Prof. Jan D'hooge
Despite the wide clinical use and benefits of current cardiac imaging techniques, medical imaging continues to develop at an incredible speed. Of course, these technological developments require advanced engineering guided by the clinical context and application. As such, these novel developments intrinsically require a multi-disciplinary approach. In this context, this Thursday morning session was introduced to offer a forum to engineers and clinicians. More specifically, two topics were addressed: high frame rate imaging and 3D fast prototyping.
Dr. Vos introduced different technical approaches towards ultrasound imaging at very high time resolution. He elegantly described how the number of ultrasound transmits to reconstruct an image can dramatically be reduced by transmitting multiple image lines simultaneously or by transmitting defocused ultrasound beams and how this results in a spectacular increase in frame rate (i.e. time resolution). These conceptual imaging paradigms were demonstrated to work in practice both in open-chest experimental animal setups and in the clinical setting. The generated datasets were shown to have a rich information content enabling to analyze myocardial motion patterns in detail and opening up the door towards novel clinical applications. His clinical colleague Dr. Strachinaru built on this lecture in order to explore the value of this novel technology in clinical routine. In particular, shear waves induced in the LV myocardium due to (aortic/mitral) valve closure were investigated as they might give insight into the native myocardial elastic properties. As a proof of concept, it was shown that shear wave speed in HCM patients is significantly higher than that in normal controls suggesting that their native tissue properties differ. Other waves at different phases of the cardiac cycle were described and suggested to be of possible use in phenotyping the individual heart. Although the nature and origin of some of the observed waves remains incompletely understood and although the true clinical added value of this high frame rate imaging technology yet remains to be demonstrated, better characterization of HFpEF patients; better timing of surgical interventions in valve disease; and discovering subclinical HCM seem possible targets to name a few.
Dr. Valverde-Perez shifted gears by moving to 3D printing technology. Although different volumetric imaging modalities exist (i.e. US, CT, MRI) each having pro’s and con’s, he pointed to the fact that data acquisition is critical for high-quality prints and thus recommended to work with the modality in which the user/hospital has the most expertise. Combining these images with (commercially) available segmentation tools were shown to enable reconstructing structures – in his hands – reliably with 3D printing accuracy of ~1mm (using the original image data as reference). Several clinical cases were presented and discussed that clearly demonstrated the added value of this printing technology. In particular, the models showed to be of use for complex surgery planning in congenital heart disease but also to plan minimally invasive interventions such as endovascular stenting, left/right heart valve implantations, and ASD/LAA closure. Dr. Pappalardo subsequently took this technology a step further by using it to better understand the detailed morphology of the valves. He convincingly demonstrated that also in the context of valve disease 3D rapid prototyping adds value. A key question to be addressed remains however how the material properties of the printed models can be matched to the tissue properties of an individual patient. Hopefully, novel imaging technologies can help out here thereby nicely creating a link between the first two lectures on high frame rate echocardiography and the latter talks on rapid prototyping.
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