# Design of Personalized Devices--The Tradeoff between Individual Value and Personalization Workload
## 3 Results
### Identification of Product Characteristics Potentially Relevant for Personalization  
It is essential to determine whether a differentiating property requires a customer-specific, individualized attribute, or if a predefined variant attribute will be sufficient to fulfill the purpose of the product efficiently. With this in mind, it is necessary to evaluate the impact of an individual attribute design on the overall product performance as compared to that of a variant attribute design. Product surveys and evaluation tests conducted by the product user are particularly well-suited to this task. For medical devices, medical simulation environments can be used to investigate the individualization relevance of the product properties. For this example, the _HANNES_ medical simulation model with its patient-specific aneurysm models was used (see Section 2.3). The aneurysm models corresponded to patient pathologies that had been treated using a flow diverter and showed pronounced vascular characteristics such as a particularly pronounced curvature or small optimal anchorage zones for the distal and proximal ends. Four different anatomies were tested; two of these are shown as examples in Figure 10.  
The flow diverter prototypes were implanted by experienced senior physicians who were part of the interdisciplinary team investigating the personalization of the flow diverter. Different implant prototypes were released in each aneurysm anatomy, by each physician, and the product performance was evaluated. A System Usability Scale (SUS) questionnaire, as presented by [PERSON] [49], was used for this purpose. In this questionnaire, the physicians expressed their satisfaction with the product using a variety of statements. The questionnaire has already proven effective in measuring satisfaction in a number of previous studies [50]. The implantation time was also measured and compared. Furthermore,  
Figure 10: Using additively manufactured aneurysm models developed based on angiographic 3D images with different anatomical characteristics to implant personalized flow diverter variants in order to analyze the impact of specifically designed product characteristics on overall product performance. the same implantation procedure was performed by two independent doctors. Tests at the premises of the manufacturer of the flow diverter were also added. The flow diverter prototypes differed in one attribute of a product characteristic in an attempt to influence the performance of the corresponding product property. This ensures that any change in performance must be a result of the adaption to the attribute of the product characteristic in question. The testing of the personalized prototypes shows that ensuring that the implant length exactly matched the _Vessel length_ determined by the physician has a positive effect on handling during implantation. At the same time, however, it was found that the physician could manipulate the length by pushing and pulling harder when releasing the flow diverter. If a uniform discharge--and thus a physician-specific manipulation of the length--can be prevented, personalizing the exact length of the implant will improve the product performance. Implementing the differentiation between the proximal and distal diameters alone led to an improvement in the _Wall apposition (proximal)_ and _Wall apposition (distal)_. An exact, customer-specific attribute for the diameter based on the pathology of the individual in question led to an improvement in the result of the treatment. A personalized attribute for the braid angle at an individual position in the proximal segment also demonstrated a highly positive effect on implant performance in curves and twists. An individual attribute for the _Number of wires_ and _Wire thickness_ would also be conceivable for individual behavior in curves, but since the effects of adjusting the braid angle have been researched in more detail, it makes more sense to adjust the differentiating property _Wall apposition (curvature)_ using the braid angle.