Introduction

Medical education is not confined within the medical school, but it is rather a lifelong process [2, 5, 12, 24]. All kinds of theoretical and practical experience during under and post-graduate period contribute to medical education [2, 25, 37]. Three-dimensional (3D) information plays an important role in understanding the complex structure of human anatomy in medical education [22, 33–36]. Use of 3D image displays can potentially increase the learning curve of students and increase the understanding of spatial relationships as it provides a whole representation of the patient’s anatomy [18–20]. The use of 3D tools can potentially be helpful for students with lower innate spatial ability [3, 10, 22]. In recent years, new interface technologies and 3D printed models have become possible due to advanced computer technology and software [22, 27]. These printed anatomical models enable visualization and manipulation, as well as stereoscopic 3D presentation [1, 6, 21, 31].

As for the analysis of the aortic arch system, normally, it gives rise to three branches: the brachiocephalic trunk, which branches to the right subclavian and to the right common carotid arteries, the left common carotid artery and the left subclavian artery (Fig. 1) [7, 8, 14, 16, 17, 38]. Previously, the description of the six patterns of the supraaortic branches pattern and their prevalence have been gleaned from radiological and post-mortem studies (Fig. 2). Descriptions of the supraaortic arch patterns in undergraduate education were based on analyzing the structure; the clinical appliance of the essential medical knowledge is evaluated more extensively (Fig. 2a–f) [26, 39].

Fig. 1
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a–c 3D Computed tomography angiography images provide a detailed normal pattern of supraaortic arch branches originating from the left aortic arch

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Fig. 2
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a–f Schematic presentation provides a detailed vascular map of the patterns of the branches arising from aortic arch arterial tree

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The production of models was obtained by high-resolution CTA and 3D printing technologies.

The aim of this study was, first, to present the anatomical variations of the aortic arch and the supraaortic arteries and to teach the formation of one-to-one direct modeling following CTA imaging and printing. Second, it targeted stressing the radiological and surgical significance of the variations based on the obtained anatomical and radiological data. The study also aimed at an innovative teaching technique approach for the undergraduate and post-graduate medical students by applying the use of imaging and printing technologies during the course of their teaching in anatomy.

Materials and methods

The printed models of the supraaortic arch were created using 64-slice CTA data provided by the Department of Radiology, University of Ege (Fig. 3a–c). The CTA scan was performed on a 64 detector 128 sliced CT scanner (Siemens Somatom Definition AS, Siemens Medical Systems, Erlangen, Germany). The scanning was triggered by the CT technologist on the basis of contrast enhancement in the aortic arch following administration of 120 mL of iohexol with a concentration of 350 mg I/mL (Omnipaque 350; GE Healthcare, Princeton, NJ) at a rate of 4–5 mL/s. Imaging parameters include 0.6-mm section thickness, 140 kV, 250 mA, 1-s per rotation, 10–20 s to acquire images from the aortic arch to the vertex. The CTA source images were postprocessed to create contiguous coronal and sagittal reformatted images using a work station (Siemens Leonardo Workstation, Erlangen, Germany) after image reconstruction of a 2-mm section thickness, maximum intensity projection images, volume-rendered 3D images, and curved planar reformatted images of the bilateral common and internal carotid arteries. The typical dose-length product for the head and neck CTA was 2200 mGy-cm. Medical image files were in a DICOM format and were exported in image format (TIFF) files with known pixel separations. Using free software (Google SketchUp), rapid prototype bovian type of the supraaortic arch model was created. One set of models of the vascular system of the supraaortic arch were created using the volume rendering technique, based on tissue density, using CTA data (505 axial slices), and selecting density thresholds of arteries for volume segmentation (Fig. 3). The 3D CTA used for the fabrication of 3D vascular models was obtained with a slice thickness of 2 mm, to ensure high accuracy and precision. The CT data were transferred into medical image processing software (e.g., Mimics; Materialise NV, Belgium) to construct a 3D computer-aided design model. The model was saved in stereolithography file format (Fig. 4). A physical model of the processed 3D digital model was created using 3D printer Makerbot (Fig. 5). Material used was polylactic acid.

Fig. 3
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a–c Multislice 3D computed tomographic angiographic images of bovian type of aortic arch. The left common carotid artery (arrow) shares a origin site (star) with the brachiocephalic trunk. The left subclavian artery pointed by arrow head and right internal carotid artery indicated by tailed arrows

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Fig. 4
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Dimensions of X, Y, and Z for 3-D printed models

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Fig. 5
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3D printer Makerbot

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Results

Direct branches of the aortic arch are also known as the primary or the supraaortic arteries. Bovian type of the supraaortic arch pattern is the aortic arch with two branches. The first branch is the common trunk which is divided into right subclavian, right common carotid, left common carotid, and the second branch as left subclavian (Fig. 1). These structures included the aortic arch, brachiocephalic trunk, subclavian arteries, common carotid arteries, internal carotid arteries, and external carotid arteries (Fig. 6a–c). The actual model can be rotated 360° at any angle and magnified at any size for learners. Geometrical vascular anomalies can be more clearer. All reconstructed 3D printed models described here can be displayed in 3D presentation in a life-like specimen. It remains a true anatomical representation. The external shape of the aortic arch and its major branches and their dimensions are measurable. The angle formed by the aortic arch and the coronal plane was an average of 62.2° (range 30–90) and the three major branches originated from the initial third of the anterior length of the aortic arch (Fig. 6). The 3D preoperative model demonstrated the exact anatomy to understand the variable configuration in space. It also supplied us with information regarding the size of the appropriate stent graft the localization of the sealing zones.

Fig. 6
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a–c Frontal view, side view printed three-dimensional model of the nature aortic arch including bovin type can be allowed of inspection from all angles. The left common carotid artery (big arrow) originates from the brachiocephalic trunk (star), close to the left subclavian artery (head arrow), right common carotid artery, and right subclavian artery (slim arrow)

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Discussion

In the current research, the use of the CTA was explored to create 3D printed models of the supraaortic arteries for geometrical vascular anomalies teaching [1, 14, 17, 19, 21, 23, 27, 35, 36]. For example, using these combined models, students are able to trace the path of supraaortic arteries visually. The model created here is the ability to place 3D vascular anatomy into the context of individual CTA slices (Fig. 6). Using this feature, students are able to visualize the bovian type of the supraaortic aortic arch design (Fig. 6); this is a point that is often confused by students via the traditional learning.

A common arterial trunk, the truncus arteriosus, arises from the primitive heart and is divided into six paired arches. The six pairs of aortic arches are a series of vessels that connect on each side the aortic sac with the corresponding dorsal aorta. At a later developmental stage, the aortic arches are both reduced in number and extensively transformed, and finally, an asymmetric blood supply system is achieved. During the third week of pregnancy, these dorsal aortae fuse caudally into a single descending aorta at the fourth thoracic vertebral level [30, 34, 38]. The first, second, and the fifth arches then regress. The third arches form the carotid arteries. The fourth arch on the right forms the brachiocephalic and right subclavian artery, whilst on the left, this forms the left subclavian artery, and the aortic arch proper, which subsequently joins the descending aorta beyond (Fig. 7).

Fig. 7
figure 7

During the 6th to 8th week, the primitive aortic arch pattern is transformed into adult arterial mapping. The first, second, and fifth pairs of the aortic arches disappear (grey colour), while the third, fourth, and sixth pairs of aortic arches have their branches (red colour). Internal carotid artery (A), external carotid artery (B), common carotid artery (C), arch of aorta (D), brachiocephalic trunk (E), right subclavian artery (F), and right dorsal aorta (G). (Color figure online)

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The previous researchers reported that the variations of the aortic sac and the branchial artery system, from an embryologic standpoint can be explained by the disappearance of normally persisting vessels or from the persistence of channels that normally disappear; however, reasons for subtle variations are not understood (Fig. 7) [7–14, 32]. In this case report, we present a case of the left common carotid artery arising from the brachiocephalic trunk and absence of the main branches of the right subclavian artery in her angiographic imaging findings. The findings show that the cases whose brachiocephalic trunk and left common carotid artery originated together are the most prevalent type of variation, and the remaining cases of the variation showing either the left carotid artery originating from the aortic arch together with the brachiocephalic trunk, or that the left carotid artery originated directly from the brachiocephalic trunk. However, variations leading to the compression of the trachea and oesophagus may cause clinically significant symptoms. Every patient is unique and, therefore, should be embraced individually prior to surgical intervention [14, 39]. The aortic arch changes shape with advancing age or longstanding hypertension and this group has also undertaken the morphometric measurements of the arch branches, including the angles of origin and distance of origins from each branch. Using such data has led to the description of types of aortic arch as the angles between branch vessels become more acute, and the origin of the brachiocephalic trunk moves anteriorly.

Undergraduate education

The students are also reminded of the variability of human anatomy and its surgical relevance, showing the importance of personalized procedures—namely that each patient has his individual anatomy [13, 15, 28, 29]. 3D printed anatomical models can serve as accurate, tactile visualization tools, and surgical simulation devices [4, 32]. They can be utilized to reproduce complex, patient-unique anomalies, or pathologies that facilitate the surgical trainees to preoperatively predict the potential intraoperative challenges and postoperative outcomes and aid in their learning [35, 36].

Post-graduate education

Using modeling in post-graduate education helps scientists to reach a higher level of knowledge on a variety of topics, including normal structure, embryology, the underlying congenital or acquired cause of the variational structure differences, the geometrical structure of the supraaortic arch pattern, and the distance among each pattern and the angle points [32]. The course and the variation of the brachiocephalic trunk originating from the aortic arch of life-like models can be examined (Fig. 5). Since these models are exactly the same as the human, the vascular diameter, the distance between the vessels, and similar geometrical calculations can be studied easily.

Creating the 3D printing models can reduce both the operation time, exposure to general anesthetic, decrease in blood loss, and lessen wound exposure [13, 18, 21]. Tangible 3D models allow preoperative identification and help in the selection of the appropriate surgical management and improve surgical skills of the young surgeons [3, 4, 6, 9, 12]. The models have been evaluated by the patients for their usefulness in helping to understand their illness. The patients reported that the models aid in understanding the anatomy, pathology, and the surgical risks [24, 25].

Individualized treatment approaches, customizability of 3D printing, can transform the manufacturing of patient-specific catheter to being widely accessible and affordable. 3D printed custom prostheses lead to improved clinical outcomes, such as a reduction in the length of surgery, reduced exposure to anesthetics, and a decreased risk of complications like infections. Besides their value for planning, orientation, and simulation, we believe that the life-like models are helpful for demonstrating complex procedures to the patients, colleagues, and the students [7, 8, 14].

Conclusion

In conclusion, this study shows that the curricular innovation proposed, by combining medical imaging, 3D print technologies, and classical anatomical knowledge, is feasible with dedicated students. The anatomical vascular models obtained showed good qualitative and quantitative correlation with the authentic anatomy. Because of the cost and practicality issues, the aortic arch models can only be used for educational purposes. A collection of models and corresponding radiological images of interesting or complex case studies can be assembled to help trainees gain valuable learning experience.