3D printing of vascular models for in vitro bench testing for hemodynamic studies: development of an automatic vessel diameter acquisition system during pulsatile flow

For medical applications, the use of 3D printing starts when this technology was first commercialized. Nowadays, the use of 3D printing for medical applications is expanding rapidly and probably will revolutionize health care in the near future. The main benefit of this technology consists in the opportunity to create customized and personalized medical products, such as implants and anatomical models, drugs and equipment. 3D printing represents a helpful instrument for the creation of patient-specific vascular anatomic models for medical device testing, for the interpretation of physiological conditions and for planning safer and more accurate interventions. In this context, the aim of this thesis work is (1) the fabrication of 3D printed phantoms representing a portion of the descending aorta, and (2) the automatic characterization of the compliance under realistic pulsatile flow conditions. These models were realized in collaboration with 3D4MED laboratory at Policlinico San Matteo of Pavia using a STRATASYS OBJET 260 CONNEX 3 printer. This printer uses photopolymer resins crosslinking with UV laser light for the fabrication of vascular models. The phantoms were realized with different percentages of two resins, a softer and a hard one. The phantoms were then tested with a mock circulatory loop (MCL) by BDC Laboratories that allows controlling the pump by setting several flow rates with a physiological waveform. A set up that allows the automatic synchronized acquisition of the external diameter and the pressure of the phantom using a LabView scheme was developed. A camera was located above the phantom with the optical axes directed orthogonally to the test bench. The camera recorded a video that was used to estimate how the external diameter varied in consequence of the prescribed flow-rate waveform. At the same time the pressure is measured upstream and downstream of the phantom. Finally, the compliance was estimated for each 3D printed phantom and compared to the physiological values characterizing human descending aortas.