models are physiologically and anatomically accurate and very helpful for gaining an understanding of the structures. For these reasons, these models are recently being used in the clinical setting, and they have shown to be effective teaching tools for training junior surgeons. The application of 3D printing technology in neurosurgical training has been reported in recent years and its usefulness has been demonstrated [5,8,10].

Such advantages led us to postulate that patient-specific 3D printed aneurysm models might be useful educational tools for patients and family members. Until now, 2D imaging, such as computed tomography angiography (CTA) or cerebral angiography, was the only method available for patient educations. With the digitalization of diagnostic radiologic images, it has become easy to obtain simulated 3D images at desired angles by, for example, 3D-CTA or 3D digital subtraction angiography (3D-DSA) [2]. Although this method is useful, it is difficult to understand the complexity of the vascular network around the aneurysm, and all these images can only be presented on a computer screen.

We believe a true 3D printed model is more advantageous as an educational tools. However, no study has focused on patients' understanding and satisfaction of aneurysm clipping surgery. Thus, we created patient-specific 3D printed aneurysm models as an educational tool for patients who were scheduled to undergo aneurysm clipping surgery. In this study, we describe how these 3D models were created and the effects of applying them for patient education purposes.

In this study, 20 patients with UIAs (five men and 15 women; mean age, 59.4 years [range, 50–71]) were enrolled. Characteristics of age and level of education were similar between the two groups. The location, size, and diameter of aneurysm were summarized in Tables 1 and 2 for each group. There are no statistically significant differences in the mean size of the aneurysm which length (group I, 4.56±1.57 mm; group II, 5.60±1.57 mm; p=0.144), width (group I, 5.01±1.14 mm; group II, 5.06±1.25 mm; p=0.924), and height (group I, 5.12±1.54 mm; group II, 5.61±1.78 mm; p=0.524) between two groups. The mean diameter of aneurysm neck of group I was 3.43 ± 0.55 mm, whereas the mean diameter of group II was 4.11±0.94 mm (p=0.063).

All patients underwent aneurysm clipping surgery under general anesthesia. Additionally, all 20 patients underwent CTA, DSA, and MRA, and the 3D models of the aneurysms were printed based on MRA DICOM data. The proposed method successfully produced patient-specific 3D printed aneurysm models that precisely matched the images reconstructed through 3D DSA and Materialise Mimics. A total of 20 patients in group I and II participated in the survey after completing the consultation. Table 3 shows the questions of the questionnaire with the mean responses and ranges in group I and II.

The time required for manufacturing was 3-4.5 hours, and it tended to increase with the size of the 3D vascular model. This was mainly due to the longer time required to manufacture the 3D model. The process time and cost of the material are shown in Table 4.

Table 5 shows the levels of understanding and satisfaction both before and after the explanation in group I and group II. On average, the level of understanding scores improved from 1.7±0.67 to 4.7±0.67 in group I, and from 1.5±0.53 to 2.5±0.53 in group II. The level of satisfaction scores were 4.4±0.70, and 2.9±0.57 in group I and II, respectively (Table 5). The 3D models provided a better understanding of UIAs and aneurysm clipping surgery with a high level of patient satisfaction.

This current study investigated the impact of using 3D printed aneurysm models of the patient for patient education compared with CTA. In order to reduce the bias that could arise from differences in the description rather than differences in the explanatory material, single doctor gave an explanation for the patients. The 3D model was used as an adjunct to the conventional preoperative consent process. In the current study, it was possible to quantify the impact of the 3D models on patient understanding. Compared with conventional methods, the results suggested that 3D printed intracranial vascular models comprehensively improved patients' understanding and satisfaction of UIAs and clipping surgery.

Currently, the use of 3D printing in medicine is rapidly growing in many surgical fields but mostly in surgical training and simulation [2,3,5]. The use of 3D printing technology is rapidly expanding, not only in surgical training and simulation, but also in the area of medical education for patients [4]. We successfully created patient specific 3D models to inform patients with UIA about their clinical situation, treatment options, and risk. The models were highly appreciated by the patients. Patients significantly improved their understanding of all aspects investigated with the 3D printed models compared with conventional methods. Observing a physical representation of the aneurysm did not make patients feel uncomfortable. The use of a 3D printed model herein gave patients a much better idea of what would happen during the surgery, which reassured them, and consequently, the patients felt more involved in the decision-making process.

The main limitation of 3D printing technology is that building a 3D model involves a 3D rendering and 3D printing, which are time consuming and costly [7]. However, with the development of newer printers and the broadening of printed materials, the time and cost have been reduced [13]. In this study, we used the Nobel 1.0A (XYZPrinting), which is small (280×345×590 mm) and lightweight (9.6 kg). The process time for making the 3D models is 3.7 hours on average. The material cost of each model is approximately 3500 Korea won. The time and cost will decrease as 3D printing technology advances. As 3D printing technology progresses and costs fall, patient-specific 3D printing may become standard for both clinical and educational purposes.

This study had several limitations. The model integrated only the vascular structure with the aneurysm. Other important anatomical relationships such as the other optic chiasm, cranial nerves, skulls, and brains were not included. In addition, the 3D printing technology could capture only major vasculature structures. It is not possible to capture small vessels and perforators with current commercially-available technology.

Furthermore, this study only enrolled 20 patients, and the small sample sizes may introduce bias. Given that this was only a single-center experience and that there were only 10 patient-specific models used to evaluate patient understanding, additional larger prospective studies will be needed to confirm the usefulness of a patient-specific 3D print model for patient understanding and satisfaction with aneurysm clipping surgery.

The patient-specific 3D printed aneurysm models were useful patient education. The models were accurate, realistic, and easy to understand, although they illustrated the complex intracranial vascular structure. Moreover, such models are easy to create, and we believe that they are very useful in routine clinical practice during pretreatment. However, studies with larger sample sizes are needed to confirm these preliminary findings.